Trochleoplasty for Chronic Patellofemoral Instability

Patellar instability or maltracking symptoms are a typical problem in orthopedic surgery. They are caused by an interaction between different factors controlling the movement and the stability of the patella. There is an interplay between the active muscle tension (active stabilizers), passive tension in the retinacular structures (passive stabilizers), and the reactive forces on the articular surfaces (static stabilizers). Hence, the patellofemoral joint articular geometry is an important factor in chronic patellofemoral instability. A deficient lateral trochlear slope, a malaligned trochlear groove, and a reduced trochlear depth can cause patella subluxation in extension or early flexion. Surgical interventions addressing the passive or active stabilizers may not be able to stabilize the patellofemoral joint in those cases because they do not address the underlying pathology. Since 1915, few surgical techniques were described to correct trochlear dysplasia by either elevating the lateral trochlear facet or by deepening the trochlear depth, both increasing the lateral trochlear slope. With the technique presented here, it is possible to shape a new trochlea according to the physiological trochlea geometry without increasing the patellofemoral pressure. We describe indications for surgery, the surgical technique and radiological as well as clinical results of our patient population. We conclude that trochleoplasty is not a salvage procedure, but the primary surgical intervention for chronic patellar instability in the presence of a significant trochlear dysplasia, as it addresses the underlying pathological anatomical geometry.