Low filling ratio of the distal nail segment to the medullary canal is a risk factor for loss of anteromedial cortical support: a case control study

Abstract

Background Anteromedial cortical support apposition (positive and/or neutral cortical relations) is crucial for surgical stability reconstruction in the treatment of trochanteric femur fractures. However, the loss of fracture reduction is frequent in follow-ups after cephalomedullary nail fixation. This paper aimed to investigate the possible predictive risk factors for postoperative loss of anteromedial cortex buttress after nail fixation. Methods A retrospective analysis of 122 patients with AO/OTA 31A1 and A2 trochanteric femur fractures treated with cephalomedullary nails between January 2017 and December 2019 was performed. The patients were classified into two groups according to the postoperative status of the anteromedial cortical apposition in 3D CT images: Group 1 with contact “yes” (positive or anatomic) and Group 2 with contact “No” (negative, loss of contact). The fracture reduction quality score, tip-apex distance (TAD), calcar-referenced TAD (Cal-TAD), Parker ratio, neck-shaft angle (NSA), and the filling ratio of the distal nail segment to medullary canal diameter in anteroposterior (AP) and lateral fluoroscopies (taken immediately after the operation) were examined in univariate and multivariate analyses. Mechanical complications were measured and compared in follow-up radiographs. Results According to the postoperative 3D CT, 84 individuals (69%) were categorized into Group 1, and 38 individuals (31%) were classified as Group 2. The multivariate logistic regression analysis showed that the poor fracture reduction quality score (P < 0.001) and decreasing filling ratio in the lateral view (P < 0.001) were significant risk factors for the loss of anteromedial cortical contact. The threshold value for the distal nail filling ratio in lateral fluoroscopy predicting fracture reduction re-displacement was found to be 53%, with 89.3% sensitivity and 78.9% specificity. The mechanical complication (varus and over lateral sliding) rate was higher in Group 2. Conclusions The fracture reduction quality score and the decreasing filling ratio of the distal nail to the medullary canal in the lateral view (a novel parameter causing pendulum-like movement of the nail) were possible risk factors for postoperative loss of anteromedial cortical support.

What is the importance of distal nail diameter in the treatment of intertrochanteric femur fractures?

“…In a study by Song et al[ 5 ] involving 122 ITFF patients, the effects of distal nail diameter on anteromedial cortical support were investigated and a significant relationship was found between the nail diameter and anteromedial cortical support. In this regard, the authors recommended the use of the largest nail possible without the need for reamerization.…”

“…Postoperative complications such as femoral head/neck collapse, femoral shortness or varus malunion, cut-out of the lag screw from the femoral head, nonunion or implant failure may occur after CMN for ITFF. [ 5 - 7 ] Well-established risk factors for implant failure of CMN in the treatment of ITFF are increased tip-apex distance, unstable fractures, and inadequate reduction. [ 8 , 9 ] Although risk factors for implant failure have been extensively studied for CMNs in the treatment of ITFFs,[ 10 ] little focus has been given toward for the distal nail diameter.…”

A sophisticated fracture classification system of the proximal femur trochanteric region (AO/OTA-31A) based on 3D-CT images

“…There is an open deformity of the posterior coronal fragment(s) due to the insertion of the head–neck implant ( Figure 10 ). In these circumstances, sagittal nail toggle or pendulum-like movement in the medullary canal may present and result in loss of fracture reduction of the anteromedial cortical apposition ( 14 , 28 ).…”

Biomechanical evaluation of three implants for treating unstable femoral intertrochanteric fractures: finite element analysis in axial, bending and torsion loads

“…The fixation techniques of these intramedullary nails are minimally invasive and easy to operate. Yet, the proximal parts of UFIFs are prone to implant lossening and even failure because of swing effects while they are fixed via a cephalomedullary nail due to the osteoporotic medullary cavity resulting from osteopenia and the advanced age (Ceynowa et al, 2020;Chen et al, 2022;Song et al, 2022). The cephalomedullary nail of PFNA and Gamma3 is designed with only one nail, and its antirotation effect is poor.…”