Objectives: To evaluate the variability of the ideal trochanteric starting point as a possible cause for malreduction of subtrochanteric fractures and to analyze the accuracy of contralateral templating to predict correct entry site.
Methods: Standardized anteroposterior pelvis radiographs of 50 patients were evaluated by two independent reviewers. Patients with advanced osteoarthritis, severe hip deformity, and radiographs with asymmetric hip rotation were excluded. Ideal nail entry site was established using a template for a trochanteric nail with a 6° proximal bend. The distance from the greater trochanteric tip to the ideal nail entry site was measured. Additionally, offset of the greater trochanter tip from the femoral longitudinal axis was measured. Interobserver reliability and accuracy of contralateral templating were evaluated.
Results: The ideal entry point ranged from 16 mm medial to 8 mm lateral to the trochanteric tip (mean, 3 mm medial; standard deviation, 5 mm). In 70% of patients, the ideal entry point was medial to and in 23% lateral to the tip of the greater trochanter. Ideal entry points were located within 2 mm of the trochanteric tip in 29% and within 4 mm in 44% of patients. The location of the ideal entry point relative to the trochanteric tip had a weak correlation with patient height and neck shaft angle (r: -0.23 and r: -0.35, respectively). Interobserver reliability and agreement between left and right side measurements were strong (intraclass correlation coefficient: >0.94 and >0.88, P < 0.001, respectively). The mean measurement differences between sides was 0 mm (95% confidence interval: -1 to 1). Greater trochanter offset averaged 15 mm (range, 5-26 mm; standard deviation: 5) on the right and 15 mm (range, 5-25 mm; standard deviation: 5.1) on the left (P = 0.95).
Conclusion: A high degree of variability exists for the ideal trochanteric entry site. The trochanteric tip represents the ideal starting point in only the minority of cases. Preoperative contralateral templating provides an accurate means for establishing a patient-specific entry point to minimize fracture malreduction.