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Hamstring anterior cruciate ligament reconstruction using femoral cross pin fixation
HAMSTRING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION USING FEMORAL CROSS-PIN FIXATION EUGENE M. WOLF, MD
Surgical reconstruction of the anterior cruciate ligament (ACL) with bone-patella tendon-bone (BPTB) graft has become the most commonly performed procedure for the unstable cruciate-deficient knee. The use of BPTB has been complicated by chronic anterior knee pain, loss of extension, patella tendon rupture, and patella fractures. The TransFix technique uses a double-looped semitendinosis and gracilis (DLSG) graft that is stronger than BPTB, and has less graft site and operative morbidity. This technique uses cross-pin femoral fixation and tibial interference screw fixation in the tibia that allows immediate weight bearing and an aggressive rehabilitation program. Results are equal to those previously reported for BPTB. KEY WORDS: double looped semitendinosis and gracilis, femoral cross-pin, tibial Bioscrew fixation
The evolution of more demanding and active lifestyles of our population combined with the technical advances of arthroscopic surgical techniques has made the surgical reconstruction of the anterior cruciate ligament (ACL) the standard of care in the treatment of the unstable ACLdeficient knee3 Arthroscopic-assisted bone-patella tendonbone (BPTB) autograft has become the most commonly used procedure in ACL reconstruction. Although this approach that has become the gold standard in ACL reconstruction, complications and problems have been reported2-4: Patella chondromalacia with chronic anterior knee pain Decreased range of motion with loss of extension Patella baja from patella ligament contracture Intraoperative or postoperative fractures of the patella Patella tendon ruptures Severed graft on femoral interference screw insertion The use of allograffs has solved some of these problems, but allograffs present significant cost and availability issues. The use of hamstrings (tripled or quadrupled semitendinosis or double-looped semitendinosis and gracilis [DLSG]) has gained popularity in recent years. A recent although informal survey of registrants at the annual meeting of the Arthroscopy Association of North America suggested that approximately 30% of the surgeons surveyed were using hamstring techniques. Whether or not an ACL reconstruction can restore stability and function in the unstable and ACL-deficient knee is no longer an issue. The issues at hand are which is the best graft and which is the best technique to use. The ideal technique should incorporate the following features:
From the Department of Orthopedic Surgery, California Pacific Medical Center, San Francisco, CA. Address reprint requests to Eugene M. Wolf, MD, 3000 California Street, San Francisco, CA 94115. Copyright © 1999 by W.B. Saunders Company 1060-1872/99/0704-0007510.00/0
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Restore the normal kinematics of the knee. Produce the least amount of operative morbidity possible. Have the strongest fixation possible. Use the strongest graft possible. Use a graft of optimal stiffness. Permit immediate weight bearing and an early rehabilitation program. Allow the most rapid return to the patient's preinjury level. Produce the least impact on daffy and professional activities. Facilitate revision of failed prior procedures. Be useful with open epiphyses. There are some recent comparative studies using BPTB and semitendinosis and gracils (STG) grafts. Marder et al s reviewed 80 patients. He found no significant differences in subjective results, KT-1000, or functional levels. O'Neill 6 compared the results in 125 patients. All patients were started immediately on an aggressive rehabilitation program. Analysis of functional outcome and return to sports at 42 months postoperatively showed no differences between arthroscopic BPTB and STG, with 89% and "88% returning to their preinjury level. The KT-1000 results showed no significant differences between the two groups. Pinczewski et al 7 recently presented a 2-year prospective study of 90 patients in each group of BPTB and quadrupled semitendinosus graft (HT) fixated with metal interference screws. There was no difference in the clinical examinations of both groups. There was no significant statistical difference in International Knee Data Collection (IKDC) assessments or abilities to return to prior athletic activities, but arthrometry showed that only 74% of HT versus 90% of BPTB had side-to-side differences of 3 mm or less. When compared with BPTB, the graft site morbidity of STG grafts has proven to be negligible. Yasuda et al 8 showed in 65 patients that donor site soreness resolved completely at 3 months, and that the hamstring muscle strength had returned to normal at 9 months. Lipscomb et al 9 evaluated 51 patients for hamstring and quadriceps strength at 26.2 months postoperatively. Hamstring strength
Operative Techniques in Sports Medicine, Vol 7, No 4 (October), 1999: pp 214-222
was found to be at 99% and quadriceps at 96% when compared by isokinetic testing. In the previously cited study by Pinczewski et al, there was significantly less thigh atrophy in the hamstring group, although the difference disappeared after 2 years. At 2 years postoperatively, 33% of the BPTB group as opposed to 7% of the HT group experienced anterior knee pain. Which is the strongest, stiffest graft, BPTB or doublelooped semitendinosus and gracilis (DLSTG)? The best w a y to restore the normal kinematics of the knee is to construct a strong and isometric graft. Present data indicate that the double-looped semitendinosus and gracilis tendons composite is the stronger and stiffer graft when compared with the 10-mm BPTB graft¢ °-n The DLSTG has a cross-sectional diameter and stiffness that resembles the normal ACL more than the 10-mm BPTB graft. The 10-mm BPTB graft is 125% of the normal ACL, whereas the DLSTG is 249% of the normal ACL. With a stronger graft, the technique used to fixate the DLSTG must provide strong enough fixation over a sufficient period of time to allow early weight bearing and rapid return to normal daily activities. H o w long does it take to obtain adequate biological
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Fig 2. The fibers of the conjoined insertion of the semitendinosus and gracilis tendons are sectioned with scissors. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.) Gracilis
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Fig 1. A 4- to 5-cm incision is made over the insertion of the pes tendons, and the subcutaneous tissues are undermined to gain access to the tendons and the tibial tunnel site. The incision is carried down through the periosteum of the tunnel site and through the pes tendons down to bone. The entire pes is reflected off the tibia. The gracilis and semitendinosus tendons are easily identified on the undersurface. They are dissected from the sartorial fascia with a curved clamp and are sectioned with a knife, cutting down on the clamp. This will leave a firm edge of conjoined tendon left to repair to the stump on the tibia when closing, yet still provide more than enough graft to work with. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.) FEMORAL CROSS-PIN FIXATION ACL RECONSTRUCTION
healing of tendons in bone tunnels? Grana et aU3 showed in the rabbit model that collagenous and bony ingrowth exceeds the strength of the tendon graft at 3 weeks. The results showed that by 3 weeks, failure of the construct occurred at the intra-articular portion of the graft and not by pull-out of the tendon from the tunnels. Rodeo et aU4 studied tendon healing in bone tunnels in dogs. The dogs were killed at 2-, 4-, 8-, 12-, and 26-week intervals. At 2, 4, and 8 weeks, pull-out occurred from the tunnels. At 12 and 26 weeks, the tendon failed by pull-out of the tendon from the test clamp or by midsubstance rupture. They concluded that STG grafts should be protected for at least 8 weeks. This was a study that transplanted the long digital extensor tendon through a 4.5-mm drill hole in the proximal tibia and had no intra-articular component. At 4 weeks the average pull-out strength was already 274 N, and increased to 295 N and 357 N at 8 and 12 weeks, respectively. The pull-out loads were roughly proportional to tunnel lengths, and those tunnels lengths were as short as 9 mm. If one could extrapolate these data and correlate them to the size of STG grafts and tunnels in the human model, one would expect pull-out strengths far in excess of that necessary for the most aggressive rehabilitation program. 215
TRANSFIX TECHNIQUE The femoral fixation is obtained with a cannulated crosspin, 3 m m in diameter, with a specially designed, 7-mm-wide head that is impacted into the lateral femoral cortex. The initial design of the cross pin (SemiFix, Arthrex, Naples, FL) incorporated a 7-mm-wide threaded head that
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Fig 3. It is important to identify the tendinous expansions to the gastrocnemius of the gracilis, and in particular the semitendinosus tendon, and cut them before stripping them. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.)
