Clustering of morphological fracture lines for identifying intertrochanteric fracture classification with Hausdorff distance–based K-means approach

Objectives The aim of this study was to develop a systematic three-dimensional (3D) classification of intertrochanteric fractures by clustering the morphological features of fracture lines using the Hausdorff distance–based K-means approach and assess the usefulness of it in the clinical setting. Methods We retrospectively analyzed the data of 504 patients with intertrochanteric fractures who underwent closed reduction and intramedullary internal fixation. The morphological fracture lines of all patients extracted from computed tomography were transcribed freehand onto the template. All fracture lines were then clustered into five distinct types using the Hausdorff distance–based K-means clustering method. Five radiographic parameters and four functional parameters were used to evaluate the postoperative functional states and mobilization levels. Postoperative complications were also recorded. Results Intertrochanteric fractures were classified into five types: type I (108/504, 21.4%), simple fracture with intact lateral femoral wall and greater trochanter fragment; type II (85/504, 16.9%), simple fracture with intact lateral femoral wall with/without lesser trochanter detachment; type III (147/504, 29.2%), fractures with intertrochanteric crest detachment involving the lesser trochanter and greater trochanter with an intact lateral femoral wall; type IV (113/504, 22.4%), fractures with large intertrochanteric crest detachment and large lesser trochanter and greater trochanter detachment partially involving the lateral femoral wall and less medial cortical support; type V (51/504, 10.1%), a combination of pertrochanteric and lateral fracture line involving the entire lateral femoral wall and lesser trochanter detachment. Parameters of femoral neck–shaft angle and sliding distance of the cephalic nail were significantly different among types. The complication rate generally increased from type I to type V (P = 0.035). Conclusions The unsupervised clustering can achieve identification of the type of intertrochanteric fractures with clinical significance. The Tang classification can be used to describe fracture morphology, predict the possibility of achieving stable reduction and the risk of complications following intramedullary fixation.