Reconstruction of the Medial Patellofemoral Ligament With Arthroscopic Control of Patellofemoral Congruence Using Electrical Stimulation of the Quadriceps Jun Suganuma, M.D., Ryuta Mochizuki, M.D., Reo Shibata, M.D., Tadashi Sugiki, M.D., Kazuya Kitamura, M.D., Hideaki Tani, M.D., and Masaki Hasegawa, M.D.
Abstract: Reconstruction of the medial patellofemoral ligament (MPFL) for recurrent patellar dislocation provides significant improvements in knee function. However, various complications have been reported, with most attributed to incorrect positioning of anchoring sites for the reconstructed MPFL and inappropriate graft tension. Patellofemoral congruence at 30 of flexion on arthroscopy was therefore controlled using devices able to modify the length of the reconstructed MPFL. This was done under circumstances of external rotation of the knee joint and electrical stimulation of the quadriceps with the purpose of maintaining the patella in a lateral shift. Advantages of this technique include completely controllable correction on arthroscopy under the worst patellofemoral congruence induced by external rotation of the knee joint and electrical stimulation of the quadriceps at 30 of flexion of the knee joint; in other words, voluntary determination of lateral shift during arthroscopy.
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any studies have reported that reconstruction of the medial patellofemoral ligament (MPFL) to treat recurrent patellar dislocation provides significant improvements in knee function.1 However, a variety of postsurgical complications have also been reported.2-4 Most complications have been attributed to incorrect positioning of anchoring sites for the reconstructed MPFL and excessive graft tensioning.5-8 Clinical studies have proposed that the reconstructed MPFL should allow 2 to 3 patellar quadrants of translation, without overly constraining the patella.3 Patellofemoral congruence at 30 of flexion on arthroscopy was therefore controlled using a synthetic graft and devices able to change the length of the reconstructed MPFL under application of external rotation of the knee joint
From the Department of Orthopaedic Surgery, Hiratsuka City Hospital, Hiratsuka, Kanagawa, Japan. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received September 21, 2015; accepted February 4, 2016. Address correspondence to Jun Suganuma, M.D., Department of Orthopaedic Surgery, Hiratsuka City Hospital, 1-19-1 Minamihara, Hiratsuka, Kanagawa 254-0065, Japan. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 2212-6287/15914/$36.00 http://dx.doi.org/10.1016/j.eats.2016.02.022
(ER) and electrical stimulation of the quadriceps (ESQ) to keep the patella shifted laterally.
Surgical Technique The technique is described step by step as follows and shown in Video 1. Pearls and pitfalls for each step are described in Table 1. Step 1: Anesthesia General anesthesia by a laryngeal mask airway without muscle relaxants is performed. Step 2: Setup of the Video System A video camera on a tripod is set over the head of the patient. The video is relayed to a small window on the arthroscopy display in real time (picture-in-picture) using an SDC Ultra system (Stryker Endoscopy, San Jose, CA), and the findings of arthroscopy and the video are recorded simultaneously. Step 3: Setup of the Electrical Muscle Stimulation System The electrical muscle stimulation system includes an electrical muscle stimulator, controllable foot switch, bifurcated wire, and monitor lamp (M-STIM wit, PHCM100FSVR; Nihon Medix, Chiba, Japan). A wired adhesive pad (SR 5090; Sekisui Plastics, Tokyo, Japan)
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Table 1. Pearls and Pitfalls in Each Step of the Surgical Technique Step 1: Anesthesia must not interfere with electrical muscle contraction. Step 2: The video system records which direction an examined knee joint is rotated to during surgery and when ESQ is performed. Step 3: ESQ is used to examine the J-sign and keep the patella shifted as laterally and physiologically as possible. Step 4: Patellar maltracking and crepitus during motion of the knee joint in neutral, external, or internal rotation are also examined. Step 5: Feeling the extent of quadriceps contraction and delicate maneuver of the foot switch is important to control the movement of the knee joint. Step 6: The pneumatic tourniquet is not used except in steps 8-12 to allow ESQ and evaluation of the patellofemoral alignment. Step 7: This evaluation can show the worst patellofemoral congruence. ESQ should be used as briefly as possible, to avoid fatigue of the quadriceps. Step 8: If a sufficiently wide space between the second and third layers on the medial side of the knee joint is not created, the route of the graft might be distorted. Step 9: The femoral anchoring site should be determined by both palpation and fluoroscopy to make double sure. Step 10: A transverse slit of 1 cm on the medial retinaculum is used to fix the graft that takes an anterior route by passing through the slit. Step 11: The bifurcated tips of the graft tensioner must be fixed securely to the femur so that the graft cannot slip off between the tip and femur. Step 12: Surgical wires are used to pull out one end of the PT20 through the bone tunnel and both ends of the PT20 between the bifurcated tips of the graft tensioner. Step 13: Make sure that the graft pusher presses the PT20 securely and firmly to the femur, simulating final fixation of the PT20 with staples. Step 14: Adhering to the verification criteria (1-3) is essential to avoid complications. Step 15: If the verification criteria are not met, repeat the adjustment of MPFL length until the criteria are met. Step 16: If graft length adjusted to the planned maximum lateral shift is incompatible with that adjusted to the verification criteria, the verification criteria have priority. Step 17: The second staple must be tamped parallel to the first staple with a narrow interval, or late failure of fixation might result. Step 18: Final evaluation of patellofemoral congruence is important to optimize outcomes of MPFL reconstruction in the future. ESQ, electrical stimulation of the quadriceps; MPFL, medial patellofemoral ligament; PT20, 20 500 mm Poly-Tape.
