Calcar fracture gapping: a reliable predictor of anteromedial cortical support failure after cephalomedullary nailing for pertrochanteric femur fractures

Abstract

Background: Maintaining anteromedial cortical support is essential for controlling sliding and decreasing postoperative implant-related complications. However, adequate fracture reduction with cortical support in immediate postoperative fluoroscopy is not invariable in postoperative follow-ups. This study was conducted to investigate the risk factors leading to anteromedial cortical support failure in follow up for pertrochanteric femur fractures treated with cephalomedullary nails.

Methods: This retrospective study enrolled 159 patients with pertrochanteric fractures (AO/OTA- 31A1 and 31A2) that fixed with cephalomedullary nails. All patients were evaluated as adequate fracture reduction in immediate postoperative fluoroscopy before leaving the operation theater. The patients were separated into two groups based on the condition of the anteromedial cortex in the postoperative 3D CT with full-range observation: those with calcar support maintained in Group 1 and those with calcar support lost in Group 2. Demographic information, fracture classification, TAD (tip-apex distance), Cal-TAD, Parker ratio, NSA (neck-shaft angle), reduction quality score, and calcar fracture gapping were collected and compared. Logistic regression analysis was conducted to explore the risk factors leading to anteromedial cortex change.

Results: Anteromedial cortical support failure was noted in 46 cases (29%). There was no significant difference between the two groups concerning age, sex, side injury, TAD, Cal-TAD, Parker ratio, or NSA. There was a significant difference in the AO/OTA fracture classification in univariate analysis but no difference in the multivariable analysis. The reduction quality score, calcar fracture gapping in the AP (anteroposterior), and lateral views were significantly associated with anteromedial cortical support failure in follow-up after cephalomedullary nailing in the multivariable analysis. The threshold value of calcar fracture gapping for the risk of loss was 4.2 mm in the AP and 3.8 mm in the lateral fluoroscopies. Mechanical complications (lateral sliding and varus) were frequently observed in the negative anteromedial cortical support group.

Conclusions: Good reduction quality was a protective factor, and larger calcar fracture gapping in the AP and lateral views were risk factors leading to the postoperative loss of anteromedial cortical support. Therefore, we should pay close attention to fracture reduction and minimize the calcar fracture gap during surgery.

Keywords: Anteromedial cortical support; Calcar fracture gapping; Cephalomedullary nailing; Fracture reduction quality; Pertrochanteric fracture.

Fig. 1

Calcar residual fracture gapping measurement at the medial basicervical in the AP view

Fig. 2

Anterior fracture gapping in the lateral view, defined parallel to the sliding direction of the head-neck fragment

Fig. 3

An illustrative case of maintenance-of-calcar support in postoperative 3D-CT follow-up. A: An 86-year-old female diagnosed with 31A2.3 trochanteric fracture. B: Immediate AP fluoroscopy after operation showed positive relation of the two medical cortices; the arrow indicated a close contact of the inferior medial calcar. C: Immediate lateral fluoroscopy after operation showed neutral relation of the two anterior cortices; the arrow indicated minimal gap at the anterior cortex. D: Postoperative 3D CT image showed true positive anteromedial cortical support at the inferior corner. E: In postoperative 26 months follow-up, the fracture healed with minimal lateral sliding of the helical blade

Fig. 4

An illustrative case of loss-of-calcar support in postoperative 3D-CT follow-up. A: A 77-year-old female, diagnosed with 31A2.2 trochanteric fracture. B: Immediate AP fluoroscopy after operation, the arrow showed a large calcar fracture gap of the medial cortex (4.83 mm). C: Immediate lateral fluoroscopy after operation, the arrow showed a large calcar fracture gap of the anterior cortex (3.61 mm). D: Postoperative 3D CT image showed negative anteromedial cortical support. The arrow indicated posterior sagging of the head-neck fragment. E: In postoperative 14 months follow-up, the AP radiograph showed an apparent lateral sliding of the helical blade (10.5 mm)

Fig. 5

A graph demonstrating the ROC curve by plotting the sensitivity and the 1-specificity. For the calcar fracture gapping assessment, the recommended cut-off point for balancing sensitivity and specificity was 4.2 mm with 91.3% sensitivity and 90.3% specificity in the AP view and 3.8 mm with 80.4% sensitivity and 85.8% specificity in the lateral view. The area under the curve (AUC) was 0.922 for the AP view and 0.843 for the lateral view