Association of global sagittal spinal deformity with functional disability two years after total hip arthroplasty

The relationship between spinopelvic alignment and functional disability after total hip arthroplasty (THA) has not been fully elucidated despite the growing recognition of its importance on patient-reported outcome measures. Therefore, our aim was to assess the effect of global sagittal spinal deformity on post-operative disability.

This analysis was based on 208 cases of THA, with functional disability measured at a follow-up of 2 years. The Hip Disability and Osteoarthritis Outcome Score-Joint Replacement (HOOS-JR), ranging from a scale of 0 (complete joint disability) to 100 (perfect joint health), was used to divide eligible patients into two groups, namely with and without disability, using a score of 70 as the cut-off. The following factors were compared between the two groups using multivariate analysis: age, sex, body height, body mass index, spinopelvic parameters, and surgeon experience. To identify the cut-off value of the parameters for predicting disability (HOOS-JR < 70/100), we used the receiver-operating characteristic curve.

The disability (30 hips) and control (178 hips) groups showed a significant difference in pre-operative body height (p = 0.020), T1 pelvic angle divided by pelvic incidence (T1PA/PI; p = 0.018), PI minus lumbar lordosis (p = 0.027), post-operative HOOS-JR (p = 0.010), patient satisfaction (p = 0.033), and the modified Harris Hip Score (p = 0.038). On multivariate analysis, the following factors were associated with persistent disability: T1PA/PI > 0.2 (odds ratio [OR], 2.11; 95% confidence interval [CI], 1.19-4.14; p <  0.001) and height < 148 cm equivalent to legal standards as short stature (OR, 1.26; 95% CI, 1.09-1.48; p = 0.011). The cut-off value of pre-operative T1PA/PI was > 0.19, with a sensitivity of 95% and specificity of 85%. Post-operative satisfaction (p <  0.001), HOOS-JR (p = 0.023), and EuroQol 5-Dimension (p = 0.041) differed between the two groups when the pre-operative cut-off value was chosen as 0.2.

A T1PA/PI > 0.2 was associated with greater disability after THA. Clinicians should be aware that patient-related factors, including global spinal deformities, particularly in patients with a short stature, can influence THA outcomes at 2 years postoperatively.