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Revision anterior cruciate ligamentreconstruction
REVISION ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION MERRICK J. WETZLER, MD, ARTHUR R. BARTOLOZZI, MD, MARTIN J. GILLESPIE, MD, DAVID L. RUBENSTEIN, MD, MICHAEL G. CICCOTTI, MD, and LAWRENCE S. MILLER, MD
Anterior cruciate ligament (ACL) reconstruction has gained wide acceptance as the treatment of choice for the functionally unstable ACL-deficient knee and is now performed on about a half million individuals per year. The documented long-term good or excellent result rates for functional stability, relief of symptoms, and return to activity for intra-articular ACL reconstructions is approximately 75% to 95%. This leaves a substantial group of patients with an unsatisfactory result secondary to a variety of reasons. Review of the literature reveals that recurrent instability and graft failure are responsible for unsatisfactory results in as high as 8% of these patients. In this article, the factors responsible for graft failure and recurrent instability are discussed. In addition, the planning and difficulties hhat the orthopedic surgeon must address before, during, and after the procedure, are also reviewed. KEY WORDS: arterior cruciate ligament, failure, revision, reconstruction
Anterior cruciate ligament (ACL) reconstruction has gained wide acceptance as the treatment of choice for the functionally unstable ACL-deficient knee. It is n o w performed on approximately a half million individuals per year. ~ The d o c u m e n t e d long-term good or excellent results of p r i m a r y ACL reconstructions with respect to functional stability, relief of symptoms, and return to activity is between 75% to 950/o.2-9 This leaves a substantial group of patients with an unsatisfactory result, secondary to a variety of reasons, which include (1) continued pain secondary to preexisting degenerative articular cartilage changes within any compartment of the knee, 2,10-12(2) loss of motion associated with operative intervention (arthrofibrosis and infrapatellar contraction syndrome), 13,14and (3) recurrent instability. 2,~°,12,15-1s Review of the literature reveals that recurrent instability and graft failure are responsible for unsatisfactory results in as high as 8% of patients w h o undergo primary ACL reconstructions.2,1°,l~,13 Ideally, revision ACL reconstruction restores function in patients w i t h recurrent instability after a p r i m a r y ACL reconstruction. Harner and Fu classified failed ACL reconstruction w i t h recurrent instability into three groups based on the prim a r y cause for failure2,1°q2: • Technical errors. Included in this category are all surgical errors as well as failure to recognize or properly address laxity in the secondary restraints. e Biological failure. Failure of graft incorporation, biomechanical failure of the tissue (failure of "ligamentization'), infection, or rejection. From the Department of Orthopaedic Surgery, South Jersey Orthopaedic Association; the Department of Orthopaedic Surgery, Thomas Jefferson University Medical Center; Department of Orthopaedic Surgery, Thomas Jefferson University Medical Center, Rothman Institute; and Pennsylvania Hospital, Philadelphia,PA. ~ddress reprint requests to Arthur R. Bartolozzi, MD, 800 Spruce St, Philadelphia, PA 19107. Copyright © 1996 by W.B. Saunders Company 1048-6666/96/0603-0009505.00/0
• Traumatic failure. Subsequent trauma deemed sufficient to rupture an intact and functional graft (Fig 1). Schepsis 1,19 and DiStefano 2° classified failure to recognize or address associated laxity as a fourth category separate from technical errors. [t is our opinion that this error is purely dependent on the physical examination and technical skills of the operative surgeon and thus is better classified as a technical error. To facilitate revision ACL reconstruction, it is vitally important to identify the cause of failure prior to surgery. Many factors are associated with graft failure a n d recurrent instability. These factors are not mutually exclusive, and several different causes can contribute concurrently to failure of a p r i m a r y ACL reconstruction, z1°-12,1~,2°Harner 1° and Distefano 2° documented, respectively, that 60% and 40% of their failed ACL reconstructions h a d primary as well as secondary factors contributing to the failure (Fig 2). Technical Errors
Schepsis reported that 92% of the ACL reconstructions that were revised failed primarily because of a technical errod (Fig 1). H a r n e d ° and DiStefano 2° further a d d e d that technical errors, although not always the primary cause of failure, contributed to failure in 83% and 95% of their cases, respectively (Fig 2). Technical errors include (1) nonanatomic tunnel placement (most c o m m o n technical error), (2) inadequate notchplasty, (3) improper tensioning of the graft, (4) inadequate or improper fixation of the graft in the b o n y tunnels, (5) failure to recognize or properly address laxity in secondary constraints, (6) poor graft selection, and (7) improper or inadequate graft harvest or preparation. Nonanatomic Tunnel Placement
The literature reports that 70% to 80% of the technical failures were due to improper tunnel placement 2.1°-I2,19-21 (Fig 3). The majority of these failures were related to an improperly placed femoral tunnel. 2,1°-12,I9-2I This is clearly
Operative Techniques in Orthopaedics, Vol 6, No 3 (July), 1996: pp 181-189
"181
[mSchepsis [] DiStefano • Harner [] Uribe ]
In Schepsis [] DiStffano • Harner [] Uribe]
I00~ 81% 82%
75% S0~ 25% 17% f ~
15% 14%
25%
4% 5% 5% Nonanat omic Tunnel
0%
Technical Errors
Traumatic
Biological
Causes
Causes
Fig 1. Factors responsible for failure of ACL reconstruction can be divided into three major categories: (1) technical errors, (2) biological derivations, and (3) traumatic causes. In the four major series by DiStefano, 19 Harner, ~° Schepsis, 20 and Uribe, 21 technical errors were responsible for approximately 60% to 90% of failures.
because of the significant impact that femoral tunnel location has on the isometric behavior of the graft during range-of-motion of the knee. 2° An ACL graft can only withstand a small amount of strain prior to plastically deforming. Excessive tension and strain will cause inA 100% 83% 75%.
50%.
25%
18%
i [ [
o%.,~
Technical Errors
Traumatic
Biological
Causes
Causes
E" 100%
Fixation
Notch Impingement
Associated Laxity
Inadequate Graft
Fig 3. Technical errors can be subdivided into five main categories: (1) nonanatomic tunnel placement, (2) inadequate or improper fixation, (3) inadequate notchplasty, (4) unrecognized or unaddressed associated laxity, and (5) inadequate graft harvest or selection. Nonanatomic tunnel placement was primarily responsible for as much as 70% to 80% of failures, with a majority of these errors related to femoral tunnel placement. The remainder of failures were the results of the other reasons listed.
creased laxity of the graft and failure of the reconstruction. Placing the femoral tunnel too far anterior on the lateral femoral condyle and fixing it at 0 ° to 30 ° of extension will therefore produce excessive graft strain when the knee is flexed. Placing the graft in a posterior (over-the-top) position will result in excessive laxity of the graft in flexion and increased tension in extension (Fig 4). Although not as crucial as the femoral tunnel, it is still important to properly place the tibial tunnel. A tunnel drilled too far anterior on the tibia will cause excessive tension on the graft in both flexion and extension. In addition, Howell m22 has documented that an anterior tibial tunnel will cause the graft to impinge on the roof of the femoral notch. A tunnel placed too far posterior on the tibia results in excessive laxity of the graft in flexion. In addition, if the tunnel is placed too far medially or laterally on the tibia, the graft will impinge on the walls a n d / o r roof of the notch. Howell stresses the value of magnetic resonance imaging (MRI) and lateral radiographs of the knee in extension to evaluate the status of the graft and tunnel placement 2s (Fig 5).
75%
Inadequate Notchplasty 50%
25%
0%
Technical Errors
Traumatic
Biological
Causes
Causes
Fig 2. Factors responsible for failure of an ACL reconstruction are not mutually exclusive. More than one factor can contribute to failure. (A) Harner 1° and (B) DiStefano is both documented that 60% and 40%, respectively, of their failed revision ACL reconstructions had primary as well as secondary factors contributing to the failure of the initial reconstruction.
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Graft sources are usually larger than the original ACL. Inadequate notchplasty causes impingement of the graft on the roof, as well as the wall of the notch. If an adequate amount of bone is not removed from the anterior/superior portion of the notch, the graft will impinge in extension, and flexion contracture may result. 24 Schepsis, ]9 Distefano, 2° and Harned ° all reported that approximately 5% of their revision cases had impingement with subsequent lack of extension and failure of the reconstruction. A graft usually fails secondary to repetitive trauma and attrition from friction against the notch as the knee goes into extension. 13,17,22,23 In addition, as the knee cycles from flexion to terminal extension, this repetitive stress may fatigue the fixation device. This may result in fi afion failure prior to graft incorporation. Furthermore, insufficient removal of WETZLER ET AL
decreased anterior translation but will also increase tibiofemoral contact forces, which may accelerate degenerative changes. Overtensioning can also cause elongation of the graft, postoperative loss of motion, or possible fixation failure. 15 Furthermore, Yoshiya has proposed that overtensioning may decrease incorporation, delay vascularization, and cause mvxoid degeneration of the graft. 2s
Failure to R e c o g n i z e or Address Associated Instability
Failure to recognize or address associated pathological laxities may result in a sensation of continued instability or lead to actual giving way and result in damage to the reconstructed ACL. Schepsis 1,19 reported that failure to recognize or address associated instability patterns (posteriolateral rotatory instability [PLRI], anteriomedial rotatory instability [AMRI]) contributed to 15% of the failed ACL reconstructions they revised. DiStefano 2° reported that associated laxity was primarily responsible for 25% of the cases he revised (Fig 3). In all primary and revision ACL reconstructions, the patient must be assessed for any associated secondary laxity patterns, both preoperatively and intraoperatively. Graft Fixation
In recent years, results have improved from accelerated rehabilitation programs as popularized by Shelbourne. 7'29 Thus, more importance and increased stress is placed on Fig 4. (A) An improperly placed femoral tunnel can cause excessive length changes in the graft, with the graft becoming nonfunctional. (B) Revision notchplasty is required to visualize the previous tunnels, as is the over-the-top position to guide in new tunnel placement. The markings on the probe are 5 mm in width. Notice how the original tunnel is at least 10 mm anterior from the posterior wall of the femoral notch. In this situation, a new tunnel can usually be drilled with minimal interference from the previous tunnel.