Radiographic enlargement of bone tunnels has been reported after ACL reconstruction using BPTB autografts 15 and BPTB allografts. 16Although this has not been correlated with poor outcomes, the apparent enlargement on radiographs of a tunnel within which a graft is supposed to be incorporated does raise some concerns. It was thought that the enlargement was caused by the ethylene oxide sterilization of allografts. 17 UInsalata et a115compared ~mnel expansion after BPTB and hamstrings autografts. There was a considerable increase in ~nnel width in the hamstring group, most notably on the tibial side (30.2%) when compared with the BPTB group (9.7%). There was no enlargement of tunnels on the femoral side when BPTB was used. They concluded that the points of graft fixation were the determining factors in the degree of tunnel enlargement, and that micromotion of the grafts in the tunnels produces the enlargement. The hamstrings were fixated outside of the tunnels with cortical devices and Mersilene (Ethicon Inc., Somerville, NJ) tape, thereby creating longer grafts that were susceptible to graft strain within the tunnels. Thus a shorter graft with rigid fixation within the tunnels not dependent on suture or Mersilene tape would be optimal. 216
Fig 4. Depending on the size of the tendons, a 5- or 7-mm tendon stripper is used to free them from their muscular origins. It is petter to use the 5-mm stripper if possible because it will strip the tendons more cleanly. The bulbous distal end of the tendon may be trimmed back to facilitate the use of the smaller stripper. An arthroscopic grasper is used to pull the tendon through the tip of the tendon stripper. When through the end of the stripper, the tendon end is grasped with a Mayo clamp toward the base of the clamp's jaws. The tendon is then wound around the clamp. This allows good tension to be placed on the tendon while the stripper is pushed proximally, stripping the muscle at the musculotendinous junction. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.) EUGENE M. WOLF
was screwed into the lateral femoral cortex. There were technical difficulties encountered with this screw design. The grafts could be w o u n d up as if on a winch when the screw/implant was turned in the femur. There were difficulties advancing the screw-like device as the head encountered the oblique metaphyseal surface of the lateral femoral cortex. The TransFix implant (Arthrex Corporation, Naples, FL) can now be impacted into the femur with a mallet. Impacting the implant avoids the above-cited problem, and the implant is designed to act as a staple on impaction and as a screw on removal. The head of the implant still has a threaded configuration that allows its removal with a hex-head screwdriver, should it ever be deemed necessary. The TransFix implant is passed over a flexible nitenol wire that is used to pull the grafts into snug tunnels in the tibia and femur. The TransFix technique places the femoral implant at 90 ° to the graft as it passes under the DLSTG. The ultimate load (4,113 N) and stiffness (689 N) of cross-pin fixation far exceeds that of any other type of fixation of a graft in the femur. 18 A biodegradable screw, the Bioscrew (Arthrex Corporation, Naples, FL), provides the tibial fixation. Weiler showed using h u m a n cadaver semitendinosus tendons and bovine proximal tibias that a biodegradable screw had higher pull-out strength than a titanium screw (Weiler A, unpublished data). He hypothesized that the stiffness gradient between the polymeric screw and the bone was lower than that of the titanium interface, resulting in better transmission of the shear forces. The surface texture of the Bioscrew
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provided a better grip on the tendon surfaces. A 9-mm × 28-mm screw is used in an 8 mm tunnel, and a 10 × 28 m m screw in a 9-ram tunnel is recommended in this technique. The Bioscrew is 28 m m long, and is inserted into the tibia along the sutured section of the graft into the tibia until it reaches the cortical surface of the intercondylar area. An additional security point of fixation can be afforded by creating a bony bridge distal to the tibial tunnel. The 3-mm transfemoral pin can be used to create a drill hole 1 cm distal to the tunnel A currette is used to open a space behind the cortex to allow passage of half the sutures. In this case, the grafts must be prepared so they do not exceed 20 cm in length, to ensure that they will not extend beyond the tibial tunnel opening. Sutures at one end of the grafts are shorter so they can be identified and properly tied over the bony bridge. There is a new Bio-Interference screw, 17 m m in length, designed to enhance the tibial fixation by capturing the graft at the cortical opening of the tibial tunnel (Arthrex, Naples, FL). The fixation afforded by the TransFix system allows the patients to immediately bear weight and to begin an exercise program as soon as tolerated.
MATERIALS AND METHODS This technique has undergone a considerable degree of evolution since its original clinical use in 1994. The original technique called for dragging the tendons up through the tunnels using a fork-like device. This necessitated larger
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Fig 5. The marking hook that is firmly mounted on the femoral guide is inserted up through the tibial tunnel and up into the femoral tunnel to a depth of 25 to 30 mm as indicated by the laser markings on the hook. The pin sleeve is advanced to contact the skin, and the sharp trocartipped 3-mm guide pin is pushed through the skin to contact bone. It is drilled through the distal femur in a direction that is slightly posterolateral to anteromedial to the coronal plane. The pin will pass through the opening in the marking hook, out the lateral cortex, and exit the skin anterior to the midcoronal plane. This will avoid any risk to the saphenous vein or nerve. (Arthrex, Naples, FL). (Reprinted with permission from Arthrex, Naples, FL.)
FEMORAL CROSS-PIN FIXATION ACL RECONSTRUCTION
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tunnels than are now used in the TransFix technique, to accommodate the concomitant insertion of the tendons and the fork-like marking hook. The adoption of a modified marking hook and a nitenol wire has permitted the use of tunnels that are based on the measured width of the grafts. This affords a snug fit in the tunnels and excellent contact at the tendon-bone interface to avoid any windshield-wiper-like motion of the grafts. The tibial tunnel should be reamed 1 m m larger than the femoral tunnel to accommodate the extra bulk of the tendon ends and sutures. The grafts are measured in the graft-measuring block with the notion of different tunnel sizes for the tibia and femur. The proximal or femoral end of the graft will always be smaller than the tibial side. The DLSG tendon graft should be sized at each end to determine the appropriate tunnel size. The most common tunnel size configuration is an 8-mm femoral tunnel and a 9-mm tibial tunnel. The SemiFix screw has been replaced by the 3-mm Trans-
Fix implant. This pin is available in both 40- and 50-mm lengths. The 28-mm headless resorbable screw has replaced the double-staple fixation configuration that was used on the tibia. The surgeon always has the option of adding additional fixation on the tibia by tying the sutures over a bony bridge created on the tibia or using a staple if the interference screw insertion contact is thought to be inadequate. From January 1, 1995 through December 31, 1997, we performed 94 ACL reconstructions, using a transfemoral pin technique. There were 67 SemiFix and 27 TransFix procedures performed during this period. All patients were examined at 1, 3, 6, 12, 26, and 52 weeks postoperatively. Subsequently they were examined yearly. All patients had a subjective evaluation using the IKDC Knee Ligament Standard Evaluation Form. KT-1000 measurements at maximum manual evaluation have been recorded in the TransFix group.
