PREFERRED SURGICAL TECHNIQUE FOR MPFL RECONSTRUCTION WITH ALLOGRAFT
Surgery should be scheduled and performed as an outpatient procedure. Preoperative instructions may include crutch training, when indicated, and postoperative education regarding expected early therapy and pain management strategy may be employed. Chlorhexidine wipes are provided to patients preoperatively with instruction to use daily starting 3 days prior to surgery. A home exercise program with a focus on quadriceps activation and range of motion is provided and requested to be performed postoperatively.
A standard operating room setup for knee arthroscopy is employed (preference list noted in Table 3; items bolded may be unique to an MPFL reconstruction). Regional, single-shot anesthesia is employed using a sensory-only adductor canal block. A universal surgical timeout is performed before beginning the surgery to include verification of prophylactic antibiotics (Ancef or clindamycin in penicillin-allergic patients) and consideration of the use of a sequential compression device in children aged >10 years when ≥1 venous thromboembolic risk factors are detected in preoperative screening.
Nonirradiated allografts (semitendinosus or tibialis anterior), preferably from a donor <30 years, are our preferred graft choice. The minimum length of the graft should be 240 mm and the doubled thickness should be 5 to 6 mm. After thawing, the graft is lavaged with a mixture of antibiotic saline consisting of 50,000 U of bacitracin in 1 l of normal saline. Tension is then placed on the graft using the graft preparation board, and a whip stitch is placed on each side of the graft using a #2 FiberWire (Arthrex). The graft is sized with care to ensure that it is not thicker than 6.5 mm with an optimal goal of 6 mm.
A standard knee arthroscopy is performed with an emphasis on evaluating the patellofemoral anatomy. Although insufflation can cause distortion and, often, lateralize the patella, the surgeon should consider an estimate of when the patella engages the trochlea during knee flexion. This position of knee flexion will determine the appropriate position of the knee during graft fixation. A bipolar device (90°Arthrocare wand) may be used to debride synovial folds (ie, plica) when affecting the patellar tracking. To maximize visualization of the patella within the knee, we recommend switching the arthroscope from the anterolateral portal to the anteromedial portal. This allows for improved visualization of the lateral femoral condyle and the inferomedial patellar facet, common locations for chondral and osteochondral damage, as well as optimal visualization of patellar engagement within the trochlea. During an arthroscopic dynamic exam of the patella tracking, a lateralized patella may be observed. If the patella tilts upon manual medial translation toward the trochlear groove during the dynamic exam, the lateral retinaculum may be tight or constraining the patella laterally. If this occurs, a partial or complete lateral release may be indicated with a bipolar wand. Visualization of the posteromedial and the posterolateral compartments is required as loose chondral bodies may be present in these locations.
Any osteochondral or chondral injuries are addressed during the arthroscopy. Large osteochondral fractures of the lateral femoral condyle or the patella are repaired using headless compression screws (Acutrak Screws, Acumed) or headed low-profile screws (1.5-mm screws, DePuy Synthes). Headless screws can be buried 2 to 3 mm below the chondral surface when the fragment has an appropriate thickness, whereas thin fragments may necessitate headed screws for adequate fixation and subsequent implant removal in 8 to 10 weeks. Defects in the patella most often require an open arthrotomy to evert the patella 90° to allow adequate exposure for treatment. Chronic chondral fragmentation may be debrided using the motorized chondrotome or removed and indicated for microfracture (<2 cm2 in surface area and <4 mm in depth) or other types of chondral replacement. Chondral lesions over the inferior medial facet are typically not symptomatic and often require minimal treatment.
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