Patellofemoral Arthroplasty

Abstract

Background: The first report of patellofemoral arthroplasty (PFA) was published in 1979¹. Reviews in 2005 and 2007^2,3 called for studies comparing PFA with total knee arthroplasty (TKA) for isolated patellofemoral osteoarthritis. A blinded randomized controlled trial (RCT) was initiated in 2007 for this purpose, and the first report with 2-year results was awarded the Mark Coventry Award of the Knee Society in 2017⁴. It was found that (1) patients recover more quickly from PFA than from TKA; (2) during the first 2 years after surgery, PFA-treated patients have better average knee function than TKA-treated patients; and (3) PFA-treated patients regain their preoperative range of movement within the first postoperative year whereas TKA-treated patients do not regain it within the first 2 years⁴.

Description: There are general principles that are common to all brands of PFA implants. These include (1) an indication based on bone-on-bone contact in the patellofemoral joint with a preserved tibiofemoral joint; (2) replacing all surfaces of the patellofemoral joint, with metal on the femoral side and polyethylene on the patellar side; (3) ensuring a smooth transition from normal articular cartilage to the trochlear component; and (4) creating normal patellofemoral tracking.

Alternatives: The primary treatment of any degenerative condition should be nonoperative, but when such measures are insufficient surgical treatment may be indicated. Many procedures have been suggested for relieving patellofemoral pain, but if there is bone-on-bone contact in the patellofemoral joint, the only current surgical option (except for experimental treatments) is joint replacement-i.e., either PFA or TKA.

Rationale: Our general principle for joint replacement of the knee is to replace only the affected compartment if unicompartmental changes are found. If ≥2 compartments are affected, we perform TKA. This principle is challenged both by proponents of performing TKA in all cases of knee osteoarthritis and by proponents of bicompartmental knee replacement for 2-compartment disease. The 2-year results of our blinded RCT comparing PFA and TKA⁴ support our current practice of PFA. In our practice, we have found PFA to be a rewarding procedure when the correct indications are used. PFA is likely to remain a fairly rare procedure, but any knee arthroplasty center should be able to offer it.

Fig. 1-A

Posteroanterior view.

Fig. 1-B

Lateral view.

Fig. 1-C

Tangential view.

Fig. 2

Tangential radiograph showing severe patellofemoral osteoarthritis with longitudinal wear grooves.

Fig. 3

Position of the extremity at the start of the procedure.

Fig. 4

View of a left knee from above (the surgeon’s view). The trochlear wear is mainly in the medial part. Similarly, the patellar changes were also mainly medial. This wear pattern is unusual.

Fig. 5

Postoperative lateral radiograph of the patient shown in Figures 1-A, 1-B, and 1-C. Note that the distal part of the trochlear component extends slightly beyond the Blumensaat line.