Recurrent Pediatric Patellofemoral Instability-Beyond the MPFL

Abstract

Pediatric patellofemoral instability is an increasingly common and debilitating problem. In recent years, there has been an improvement in diagnostic capabilities and greater knowledge of unique pediatric patellofemoral anatomy and pathophysiology. The spectrum of disease varies from a single traumatic dislocation, to recurrent dislocation, to obligatory dislocation in flexion or even fixed dislocation in severe or syndrome-associated cases. When treating pediatric patellofemoral instability, it is important to understand the benefits and limitations of nonoperative management. It is important to recognize the challenges imparted by the anatomy of the skeletally immature knee, specifically with regards to the physis, when considering surgical treatment. One must have a thorough understanding of common anatomic and pathophysiologic contributors to patellofemoral instability, such as coronal or axial plane malalignment, and concomitant osteochondral injury. For the very severe cases such as obligatory dislocation in flexion, special techniques may be required to achieve stability of the patellofemoral joint.

Increased tibiofemoral rotation on MRI with increasing clinical severity of patellar instability

“…Pediatric patellofemoral instability can vary in presentation from a single dislocation event to severe cases of either ixed lateral dislocation or obligatory dislocation in lexion, where every time the knee is lexed, the patella dislocates laterally 1 3 [15,19]. Fixed or obligatory dislocators have a more severe manifestation of the disease than the more standard patellofemoral instability patients who have one to several traumatic dislocations [12]. Multiple factors contribute to the pathogenesis of patellar maltracking and patellofemoral instability, including trochlear dysplasia, soft tissue integrity particularly of the medial patellofemoral ligament (MPFL), coronal alignment (genu valgum), and axial malalignment in the form of increased tibial tubercle to trochlear groove distance (TT-TG).…”

Simultaneous MPFL reconstruction and guided growth result in low rates of recurrent patellofemoral instability

“…Care must also be taken during hemiepiphysiodesis plate removal so as to avoid MPFL graft damage [3,23,29]. For tension plate removal, we recommend palpating the MPFL graft and sharp dissection proximal and distal to the graft, which facilitates plate access.…”

“…Careful consideration must be taken with tension plate fixation to avoid growth plate violation and distal femoral MPFL insertion site impingement [24]. In the technique reported here, the epiphyseal screw of the tenodesis plate is placed anterior to the MPFL femoral graft insertion site [10, 23, 32]. The planned femoral graft socket or suture anchors in our patients are aimed anteriorly and distally (away from the growth plate) at Schottle's point when securing the distal femoral aspect of the graft.…”

Treatment of Osteochondral Fractures After Acute Patellofemoral Instability

“…Chondral-only fractures may require different fixation strategies, including chondral-specific implants or suture fixation 45 . Procedures such as abrasion arthroplasty, microfracture, osteochondral autograft transplantation surgery, osteochondral allograft transplantation, autologous chondrocyte implantation, or resurfacing with particulated juvenile allograft cartilage may be utilized in the setting of unsalvageable osteochondral fractures 46 .…”

“…If the patient can successfully perform these tests with a difference of <10% between the legs for the monopodal tests, they can be allowed to resume athletic endeavors safely 24,54 . Even after clearance for return to play, patients should continue to utilize a stabilizing brace and follow an injury prevention program that includes strengthening, conditioning, and neuromuscular training 46 .…”