Ankylosing spondylitis in patients undergoing total hip arthroplasty increases the risk of medical and implant-related complications: a case control analysis.

Introduction: Ankylosing spondylitis (AS) is an inflammatory spondyloarthropathy, often involving the spine and sacroiliac joints. Total hip arthroplasty (THA) has been shown to be effective in improving pain and function in patients with AS with hip involvement. However, extraskeletal manifestations and altered mechanics in those with AS leads to increased complications. Thus, the aims of this study were to assess the effects that AS has on medical and implant complications, falls, length of stay, and readmissions following THA.

Methods: A retrospective review of the Mariner private insurance claims database was conducted from 2010 to 2020. All cases of THA and those with AS were identified using Current Procedural Terminology, and International Classification of Disease 9^th and 10^th revision codes. Patients who underwent THA with a diagnosis of AS were matched to non-AS patients 1:5 based on demographic and comorbidity profiles. 90-day medical complications, falls, and readmission rates, as well as 2-year implant complications were compared between cohorts.

Results: A total of 6509 AS patients were matched to 32,489 control patients. The AS group had significantly higher rates of myocardial infarction, cerebrovascular accident, deep vein thrombosis, pulmonary embolism, urinary tract infection, wound complications, acute kidney injury, pneumonia, sepsis, transfusions, and falls when compared to the control group. The AS group had significantly higher rates of prosthetic joint infection, dislocation, mechanical loosening, and periprosthetic fracture (all p < 0.0001). Likewise, mean length of stay and readmissions were significantly greater in the AS group.

Conclusions: Ankylosing spondylitis in patients undergoing THA is associated with significant risk of medical and implant complications, as well as fall risk, length of stay, and readmission rates. These findings may allow orthopaedic surgeons to be more attentive in identifying those patients at risk and allow for more educated patient counseling and perioperative planning.