Medial Patellofemoral Ligament Reconstruction With a Looped Semitendinosus Tendon, Using Knotless Anchor Fixation on the Patella and Hybrid Fixation on the Femur Alexander Golant, M.D., Tony Quach, M.D., and Jeffrey E. Rosen, M.D.
Abstract: Medial patellofemoral ligament (MPFL) reconstruction is a reliable surgical method for stabilizing a dislocating patella, with multiple techniques previously described. Although outcomes are generally favorable, the procedure is technically demanding and relies on precise identification of native MPFL insertion sites, secure fixation of the graft to these sites, and appropriate graft tension. We describe a technique for MPFL reconstruction with a looped semitendinosus tendon. The 2 free limbs of the graft are secured into blind-end patellar sockets with knotless anchors, and the looped end is initially secured into a medial femoral socket with a button on the opposite (lateral) cortex. Use of an adjustable-loop button allows for gradual adjustment of graft tension, as well as re-tensioning after cycling of the knee, before final aperture fixation on the femur with an interference screw.
M
ultiple techniques for reconstruction of the medial patellofemoral ligament (MPFL) have been described, but no single “gold standard” exists. Despite the variations in techniques, however, certain principles have been identified as being of importance to every reconstruction. These principles include (1) graft selection, (2) identification of anatomic insertion sites of the MPFL on the femur and the patella, (3) secure fixation of the graft to these sites, and (4) appropriate adjustment of graft tension. We present a surgical technique for MPFL reconstruction with a doubled semitendinosus tendon, using knotless suture anchor fixation of the free ends to the patella, as well as hybrid femoral fixation consisting of an adjustable-loop cortical button and an interference screw. The use of an adjustable-loop button system allows gradual tensioning that can be checked with direct arthroscopic visualization and readjusted after cycling of the knee.
From New York Hospital Queens, Flushing, New York, U.S.A. The authors report the following potential conflict of interest or source of funding: A.G. has received support from Arthrex for a presentation unrelated to this manuscript. J.E.R. receives support from Ferring Pharmaceuticals. Received May 24, 2013; accepted October 28, 2013. Address correspondence to Alexander Golant, M.D., 163-03 Horace Harding Expressway, Fourth Floor, Fresh Meadows, NY 11365, U.S.A. E-mail: [email protected] Ó 2014 by the Arthroscopy Association of North America 2212-6287/13343/$36.00 http://dx.doi.org/10.1016/j.eats.2013.10.001
Preoperative Evaluation Preoperative imaging, in addition to anteroposterior and lateral radiographs of the affected knee, should include bilateral sunrise views on the same cassette to assess for differences in static alignment and tilt of the patella; this helps to determine the need for a lateral release (Table 1). Magnetic resonance imaging is obtained to evaluate articular cartilage injury, localize loose fragments, and rule out concomitant injuries to the menisci and ligaments. The tibial tubercleetoetrochlear groove distance should be calculated and is useful for predicting the need for a tibial tubercle transfer.1
Surgical Technique We prefer to use general anesthesia and a femoral nerve block for the surgical procedure. The patient is positioned supine. An examination with the patient under anesthesia is performed first, including comparison with the contralateral side. An intravenous antibiotic is administered before incision. Arthroscopy is performed next and should include documentation of any patellofemoral dysplasia (Tables 2 and 3). Lateral retinacular release may be performed as necessary for significant lateral tilt, but we do not routinely perform it for instability. Additional procedures may include loose body removal and debridement and microfracture of osteochondral lesions, as well as procedures for torn menisci. After completion of arthroscopy, the tourniquet is inflated. If an autograft is to be used, the semitendinosus
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Table 1. Preoperative Radiographic Evaluation
Table 3. Surgical Technique: Tips and Tricks
Obtain AP, lateral, and sunrise radiographs of the affected knee (this should include bilateral sunrise views on the same cassette to assess for differences in static alignment and tilt). Perform MRI to evaluate the condition of the MPFL and identify other intra-articular pathology (articular cartilage injury, osteochondral fragments, meniscus and ligament injuries). Perform MRI or a CT scan to calculate the TT-TG distance. A TT-TG value >20 mm is a relative indication for medialization of the tibial tubercle.
Mark all incisions before starting the procedure (because once the knee is swollen after the knee arthroscopy, the anatomic landmarks may be hard to palpate). Place a bump under the ipsilateral hip to ensure that the patella is facing up. Place a foam wedge or a sterile bump under the knee on the operative side to help obtain a perfect lateral fluoroscopic image. Load the Biomet ToggleLoc device onto the graft after insertion of the first SwiveLock anchor but before securing the second anchor. Aim the femoral tunnel guidewire (beath pin) slightly anteriorly to avoid injury to the posterior neurovascular structures. Make the femoral tunnel as long as possible (without violating the lateral cortex) to prevent the graft from bottoming out (before attaining the required tension). Make sure to verify the isometry of the planned reconstruction before reaming the femoral tunnel, when the position of the beath pin can still be changed if necessary. Confirm with fluoroscopy that the ToggleLoc button is properly flipped on the lateral femoral cortex. Preload the nitinol wire (for the interference screw) into the femoral tunnel before withdrawing the beath pin (for ease of tunnel localization).
