Surgical Management of Patellofemoral Instability in the Skeletally Immature Patient

Lauren H. Redler, MD; Margaret L. Wright, MD


J Am Acad Orthop Surg. 2018;26(19):e405-e415. 

In This Article

Natural History and Risk Factors

Patellofemoral dislocation is common in the pediatric population and occurs at a rate of 29 per 100,000 patients between the ages of 10 and 17 years.[1–3] Nearly 70% of dislocations happen during sports activities or dancing.[3] Previous patellar dislocation, ligamentous laxity, open physes, and trochlear dysplasia all represent risk factors for recurrence, with rates as high as 69%.[4]

The pathoanatomy of patellofemoral instability has many factors that are challenging to modify in the skeletally immature patient. An elevated tibial tubercle to trochlear groove (TT-TG) distance creates a lateral vector that contributes to patellar instability. Because of the open apophysis, this cannot be surgically addressed with an osteotomy in the skeletally immature patient. Similarly, patella alta cannot be treated with a distalizing osteotomy because of the risk of growth arrest and recurvatum deformity. Trochlear dysplasia is the strongest individual radiographic risk factor for instability, which can be evaluated using MRI or a lateral radiograph of the knee.[5,6] Although they are gaining popularity, trochleoplasties are contraindicated in skeletally immature patients because of the risk of injury to the open distal femoral physis. In contrast, genu valgum is an important modifiable risk factor in skeletally immature patients; it may be treated with implant-mediated guided growth before skeletal maturity and can reduce the risk of future dislocations.