Fig 6. The fine wire loop on the end of the nitenol guide wire is slipped into the slot in the end of the 3-mm guide pin. The hand chuck is placed onto the femoral pin as it exits the skin medially. The guide pin and the nitenol wire are pulled through the femur, Once completely through, the ends of the nitenol wire are clamped with heavy Mayo clamps. The marking hook is then used to pull the loop of nitenol wire down through the femur and out of the tibial tunnels. (Reprinted with permission from Arthrex, Naples, FL.)
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EUGENE M. WOLF
TECHNIQUE The procedures were all performed under a general anesthetic, with a tourniquet and knee holder applied. All patients underwent a positive pivot shift and Lachman's test under anesthesia. The knee was first evaluated arthroscopically to determine the presence of associated pathology. Any meniscal or cartilage lesions were addressed before graft harvesting. Harvesting of the STG graft was performed using an inside-out technique. 19 A 4- to 5-cm incision is made over the insertion of the pes tendons, and the subcutaneous tissues are undermined to gain access to the tendons and the tibial tunnel site. The incision is carried down through the periosteum of the ~mnel site and through the pes tendons down to bone. The entire pes is reflected off the tibia. The gracilis and semitendinosis tendons are easily identified on the undersurface. They are dissected from the deep side of the sartorial fascia with a curved clamp, and are sectioned with a scalpel (Fig 1). This will leave a firm edge of conjoined tendon left to repair to the cut edge on the tibia when closing, yet still provide more than enough graft length. The semitendinosis and gracilis are then
separated with a scissors (Fig 2). It is important to identify the tendinous expansions of the gracilis and in particular the semitendinosus tendon and cut them before stripping them (Fig 3). Depending on the size of the tendons, a 5- or 7-mm tendon stripper is used to free them from their muscular origins. It is better to use the 5-mm tendon stripper if possible because it will strip the tendons more cleanly. Tapering the tendon end cut from the tibia will facilitate the use of the smaller stripper. An arthroscopic grasper is used to pull the end of the tendon through the tip of the tendon stripper. When through the end of the stripper, the tendon end is grasped with a Mayo clamp toward the base of its jaws. The tendon is then w o u n d around the clamp like a line around a wheel. This allows good tension to be placed on the tendon while the stripper is pushed proximally, stripping the muscle from the musculotendinous junction (Fig 4). The assistant prepares the grafts on the graft workstation while the surgeon performs the notchplasty and drills the tibial and femoral tunnels. A Cobb elevator is an ideal instrument for removing any muscle tissue from the tendons. The exact length of the graft can be measured by placing the marking hook 25 mm
Fig 7. The grafts are then loaded into the nitenol loop. Needle drivers or large clamps are placed on each end of the wire, and maximum tension is placed on the wire to pull the graft up into the tunnels. (Reprinted with permission from Arthrex, Naples, FL.)
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FEMORAL
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into the femoral tunnel and measuring the distance to the exit of the tibial tunnel. The tendons are cut to the exact length needed by removing and discarding the most proximal and tenuous part of the DSTG grafts. When the tibial tunnel is drilled at 60 °, the total length of the DSTG graft is 10 cm, thus the individual minimum total tendon length needed is 20 cm. The clamped tendon ends are inserted into the mounts on the workstation and tension is applied. The workstation allows tensioning of the grafts while 4 cm of tendon end is prepared with a running baseball stitch of no. i braided suture. This suture protects the graft and provides increased bulk for interference screw fixation. Tibial and femoral tunnels are created in the usual fashion with cannulated acorn reamers with the tibial tunnel 1 mm larger than the femoral tunnel. The tibial guide is set at 60 ° and should exit 4 mm lateral to the medial tibial spine. The femur is reamed to a minimum depth of 40 mm to easily accommodate the full length of the marking hook. The marking hook is firmly mounted on the TransFix femoral guide and is inserted through the tibial tunnel and up into the femoral tunnel to a depth of 25 to 30 mm as indicated by the laser markings on the hook. The pin sleeve is advanced to contact the skin over the lateral femoral condyle. The 3-mm guide pin has a sharp trocar tip and is pushed through the skin until it contacts the bony surface of the lateral femoral condyle. The 3-mm guide pin then is drilled through the distal femur in a direction that is slightly posterolateral to anteromedial to the coronal plane. The pin will pass through the opening in the marking hook, out the lateral cortex, and exit the skin anterior to the midcoronal plane. This will avoid any risk to the saphenous vein or nerve (Fig 5).
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The pin sleeve and femoral guide are removed, leaving the marking hook in place. Tension is placed on the hook to ensure that the guide pin has been captured in its opening. A no. 10 blade is then used to create a small incision through the skin and parallel to the fibers of the fascia lata by cutting along the guide pin. This allows entry of the cortical reamer that is placed over the guide pin until it contacts the lateral condylar flare. It is used to open the cortex to a depth of 7 mm. The wire loop of the nitenol guide wire is then slipped into the slot in the end of the 3-mm guide pin. The hand chuck is placed onto the femoral pin as it exits the skin medially. The guide pin and the nitenol wire are pulled through the femur. When completely through, the ends of the nitenol wire are clamped with heavy Mayo clamps. The marking hook is then used to pull the loop of nitenol wire down through the femur and out of the tibial tunnels (Fig 6). The grafts are then loaded into the nitenol loop. Needle drivers or large clamps are placed on each end of the wire, and maximum tension is placed on the wire to pull the graft up into the tunnels. It is recommended that the wire be pulled back and forth several times under maximum tension to ensure that the graft is pulled as far into the femoral tunnel as possible (Fig 7). The wire must slide easily under the graft, or a sterile traction b o w should be applied to the wire to ensure that the grafts are pulled all the w a y into tile femur and that the nitenol wire has no kinks. If the tension needed on the graft during insertion is significant at the outset, it is better to back the grafts out and enlarge the tunnels with a rasp or dilator. The TransFix cross-pin implant is placed on its impactor, and is gently slid over the nitenol guide wire and under Fig 8. The TransFix implant is placed on its impactor and gently is slid over the nitenol guide wire and under the grafts in the direction of the medial exit point of the wire. The TransFix implant should slide under the grafts, across the femur in the 3-mm tunnel that was created by the initial 3-mm guide pin. Simultaneous sliding of the nitenol guide wire in the direction of the TransFix pin insertion facilitates the passage of the pin under the grafts and through the femur. It is important not to place any tension on the graft during placement of the TransFix implant. When the TransFix implant has passed into the femur to the point where the head is contacting the lateral femoral cortex, it is driven into the femur with a mallet. A flare stop on the impactor prevents overpenetration into the femur. (Reprinted with permission from Arthrex, Naples, FL) EUGENE M. WOLF
on the impactor prevents overpenetration into the femur (Fig 8). The graft is then placed under tension, and the knee is put through a range of motion to check for isometry. A 28-ram-long headless tibial interference Bioscrew of the same diameter of the tibial tunnel is inserted until it is buried just below the tibial intercondylar cortex. The Bioscrew insertion should be visualized intra-articularly to ensure its proper placement (Fig 9).
