Predicting 'sagittally unstable intertrochanteric fractures' that require direct manipulation for reduction: a fracture morphology analysis.

Sagittally unstable intertrochanteric fracture (SUITF) is the posterior displacement of the shaft fragment (posterior sagging, [PS]) which causes difficulty in achieving an acceptable closed reduction in lateral view. This study aimed to validate the morphological characteristics of SUITF. Data of patients with acute intertrochanteric fractures who underwent surgery were retrospectively reviewed. Altogether, 382 patients were enrolled and classified into the PS and control groups, based on the presence of PS. We obtained morphological characteristics on plain radiographs based on literature (Long medial beak, anterosuperior obliquity, lesser trochanter (LT) detachment, extramedullary beak, and V shape cortical defect). Comparison between groups and multivariable analysis were performed using a multiple Firth logistic regression analysis. For all morphological characteristics, the proportion of patients was significantly higher in the PS group than in the control group. In the multiple Firth logistic regression analysis, 'long medial beak distal to lesser trochanter (LT)' (OR, 7.93; 95%CI: 1.72-36.59; P = 0.008); 'anterosuperior obliquity' (OR, 23.87; 95%CI: 1.37-415.54; P = 0.030); 'LT detachment,' (OR, 10.15; 95%CI: 2.03-50.83; P = 0.005); and 'extramedullary beak' (OR, 39.47; 95%CI: 2.14-727.26; P = 0.013) were significantly associated with PS presence. These morphological characteristics will be helpful in preoperative detection of SUITF for direct manipulation of fractures.