Abbreviations: AP, anteroposterior; CT, computed tomography; MRI, magnetic resonance imaging; TT-TG, tibial tubercle-to-trochlear groove.
tendon is harvested through a 1-inch oblique incision directly over the pes anserinus. The graft is trimmed to be 18 to 20 cm long (9 to 10 cm folded on itself), and 2.5 cm of each end is whip-stitched with a No. 2 braided suture. The graft is then pre-tensioned (Video 1). Table 2. Surgical Technique: Step by Step Perform arthroscopy first. Harvest and prepare the semitendinosus tendon (total length of 18 to 20 cm, 4.5 mm single stranded, 6-mm tunnel folded). Expose the proximal half of the medial patellar facet (superficial to the joint capsule). Drill two 3.2-mm guidewires into the medial patella, at least 1.5 cm apart. Confirm the position using fluoroscopy. Use arthroscopy to confirm that there is no joint penetration. Over-ream the guidewires with a 4.5-mm reamer to a depth of 20 to 25 mm. Load the graft into the ToggleLoc loop. Secure the free ends into the patellar sockets with 2 SwiveLock 4.75-mm knotless anchors. Locate the femoral insertion of the MPFL with an Arthrex radiodense template (bump under the knee, perfect lateral image on fluoroscopy). Drill a beath pin percutaneously into the medial femoral condyle through this template. Dissect down to the medial femoral condyle over the beath pin. Develop the correct tissue plane (second layer of the medial knee) from the patella to the femur. Shuttle the sutures from the SwiveLock anchors to the femoral pin, and wrap them around the pin under tension. Take the knee through a range of motion to assess the isometry of the planned reconstruction. Reposition the beath pin if necessary. Ream a 6-mm blind femoral tunnel over the beath pin; do not violate the lateral cortex. Pass the graft and ToggleLoc device from the patella to the femur. Preload the nitinol wire into the femoral tunnel. Withdraw the beath pin through the lateral side of the knee, with the leading suture for the ToggleLoc device. Now, pass the ToggleLoc button through the tunnel and flip it on the lateral femoral cortex (confirm with fluoroscopy). With the knee flexed 20 to 30 , draw the graft loop into the femoral tunnel (pull on the tensioning suture of the ToggleLoc) and set the desired tension. Make sure not to overtighten or produce excessive medialization of the patella. Directly observe the patellofemoral articulation during this process with an arthroscope. Cycle the knee through a full range of motion, and adjust graft tension as necessary. Insert a 6 23emm interference screw into the femoral tunnel over the preloaded nitinol wire, flush with the condyle. Remove the wire, and cut the ToggleLoc tensioning sutures. Perform closure in layers.
A 2-incision technique is used to access the patellar and femoral insertion sites of the MPFL. A 3- to 4-cm longitudinal incision is made over the medial border of the patella, and the upper half to three-quarters of the medial patellar facet is exposed, staying superficial to the joint capsule (Video 1). Under fluoroscopic imaging, two 3.2-mm guidewires are drilled into the patella from the medial facet, parallel to each other, and aiming slightly anterior to avoid penetration into the joint (Fig 1). The inferior wire is placed at or just below the half point of the patella. The superior wire is placed at least 1.5 cm proximal to ensure adequate separation between the sockets. The guidewires are over-reamed with a 4.5-mm reamer to a depth of 25 mm (Video 1). The graft is then loaded onto an adjustable suspensory fixation device (ToggleLoc; Biomet, Warsaw, IN) and secured into 2 patellar sockets with 4.75-mm knotless anchors (SwiveLock; Arthrex, Naples, FL) (Fig 2, Video 1). The femoral insertion site of the MPFL is identified with the aid of fluoroscopy. It is located on a line drawn between the medial femoral epicondyle and the adductor tubercle, approximately 2 mm anterior and 4 mm distal to the adductor tubercle. The radiographic location has been described as 1 mm anterior to the posterior femoral cortex extension line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the level of the posterior point of the Blumensaat line on a perfect lateral radiograph of the knee.2 A perfect lateral image of the knee is obtained, and by use of a radiodense template (Arthrex), a beath pin is percutaneously inserted and drilled into the medial femoral condyle (Fig 3, Video 1). The guidewire should not be aimed posterior or distal to avoid injury to the neurovascular structures or penetration into the
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Fig 1. (A) Guidewires are drilled into the medial facet of the patella, where the 2 free limbs of the graft will be secured. One should note the incision over the pes anserinus for harvesting of the semitendinosus tendon. (B) Fluoroscopic verification of appropriate guidewire position on anteroposterior image.
