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Objectives and questions: To determine whether cephalomedullary nail geometry—specifically nail length and CCD configuration—independently influences (i) achieving a tip–apex distance (TAD) <25 mm and (ii) early mechanical lag screw cut-out within 90 days after fixation of trochanteric femur fractures (AO/OTA 31-A1 to 31-A3) in a predominantly geriatric cohort. We further assessed contralateral CCD mismatch as a potential contributor to technical difficulty.

Material and methods: Retrospective single-centre cohort study (2018–2022). Consecutive patients with AO/OTA 31-A1 to 31-A3 fractures treated with cephalomedullary nails were analysed. Primary radiographic outcome was TAD <25 mm on immediate postoperative radiographs; primary clinical outcome was mechanical cut-out ≤90 days. Multivariable logistic regression assessed predictors of TAD <25 mm (including nail length, screw position, age, fracture type, reduction quality). Due to sparse cut-out events, Firth-penalised logistic regression was used for cut-out modelling. Time-to-event analyses applied Kaplan–Meier estimates and penalised Cox regression. Contralateral CCD and absolute CCD mismatch were evaluated when contralateral imaging was available. A predefined homogeneous subgroup (AO/OTA 31-A2, good reduction by Baumgaertner criteria, 130° nails) was analysed separately.

Results: For TAD analysis, 373 patients were eligible; for cut-out analyses 351 remained after excluding 22 in-hospital deaths. Median age was 83 years and 62.7% were female. TAD <25 mm was achieved in 313/373 (83.9%) and centre–centre screw position in 324/373 (86.9%). Early cut-out occurred in 16/351 (4.6%); no event occurred after day 65. Nail length and CCD configuration were not independently associated with TAD attainment or cut-out (e.g., nail length OR 1.27, 95% CI 0.55–2.91 for TAD <25 mm; cut-out OR 0.60, 95% CI 0.16–1.87). Centre–centre screw placement was strongly associated with TAD <25 mm (OR 14.98, 95% CI 7.35–30.54) and lower cut-out risk (OR 0.23, 95% CI 0.09–0.69). TAD <25 mm was associated with reduced cut-out (OR 0.29, 95% CI 0.11–0.86). In contralateral analyses, non-130° constructs showed greater CCD mismatch than 130° constructs, without a corresponding increase in early cut-out.

Discussion and conclusions: In this geriatric trochanteric fracture cohort, implant geometry (nail length, CCD configuration) did not independently determine TAD attainment or early mechanical cut-out. In contrast, technically modifiable factors—centre–centre screw position and achieving TAD <25 mm—were consistently associated with construct stability. Increased CCD mismatch in non-130° constructs was not linked to higher early cut-out but may still be relevant in atypical anatomies.