Neurovascular Structural Deviations in Patients Who Have Fused Hips: Implications for Total Hip Arthroplasty.

Background: The purpose of this study was to compare the fused and normal sides of patients who have fused hips to determine the differences in neurovascular structures and factors that increase the risk of neurovascular injury.

Methods: We evaluated 38 patients who underwent total hip arthroplasty, with a fused hip between 2003 and 2021. Excluding patients who had bilateral lesions, differences in the location of neurovascular structures were measured by comparing the fused side with the normal side. The position of neurovascular structures was measured by the distance from the acetabular rim and the shortest distance to the particular bony structure. In addition, the patient's sex, weight, body mass index cause of fused hips, estimated age of fusion onset, and preoperative range of motion were investigated to examine the correlations with neurovascular deviation and these factors.

Results: The neurovascular distances for all the measured neurovascular structures were significantly reduced on the fused side compared with the normal side. Sex-based analysis revealed that women had significantly shorter distances to the femoral neurovascular bundle than men. Although height and body weight were associated with differences in neurovascular distances, body mass index was not associated with significant differences, except for the femoral nerve distance from the nearest bone. When classified by the estimated age of fusion onset, significant differences in neurovascular distances were found between the adolescent- and adult-onset groups.

Conclusions: In patients who have fused hips, neurovascular structures are located closer to the bone than on the normal side. Moreover, patients in whom the fusion occurred before the completion of growth may exhibit a shorter neurovascular distance, thereby increasing the potential risk of direct injury during total hip arthroplasty .