knee joint. A small (2-cm) longitudinal incision is made directly over the guidewire, and dissection is carried down to the femoral condyle (Video 1). Next, the tissue plane for passage of the graft is developed. The graft is placed into the same layer in which the native MPFL is found. Near the patella, the MPFL is often contiguous with the aponeurosis of the vastus medialis oblique, whereas near the femur, its insertion is close to that of the medial collateral ligament. By use of a blunt clamp, the appropriate layer is developed, deep to the crural fascia but superficial to the joint capsule, to connect the femoral and patellar incisions. The sutures from the patellar anchors are then passed to the femur and wrapped around the
Fig 2. The free limbs of the semitendinosus graft have been secured into the 4.5-mm sockets on the proximal half of the medial patellar facet with 2 Arthrex 4.75-mm SwiveLock anchors. One should note that the graft has been preloaded onto an adjustable-loop suspensory cortical button device (Biomet ToggleLoc).
guidewire. The knee is taken through a range of motion to assess the isometry of the sutures in early flexion, which predicts the isometry of the reconstructed ligament (Video 1). If there is significant deviation from the expected isometry, the guidewire position may be wrong and it should be repositioned. A blind femoral tunnel is then reamed over the guidewire (Fig 4). The diameter of the tunnel is determined by the folded diameter of the graft (typically 6
Fig 3. The location for the femoral insertion of the MPFL is identified with the aid of fluoroscopy and a radiodense template, and a guidewire is drilled into this spot.
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the knee in 30 of flexion, the tensioning sutures are pulled until appropriate stability is felt when one is translating the patella laterally. The knee is then cycled through a full range of motion several times, and tension is rechecked (Video 1). Arthroscopy is performed to check alignment and stability by direct visualization of the patellofemoral articulation. After the graft tension is appropriately adjusted, a nitinol wire is placed into the tunnel and a 6 23emm BioComposite screw (Arthrex) is inserted (Video 1). The tourniquet is then deflated, and the incisions are closed in layers.
Postoperative Care
Fig 4. The femoral guidewire is over-reamed with a reamer (the diameter of which matches the diameter of the graft) as far as possible across the distal femur, without violating the medial cortex. Ideally, the reamer should be stopped within 2 cm from the medial cortex.
mm). We prefer to drill the tunnel as far as possible to prevent the graft from bottoming out and to ream over the wire under fluoroscopic imaging, stopping 2 cm short of the lateral cortex (Video 1). The graft is brought through the appropriate layer to the entrance of the femoral tunnel (Fig 5); the button is passed through the tunnel and flipped on the lateral femoral cortex (Fig 6). The tensioning sutures are then pulled to draw the graft into the femoral tunnel (Video 1). At this point, the graft is already secured within the femoral tunnel, and the tension can be adjusted. With
Fig 5. The graft, along with the ToggleLoc device, has been tunneled within the second layer of the medial knee (deep to the crural fascia, superficial to the medial retinaculum) to the opening of the femoral tunnel.
Postoperatively, weight bearing is allowed with crutches and a brace locked in extension (Table 4). Range-of-motion and isometric quadriceps strengthening is initiated immediately. Use of crutches is discontinued after 2 weeks, and brace use is discontinued after 6 weeks. Sports training is initiated after 3 months, and unrestricted participation is allowed after 6 months, provided that the patient has a pain-free knee, full range of motion, normal patellar stability, and normal or near-normal quadriceps strength.
Discussion The MPFL is an important soft-tissue restraint of the patellofemoral joint, providing up to 60% of the checkrein to lateral patellar displacement at 0 to 30 , where the patella is not yet engaged in the trochlea.3,4 Sectioning of the MPFL increases lateral patellar subluxation by 50%5 and decreases the force required to translate the patella laterally by 10 mm by 50%.6 The MPFL is ruptured in as many as 90% of acute dislocations7 and is either ruptured or attenuated in almost 100% of cases of recurrent instability.8 Restoration of MPFL integrity, including its anatomic insertion sites, can restore patellofemoral tracking to normal4,5,9 and is therefore an important component of any surgical plan for patellar stabilization. Anatomic MPFL reconstruction was first described in 1992,10 and since then, it has been shown that this procedure produces excellent results in patients with patellofemoral instability, with low rates of recurrent instability, low complication rates, and good functional improvement, as well as a relatively low risk of development and progression of arthritis.10-17 Although many variations on the surgical technique for MPFL reconstruction have been described, there is no consensus with regard to the surgical approach, choice of graft, graft positioning, and fixation methods.11,18 Only a handful of studies have directly compared different surgical techniques, and they suggest that there may be better outcomes when both bundles of the MPFL are reconstructed, as compared with a single-bundle reconstruction.19,20 Otherwise, there has not emerged a single
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Fig 6. (A) Fluoroscopic anteroposterior image of final reconstruction. One should note that the button is lying directly on the medial cortex. In addition, the central position of the patella should be noted. (B) Fluoroscopic lateral image of final reconstruction. One should note the positions of the patellar and femoral tunnels, consistent with the anatomic insertions of the native MPFL.
