Postoperative Rotation Deformity of Head-Neck Fragments in Unstable Intertrochanteric Fractures Fixed with Intramedullary Nails.

Background: Our purpose was to quantify the postoperative rotation deformity (RD) after osteosynthesis of unstable intertrochanteric fractures (ITFx) using 3D-CT / image processing software, and to clarify the clinical meaning of RD.

Methods: Forty-six consecutive patients with unstable intertrochanteric fractures were enrolled in this study. All were fixed with Gamma 3 Trochanteric nail and RC Lag Screw^® (Stryker). We performed 3D-CT evaluations for the rotational deformity of head-neck fragments, the medial cortex support (MCS) between main fragments and bone healing at 3 months postoperatively.

Results: The RD was significantly larger in the patients without the MCS (5.1 ± 4.0°, N = 9) than those with the MCS (2.4 ± 2.6°, N = 37) (P = 0.006*). Delayed healing (N=3) was observed in patients without the MCS, and the association between RD and delayed healing was significant (P = 0.003*, cut-off value 6.4°, sensitivity 100% and specificity 90.7%, AUC 0.91).

Conclusions: This study proposed a novel method of measuring postoperative RD. Lack of MCS may lead to RD and consequent delayed healing in unstable ITFx fixed with intramedullary nails.