is used as a proximal electrode and attached to the skin over the rectus femoris muscle, approximately 15 cm distal to the anterior superior iliac spine. A 23-gauge Cattelan needle (TOP, Tokyo, Japan) is used as a distal electrode and introduced into the center of the tendon of the rectus femoris muscle, approximately 2 cm proximal to the patella. An alligator clip (5002/ LM-IEC; Tokiwa Shoukou, Tokyo, Japan) is used to connect the wire to the Cattelan needle. An electrical current is applied as a biphasic sine curve of 50 Hz and the maximum current is limited to 66 mA. ESQ is used for 2 purposes during surgery: to extend the knee joint completely from approximately 45 flexion against gravity and to contract the quadriceps without elevating the crus against gravity. The current is usually 40 to 55 mA for the former, and usually 20 to 30 mA for the latter. ESQ during surgery is performed by an operator. Step 4: Preoperative Clinical Examination Before surgery, the knee joint is examined clinically under anesthesia. Step 5: Examination for the J-Sign ESQ is used to evaluate whether the J-sign can be detected preoperatively. Step 6: Arthroscopic Examination Arthroscopy is performed through anterolateral and anteromedial portals to rule out further intra-articular lesions in the tibiofemoral joint. The patellofemoral chondral lesions are evaluated through a proximal superomedial portal.9 The pneumatic tourniquet is not inflated during arthroscopic examination. Lactated
Ringer solution is used for irrigation of the joint. When intra-articular bleeding interferes with the arthroscopic examination, 0.5 mg of adrenaline is injected into 3000 mL of lactated Ringer solution. Step 7: Evaluation of Patellofemoral Alignment Evaluation of the patellofemoral alignment is performed through a proximal superomedial portal9 with the knee joint flexed 30 with the use of a 45 angled arthroscope. First, patellofemoral congruence is examined with neutral, external, and internal rotation of the knee joint. The same evaluation is then conducted with ESQ. Step 8: Skin Incision and Approach After the tourniquet is inflated, a longitudinal incision of approximately 2 cm is made on the skin and medial retinaculum approximately 1 cm medial to the medial border of the patella. A Kelly clamp (A-33; Yufu Itonaga, Tokyo, Japan) is then used to create a wide space between the second and third layers on the medial side of the knee joint, sufficiently over the medial epicondyle. A longitudinal posteromedial incision of approximately 4 to 5 cm is made posterior to the medial epicondyle and a small area encircled by the attachment sites of the superficial medial collateral ligament (medial epicondyle), adductor magnus tendon (adductor tubercle), and medial gastrocnemius tendon (gastrocnemius tubercle)10 is identified by palpation through the incison.11 Step 9: Determination of a Femoral Insertion Site The femoral insertion site of the MPFL (2 mm posterior to the posterior femoral cortex extension line and
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2 mm distal to the posterior femoral condyle) is identified on the true lateral view of the femoral condyles under fluoroscopic control, within the small palpated area. A Kirschner wire (K-wire) with a diameter of 1.2 mm is then inserted through the posteromedial incision to the location of the first staple fixation, 1.5 mm proximal to the insertion site of the MPFL, to position the second staple in the insertion site. Step 10: Creation of a Patellar Bone Tunnel The anchoring site of the MPFL on the patella is also marked under fluoroscopic control. A 3.2-mm-diameter bone tunnel is made transversely in the patella and a small incision is made over the lateral outlet of the bone tunnel. A transverse slit of approximately 1 cm is made in the medial retinaculum from the edge of the longitudinal incision to the medial outlet of the bone tunnel.
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second and third layers on the medial side of the knee, and between the bifurcated tips of the graft tensioner using a 0.3-mm surgical wire. The ends are then secured to the graft gripper (Figs 1 and 2B), which is mounted on the graft tensioner at this time. The tourniquet is then deflated throughout the rest of the operation. Step 13: Reduction of the Patella and Simulation of Graft Fixation By sliding the graft gripper on the graft tensioner, the patella is reduced to the planned position (Fig 3). If the lateral retinaculum is too tight, lateral retinacular release is conducted. The staple guide (Fig 1) is then mounted on the graft tensioner, and the graft pusher (Fig 1) is introduced through the slit of the staple guide so that the graft pusher presses the PT20 to the femur, simulating final fixation of the PT20 with staples (Fig 2C).
Step 11: Setup of the Graft Tensioner The graft tensioner attached to the tensioner guide (Fig 1) is introduced through the posteromedial incision, with the 1.2-mm K-wire inserted into the guide tunnel of the tensioner guide and fixed to the femur with 2 K-wires with diameters of 2.0 mm (Fig 2A). The tensioner guide is then disassembled. The 1.2-mm guide K-wire is removed and the superfluous parts of the 2.0-mm fixation K-wires are excised.
Step 14: Examination of Verification Criteria The following verification criteria are checked:
Step 12: Placement of the Graft One end of a 20 mm 500 mm Poly-Tape (PT20) (Neoligaments, Leeds, UK) is passed through the patellar bone tunnel using a 0.9-mm surgical wire. The other end is passed over the anterior surface of the patella using a Kelly clamp, deep to the anterior retinaculum, and through the slit in the medial retinaculum. Both ends of the PT20 are passed between the
Step 15: Checking Against Verification Criteria If the criteria are not met, the length of the MPFL is adjusted (usually lengthened) after removing the graft pusher from the slit. Step 14 is then repeated after mounting the graft pusher (Fig 4). If the criteria are met, the location of the patella is examined arthroscopically in 30 of flexion to verify that the patella is located in the expected position with ER and ESQ, and
(1) (2) (3)
Knee joint is extended completely by ESQ without the J-sign. Knee joint is flexed smoothly to more than 150 . No patellar maltracking occurs during motion of the knee joint in neutral, external, or internal rotation.
Fig 1. Photographs showing specially made devices used for reconstruction of the medial patellofemoral ligament. (A) From left to right: graft gripper (GG), graft tensioner (GT), tensioner guide (TG), staple guide (SG), graft pusher (GP), and staple tamper (ST). The wing nut of the GG is used to fix the graft to the GG. The wing nut at the tail of the GT is used to fix the TG or SG to the GT. (B) The GT, with bifurcated tip, is fixed to the femur using 2 Kirschner wires (K-wire) with diameters of 2.0 mm. The GG is mounted to the GT to grasp and pull the graft. The 1.2-mm K-wire is introduced into the guide tunnel of the TG. The GP is introduced into the slit of the SG and fixed to the SG using the screw at the end of the GP. The ST is used to tamp a spike staple. The GP and GT have rules on the end to allow accurate operative procedures.
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Fig 2. Photographs showing how devices are used on the medial side of the left knee joint. (A) The graft tensioner attached to the tensioner guide is introduced through the posteromedial incision, with a Kirschner wire (K-wire) with a diameter of 1.2 mm inserted into the guide tunnel of the tensioner guide and fixed to the femoral insertion site of the medial patellofemoral ligament with 2 K-wires with diameters of 2.0 mm. (B) The Poly-Tape is passed between the second and third layers on the medial side of the knee, between the bifurcated tips of the graft tensioner, and secured to the graft gripper, which is mounted on the graft tensioner. (C) After the patella is reduced to the planned position by sliding the graft gripper on the graft tensioner, the staple guide is mounted on the graft tensioner, and the graft pusher is introduced through the slit of the staple guide so that the graft pusher presses the Poly-Tape to the femur, simulating final fixation of the Poly-Tape with staples.