surgical technique that has shown clear superiority over the other techniques. A significant percentage of complications associated with MPFL reconstruction occur because of technical errors.21,22 These errors typically involve improper graft position and/or tension. Recurrent instability can occur when the graft is too loose or if fixation at either the femoral or patellar side fails. Conversely, overtightening or malpositioning of the graft can lead to maltracking, stiffness, and excessive medial compressive forces.23 Malpositioning the graft and making it too short may as much as double the graft tension in flexion,24 which is likely to lead to the development of stiffness and patellofemoral arthrosis. Our preferred technique for MPFL reconstruction is designed to decrease the risk of complications associated with the aforementioned technical errors. This technique incorporates several aspects of previously described successful techniques, such as secure interference screw fixation within bone sockets and careful identification of the anatomic femoral insertion site using verified radiographic landmarks. We add suspensory adjustable-loop cortical button fixation of the looped part of the graft on the femoral side because it allows us to provisionally secure the graft in the femoral tunnel and then gradually adjust graft tension while directly (arthroscopically and with manual testing)
Table 4. Postoperative Rehabilitation A hinged knee brace is worn for 6 weeks postoperatively. Immediate weight bearing is allowed with the brace locked in extension. Range-of-motion and isometric quadriceps strengthening is started immediately. Sports training is initiated after 3 months. Unrestricted sports participation is allowed after 6 months as long as the patient has a pain-free knee, with full range of motion, normal patellar stability, and quadriceps strength that is at least 80% of that on the normal side.
checking the stability and patellofemoral alignment; moreover, it allows readjustment of tension after cycling the knee. Final fixation with an interference screw at the femoral tunnel aperture is performed only after appropriate tension is confirmed. In conclusion, MPFL reconstruction with a free semitendinosus graft using a suspensory adjustable-loop cortical button and interference screw fixation on the femoral side, as well as knotless suture anchor fixation in 2 bone sockets on the patellar side, is a reproducible technique for patellar stabilization in patients with acute or recurrent instability.
References 1. Dejour H, Walch G, Nove-Josserand L, Guier C. Factors of patellar instability: An anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 1994;2:19-26. 2. Schöttle PB, Schmeling A, Rosenstiel N, Weiler A. Radiographic landmarks for femoral tunnel placement in medial patellofemoral ligament reconstruction. Am J Sports Med 2007;35:801-804. 3. Desio SM, Burks RT, Bachus KN. Soft tissue restraints to lateral patellar translation in the human knee. Am J Sports Med 1998;26:59-65. 4. Conlan T, Garth WP Jr, Lemons JE. Evaluation of the medial soft-tissue restraints of the extensor mechanism of the knee. J Bone Joint Surg Am 1993;75:682-693. 5. Hautamaa PV, Fithian DC, Kaufman KR, Daniel DM, Pohlmeyer AM. Medial soft tissue restraints in lateral patellar instability and repair. Clin Orthop Relat Res 1998;349:174-182. 6. Senavongse W, Amis AA. The effects of articular, retinacular, or muscular deficiencies on patellofemoral joint stability: A biomechanical study in vitro. J Bone Joint Surg Br 2005;87:577-582. 7. Sallay PI, Poggi J, Speer KP, Garrett WE. Acute dislocation of the patella. A correlative pathoanatomic study. Am J Sports Med 1996;24:52-60. 8. Nomura E. Classification of lesions of the medial patellofemoral ligament in patellar dislocation. Int Orthop 1999;23:260-263.