the lateral wall of the notch, especially inferiorly (distally), will also produce attrition and subsequent graft failure. 2° Injury to the graft from impingement has been confirmed with MRI results. Grafts that do not impinge will have a signal similar to that of a tendon. Impingement results in changes in the midsubstance of the graft, which will be represented by an increased signal or narrowing o f its substance on MR117,22,23(Fig 5). Improper Tensioning
Although the exact amount of tension has not been determined, it is vital that the graft be placed and fixed under adequate tension. Many investigators initially attach the femoral side, and then tension and fix the tibial side, between full extension and 30 ° of flexion. 9,15,24-27The graft is then checked for proper tension through a full range of motion. Undertensioning of the graft during fixation will result in immediate residual postoperative laxity. Overtensioning has been associated with poor graft incorporation, decreased graft strength, and increased constraint of the knee. 28 Increased constraint of the knee will produce REVISION ACL RECONSTRUCTION
Fig 5. Howell 22 stresses the value of MRI and lateral radiographs of the knee in extension to evaluate the status of the graft and tunnel placement. A tunnel placed too far anteriorly on the tibia will cause impingement on the notch. Injury to the graft from impingement has been confirmed with MRI studies. Grafts that do not impinge will have the normal signal of a tendon. Impingement will result in changes in the midsubstance of the graft, which will be represented by an increased signal or tapering of the graft on MRI, as shown here.
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the fixation of the graft. Schepsis 19 and Harner 1° reported that inadequate fixation, respectively, contributed to 8% and 14% of their failed primary reconstructions. DiStefano described three cases (15%) in which the fixation was improperly placed and abraded the graft, causing the graft to fail.2° The strength of fixation techniques has been extensively studied. 3°,31 Regardless of technique, the fixation must be properly placed and hold during the early postoperative period to prevent changes in tension during rehabilitation.30,32,33
Graft Selection and Harvest
Harner has reported a case of an inadequately harvested graft that contributed to its eventual failure. 1° Uribe, in addition, discussed three cases that had progressive or persistent laxity following the original reconstruction with an incompetent graft. 21 These grafts were unable to withstand the physiological stresses during normal activity and subsequently failed. Several different types of grafts are currently used: • Autograft Bone-patella tendon-bone central one third Hamstring Quadriceps--Patella Iliotibial band • Allograft Bone-Patella Tendon-Bone Achilles tendon Iliotibial band • Synthetic and LAD have fallen out of favor. Biological F a i l u r e
Any graft used for reconstruction of the ACL is biologically different than the original ACL. The most obvious difference is collagen type and fibril size, length, and orientation. The inability of the reconstructed ACL to exactly duplicate the natural ACL in certain cases contributes to graft failure (Table 1). The reconstructed ACL may not revascularize or biologically adapt ("ligamentize'). Additionally, biological failure of the graft can occur because of failure of the graft incorporation, 2,1°bone plug healing, 34 infection,35 or rejection of the graft (if an allograft is used).35 Harner reported that 14% of failures were directly the result of failure of graft incorporation (80% were allografts). 1° Although not the primary cause of failure, failure of graft incorporation contributed to another 25% of Harner's reported failures. 2,m Berg also noted that nonunion of the bone plugs can be a contributing factor to failure of an ACL reconstruction. 34 If an allograft is used, an immunological reaction, ie, rejection, must be c o n s i d e r e d . 1,2,11,12,19,20,36,37Thompson and Harner reported that approximately 60% of patients who underwent allograft reconstruction of their ACL will mount some type of immunological reaction, which may hinder graft incorporation. 1°,35,37In contrast to allografts, Schepsis reported an 8% biological failure rate using only autografts. 2° 184
TABLE 1. Biological Differences Between a Tendon Graft and Normal ACL Anterior Cruciate Ligament
Tendon Graft
Ligament fibers of different length. During ROM, fibers see different tension and loads Fibers are not parallel Bimodal fibril diameter (type I collagen)
Fiber is uniform length Tensioning is a composite of all the fibers and is randomly distributed Fibers are parallel At the time of reconstruction the fibril pattern is different then the pattern after incorporation The replacement fibroblasts are not capable of re-establishing the inherent characteristics of the normal ACL Aneural except for those receptors accompanying revascularization
Complex relationship of ACL fibroblasts surrounded by and interacting with biopolymers synthesized by these cells Mechanoreceptors as well as pain fibers provide proprioception and neurosensory function Distinct vascular supply
Variable vascular supply
Abbreviations: ROM, range of motion; ACL, anterior cruciate ligament. Adapted and reprinted with permission. 21
Other Causes
of F a i l u r e
Laurencin and Warren reported on seven cases of infection in approximately 2,200 ACL reconstructions (0.3% infection rate). This is similar to the infection rate for total joint arthroplasties. Infections require prompt and thorough irrigation and debridement. Whether to remove the graft and fixation should be decided on an individual basis and depends on the causative organism, magnitude of the infection, and the specific graft and hardware usedY Lastly, Paulos discussed the etiology and treatment of arthrofibrosis and infrapatellar contracture syndrome with significant fibrosis and scarring, with resultant and severe decrease in range of motion. To restore motion and function, manipulation of the knee a n d / o r debridement of scar tissue as well as the graft may be required; early intervention is essential. If the patient is severely limited at 6 weeks, intervention consisting of manipulation, arthroscopy, and debridement is advised. Patients should be counseled that manipulation can cause graft rupture and that graft removal in some cases may be necessary to regain motion leaving the knee once again unstable. 14 Traumatic
Causes
Fu believes that in an athletic population 5% to 10% of ACLs reconstructed will fail secondary to repeat trauma even if a technically perfect ACL reconstruction was performed. 1,2,11a9 Harner 1° and Uribe, 21 respectively, reported that a traumatic episode was responsible for failures in 25% and 43% of their patients undergoing revision ACL reconstruction. Schepsis believes that the incidence of true traumatic reruptures is lower and that pure reruptures rarely occur. Most traumatic reruptures have contributing factors, and these figures do not account for these factors. 1,19Traumatic re-ruptures can be subdivided into two categoriesa,n,12: (1) Failures secondary to early trauma before complete graft incorporation and the completion of rehabilitation; and (2) late trauma after resuming full activities. Graf has implicated overzealous rehabilitation or too WETZLER ET AL
early return to activity in graft failure. 13With the implementation of aggressive rehabilitation protocols, physicians have to temper the aggressive rehabilitation against the risk of failure of the ACL graft. It is essential to have secure fixation of the graft prior to embarking on an aggressive rehabilitation program. Tendon-to-bone healing can take up to 8 to 12 weeks, whereas bone-to-bone healing is somewhat faster. Stability of graft fixation must be factored in selecting a rehabilitation program. In late failure secondary to significant trauma associated with a large hemarthrosis, it is assumed that the patient had returned to full activity, the knee was stable, the graft had been incorporated and was functioning at the time of injury. Rubenstein and Shelbourne believe that most early failures are traumatic prior to graft incorporation, whereas late failures have multiple contributing factors as described earlier. 29It is unclear how accurate this assumption is and what other factors may play a rote in graft failure. In recent literature, there have been several reports discussing the effects of the sterilization process on disease transmission and resultant graft strength. 39,40 Allografts that are irradiated, can be weakened by the process. 4° The general recommendation is to use less than 2.5 Mrad radiation, but many surgeons prefer fresh frozen nonirradiated grafts because of the improved mechanical properties .39
OPERATIVE AND TECHNICAL CONSIDERATIONS Preoperative Planning Harner has shown that revision ACL reconstruction can restore function. 2,1°-12 The patient should have realistic goals about their return to sports versus their ability to do their activities of daily living without instability. The orthopaedic surgeon should be aware of patients that will "trash their knees" no matter how much they are instructed against it. These "knee abusers" will test any reconstruction or revision. An understanding of all surgical options and approaches is essential when a surgeon considers revision ACL surgery. Familiarity with different techniques of tunnel placement (one v two incisions), graft harvesting and preparation techniques, as well as various methods of graft fixation, is essential. This will allow the surgeon flexibility to anticipate and adapt to the unique situation when he or she is performing a revision ACL reconstruction. The preoperative workup should include MRI to assess joint surface conditions, meniscal disease, and tunnel size, positions, and possible tunnel enlargement erosion. A lateral knee radiograph in full extension is also useful in assessing tunnel placement13,23,24 (Fig 5). Standing anteriorposterior radiographs are helpful to assess alignment of the lower extremity. In long-standing ACL deficiency, double or triple varus knees, as described by Noyes, may develop and should be addressed during revision ACL reconstruction. 4~ A thorough preoperative evaluation of laxity is imperative. The examination should begin with careful observation of gait, Detection of a subtle undiagnosed laxity REVISION ACL RECONSTRUCTION
pattern is required to ensure proper repair a n d / o r reconstruction and, therefore, preventive failure of the revision ACL reconstruction.l,13,2°,43
One-Staged Versus Two-Staged Procedures If the previous surgery has resulted in tunnel enlargement ~ that left large bony tunnels that will interfere with placement of new tunnels, consideration must be given to bone grafting the tunnels and staging the final reconstruction. The patient must be advised of this possibility preoperatively. In addition, if the patient has a significant loss of motion, (extension > 5 °, flexion > 20°), this must be rega!ned before the definitive reconstruction, and the procedure might need to be staged. 2,1°-12
Incision Placement Old incisions should be used whenever possible to perform the procedure and to remove any residual hardware; avoid skin bridges of less than 7 cm. If there are multiple incisions, consider using an allograft to minimize the incisions. Careful surgical technique with delicate handling of the soft tissue, as well as opening and closing the periosteum with care, is needed to prevent soft tissue and wound complications. 2,12
Hardware Removal Depending on the graft used in the initial ACL reconstruction, the surgeon may need to have an assortment of fixation devices, such as interference screws, staples, cortical and cancellous screws, and washers. A variety of screw drivers are needed to remove the different interference screws. It may be difficult to find the interference screw or other fixation devices. At times, a pneumatic burr or hollow mill may be required to remove bone that has overgrown and covered the fixation devices. The appropriate screw driver that fully seats into the head of the screw is a necessity. A stripped screw can lead to extensive bone removal that may require bone grafting and compromise fixation of the revision graft. The surgeon should contemplate whether a staged revision might be more appropriate, and sometimes this determination can only be made at the time of surgery. A femoral screw in a two-incision technique may need to be removed, but with endoscopic technique it may be left in place because the trajectory of the tunnels are different.2,11,12 If staples are used as the femoral fixation, a prong may interfere with tunnel placement and require removal. This is never an easy procedure.
