Functional and clinical outcome with modified lateral approach total hip arthroplasty in stiff hips with ankylosing spondylitis

BACKGROUND: Ankylosing spondylitis at total hip arthroplasty (THA) has significant hip stiffness with flexion deformity, restricted mobility, and function. Range of movement (ROM) improvement with good functional outcome is seen following THA in these hips. The modified Hardinge approach without abductor compromise is helpful in these stiff hips with associated flexion deformity. AIM: To assess improvement in ROM and functional outcomes with a modified lateral approach THA in ankylosing spondylitis with stiff hips. METHODS: A total of 69 hips that underwent THA with a modified Hardinge approach in 40 patients were evaluated at a mean follow-up of 38.33 mo. All individuals ambulated with weight-bearing as tolerated and ROM exercises from the 1(st )postoperative day. Modified Harris hip score and ROM were assessed during follow-up. Quality of life assessments using the 36-item and 12-item short form health surveys were done along with clinical and functional outcomes at follow-up. SPSS 22.0 was used for statistical analysis. The correlation of ROM and functional score change was performed using Pearson’s correlation coefficient. RESULTS: Sixty-nine hips with a significant decrease in ROM preoperatively with 32 clinically fused hips showed significant improvement in flexion range. The mean flexion in 69 hips improved from 29.35 ± 31.38 degrees to 102.17 ± 10.48 degrees. The mean difference of 72.82 with a P value < 0.0001 was significant. In total, 45 out of 69 hips had flexion deformity, with 13 hips having a deformity above 30 degrees. The flexion during the follow-up was below 90 degrees in 3 hips. Eleven hips had flexion of 90 degrees at follow-up, while the remaining 55 hips had flexion above 100 degrees. Modified Harris hip score improved from 17.03 ± 6.02 to 90.66 ± 7.23 (P value < 0.0001). The 36-item short form health survey at the follow-up indicated health status in 40 patients as excellent in 11, very good in 20, good in 5, fair in 3, and poor in 1. The mean mental health score was 84.10 ± 11.58. Pain relief was good in all 69 hips. Altogether, 28/40 patients (70%) had no pain, 9 patients (22%) had occasional pain, and 3 patients (8%) had mild to moderate pain with unusual activity. Heterotopic ossification was seen in 21 hips with Brooker class 1 in 14 hips. CONCLUSION: Modified Hardinge approach THA in ankylosing spondylitis with stiff hips with flexion deformity significantly improved ROM, Harris hip score, and quality of life indicated by the 36-item and 12-item short form health surveys.