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9. Burks RT, Desio SM, Bachus KN, Tyson L, Springer K. Biomechanical evaluation of lateral patellar dislocations. Am J Knee Surg 1998;11:24-31. 10. Ellera Gomes JL. Medial patellofemoral ligament reconstruction for recurrent dislocation of the patella: A preliminary report. Arthroscopy 1992;8:335-340. 11. Buckens CF, Saris DB. Reconstruction of the medial patellofemoral ligament for treatment of patellofemoral instability: A systematic review. Am J Sports Med 2010;38:181-188. 12. Nomura E, Inoue M, Kobayashi S. Long-term follow-up and knee osteoarthritis change after medial patellofemoral ligament reconstruction for recurrent patellar dislocation. Am J Sports Med 2007;35:1851-1858. 13. Drez D Jr, Edwards TB, Williams CS. Results of medial patellofemoral ligament reconstruction in the treatment of patellar dislocation. Arthroscopy 2001;17:298-306. 14. Schöttle PB, Fucentese SF, Romero J. Clinical and radiological outcome of medial patellofemoral ligament reconstruction with a semitendinosus autograft for patella instability. Knee Surg Sports Traumatol Arthrosc 2005;13:516-521. 15. Nomura E, Horiuchi Y, Kihara M. A mid-term follow-up of medial patellofemoral ligament reconstruction using an artificial ligament for recurrent patellar dislocation. Knee 2000;7:211-215. 16. Ellera Gomes JL, Stigler Marczyk LR, César de César P, Jungblut CF. Medial patellofemoral ligament reconstruction with semitendinosus autograft for chronic patellar instability: A follow-up study. Arthroscopy 2004;20:147-151. 17. Steiner TM, Torga-Spak R, Teitge RA. Medial patellofemoral ligament reconstruction in patients with lateral
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patellar instability and trochlear dysplasia. Am J Sports Med 2006;34:1254-1261. Smith TO, Walker J, Russell N. Outcomes of medial patellofemoral ligament reconstruction for patellar instability: A systematic review. Knee Surg Sports Traumatol Arthrosc 2007;15:1301-1314. Kang H, Cao J, Yu D, Zheng Z, Wang F. Comparison of 2 different techniques for anatomic reconstruction of the medial patellofemoral ligament: A prospective randomized study. Am J Sports Med 2013;41:1013-1021. Wang CH, Ma LF, Zhou JW, et al. Double-bundle anatomical versus single-bundle isometric medial patellofemoral ligament reconstruction for patellar dislocation. Int Orthop 2013;37:617-624. Shah JN, Howard JS, Flanigan DC, Brophy RH, Carey JL, Lattermann C. A systematic review of complications and failures associated with medial patellofemoral ligament reconstruction for recurrent patellar dislocation. Am J Sports Med 2012;40:1916-1923. Parikh SN, Nathan ST, Wall EJ, Eismann EA. Complications of medial patellofemoral ligament reconstruction in young patients. Am J Sports Med 2013;41:1030-1038. Beck P, Brown NA, Greis PE, Burks RT. Patellofemoral contact pressures and lateral patellar translation after medial patellofemoral ligament reconstruction. Am J Sports Med 2007;35:1557-1563. Elias JJ, Cosgarea AJ. Technical errors during medial patellofemoral ligament reconstruction could overload medial patellofemoral cartilage: A computational analysis. Am J Sports Med 2006;34:1478-1485.
Abstract: Medial patellofemoral ligament (MPFL) reconstruction is a reliable surgical method for stabilizing a dislocating patella, with multiple techniques previously described. Although outcomes are generally favorable, the procedure is technically demanding and relies on precise identification of native MPFL insertion sites, secure fixation of the graft to these sites, and appropriate graft tension. We describe a technique for MPFL reconstruction with a looped semitendinosus tendon. The 2 free limbs of the graft are secured into blind-end patellar sockets with knotless anchors, and the looped end is initially secured into a medial femoral socket with a button on the opposite (lateral) cortex. Use of an adjustable-loop button allows for gradual adjustment of graft tension, as well as re-tensioning after cycling of the knee, before final aperture fixation on the femur with an interference screw.
M
ultiple techniques for reconstruction of the medial patellofemoral ligament (MPFL) have been described, but no single “gold standard” exists. Despite the variations in techniques, however, certain principles have been identified as being of importance to every reconstruction. These principles include (1) graft selection, (2) identification of anatomic insertion sites of the MPFL on the femur and the patella, (3) secure fixation of the graft to these sites, and (4) appropriate adjustment of graft tension. We present a surgical technique for MPFL reconstruction with a doubled semitendinosus tendon, using knotless suture anchor fixation of the free ends to the patella, as well as hybrid femoral fixation consisting of an adjustable-loop cortical button and an interference screw. The use of an adjustable-loop button system allows gradual tensioning that can be checked with direct arthroscopic visualization and readjusted after cycling of the knee.
