Hip Replacement Following Intertrochanteric Osteosynthesis Failure: Is It Possible to Restore Normal Hip Biomechanics?

Introduction: Intertrochanteric femoral fractures (IFFs) are the most common traumatic injuries in elderly people and significantly impact the patient’s health status. The current evidence indicates that short intramedullary nails may be a better choice than dynamic hip screws in IFF management, being less invasive and biomechanically superior, providing a buttress to limit fracture collapse. On the other hand, an unstable fracture may collapse even after adequate reduction and fixation. This paper aims to describe the surgical complexity of the nail-to-total hip arthroplasty (THA) conversion, focusing on the restoration of normal hip geometry. Material and Methods: Patients referred to our level I trauma center with failed cephalomedullary nailing following IFFs and managed with the nail-to-THA conversion were retrospectively recruited. The anteroposterior postoperative pelvis radiographs were analyzed to establish whether the normal biomechanics of the involved hip were restored. The following radiographic parameters were recorded and compared to the contralateral unaffected side: hip offset, cervical–diaphyseal angle, and limb length discrepancy. Clinical assessment was performed using the following scores: the Harris hip score (HHS) and the visual analog scale for pain (VAS). The independent samples t-test and the Pearson correlation test were performed. The tests were two-tailed; a p < 0.05 was considered significant. Results: A total of 31 patients met the inclusion and exclusion criteria (10 males and 21 females; mean age: 76.2 years; range: 66–90 years) and were included in this study. The modes of trochanteric nail failure included the following: cut-out in 22 cases (70.97%), non-union in 4 cases (12.9%), peri-implant fracture in 1 case (3.23%), cut-through in 2 cases (6.45%), and femoral head avascular necrosis (HAN) in 2 cases (6.45%). Long stems were used in 21 patients out of 31 (67.74%), while dual-mobility cups were implanted in 24 patients out of 31 (77.41%). A significant mean neck shaft angle (NSA) increase (p < 0.001) and a significant mean femoral offset reduction (FO, p 0.001) compared to the contralateral hip were recorded; a mean limb length discrepancy (LLD) of 8.35 mm was observed. A significant correlation between HHS and ∆NSA (p = 0.01) and ∆FO (p = 0.003) was recorded. Conclusions: Conversion from a cephalomedullary nail to THA is a complex procedure that should be considered a revision surgery, rather than a primary surgery. Surgeons must be aware that normal hip geometry may not be obtained during this surgical procedure; thus, a patient undergoing the nail-to-THA conversion for intertrochanteric fixation failure may have an increased risk of implant-related complications.