Preoperative Predictors of Arthroscopic Partial Meniscectomy Outcomes: The APM Index Score

Background: Preoperative risk factors contributing to poor outcomes after arthroscopic partial meniscectomy (APM) have not yet been consolidated and codified into an index scoring system used to predict APM success.Purpose: To create an index score using available preoperative factors to predict the likelihood of favorable postoperative outcomes after APM.Study Design: Case-control study; Level of evidence, 3.Methods: A consecutive cohort of patients undergoing primary APM were enrolled in this study. Patients completed pre- and postoperative patient-reported outcome measure (PROM) questionnaires that included the Knee injury and Osteoarthritis Outcome Score (KOOS), visual analog scale (VAS) for pain, Veterans RAND 12-Item Health Survey (VR-12 Physical and Mental), and Marx Activity Rating Scale (MARS). Multivariable logistic regression models were performed to evaluate independent predictors of KOOS Pain, Symptoms, and Activities of Daily Living scores and achievement of the minimal clinically important difference (MCID) and substantial clinical benefit (SCB). The authors assigned points to each variable proportional to its odds ratio, rounded to the nearest integer, to generate the index score.Results: In total, 468 patients (mean age, 49 years [SD, 10.4 years; range, 19-81 years]) were included in this study. In the univariate analysis, shorter symptom duration, lower Kellgren-Lawrence (KL) grade, lower preoperative KOOS Pain value, and lower VR-12 Physical score were associated with a higher likelihood of clinical improvement at 1 year. In the multivariable model for clinical improvement with MCID, symptom duration (<3 months: OR, 3.00 [95% CI, 1.45-6.19]; 3-6 months: OR, 2.03 [95% CI, 1.10-3.72], compared with >6 months), KL grade (grade 0: OR, 3.54 [95% CI, 1.66-7.54]; grade 1: OR, 3.04 [95% CI, 1.48-6.26]; grade 2: OR, 2.31 [95% CI, 1.02-5.27], compared with grade 3), and preoperative KOOS Pain value (score <45: OR, 3.00 [95% CI, 1.57-5.76]; score of 45-60: OR, 2.80 [95% CI, 1.47-5.35], compared with score >60) were independent significant predictors for clinical improvement. The scoring algorithm demonstrated that a higher total score predicted a higher likelihood of achieving the MCID: 0 = 40%, 1 = 68%, 2 = 80%, 3 = 89%, and 4 = 96%.Conclusion: Using this model, the authors developed an index score that, using preoperative factors, can help identify which patients will achieve clinical improvement after APM. Longer symptom duration and higher KL grade were associated with a decreased likelihood of clinical improvement as measured by KOOS Pain at 1 year postoperatively.