Functional and Clinical Outcome With Modified Lateral Approach Total Hip Arthroplasty in Stiff Hips With Ankylosing Spondylitis 

Abstract Background Ankylosing spondylitis at THA have significant hip stiffness with flexion deformity and restricted function. ROM (range of movement) improvement with good functional outcome is seen following THA with modified lateral approach in these hips.Methods 69hips who underwent THA with a modified Hardinge approach in 40patients were evaluated at a mean follow up of 38.33 months (0 to 83 months). Modified Harris hip score, ROM (range of movement), and SF 36 scores were used to assess clinical and functional improvement at review. Results 69 hips with significant decrease in ROM preoperatively with 32 clinically fused hips showed significant improvement in the range of flexion. The mean flexion in 69 hips improved from 29.35 (SD 31.38) to 102.17 degrees (SD10.48). The mean difference of 72.82 with p Value <0.0001 was found to be significant. 45 /69 hips had fixed flexion deformity with 13 hips having a deformity above 30 degrees. The flexion at review was below 90 degrees in 3 hips. Eleven hips had flexion of 90 degrees at review while the remaining 55 hips had flexion above 100 degrees. Modified HHS improved from 17.03(SD 6.02) to 90.66 (SD7.23). SF 36 at review indicated health status in 40 patients as excellent in 11, very good in 20, fair in 3 and poor in 1. Mean mental health score was 84.10(SD11.58)Conclusion Our study suggests that modified lateral approach THA in AS with stiff hips achieves significant improvement in ROM, HHS and quality of life indicated by SF12 and SF36 scores. Modified lateral approach is useful especially in fused AS hips with flexion deformity.