Does Cephalomedullary Nail Design Influence Risk of Varus Collapse in Subtrochanteric Femur Fractures?

Area of Science:

• Orthopedic Surgery
• Trauma Surgery
• Biomechanics

Background:

• Subtrochanteric femur fractures often require cephalomedullary nails (CMNs).
• Proximal fractures may have inadequate cortical fit, potentially leading to varus deformity.
• A hypothesis suggests increased nail-canal mismatch elevates varus deformity risk.

Purpose of the Study:

• To investigate the correlation between nail-canal mismatch and neck shaft angle in subtrochanteric femur fractures.
• To compare outcomes between different types of CMNs: the TFNA (tapered femoral nail with antirotation) and GTE (greater trochanteric entry) recon nail.
• To assess secondary outcomes including nonunion and malunion rates.

Main Methods:

• Retrospective study of 71 patients with subtrochanteric femur fractures treated with CMNs.
• Patients divided into TFNA (n=35) and GTE (n=36) cohorts.
• Primary outcome: correlation between nail-canal mismatch and final neck shaft angle; secondary outcomes: nonunion and malunion rates.

Main Results:

• No significant correlation between nail-canal mismatch and neck shaft angle for GTE nails (r=-0.187, p=0.274).
• Significant negative correlation for 125° TFNAs (r=-0.678, p=0.001) and 130° TFNAs (r=-0.515, p=0.041).
• For 125° TFNAs, each 1 mm increase in mismatch decreased neck shaft angle by 0.757°.

Conclusions:

• GTE nails and TFNAs show similar nonunion and malunion rates for subtrochanteric fractures.
• 125° TFNAs may be linked to increased varus deformity with greater nail-canal mismatch.