Robot-Assisted Patellofemoral Arthroplasty.

Background: Patellofemoral arthroplasty is indicated in patients with isolated patellofemoral arthritis in whom nonoperative treatment has failed². The goal of the presently described procedure is to provide relief from patellofemoral arthritis pain while maintaining native knee kinematics².

Description: Patient radiographs are carefully reviewed for isolated patellofemoral arthritis in order to determine the appropriateness of robotic-assisted patellofemoral arthroplasty. Magnetic resonance imaging can be performed preoperatively to help confirm isolated patellofemoral arthritis. We perform this procedure with use of the MAKO Surgical Robot (Stryker). Preoperative computed tomography is performed to plan the bone resection, the size of the implant, and the positioning of the device. The steps of the procedure include (1) medial parapatellar arthrotomy, (2) intraoperative inspection to confirm isolated patellofemoral arthritis, (3) patellar resurfacing, (4) placement of optical arrays and trochlear registration, (5) trochlear resection, (6) trialing of implants, (7) removal of the optical array, (8) impaction of final implants, (9) confirmation of appropriate patellar tracking, and (10) closure.

Alternatives: Alternatives to patellofemoral arthroplasty include standard nonoperative treatment, bicompartmental arthroplasty, total knee arthroplasty, tibial tubercle osteotomy, partial lateral facetectomy, and arthroscopy².

Rationale: Patellofemoral arthroplasty is indicated in patients with isolated patellofemoral arthritis in whom nonoperative treatment has failed². Patellofemoral arthroplasty may be superior to total knee arthroplasty because it helps treat pain that affects patient quality of life and activities of daily living while also preserving greater tibiofemoral bone stock². We recommend against performing patellofemoral arthroplasty in patients with arthritis of the tibiofemoral joints².

Expected outcomes: In properly selected patients, outcomes include improvement in patient pain and function¹. One study found that robotic-assisted patellofemoral arthroplasty may result in improved patellar tracking compared with non-robotic-assisted patellofemoral arthroplasty¹; however, functional outcomes were found to be similar between procedures, and data for all non-robotic-assisted controls were retrospectively captured¹.

Important tips: Confirm isolated patellofemoral arthritis on radiographs and/or magnetic resonance imaging.Review the preoperative plan for appropriate positioning of the trochlear implant.○ Confirm coverage of the trochlear groove.○ Avoid medial overhang.○ Avoid lateral overhang.○ Avoid anterior femoral notching.○ Avoid impingement of the trochlear component into the notch.○ Avoid excessive prominence of the trochlear component on the anterior femoral cortex.○ General principles are to place the trochlear component in 0° to 6° of flexion and 0° to 2° of external rotation.Robotic-assisted trochlear resurfacing is accurate and efficient.

Acronyms and abbreviations: CT = computed tomography.