not subluxated medially with neutral rotation of the knee joint. If necessary, the position of the patellar central ridge (PPCR) is measured following the original method (Fig 3).12 Step 16: Checking Against Planned Maximum Lateral Shift If maximum lateral shift (the worst patellofemoral congruence induced by ER and ESQ) is not as expected for the first time, the length of the MPFL is adjusted after removing the graft pusher from the slit. The recommended PPCR is 5% to 10% (Fig 3). Step 14 is then repeated after mounting the graft pusher (Fig 4). However, if the verification criteria are not met after this adjustment, the planned maximum lateral shift is abandoned and the length of the MPFL is adjusted to the verification criteria, while keeping the maximum lateral shift as close to the expected value as possible. Step 14 is then repeated (Fig 4). If the maximum lateral shift is as expected, Step 17 is performed. Step 17: Graft Fixation A spike staple is inserted into the slit of the staple guide and driven into the femur using the staple tamper (Fig 1) after removing the graft pusher from the slit. The staple guide is then dismounted. After releasing the PT20 from
the graft gripper, the graft tensioner with the staple gripper is removed en bloc. The PT20 is folded back at the staple and fixed again using another spike staple. Step 18: Final Verification and Evaluation After final verification (criteria 1 to 3), final examination of patellofemoral congruence with ER and ESQ is conducted and recorded in a still frame. After correcting image distortion of the still frame, the PPCR is measured to check whether expectations are met. The incisions are then copiously irrigated with normal saline solution. The slit of the medial retinaculum is securely sutured to fix the PT20, which runs in an anterior route, to the medial border of the patella. The incisions are then closed in layers. Postoperative Treatment Range-of-motion (ROM) exercises are initiated on the day of surgery using continuous passive motion for at least 12 hours a day for at least 7 consecutive days after surgery, with an initial range of 90 , increasing by 5 a day (Table 2). Partial weight-bearing gait, active ROM exercise without restriction of the flexion angle, and quadriceps exercise (including straight leg raising) are initiated 2 days after surgery, and full weight-bearing gait without a brace is started after 5 days, once
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Fig 3. Drawing showing how to reduce the patella to the planned position in a left knee joint viewed from the proximal direction. The patella is reduced to the planned position (upper closed arrow), which can be expressed as the position of the patellar central ridge (PPCR), by sliding the graft gripper on the graft tensioner (lower closed arrow), while the patella is shifted laterally (open arrow) by external rotation of the knee joint (ER) and electrical stimulation of the quadriceps (ESQ). The tangent touching the medial (M) and lateral (L) articular surfaces of both sides of the trochlear groove is assumed to be the x-axis. The point on the trochlear groove that is the furthest from the x-axis is considered to be the deepest point (D). The intersection of the x-axis and the line that meets the x-axis at a right angle and passes through D is assumed to be 0 on the x-coordinate, and the lateral point of tangency (L) is assumed to be 100. The intersection between the x-axis and the line that is perpendicular to the x-axis and passes the patellar central ridge (C) is designated as P. The position of P is measured as PPCR (%) on the x-coordinate.
straight leg raising is possible. Sports activity is permitted at 3 months.
Discussion Many studies have shown that both the femoral attachment site and graft tensioning are crucial factors related to reconstructing the MPFL without complications.5-8 Accurate determination of anchoring sites and optimal graft tensioning thus appears essential for satisfactory outcomes of MPFL reconstruction. However, when the patella is reduced to the strict center of the trochlea, small technical errors in femoral anchoring site or graft tensioning, which might be induced by morphological variations in anteroposterior diameter or posterior cortex curvature of the distal femoral metaphysis,13 could result in medial patellofemoral articular overload or a disturbance of deep flexion of the knee joint. Precautionary measures including a safer anchoring site and slight loosening of the graft would thus be needed to reduce the possibility of complications (Table 3).
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The described technique contains 4 precautionary measures (Table 3). First, the femoral anchoring site of the reconstructed MPFL is deviated slightly posteriorly, although still within the range of the reported area for the anchoring site,13-18 to meet the demand of patients to sit squarely after surgery. When this point is used, the distance between the patellar and femoral attachment sites gradually shortens as the knee joint bends to more than 60 of flexion, regardless of the site of patellar attachment.19 Because the patella with recurrent dislocation is most vulnerable in the first 30 of flexion,20 if the reconstructed MPFL becomes tight around 30 of flexion, laxity will be seen at more than 60 of flexion.21 Second, patellofemoral congruence at 30 of flexion on arthroscopy can be controlled under circumstances of ER and ESQ with the purpose of maintaining the patella in the maximum lateral shift. When the patella is repositioned slightly lateral to the center of the trochlea (PPCR ¼ 5% to 10%) (Fig 3), the possibility of medial patellofemoral articular overload is significantly reduced. The control of patellofemoral congruence can also reduce the potential disturbances caused by errors in the femoral anchoring site to some extent. Third, verification criteria (1 to 3) need to be met by adjusting the length of the MPFL before graft fixation. Adherence to the criteria can prevent patellar maltracking at any flexion of the knee joint, disturbance of active full extension caused by an overly short MPFL, and J-sign attributable to an excessively long MPFL, if present. Fourth, if the graft length adjusted to the planned maximum lateral shift is incompatible with that adjusted to the verification criteria, the verification criteria are given priority to avoid complications (Fig 4). Such situations occasionally occur when the patella is reduced to the strict center of the trochlea without space between the medial articular surfaces of the patella and the trochlea (PPCR ¼ 0%). Although the PT20 is used as a graft for reconstruction of the MPFL in this technique because of the ease of handling, the described precautionary measures are available regardless of the operative methods or graft materials. The important issue in arthroscopic control of patellofemoral congruence is that if the PMFL graft is slack at the time of arthroscopic examination, patellofemoral congruence cannot be evaluated accurately and consistently. Tightening the MPFL graft by shifting the patella laterally therefore seems important when evaluating congruence. Two methods are available to induce the lateral shift of the patella: external force, or ER, and ESQ. ER and ESQ were used to maintain as much physiologic and kinematic accuracy as possible with respect to the patella while confirming patellar behavior after MPFL reconstruction as well as during examination of the J-sign. Advantages of this technique (Table 3) include completely controllable correction of patellar instability
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Fig 4. Treatment algorithm showing the medial patellofemoral ligament (MPFL) reconstruction technique from step 14 to step 17. If the maximum lateral shift is not as expected with the second attempt at step 16, the procedure advances to step 17, because obtaining the planned maximum lateral shift without complications seems infeasible.
on arthroscopy under the worst patellofemoral congruence inducible by ER and ESQ at 30 of flexion of the knee joint; in other words, voluntary determination of maximum lateral shift during arthroscopy. Concerning other advantages, this technique allows examination of the J-sign using ESQ, to simulate the situation where the graft is fixed to the femur using the devices, to detect disturbance of active full extension of the knee joint caused by a too short MPFL graft, and to sit squarely after surgery. The advantages in using a synthetic graft for reconstruction of the MPFL include removing the need to sacrifice autologous tissue, strength of the graft (10 times higher than native MPFL),22 no occurrence of graft slackness, accelerated rehabilitation, and early return to sports activity. The disadvantages (Table 3) are the need for general Table 2. Postoperative Rehabilitation Day 0 Day 1 Day 2
Day 3 Day 4 Day 5
Day 6 Day 7 Month 3
ROM exercise using CPM (0 -90 ) ROM exercise using CPM (0 -95 ) for at least 12 h ROM exercise using CPM (0 -100 ) for at least 12 h Partial weight-bearing gait without a brace Active ROM exercise without restriction of flexion angle Quadriceps exercise including straight leg raising ROM exercise using CPM (0 -105 ) for at least 12 h ROM exercise using CPM (0 -110 ) for at least 12 h ROM exercise using CPM (0 -115 ) for at least 12 h Full weight-bearing gait without a brace (once straight leg raising is possible) ROM exercise using CPM (0 -120 ) for at least 12 h ROM exercise using CPM (0 -125 ) for at least 12 h Sport activity
CPM, continuous passive motion; ROM, range of motion.
