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Medial patellofemoral ligament reconstruction using a hamstring graft
MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION USING A HAMSTRING GRAFT ETHAN J. SCHOCK, MD, and ROBERT T. BURKS, MD
Recurrent lateral dislocation of the patella has been historically treated with a combination of multiple techniques including lateral release, proximal realignment, medial reefing, and distal realignment. Poor-quality medial retinacular tissues and nonanatomic surgical attempts to restrain the patella may contribute to notable problems with redislocation and anterior knee pain. Recent biomechanical studies have identified the functional importance of the medial patellofemoral ligament as the primary restraint to lateral translation of the patella. A technique of reconstruction of this ligament with a single semitendinosis autograft, which provides a sturdy check-rein to lateral translation, is described. The authors' current indications for this procedure are (1) the recurrent lateral patellar dislocations in a patient with poor-quality medial soft tissues and no definable MPFL, and (2) the failure of previous proximal or proximal and distal realignment procedures with continued medial functional deficiency. KEY WORDS: medial patellofemoral ligament, patellar dislocation, autograft tendon Copyright © 2001 by W.B. Saunders Company
Recurrent lateral dislocation of the patella remains a challenging problem for the orthopedic surgeon because of many complex contributing factors such as generalized ligamentous laxity, inadequate medial retinacular tissue, insufficient trochlear groove restraint (Fig 1), patellar tendon length abnormalities, limb-alignment torsional abnormalities, and others. Nonoperative treatment of primary patellar dislocations has reported redislocation rates of 15% to 440/o.1-6 Management of these recurrent dislocations often includes lateral release with proximal a n d / o r distal realignment. Although short-term results of operative management have been good, 7-9 recurrent dislocations have been reported in up to 21% of patients evaluated with longer follow-up. 1°-12 In addition to recurrence of patellar instability, several investigators have reported postoperative problems with anterior knee pain, medial dislocation, chondral damage, and chronic effusions. 7-9,1°,12It is reasonable to presume that some of these failures are related to the complexity of variable injuries to the stabilizing structures. Articular damage may have been incurred before surgical management, as well. The medial extensor mechanism has been described by numerous investigators 13-1s however, it is only recently that the significance of the medial patellofemoral ligament has been widely appreciated. 14,16-1s Conlan et a117 performed a serial-sectioning study of the medial soft tissues of cadavers and found that the medial patellofemoral ligament (MPFL) contributed an average of 53% of the total
From the University of Utah Department of Orthopaedic Surgery, Salt Lake City, UT. Address reprintrequests to Ethan J. Schock, MD, 50 North Medical Dr, Salt Lake City, UT 84132. Copyright © 2001 by W.B. Saunders Company 1060-1872/01/0903-0010535.00/0 doi:l 0.1053/otsm.2001.25235
restraining force to lateral displacement of the patella. The authors' studies of the anatomic and biomechanical properties of the MPFL have shown similar results: the MPFL provides the primary restraint to lateral patellar displacement at 20 ° of flexion, contributing 60% of the total restraining force. Is A further study has shown that changes in patellar tracking in the medial soft-tissue-deficient knee with a laterally directed force can be significantly reversed by reconstructing the MPFL. 19 An understanding of the anatomy of the medial side of the knee is important when evaluating the medial patellar stabilizers. The femoral origin of the MPFL is located in layer 2 of the medial knee. It begins with an arc of fibers continuous with the anterior edge of the superficial medial collateral ligament near the medial epicondyle with other fibers originating from the adductor tubercle or medial epicondyle or both, with individual variation. The MPFL inserts on the proximal medial edge of the patella. The vastus medialis obliquus (VMO) inserts on the ligament over a variable distance near the patellar insertion. Figure 2 is taken from a cadaveric dissection, and Figure 3 is an arthroscopic view of the MPFL after synovectomy for an unrelated problem. Conlan et a117found the MPFL to be a distinct ligament in 29 of 33 cadaveric specimens. However in cases of chronic instability, with scar tissue obscuring attenuated tissue planes, it can be difficult or impossible to identify the ligament. An understanding of the precise site at which the MPFL fails should enhance the ability to treat related patellar instability. However, there is debate over exactly where these tears occur. Sallay et al 2° and Avikainen et a121 evaluated patients with acute patellar dislocations and found tears of the retinaculum from the femur in almost all patients. Sargent and Telpher 8 noted tears from the patella in all patients. Yamamoto 22 found a distinct medial capsular tear in all of his patella dislocation patients, but none
Operative Techniques in Sports Medicine, Vol 9, No 3 (July), 2001: pp 169-175
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Fig 1. Merchant view of a 17-year-old female patient with recurrent lateral patellar dislocation. Note the shallow trochlea.
directly from the femur. The authors' laboratory results and clinical experience suggest that the MPFL is most often injured on the femoral side but can be torn in its midsubstance. ~6 The authors have noted injury adjacent to the patella but attribute this to the avulsion of the medial patellomeniscal ligament (Fig 4). They have found no failures of the MPFL patellar insertion. Figure 5 is an arthroscopic view of the medial gutter showing a femoral-sided injury to the MPFL in an acute patellar dislocation. Interestingly, traditional surgical treatment for patella instability has been performed adjacent to the patella rather than the femoral origin of the MPFL. These medial reefing procedures may tension the medial retinaculum and possibly the MPFL to the patella but ignore the frequently incompetent femoral attachment. This may prevent true tensioning of the ligament. Further, the bulk and integrity of the retinacular tissues found in the knee with recurrent dislocation or previous surgery are often quite compromised. Conversely, the authors have also seen overtensioning of the entire medial retinacular tissues
Fig 2. Medial view of the right knee. The probe passes under the inferior edge of the MPFL. Note the insertion of the VMO on the superior edge. The large arrowhead represents the medial epicondyle and the smaller arrowhead represents the superficial medial collateral ligament. The medial patelIotibial ligament is reflected anteriorly to show medial patelIomeniscal ligament, and patellar tendon is seen at the far left.