From New York Hospital Queens, Flushing, New York, U.S.A. The authors report the following potential conflict of interest or source of funding: A.G. has received support from Arthrex for a presentation unrelated to this manuscript. J.E.R. receives support from Ferring Pharmaceuticals. Received May 24, 2013; accepted October 28, 2013. Address correspondence to Alexander Golant, M.D., 163-03 Horace Harding Expressway, Fourth Floor, Fresh Meadows, NY 11365, U.S.A. E-mail: [email protected] Ó 2014 by the Arthroscopy Association of North America 2212-6287/13343/$36.00 http://dx.doi.org/10.1016/j.eats.2013.10.001
Preoperative Evaluation Preoperative imaging, in addition to anteroposterior and lateral radiographs of the affected knee, should include bilateral sunrise views on the same cassette to assess for differences in static alignment and tilt of the patella; this helps to determine the need for a lateral release (Table 1). Magnetic resonance imaging is obtained to evaluate articular cartilage injury, localize loose fragments, and rule out concomitant injuries to the menisci and ligaments. The tibial tubercleetoetrochlear groove distance should be calculated and is useful for predicting the need for a tibial tubercle transfer.1
Surgical Technique We prefer to use general anesthesia and a femoral nerve block for the surgical procedure. The patient is positioned supine. An examination with the patient under anesthesia is performed first, including comparison with the contralateral side. An intravenous antibiotic is administered before incision. Arthroscopy is performed next and should include documentation of any patellofemoral dysplasia (Tables 2 and 3). Lateral retinacular release may be performed as necessary for significant lateral tilt, but we do not routinely perform it for instability. Additional procedures may include loose body removal and debridement and microfracture of osteochondral lesions, as well as procedures for torn menisci. After completion of arthroscopy, the tourniquet is inflated. If an autograft is to be used, the semitendinosus
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Table 1. Preoperative Radiographic Evaluation
Table 3. Surgical Technique: Tips and Tricks
Obtain AP, lateral, and sunrise radiographs of the affected knee (this should include bilateral sunrise views on the same cassette to assess for differences in static alignment and tilt). Perform MRI to evaluate the condition of the MPFL and identify other intra-articular pathology (articular cartilage injury, osteochondral fragments, meniscus and ligament injuries). Perform MRI or a CT scan to calculate the TT-TG distance. A TT-TG value >20 mm is a relative indication for medialization of the tibial tubercle.
Mark all incisions before starting the procedure (because once the knee is swollen after the knee arthroscopy, the anatomic landmarks may be hard to palpate). Place a bump under the ipsilateral hip to ensure that the patella is facing up. Place a foam wedge or a sterile bump under the knee on the operative side to help obtain a perfect lateral fluoroscopic image. Load the Biomet ToggleLoc device onto the graft after insertion of the first SwiveLock anchor but before securing the second anchor. Aim the femoral tunnel guidewire (beath pin) slightly anteriorly to avoid injury to the posterior neurovascular structures. Make the femoral tunnel as long as possible (without violating the lateral cortex) to prevent the graft from bottoming out (before attaining the required tension). Make sure to verify the isometry of the planned reconstruction before reaming the femoral tunnel, when the position of the beath pin can still be changed if necessary. Confirm with fluoroscopy that the ToggleLoc button is properly flipped on the lateral femoral cortex. Preload the nitinol wire (for the interference screw) into the femoral tunnel before withdrawing the beath pin (for ease of tunnel localization).
Abbreviations: AP, anteroposterior; CT, computed tomography; MRI, magnetic resonance imaging; TT-TG, tibial tubercle-to-trochlear groove.
tendon is harvested through a 1-inch oblique incision directly over the pes anserinus. The graft is trimmed to be 18 to 20 cm long (9 to 10 cm folded on itself), and 2.5 cm of each end is whip-stitched with a No. 2 braided suture. The graft is then pre-tensioned (Video 1). Table 2. Surgical Technique: Step by Step Perform arthroscopy first. Harvest and prepare the semitendinosus tendon (total length of 18 to 20 cm, 4.5 mm single stranded, 6-mm tunnel folded). Expose the proximal half of the medial patellar facet (superficial to the joint capsule). Drill two 3.2-mm guidewires into the medial patella, at least 1.5 cm apart. Confirm the position using fluoroscopy. Use arthroscopy to confirm that there is no joint penetration. Over-ream the guidewires with a 4.5-mm reamer to a depth of 20 to 25 mm. Load the graft into the ToggleLoc loop. Secure the free ends into the patellar sockets with 2 SwiveLock 4.75-mm knotless anchors. Locate the femoral insertion of the MPFL with an Arthrex radiodense template (bump under the knee, perfect lateral image on fluoroscopy). Drill a beath pin percutaneously into the medial femoral condyle through this template. Dissect down to the medial femoral condyle over the beath pin. Develop the correct tissue plane (second layer of the medial knee) from the patella to the femur. Shuttle the sutures from the SwiveLock anchors to the femoral pin, and wrap them around the pin under tension. Take the knee through a range of motion to assess the isometry of the planned reconstruction. Reposition the beath pin if necessary. Ream a 6-mm blind femoral tunnel over the beath pin; do not violate the lateral cortex. Pass the graft and ToggleLoc device from the patella to the femur. Preload the nitinol wire into the femoral tunnel. Withdraw the beath pin through the lateral side of the knee, with the leading suture for the ToggleLoc device. Now, pass the ToggleLoc button through the tunnel and flip it on the lateral femoral cortex (confirm with fluoroscopy). With the knee flexed 20 to 30 , draw the graft loop into the femoral tunnel (pull on the tensioning suture of the ToggleLoc) and set the desired tension. Make sure not to overtighten or produce excessive medialization of the patella. Directly observe the patellofemoral articulation during this process with an arthroscope. Cycle the knee through a full range of motion, and adjust graft tension as necessary. Insert a 6 23emm interference screw into the femoral tunnel over the preloaded nitinol wire, flush with the condyle. Remove the wire, and cut the ToggleLoc tensioning sutures. Perform closure in layers.
