Effects of total hip arthroplasty on spinal sagittal alignment and static balance: a prospective study on 28 patients

The aim of this study was to investigate postoperative changes in spinal sagittal alignment and postural balance in patients with hip-spine syndrome (HSS) and to verify whether any significant correlation exists between these changes and improvement of low back pain (LBP) symptoms following total hip replacement (THR) surgery.

Twenty-eight consecutive patients with HSS undergoing unilateral THR were prospectively enrolled. Whole spine X-rays were obtained before surgery and 6 months after surgery. The following parameters were measured: cervical lordosis, thoracic kyphosis, lumbar lordosis, pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (C7 SVA). Patients underwent pre- and postoperative postural balance assessment (950-460 BioSway^TM system; clinical test of sensory integration-CTSIB, limit of stability test-LOS) and patient reported outcome measures assessment (Short Form-36, SF-36, Oswestry Disability Index, ODI, Visual Analog Scale, VAS and Western Ontario and McMaster Universities Arthritis Index, WOMAC).

Mean age of the patients was 61.7 ± 6.4. Median (interquartile range, IQR) pre-operative PI and PT were 50.0 (35.0, 60.0) and 11.0 (7.0, 23.0), respectively; lumbar lordosis was 49.0 (41.0, 68.0) and SVA 5.0 (-11.0, 41.0). No significant changes in sagittal alignment were observed postoperatively. Median LBP VAS decreased from 6.0 (5.0, 7.0) to 3.0 (2.0, 4.0) and ODI from 54.0 (39.0, 64.0) to 34.0 (26.0, 48.0) (p < 0.001). Median CTSIB improved from 1.22 (1.07, 1.45) to 1.01 (0.80, 1.19) and LOS from 46.0 (42.0, 58.0) to 37.0 (32.0, 39.0) postoperatively. No significant correlation was noted between postoperative changes in spinal sagittal alignment or postural balance and improvement of LBP VAS and ODI scores.

Our study demonstrated an improvement in LBP levels (VAS and ODI) and postural balance in patients with HSS following THR surgery. No significant changes have been noted in radiographic spinal sagittal alignment postoperatively. The improvement in LBP levels does not correlate with post-operative changes in spinopelvic alignment or postural balance.