A Radiologic Predictor Of Intraoperative Lateral Wall Fractures In Pertrochanteric Fractures Treated With Cephalomedullary Nailing

Objective To investigate whether the line drawn as a tangent to the superior femoral neck can be used to predict the incidence of intraoperative lateral wall fractures in pertrochanteric fractures treated with a cephalomedullary nail and to compare the effect on lateral wall of two intramedullary fixation devices:Intertan nail and Gamma3 nail.Methods We retrospectively analyzed the clinical data of 56 patients who had been trrated in our department from August 2014 to February 2015 for intertrochanteric hip fractures closed reduction and internal fixation with Intertan nail or Gamma3.There were six patients whose points on the lateral femoral cortex where the fracture lines meet it were below the the vastus ridge.All patients were assessed with pre- and postoperative radiographs including X-ray images and three dimensional CT reconstruction(3D CT)images. 50 patients whose points on the lateral femoral cortex where the fracture lines meet it were above the the vastus ridge were grouped according to whether intraoperative lateral wall fractures exist or not and their different intramedullary fixation devices.In accordance with the lateral wall’s circumstance,the group A included 17 cases with intraoperative lateral wall fractures, and the other 33 cases with an intact lateral wall were in group B. In group A, the mean age of patients was 77.0 years(54 to 92) and there were 3cases with type OTA31-A1 and 14 cases with type OTA31-A2.In group B, the mean age of patients was 74 years(47-94) and there were 17 cases with type OTA31-A1 and 16 cases with type OTA31-A2. The two groups were compared in terms of the length from the point on the lateral femoral cortex where the fracture line meets it to the vastus ridge and the tip apex distance(TAD).Then we used an ROC curve to estimate a threshold value that could predict lateral wall fracture.With stratified sampling, we also adopt the same ratio of gender to select 25 patients from the 50 patients. On the contralateral side without fractures,we measured the length from the point on the lateral femoral cortex where the line drawn as a tangent to the superior femoral neck meets it to the vastus ridge. After that, we compared the length with the threshold value.In addition, we compared the incidence of intraoperative lateral wall fractures between Intertan nailing and Gamma3 nailing.Results The length from the point on the lateral femoral cortex where the fracture line meets it to the vastus ridge was 15.6±6.33 mm and 28.5±6.76 mm respectively for group A and group B, with significant difference(P=0.00000004).The incidence of intraoperative lateral wall fractures in OTA31-A2 fractures was 46.7%(14/30), which was significantly higher than the incidence of 15%(3/20) in OTA31-A1 fractures(P=0.021). The tip apex distance(TAD) was 16.8±3.76 mm and 20.2±6.76 mm respectively for group A and group B,with significant difference(P=0.024). Through ROC curve, we obtained a threshold value that was 20.445 mm. When the length from the point on the lateral femoral cortex wherethe fracture line meets it to the vastus ridge was 20.445 mm, the sensitivity was 90.9% and specificity was 88.2%(P<0.0001). On the contralateral side, the length from the point on the lateral femoral cortex where the line drawn as a tangent to the superior femoral neck meets it to the vastus ridge was 19.4±3.16 mm, which was similar to the threshold value“20.445mm”, without significant difference(P=0.109). Additionally, the incidence of intraoperative lateral wall fractures was 38.7%(12/31) and 26.3%(5/19) respectively for the Intertan and Gamma3 groups, but without significant difference(P=0.369).Conclusions The length from the point on the lateral femoral cortex where the fracture line meets it to the vastus ridge can predict the incidence of intraoperative lateral wall fractures in pertrochanteric fractures treated with a cephalomedullary nail. When the length <20.445 mm, the lateral wall is more easily fractured intraoperatively. And the corresponding site of the threshold “20.445mm” may be the point on the lateral femoral cortex where the line drawn as a tangent to the superior femoral neck meets it. In the study of the incidence of intraoperative lateral wall fractures, there is not significant difference between Intertan nail and Gamma3 nail.