A 2-incision technique is used to access the patellar and femoral insertion sites of the MPFL. A 3- to 4-cm longitudinal incision is made over the medial border of the patella, and the upper half to three-quarters of the medial patellar facet is exposed, staying superficial to the joint capsule (Video 1). Under fluoroscopic imaging, two 3.2-mm guidewires are drilled into the patella from the medial facet, parallel to each other, and aiming slightly anterior to avoid penetration into the joint (Fig 1). The inferior wire is placed at or just below the half point of the patella. The superior wire is placed at least 1.5 cm proximal to ensure adequate separation between the sockets. The guidewires are over-reamed with a 4.5-mm reamer to a depth of 25 mm (Video 1). The graft is then loaded onto an adjustable suspensory fixation device (ToggleLoc; Biomet, Warsaw, IN) and secured into 2 patellar sockets with 4.75-mm knotless anchors (SwiveLock; Arthrex, Naples, FL) (Fig 2, Video 1). The femoral insertion site of the MPFL is identified with the aid of fluoroscopy. It is located on a line drawn between the medial femoral epicondyle and the adductor tubercle, approximately 2 mm anterior and 4 mm distal to the adductor tubercle. The radiographic location has been described as 1 mm anterior to the posterior femoral cortex extension line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the level of the posterior point of the Blumensaat line on a perfect lateral radiograph of the knee.2 A perfect lateral image of the knee is obtained, and by use of a radiodense template (Arthrex), a beath pin is percutaneously inserted and drilled into the medial femoral condyle (Fig 3, Video 1). The guidewire should not be aimed posterior or distal to avoid injury to the neurovascular structures or penetration into the
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Fig 1. (A) Guidewires are drilled into the medial facet of the patella, where the 2 free limbs of the graft will be secured. One should note the incision over the pes anserinus for harvesting of the semitendinosus tendon. (B) Fluoroscopic verification of appropriate guidewire position on anteroposterior image.
knee joint. A small (2-cm) longitudinal incision is made directly over the guidewire, and dissection is carried down to the femoral condyle (Video 1). Next, the tissue plane for passage of the graft is developed. The graft is placed into the same layer in which the native MPFL is found. Near the patella, the MPFL is often contiguous with the aponeurosis of the vastus medialis oblique, whereas near the femur, its insertion is close to that of the medial collateral ligament. By use of a blunt clamp, the appropriate layer is developed, deep to the crural fascia but superficial to the joint capsule, to connect the femoral and patellar incisions. The sutures from the patellar anchors are then passed to the femur and wrapped around the
Fig 2. The free limbs of the semitendinosus graft have been secured into the 4.5-mm sockets on the proximal half of the medial patellar facet with 2 Arthrex 4.75-mm SwiveLock anchors. One should note that the graft has been preloaded onto an adjustable-loop suspensory cortical button device (Biomet ToggleLoc).
guidewire. The knee is taken through a range of motion to assess the isometry of the sutures in early flexion, which predicts the isometry of the reconstructed ligament (Video 1). If there is significant deviation from the expected isometry, the guidewire position may be wrong and it should be repositioned. A blind femoral tunnel is then reamed over the guidewire (Fig 4). The diameter of the tunnel is determined by the folded diameter of the graft (typically 6
Fig 3. The location for the femoral insertion of the MPFL is identified with the aid of fluoroscopy and a radiodense template, and a guidewire is drilled into this spot.
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the knee in 30 of flexion, the tensioning sutures are pulled until appropriate stability is felt when one is translating the patella laterally. The knee is then cycled through a full range of motion several times, and tension is rechecked (Video 1). Arthroscopy is performed to check alignment and stability by direct visualization of the patellofemoral articulation. After the graft tension is appropriately adjusted, a nitinol wire is placed into the tunnel and a 6 23emm BioComposite screw (Arthrex) is inserted (Video 1). The tourniquet is then deflated, and the incisions are closed in layers.
