The horizontal shear fracture of the pelvis

PURPOSE: Various classification systems describe fractures of the acetabulum and pelvis separately. Horizontal shear fractures involve the pelvic ring and both acetabula and have not been previously described. The aim of this study is to describe the horizontal shear fracture of the pelvis. METHODS: At a level 1 trauma centre over 10 years from December 2008 to December 2018, 1242 patients had pelvic and acetabular fractures. Six patients had horizontal shear fractures, comprising 0.5% of all pelvic and acetabular fractures. Demographic, clinical and radiological data was collected. Clinical outcomes were pain and mobility level, sciatic nerve symptoms, further acetabular or pelvic surgery, or total hip arthroplasty. Radiological outcomes included fracture displacement, implant migration, femoral head osteonecrosis, and post-traumatic arthritis. Outcomes were assessed at a minimum 12 month follow-up. RESULTS: The median patient age was 35 years. Five of six shear fractures were due to motorcycle crashes. No mortalities occurred. At follow-up, three patients reported pain, two patients had difficulty mobilising associated with traumatic sciatic nerve injury, and one patient underwent total hip arthroplasty for femoral head osteonecrosis. No fracture displacement or implant migration occurred. The Matta arthritis grade was excellent or good in all except one hip. Median follow-up time was 1.8 (range 1.1–7.8) years. CONCLUSION: The horizontal shear fracture of the pelvis is a high-energy injury characterised by separation of the anterior and posterior pelvic ring through the acetabula. Good outcomes can be achieved with open reduction and internal fixation of displaced fractures.