Prosthetic Ligament Removal An en-bloc removal of the prosthetic ligament is preferred because particulate debris from synthetic ligaments has incited an inflammatory response. A synovectomy may be necessary if the synthetic ligament is frayed and has already disintegrated into the joint. 43In addition, synthetic ligaments may cause enlargement of the bone tunnels, and it might be wise to graft the tunnels initially and stage the revision reconstruction once the bone tunnels are healed. ~3,2°,43Removing a well-ingrown synthetic ligament may require overdrilling the graft with a hollow mill. 185
Graft Selection
Graft choices include allograft and autograft materials. Allografts include patella and Achilles tendon, whereas autografts can include patellar tendon, either from the ipsilateral or contralateral knee, quadriceps tendon, iliotibial band, or the hamstring tendon (semitendinosus/ gracillis). Schepsis recently reported similar results using allografts and autografts. 19 Purnell reported good results using a partial-thickness quadriceps tendon with a bone plug from the proximal patella. 44 Some orthopaedic surgeons favor the use of hamstring tendons because they allow more flexibility of tunnel size and placement; fixation can be accomplished with an Endobutton (Acufex Inc, Norwood, MA). The Endobutton is like a molly bolt or grappling hook and relies on an intact femoral cortex, rather than intact femoral tunnel, and an interference fit with a screw. Furthermore, the Endobutton requires no additional incisions as would be necessary when screws or staples are used. Fixation of the hamstring may be accomplished with a screw through the femur and thus does not rely on an intact femoral cortex of the tunnel. Fixation is enhanced with the use of a bone graft in certain instances. Additional pros and cons of selecting a graft for a revision are summarized in Table 2. 2"10-12'20'21'29'45 Recently, some orthopaedic surgeons have contemplated reharvesting the middle third of the patella tendon as a graft source. This is more popular in Europe. 18,43Sequential MRIs of the harvest site have documented reconstitution of the patella tendon at 1 year. 2,1°-12,2°,29Biopsy specimens of the reharvested tendon have shown normal tendon architecture. Karns et al is recently reported a case of a revision ACL reconstruction using a reharvested patella tendon 4 years after the original reconstruction. Goble is concerned with the mechanical properties and tensile strength of this reharvested tendon. 46As of yet, there are no biomechanical studies documenting the mechanical properties and tensile strength of the reharvested bone-patella tendon-bone graft as compared with a virgin-harvested graft. It is difficult to recommend this graft selection at this time, because there TABLE 2. Pros and Cons of Different Graft Sources Used for Revision ACL Surgery Pros Autograft
Patient's own tissue; there is no chance of rejection or "delayed incorporation" No extra cost Available and AIIograft strong No donor site morbidity Shorter tourniquet Smaller incision Flexibility with size and width of bone plugs Synthetic Available Minimal morbidity
Cons
Status
Graft site morbidity (PF pain or hamstring weakness) Limited availability
Used for hamstrings or failed allografts with technical errors that do not compromise tunnel placement Used for failed autografts Used for failed allografts with obvious technical errors or failure from traumatic reinjury Not currently indicated
"Delayed Incorporation" immune reaction HIV and disease transmission Irradiated (effects on mechanical properties) Expensive Stiffer than ACL, which leads to
failure Inflammatory reaction Adapted and reprinted with permission. 1° 186
Fig 6. In patients with long-term deficiency of the ACL, the notch narrows over time, filling up with soft tissue and bony overgrowth. A bone-patella-bone (allograft or autograft), hamstring tendons, or other graft sources are usually larger than the original ACL. An adequate notchplasty is necessary so that the over-the-top position can be properly visualized and proper tunnel placement can be assured.
are more reliable grafts with documented good results (both autografts and allografts). Revision Notchplasty
Some natural overgrowth of the notch will occur after an ACL reconstruction. Ideally, the graft should not impinge at all. Revision notchplasty is required to visualize the previous tunnels, as well as the "over-the-top" position to guide in new tunnel placement (Fig 6). In addition, revision notchplasty will prevent impingement from the lateral femoral condyle or superior notch. 2,12,1s Bone Tunnels
Selecting and creating the proper bone tunnels during a revision of an ACL reconstruction can be the most challenging portion of the procedure. The treatment of different technical errors or problems with tunnel placement are summarized in Tables 3 and 4.1° In the initial assessment of any patient prior to revision ACL reconstruction, the surgeon must determine if the procedure should be performed in stages. If the tibial or femoral tunnels are drilled too far anteriorly, often the tunnels may be redrilled in the optimal position with little interference from the previous improperly placed tunnels (Fig 7). On the femoral side, correct tunnel placement can be facilitated by using a two-incision approach when an endoscopic procedure was done originally, and visa versa (Fig 8). By using a different technique (two-incision endoscopic) the new tunnel will quickly diverge from the old tunnel and allow adequate fixation with an interference screw (Fig 9). If the tibial tunnel is only slightly anterior and the optimal placement would encroach on the previous tunnel, several techniques may be used to solve this error. The surgeon can expand the tunnel posteriorly and fashion a larger bone plug from an allograft. If an autograft is preferred, a core of bone obtained from drilling WETZLER ET AL
TABLE 3. Suggestions on How to Best Resolve the Problems of Improperly Placed Tibial Tunnel Placement Location
Options
Too far anterior or posterior
Redrill the tunnel in the optimal position.
Slightly anterior
Expand the tunnel posteriorly and use a larger ACL bone plug (allograft) Expand the tunnel posteriorly and place the ACL graft posteriorly and bone graft anteriorly (allograft or autograft).
Slightly posterior
Expand the tunnel anteriorly and use a larger ACL bone plug (allograft) Expand the tunnel anteriorly and place the ACL graft anteriorly and bone graft posteriorly (allograft or autograft)
Large capacious tunnel (usually occurs when an Achilles tendon allograft or synthetic graft are used)
Use a larger bone plug (allograft) Simultaneous use of bone graft and ACL graft in appropriate position Stage the procedure: 1st stage: Bone graft the tunnel 2nd stage: ACL reconstruction after incorporation of bone graft
Adapted and reprinted with permission. 21
the new tunnel or a graft core obtained from the tibial may be used to graft the tunnel. Interference fixation may be difficult, so the surgeon may need an alternate type of fixation other than an interference screw (ie, screw and washer, staple, or the Endobutton). In addition, sometimes a second interference screw can be used as a spacer. A femoral tunnel placed slightly anteriorly can be treated in several wavs. The surgeon may choose to convert to the over-the-top position or the two-incision approach. Rosenberg has described another method for coping with this technical error that uses a quadruple hamstring graft. He divides the graft into two halves, and through two 6-ram femoral tunnels, he attaches each graft to the femur with a separate Endobutton. 47 This allows tunnel placement m an optimal position without interference from the previous malpositioned tunnels. If a twoincision approach is used, the graft may be fixed directly to the femur through the lateral incision with a screw, staple, or Interference screw. If the tibial tunnel is too far posteriorly In the tibia, the surgeon can expand the tunnel anteriorly and either use a larger bone plug or graft posteriorly in just the opposite
Fig 7, The tibial tunnel is viewed with the scope. The initial placement of the tibial interference screw allowed redriliing of the tibial tunnel in optimal position with little interference from the previous screw,
fashion to that described for a tunnel placed too far anteriorly. In the femur, if the tunnel is too far posteriorly, the posterior wall is usually blown out, and this usually requires the surgeon to convert to the over-the-top or two-incision technique to gain adequate femoral fixation. One of the most difficult problems associated with a failed synthetic graft or allograft is a large capacious tunnel. 42,43 This usually occurs with svnthetic allografts. The resultant defect after the graft is removed may be difficult to treat. Adequate assessment with computed tomography scan in the plane of the tunnel or MRI scan may be helpful. The surgeon can use one of three techniques: (1) use a larger bone plug from a allograft, (2) simultaneously bone graft the tunnel and place the ACL and bone plug in the optimal position with a bone plug core obtained with a coring reamer; or (3) bone graft the tunnel and stage the procedure. Usually the surgeon must stage the procedure, the tunnel should be bone grafted, preferably with autograft to accelerate incorporation. Once the graft has healed, a surgeon may proceed with the revision ACL reconstruction, drilling the tunnels in the optimal position.
TABLE 4. Suggestions on How to Best Resolve the Problems of Improperly Placed Femoral Tunnel Placement Location
Options
Too far anterior
Redrill the tunnel in the proper position ignoring the old tunnel Expand the tunnel posteriorly and use a larger ACL graft bone plug (allograft) or convert to "overthe-top" two-incision technique Same as tibial technique or use an alternative fixation device such as the Endobutton Convert to "over-the-top" two-incision technique or use alternative fixation device such as the Endobutton Use endoscopic technique to create a divergent tunnel
Slightly anterior Large, capacious tunnel Blowout posteriorly Two-incision tunnel (outside-in)
Adapted and reprinted with permission 21 REVISION ACL RECONSTRUCTION
Fig 8. The initial femoral tunnel was drilled too far anteriorly. The new femoral tunnel was easily drilled in the optimal position without interference from the old tunnel.
