Lateral retinacular release during medial unicompartmental knee arthroplasty in the presence of patello-femoral joint arthritis relieves patello-femoral joint pressure and improves associated symptoms.

BACKGROUND: This study evaluated the effects of concomitant lateral patellar retinacular release (LPRR) during medial unicompartmental knee arthroplasty (UKA).

METHODS: We retrospectively analyzed 100 patients who had patello-femoral joint (PFJ) arthritis who underwent medial UKA with (n=50) and without (n=50) LPRR who had ≥2 years follow-up. Radiological parameters associated with lateral retinacular tightness, including patellar tilt angle (PTA), lateral patello-femoral angle (LPFA), and congruence angle, were measured. Functional evaluation was performed using the Knee Society Pain Score, Knee Society Function Score (KSFS), Kujala Score, and the Western Ontario McMaster Universities Osteoarthritis Index score. Intraoperative patello-femoral pressure evaluation was performed on 10 knees to evaluate the pressure changes before and after LPRR. Mann-Whitney U-tests were used for statistical analyses.

RESULTS: Demographic data did not differ between the LPRR(+) and LPRR(-) groups. A decrease in PTA and an increase in LPFA were observed in the LPRR(+) group compared to those in the LPRR(-) group (PTA; -0.54 vs. -1.74, P=0.002, LPFA; 0.51 vs. 2.01, P=0.010). The LPRR(+) group showed significantly better KSFS and Kujala scores than the LPRR(-) group (KSFS: 90 vs. 80, P=0.017; Kujala score: 86 vs. 79, P=0.009). Intraoperative patello-femoral pressure analysis showed a 22.6% reduction in the PFJ contact pressure and an 18.7% reduction in PFJ peak pressure after LPRR. (P=0.0015, P<0.0001, respectively) CONCLUSION: A LPRR during UKA may be a simple and useful adjunct procedure to relieve PFJ symptoms with concomitant PFJOA.