POSTOPERATIVE CARE The patient is placed in a compressive dressing with an antiembolism stocking. A simple knee immobilizer is also applied before the patient leaves the operating room. Weight bearing as tolerated is allowed, and the patient is advised to remove the immobilizer as soon as he or she can perform a straight leg raise and is comfortable enough to begin active flexion and extension exercises. The patients are given a home therapy program, and then a gym program in which they progress rapidly to squats and active-resistive flexion-extension exercises. A stationary bicycle and other nonimpact activities are permitted as pain and range of motion permits. Return to noncutting, noncontact sports are allowed at 3 months postoperatively. Cutting and contact sports are allowed at 6 months.
RESULTS
Fig 9. A 28-mm-long headless interference Bioscrew of the same diameter of the tibial tunnel is inserted until it is buried just below the intercondylar cortex. The surgeon always has the option of adding additional fixation on the tibia by tying the sutures over a bony bridge created on the tibia or using a staple if the interference screw insertion contact is thought to be inadequate. (Reprinted with permission from Arthrex, Naples, FL)
the grafts in the direction of the medial exit point of the wire. The TransFix implant should slide under the grafts, across the femur in the 3-ram tunnel that was created by the 3-mm guide pin. Simultaneous sliding of the nitenol guide wire medially with TransFix pin insertion facilitates the passage of the pin under the grafts and through the femur. It is important not to place any tension on the graft during placement of the TransFix implant. When the TransFix implant has passed into the femur to the point where the head is close to contacting the lateral femoral cortex, it is driven into the femur with a mallet. A flare stop FEMORAL CROSS-PIN FIXATION ACL RECONSTRUCTION
In the SemiFix group there were four graft failures. All the failures that occurred were noted at the 6-month follow-up visit. One was a worker's compensation case and declined any further treatment. One was a 47-year-old low-demand woman who is satisfied with her knee in spite of positive Lachman's test and anterior drawer test results on examination. Of the 2 patients who required reoperation 8 and 15 months postoperatively, 1 patient underwent a BPTB autograft that also went on to fail within 6 months; the second patient had an Achilles tendon allograft, and the knee has been stabilized. On the IKDC activity scale, 41 patients (67%) returned to their preinjury activity level. Preinjury activity levels were reduced in 12 patients (18%) who had some pain with activities, and the above 4 patients (6%) with graft failure had complaints of instability. Only 1 patient experienced an extension loss after a SemiFix reconstruction. In the TransFix group (27 patients), there was 1 failure and recurrent instability. The patient was offered a revision procedure but declined. KT-1000 measurements have shown side-to-side difference of an average of 1.5 mm, with only 2 patients between 3 and 4 mm and the I failure at 9 mm, when compared with their contralateral side. No patient suffered any loss of motion, and 24 patients (88%) described their knee as normal or near normal.
DISCUSSION The debate continues regarding which is the best approach for the surgical reconstruction of the ACL. Comparative studies of BPTB and hamstrings have involved different hamstring techniques that do not offer the fixation strength of the TransFix. Nonetheless these studies have shown the
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h a m s t r i n g s to h a v e v e r y similar if n o t e q u a l results w h e n c o m p a r e d w i t h BPTB. 5-7 Existing i n f o r m a t i o n r e g a r d i n g the s t r e n g t h a n d stiffness of available grafts s h o w s the d o u b l e - l o o p e d s e m i t e n d i n o s u s a n d gracilis to be the strongest a n d stiffest. 11,18 BPTB grafts h a v e h a d the distinct a d v a n t a g e of b o n e - t o - b o n e healing, a feature that is p e r h a p s the m o s t p e r v a s i v e a r g u m e n t in f a v o r of the BPTB construct. But is the b o n e - t o - b o n e h e a l i n g faster, stronger, a n d better t h a n D L S G in a s n u g b o n e t u n n e l ? A n i m a l m o d e l s 14,15 h a v e s h o w n i m p r e s s i v e p u l l - o u t s t r e n g t h s at 4 a n d 6 w e e k s p o s t o p e r a t i v e l y . All s t u d i e s c o n c e r n i n g the m o r b i d i t y of A C L r e c o n s t r u c t i o n s h a v e s h o w n that the a d v a n t a g e is o n the side of the h a m s t r i n g r e c o n s t r u c tions. 2-9 W i t h the d e c r e a s e d m o r b i d i t y of DSTG, the o u t p a tient arena is m o r e accessible a n d the overall r e c o v e r y m o r e rapid. In this series the v a s t m a j o r i t y of p a t i e n t s w e r e able to d i s c a r d c r u t c h e s w i t h i n 5 d a y s a n d r e t u r n to d a i l y activities. Very f e w r e q u i r e d a f o r m a l p h y s i c a l t h e r a p y p r o g r a m . All p a t i e n t s w e r e a l l o w e d to b e a r w e i g h t as tolerated immediately. No patient required postoperative b r a c i n g of a n y type. N o p a t i e n t e x p e r i e n c e d a n y extension loss after u n d e r g o i n g a TransFix reconstruction. The p o s t o p e r a t i v e t h e r a p y p r o g r a m consisted of a h o m e exercise p r o g r a m , a n d the o n l y e q u i p m e n t n e e d e d w a s a 5 - p o u n d ankle w e i g h t . This t y p e of p o s t o p e r a t i v e p r o g r a m is ext r e m e l y cost-effective a n d p r o d u c e d g o o d or excellent results in 88% of patients. This t e c h n i q u e p r o v i d e s excellent fixation of the strongest available autograft. The results in this series are c o m p a r a b l e w i t h t h o s e r e p o r t e d for BPTB. Graft site m o r b i d i t y a n d a n t e r i o r k n e e p a i n w a s negligible.
REFERENCES 1. Johnson RJ, Beynnon BD, Nichols CE, et al: Current concepts review. The treatment of injuries of the anterior cruciate ligament. J Bone Joint Surg Am 74:140-151, 1992 2. Aglietti P, Buzzi R, D'Andria S, et al: Patello-femoral problems after intra-articular anterior cruciate ligament reconstruction. Clin Orthop 288:195-204, 1993 3. Christen B, Jakob RP: Fractures associated with patella ligament grafts in cruciate ligament surgery. J Bone Joint Surg Br 74:617-619, 1992
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4. O'Brien SJ, Warren RF, Pavlov H, et ah Reconstruction of the chronically insufficient anterior cruciate ligament with the central third of the patella ligament. J Bone Joint Surg Am 73:278-285, 1992 5. Marder RA, Raskind JR, Carroll M: Prospective evaluation of arthroscopically assisted anterior cruciate ligament reconstruction. Patella tendon versus semitendinosis/gracilis tendons. Am J Sports Med 19:478-484,1991 6. O'Neill DA: Arthroscopically assisted reconstruction of the anterior cruciate ligament. A prospective randomized analysis of three techniques. J Bone Joint Surg Am 78:803-813,1996 7. Pinczewski LA, Corry IS, Webb JM: A Comparison of Endoscopic Anterior Cruciate Ligament Reconstruction Utilizing Patella Tendon Autografts and Hamstring Tendon at 2 Years. Syllabus from the Arthroscopy Association of North America, Specialty Day at the Armual Meeting of AAOS. 169-174, 1998 8. Yasuda K, Tsujino J, Ohkoshi Y, et al: Graft site morbidity with autogenous semitendinosis and gracilis tendons. Am J Sports Med 23:706-714,1995 9. Lipscomb AB, Johnston RK, Snyder RB, et al: Evaluation of hamstring strength following use of semitendinosis and gracilis tendons to reconstruct the anterior cruciate ligament. Am J Sports Med 10:340342, 1982 10. Howell S, Gottllieb J: Endoscopic fixation of a double looped semitendinosis and gracilis anterior cruciate graft using a bone mulch screw. Operative Techniques Orthop 6:152-160, 1996 11. Noyes FR, Butler DL, Grood ES, et al: J Bone Joint Surg Am 66:344-352, 1984 12. Daniel DM, et al (eds): Knee Ligaments. New York, Raven Press, 1990 13. Grana WA, Egle DM, Mahnken R, et al: An analysis of autograft fixation after anterior cruciate ligament reconstruction in the rabbit model. Am J Sports Med 22:344-351, 1994 14. Rodeo SA, Arnoczky SP, Torzilli PA, et al: Tendon healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am 75:1795-1803, 1995 15. UInsalata JC, Klatt B, Fu FH, et ah Tunnel expansion following anterior cruciate ligament reconstruction: A comparison of hamstring and patella tendon autografts. Knee Surg Sports Traumatol Arthrosc 5:234-238, 1997 16. Fahey M, Indelicato P: Bone tunnel enlargement after anterior cruciate ligament replacement. Am J Sports Med 22:410-414,1994 17. Dyer C, Elrod B: Tibial and femoral bone tul~nel ei~largement following allograft replacement of the anterior cruciate ligament. J Arthros 11:352-354, 1995 18. Howell SM, Hull ML, et al: Aggressive rehabilitation using hamstring tendons: Graft construct, tibial tunnel placement, fixation properties, and clinical outcome. Am J Knee Surg 11:120-127,1998 19. Fontes R, Wolf EM: The inside out technique for harvesting the semitendinosis and gracilis tendons. Poster Exhibit, Annual Meeting of the AAOS, New Orleans, LA, March 1998.
