A trochlear implant is a metal resurfacing of the groove of the trochlea to replace damaged joint cartilage there.
The patella may be left intact, or a corresponding metal and plastic implant may be used on the patella.
X-ray from the side, showing how the implant is anchored.
Avoiding total knee replacement
A trochlear implant may be indicated in the active adult where the trochlear joint cartilage is damaged but the cartilage at the ends of the rounded femoral condyles is still good. The ligaments and menisci are left intact.
Patellofemoral Arthroplasty: Current Concepts and Review of the Literature. Pisanu G, Rosso F, Bertolo C, Dettoni F, Blonna D, Bonasia DE and Rossi R. Joints. 2017 Dec; 5(4): 237–245.