A case of recurrent dislocation following lumbar spine fusion in a patient with a prior dual mobility total hip arthroplasty

Lumbar spine fusion alters spinopelvic mechanics. As a result, patients with a total hip arthroplasty (THA) and lumbar spine fusion (LSF) are at increased risk for hip dislocation. In efforts to reduce instability, surgeons have been recommending dual mobility constructs for hip arthroplasty. To the best of our knowledge, there are little to no reported cases of recurrent dislocation in patients who underwent a dual mobility THA followed by LSF. Such a case is discussed in this case report, along with potential explanations as to why this occurred, and how it may be prevented in the future. We report a case of a 77-year-old morbidly obese (BMI: 43.1) female who initially had a stable primary dual mobility THA for over a year, but experienced recurrent dislocation following a multi-level lumbar fusion. The patient successfully underwent a revision hip arthroplasty with a constrained liner. Instability of a dual mobility THA is a possibility following LSF. An understanding of spinopelvic biomechanics and its changes following LSF, highlight its contribution to instability in this case. The traditional Lewinnek safe zones of acetabular anteversion should be reconsidered for these patients. Certain changes in surgical technique may prevent instability.