Stair Climbing Ability and Identification of the Nine Stairs Ascent and Descent Test Cut-Off Points in Hip Osteoarthritis Patients: A Retrospective Study.

Objectives As the prevalence and incidence of hip osteoarthritis (hip OA) continue to rise, measuring the impact of hip OA severity on a patient's functionality is essential. Stair walking is a particularly relevant task to assess hip OA patients, as difficulty with stair ascent is one of the driving factors in deciding to undergo a total hip arthroplasty. Although stairs tests often arise in post-arthroplasty measures, there is a lack of reported stairs performance time in hip OA patients. Therefore, this retrospective study aimed to report the stair performance time of hip OA patients categorized by disease severity and determine cut-off points that differentiate between severity grades. Materials and methods The patient selection was based on the review of de-identified data from our research laboratory database. 254 hip OA patients (aged ≥ 50 years) were divided according to the Kellgren-Lawrence classification system into three groups: Grade 2 (n=68), Grade 3 (n=109), and Grade 4 (n= 68). The stair-walking ability was evaluated using the 9S-A/D test. The time taken to ascend and descend the stairs was measured separately, and the total time (9S-A/D) was also recorded. The one-way ANOVA model, Welch test, Games-Howell posthoc test, Chi-Square tests, and Two-Way ANOVA model were used for the statistical analysis of the data. The cut-off points were obtained by receiver operating curve (ROC) analysis. The statistical significance was set at p<0.05. Results Homogeneity was found between the three groups regarding demographic and clinical characteristics, except age and gender (p<0.001). The comparison of the variables (9S-ascent, 9S-descent, and 9S-A/D) between groups, adjusted for gender and age, showed significant differences: Grade 2 individuals had shorter performance times compared to those in Grade 3 and Grade 4 (p<0.005). Simultaneously, patients with Grade 3 hip OA have a shorter performance time than those with Grade 4 hip OA (p<0.005). Regarding ROC analysis of Grade 2 versus Grade 3: The AUCs of 9S-ascend, 9S-descent, and 9S-A/D were 0.742 (95%CI 0.67-0.81), 0.734 (95%CI 0.66-0.81), and 0.745 (95%CI 0.54-0.90), respectively (all p values <0.005). The cut-off points of 9S-ascend, 9S-descent, and 9S-A/D were 8.7 s (sensitivity 56%, specificity 88%), 7.1 s (sensitivity 58%, specificity 80%), and 16.25 s (sensitivity 54%, specificity 90%), respectively. Concerning ROC analysis of Grade 3 versus Grade 4: The AUCs of 9S-ascend, 9S-descent, and 9S-A/D were 0.702 (95%CI 0.62-0.78), 0.711 (95%CI 0.63-0.79), and 0.715 (95%CI 0.64-0.80), respectively (all p values <0.005). The cut-off points of 9S-ascend, 9S-descent, and 9S-A/D were 11.5 s (sensitivity 66%, specificity 65%), 8.3 s (sensitivity 71%, specificity 62%), and 19.05 s (sensitivity 71%, specificity 61%), respectively. Conclusions The study provides evidence that the progression of hip OA affected stair walking; the performance time of 9S-ascent, 9S-ascent, and 9S-A/D tests was significantly longer as the severity of hip OA worsened. ROC analysis results show tests' ability to distinguish the cut-off point between different hip OA grades. However, further research is required for the reporting and classification of stair performance time values in hip OA patients and to further investigate the ability of 9S-ascent, 9S-descent, and 9S-A/D tests to predict the grade of hip OA.