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Fig 3. Arthroscopic view of the MPFL in the right knee as seen from the lateral suprapatellar portal. The instrument is placed in the medial gutter from the inferior medial portal and the patella is at the top.
with a wide lateral release and subsequent medial subluxation or tilt caused by these efforts to prevent lateral dislocation. Both of these problems may contribute to failure of the procedure. Although clinical experience with repair of the MPFL with acute lateral dislocations is limited, it may be a reasonable option. Sallay et al 2° recently reported a series of 16 patients with acute dislocations w h o m they treated with primary repair of the MPFL. They used an incision over the adductor tubercle and either suture anchors or
Fig 4. Axial magnetic resonance image obtained after firsttime lateral patellar dislocation showing injury at the patellar insertion of the medial patellomeniscal ligament. SCHOCK AND BURKS
The authors believe that reconstruction of the MPFL has an important role in the treatment of recurrent lateral dislocation of the patella but not in the treatment of patellofemoral pain caused by patellar-tracking abnormalities. This procedure may be especially useful in the patient with generalized ligamentous laxity in w h o m stretching of a retinacular reefing is likely. The authors' present indications for reconstruction are (1) recurrent lateral patellar dislocation in patients with poor quality medial soft tissues, no definable MPFL and limited bony stability because of trochlear dysplasia, and (2) failure of previous proximal- or proximal and distal-realignment procedures with continued medial laxity. TECHNIQUE Fig 5. Arthroscopic view of the medial gutter of a right knee showing acute MPFL rupture near its femoral attachment. The femur (F) is to the left and hemorrhagic synovium and retinaculum are to the right. The arrow points to torn fibers of the MPFL and the synovial rent.
direct repair to the residual stump to the femur. No redislocations were seen among the 12 patients seen at follow-up of 2 years or more. Recently, Ahmad et a123 recently presented their results with acute repair of the MPFL and VMO in acute patella dislocations. Eight patients were followed a minimum of 11/~years. No recurrent dislocations occurred and patient ratings of athletic activity level and overall satisfaction were 86% and 96%, respectively. The authors' experience in the acute setting has been similarly encouraging. However, in the setting of recurrent dislocation, especially after failed surgery, it is rarely possible to obtain adequate tension or even to identify the MPFL remnant. It is in this situation that reconstruction of the MPFL, possibly in combination with lateral release or distal realignment, may be the best option to regain patellar stability. Several investigators have described medial augmentation procedures for recurrent lateral dislocations. Baker et a124 popularized the tenodesis of Galeazziy and Baski 26 described a transposition of the pes anserinus. Both of these methods use a tibial-based check-rein. Avikainen et a121 proposed an adductor magnus tenodesis to reconstruct or to reinforce the MPFL. They reported good results in 14 patients with mostly primary dislocations at almost 7 years. Gomes 27 reported on a technique for reconstructing the MPFL which uses a polyester substitute. With a mean follow-up of 39 months, he showed reasonably positive results in 30 patients with recurrent dislocations. In a recently published article, Drez et a128presented a series of acute and chronic patellar dislocations managed with a medial patellofemoral ligament reconstruction. The investigators describe their technique of using an autogenous semitendinosis and gracilis tendons or fascia lata graft to reconstruct the MPFL with additional extension of the construct to recreate the medial patellotibial ligament. With a follow-up of greater than 2 years, 93% of their subjects showed good to excellent results with only 1 patient experiencing a recurrence of patellar instability. MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION
A complete examination of the knee under anesthesia is performed first. This can provide important information about the degree of patellar instability as well as help define the range of motion at which the medial restraints are most deficient (Fig 6). A diagnostic arthroscopy is then performed. Additional sources of knee pain or patellar instability, such as articular cartilage damage can be identified and addressed. At this point, any additionally indicated procedure, such as distal realignment may be performed according to the preoperative determination of patellofemoral alignment and limb-rotation profile. 'l-he authors believe it is important to perform these procedures before MPFL reconstruction as they might otherwise alter graft isometry. Most of the authors' patients have already undergone lateral patellar retinacular release and this procedure should not be performed unless it is excessively tight. The majority of the patients requiring MPFL reconstruction have had multiple previous procedures; the location
Fig 6. Examination under anesthetic shows lateral dislocation of a grossly unstable patella. (This is the same patient as shown in Figure 1.)