187
Fig 9, A two-incision approach was performed for the original ACL reconstruction, Endoscopic technique was used for the revision surgery, and the new femoral interference screw quickly diverged from the original interference screw, Graft Fixation
As with placement of the bone tunnels it is advantageous to know different types of graft fixation. Usually, fixation is performed with interference screws. Additional fixation methods include several new techniques to fix hamstrings such as the bone mulch technique (Arthrotek, Ontario, CA) and interference screw fixation techniques for the hamstring developed by Smith & Nephew DonJoy (Carlsbad, CA) as well as Arthrex. Addressing Associated Laxity
As stated previously, the surgeon must address and correct all associated laxity at the time of the ACL reconstruction revision. Residual PLRI must be corrected or the revision reconstruction may fail. The posterior lateral corner (PLC) structures include: popilteus, lateral collateral ligament (LCL), arcurate ligament, a n d / o r the popilteofibular ligament. Unlike the posterior medial corner, these are discrete structures and like the ACL, will not heal properly if incompetent. Often, the PLC structures are intact and are lax either from partial tearing during the original injury or from secondary elongation from chronic ACL deficiency and recurrent giving away. In this scenario, excessive laxity 188
of the PLC structures may be corrected by recessing the femoral attachments of the popilteus and LCL. This tightens the PLCs without changing their axis of rotation. If the popilteus, LCL, accurate ligament, a n d / o r the popilteofibular ligament are disrupted, reconstruction of these structures with an allograft or autograft is essential to restore stability. The Achilles tendon allograft is well suited for this reconstruction. An Achilles tendon allograft can be split with both ends remaining attached to one bone plug. 48,49 The bone plug is placed in the insertion of the LCL/popilteus tendon, and the two bundles of the Achilles tendon are used to reconstruct the torn structures of posterolateral corner. The choice of autograft for this procedure depends on what structures remain from the previous ACL reconstructions. A patient with long-term PLRI and ACL might develop double or triple-varus alignment of the lower extremity, as described by Noyes. 41A valgus osteotomy, in addition to a reconstruction of the posterolateral comer of the tibia is required. The valgus osteotomy accomplishes two things: (1) correction of the varus alignment, and (2) prevention of excessive tension on the reconstructed posterolateral corner. Reconstruction of AMRI (posterior medial corner) is less complex than reconstructing the posterolateral corner. The posterior medial corner is made up of the deep medial collateral ligament (MCL), which becomes confluent with the superficial MCL to form the posterior oblique ligament (POL). These structures do not need to be reconstructed separately as on the lateral side, because they are not discrete bands of tissue but sheets of tissue in layers. The POL and deep MCL are more substantial and confluent compared with the structures of the posterolateral comer. Therefore, if these structures are lax, they may be reefed rather than reconstructed. An oblique incision is made in the POL, and sutures are placed in the POL. After the ACL is reconstructed and the graft fixed, the POL is advanced, and the sutures are tied in a "pants-over-vest" fashion.
Postoperative C a r e
and Rehabilitation
Patients should be advised that ACL revision is a salvage procedure with often unpredictable results. Rehabilitation after revision ACL reconstruction is not the same as after a primary reconstruction; special consideration in rehabilitation of these patient must be taken into account. Many of these patients have had reconstruction of their secondary constraints or have persistent laxity because of prolonged ligament laxity. The rehabilitation protocol must be tailored to the individual and security of fixation of the graft must be taken into consideration. The general rule in designing a rehabilitation protocol is to respect graft healing. Activity is limited, with protective weight bearing on crutches for 2 to 8 weeks, patients are advised that a return to sporting activities takes at least 1 year.
REFERENCES 1. Personal communication with Schepsis AA, June 1994 2. Greis PE, Johnson DJ, Fu FH: Revison anterior cruciate ligament surgery: Cause of graft failure and technical considerations of revision surgery. Clin Sports Med 12:839-852, 1993
WETZLER ET AL
3. Harter RA, Ostering LR, Singer KM, et al: Long-term evaluation of knee stability and function following surgical reconstruction for anterior cruciate insufficiency. Am J Sports Med 16:434443,1988 4. Holmes PF, James SL, Larson RL, et al: Retrospective direct comparison of three intra-articular anterior cruciate ligament reconstruction. Am J Sports Med 19:596-600, 1991 5. Howe JG, Johnson RJ, Kaplan MJ, et al: Anterior cruciate ligament reconstruction using quadriceps patella tendon graft: I. Long term follow-up. Am J Sports Med 19:447-57,1991 6. Korblatt I, Warren RF, Wickiewicz TL: Long-term follow-up of anterior cruciate ligament reconstruction using quadriceps tendon substitute for chronic anterior cruciate ligament insufficiency. Am J Sports Med 16:444-448, 1988 7. Shelbourne DK, Whitaker JM, McCarroll JR, et al: Anterior cruciate ligament reconstruction of acute tears without repair. Am J. Sports Med 18:484-489,1990 8. Shimo K, Inque M, Horibe S, et al: Reconstruction of the anterior cruciate ligament using allogenic tendon: Long term follow-up. Am J Sports Med 18:457-465,1990 9. Sisk TD: Knee injuries, in Crenshaw AH (ed): Campbell's Operative Orthopaedics. vol 3. Eighth edition. St Louis, MO, Mosby-Year Books, 1992, pp 1487-1732 10. Harner CD: Revision anterior cruciate ligament reconstruction using fresh-frozen allograft tissue. Instructional Course at the 62nd Annual American Academy of Orthopaedic Surgeon Meeting, Orlando, FL, February, I995 11. Johnson DL, Harner CD, Maday MG: Revision ACL surgery, in Fu FH, Harner CD, Vinve KG (eds): Knee Surgery, Baltimore, MD, Williams & Wilkins, 1994, pp 877-895 12. Maday MG, Harner CD, Fu FH: Revision ACL surgery: evaluation and treatment, in Feagin JA (ed): The Crucial Ligaments, New York, NY, Churcl~ill Livingstone, 1994, pp 711-723 13. Graf B, Uhr F: Complications of intra-articularanterior cruciate ligament reconstruction. Clin Sports Med 17:835-848,1988 14. Paulos LE, Wnorowski DC, Greenwald AE: Infrapatellar contracture syndrome. Diagnosis, treatment and longterm followup. Am J Sports Med 22:440-449 15. Bylski-Austrow DI, Grood ES, Hefsy MS: Anterior cruciate ligament replacements: A mechanical study of femoral attachment location, flexion angle of tensioning, and initial tension. J Ortho Res 8:522-531, 1993 16. Graf B: Revision ACL surgery-Tunnel placement. Presented at Arthroscopy Association of North America Interim meeting, New Orleans, LA, February, 1994 17. Howell SM, Taylor MA: Failure of reconstruction of the anterior cruciate ligament d u e to impingement by the intercondylar roof. J Bone Joint Surg 75:1044-!055,1993 18. Karns DJ, Heidt, RS Jr, Holladay BR, et ah Case report: revision anterior cruciate ligament reconstruction. Arthroscopy 10:148-151, 1994 19. Schepsis A , Getelman M, Zimmer J: Revision ACL reconstruction: Aut0graft vs all0graft. Presented at the Arthroscopy Association of North America AnnUal Meeting, San Francisco, CA, May 1995 20. DiStefano VJ: Intraarticular ACL reconstruction: Mechanism of failure analyzed a t revision surgery. Pennsylvania Orthopaedic Meeting, April 6-8,1995 21. Uribe JW: Revision anterior cruciate ligament surgery. Instructional Course at 62nd Annual American Academy of Orthopaedic Surgeon Meeting, Orlando, FL, Februar~ 1995 22. Howell SM, Clark ]A: Tibial tunnel placement in anterior cruciate ligament reconstruction and graft inpingement. Clin Orthop 283:187195, 19£2 23. Howell SM, Clark JA, Farley: Serial magnetic resonance study assessing the effects of impingement on the MR image of the patellar tendob graft; Arthroscopy 8:350-358,1992 24. TanZer M, Lenezer E: The relationship of intra-condylar notch size and content innotch plasty requirement in anterior cruciate ligament surgery. Arthrqscopy 6;89-93~1990 25. Asahina S; Muneta T, Ishibashi T, et ah Effects of knee flexion angle at graft fixation on the outcome of anterior cruciate ligament reconstruction, Arthroseopy 12:70-75,1996
REVISION ACL RECONSTRUCTION
26. Melby A III, Noble JS, Askew MJ, et al: The effects of graft tensioning on the laxity and kinematics of the anterior cruciate ligament reconstruction. Arthroscopy 7:257-266, 1991 27. Nabor ED, Richmond JC, Vannah WM, et ah Anterior cruciate ligament graft tensioning in full extension. Am J Sports Med. 23:488-492,1995 28. Yoshiya S, Andrish JY, Manley MT, et al: Graft tension in anterior cruciate ligament reconstruction. Am J Sports Med 15:464-470, 1987 29. Rubenstein RA, Shetbourne KD VanMeter CD, et al: Isolated autogenous bone-patellar tendon-bone graft site morbidity. Am J Sports Med 22:324-327, 1994 30. Kurosaka M. Yoshiya S, Andrish JT: Biomechanical comparison of different surgical techniques of graft fixation in anterior cruciate ligament reconstruction. Am J Sports Med 15:225-229, 1987 31. Steiner ME, Hecker AT, Brown CH Jr, et al: Anterior cruciate ligament graft fixation. Comparison of hamstring and patellar tendon grafts. Am J Sports Med 22:240-246, 1994 32. Doerr AL, Cohn BT, Ruoff MJ, et al: A complication of interference screw fixation in anterior cruciate ligament reconstruction. Orthop Rev 19:997-1000, 1990 33. Matthews LS, Softer SR: Pitfalls in the use of interference screws for anterior cruciate ligament reconstruction. Arthroscopy 5:225-226, 1989 34. Berg E: Tibial bone plug nonunion: A cause of anterior cruciate ligament reconstruction. Arthroscopy 8:380-384, 1992 35. Laurencin CT, Speciale A, Brause BD, et ah Infection after arthroscoptc anterior cruciate reconstructions. Poster at the 62nd AnnualAmerican Academy of Orthopaedic Surgeon Meeting, Orlando, FL, February, 1995 36. Harner CD, Fu FH: Immune response to allograft ACL reconstruction. Am J Knee Surgery 6:45, 1993 37. Rodrigo JL, Jackson DW, et al: The immune response to freeze dried bone tendon allograffs in humans. Trans ORS, 13:305,1988 38. Thompson WO, Harner CD Jamison J: Immunologic response to fresh frozen patellar tendon allograft anterior cruciate ligament reconstruction. Trans ORS 19:624, 1994 39. Fideler BM, Vangsness "17,Moore T, et al: Effects of gamma irradiation on the human immunodeficiency virus. A study in frozen human bone-patellar ligament bone grafts obtained from infected cadavera. J Bone Joint Surg 76:1032-1035,1994 40. Kerboul L, Christel P, Meunier A: In vitro study of the role of various preservation methods on mechanical properties of allograft of the patellar tendon. Chirurgie 117:751-762. 