Postoperative Care
Fig 4. The femoral guidewire is over-reamed with a reamer (the diameter of which matches the diameter of the graft) as far as possible across the distal femur, without violating the medial cortex. Ideally, the reamer should be stopped within 2 cm from the medial cortex.
mm). We prefer to drill the tunnel as far as possible to prevent the graft from bottoming out and to ream over the wire under fluoroscopic imaging, stopping 2 cm short of the lateral cortex (Video 1). The graft is brought through the appropriate layer to the entrance of the femoral tunnel (Fig 5); the button is passed through the tunnel and flipped on the lateral femoral cortex (Fig 6). The tensioning sutures are then pulled to draw the graft into the femoral tunnel (Video 1). At this point, the graft is already secured within the femoral tunnel, and the tension can be adjusted. With
Fig 5. The graft, along with the ToggleLoc device, has been tunneled within the second layer of the medial knee (deep to the crural fascia, superficial to the medial retinaculum) to the opening of the femoral tunnel.
Postoperatively, weight bearing is allowed with crutches and a brace locked in extension (Table 4). Range-of-motion and isometric quadriceps strengthening is initiated immediately. Use of crutches is discontinued after 2 weeks, and brace use is discontinued after 6 weeks. Sports training is initiated after 3 months, and unrestricted participation is allowed after 6 months, provided that the patient has a pain-free knee, full range of motion, normal patellar stability, and normal or near-normal quadriceps strength.
Discussion The MPFL is an important soft-tissue restraint of the patellofemoral joint, providing up to 60% of the checkrein to lateral patellar displacement at 0 to 30 , where the patella is not yet engaged in the trochlea.3,4 Sectioning of the MPFL increases lateral patellar subluxation by 50%5 and decreases the force required to translate the patella laterally by 10 mm by 50%.6 The MPFL is ruptured in as many as 90% of acute dislocations7 and is either ruptured or attenuated in almost 100% of cases of recurrent instability.8 Restoration of MPFL integrity, including its anatomic insertion sites, can restore patellofemoral tracking to normal4,5,9 and is therefore an important component of any surgical plan for patellar stabilization. Anatomic MPFL reconstruction was first described in 1992,10 and since then, it has been shown that this procedure produces excellent results in patients with patellofemoral instability, with low rates of recurrent instability, low complication rates, and good functional improvement, as well as a relatively low risk of development and progression of arthritis.10-17 Although many variations on the surgical technique for MPFL reconstruction have been described, there is no consensus with regard to the surgical approach, choice of graft, graft positioning, and fixation methods.11,18 Only a handful of studies have directly compared different surgical techniques, and they suggest that there may be better outcomes when both bundles of the MPFL are reconstructed, as compared with a single-bundle reconstruction.19,20 Otherwise, there has not emerged a single
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Fig 6. (A) Fluoroscopic anteroposterior image of final reconstruction. One should note that the button is lying directly on the medial cortex. In addition, the central position of the patella should be noted. (B) Fluoroscopic lateral image of final reconstruction. One should note the positions of the patellar and femoral tunnels, consistent with the anatomic insertions of the native MPFL.
surgical technique that has shown clear superiority over the other techniques. A significant percentage of complications associated with MPFL reconstruction occur because of technical errors.21,22 These errors typically involve improper graft position and/or tension. Recurrent instability can occur when the graft is too loose or if fixation at either the femoral or patellar side fails. Conversely, overtightening or malpositioning of the graft can lead to maltracking, stiffness, and excessive medial compressive forces.23 Malpositioning the graft and making it too short may as much as double the graft tension in flexion,24 which is likely to lead to the development of stiffness and patellofemoral arthrosis. Our preferred technique for MPFL reconstruction is designed to decrease the risk of complications associated with the aforementioned technical errors. This technique incorporates several aspects of previously described successful techniques, such as secure interference screw fixation within bone sockets and careful identification of the anatomic femoral insertion site using verified radiographic landmarks. We add suspensory adjustable-loop cortical button fixation of the looped part of the graft on the femoral side because it allows us to provisionally secure the graft in the femoral tunnel and then gradually adjust graft tension while directly (arthroscopically and with manual testing)
Table 4. Postoperative Rehabilitation A hinged knee brace is worn for 6 weeks postoperatively. Immediate weight bearing is allowed with the brace locked in extension. Range-of-motion and isometric quadriceps strengthening is started immediately. Sports training is initiated after 3 months. Unrestricted sports participation is allowed after 6 months as long as the patient has a pain-free knee, with full range of motion, normal patellar stability, and quadriceps strength that is at least 80% of that on the normal side.
checking the stability and patellofemoral alignment; moreover, it allows readjustment of tension after cycling the knee. Final fixation with an interference screw at the femoral tunnel aperture is performed only after appropriate tension is confirmed. In conclusion, MPFL reconstruction with a free semitendinosus graft using a suspensory adjustable-loop cortical button and interference screw fixation on the femoral side, as well as knotless suture anchor fixation in 2 bone sockets on the patellar side, is a reproducible technique for patellar stabilization in patients with acute or recurrent instability.
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