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Fig 7. Anteromedial view of the right knee showing incision location. (A) Graft harvest incision over pes anserinus. (B) Superiormedial pole of patella (MPFL insertion). (C) Medial femoral epicondyle (MPFL origin)-note the preserved branch of saphenous nerve. (D) The medial joint line arthroscopic portal and an incision are also visible, used to remove painful hardware of a previous distal realignment procedure. A suture has been placed to aid in isometry testing and future graft passage.
and nature of these scars will dictate the surgical approach. Typically, the surgeon uses small incisions to accomplish this reconstruction; however, a single, midline incision may be useful when additional procedures are indicated (Fig 7). There are multiple options for graft material for the MPFL reconstruction. The 2 most familiar sources are the quadriceps tendon and medial hamsrings. A third option is a strip of adductor magnus with intact distal attachment preserved, as described by Avikainen et alY Until recently, the authors have mainly used the quadriceps tendon with a patellar bone block as described b y Burks et al. 29 In an attempt to avoid bone harvest from the proximal patella, an area less forgiving than the more familiar distal pole, a modification of the procedure was developed. Currently, when possible, a single, ipsilateral semitendinosis graft is used. This requires harvest of a hamstring tendon which is familiar to most orthopedic surgeons. Having determined the need for MPFL reconstruction and ruled out any additional intra-articular pathology with arthroscopy, the semitendinosis is harvested. A longitudinal incision is made 5 cm distal to the knee joint, in line with the medial joint line portal. Additional confirmation of incision location is obtained by palpating the pes anserinus on the anterior-medial aspect of the proximal tibia. The dissection is carried down to the level of the sartorious fascia which is split in line with its fibers, allowing the semitendinosis and gracilis tendons to be identified. The dimensions of a looped (double-stranded) semi-
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Fig 8. (A) Medial and (B) anterior views of a left patella. The general area of MPFL insertion is identified for provisional pin placement and graft tunnel creation.
Fig 9. An endobutton (inset) is used to secure the looped semitendinosis in the patellar tunnel. The surgeon will fix this later to the femur with a screw and soft-tissue washer. SCHOCK AND BURKS
Fig 10. Once the patellar and femoral sites have been selected, the surgeon prepares an extrasynovial tunnel for graft passage. The curved arrow shows the prepared femoral bone bed and the open arrow shows the medial collateral ligament. A single, large incision shown to illustrate anatomy. (Reprinted with permission. 2~)
tendinosis graft approximates the dimensions of the MPFL found in normal cadaveric dissections. Standard graft harvest technique is used and the semitendinosis tendon is taken to the back table for further preparation. The semitendinosis graft is cleaned of extraneous soft tissue, whip-
stitched at both ends, and measured to determine tunnel size. The second incision is placed at the superior-medial "corner" of the patella. Because of the mobile nature of the skin in this area, this incision, as well as the third incision may use 2 (or 1) pre-existing incisions up to several centimeters away. A length of 2 cm provides more than adequate exposure. The MPFL insertion is often visible and is a good landmark for tunnel starting point. The overlying soft tissue is sharply removed, exposing bone over a 1-cm wide area. With the arthroscope reintroduced to allow visualization of the undersurface of the patella, the surgeon places a guide pin medial to lateral through the patella in the middle of its anterior-posterior width, starting at the MPFL footprint (Fig 8). Arthroscopic control ensures that the articular surface is not violated by incorrect pin direction. Once the surgeon has determined the appropriate position for the patellar insertion point, the tunnel is now prepared (Fig 9). Using standard endobub ton fixation technique, a drill matching the diameter of the looped semitendinosis graft is introduced over the guidewire. Again, this is performed with arthroscopic visualization of the patella to preclude any chondral injury. The surgeon drills to a depth of one half to two thirds of the width of the patella. This will be a function of patellar width and size of endobutton loops available. The tunnel is completed with the 4.5 m m endobutton drill. The third incision is placed at the medial aspect of medial femoral condyle. The dissection is carried down through the superficial fascia to the midlateral aspect of the medial epicondyle. Cadaveric dissections have shown the MPFL origin to be rather broad. However, the most distinct portion of the ligament has a coalescence of fibers at a point just proximal to the medial collateral ligament. Identification of the medial collateral ligament allows for
Fig 11. Medial views of the right knee showing a graft being passed along the anatomic course of the MPFL and tensioning around the medial epicondylar screw and soft-tissue washer. MEDIAL PATELLOFEMORALLIGAMENT RECONSTRUCTION
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placement of a provisional K-wire which will aid in isometry testing. An extrasynovial tunnel is developed for graft passage. The surgeon uses a clamp or scissors to develop the plane between the joint capsule and the medial patellar retinaculum. This is directed to the MPFL origin and a suture can be placed to aid in graft passage (Fig 10). Isometry of a graft at these proposed origins and insertions can be estimated by passing a length of mersilene tape along the course of the MPFL (between the medial joint capsule and the VMO) with moderate tension and provisional attachment through the patella to the medial condyle K-wire. It is believed that the femoral attachment is more important in isometry and the patella position does not need to be adjusted. The knee is put through a full range of motion. Careful observation is made for any excessive change in graft length or tension. Excessive graft excursion indicates an incorrect MPFL femoral attachment. The femoral attachment should be repositioned to avoid capture of the patella and eventual graft failure. Incorrect K-wire position can be easily adjusted at this stage. Slight tension in extension before the patella engages the trochlear groove can be accepted, however, tension in flexion may lead to medial subluxation of the patella or graft failure. On satisfactory determination of the femoral attachment, a 1-cm square window is made in the soft tissue around the femoral K-wire. Careful elevation of 3 to 5 mm of the anterior edge of the medial collateral ligament is often required. This facilitates an anatomic placement of the graft. The surgeon makes a 3.5 mm unicortical drill hole at this site and a partially threaded 6.5-mm cancellous screw with a soft-tissue washer is partially inserted. The graft is now passed into the patellar tunnel (Fig 11). The surgeon should take care to ensure that surrounding soft tissue is not caught between the endobutton and the patella. With the aid of the previously used mersilene tape, or a tonsil, the surgeon pulls the graft sutures into the medial femoral condyle incision, delivering the 2 graft
Fig 13. Arthroscopic view of a reconstructed MPFL at I year. The view is the same as in Figure 3. Note the similar appearance of a reconstructed ligament to a normal ligament.