1991 41. Noyes FR, Barber SD, Simon R: High tibal osteotomy and ligament reconstruction m varus angulation, anterior cruciate ligamentdeficient knees. A two- to- seven-year followup study. Am J Sprots Med 21:2-12,1993 42. Fahey M, Indelicato PA: Bone tunnel enlargement after ACL allograft reconstruction. Orthop Trans 17: 231, 1993 43. Olson EJ, Kang JD, Fu FH, et ah The biomechanical and histiological effects of artificial ligament wear particles in vitro and in vivo studies. Am J Sports Meal 16:558-570,1988 44. Purnell ML, Lamoreaux L: Autogenous quadriceps tendon ACL revlston reconstruction: Long term follow-up study. Sports Medicine 2000, Stockholm, Sweden, June 6-8,1995 45. Jackson DW: Revision ACL surgery: Revision using autograft. Presented at American Orthopedic Society of Sports Medicine Annual Meeting, Sun Valle}~ID, July 1993 46. Goble EM: Discussion to Karns DJ, et al.: Case report: revision anterior cruciate ligament reconstruction, Arthroscopy 10:152-157, 1994 47. Rosenberg TD: Revision anterior cruciate ligament reconstruction using fresh-frozen allograft tissue. Instructional Course at the 62nd Annual American Academy of Orthopaedic Surgeon Meeting, Orlando, FL, February, 1995 48. Veltri DM, Warren RF: Operative treatment of posterolateral instability of the knee. Clin Sports Med 13:615-627, 1994 49. Veltri DM, Warren RF Posterolateral instability of the knee. Instr Course Lect; 44:441-453,1995
189
Anterior cruciate ligament (ACL) reconstruction has gained wide acceptance as the treatment of choice for the functionally unstable ACL-deficient knee and is now performed on about a half million individuals per year. The documented long-term good or excellent result rates for functional stability, relief of symptoms, and return to activity for intra-articular ACL reconstructions is approximately 75% to 95%. This leaves a substantial group of patients with an unsatisfactory result secondary to a variety of reasons. Review of the literature reveals that recurrent instability and graft failure are responsible for unsatisfactory results in as high as 8% of these patients. In this article, the factors responsible for graft failure and recurrent instability are discussed. In addition, the planning and difficulties hhat the orthopedic surgeon must address before, during, and after the procedure, are also reviewed. KEY WORDS: arterior cruciate ligament, failure, revision, reconstruction
Anterior cruciate ligament (ACL) reconstruction has gained wide acceptance as the treatment of choice for the functionally unstable ACL-deficient knee. It is n o w performed on approximately a half million individuals per year. ~ The d o c u m e n t e d long-term good or excellent results of p r i m a r y ACL reconstructions with respect to functional stability, relief of symptoms, and return to activity is between 75% to 950/o.2-9 This leaves a substantial group of patients with an unsatisfactory result, secondary to a variety of reasons, which include (1) continued pain secondary to preexisting degenerative articular cartilage changes within any compartment of the knee, 2,10-12(2) loss of motion associated with operative intervention (arthrofibrosis and infrapatellar contraction syndrome), 13,14and (3) recurrent instability. 2,~°,12,15-1s Review of the literature reveals that recurrent instability and graft failure are responsible for unsatisfactory results in as high as 8% of patients w h o undergo primary ACL reconstructions.2,1°,l~,13 Ideally, revision ACL reconstruction restores function in patients w i t h recurrent instability after a p r i m a r y ACL reconstruction. Harner and Fu classified failed ACL reconstruction w i t h recurrent instability into three groups based on the prim a r y cause for failure2,1°q2: • Technical errors. Included in this category are all surgical errors as well as failure to recognize or properly address laxity in the secondary restraints. e Biological failure. Failure of graft incorporation, biomechanical failure of the tissue (failure of "ligamentization'), infection, or rejection. From the Department of Orthopaedic Surgery, South Jersey Orthopaedic Association; the Department of Orthopaedic Surgery, Thomas Jefferson University Medical Center; Department of Orthopaedic Surgery, Thomas Jefferson University Medical Center, Rothman Institute; and Pennsylvania Hospital, Philadelphia,PA. ~ddress reprint requests to Arthur R. Bartolozzi, MD, 800 Spruce St, Philadelphia, PA 19107. Copyright © 1996 by W.B. Saunders Company 1048-6666/96/0603-0009505.00/0
• Traumatic failure. Subsequent trauma deemed sufficient to rupture an intact and functional graft (Fig 1). Schepsis 1,19 and DiStefano 2° classified failure to recognize or address associated laxity as a fourth category separate from technical errors. [t is our opinion that this error is purely dependent on the physical examination and technical skills of the operative surgeon and thus is better classified as a technical error. To facilitate revision ACL reconstruction, it is vitally important to identify the cause of failure prior to surgery. Many factors are associated with graft failure a n d recurrent instability. These factors are not mutually exclusive, and several different causes can contribute concurrently to failure of a p r i m a r y ACL reconstruction, z1°-12,1~,2°Harner 1° and Distefano 2° documented, respectively, that 60% and 40% of their failed ACL reconstructions h a d primary as well as secondary factors contributing to the failure (Fig 2). Technical Errors
Schepsis reported that 92% of the ACL reconstructions that were revised failed primarily because of a technical errod (Fig 1). H a r n e d ° and DiStefano 2° further a d d e d that technical errors, although not always the primary cause of failure, contributed to failure in 83% and 95% of their cases, respectively (Fig 2). Technical errors include (1) nonanatomic tunnel placement (most c o m m o n technical error), (2) inadequate notchplasty, (3) improper tensioning of the graft, (4) inadequate or improper fixation of the graft in the b o n y tunnels, (5) failure to recognize or properly address laxity in secondary constraints, (6) poor graft selection, and (7) improper or inadequate graft harvest or preparation. Nonanatomic Tunnel Placement
The literature reports that 70% to 80% of the technical failures were due to improper tunnel placement 2.1°-I2,19-21 (Fig 3). The majority of these failures were related to an improperly placed femoral tunnel. 2,1°-12,I9-2I This is clearly
Operative Techniques in Orthopaedics, Vol 6, No 3 (July), 1996: pp 181-189
"181
[mSchepsis [] DiStefano • Harner [] Uribe ]
In Schepsis [] DiStffano • Harner [] Uribe]
I00~ 81% 82%
75% S0~ 25% 17% f ~
15% 14%
25%
4% 5% 5% Nonanat omic Tunnel
0%
Technical Errors
Traumatic
Biological
Causes
Causes
Fig 1. Factors responsible for failure of ACL reconstruction can be divided into three major categories: (1) technical errors, (2) biological derivations, and (3) traumatic causes. In the four major series by DiStefano, 19 Harner, ~° Schepsis, 20 and Uribe, 21 technical errors were responsible for approximately 60% to 90% of failures.
because of the significant impact that femoral tunnel location has on the isometric behavior of the graft during range-of-motion of the knee. 2° An ACL graft can only withstand a small amount of strain prior to plastically deforming. Excessive tension and strain will cause inA 100% 83% 75%.
50%.
25%
18%
i [ [
o%.,~
Technical Errors
Traumatic
Biological
Causes
Causes
E" 100%
Fixation
Notch Impingement
Associated Laxity
Inadequate Graft
Fig 3. Technical errors can be subdivided into five main categories: (1) nonanatomic tunnel placement, (2) inadequate or improper fixation, (3) inadequate notchplasty, (4) unrecognized or unaddressed associated laxity, and (5) inadequate graft harvest or selection. Nonanatomic tunnel placement was primarily responsible for as much as 70% to 80% of failures, with a majority of these errors related to femoral tunnel placement. The remainder of failures were the results of the other reasons listed.
creased laxity of the graft and failure of the reconstruction. Placing the femoral tunnel too far anterior on the lateral femoral condyle and fixing it at 0 ° to 30 ° of extension will therefore produce excessive graft strain when the knee is flexed. Placing the graft in a posterior (over-the-top) position will result in excessive laxity of the graft in flexion and increased tension in extension (Fig 4). Although not as crucial as the femoral tunnel, it is still important to properly place the tibial tunnel. A tunnel drilled too far anterior on the tibia will cause excessive tension on the graft in both flexion and extension. In addition, Howell m22 has documented that an anterior tibial tunnel will cause the graft to impinge on the roof of the femoral notch. A tunnel placed too far posterior on the tibia results in excessive laxity of the graft in flexion. In addition, if the tunnel is placed too far medially or laterally on the tibia, the graft will impinge on the walls a n d / o r roof of the notch. Howell stresses the value of magnetic resonance imaging (MRI) and lateral radiographs of the knee in extension to evaluate the status of the graft and tunnel placement 2s (Fig 5).
75%
Inadequate Notchplasty 50%
25%
0%
Technical Errors
Traumatic
Biological
Causes
Causes
Fig 2. Factors responsible for failure of an ACL reconstruction are not mutually exclusive. More than one factor can contribute to failure. (A) Harner 1° and (B) DiStefano is both documented that 60% and 40%, respectively, of their failed revision ACL reconstructions had primary as well as secondary factors contributing to the failure of the initial reconstruction.
