Prospective comparative analysis from pre- to postoperative changes in Single Assessment Numeric Evaluation (SANE) for patellofemoral instability.

Abstract

Single Assessment Numeric Evaluation (SANE) has been introduced for the pre-operative assessment of lateral patellar instability (LPI), but post-operative evaluation is lacking. This study aimed to investigate the ability of SANE questions (SQs) to assess patients with LPI before and after surgery. 120 consecutive patients with LPIs were prospectively assessed via the Banff Patella Instability Instrument 2.0 (BPII 2.0). Patients were randomised into three groups (40 each) and asked to answer 1 of 3 SQs: "How do you rate your knee joint if a completely stable kneecap means 100%?" (SQ1), "How do you rate your knee joint if complete satisfaction means 100%?" (SQ2), "How do you rate your knee joint if complete normal function means 100%?" (SQ3). At ≥24 months post-operatively, 98 patients (81.6%) underwent reassessment with previous SQs and BPII 2.0. Post-operatively, the average BPII 2.0 was 77.7 ± 17.3 points. Mean SQ1, SQ2 and SQ3 results euqalled BPII 2.0 values and were 82.9%, 77.1% and 80.1%, respectively, without differences between groups (all <i>p</i> > 0.05). Compared with pre-operative data, post-operative correlations between BPII 2.0 and SQ1, SQ2, and SQ3 changed from high to low for SQ1 (<i>r</i> = 0.23; 95% confidence interval [CI], -0.13 to 0.53; <i>p</i> = 0.2), from low to moderate for SQ2 (<i>r</i> = 0.61; 95% CI, 0.32-0.79; <i>p</i> = 0.0003), and from low to high for SQ3 (<i>r</i> = 0.84; 95% CI, 0.70-0.92; <i>p</i> < 0.0001). 87 participants (88%) reached the patient acceptable symptom state (PASS), and 84 participants (86%) reported substantial clinical benefit (SCB). All three SANE questions reflected significant post-operative improvement consistent with BPII 2.0 outcomes. However, correlations varied from pre- to post-operative. While SQ1 previously demonstrated concurrent validity with BPII 2.0 pre-operatively, SQ3 exhibited the strongest correlation with BPII 2.0 post-operatively, warranting cautious interpretation given study limitations. Level II.