arms to the origin fixation site. The authors have found that the standard looped semitendinosis graft is more than long enough to recreate the MPFL. With the knee in 30 ° to 45 ° of flexion, the arms of the graft are provisionally tensioned around the smooth portion of the screw and the knee is put through range of motion (Fig 12). It is critical that the graft not be overtensioned; medial subluxation, tilt, pain, or failure will result from excessive tension. Gentle pressure should cause lateral translation of the patella but no more than 25% of its width. Graft tension should be palpable as this occurs. Range of motion should confirm normal patellar tracking. Once the surgeon has confirmed the optimum combination of patellar stability and knee range of motion, the femoral screw is tightened to secure this graft length. Figure 13 shows an arthroscopic view of a reconstructed MPFL at 1 year. All wounds are irrigated with antibiotic solution and closed. Postoperative care includes 2 to 4 weeks in a knee immobilizer followed by early, protected range of motion. CONCLUSION
Fig 12. The medial view of the left knee with reflected VMO reflected proximally is shown. After securing it to the patella, the graft is passed through an extrasynovial tunnel, deep to the VMO, and provisionally tensioned around the epicondylar screw.
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This procedure reconstructs the primary restraint to lateral patellar translation, the MPFL, with a strong soft-tissue graft. At the authors' institution, experience with this procedure is growing and the early results are encouraging. However, as with all new procedures, caution must be exercised. Although the primary restraint is recreated, not all the contributing factors of lateral patellar instability are addressed; this technique should be used in conjunction with other procedures, as indicated. 3° Despite this, the authors believe that reconstruction of the MPFL is a more logical approach for recurrent patellar dislocation than attempting to tighten poor medial retinacular tissue. This is especially true in the knee with long-standing instability and multiple, failed realignment procedures. It can be a SCHOCK AND BURKS
useful adjunct, as well, with inadequate bony constraints as s e e n i n t r o c h l e a r d y s p l a s i a . T h e h i s t o r y of a n t e r i o r cruciate ligament reconstruction has shown that anatomic l i g a m e n t r e c o n s t r u c t i o n m o r e a c c u r a t e l y a d d r e s s e s t h e ligament deficiency than other extra-articular techniques. T h i s s a m e r e a s o n i n g is t h e b a s i s of t h i s t e c h n i q u e of M P F L reconstruction. At the authors' institution, the preference is to r e c o n s t r u c t t h e d e f i c i e n t p r i m a r y r e s t r a i n t to l a t e r a l p a t e l l a r d i s l o c a t i o n r a t h e r t h a n n o n a n a t o m i c r e e f i n g of stretched and frequently inadequate medial tissues.
REFERENCES 1. Cofield R, Bryan R: Acute dislocation of the patella: ResuIts of conservative treatment. J Trauma 17:526-531, 1977 2. Hawkins R, Bell R, Garth A: Acute patellar dislocations: The natural history. Am J Sports Med 14:117-120, 1986 3. Larsen E, Lauridsen F: Conservative treatment of pateltar dislocations: Influence of evident factors on the tendency to redislocation and the therapeudic result. Clin Orthop 171:131-136, 1982 4. Macnab h Recurrent dislocation of the patella. J Bone Joint Surg Am 34:957-967, 1953 5. Maenpaa H, Lehto MUK: Patellar dislocation: The long-term results of non-operative management in 100 patients. Am J Sports Med 25:213-217, 1997 6. McManus F, Rang M, Heslin D: Acute dislocation of the patella in children: The natural history. Clin Orthop 139:88-91, 1979 7. Cash J, Hughston J: Treatment of acute patellar dislocation. Am J Sports Med 16:244-249, 1988 8. Sargent J, Teipner W: Medial patellar retinacular repair for acute and recurrent dislocation of the patella: A preliminary report. J Bone Joint Surg Am 53:386, 197t 9. Vainionpaa S, Laasonen E, Silvennoinen T: Acute dislocation of the patella: A prospective review of operative treatment. J Bone Joint Surg Br 72:366-369, 1990 10. Arnbjornsson A, Egund N, Rydting O, et ah The natural history of recurrent dislocations of the patella. J Bone Joint Surg Br 74:140-142,1992 11. Crosby E, Insall J: Recurrent dislocation of the patella: Relation of treatment to osteoarthritis. J Bone Joint Surg Am 58:9-13, 1976 12. Harilainen R, Sandelin J: Prospective long-term results of operative treatment in primary dislocation of the patella. Knee Surg Sports Traumatol Arthrosc 1:100-103, 1993
MEDIAL PATELLOFEMORALLIGAMENT RECONSTRUCTION
13. Feller J, Feagin J, Garrett W: The MPFL revisited: An anatomical study. Knee Surg Sports Traumatol Athrosc 1:184-186, 1993 14. Reider B, Marshall J, Koslin B, et al: The anterior aspect of the knee joint: An anatomical study. J Bone Joint Surg Am 63:351-356, 1981 15. Warren R, Marshall J: The supporting structures and layers of the medial side of the knee: An anatomical analysis. J Bone Joint Surg Am 61:56-62, 1979 16. Burks R, Desio S, Bachus K, et ah Biomechanical evaluation of lateral patellar dislocations. Am J Knee Surg 11:24-31, 1998 17. Conlan T, Garth W, Lemons J: Evaluation of the medial soft tissue restraints of the extensor mechanism of the knee. J Bone Joint Surg Am 75:682-693, 1993 18. Desio S, Burks R, Bachus K: Soft tissue restraints to lateral patellar translation. Am J Sports Med 26:59-65, 1998 19. Sandmeier R, Burks R, Bachus K, et ah The effect of reconstruction of the medial patellofemoral ligament on patellar tracking. Am J Sports Med 28:345-349, 2000 20. Sallay P, Poggi J, Speer K, et al: Acute dislocation of the patella: A correlative pathoanatomical study. Am J Sports Med 24:52-60, 1996 21. Avikainen V, Nikku R, Seppannen-Lehmonen T: Adductor magnus tenodesis for patellar dislocation. Clin Orthop 297:12-16, 1993 22. Yamamoto R: Arthroscopic repair of the medial retinacuhim and capsule in acute patellar dislocations. Arthroscopy 2:125-131, 1986 23. Ahmad C, Shuben B, Matuz D, et ah Immediate surgical repair of the medial patellar stabilizes for acute patellar dislocations. Am J Sports Med 28:804-810, 2000 24. Baker R, Carroll N, Dewar F, et ah The semitendinosis tenodesis for recurrent dislocation of the patella. J Bone Joint Surg Br 54:103-109, 1972 25. Galeazzi R: Nouve applicazioni deI trapianto muscu!are e tendineo. Arch Orthop 38:4-7, 1922 26. Baski D: Pes anserinus transposition for patellar dislocations. J Bone Joint Surg Br 75:305-310, 1993 27. Gomes J: Medial patellofemoral ligament reconstruction for recurrent dislocation of the patella: A preliminary report. J Arthrosc 8:335-340, 1992 28. Drez D Jr, Edwards B, Williams C: Results of medial patellofemoral ligament reconstruction in the treatment of patellar dislocation. Arthroscopy 17:298-306, 2001 29. Burks R, Luker M: Medial patellofemoral ligament reconstruction. Tech Ortho 12:185-191, 1997 30. Fulkerson J, Shea K: Disorders of patellofemoral alligmnent. J Bone Joint Surg Am 72:1424-1429, 1990