EUGENE M. WOLF
Surgical reconstruction of the anterior cruciate ligament (ACL) with bone-patella tendon-bone (BPTB) graft has become the most commonly performed procedure for the unstable cruciate-deficient knee. The use of BPTB has been complicated by chronic anterior knee pain, loss of extension, patella tendon rupture, and patella fractures. The TransFix technique uses a double-looped semitendinosis and gracilis (DLSG) graft that is stronger than BPTB, and has less graft site and operative morbidity. This technique uses cross-pin femoral fixation and tibial interference screw fixation in the tibia that allows immediate weight bearing and an aggressive rehabilitation program. Results are equal to those previously reported for BPTB. KEY WORDS: double looped semitendinosis and gracilis, femoral cross-pin, tibial Bioscrew fixation
The evolution of more demanding and active lifestyles of our population combined with the technical advances of arthroscopic surgical techniques has made the surgical reconstruction of the anterior cruciate ligament (ACL) the standard of care in the treatment of the unstable ACLdeficient knee3 Arthroscopic-assisted bone-patella tendonbone (BPTB) autograft has become the most commonly used procedure in ACL reconstruction. Although this approach that has become the gold standard in ACL reconstruction, complications and problems have been reported2-4: Patella chondromalacia with chronic anterior knee pain Decreased range of motion with loss of extension Patella baja from patella ligament contracture Intraoperative or postoperative fractures of the patella Patella tendon ruptures Severed graft on femoral interference screw insertion The use of allograffs has solved some of these problems, but allograffs present significant cost and availability issues. The use of hamstrings (tripled or quadrupled semitendinosis or double-looped semitendinosis and gracilis [DLSG]) has gained popularity in recent years. A recent although informal survey of registrants at the annual meeting of the Arthroscopy Association of North America suggested that approximately 30% of the surgeons surveyed were using hamstring techniques. Whether or not an ACL reconstruction can restore stability and function in the unstable and ACL-deficient knee is no longer an issue. The issues at hand are which is the best graft and which is the best technique to use. The ideal technique should incorporate the following features:
From the Department of Orthopedic Surgery, California Pacific Medical Center, San Francisco, CA. Address reprint requests to Eugene M. Wolf, MD, 3000 California Street, San Francisco, CA 94115. Copyright © 1999 by W.B. Saunders Company 1060-1872/99/0704-0007510.00/0
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Restore the normal kinematics of the knee. Produce the least amount of operative morbidity possible. Have the strongest fixation possible. Use the strongest graft possible. Use a graft of optimal stiffness. Permit immediate weight bearing and an early rehabilitation program. Allow the most rapid return to the patient's preinjury level. Produce the least impact on daffy and professional activities. Facilitate revision of failed prior procedures. Be useful with open epiphyses. There are some recent comparative studies using BPTB and semitendinosis and gracils (STG) grafts. Marder et al s reviewed 80 patients. He found no significant differences in subjective results, KT-1000, or functional levels. O'Neill 6 compared the results in 125 patients. All patients were started immediately on an aggressive rehabilitation program. Analysis of functional outcome and return to sports at 42 months postoperatively showed no differences between arthroscopic BPTB and STG, with 89% and "88% returning to their preinjury level. The KT-1000 results showed no significant differences between the two groups. Pinczewski et al 7 recently presented a 2-year prospective study of 90 patients in each group of BPTB and quadrupled semitendinosus graft (HT) fixated with metal interference screws. There was no difference in the clinical examinations of both groups. There was no significant statistical difference in International Knee Data Collection (IKDC) assessments or abilities to return to prior athletic activities, but arthrometry showed that only 74% of HT versus 90% of BPTB had side-to-side differences of 3 mm or less. When compared with BPTB, the graft site morbidity of STG grafts has proven to be negligible. Yasuda et al 8 showed in 65 patients that donor site soreness resolved completely at 3 months, and that the hamstring muscle strength had returned to normal at 9 months. Lipscomb et al 9 evaluated 51 patients for hamstring and quadriceps strength at 26.2 months postoperatively. Hamstring strength
Operative Techniques in Sports Medicine, Vol 7, No 4 (October), 1999: pp 214-222
was found to be at 99% and quadriceps at 96% when compared by isokinetic testing. In the previously cited study by Pinczewski et al, there was significantly less thigh atrophy in the hamstring group, although the difference disappeared after 2 years. At 2 years postoperatively, 33% of the BPTB group as opposed to 7% of the HT group experienced anterior knee pain. Which is the strongest, stiffest graft, BPTB or doublelooped semitendinosus and gracilis (DLSTG)? The best w a y to restore the normal kinematics of the knee is to construct a strong and isometric graft. Present data indicate that the double-looped semitendinosus and gracilis tendons composite is the stronger and stiffer graft when compared with the 10-mm BPTB graft¢ °-n The DLSTG has a cross-sectional diameter and stiffness that resembles the normal ACL more than the 10-mm BPTB graft. The 10-mm BPTB graft is 125% of the normal ACL, whereas the DLSTG is 249% of the normal ACL. With a stronger graft, the technique used to fixate the DLSTG must provide strong enough fixation over a sufficient period of time to allow early weight bearing and rapid return to normal daily activities. H o w long does it take to obtain adequate biological
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Fig 2. The fibers of the conjoined insertion of the semitendinosus and gracilis tendons are sectioned with scissors. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.) Gracilis
~
Semitendinosus - i?