182
Graft sources are usually larger than the original ACL. Inadequate notchplasty causes impingement of the graft on the roof, as well as the wall of the notch. If an adequate amount of bone is not removed from the anterior/superior portion of the notch, the graft will impinge in extension, and flexion contracture may result. 24 Schepsis, ]9 Distefano, 2° and Harned ° all reported that approximately 5% of their revision cases had impingement with subsequent lack of extension and failure of the reconstruction. A graft usually fails secondary to repetitive trauma and attrition from friction against the notch as the knee goes into extension. 13,17,22,23 In addition, as the knee cycles from flexion to terminal extension, this repetitive stress may fatigue the fixation device. This may result in fi afion failure prior to graft incorporation. Furthermore, insufficient removal of WETZLER ET AL
decreased anterior translation but will also increase tibiofemoral contact forces, which may accelerate degenerative changes. Overtensioning can also cause elongation of the graft, postoperative loss of motion, or possible fixation failure. 15 Furthermore, Yoshiya has proposed that overtensioning may decrease incorporation, delay vascularization, and cause mvxoid degeneration of the graft. 2s
Failure to R e c o g n i z e or Address Associated Instability
Failure to recognize or address associated pathological laxities may result in a sensation of continued instability or lead to actual giving way and result in damage to the reconstructed ACL. Schepsis 1,19 reported that failure to recognize or address associated instability patterns (posteriolateral rotatory instability [PLRI], anteriomedial rotatory instability [AMRI]) contributed to 15% of the failed ACL reconstructions they revised. DiStefano 2° reported that associated laxity was primarily responsible for 25% of the cases he revised (Fig 3). In all primary and revision ACL reconstructions, the patient must be assessed for any associated secondary laxity patterns, both preoperatively and intraoperatively. Graft Fixation
In recent years, results have improved from accelerated rehabilitation programs as popularized by Shelbourne. 7'29 Thus, more importance and increased stress is placed on Fig 4. (A) An improperly placed femoral tunnel can cause excessive length changes in the graft, with the graft becoming nonfunctional. (B) Revision notchplasty is required to visualize the previous tunnels, as is the over-the-top position to guide in new tunnel placement. The markings on the probe are 5 mm in width. Notice how the original tunnel is at least 10 mm anterior from the posterior wall of the femoral notch. In this situation, a new tunnel can usually be drilled with minimal interference from the previous tunnel.
the lateral wall of the notch, especially inferiorly (distally), will also produce attrition and subsequent graft failure. 2° Injury to the graft from impingement has been confirmed with MRI results. Grafts that do not impinge will have a signal similar to that of a tendon. Impingement results in changes in the midsubstance of the graft, which will be represented by an increased signal or narrowing o f its substance on MR117,22,23(Fig 5). Improper Tensioning
Although the exact amount of tension has not been determined, it is vital that the graft be placed and fixed under adequate tension. Many investigators initially attach the femoral side, and then tension and fix the tibial side, between full extension and 30 ° of flexion. 9,15,24-27The graft is then checked for proper tension through a full range of motion. Undertensioning of the graft during fixation will result in immediate residual postoperative laxity. Overtensioning has been associated with poor graft incorporation, decreased graft strength, and increased constraint of the knee. 28 Increased constraint of the knee will produce REVISION ACL RECONSTRUCTION
Fig 5. Howell 22 stresses the value of MRI and lateral radiographs of the knee in extension to evaluate the status of the graft and tunnel placement. A tunnel placed too far anteriorly on the tibia will cause impingement on the notch. Injury to the graft from impingement has been confirmed with MRI studies. Grafts that do not impinge will have the normal signal of a tendon. Impingement will result in changes in the midsubstance of the graft, which will be represented by an increased signal or tapering of the graft on MRI, as shown here.
183
the fixation of the graft. Schepsis 19 and Harner 1° reported that inadequate fixation, respectively, contributed to 8% and 14% of their failed primary reconstructions. DiStefano described three cases (15%) in which the fixation was improperly placed and abraded the graft, causing the graft to fail.2° The strength of fixation techniques has been extensively studied. 3°,31 Regardless of technique, the fixation must be properly placed and hold during the early postoperative period to prevent changes in tension during rehabilitation.30,32,33
Graft Selection and Harvest
Harner has reported a case of an inadequately harvested graft that contributed to its eventual failure. 1° Uribe, in addition, discussed three cases that had progressive or persistent laxity following the original reconstruction with an incompetent graft. 21 These grafts were unable to withstand the physiological stresses during normal activity and subsequently failed. Several different types of grafts are currently used: • Autograft Bone-patella tendon-bone central one third Hamstring Quadriceps--Patella Iliotibial band • Allograft Bone-Patella Tendon-Bone Achilles tendon Iliotibial band • Synthetic and LAD have fallen out of favor. Biological F a i l u r e
Any graft used for reconstruction of the ACL is biologically different than the original ACL. The most obvious difference is collagen type and fibril size, length, and orientation. The inability of the reconstructed ACL to exactly duplicate the natural ACL in certain cases contributes to graft failure (Table 1). The reconstructed ACL may not revascularize or biologically adapt ("ligamentize'). Additionally, biological failure of the graft can occur because of failure of the graft incorporation, 2,1°bone plug healing, 34 infection,35 or rejection of the graft (if an allograft is used).35 Harner reported that 14% of failures were directly the result of failure of graft incorporation (80% were allografts). 1° Although not the primary cause of failure, failure of graft incorporation contributed to another 25% of Harner's reported failures. 2,m Berg also noted that nonunion of the bone plugs can be a contributing factor to failure of an ACL reconstruction. 34 If an allograft is used, an immunological reaction, ie, rejection, must be c o n s i d e r e d . 1,2,11,12,19,20,36,37Thompson and Harner reported that approximately 60% of patients who underwent allograft reconstruction of their ACL will mount some type of immunological reaction, which may hinder graft incorporation. 1°,35,37In contrast to allografts, Schepsis reported an 8% biological failure rate using only autografts. 2° 184
TABLE 1. Biological Differences Between a Tendon Graft and Normal ACL Anterior Cruciate Ligament
Tendon Graft
Ligament fibers of different length. During ROM, fibers see different tension and loads Fibers are not parallel Bimodal fibril diameter (type I collagen)
Fiber is uniform length Tensioning is a composite of all the fibers and is randomly distributed Fibers are parallel At the time of reconstruction the fibril pattern is different then the pattern after incorporation The replacement fibroblasts are not capable of re-establishing the inherent characteristics of the normal ACL Aneural except for those receptors accompanying revascularization
Complex relationship of ACL fibroblasts surrounded by and interacting with biopolymers synthesized by these cells Mechanoreceptors as well as pain fibers provide proprioception and neurosensory function Distinct vascular supply
Variable vascular supply
Abbreviations: ROM, range of motion; ACL, anterior cruciate ligament. Adapted and reprinted with permission. 21
Other Causes
of F a i l u r e
Laurencin and Warren reported on seven cases of infection in approximately 2,200 ACL reconstructions (0.3% infection rate). This is similar to the infection rate for total joint arthroplasties. Infections require prompt and thorough irrigation and debridement. Whether to remove the graft and fixation should be decided on an individual basis and depends on the causative organism, magnitude of the infection, and the specific graft and hardware usedY Lastly, Paulos discussed the etiology and treatment of arthrofibrosis and infrapatellar contracture syndrome with significant fibrosis and scarring, with resultant and severe decrease in range of motion. To restore motion and function, manipulation of the knee a n d / o r debridement of scar tissue as well as the graft may be required; early intervention is essential. If the patient is severely limited at 6 weeks, intervention consisting of manipulation, arthroscopy, and debridement is advised. Patients should be counseled that manipulation can cause graft rupture and that graft removal in some cases may be necessary to regain motion leaving the knee once again unstable. 14 Traumatic
Causes
Fu believes that in an athletic population 5% to 10% of ACLs reconstructed will fail secondary to repeat trauma even if a technically perfect ACL reconstruction was performed. 1,2,11a9 Harner 1° and Uribe, 21 respectively, reported that a traumatic episode was responsible for failures in 25% and 43% of their patients undergoing revision ACL reconstruction. Schepsis believes that the incidence of true traumatic reruptures is lower and that pure reruptures rarely occur. Most traumatic reruptures have contributing factors, and these figures do not account for these factors. 1,19Traumatic re-ruptures can be subdivided into two categoriesa,n,12: (1) Failures secondary to early trauma before complete graft incorporation and the completion of rehabilitation; and (2) late trauma after resuming full activities. Graf has implicated overzealous rehabilitation or too WETZLER ET AL
early return to activity in graft failure. 13With the implementation of aggressive rehabilitation protocols, physicians have to temper the aggressive rehabilitation against the risk of failure of the ACL graft. It is essential to have secure fixation of the graft prior to embarking on an aggressive rehabilitation program. Tendon-to-bone healing can take up to 8 to 12 weeks, whereas bone-to-bone healing is somewhat faster. Stability of graft fixation must be factored in selecting a rehabilitation program. In late failure secondary to significant trauma associated with a large hemarthrosis, it is assumed that the patient had returned to full activity, the knee was stable, the graft had been incorporated and was functioning at the time of injury. Rubenstein and Shelbourne believe that most early failures are traumatic prior to graft incorporation, whereas late failures have multiple contributing factors as described earlier. 29It is unclear how accurate this assumption is and what other factors may play a rote in graft failure. In recent literature, there have been several reports discussing the effects of the sterilization process on disease transmission and resultant graft strength. 39,40 Allografts that are irradiated, can be weakened by the process. 4° The general recommendation is to use less than 2.5 Mrad radiation, but many surgeons prefer fresh frozen nonirradiated grafts because of the improved mechanical properties .39
OPERATIVE AND TECHNICAL CONSIDERATIONS Preoperative Planning Harner has shown that revision ACL reconstruction can restore function. 2,1°-12 The patient should have realistic goals about their return to sports versus their ability to do their activities of daily living without instability. The orthopaedic surgeon should be aware of patients that will "trash their knees" no matter how much they are instructed against it. These "knee abusers" will test any reconstruction or revision. An understanding of all surgical options and approaches is essential when a surgeon considers revision ACL surgery. Familiarity with different techniques of tunnel placement (one v two incisions), graft harvesting and preparation techniques, as well as various methods of graft fixation, is essential. This will allow the surgeon flexibility to anticipate and adapt to the unique situation when he or she is performing a revision ACL reconstruction. The preoperative workup should include MRI to assess joint surface conditions, meniscal disease, and tunnel size, positions, and possible tunnel enlargement erosion. A lateral knee radiograph in full extension is also useful in assessing tunnel placement13,23,24 (Fig 5). Standing anteriorposterior radiographs are helpful to assess alignment of the lower extremity. In long-standing ACL deficiency, double or triple varus knees, as described by Noyes, may develop and should be addressed during revision ACL reconstruction. 4~ A thorough preoperative evaluation of laxity is imperative. The examination should begin with careful observation of gait, Detection of a subtle undiagnosed laxity REVISION ACL RECONSTRUCTION
pattern is required to ensure proper repair a n d / o r reconstruction and, therefore, preventive failure of the revision ACL reconstruction.l,13,2°,43
One-Staged Versus Two-Staged Procedures If the previous surgery has resulted in tunnel enlargement ~ that left large bony tunnels that will interfere with placement of new tunnels, consideration must be given to bone grafting the tunnels and staging the final reconstruction. The patient must be advised of this possibility preoperatively. In addition, if the patient has a significant loss of motion, (extension > 5 °, flexion > 20°), this must be rega!ned before the definitive reconstruction, and the procedure might need to be staged. 2,1°-12
Incision Placement Old incisions should be used whenever possible to perform the procedure and to remove any residual hardware; avoid skin bridges of less than 7 cm. If there are multiple incisions, consider using an allograft to minimize the incisions. Careful surgical technique with delicate handling of the soft tissue, as well as opening and closing the periosteum with care, is needed to prevent soft tissue and wound complications. 2,12
Hardware Removal Depending on the graft used in the initial ACL reconstruction, the surgeon may need to have an assortment of fixation devices, such as interference screws, staples, cortical and cancellous screws, and washers. A variety of screw drivers are needed to remove the different interference screws. It may be difficult to find the interference screw or other fixation devices. At times, a pneumatic burr or hollow mill may be required to remove bone that has overgrown and covered the fixation devices. The appropriate screw driver that fully seats into the head of the screw is a necessity. A stripped screw can lead to extensive bone removal that may require bone grafting and compromise fixation of the revision graft. The surgeon should contemplate whether a staged revision might be more appropriate, and sometimes this determination can only be made at the time of surgery. A femoral screw in a two-incision technique may need to be removed, but with endoscopic technique it may be left in place because the trajectory of the tunnels are different.2,11,12 If staples are used as the femoral fixation, a prong may interfere with tunnel placement and require removal. This is never an easy procedure.