anesthesia by a laryngeal mask airway without muscle relaxants, a video system, an electrical muscle stimulation system, intraoperative fluoroscopy, the operative devices to modify length of the reconstructed MPFL, and measurement of patellofemoral congruence during surgery. Various potential risks and complications must also be considered (Table 4). The PT20 usually feels slack with neutral rotation of the knee joint after reposition of the patella. However, if graft tension is found high during repositioning of the patella, caused by a tight lateral retinaculum, lateral retinacular release should be conducted to avoid the risk of late patellar fracture. Reduction of the patella to the strict center of the trochlea without space between the medial articular surfaces of the patella and trochlea, which looks like an ideal repositioning at first sight, can induce overstress on the medial patellofemoral joint. Conversely, if the reduction of the patella is insufficient, the J-sign can remain after surgery if one was present earlier. In patients with osteoporosis, anchoring the PT20 to the insertion site of the MPFL on the femoral condyle using staples can be insufficient to ensure secure fixation. In such cases, 2 longer Poly-Tapes (10 800 mm) should be used and fixed to the lateral metaphysis of the femur through a bone tunnel from the insertion site of the MPFL to the lateral metaphysis, although patellofemoral congruence then becomes impossible to control by light maneuvers such as sliding the graft gripper. When the MPFL graft is lengthened to meet the verification criteria or the planned maximum lateral shift, it is important to make sure that the graft is not
RECONSTRUCTION OF MPFL WITH ARTHROSCOPY Table 3. Key Points, Tips, Advantages, and Disadvantages Key points: Small technical errors can occur during surgery as long as morphological variation exists. Precautionary measures are therefore needed in operative techniques. Voluntary determination of the maximum lateral shift of the patella at 30 of flexion of the knee joint is available on arthroscopy. Tips: Within the range of the reported area for the femoral anchoring site, a posteriorly deviated anchoring site more easily allows full ROM of the knee joint to be gained after surgery. When the patella is repositioned slightly lateral to the center of the trochlea (PPCR ¼ 5%-10%), the possibility of medial patellofemoral articular overload is significantly reduced. The verification criteria (1-3) need to be met before graft fixation. The graft length adjusted to the verification criteria has priority over that adjusted to the planned maximum lateral shift, when incompatibility exists between these adjustments. Advantages: J-sign can be examined. Patellofemoral congruence can be measured. Voluntary determination of the maximum lateral shift of the patella is possible. The situation where the graft is fixed to the femur can be simulated. Disturbance of active full extension of the knee joint caused by a too short MPFL graft can be detected. No need to sacrifice own tissue. Strength of graft (10 times higher than the native MPFL). Accelerated rehabilitation. Early return to sports activity. Unlikelihood of disturbance of deep flexion of the knee joint after surgery. Unlikelihood of graft slackness after surgery. Disadvantages: General anesthesia without muscle relaxants is required. A video system is required. An electrical muscle stimulator and associated electrodes are required. Intraoperative fluoroscopy is required. Operative devices to modify the length of the MPFL graft are required. Measurement of patellofemoral congruence is required during surgery. MPFL, medial patellofemoral ligament; PPCR, position of the patellar central ridge; ROM, range of motion.
stuck to the surrounding tissue or the bifurcated tips of the graft tensioner. Otherwise, the reduction of the patella becomes insufficient. The second staple must be placed parallel to the first staple with a narrow interval, never touching or overlapping, or late failure of the fixation might result. If placement is not good enough, the second staple must be removed using a removal device and the PT20 should be fixed securely using a new second staple. If the posteromedial incision is located far anteriorly, devices fixed to the medial femoral condyle might pull the patella medially because of skin tension during arthroscopic examination. The incision should thus be located sufficiently posteriorly to avoid obstructing the lateral shift of the patella. On
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the other hand, if the posteromedial incision is located too far posteriorly, paresthesia of the infrapatellar region might occur after surgery. Indications for this technique (Table 4) are recurrent dislocation and subluxation of the patella. Contraindications (Table 4) include patients with habitual or permanent dislocation of the patella, severe trochlear dysplasia in which the quadriceps tendon can dislocate laterally during deep flexion of the knee joint, contraindication for electrical muscle stimulation, and a knee joint with restricted ROM. In cases with restricted ROM, the lateral shift of the patella induced by ER and ESQ is reduced and accurate evaluation of patellofemoral congruence becomes impossible. Another contraindication is the inability to raise the legs without bending the knee joints. In such cases, strenuous muscle training is mandatory before surgery so that rehabilitation can be achieved without problems. Limitations First, repositioning of the patella slightly lateral to the center of the trochlea (PPCR ¼ 5% to 10%) (Fig 3) is recommended for this technique. However, the optimal maximum lateral shift of the patella after surgery may depend on stiffness of the graft, dynamic behavior of the patella induced by ER and ESQ, anchoring sites of the reconstructed MPFL, flexion angle of the knee joint when a graft is fixed, and whether the J-sign is included among the chief complaints of the patient. Second, whether the J-sign reproduced by ESQ can substitute
Table 4. Risks, Complications, Indications, and Contraindications Potential risks and complications: High graft tension during reposition of the patella, caused by a tight lateral retinaculum, might induce late patellar fracture. Reduction of the patella to the strict center of the trochlea can induce overstress on the medial patellofemoral joint. If the reduction of the patella is insufficient, the J-sign can remain after surgery if present earlier. In patients with osteoporosis, anchoring the graft to the femur using staples can be insufficient to ensure secure fixation. When the graft is lengthened, care must be taken to ensure that the graft is not stuck to the surrounding tissue or the bifurcated tips of the graft tensioner. If the posteromedial incision is located too anteriorly, devices fixed to the femur might pull the patella medially because of skin tension. If the posteromedial incision is located too posteriorly, paresthesia of the infrapatellar region might occur after surgery. Indications: Recurrent dislocation of the patella. Recurrent subluxation of the patella. Contraindications: Habitual and permanent dislocation of the patella. Severe trochlear dysplasia. Contracture of the knee joint. Patients who cannot perform straight leg raising. Patients with contraindications for electrical muscle stimulation.
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for the natural J-sign is unknown, because ESQ differs from voluntary contraction of the quadriceps.
References 1. Howells NR, Barnett AJ, Ahearn N, Ansari A, Eldridge JD. Medial patellofemoral ligament reconstruction: A prospective outcome assessment of a large single centre series. J Bone Joint Surg Br 2012;94:1202-1208. 2. 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. 3. Tanaka MJ, Bollier MJ, Andrish JT, Fulkerson JP, Cosgarea AJ. Complications of medial patellofemoral ligament reconstruction: Common technical errors and factors for success: AAOS exhibit selection. J Bone Joint Surg Am 2012;94:e87. 4. 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. 5. Thaunat M, Erasmus PJ. Management of overtight medial patellofemoral ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2009;17:480-483. 6. 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. 7. Bollier M, Fulkerson J, Cosgarea A, Tanaka M. Technical failure of medial patellofemoral ligament reconstruction. Arthroscopy 2011;27:1153-1159. 8. Stephen JM, Kaider D, Lumpaopong P, Deehan DJ, Amis AA. The effect of femoral tunnel position and graft tension on patellar contact mechanics and kinematics after medial patellofemoral ligament reconstruction. Am J Sports Med 2014;42:364-372. 9. Schreiber SN. Proximal superomedial portal in arthroscopy of the knee. Arthroscopy 1991;7:246-251. 10. LaPrade RF, Engebretsen AH, Ly TV, Johansen S, Wentorf FA, Engebretsen L. The anatomy of the medial part of the knee. J Bone Joint Surg Am 2007;89:2000-2010. 11. Suganuma J, Mitani T, Suzuki N, et al. Reconstruction of the medial patellofemoral ligament. J Tokyo Knee Soc 1990;10:137-148 [in Japanese].