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Recurrent lateral dislocation of the patella has been historically treated with a combination of multiple techniques including lateral release, proximal realignment, medial reefing, and distal realignment. Poor-quality medial retinacular tissues and nonanatomic surgical attempts to restrain the patella may contribute to notable problems with redislocation and anterior knee pain. Recent biomechanical studies have identified the functional importance of the medial patellofemoral ligament as the primary restraint to lateral translation of the patella. A technique of reconstruction of this ligament with a single semitendinosis autograft, which provides a sturdy check-rein to lateral translation, is described. The authors' current indications for this procedure are (1) the recurrent lateral patellar dislocations in a patient with poor-quality medial soft tissues and no definable MPFL, and (2) the failure of previous proximal or proximal and distal realignment procedures with continued medial functional deficiency. KEY WORDS: medial patellofemoral ligament, patellar dislocation, autograft tendon Copyright © 2001 by W.B. Saunders Company
Recurrent lateral dislocation of the patella remains a challenging problem for the orthopedic surgeon because of many complex contributing factors such as generalized ligamentous laxity, inadequate medial retinacular tissue, insufficient trochlear groove restraint (Fig 1), patellar tendon length abnormalities, limb-alignment torsional abnormalities, and others. Nonoperative treatment of primary patellar dislocations has reported redislocation rates of 15% to 440/o.1-6 Management of these recurrent dislocations often includes lateral release with proximal a n d / o r distal realignment. Although short-term results of operative management have been good, 7-9 recurrent dislocations have been reported in up to 21% of patients evaluated with longer follow-up. 1°-12 In addition to recurrence of patellar instability, several investigators have reported postoperative problems with anterior knee pain, medial dislocation, chondral damage, and chronic effusions. 7-9,1°,12It is reasonable to presume that some of these failures are related to the complexity of variable injuries to the stabilizing structures. Articular damage may have been incurred before surgical management, as well. The medial extensor mechanism has been described by numerous investigators 13-1s however, it is only recently that the significance of the medial patellofemoral ligament has been widely appreciated. 14,16-1s Conlan et a117 performed a serial-sectioning study of the medial soft tissues of cadavers and found that the medial patellofemoral ligament (MPFL) contributed an average of 53% of the total
From the University of Utah Department of Orthopaedic Surgery, Salt Lake City, UT. Address reprintrequests to Ethan J. Schock, MD, 50 North Medical Dr, Salt Lake City, UT 84132. Copyright © 2001 by W.B. Saunders Company 1060-1872/01/0903-0010535.00/0 doi:l 0.1053/otsm.2001.25235
restraining force to lateral displacement of the patella. The authors' studies of the anatomic and biomechanical properties of the MPFL have shown similar results: the MPFL provides the primary restraint to lateral patellar displacement at 20 ° of flexion, contributing 60% of the total restraining force. Is A further study has shown that changes in patellar tracking in the medial soft-tissue-deficient knee with a laterally directed force can be significantly reversed by reconstructing the MPFL. 19 An understanding of the anatomy of the medial side of the knee is important when evaluating the medial patellar stabilizers. The femoral origin of the MPFL is located in layer 2 of the medial knee. It begins with an arc of fibers continuous with the anterior edge of the superficial medial collateral ligament near the medial epicondyle with other fibers originating from the adductor tubercle or medial epicondyle or both, with individual variation. The MPFL inserts on the proximal medial edge of the patella. The vastus medialis obliquus (VMO) inserts on the ligament over a variable distance near the patellar insertion. Figure 2 is taken from a cadaveric dissection, and Figure 3 is an arthroscopic view of the MPFL after synovectomy for an unrelated problem. Conlan et a117found the MPFL to be a distinct ligament in 29 of 33 cadaveric specimens. However in cases of chronic instability, with scar tissue obscuring attenuated tissue planes, it can be difficult or impossible to identify the ligament. An understanding of the precise site at which the MPFL fails should enhance the ability to treat related patellar instability. However, there is debate over exactly where these tears occur. Sallay et al 2° and Avikainen et a121 evaluated patients with acute patellar dislocations and found tears of the retinaculum from the femur in almost all patients. Sargent and Telpher 8 noted tears from the patella in all patients. Yamamoto 22 found a distinct medial capsular tear in all of his patella dislocation patients, but none
Operative Techniques in Sports Medicine, Vol 9, No 3 (July), 2001: pp 169-175
1 69
Fig 1. Merchant view of a 17-year-old female patient with recurrent lateral patellar dislocation. Note the shallow trochlea.