Fig 1. A 4- to 5-cm incision is made over the insertion of the pes tendons, and the subcutaneous tissues are undermined to gain access to the tendons and the tibial tunnel site. The incision is carried down through the periosteum of the tunnel site and through the pes tendons down to bone. The entire pes is reflected off the tibia. The gracilis and semitendinosus tendons are easily identified on the undersurface. They are dissected from the sartorial fascia with a curved clamp and are sectioned with a knife, cutting down on the clamp. This will leave a firm edge of conjoined tendon left to repair to the stump on the tibia when closing, yet still provide more than enough graft to work with. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.) FEMORAL CROSS-PIN FIXATION ACL RECONSTRUCTION
healing of tendons in bone tunnels? Grana et aU3 showed in the rabbit model that collagenous and bony ingrowth exceeds the strength of the tendon graft at 3 weeks. The results showed that by 3 weeks, failure of the construct occurred at the intra-articular portion of the graft and not by pull-out of the tendon from the tunnels. Rodeo et aU4 studied tendon healing in bone tunnels in dogs. The dogs were killed at 2-, 4-, 8-, 12-, and 26-week intervals. At 2, 4, and 8 weeks, pull-out occurred from the tunnels. At 12 and 26 weeks, the tendon failed by pull-out of the tendon from the test clamp or by midsubstance rupture. They concluded that STG grafts should be protected for at least 8 weeks. This was a study that transplanted the long digital extensor tendon through a 4.5-mm drill hole in the proximal tibia and had no intra-articular component. At 4 weeks the average pull-out strength was already 274 N, and increased to 295 N and 357 N at 8 and 12 weeks, respectively. The pull-out loads were roughly proportional to tunnel lengths, and those tunnels lengths were as short as 9 mm. If one could extrapolate these data and correlate them to the size of STG grafts and tunnels in the human model, one would expect pull-out strengths far in excess of that necessary for the most aggressive rehabilitation program. 215
TRANSFIX TECHNIQUE The femoral fixation is obtained with a cannulated crosspin, 3 m m in diameter, with a specially designed, 7-mm-wide head that is impacted into the lateral femoral cortex. The initial design of the cross pin (SemiFix, Arthrex, Naples, FL) incorporated a 7-mm-wide threaded head that
Gracilis
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,
/
Fig 3. It is important to identify the tendinous expansions to the gastrocnemius of the gracilis, and in particular the semitendinosus tendon, and cut them before stripping them. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.)
Radiographic enlargement of bone tunnels has been reported after ACL reconstruction using BPTB autografts 15 and BPTB allografts. 16Although this has not been correlated with poor outcomes, the apparent enlargement on radiographs of a tunnel within which a graft is supposed to be incorporated does raise some concerns. It was thought that the enlargement was caused by the ethylene oxide sterilization of allografts. 17 UInsalata et a115compared ~mnel expansion after BPTB and hamstrings autografts. There was a considerable increase in ~nnel width in the hamstring group, most notably on the tibial side (30.2%) when compared with the BPTB group (9.7%). There was no enlargement of tunnels on the femoral side when BPTB was used. They concluded that the points of graft fixation were the determining factors in the degree of tunnel enlargement, and that micromotion of the grafts in the tunnels produces the enlargement. The hamstrings were fixated outside of the tunnels with cortical devices and Mersilene (Ethicon Inc., Somerville, NJ) tape, thereby creating longer grafts that were susceptible to graft strain within the tunnels. Thus a shorter graft with rigid fixation within the tunnels not dependent on suture or Mersilene tape would be optimal. 216
Fig 4. Depending on the size of the tendons, a 5- or 7-mm tendon stripper is used to free them from their muscular origins. It is petter to use the 5-mm stripper if possible because it will strip the tendons more cleanly. The bulbous distal end of the tendon may be trimmed back to facilitate the use of the smaller stripper. An arthroscopic grasper is used to pull the tendon through the tip of the tendon stripper. When through the end of the stripper, the tendon end is grasped with a Mayo clamp toward the base of the clamp's jaws. The tendon is then wound around the clamp. This allows good tension to be placed on the tendon while the stripper is pushed proximally, stripping the muscle at the musculotendinous junction. (Figure printed with permission from Susan E. Brust, MS, CMI. Copyright © 1999 Susan E. Brust.) EUGENE M. WOLF
was screwed into the lateral femoral cortex. There were technical difficulties encountered with this screw design. The grafts could be w o u n d up as if on a winch when the screw/implant was turned in the femur. There were difficulties advancing the screw-like device as the head encountered the oblique metaphyseal surface of the lateral femoral cortex. The TransFix implant (Arthrex Corporation, Naples, FL) can now be impacted into the femur with a mallet. Impacting the implant avoids the above-cited problem, and the implant is designed to act as a staple on impaction and as a screw on removal. The head of the implant still has a threaded configuration that allows its removal with a hex-head screwdriver, should it ever be deemed necessary. The TransFix implant is passed over a flexible nitenol wire that is used to pull the grafts into snug tunnels in the tibia and femur. The TransFix technique places the femoral implant at 90 ° to the graft as it passes under the DLSTG. The ultimate load (4,113 N) and stiffness (689 N) of cross-pin fixation far exceeds that of any other type of fixation of a graft in the femur. 18 A biodegradable screw, the Bioscrew (Arthrex Corporation, Naples, FL), provides the tibial fixation. Weiler showed using h u m a n cadaver semitendinosus tendons and bovine proximal tibias that a biodegradable screw had higher pull-out strength than a titanium screw (Weiler A, unpublished data). He hypothesized that the stiffness gradient between the polymeric screw and the bone was lower than that of the titanium interface, resulting in better transmission of the shear forces. The surface texture of the Bioscrew
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provided a better grip on the tendon surfaces. A 9-mm × 28-mm screw is used in an 8 mm tunnel, and a 10 × 28 m m screw in a 9-ram tunnel is recommended in this technique. The Bioscrew is 28 m m long, and is inserted into the tibia along the sutured section of the graft into the tibia until it reaches the cortical surface of the intercondylar area. An additional security point of fixation can be afforded by creating a bony bridge distal to the tibial tunnel. The 3-mm transfemoral pin can be used to create a drill hole 1 cm distal to the tunnel A currette is used to open a space behind the cortex to allow passage of half the sutures. In this case, the grafts must be prepared so they do not exceed 20 cm in length, to ensure that they will not extend beyond the tibial tunnel opening. Sutures at one end of the grafts are shorter so they can be identified and properly tied over the bony bridge. There is a new Bio-Interference screw, 17 m m in length, designed to enhance the tibial fixation by capturing the graft at the cortical opening of the tibial tunnel (Arthrex, Naples, FL). The fixation afforded by the TransFix system allows the patients to immediately bear weight and to begin an exercise program as soon as tolerated.
MATERIALS AND METHODS This technique has undergone a considerable degree of evolution since its original clinical use in 1994. The original technique called for dragging the tendons up through the tunnels using a fork-like device. This necessitated larger
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Fig 5. The marking hook that is firmly mounted on the femoral guide is inserted up through the tibial tunnel and up into the femoral tunnel to a depth of 25 to 30 mm as indicated by the laser markings on the hook. The pin sleeve is advanced to contact the skin, and the sharp trocartipped 3-mm guide pin is pushed through the skin to contact bone. It is drilled through the distal femur in a direction that is slightly posterolateral to anteromedial to the coronal plane. The pin will pass through the opening in the marking hook, out the lateral cortex, and exit the skin anterior to the midcoronal plane. This will avoid any risk to the saphenous vein or nerve. (Arthrex, Naples, FL). (Reprinted with permission from Arthrex, Naples, FL.)
