Graded Association Between Preoperative Bone Mineral Density and Two-Year Postoperative Complications After Primary Total Hip and Knee Arthroplasty.
BACKGROUND Osteoporosis is a recognized risk factor for adverse events after total joint arthroplasty, whereas osteopenia is often considered a borderline or lower-risk condition. This study evaluated whether osteopenia is associated with increased two-year reoperation after primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) and whether decreasing bone mineral density (BMD) is associated with a graded postoperative risk. METHODS We retrospectively reviewed a single-center cohort of consecutive patients who underwent primary THA or TKA between 2015 and 2023 and had dual-energy X-ray absorptiometry within one year preoperatively. Patients were categorized by lowest T-score as normal (greater than -1.0), osteopenia (-1.0 to -2.5), or osteoporosis (less than -2.5). The primary outcome was reoperation within two years after surgery. The secondary outcomes included periprosthetic fracture, periprosthetic joint infection (PJI), readmission, all-cause mortality, and dislocation in the THA cohort. Aseptic loosening was reviewed descriptively as a reason for reoperation. Separate multivariable logistic regression analyses were performed for THA and TKA. RESULTS A total of 3,302 patients were included, including 1,111 THA and 2,191 TKA patients. Reoperation rates increased from 0.4% in normal BMD to 4.4% in osteopenia and 6.8% in osteoporosis after THA, and from 0.3 to 1.7 to 3.5% after TKA (all P < 0.001). In adjusted models, osteopenia and osteoporosis were associated with higher odds of reoperation after both THA and TKA compared with normal BMD. The secondary analyses showed similar graded increases in periprosthetic fracture, periprosthetic joint infection, readmission, and mortality. CONCLUSION Osteopenia was associated with increased two-year reoperation after primary THA and TKA and may represent an intermediate-risk state between normal BMD and osteoporosis. Decreasing preoperative BMD was associated with graded postoperative risk.