Summary

LFPOA is not a contraindication for fixed bearing medial UKA. Patient selection utilizing a specific clinical and radiographic algorithm resulted in excellent outcomes in patients with LFPOA with a patelloplasty at a mean of 10 years. There were no differences in survivorship or outcomes when comparing patients within our control group to those with LFPOA.

Abstract

Background

Recent consensus statements have suggested that lateral facet patellar osteoarthritis (LFPOA) should be a contraindication for medial UKA due to poor postoperative functional outcomes and continued pain postoperatively. The purpose of this paper was to determine if LFPOA was related to lower survivorship or patient reported outcomes following medial UKA.

Methods

One hundred forty-four medial UKAs were performed by a single surgeon and included in the study. All patients were selected with a specific clinical and radiologic patient selection algorithm developed by the senior author. Prior to UKA, all patients underwent knee arthroscopy for research purposes. The patella was examined and the chondral damage of the patellofemoral joint including the medial and lateral patellar facets was recorded in a prospective database. LFPOA was defined as Outerbridge grade 3 or 4 of the lateral patella facet. A patelloplasty was performed in all patients. All patients completed follow-up with clinical exam at a minimum of 5 years following UKA. In addition, patients completed subjective patient-reported outcomes questionnaires to determine Patient Acceptable Symptom State (PASS) for the KOOS subscales. KOOS ADL, KOOS Sport and KOOS QOL were used based on recent psychometric analysis.

Results

One-hundred nine patients did not have LFPOA and 35 patients had LFPOA. Seven of the patients with LFPOA had isolated lateral patellar facet OA, and 28 patients had both medial and lateral patellar facet OA. Patients without LFPOA were younger than those with LFPOA (63±9 vs. 69±10 years; p=0.006) and there were more females in the LFPOA group (66%) compared to the patients without LFPOA (46%; p=0.032). No patient in the LFPOA group required conversion to TKA at mean 10-year follow-up. Four patients in the control group required conversion to TKA due to technical errors (N=2) early in the surgeon’s series and traumatic falls (N=2) during sports. There was no difference in mean survival time between the 2 groups (p=0.25). Mean survival in the control group was 9.6[95%CI:8.9-10.3] years and in the LFPOA group 10.4[95%CI:9.3-11.4] years. At mean follow-up of 10 years, there was no difference in knee flexion range of motion (without LFPOA=129°, LFPOA=130°; p=0.439) or extension (without LFPOA=0.46°, LFPOA=0.52°; p=0.886). There was also no difference in VR-12 PCS. PASS was achieved in 78% in the control group, and 81% in LFPOA group for KOOS ADL (p=0.807). PASS was achieved in 82% in the control group, and 74% in LFPOA group for KOOS Sport(p=0.441). PASS was achieved in 85% in the control group, and 88% in LFPOA group for KOOS QoL (p=0.723).

Conclusion

At a mean of 10 years, there were no differences in survivorship or outcomes when comparing patients without LFPOA versus those with LFPOA. We encourage surgeons to consider counseling patients with isolated medial compartment OA in the presence of lateral facet patella OA to proceed with a medial UKA. We believe surgeons will succeed if an accurate history is obtained that identifies an absence of pain ascending stairs in the lateral compartment that correlates with physical and radiographic examination findings.