directly from the femur. The authors' laboratory results and clinical experience suggest that the MPFL is most often injured on the femoral side but can be torn in its midsubstance. ~6 The authors have noted injury adjacent to the patella but attribute this to the avulsion of the medial patellomeniscal ligament (Fig 4). They have found no failures of the MPFL patellar insertion. Figure 5 is an arthroscopic view of the medial gutter showing a femoral-sided injury to the MPFL in an acute patellar dislocation. Interestingly, traditional surgical treatment for patella instability has been performed adjacent to the patella rather than the femoral origin of the MPFL. These medial reefing procedures may tension the medial retinaculum and possibly the MPFL to the patella but ignore the frequently incompetent femoral attachment. This may prevent true tensioning of the ligament. Further, the bulk and integrity of the retinacular tissues found in the knee with recurrent dislocation or previous surgery are often quite compromised. Conversely, the authors have also seen overtensioning of the entire medial retinacular tissues
Fig 2. Medial view of the right knee. The probe passes under the inferior edge of the MPFL. Note the insertion of the VMO on the superior edge. The large arrowhead represents the medial epicondyle and the smaller arrowhead represents the superficial medial collateral ligament. The medial patelIotibial ligament is reflected anteriorly to show medial patelIomeniscal ligament, and patellar tendon is seen at the far left.
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Fig 3. Arthroscopic view of the MPFL in the right knee as seen from the lateral suprapatellar portal. The instrument is placed in the medial gutter from the inferior medial portal and the patella is at the top.
with a wide lateral release and subsequent medial subluxation or tilt caused by these efforts to prevent lateral dislocation. Both of these problems may contribute to failure of the procedure. Although clinical experience with repair of the MPFL with acute lateral dislocations is limited, it may be a reasonable option. Sallay et al 2° recently reported a series of 16 patients with acute dislocations w h o m they treated with primary repair of the MPFL. They used an incision over the adductor tubercle and either suture anchors or
Fig 4. Axial magnetic resonance image obtained after firsttime lateral patellar dislocation showing injury at the patellar insertion of the medial patellomeniscal ligament. SCHOCK AND BURKS
The authors believe that reconstruction of the MPFL has an important role in the treatment of recurrent lateral dislocation of the patella but not in the treatment of patellofemoral pain caused by patellar-tracking abnormalities. This procedure may be especially useful in the patient with generalized ligamentous laxity in w h o m stretching of a retinacular reefing is likely. The authors' present indications for reconstruction are (1) recurrent lateral patellar dislocation in patients with poor quality medial soft tissues, no definable MPFL and limited bony stability because of trochlear dysplasia, and (2) failure of previous proximal- or proximal and distal-realignment procedures with continued medial laxity. TECHNIQUE Fig 5. Arthroscopic view of the medial gutter of a right knee showing acute MPFL rupture near its femoral attachment. The femur (F) is to the left and hemorrhagic synovium and retinaculum are to the right. The arrow points to torn fibers of the MPFL and the synovial rent.