12. Suganuma J, Mochizuki R, Inoue Y, Kitamura K, Honda A. Arthroscopic evaluation of patellofemoral congruence with rotation of the knee joint and electrical stimulation of the quadriceps. Arthroscopy 2014;30: 214-221. 13. Stephen JM, Lumpaopong P, Deehan DJ, Kader D, Amis AA. The medial patellofemoral ligament: Location of femoral attachment and length change patterns resulting from anatomic and nonanatomic attachments. Am J Sports Med 2012;40:1871-1879. 14. 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. 15. Wijdicks CA, Griffith CJ, LaPrade RF, et al. Radiographic identification of the primary medial knee structures. J Bone Joint Surg Am 2009;91:521-529. 16. Redfern J, Kamath G, Burks R. Anatomical confirmation of the use of radiographic landmarks in medial patellofemoral ligament reconstruction. Am J Sports Med 2010;38: 293-297. 17. Tateishi T, Tsuchiya M, Motosugi N, et al. Graft length change and radiographic assessment of femoral drill hole position for medial patellofemoral ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2011;19:400-407. 18. Barnett AJ, Howells NR, Burston BJ, Ansari A, Clark D, Eldridge JD. Radiographic landmarks for tunnel placement in reconstruction of the medial patellofemoral ligament. Knee Surg Sports Traumatol Arthrosc 2012;20: 2380-2384. 19. Smirk C, Morris H. The anatomy and reconstruction of the medial patellofemoral ligament. Knee 2003;10:221-227. 20. Philippot R, Boyer B, Testa R, Farizon F, Moyen B. The role of the medial ligamentous structures on patellar tracking during knee flexion. Knee Surg Sports Traumatol Arthrosc 2012;20:331-336. 21. Farr J, Schepsis AA. Reconstruction of the medial patellofemoral ligament for recurrent patellar instability. J Knee Surg 2006;19:307-316. 22. Herbort M, Hoser C, Domnick C, et al. MPFL reconstruction using a quadriceps tendon graft: Part 1. Biomechanical properties of quadriceps tendon MPFL reconstruction in comparison to the intact MPFL. A human cadaveric study. Knee 2014;21:1169-1174.
Abstract: Reconstruction of the medial patellofemoral ligament (MPFL) for recurrent patellar dislocation provides significant improvements in knee function. However, various complications have been reported, with most attributed to incorrect positioning of anchoring sites for the reconstructed MPFL and inappropriate graft tension. Patellofemoral congruence at 30 of flexion on arthroscopy was therefore controlled using devices able to modify the length of the reconstructed MPFL. This was done under circumstances of external rotation of the knee joint and electrical stimulation of the quadriceps with the purpose of maintaining the patella in a lateral shift. Advantages of this technique include completely controllable correction on arthroscopy under the worst patellofemoral congruence induced by external rotation of the knee joint and electrical stimulation of the quadriceps at 30 of flexion of the knee joint; in other words, voluntary determination of lateral shift during arthroscopy.
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any studies have reported that reconstruction of the medial patellofemoral ligament (MPFL) to treat recurrent patellar dislocation provides significant improvements in knee function.1 However, a variety of postsurgical complications have also been reported.2-4 Most complications have been attributed to incorrect positioning of anchoring sites for the reconstructed MPFL and excessive graft tensioning.5-8 Clinical studies have proposed that the reconstructed MPFL should allow 2 to 3 patellar quadrants of translation, without overly constraining the patella.3 Patellofemoral congruence at 30 of flexion on arthroscopy was therefore controlled using a synthetic graft and devices able to change the length of the reconstructed MPFL under application of external rotation of the knee joint
From the Department of Orthopaedic Surgery, Hiratsuka City Hospital, Hiratsuka, Kanagawa, Japan. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received September 21, 2015; accepted February 4, 2016. Address correspondence to Jun Suganuma, M.D., Department of Orthopaedic Surgery, Hiratsuka City Hospital, 1-19-1 Minamihara, Hiratsuka, Kanagawa 254-0065, Japan. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 2212-6287/15914/$36.00 http://dx.doi.org/10.1016/j.eats.2016.02.022
(ER) and electrical stimulation of the quadriceps (ESQ) to keep the patella shifted laterally.
Surgical Technique The technique is described step by step as follows and shown in Video 1. Pearls and pitfalls for each step are described in Table 1. Step 1: Anesthesia General anesthesia by a laryngeal mask airway without muscle relaxants is performed. Step 2: Setup of the Video System A video camera on a tripod is set over the head of the patient. The video is relayed to a small window on the arthroscopy display in real time (picture-in-picture) using an SDC Ultra system (Stryker Endoscopy, San Jose, CA), and the findings of arthroscopy and the video are recorded simultaneously. Step 3: Setup of the Electrical Muscle Stimulation System The electrical muscle stimulation system includes an electrical muscle stimulator, controllable foot switch, bifurcated wire, and monitor lamp (M-STIM wit, PHCM100FSVR; Nihon Medix, Chiba, Japan). A wired adhesive pad (SR 5090; Sekisui Plastics, Tokyo, Japan)
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Table 1. Pearls and Pitfalls in Each Step of the Surgical Technique Step 1: Anesthesia must not interfere with electrical muscle contraction. Step 2: The video system records which direction an examined knee joint is rotated to during surgery and when ESQ is performed. Step 3: ESQ is used to examine the J-sign and keep the patella shifted as laterally and physiologically as possible. Step 4: Patellar maltracking and crepitus during motion of the knee joint in neutral, external, or internal rotation are also examined. Step 5: Feeling the extent of quadriceps contraction and delicate maneuver of the foot switch is important to control the movement of the knee joint. Step 6: The pneumatic tourniquet is not used except in steps 8-12 to allow ESQ and evaluation of the patellofemoral alignment. Step 7: This evaluation can show the worst patellofemoral congruence. ESQ should be used as briefly as possible, to avoid fatigue of the quadriceps. Step 8: If a sufficiently wide space between the second and third layers on the medial side of the knee joint is not created, the route of the graft might be distorted. Step 9: The femoral anchoring site should be determined by both palpation and fluoroscopy to make double sure. Step 10: A transverse slit of 1 cm on the medial retinaculum is used to fix the graft that takes an anterior route by passing through the slit. Step 11: The bifurcated tips of the graft tensioner must be fixed securely to the femur so that the graft cannot slip off between the tip and femur. Step 12: Surgical wires are used to pull out one end of the PT20 through the bone tunnel and both ends of the PT20 between the bifurcated tips of the graft tensioner. Step 13: Make sure that the graft pusher presses the PT20 securely and firmly to the femur, simulating final fixation of the PT20 with staples. Step 14: Adhering to the verification criteria (1-3) is essential to avoid complications. Step 15: If the verification criteria are not met, repeat the adjustment of MPFL length until the criteria are met. Step 16: If graft length adjusted to the planned maximum lateral shift is incompatible with that adjusted to the verification criteria, the verification criteria have priority. Step 17: The second staple must be tamped parallel to the first staple with a narrow interval, or late failure of fixation might result. Step 18: Final evaluation of patellofemoral congruence is important to optimize outcomes of MPFL reconstruction in the future. ESQ, electrical stimulation of the quadriceps; MPFL, medial patellofemoral ligament; PT20, 20 500 mm Poly-Tape.
