The goal of MPFL reconstruction is to replace the torn ligament with a graft that is stronger than the native MPFL and with a tension similar to the native ligament. Normal patellar motion allows about two patella quadrants of lateral translation.2 Graft tensioning should be performed with the knee in about 30 to 45 degrees of flexion.11,16 In addition, we use the C-arm to help locate the femoral attachment site. Schöttle et al.27 and Redfern et al.23 have described radiographic landmarks to locate the anatomic femoral position of the MPFL. The femoral attachment site is very important for achieving a good outcome.25 For example, in cadaver studies, Steensen et al.31 and Stephen et al.33 demonstrated that the position of the MPFL graft femoral attachment substantially influenced the graft length change pattern. The patellar attachment site, on the other hand, had little effect. The most common error in graft placement is to fix the graft too far anteriorly on the femur which may lead to graft laxity in extension and graft tension in flexion. This graft malposition can lead to overloading of the medial patellofemoral cartilage, anterior knee pain, and loss of flexion.4,8,35 In addition, Camp et al.6 reported that a nonanatomic MPFL femoral attachment site can result in a high rate of recurrent patellar dislocation following MPFL reconstruction. An overtightened graft combined with a lateral release can result in iatrogenic medial patellar subluxation in flexion.4 After graft fixation, knee motion should be equal to the opposite knee and there should be a good end point to lateral patellar translation from 0 to 30 degrees of knee flexion.
OUR SURGICAL TECHNIQUE IS AS FOLLOWS
Preoperative Planning
The operation should be performed with the patient under general anesthesia and in the supine position. A radiolucent operating room (OR) table (Fig. 16.3), such as the OSI flat top (Mizuho OSI, Union City, CA), is used with the C-arm positioned on the opposite side of the injured extremity. A thorough examination under anesthesia is performed to confirm incompetence of the MPFL. Lateral translation of the patella is assessed with the knee at 0 and 30 degrees of knee flexion (Fig. 16.4). Greater than 50% lateral translation of the patella is diagnostic of MPFL rupture; in the illustrated case, the patella could be completely dislocated (Fig. 16.5). Assessment of a tight lateral retinaculum is also assessed to determine the need for a lateral release.
Surgical Approach
The patient is prepped and draped in the usual sterile fashion. Perioperative antibiotics are administered. A preoperative time-out is performed. A nonsterile tourniquet is placed on the proximal thigh and inflated during the procedure. Standard diagnostic knee arthroscopy is performed, documenting any associated injuries and concomitant articular cartilage damage is graded (Fig. 16.6). Medial and lateral translation of the patella is again assessed under arthroscopy (Fig. 16.7). If it is determined, a lateral release is needed; this is performed with use of a radiofrequency ablation wand. This is performed from the 10 o’clock position (right knee), or 2 o’clock position (left knee), and extended distally until release deemed adequate. Once the arthroscopic evaluation is complete, the equipment is removed from the knee joint and the open MPFL reconstruction is performed.
Technique
A longitudinal incision is made from the superior pole of the medial patella extending 5 to 6 cm proximally (Fig. 16.8). Full-thickness flaps are developed and dissected down to the quadriceps tendon and its insertion on the patella. An Army-Navy retractor is used to retract the soft tissue, and the insertion of the VMO on the quadriceps tendon is identified (Fig. 16.9). Next, an 8- × 70-mm full-thickness graft is harvested, leaving the patellar insertion intact (Fig. 16.10). The proximal free end of the graft is sutured with a whipstitch using no. 2 Ethibond (Ethicon, Johnson & Johnson, Menlo Park, CA) suture to prepare for passage of the graft.
The knee is then flexed to about 40 degrees over a radiolucent triangle (Fig. 16.11). A 2-cm incision is made over the medial femoral epicondyle based on fluoroscopy and palpation. Fluoroscopic imaging is used to identify the MPFL insertion just distal to the femoral physis and just proximal to the posterior aspect of the femur (Fig. 16.12). Dissection is performed down to bone. A soft tissue tunnel is made using a large hemostat between the medial retinaculum and the synovium. The graft is then rotated 90 degrees medially and passed distally through the medial incision (Fig. 16.13). Next, a 2.5-mm bioabsorbable suture anchor with 3-0 FiberWire suture on a needle (Arthrex, Naples, FL) is placed at the femoral insertion (Fig. 16.14). A pilot stitch is placed to hold the tendon graft in place while the tension and patellar tracking are checked with gentle range of motion. Be sure that the patella can still be manually moved laterally about 10 mm to prevent overtensioning. The goal is to maintain the patellar tracking centrally in the trochlea without any sign of medial subluxation. The quadriceps tendon graft is then sutured in place to the medial femoral epicondyle using the FiberWire from the suture anchor, below the growth plate (Fig. 16.15). Reinforcement of the fixation is made with no. 2 Ethibond suture to the medial intermuscular septum. In addition, imbricate and attach the quadriceps tendon and medial retinaculum to the patella with no. 2 Ethibond sutures. This is done in conjunction with medial reefing of the patella to the graft with no. 2 Ethibond suture.