FEMORAL CROSS-PIN FIXATION ACL RECONSTRUCTION
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tunnels than are now used in the TransFix technique, to accommodate the concomitant insertion of the tendons and the fork-like marking hook. The adoption of a modified marking hook and a nitenol wire has permitted the use of tunnels that are based on the measured width of the grafts. This affords a snug fit in the tunnels and excellent contact at the tendon-bone interface to avoid any windshield-wiper-like motion of the grafts. The tibial tunnel should be reamed 1 m m larger than the femoral tunnel to accommodate the extra bulk of the tendon ends and sutures. The grafts are measured in the graft-measuring block with the notion of different tunnel sizes for the tibia and femur. The proximal or femoral end of the graft will always be smaller than the tibial side. The DLSG tendon graft should be sized at each end to determine the appropriate tunnel size. The most common tunnel size configuration is an 8-mm femoral tunnel and a 9-mm tibial tunnel. The SemiFix screw has been replaced by the 3-mm Trans-
Fix implant. This pin is available in both 40- and 50-mm lengths. The 28-mm headless resorbable screw has replaced the double-staple fixation configuration that was used on the tibia. The surgeon always has the option of adding additional fixation on the tibia by tying the sutures over a bony bridge created on the tibia or using a staple if the interference screw insertion contact is thought to be inadequate. From January 1, 1995 through December 31, 1997, we performed 94 ACL reconstructions, using a transfemoral pin technique. There were 67 SemiFix and 27 TransFix procedures performed during this period. All patients were examined at 1, 3, 6, 12, 26, and 52 weeks postoperatively. Subsequently they were examined yearly. All patients had a subjective evaluation using the IKDC Knee Ligament Standard Evaluation Form. KT-1000 measurements at maximum manual evaluation have been recorded in the TransFix group.
Fig 6. The fine wire loop on the end of the nitenol guide wire is slipped into the slot in the end of the 3-mm guide pin. The hand chuck is placed onto the femoral pin as it exits the skin medially. The guide pin and the nitenol wire are pulled through the femur, Once completely through, the ends of the nitenol wire are clamped with heavy Mayo clamps. The marking hook is then used to pull the loop of nitenol wire down through the femur and out of the tibial tunnels. (Reprinted with permission from Arthrex, Naples, FL.)
218
EUGENE M. WOLF
TECHNIQUE The procedures were all performed under a general anesthetic, with a tourniquet and knee holder applied. All patients underwent a positive pivot shift and Lachman's test under anesthesia. The knee was first evaluated arthroscopically to determine the presence of associated pathology. Any meniscal or cartilage lesions were addressed before graft harvesting. Harvesting of the STG graft was performed using an inside-out technique. 19 A 4- to 5-cm incision is made over the insertion of the pes tendons, and the subcutaneous tissues are undermined to gain access to the tendons and the tibial tunnel site. The incision is carried down through the periosteum of the ~mnel site and through the pes tendons down to bone. The entire pes is reflected off the tibia. The gracilis and semitendinosis tendons are easily identified on the undersurface. They are dissected from the deep side of the sartorial fascia with a curved clamp, and are sectioned with a scalpel (Fig 1). This will leave a firm edge of conjoined tendon left to repair to the cut edge on the tibia when closing, yet still provide more than enough graft length. The semitendinosis and gracilis are then
separated with a scissors (Fig 2). It is important to identify the tendinous expansions of the gracilis and in particular the semitendinosus tendon and cut them before stripping them (Fig 3). Depending on the size of the tendons, a 5- or 7-mm tendon stripper is used to free them from their muscular origins. It is better to use the 5-mm tendon stripper if possible because it will strip the tendons more cleanly. Tapering the tendon end cut from the tibia will facilitate the use of the smaller stripper. An arthroscopic grasper is used to pull the end of the tendon through the tip of the tendon stripper. When through the end of the stripper, the tendon end is grasped with a Mayo clamp toward the base of its jaws. The tendon is then w o u n d around the clamp like a line around a wheel. This allows good tension to be placed on the tendon while the stripper is pushed proximally, stripping the muscle from the musculotendinous junction (Fig 4). The assistant prepares the grafts on the graft workstation while the surgeon performs the notchplasty and drills the tibial and femoral tunnels. A Cobb elevator is an ideal instrument for removing any muscle tissue from the tendons. The exact length of the graft can be measured by placing the marking hook 25 mm
Fig 7. The grafts are then loaded into the nitenol loop. Needle drivers or large clamps are placed on each end of the wire, and maximum tension is placed on the wire to pull the graft up into the tunnels. (Reprinted with permission from Arthrex, Naples, FL.)
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FEMORAL
CROSS-PIN
FIXATION
ACL
RECONSTRUCTION
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into the femoral tunnel and measuring the distance to the exit of the tibial tunnel. The tendons are cut to the exact length needed by removing and discarding the most proximal and tenuous part of the DSTG grafts. When the tibial tunnel is drilled at 60 °, the total length of the DSTG graft is 10 cm, thus the individual minimum total tendon length needed is 20 cm. The clamped tendon ends are inserted into the mounts on the workstation and tension is applied. The workstation allows tensioning of the grafts while 4 cm of tendon end is prepared with a running baseball stitch of no. i braided suture. This suture protects the graft and provides increased bulk for interference screw fixation. Tibial and femoral tunnels are created in the usual fashion with cannulated acorn reamers with the tibial tunnel 1 mm larger than the femoral tunnel. The tibial guide is set at 60 ° and should exit 4 mm lateral to the medial tibial spine. The femur is reamed to a minimum depth of 40 mm to easily accommodate the full length of the marking hook. The marking hook is firmly mounted on the TransFix femoral guide and is inserted through the tibial tunnel and up into the femoral tunnel to a depth of 25 to 30 mm as indicated by the laser markings on the hook. The pin sleeve is advanced to contact the skin over the lateral femoral condyle. The 3-mm guide pin has a sharp trocar tip and is pushed through the skin until it contacts the bony surface of the lateral femoral condyle. The 3-mm guide pin then is drilled through the distal femur in a direction that is slightly posterolateral to anteromedial to the coronal plane. The pin will pass through the opening in the marking hook, out the lateral cortex, and exit the skin anterior to the midcoronal plane. This will avoid any risk to the saphenous vein or nerve (Fig 5).