Prosthetic Ligament Removal An en-bloc removal of the prosthetic ligament is preferred because particulate debris from synthetic ligaments has incited an inflammatory response. A synovectomy may be necessary if the synthetic ligament is frayed and has already disintegrated into the joint. 43In addition, synthetic ligaments may cause enlargement of the bone tunnels, and it might be wise to graft the tunnels initially and stage the revision reconstruction once the bone tunnels are healed. ~3,2°,43Removing a well-ingrown synthetic ligament may require overdrilling the graft with a hollow mill. 185
Graft Selection
Graft choices include allograft and autograft materials. Allografts include patella and Achilles tendon, whereas autografts can include patellar tendon, either from the ipsilateral or contralateral knee, quadriceps tendon, iliotibial band, or the hamstring tendon (semitendinosus/ gracillis). Schepsis recently reported similar results using allografts and autografts. 19 Purnell reported good results using a partial-thickness quadriceps tendon with a bone plug from the proximal patella. 44 Some orthopaedic surgeons favor the use of hamstring tendons because they allow more flexibility of tunnel size and placement; fixation can be accomplished with an Endobutton (Acufex Inc, Norwood, MA). The Endobutton is like a molly bolt or grappling hook and relies on an intact femoral cortex, rather than intact femoral tunnel, and an interference fit with a screw. Furthermore, the Endobutton requires no additional incisions as would be necessary when screws or staples are used. Fixation of the hamstring may be accomplished with a screw through the femur and thus does not rely on an intact femoral cortex of the tunnel. Fixation is enhanced with the use of a bone graft in certain instances. Additional pros and cons of selecting a graft for a revision are summarized in Table 2. 2"10-12'20'21'29'45 Recently, some orthopaedic surgeons have contemplated reharvesting the middle third of the patella tendon as a graft source. This is more popular in Europe. 18,43Sequential MRIs of the harvest site have documented reconstitution of the patella tendon at 1 year. 2,1°-12,2°,29Biopsy specimens of the reharvested tendon have shown normal tendon architecture. Karns et al is recently reported a case of a revision ACL reconstruction using a reharvested patella tendon 4 years after the original reconstruction. Goble is concerned with the mechanical properties and tensile strength of this reharvested tendon. 46As of yet, there are no biomechanical studies documenting the mechanical properties and tensile strength of the reharvested bone-patella tendon-bone graft as compared with a virgin-harvested graft. It is difficult to recommend this graft selection at this time, because there TABLE 2. Pros and Cons of Different Graft Sources Used for Revision ACL Surgery Pros Autograft
Patient's own tissue; there is no chance of rejection or "delayed incorporation" No extra cost Available and AIIograft strong No donor site morbidity Shorter tourniquet Smaller incision Flexibility with size and width of bone plugs Synthetic Available Minimal morbidity
Cons
Status
Graft site morbidity (PF pain or hamstring weakness) Limited availability
Used for hamstrings or failed allografts with technical errors that do not compromise tunnel placement Used for failed autografts Used for failed allografts with obvious technical errors or failure from traumatic reinjury Not currently indicated
"Delayed Incorporation" immune reaction HIV and disease transmission Irradiated (effects on mechanical properties) Expensive Stiffer than ACL, which leads to
failure Inflammatory reaction Adapted and reprinted with permission. 1° 186
Fig 6. In patients with long-term deficiency of the ACL, the notch narrows over time, filling up with soft tissue and bony overgrowth. A bone-patella-bone (allograft or autograft), hamstring tendons, or other graft sources are usually larger than the original ACL. An adequate notchplasty is necessary so that the over-the-top position can be properly visualized and proper tunnel placement can be assured.
are more reliable grafts with documented good results (both autografts and allografts). Revision Notchplasty
Some natural overgrowth of the notch will occur after an ACL reconstruction. Ideally, the graft should not impinge at all. Revision notchplasty is required to visualize the previous tunnels, as well as the "over-the-top" position to guide in new tunnel placement (Fig 6). In addition, revision notchplasty will prevent impingement from the lateral femoral condyle or superior notch. 2,12,1s Bone Tunnels
Selecting and creating the proper bone tunnels during a revision of an ACL reconstruction can be the most challenging portion of the procedure. The treatment of different technical errors or problems with tunnel placement are summarized in Tables 3 and 4.1° In the initial assessment of any patient prior to revision ACL reconstruction, the surgeon must determine if the procedure should be performed in stages. If the tibial or femoral tunnels are drilled too far anteriorly, often the tunnels may be redrilled in the optimal position with little interference from the previous improperly placed tunnels (Fig 7). On the femoral side, correct tunnel placement can be facilitated by using a two-incision approach when an endoscopic procedure was done originally, and visa versa (Fig 8). By using a different technique (two-incision endoscopic) the new tunnel will quickly diverge from the old tunnel and allow adequate fixation with an interference screw (Fig 9). If the tibial tunnel is only slightly anterior and the optimal placement would encroach on the previous tunnel, several techniques may be used to solve this error. The surgeon can expand the tunnel posteriorly and fashion a larger bone plug from an allograft. If an autograft is preferred, a core of bone obtained from drilling WETZLER ET AL
TABLE 3. Suggestions on How to Best Resolve the Problems of Improperly Placed Tibial Tunnel Placement Location
Options
Too far anterior or posterior
Redrill the tunnel in the optimal position.
Slightly anterior
Expand the tunnel posteriorly and use a larger ACL bone plug (allograft) Expand the tunnel posteriorly and place the ACL graft posteriorly and bone graft anteriorly (allograft or autograft).
Slightly posterior
Expand the tunnel anteriorly and use a larger ACL bone plug (allograft) Expand the tunnel anteriorly and place the ACL graft anteriorly and bone graft posteriorly (allograft or autograft)
Large capacious tunnel (usually occurs when an Achilles tendon allograft or synthetic graft are used)
Use a larger bone plug (allograft) Simultaneous use of bone graft and ACL graft in appropriate position Stage the procedure: 1st stage: Bone graft the tunnel 2nd stage: ACL reconstruction after incorporation of bone graft
Adapted and reprinted with permission. 21
the new tunnel or a graft core obtained from the tibial may be used to graft the tunnel. Interference fixation may be difficult, so the surgeon may need an alternate type of fixation other than an interference screw (ie, screw and washer, staple, or the Endobutton). In addition, sometimes a second interference screw can be used as a spacer. A femoral tunnel placed slightly anteriorly can be treated in several wavs. The surgeon may choose to convert to the over-the-top position or the two-incision approach. Rosenberg has described another method for coping with this technical error that uses a quadruple hamstring graft. He divides the graft into two halves, and through two 6-ram femoral tunnels, he attaches each graft to the femur with a separate Endobutton. 47 This allows tunnel placement m an optimal position without interference from the previous malpositioned tunnels. If a twoincision approach is used, the graft may be fixed directly to the femur through the lateral incision with a screw, staple, or Interference screw. If the tibial tunnel is too far posteriorly In the tibia, the surgeon can expand the tunnel anteriorly and either use a larger bone plug or graft posteriorly in just the opposite
Fig 7, The tibial tunnel is viewed with the scope. The initial placement of the tibial interference screw allowed redriliing of the tibial tunnel in optimal position with little interference from the previous screw,
fashion to that described for a tunnel placed too far anteriorly. In the femur, if the tunnel is too far posteriorly, the posterior wall is usually blown out, and this usually requires the surgeon to convert to the over-the-top or two-incision technique to gain adequate femoral fixation. One of the most difficult problems associated with a failed synthetic graft or allograft is a large capacious tunnel. 42,43 This usually occurs with svnthetic allografts. The resultant defect after the graft is removed may be difficult to treat. Adequate assessment with computed tomography scan in the plane of the tunnel or MRI scan may be helpful. The surgeon can use one of three techniques: (1) use a larger bone plug from a allograft, (2) simultaneously bone graft the tunnel and place the ACL and bone plug in the optimal position with a bone plug core obtained with a coring reamer; or (3) bone graft the tunnel and stage the procedure. Usually the surgeon must stage the procedure, the tunnel should be bone grafted, preferably with autograft to accelerate incorporation. Once the graft has healed, a surgeon may proceed with the revision ACL reconstruction, drilling the tunnels in the optimal position.
