Isolated Patellofemoral Joint Arthroplasty: Can Preoperative Bone Scans Predict Survivorship?

Isolated patellofemoral joint arthritis has been identified in 10% of the population presenting with symptomatic knee osteoarthritis. Patient selection is important in order to improve survivorship following PF arthroplasty. The purpose of this study is to compare the use of a preoperative bone scan vs a magnetic resonance imaging (MRI) to identify the patient with isolated PF arthritis.

This is a retrospective review of 32 patients undergoing isolated PF arthroplasty for PF arthritis using the same implant design. Sixteen consecutive patients received a preoperative bone scan to confirm isolated PF arthritis. These patients were matched by age and gender to patients where an MRI was used to determine isolated PF arthritis. The bone scan cohort contained 13 females and three males with an average age of 48 years and average follow-up of 52 months. There was no significant difference in age, body mass index, follow-up, or preoperative range of motion between the groups. The MRI and bone scan results were reported by a radiologist specializing in orthopedic radiology.

Survivorship was 100% in the PF arthroplasty group selected using a preoperative bone scan. Revision surgery with conversion to TKA was required in 5 of 16 patients (31%) when an MRI was used to identify isolated PF arthritis. Revision in all patients in the MRI group was due to progression of knee arthritis in the tibial-femoral joint. There were no cases of implant-related failures.

Patellofemoral arthroplasty using a modern design implant demonstrated 100% survivorship when a preoperative bone scan was used for patient selection to confirm isolated PF arthritis. In the group where only an MRI was used, there was a 31% failure due to progression of the disease. Based on this study, we would recommend the use of a bone scan as a tool in the selection criteria for patients undergoing PF arthroplasty.