Proximal Femoral Cancellous Bone Density Distribution and Internal Fixation Failure in Intertrochanteric Fractures: A Radiological Study and Internally Validated Prediction Model

To investigate proximal femoral cancellous bone density distribution and its association with fixation stability in intertrochanteric fractures, and to develop and internally validate a predictive model. This retrospective study included 220 patients with intertrochanteric fractures treated with proximal femoral nail anti-rotation (PFNA). Fixation failure was defined as cutout, blade migration >5 mm, neck–shaft angle loss >10°, rotational deformity >15°, implant failure, or revision surgery. Preoperative CT Hounsfield units (HU) were measured in the femoral head, intertrochanteric region, and calcar femorale. A predictive model incorporating age, tip–apex distance (TAD), and calcar HU was internally validated using 1,000 bootstrap resamples. Fixation failure decreased across increasing density-gradient categories (P for trend = 0.037), although the overall difference was nonsignificant (P = 0.112). Age (OR = 1.17, 95% CI: 1.04–1.30), TAD (OR = 1.19, 95% CI: 1.08–1.30), and calcar HU (OR = 0.97, 95% CI: 0.95–0.98) were independently associated with failure. The model achieved an apparent AUC of 0.84 and an optimism-corrected AUC of 0.83. Lower calcar HU was independently associated with fixation failure. The combined model showed good discrimination, but external validation is needed before clinical application.