TABLE 4. Suggestions on How to Best Resolve the Problems of Improperly Placed Femoral Tunnel Placement Location
Options
Too far anterior
Redrill the tunnel in the proper position ignoring the old tunnel Expand the tunnel posteriorly and use a larger ACL graft bone plug (allograft) or convert to "overthe-top" two-incision technique Same as tibial technique or use an alternative fixation device such as the Endobutton Convert to "over-the-top" two-incision technique or use alternative fixation device such as the Endobutton Use endoscopic technique to create a divergent tunnel
Slightly anterior Large, capacious tunnel Blowout posteriorly Two-incision tunnel (outside-in)
Adapted and reprinted with permission 21 REVISION ACL RECONSTRUCTION
Fig 8. The initial femoral tunnel was drilled too far anteriorly. The new femoral tunnel was easily drilled in the optimal position without interference from the old tunnel.
187
Fig 9, A two-incision approach was performed for the original ACL reconstruction, Endoscopic technique was used for the revision surgery, and the new femoral interference screw quickly diverged from the original interference screw, Graft Fixation
As with placement of the bone tunnels it is advantageous to know different types of graft fixation. Usually, fixation is performed with interference screws. Additional fixation methods include several new techniques to fix hamstrings such as the bone mulch technique (Arthrotek, Ontario, CA) and interference screw fixation techniques for the hamstring developed by Smith & Nephew DonJoy (Carlsbad, CA) as well as Arthrex. Addressing Associated Laxity
As stated previously, the surgeon must address and correct all associated laxity at the time of the ACL reconstruction revision. Residual PLRI must be corrected or the revision reconstruction may fail. The posterior lateral corner (PLC) structures include: popilteus, lateral collateral ligament (LCL), arcurate ligament, a n d / o r the popilteofibular ligament. Unlike the posterior medial corner, these are discrete structures and like the ACL, will not heal properly if incompetent. Often, the PLC structures are intact and are lax either from partial tearing during the original injury or from secondary elongation from chronic ACL deficiency and recurrent giving away. In this scenario, excessive laxity 188
of the PLC structures may be corrected by recessing the femoral attachments of the popilteus and LCL. This tightens the PLCs without changing their axis of rotation. If the popilteus, LCL, accurate ligament, a n d / o r the popilteofibular ligament are disrupted, reconstruction of these structures with an allograft or autograft is essential to restore stability. The Achilles tendon allograft is well suited for this reconstruction. An Achilles tendon allograft can be split with both ends remaining attached to one bone plug. 48,49 The bone plug is placed in the insertion of the LCL/popilteus tendon, and the two bundles of the Achilles tendon are used to reconstruct the torn structures of posterolateral corner. The choice of autograft for this procedure depends on what structures remain from the previous ACL reconstructions. A patient with long-term PLRI and ACL might develop double or triple-varus alignment of the lower extremity, as described by Noyes. 41A valgus osteotomy, in addition to a reconstruction of the posterolateral comer of the tibia is required. The valgus osteotomy accomplishes two things: (1) correction of the varus alignment, and (2) prevention of excessive tension on the reconstructed posterolateral corner. Reconstruction of AMRI (posterior medial corner) is less complex than reconstructing the posterolateral corner. The posterior medial corner is made up of the deep medial collateral ligament (MCL), which becomes confluent with the superficial MCL to form the posterior oblique ligament (POL). These structures do not need to be reconstructed separately as on the lateral side, because they are not discrete bands of tissue but sheets of tissue in layers. The POL and deep MCL are more substantial and confluent compared with the structures of the posterolateral comer. Therefore, if these structures are lax, they may be reefed rather than reconstructed. An oblique incision is made in the POL, and sutures are placed in the POL. After the ACL is reconstructed and the graft fixed, the POL is advanced, and the sutures are tied in a "pants-over-vest" fashion.
Postoperative C a r e
and Rehabilitation
Patients should be advised that ACL revision is a salvage procedure with often unpredictable results. Rehabilitation after revision ACL reconstruction is not the same as after a primary reconstruction; special consideration in rehabilitation of these patient must be taken into account. Many of these patients have had reconstruction of their secondary constraints or have persistent laxity because of prolonged ligament laxity. The rehabilitation protocol must be tailored to the individual and security of fixation of the graft must be taken into consideration. The general rule in designing a rehabilitation protocol is to respect graft healing. Activity is limited, with protective weight bearing on crutches for 2 to 8 weeks, patients are advised that a return to sporting activities takes at least 1 year.
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WETZLER ET AL
3. Harter RA, Ostering LR, Singer KM, et al: Long-term evaluation of knee stability and function following surgical reconstruction for anterior cruciate insufficiency. Am J Sports Med 16:434443,1988 4. Holmes PF, James SL, Larson RL, et al: Retrospective direct comparison of three intra-articular anterior cruciate ligament reconstruction. Am J Sports Med 19:596-600, 1991 5. Howe JG, Johnson RJ, Kaplan MJ, et al: Anterior cruciate ligament reconstruction using quadriceps patella tendon graft: I. Long term follow-up. Am J Sports Med 19:447-57,1991 6. Korblatt I, Warren RF, Wickiewicz TL: Long-term follow-up of anterior cruciate ligament reconstruction using quadriceps tendon substitute for chronic anterior cruciate ligament insufficiency. Am J Sports Med 16:444-448, 1988 7. Shelbourne DK, Whitaker JM, McCarroll JR, et al: Anterior cruciate ligament reconstruction of acute tears without repair. Am J. Sports Med 18:484-489,1990 8. Shimo K, Inque M, Horibe S, et al: Reconstruction of the anterior cruciate ligament using allogenic tendon: Long term follow-up. Am J Sports Med 18:457-465,1990 9. Sisk TD: Knee injuries, in Crenshaw AH (ed): Campbell's Operative Orthopaedics. vol 3. Eighth edition. St Louis, MO, Mosby-Year Books, 1992, pp 1487-1732 10. Harner CD: Revision anterior cruciate ligament reconstruction using fresh-frozen allograft tissue. Instructional Course at the 62nd Annual American Academy of Orthopaedic Surgeon Meeting, Orlando, FL, February, I995 11. Johnson DL, Harner CD, Maday MG: Revision ACL surgery, in Fu FH, Harner CD, Vinve KG (eds): Knee Surgery, Baltimore, MD, Williams & Wilkins, 1994, pp 877-895 12. Maday MG, Harner CD, Fu FH: Revision ACL surgery: evaluation and treatment, in Feagin JA (ed): The Crucial Ligaments, New York, NY, Churcl~ill Livingstone, 1994, pp 711-723 13. Graf B, Uhr F: Complications of intra-articularanterior cruciate ligament reconstruction. Clin Sports Med 17:835-848,1988 14. Paulos LE, Wnorowski DC, Greenwald AE: Infrapatellar contracture syndrome. Diagnosis, treatment and longterm followup. Am J Sports Med 22:440-449 15. Bylski-Austrow DI, Grood ES, Hefsy MS: Anterior cruciate ligament replacements: A mechanical study of femoral attachment location, flexion angle of tensioning, and initial tension. J Ortho Res 8:522-531, 1993 16. Graf B: Revision ACL surgery-Tunnel placement. Presented at Arthroscopy Association of North America Interim meeting, New Orleans, LA, February, 1994 17. Howell SM, Taylor MA: Failure of reconstruction of the anterior cruciate ligament d u e to impingement by the intercondylar roof. J Bone Joint Surg 75:1044-!055,1993 18. Karns DJ, Heidt, RS Jr, Holladay BR, et ah Case report: revision anterior cruciate ligament reconstruction. Arthroscopy 10:148-151, 1994 19. Schepsis A , Getelman M, Zimmer J: Revision ACL reconstruction: Aut0graft vs all0graft. Presented at the Arthroscopy Association of North America AnnUal Meeting, San Francisco, CA, May 1995 20. DiStefano VJ: Intraarticular ACL reconstruction: Mechanism of failure analyzed a t revision surgery. Pennsylvania Orthopaedic Meeting, April 6-8,1995 21. Uribe JW: Revision anterior cruciate ligament surgery. Instructional Course at 62nd Annual American Academy of Orthopaedic Surgeon Meeting, Orlando, FL, Februar~ 1995 22. Howell SM, Clark ]A: Tibial tunnel placement in anterior cruciate ligament reconstruction and graft inpingement. Clin Orthop 283:187195, 19£2 23. Howell SM, Clark JA, Farley: Serial magnetic resonance study assessing the effects of impingement on the MR image of the patellar tendob graft; Arthroscopy 8:350-358,1992 24. TanZer M, Lenezer E: The relationship of intra-condylar notch size and content innotch plasty requirement in anterior cruciate ligament surgery. Arthrqscopy 6;89-93~1990 25. Asahina S; Muneta T, Ishibashi T, et ah Effects of knee flexion angle at graft fixation on the outcome of anterior cruciate ligament reconstruction, Arthroseopy 12:70-75,1996
REVISION ACL RECONSTRUCTION
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