is used as a proximal electrode and attached to the skin over the rectus femoris muscle, approximately 15 cm distal to the anterior superior iliac spine. A 23-gauge Cattelan needle (TOP, Tokyo, Japan) is used as a distal electrode and introduced into the center of the tendon of the rectus femoris muscle, approximately 2 cm proximal to the patella. An alligator clip (5002/ LM-IEC; Tokiwa Shoukou, Tokyo, Japan) is used to connect the wire to the Cattelan needle. An electrical current is applied as a biphasic sine curve of 50 Hz and the maximum current is limited to 66 mA. ESQ is used for 2 purposes during surgery: to extend the knee joint completely from approximately 45 flexion against gravity and to contract the quadriceps without elevating the crus against gravity. The current is usually 40 to 55 mA for the former, and usually 20 to 30 mA for the latter. ESQ during surgery is performed by an operator. Step 4: Preoperative Clinical Examination Before surgery, the knee joint is examined clinically under anesthesia. Step 5: Examination for the J-Sign ESQ is used to evaluate whether the J-sign can be detected preoperatively. Step 6: Arthroscopic Examination Arthroscopy is performed through anterolateral and anteromedial portals to rule out further intra-articular lesions in the tibiofemoral joint. The patellofemoral chondral lesions are evaluated through a proximal superomedial portal.9 The pneumatic tourniquet is not inflated during arthroscopic examination. Lactated
Ringer solution is used for irrigation of the joint. When intra-articular bleeding interferes with the arthroscopic examination, 0.5 mg of adrenaline is injected into 3000 mL of lactated Ringer solution. Step 7: Evaluation of Patellofemoral Alignment Evaluation of the patellofemoral alignment is performed through a proximal superomedial portal9 with the knee joint flexed 30 with the use of a 45 angled arthroscope. First, patellofemoral congruence is examined with neutral, external, and internal rotation of the knee joint. The same evaluation is then conducted with ESQ. Step 8: Skin Incision and Approach After the tourniquet is inflated, a longitudinal incision of approximately 2 cm is made on the skin and medial retinaculum approximately 1 cm medial to the medial border of the patella. A Kelly clamp (A-33; Yufu Itonaga, Tokyo, Japan) is then used to create a wide space between the second and third layers on the medial side of the knee joint, sufficiently over the medial epicondyle. A longitudinal posteromedial incision of approximately 4 to 5 cm is made posterior to the medial epicondyle and a small area encircled by the attachment sites of the superficial medial collateral ligament (medial epicondyle), adductor magnus tendon (adductor tubercle), and medial gastrocnemius tendon (gastrocnemius tubercle)10 is identified by palpation through the incison.11 Step 9: Determination of a Femoral Insertion Site The femoral insertion site of the MPFL (2 mm posterior to the posterior femoral cortex extension line and
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2 mm distal to the posterior femoral condyle) is identified on the true lateral view of the femoral condyles under fluoroscopic control, within the small palpated area. A Kirschner wire (K-wire) with a diameter of 1.2 mm is then inserted through the posteromedial incision to the location of the first staple fixation, 1.5 mm proximal to the insertion site of the MPFL, to position the second staple in the insertion site. Step 10: Creation of a Patellar Bone Tunnel The anchoring site of the MPFL on the patella is also marked under fluoroscopic control. A 3.2-mm-diameter bone tunnel is made transversely in the patella and a small incision is made over the lateral outlet of the bone tunnel. A transverse slit of approximately 1 cm is made in the medial retinaculum from the edge of the longitudinal incision to the medial outlet of the bone tunnel.
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second and third layers on the medial side of the knee, and between the bifurcated tips of the graft tensioner using a 0.3-mm surgical wire. The ends are then secured to the graft gripper (Figs 1 and 2B), which is mounted on the graft tensioner at this time. The tourniquet is then deflated throughout the rest of the operation. Step 13: Reduction of the Patella and Simulation of Graft Fixation By sliding the graft gripper on the graft tensioner, the patella is reduced to the planned position (Fig 3). If the lateral retinaculum is too tight, lateral retinacular release is conducted. The staple guide (Fig 1) is then mounted on the graft tensioner, and the graft pusher (Fig 1) is introduced through the slit of the staple guide so that the graft pusher presses the PT20 to the femur, simulating final fixation of the PT20 with staples (Fig 2C).
Step 11: Setup of the Graft Tensioner The graft tensioner attached to the tensioner guide (Fig 1) is introduced through the posteromedial incision, with the 1.2-mm K-wire inserted into the guide tunnel of the tensioner guide and fixed to the femur with 2 K-wires with diameters of 2.0 mm (Fig 2A). The tensioner guide is then disassembled. The 1.2-mm guide K-wire is removed and the superfluous parts of the 2.0-mm fixation K-wires are excised.
Step 14: Examination of Verification Criteria The following verification criteria are checked:
Step 12: Placement of the Graft One end of a 20 mm 500 mm Poly-Tape (PT20) (Neoligaments, Leeds, UK) is passed through the patellar bone tunnel using a 0.9-mm surgical wire. The other end is passed over the anterior surface of the patella using a Kelly clamp, deep to the anterior retinaculum, and through the slit in the medial retinaculum. Both ends of the PT20 are passed between the
Step 15: Checking Against Verification Criteria If the criteria are not met, the length of the MPFL is adjusted (usually lengthened) after removing the graft pusher from the slit. Step 14 is then repeated after mounting the graft pusher (Fig 4). If the criteria are met, the location of the patella is examined arthroscopically in 30 of flexion to verify that the patella is located in the expected position with ER and ESQ, and
(1) (2) (3)
Knee joint is extended completely by ESQ without the J-sign. Knee joint is flexed smoothly to more than 150 . No patellar maltracking occurs during motion of the knee joint in neutral, external, or internal rotation.
Fig 1. Photographs showing specially made devices used for reconstruction of the medial patellofemoral ligament. (A) From left to right: graft gripper (GG), graft tensioner (GT), tensioner guide (TG), staple guide (SG), graft pusher (GP), and staple tamper (ST). The wing nut of the GG is used to fix the graft to the GG. The wing nut at the tail of the GT is used to fix the TG or SG to the GT. (B) The GT, with bifurcated tip, is fixed to the femur using 2 Kirschner wires (K-wire) with diameters of 2.0 mm. The GG is mounted to the GT to grasp and pull the graft. The 1.2-mm K-wire is introduced into the guide tunnel of the TG. The GP is introduced into the slit of the SG and fixed to the SG using the screw at the end of the GP. The ST is used to tamp a spike staple. The GP and GT have rules on the end to allow accurate operative procedures.