iii!!;iii~!!i iiii
220
The pin sleeve and femoral guide are removed, leaving the marking hook in place. Tension is placed on the hook to ensure that the guide pin has been captured in its opening. A no. 10 blade is then used to create a small incision through the skin and parallel to the fibers of the fascia lata by cutting along the guide pin. This allows entry of the cortical reamer that is placed over the guide pin until it contacts the lateral condylar flare. It is used to open the cortex to a depth of 7 mm. The wire loop of the nitenol guide wire is then slipped into the slot in the end of the 3-mm guide pin. The hand chuck is placed onto the femoral pin as it exits the skin medially. The guide pin and the nitenol wire are pulled through the femur. When completely through, the ends of the nitenol wire are clamped with heavy Mayo clamps. The marking hook is then used to pull the loop of nitenol wire down through the femur and out of the tibial tunnels (Fig 6). The grafts are then loaded into the nitenol loop. Needle drivers or large clamps are placed on each end of the wire, and maximum tension is placed on the wire to pull the graft up into the tunnels. It is recommended that the wire be pulled back and forth several times under maximum tension to ensure that the graft is pulled as far into the femoral tunnel as possible (Fig 7). The wire must slide easily under the graft, or a sterile traction b o w should be applied to the wire to ensure that the grafts are pulled all the w a y into tile femur and that the nitenol wire has no kinks. If the tension needed on the graft during insertion is significant at the outset, it is better to back the grafts out and enlarge the tunnels with a rasp or dilator. The TransFix cross-pin implant is placed on its impactor, and is gently slid over the nitenol guide wire and under Fig 8. The TransFix implant is placed on its impactor and gently is slid over the nitenol guide wire and under the grafts in the direction of the medial exit point of the wire. The TransFix implant should slide under the grafts, across the femur in the 3-mm tunnel that was created by the initial 3-mm guide pin. Simultaneous sliding of the nitenol guide wire in the direction of the TransFix pin insertion facilitates the passage of the pin under the grafts and through the femur. It is important not to place any tension on the graft during placement of the TransFix implant. When the TransFix implant has passed into the femur to the point where the head is contacting the lateral femoral cortex, it is driven into the femur with a mallet. A flare stop on the impactor prevents overpenetration into the femur. (Reprinted with permission from Arthrex, Naples, FL) EUGENE M. WOLF
on the impactor prevents overpenetration into the femur (Fig 8). The graft is then placed under tension, and the knee is put through a range of motion to check for isometry. A 28-ram-long headless tibial interference Bioscrew of the same diameter of the tibial tunnel is inserted until it is buried just below the tibial intercondylar cortex. The Bioscrew insertion should be visualized intra-articularly to ensure its proper placement (Fig 9).
POSTOPERATIVE CARE The patient is placed in a compressive dressing with an antiembolism stocking. A simple knee immobilizer is also applied before the patient leaves the operating room. Weight bearing as tolerated is allowed, and the patient is advised to remove the immobilizer as soon as he or she can perform a straight leg raise and is comfortable enough to begin active flexion and extension exercises. The patients are given a home therapy program, and then a gym program in which they progress rapidly to squats and active-resistive flexion-extension exercises. A stationary bicycle and other nonimpact activities are permitted as pain and range of motion permits. Return to noncutting, noncontact sports are allowed at 3 months postoperatively. Cutting and contact sports are allowed at 6 months.
RESULTS
Fig 9. A 28-mm-long headless interference Bioscrew of the same diameter of the tibial tunnel is inserted until it is buried just below the intercondylar cortex. The surgeon always has the option of adding additional fixation on the tibia by tying the sutures over a bony bridge created on the tibia or using a staple if the interference screw insertion contact is thought to be inadequate. (Reprinted with permission from Arthrex, Naples, FL)
the grafts in the direction of the medial exit point of the wire. The TransFix implant should slide under the grafts, across the femur in the 3-ram tunnel that was created by the 3-mm guide pin. Simultaneous sliding of the nitenol guide wire medially with TransFix pin insertion facilitates the passage of the pin under the grafts and through the femur. It is important not to place any tension on the graft during placement of the TransFix implant. When the TransFix implant has passed into the femur to the point where the head is close to contacting the lateral femoral cortex, it is driven into the femur with a mallet. A flare stop FEMORAL CROSS-PIN FIXATION ACL RECONSTRUCTION
In the SemiFix group there were four graft failures. All the failures that occurred were noted at the 6-month follow-up visit. One was a worker's compensation case and declined any further treatment. One was a 47-year-old low-demand woman who is satisfied with her knee in spite of positive Lachman's test and anterior drawer test results on examination. Of the 2 patients who required reoperation 8 and 15 months postoperatively, 1 patient underwent a BPTB autograft that also went on to fail within 6 months; the second patient had an Achilles tendon allograft, and the knee has been stabilized. On the IKDC activity scale, 41 patients (67%) returned to their preinjury activity level. Preinjury activity levels were reduced in 12 patients (18%) who had some pain with activities, and the above 4 patients (6%) with graft failure had complaints of instability. Only 1 patient experienced an extension loss after a SemiFix reconstruction. In the TransFix group (27 patients), there was 1 failure and recurrent instability. The patient was offered a revision procedure but declined. KT-1000 measurements have shown side-to-side difference of an average of 1.5 mm, with only 2 patients between 3 and 4 mm and the I failure at 9 mm, when compared with their contralateral side. No patient suffered any loss of motion, and 24 patients (88%) described their knee as normal or near normal.
DISCUSSION The debate continues regarding which is the best approach for the surgical reconstruction of the ACL. Comparative studies of BPTB and hamstrings have involved different hamstring techniques that do not offer the fixation strength of the TransFix. Nonetheless these studies have shown the
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h a m s t r i n g s to h a v e v e r y similar if n o t e q u a l results w h e n c o m p a r e d w i t h BPTB. 5-7 Existing i n f o r m a t i o n r e g a r d i n g the s t r e n g t h a n d stiffness of available grafts s h o w s the d o u b l e - l o o p e d s e m i t e n d i n o s u s a n d gracilis to be the strongest a n d stiffest. 11,18 BPTB grafts h a v e h a d the distinct a d v a n t a g e of b o n e - t o - b o n e healing, a feature that is p e r h a p s the m o s t p e r v a s i v e a r g u m e n t in f a v o r of the BPTB construct. But is the b o n e - t o - b o n e h e a l i n g faster, stronger, a n d better t h a n D L S G in a s n u g b o n e t u n n e l ? A n i m a l m o d e l s 14,15 h a v e s h o w n i m p r e s s i v e p u l l - o u t s t r e n g t h s at 4 a n d 6 w e e k s p o s t o p e r a t i v e l y . All s t u d i e s c o n c e r n i n g the m o r b i d i t y of A C L r e c o n s t r u c t i o n s h a v e s h o w n that the a d v a n t a g e is o n the side of the h a m s t r i n g r e c o n s t r u c tions. 2-9 W i t h the d e c r e a s e d m o r b i d i t y of DSTG, the o u t p a tient arena is m o r e accessible a n d the overall r e c o v e r y m o r e rapid. In this series the v a s t m a j o r i t y of p a t i e n t s w e r e able to d i s c a r d c r u t c h e s w i t h i n 5 d a y s a n d r e t u r n to d a i l y activities. Very f e w r e q u i r e d a f o r m a l p h y s i c a l t h e r a p y p r o g r a m . All p a t i e n t s w e r e a l l o w e d to b e a r w e i g h t as tolerated immediately. No patient required postoperative b r a c i n g of a n y type. N o p a t i e n t e x p e r i e n c e d a n y extension loss after u n d e r g o i n g a TransFix reconstruction. The p o s t o p e r a t i v e t h e r a p y p r o g r a m consisted of a h o m e exercise p r o g r a m , a n d the o n l y e q u i p m e n t n e e d e d w a s a 5 - p o u n d ankle w e i g h t . This t y p e of p o s t o p e r a t i v e p r o g r a m is ext r e m e l y cost-effective a n d p r o d u c e d g o o d or excellent results in 88% of patients. This t e c h n i q u e p r o v i d e s excellent fixation of the strongest available autograft. The results in this series are c o m p a r a b l e w i t h t h o s e r e p o r t e d for BPTB. Graft site m o r b i d i t y a n d a n t e r i o r k n e e p a i n w a s negligible.
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EUGENE M. WOLF