direct repair to the residual stump to the femur. No redislocations were seen among the 12 patients seen at follow-up of 2 years or more. Recently, Ahmad et a123 recently presented their results with acute repair of the MPFL and VMO in acute patella dislocations. Eight patients were followed a minimum of 11/~years. No recurrent dislocations occurred and patient ratings of athletic activity level and overall satisfaction were 86% and 96%, respectively. The authors' experience in the acute setting has been similarly encouraging. However, in the setting of recurrent dislocation, especially after failed surgery, it is rarely possible to obtain adequate tension or even to identify the MPFL remnant. It is in this situation that reconstruction of the MPFL, possibly in combination with lateral release or distal realignment, may be the best option to regain patellar stability. Several investigators have described medial augmentation procedures for recurrent lateral dislocations. Baker et a124 popularized the tenodesis of Galeazziy and Baski 26 described a transposition of the pes anserinus. Both of these methods use a tibial-based check-rein. Avikainen et a121 proposed an adductor magnus tenodesis to reconstruct or to reinforce the MPFL. They reported good results in 14 patients with mostly primary dislocations at almost 7 years. Gomes 27 reported on a technique for reconstructing the MPFL which uses a polyester substitute. With a mean follow-up of 39 months, he showed reasonably positive results in 30 patients with recurrent dislocations. In a recently published article, Drez et a128presented a series of acute and chronic patellar dislocations managed with a medial patellofemoral ligament reconstruction. The investigators describe their technique of using an autogenous semitendinosis and gracilis tendons or fascia lata graft to reconstruct the MPFL with additional extension of the construct to recreate the medial patellotibial ligament. With a follow-up of greater than 2 years, 93% of their subjects showed good to excellent results with only 1 patient experiencing a recurrence of patellar instability. MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION
A complete examination of the knee under anesthesia is performed first. This can provide important information about the degree of patellar instability as well as help define the range of motion at which the medial restraints are most deficient (Fig 6). A diagnostic arthroscopy is then performed. Additional sources of knee pain or patellar instability, such as articular cartilage damage can be identified and addressed. At this point, any additionally indicated procedure, such as distal realignment may be performed according to the preoperative determination of patellofemoral alignment and limb-rotation profile. 'l-he authors believe it is important to perform these procedures before MPFL reconstruction as they might otherwise alter graft isometry. Most of the authors' patients have already undergone lateral patellar retinacular release and this procedure should not be performed unless it is excessively tight. The majority of the patients requiring MPFL reconstruction have had multiple previous procedures; the location
Fig 6. Examination under anesthetic shows lateral dislocation of a grossly unstable patella. (This is the same patient as shown in Figure 1.)
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Fig 7. Anteromedial view of the right knee showing incision location. (A) Graft harvest incision over pes anserinus. (B) Superiormedial pole of patella (MPFL insertion). (C) Medial femoral epicondyle (MPFL origin)-note the preserved branch of saphenous nerve. (D) The medial joint line arthroscopic portal and an incision are also visible, used to remove painful hardware of a previous distal realignment procedure. A suture has been placed to aid in isometry testing and future graft passage.
and nature of these scars will dictate the surgical approach. Typically, the surgeon uses small incisions to accomplish this reconstruction; however, a single, midline incision may be useful when additional procedures are indicated (Fig 7). There are multiple options for graft material for the MPFL reconstruction. The 2 most familiar sources are the quadriceps tendon and medial hamsrings. A third option is a strip of adductor magnus with intact distal attachment preserved, as described by Avikainen et alY Until recently, the authors have mainly used the quadriceps tendon with a patellar bone block as described b y Burks et al. 29 In an attempt to avoid bone harvest from the proximal patella, an area less forgiving than the more familiar distal pole, a modification of the procedure was developed. Currently, when possible, a single, ipsilateral semitendinosis graft is used. This requires harvest of a hamstring tendon which is familiar to most orthopedic surgeons. Having determined the need for MPFL reconstruction and ruled out any additional intra-articular pathology with arthroscopy, the semitendinosis is harvested. A longitudinal incision is made 5 cm distal to the knee joint, in line with the medial joint line portal. Additional confirmation of incision location is obtained by palpating the pes anserinus on the anterior-medial aspect of the proximal tibia. The dissection is carried down to the level of the sartorious fascia which is split in line with its fibers, allowing the semitendinosis and gracilis tendons to be identified. The dimensions of a looped (double-stranded) semi-
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Fig 8. (A) Medial and (B) anterior views of a left patella. The general area of MPFL insertion is identified for provisional pin placement and graft tunnel creation.
Fig 9. An endobutton (inset) is used to secure the looped semitendinosis in the patellar tunnel. The surgeon will fix this later to the femur with a screw and soft-tissue washer. SCHOCK AND BURKS
Fig 10. Once the patellar and femoral sites have been selected, the surgeon prepares an extrasynovial tunnel for graft passage. The curved arrow shows the prepared femoral bone bed and the open arrow shows the medial collateral ligament. A single, large incision shown to illustrate anatomy. (Reprinted with permission. 2~)
tendinosis graft approximates the dimensions of the MPFL found in normal cadaveric dissections. Standard graft harvest technique is used and the semitendinosis tendon is taken to the back table for further preparation. The semitendinosis graft is cleaned of extraneous soft tissue, whip-