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Fig 2. Photographs showing how devices are used on the medial side of the left knee joint. (A) The graft tensioner attached to the tensioner guide is introduced through the posteromedial incision, with a Kirschner wire (K-wire) with a diameter of 1.2 mm inserted into the guide tunnel of the tensioner guide and fixed to the femoral insertion site of the medial patellofemoral ligament with 2 K-wires with diameters of 2.0 mm. (B) The Poly-Tape is passed between the second and third layers on the medial side of the knee, between the bifurcated tips of the graft tensioner, and secured to the graft gripper, which is mounted on the graft tensioner. (C) After the patella is reduced to the planned position by sliding the graft gripper on the graft tensioner, the staple guide is mounted on the graft tensioner, and the graft pusher is introduced through the slit of the staple guide so that the graft pusher presses the Poly-Tape to the femur, simulating final fixation of the Poly-Tape with staples.
not subluxated medially with neutral rotation of the knee joint. If necessary, the position of the patellar central ridge (PPCR) is measured following the original method (Fig 3).12 Step 16: Checking Against Planned Maximum Lateral Shift If maximum lateral shift (the worst patellofemoral congruence induced by ER and ESQ) is not as expected for the first time, the length of the MPFL is adjusted after removing the graft pusher from the slit. The recommended PPCR is 5% to 10% (Fig 3). Step 14 is then repeated after mounting the graft pusher (Fig 4). However, if the verification criteria are not met after this adjustment, the planned maximum lateral shift is abandoned and the length of the MPFL is adjusted to the verification criteria, while keeping the maximum lateral shift as close to the expected value as possible. Step 14 is then repeated (Fig 4). If the maximum lateral shift is as expected, Step 17 is performed. Step 17: Graft Fixation A spike staple is inserted into the slit of the staple guide and driven into the femur using the staple tamper (Fig 1) after removing the graft pusher from the slit. The staple guide is then dismounted. After releasing the PT20 from
the graft gripper, the graft tensioner with the staple gripper is removed en bloc. The PT20 is folded back at the staple and fixed again using another spike staple. Step 18: Final Verification and Evaluation After final verification (criteria 1 to 3), final examination of patellofemoral congruence with ER and ESQ is conducted and recorded in a still frame. After correcting image distortion of the still frame, the PPCR is measured to check whether expectations are met. The incisions are then copiously irrigated with normal saline solution. The slit of the medial retinaculum is securely sutured to fix the PT20, which runs in an anterior route, to the medial border of the patella. The incisions are then closed in layers. Postoperative Treatment Range-of-motion (ROM) exercises are initiated on the day of surgery using continuous passive motion for at least 12 hours a day for at least 7 consecutive days after surgery, with an initial range of 90 , increasing by 5 a day (Table 2). Partial weight-bearing gait, active ROM exercise without restriction of the flexion angle, and quadriceps exercise (including straight leg raising) are initiated 2 days after surgery, and full weight-bearing gait without a brace is started after 5 days, once
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Fig 3. Drawing showing how to reduce the patella to the planned position in a left knee joint viewed from the proximal direction. The patella is reduced to the planned position (upper closed arrow), which can be expressed as the position of the patellar central ridge (PPCR), by sliding the graft gripper on the graft tensioner (lower closed arrow), while the patella is shifted laterally (open arrow) by external rotation of the knee joint (ER) and electrical stimulation of the quadriceps (ESQ). The tangent touching the medial (M) and lateral (L) articular surfaces of both sides of the trochlear groove is assumed to be the x-axis. The point on the trochlear groove that is the furthest from the x-axis is considered to be the deepest point (D). The intersection of the x-axis and the line that meets the x-axis at a right angle and passes through D is assumed to be 0 on the x-coordinate, and the lateral point of tangency (L) is assumed to be 100. The intersection between the x-axis and the line that is perpendicular to the x-axis and passes the patellar central ridge (C) is designated as P. The position of P is measured as PPCR (%) on the x-coordinate.
straight leg raising is possible. Sports activity is permitted at 3 months.
Discussion Many studies have shown that both the femoral attachment site and graft tensioning are crucial factors related to reconstructing the MPFL without complications.5-8 Accurate determination of anchoring sites and optimal graft tensioning thus appears essential for satisfactory outcomes of MPFL reconstruction. However, when the patella is reduced to the strict center of the trochlea, small technical errors in femoral anchoring site or graft tensioning, which might be induced by morphological variations in anteroposterior diameter or posterior cortex curvature of the distal femoral metaphysis,13 could result in medial patellofemoral articular overload or a disturbance of deep flexion of the knee joint. Precautionary measures including a safer anchoring site and slight loosening of the graft would thus be needed to reduce the possibility of complications (Table 3).
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The described technique contains 4 precautionary measures (Table 3). First, the femoral anchoring site of the reconstructed MPFL is deviated slightly posteriorly, although still within the range of the reported area for the anchoring site,13-18 to meet the demand of patients to sit squarely after surgery. When this point is used, the distance between the patellar and femoral attachment sites gradually shortens as the knee joint bends to more than 60 of flexion, regardless of the site of patellar attachment.19 Because the patella with recurrent dislocation is most vulnerable in the first 30 of flexion,20 if the reconstructed MPFL becomes tight around 30 of flexion, laxity will be seen at more than 60 of flexion.21 Second, patellofemoral congruence at 30 of flexion on arthroscopy can be controlled under circumstances of ER and ESQ with the purpose of maintaining the patella in the maximum lateral shift. When the patella is repositioned slightly lateral to the center of the trochlea (PPCR ¼ 5% to 10%) (Fig 3), the possibility of medial patellofemoral articular overload is significantly reduced. The control of patellofemoral congruence can also reduce the potential disturbances caused by errors in the femoral anchoring site to some extent. Third, verification criteria (1 to 3) need to be met by adjusting the length of the MPFL before graft fixation. Adherence to the criteria can prevent patellar maltracking at any flexion of the knee joint, disturbance of active full extension caused by an overly short MPFL, and J-sign attributable to an excessively long MPFL, if present. Fourth, if the graft length adjusted to the planned maximum lateral shift is incompatible with that adjusted to the verification criteria, the verification criteria are given priority to avoid complications (Fig 4). Such situations occasionally occur when the patella is reduced to the strict center of the trochlea without space between the medial articular surfaces of the patella and the trochlea (PPCR ¼ 0%). Although the PT20 is used as a graft for reconstruction of the MPFL in this technique because of the ease of handling, the described precautionary measures are available regardless of the operative methods or graft materials. The important issue in arthroscopic control of patellofemoral congruence is that if the PMFL graft is slack at the time of arthroscopic examination, patellofemoral congruence cannot be evaluated accurately and consistently. Tightening the MPFL graft by shifting the patella laterally therefore seems important when evaluating congruence. Two methods are available to induce the lateral shift of the patella: external force, or ER, and ESQ. ER and ESQ were used to maintain as much physiologic and kinematic accuracy as possible with respect to the patella while confirming patellar behavior after MPFL reconstruction as well as during examination of the J-sign. Advantages of this technique (Table 3) include completely controllable correction of patellar instability
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Fig 4. Treatment algorithm showing the medial patellofemoral ligament (MPFL) reconstruction technique from step 14 to step 17. If the maximum lateral shift is not as expected with the second attempt at step 16, the procedure advances to step 17, because obtaining the planned maximum lateral shift without complications seems infeasible.
