Subtle hip joint subluxation after femoral neck fracture fixation: an ominous sign in a report of two cases

INTRODUCTION Subluxation and dislocation of the hip occurring after proximal femoral fracture fixation are rare complications. Most have been reported to occur after trochanteric fracture fixation with a screw-plate combination. A subluxation or dislocation after internal fixation of femoral neck fractures is even more uncommon, and almost all reported cases involve basicervical fractures fixed with a screw-plate combination. To the best of the authors’ knowledge, hip subluxation or dislocation after fixation of a transcervical femoral neck fracture with a minimally invasive implant like a cannulated cancellous screw (CCS) has not been reported in the literature to date. Dislocation or subluxation after fixation can occur with (septic) or without (aseptic) infection. In the absence of infection, excessive valgus fixation, neck collapse, and capsular injury are the described mechanisms while septic subluxation or dislocation usually involves tense intraarticular collection or destruction of restraining structures caused by hip joint sepsis. The deep sepsis in such cases is usually a low-grade infection caused by Staphylococcus aureus or epidermidis presenting without any systemic signs. The outcome in both septic and aseptic dislocations is mostly poor, and often replacement surgery is needed. This report presents two patients with hip subluxation after minimally invasive fixation of displaced transcervical femoral neck fractures with CCS. Ethical approval was granted for the study by the Maulana Azad Medical College Ethical Clearance Board (MAM/LNH/120/2). Written, informed consent was obtained from all patients authorizing clinical examination, radiographic and photographic documentation, and surgical procedures.