Patellofemoral arthroplasty: pros, cons, and design considerations.

Patellofemoral arthroplasty is a worthy alternative to total knee arthroplasty or patellectomy in patients with arthritis localized to the anterior compartment of the knee, particularly when there is no considerable patellar malalignment or maltracking. The results can be optimized by accurately aligning the prosthesis and balancing the soft tissues to enhance patellar tracking. However, some designs are particularly vulnerable to patellofemoral complications. Postoperative patellofemoral dysfunction should be reduced by using a trochlear component that engages the patella within the trochlear groove and articulates with the patella completely in extension, but which is relatively unconstrained in extension and has a sagittal radius of curvature that fits well with the native distal femur. The incidence of patellofemoral complications was reduced in my series from 17% with a first generation implant to 4% with a second generation implant. Evolving designs likely will eliminate many of the complications of early generation implants, leaving tibiofemoral degeneration the major source of failure of patellofemoral arthroplasties.