on arthroscopy under the worst patellofemoral congruence inducible by ER and ESQ at 30 of flexion of the knee joint; in other words, voluntary determination of maximum lateral shift during arthroscopy. Concerning other advantages, this technique allows examination of the J-sign using ESQ, to simulate the situation where the graft is fixed to the femur using the devices, to detect disturbance of active full extension of the knee joint caused by a too short MPFL graft, and to sit squarely after surgery. The advantages in using a synthetic graft for reconstruction of the MPFL include removing the need to sacrifice autologous tissue, strength of the graft (10 times higher than native MPFL),22 no occurrence of graft slackness, accelerated rehabilitation, and early return to sports activity. The disadvantages (Table 3) are the need for general Table 2. Postoperative Rehabilitation Day 0 Day 1 Day 2
Day 3 Day 4 Day 5
Day 6 Day 7 Month 3
ROM exercise using CPM (0 -90 ) ROM exercise using CPM (0 -95 ) for at least 12 h ROM exercise using CPM (0 -100 ) for at least 12 h Partial weight-bearing gait without a brace Active ROM exercise without restriction of flexion angle Quadriceps exercise including straight leg raising ROM exercise using CPM (0 -105 ) for at least 12 h ROM exercise using CPM (0 -110 ) for at least 12 h ROM exercise using CPM (0 -115 ) for at least 12 h Full weight-bearing gait without a brace (once straight leg raising is possible) ROM exercise using CPM (0 -120 ) for at least 12 h ROM exercise using CPM (0 -125 ) for at least 12 h Sport activity
CPM, continuous passive motion; ROM, range of motion.
anesthesia by a laryngeal mask airway without muscle relaxants, a video system, an electrical muscle stimulation system, intraoperative fluoroscopy, the operative devices to modify length of the reconstructed MPFL, and measurement of patellofemoral congruence during surgery. Various potential risks and complications must also be considered (Table 4). The PT20 usually feels slack with neutral rotation of the knee joint after reposition of the patella. However, if graft tension is found high during repositioning of the patella, caused by a tight lateral retinaculum, lateral retinacular release should be conducted to avoid the risk of late patellar fracture. Reduction of the patella to the strict center of the trochlea without space between the medial articular surfaces of the patella and trochlea, which looks like an ideal repositioning at first sight, can induce overstress on the medial patellofemoral joint. Conversely, if the reduction of the patella is insufficient, the J-sign can remain after surgery if one was present earlier. In patients with osteoporosis, anchoring the PT20 to the insertion site of the MPFL on the femoral condyle using staples can be insufficient to ensure secure fixation. In such cases, 2 longer Poly-Tapes (10 800 mm) should be used and fixed to the lateral metaphysis of the femur through a bone tunnel from the insertion site of the MPFL to the lateral metaphysis, although patellofemoral congruence then becomes impossible to control by light maneuvers such as sliding the graft gripper. When the MPFL graft is lengthened to meet the verification criteria or the planned maximum lateral shift, it is important to make sure that the graft is not
RECONSTRUCTION OF MPFL WITH ARTHROSCOPY Table 3. Key Points, Tips, Advantages, and Disadvantages Key points: Small technical errors can occur during surgery as long as morphological variation exists. Precautionary measures are therefore needed in operative techniques. Voluntary determination of the maximum lateral shift of the patella at 30 of flexion of the knee joint is available on arthroscopy. Tips: Within the range of the reported area for the femoral anchoring site, a posteriorly deviated anchoring site more easily allows full ROM of the knee joint to be gained after surgery. When the patella is repositioned slightly lateral to the center of the trochlea (PPCR ¼ 5%-10%), the possibility of medial patellofemoral articular overload is significantly reduced. The verification criteria (1-3) need to be met before graft fixation. The graft length adjusted to the verification criteria has priority over that adjusted to the planned maximum lateral shift, when incompatibility exists between these adjustments. Advantages: J-sign can be examined. Patellofemoral congruence can be measured. Voluntary determination of the maximum lateral shift of the patella is possible. The situation where the graft is fixed to the femur can be simulated. Disturbance of active full extension of the knee joint caused by a too short MPFL graft can be detected. No need to sacrifice own tissue. Strength of graft (10 times higher than the native MPFL). Accelerated rehabilitation. Early return to sports activity. Unlikelihood of disturbance of deep flexion of the knee joint after surgery. Unlikelihood of graft slackness after surgery. Disadvantages: General anesthesia without muscle relaxants is required. A video system is required. An electrical muscle stimulator and associated electrodes are required. Intraoperative fluoroscopy is required. Operative devices to modify the length of the MPFL graft are required. Measurement of patellofemoral congruence is required during surgery. MPFL, medial patellofemoral ligament; PPCR, position of the patellar central ridge; ROM, range of motion.
stuck to the surrounding tissue or the bifurcated tips of the graft tensioner. Otherwise, the reduction of the patella becomes insufficient. The second staple must be placed parallel to the first staple with a narrow interval, never touching or overlapping, or late failure of the fixation might result. If placement is not good enough, the second staple must be removed using a removal device and the PT20 should be fixed securely using a new second staple. If the posteromedial incision is located far anteriorly, devices fixed to the medial femoral condyle might pull the patella medially because of skin tension during arthroscopic examination. The incision should thus be located sufficiently posteriorly to avoid obstructing the lateral shift of the patella. On
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the other hand, if the posteromedial incision is located too far posteriorly, paresthesia of the infrapatellar region might occur after surgery. Indications for this technique (Table 4) are recurrent dislocation and subluxation of the patella. Contraindications (Table 4) include patients with habitual or permanent dislocation of the patella, severe trochlear dysplasia in which the quadriceps tendon can dislocate laterally during deep flexion of the knee joint, contraindication for electrical muscle stimulation, and a knee joint with restricted ROM. In cases with restricted ROM, the lateral shift of the patella induced by ER and ESQ is reduced and accurate evaluation of patellofemoral congruence becomes impossible. Another contraindication is the inability to raise the legs without bending the knee joints. In such cases, strenuous muscle training is mandatory before surgery so that rehabilitation can be achieved without problems. Limitations First, repositioning of the patella slightly lateral to the center of the trochlea (PPCR ¼ 5% to 10%) (Fig 3) is recommended for this technique. However, the optimal maximum lateral shift of the patella after surgery may depend on stiffness of the graft, dynamic behavior of the patella induced by ER and ESQ, anchoring sites of the reconstructed MPFL, flexion angle of the knee joint when a graft is fixed, and whether the J-sign is included among the chief complaints of the patient. Second, whether the J-sign reproduced by ESQ can substitute
Table 4. Risks, Complications, Indications, and Contraindications Potential risks and complications: High graft tension during reposition of the patella, caused by a tight lateral retinaculum, might induce late patellar fracture. Reduction of the patella to the strict center of the trochlea can induce overstress on the medial patellofemoral joint. If the reduction of the patella is insufficient, the J-sign can remain after surgery if present earlier. In patients with osteoporosis, anchoring the graft to the femur using staples can be insufficient to ensure secure fixation. When the graft is lengthened, care must be taken to ensure that the graft is not stuck to the surrounding tissue or the bifurcated tips of the graft tensioner. If the posteromedial incision is located too anteriorly, devices fixed to the femur might pull the patella medially because of skin tension. If the posteromedial incision is located too posteriorly, paresthesia of the infrapatellar region might occur after surgery. Indications: Recurrent dislocation of the patella. Recurrent subluxation of the patella. Contraindications: Habitual and permanent dislocation of the patella. Severe trochlear dysplasia. Contracture of the knee joint. Patients who cannot perform straight leg raising. Patients with contraindications for electrical muscle stimulation.
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for the natural J-sign is unknown, because ESQ differs from voluntary contraction of the quadriceps.
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