High-grade trochlear dysplasia with a prominence, frequently present in lateral patellar instability, is thought to correlate with PFOA because it produces an anti-Maquet effect.24 The dysplasia provokes an increment of the patellofemoral joint pressure that could explain patellofemoral chondropathy and ultimately PFOA. In fact, 33% of patients with isolated PFOA have a history of objective patellar dislocation.24 In these cases, SDT could be considered. Several studies have examined use of this technique in the treatment of instability, but not PFOA.25 After SDT, pain resolves despite the chondral lesions being left alone (Figures 7A, 7B).
Removing the bump improves patellofemoral congruence and kinematics and reduces the patellofemoral joint reaction force; that is, overloaded areas are unloaded. SDT increases the space between the patella and the femoral trochlea and thereby reduces patellofemoral joint pressure, essentially producing a Maquet effect. These findings raise the question of whether articular cartilage is essential in the patellofemoral joint. In other words, does the patellofemoral joint really need replacing? In the patellofemoral joint, patellofemoral congruence and smooth kinematics appear to be much more important than normal articular cartilage.
Conclusion
Patellofemoral joint replacement is an option for patellofemoral pain only in very select cases. Preserving the joint is always a primary goal. As not all PFOA cases are equal, joint-preserving surgery must be tailored to the patient. The keys to success are good indication, precise surgery, proper rehabilitation, and, above all, doing only what is needed.
Am J Orthop. 2017;46(3):139-145. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.