stitched at both ends, and measured to determine tunnel size. The second incision is placed at the superior-medial "corner" of the patella. Because of the mobile nature of the skin in this area, this incision, as well as the third incision may use 2 (or 1) pre-existing incisions up to several centimeters away. A length of 2 cm provides more than adequate exposure. The MPFL insertion is often visible and is a good landmark for tunnel starting point. The overlying soft tissue is sharply removed, exposing bone over a 1-cm wide area. With the arthroscope reintroduced to allow visualization of the undersurface of the patella, the surgeon places a guide pin medial to lateral through the patella in the middle of its anterior-posterior width, starting at the MPFL footprint (Fig 8). Arthroscopic control ensures that the articular surface is not violated by incorrect pin direction. Once the surgeon has determined the appropriate position for the patellar insertion point, the tunnel is now prepared (Fig 9). Using standard endobub ton fixation technique, a drill matching the diameter of the looped semitendinosis graft is introduced over the guidewire. Again, this is performed with arthroscopic visualization of the patella to preclude any chondral injury. The surgeon drills to a depth of one half to two thirds of the width of the patella. This will be a function of patellar width and size of endobutton loops available. The tunnel is completed with the 4.5 m m endobutton drill. The third incision is placed at the medial aspect of medial femoral condyle. The dissection is carried down through the superficial fascia to the midlateral aspect of the medial epicondyle. Cadaveric dissections have shown the MPFL origin to be rather broad. However, the most distinct portion of the ligament has a coalescence of fibers at a point just proximal to the medial collateral ligament. Identification of the medial collateral ligament allows for
Fig 11. Medial views of the right knee showing a graft being passed along the anatomic course of the MPFL and tensioning around the medial epicondylar screw and soft-tissue washer. MEDIAL PATELLOFEMORALLIGAMENT RECONSTRUCTION
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placement of a provisional K-wire which will aid in isometry testing. An extrasynovial tunnel is developed for graft passage. The surgeon uses a clamp or scissors to develop the plane between the joint capsule and the medial patellar retinaculum. This is directed to the MPFL origin and a suture can be placed to aid in graft passage (Fig 10). Isometry of a graft at these proposed origins and insertions can be estimated by passing a length of mersilene tape along the course of the MPFL (between the medial joint capsule and the VMO) with moderate tension and provisional attachment through the patella to the medial condyle K-wire. It is believed that the femoral attachment is more important in isometry and the patella position does not need to be adjusted. The knee is put through a full range of motion. Careful observation is made for any excessive change in graft length or tension. Excessive graft excursion indicates an incorrect MPFL femoral attachment. The femoral attachment should be repositioned to avoid capture of the patella and eventual graft failure. Incorrect K-wire position can be easily adjusted at this stage. Slight tension in extension before the patella engages the trochlear groove can be accepted, however, tension in flexion may lead to medial subluxation of the patella or graft failure. On satisfactory determination of the femoral attachment, a 1-cm square window is made in the soft tissue around the femoral K-wire. Careful elevation of 3 to 5 mm of the anterior edge of the medial collateral ligament is often required. This facilitates an anatomic placement of the graft. The surgeon makes a 3.5 mm unicortical drill hole at this site and a partially threaded 6.5-mm cancellous screw with a soft-tissue washer is partially inserted. The graft is now passed into the patellar tunnel (Fig 11). The surgeon should take care to ensure that surrounding soft tissue is not caught between the endobutton and the patella. With the aid of the previously used mersilene tape, or a tonsil, the surgeon pulls the graft sutures into the medial femoral condyle incision, delivering the 2 graft
Fig 13. Arthroscopic view of a reconstructed MPFL at I year. The view is the same as in Figure 3. Note the similar appearance of a reconstructed ligament to a normal ligament.
arms to the origin fixation site. The authors have found that the standard looped semitendinosis graft is more than long enough to recreate the MPFL. With the knee in 30 ° to 45 ° of flexion, the arms of the graft are provisionally tensioned around the smooth portion of the screw and the knee is put through range of motion (Fig 12). It is critical that the graft not be overtensioned; medial subluxation, tilt, pain, or failure will result from excessive tension. Gentle pressure should cause lateral translation of the patella but no more than 25% of its width. Graft tension should be palpable as this occurs. Range of motion should confirm normal patellar tracking. Once the surgeon has confirmed the optimum combination of patellar stability and knee range of motion, the femoral screw is tightened to secure this graft length. Figure 13 shows an arthroscopic view of a reconstructed MPFL at 1 year. All wounds are irrigated with antibiotic solution and closed. Postoperative care includes 2 to 4 weeks in a knee immobilizer followed by early, protected range of motion. CONCLUSION
Fig 12. The medial view of the left knee with reflected VMO reflected proximally is shown. After securing it to the patella, the graft is passed through an extrasynovial tunnel, deep to the VMO, and provisionally tensioned around the epicondylar screw.
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This procedure reconstructs the primary restraint to lateral patellar translation, the MPFL, with a strong soft-tissue graft. At the authors' institution, experience with this procedure is growing and the early results are encouraging. However, as with all new procedures, caution must be exercised. Although the primary restraint is recreated, not all the contributing factors of lateral patellar instability are addressed; this technique should be used in conjunction with other procedures, as indicated. 3° Despite this, the authors believe that reconstruction of the MPFL is a more logical approach for recurrent patellar dislocation than attempting to tighten poor medial retinacular tissue. This is especially true in the knee with long-standing instability and multiple, failed realignment procedures. It can be a SCHOCK AND BURKS
useful adjunct, as well, with inadequate bony constraints as s e e n i n t r o c h l e a r d y s p l a s i a . T h e h i s t o r y of a n t e r i o r cruciate ligament reconstruction has shown that anatomic l i g a m e n t r e c o n s t r u c t i o n m o r e a c c u r a t e l y a d d r e s s e s t h e ligament deficiency than other extra-articular techniques. T h i s s a m e r e a s o n i n g is t h e b a s i s of t h i s t e c h n i q u e of M P F L reconstruction. At the authors' institution, the preference is to r e c o n s t r u c t t h e d e f i c i e n t p r i m a r y r e s t r a i n t to l a t e r a l p a t e l l a r d i s l o c a t i o n r a t h e r t h a n n o n a n a t o m i c r e e f i n g of stretched and frequently inadequate medial tissues.
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MEDIAL PATELLOFEMORALLIGAMENT RECONSTRUCTION
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