Degenerative Lumbar Spine Disease, Not Fusion, May Be a Risk Factor for Instability after Total Hip Arthroplasty

Dislocation rates after total hip arthroplasty (THA) in patients with fixed spinopelvic motion have been reported as high as 20%. Few studies exist specifically for lumbar spine degenerative joint disease (DJD) and its relationship to THA instability. There were two study objectives: (1) report the incidence of lumbar spine DJD and previous lumbar spine fusion and (2) evaluate the relationship of these two conditions and other potential risk factors to postoperative dislocation after THA. We retrospectively reviewed 818 consecutive THAs performed by a single surgeon utilizing a posterior approach. Comprehensive medical chart and radiographic review was performed to identify patients with lumbar spine DJD and lumbar spine fusion. Radiographic measurements, patient factors, surgical factors, and incidences of dislocation also were recorded. Eight hundred and twelve THAs were analyzed. There were 10 dislocations (1.2%, 10/812). Lumbar spine DJD and previous lumbar spine fusion occurred in 33.4% (271/812) and 5.9% (48/812) of patients, respectively. Lumbar spine DJD, acetabular protrusio, and female sex were significant predictors of dislocation using a Firth penalized maximum likelihood estimation specifically for rare events (area under receiver-operator characteristic curve = 0.91, 95% confidence interval 0.86, 0.96). Interestingly, only 2 of 10 dislocations had a previous lumbar spine fusion. Lumbar spine DJD, acetabular protrusio, and female sex were significant predictors of dislocation, while lumbar spine fusion was largely unrelated. This study used data available to most practicing surgeons and provides useful information for counseling patients preoperatively.