The Relationship Between Patient Satisfaction and the Degree of Valgus Deformity in Lateral Unicompartmental Knee Arthroplasty at a Mean 3-Year Follow-Up.

BACKGROUND

Lateral unicompartmental knee arthroplasty (LUKA) is a technically demanding procedure for isolated lateral compartment osteoarthritis, but the impact of preoperative valgus deformity severity on patient satisfaction remains unclear.

METHODS

This retrospective study analyzed 62 patients who underwent fixed-bearing LUKA, stratified by preoperative valgus angle into mild (≤ 6°, n = 35), moderate (6 to 12°, n = 16), and severe (greater than 12°, n = 11) groups. Outcomes at a mean follow-up of 35 months (range, 24 to 71 months), including radiographic alignment, Oxford Knee score, complications, and patient satisfaction, were assessed and compared.

RESULTS

At a mean follow-up of 35 months, patient satisfaction demonstrated a significant nonlinear relationship with preoperative valgus deformity severity. The moderate valgus group (6 to 12°) achieved the highest rate of "Very Satisfied" outcomes (75.0%), significantly surpassing both the mild (34.3%) and severe (9.1%) groups. Postoperative Oxford Knee scores and functional improvement were also optimal in the moderate group, while the severe group reported the lowest scores and the highest complication rate (36.4%). Radiographically, the moderate group achieved a mean postoperative valgus alignment of 5.8 ± 1.2°, which aligns with the proposed ideal range for LUKA. In contrast, the severe group exhibited under-correction (postoperative 8.0 ± 1.3° from 13.5 ± 0.6°), and the mild group trended toward potential overcorrection (postoperative 2.1 ± 1.0°). Patient-reported reasons for dissatisfaction distinctly differed: persistent pain was predominant in the mild group (56.5%), while instability dominated in the severe group (90.0%).

CONCLUSION

Moderate valgus deformity represents the optimal indication for LUKA, yielding the highest patient satisfaction. This is likely due to the achievability of ideal postoperative valgus alignment and the match between surgical reconstruction and the characteristic posterior femoral condyle wear pattern of the lateral compartment. These findings provide crucial guidance for patient selection in LUKA.