Tip-apex distance and other predictors of outcome in cephalomedullary nailing of unstable trochanteric fractures

Abstract

Background: Cephalomedullary nails are presently the gold standard in management of unstable trochanteric fractures. The tip-apex distance (TAD) is one of the most important factors that determines success or failure of fixation, but was described originally in context of an extramedullary hip screw. Cephalomedullary nails use a different biomechanical approach to fixation; and it is hypothesized that the TAD rule may not apply similarly with these. The aim of this study is to assess whether a high TAD correlates with poor outcomes with cephalomedullary nails, and to elucidate other factors that may predict such outcome. Methods: We retrospectively reviewed the clinical and radiographic records of patients with intertrochanteric fractures, treated at our institution over a 2-year period. Those with unstable fractures (31.A2 and 31.A3), and who were treated with cephalomedullary nails were included in the study. The TAD and the position of the device in the femoral head (Cleveland index) were assessed. Other factors that could influence outcome like age, gender, AO fracture type, restoration of neck-shaft angle and degree of osteoporosis were analysed. Radiographic records of up-to at-least 3 months post-operatively were assessed for complications. Results: After applying the exclusion criteria, 75 patients were included in the analysis. The overall rate of complications was 12%. They occurred in two major patterns -varus collapse and cut-out occurred in 5 patients (6.67%), and device migration in 4 patients (5.33%). The average TAD of patients with cut-out was 28.78 mm, compared to 19.44 mm in those without cut-out (p ¼ 0.002). Our data predicted a cutoff TAD >23.56 mm as most significant for cut-out with cephalomedullary nails. On univariate logistic regression, high TAD (p ¼ 0.009), sub-optimal device positioning (p ¼ 0.02) and poor restoration of neckshaft angle (p ¼ 0.04) were found to be significant for varus collapse and cut-out, but not for complications relating to device migration. On multivariate analysis, none of the above factors reached statistical significance in isolation. Conclusion: As with extramedullary devices, TAD, along with sub-optimal device positioning and poor restoration of neck-shaft angle is a useful predictor of cut-out even with cephalomedullary nails, negating the initial hypothesis. The above factors in combination have a more significant effect than any one factor in isolation to cause varus collapse and implant cut-out. However these do not affect Z effect, reverse Z effect or other types of device migration seen especially with dual-screw nails.

Modified Short Proximal Femoral Nail for Intertrochanteric Fractures of Femur in Indian Patients - our Experience

“…Mean TAD total was 22.8mm while TAD ap and TAD lateral was 11.8 and 11.0mm respectively ( Table IV ). TAD has been poorly studied in biaxial cephalomedullary implants (having two screws) such as ours and currently there is no proven or recommended TAD for such implants 15 , 16 . Most frequent position of lag screw was charted in inferior-central zone in 95 cases ( Fig.…”

“…They concluded that a combination of high TAD, suboptimal position of implant and poor restoration of neck shaft angle may predispose to cut-out. However, achieving TAD within safe limits didn’t appear to influence screw and device migration in dual screw nails 16 . Another technical aspect of note is the length of anti-rotation screw.…”

“…Baumgartner’s original description of TAD pertains with sliding hip screw system with a large single cephalic screw. It has been extrapolated and used in cephalomedullary nails including dual screw systems such as ours 15 , 16 . TAD was measured for only the lag screw as hip pin gets obscured by the lag screw in lateral view.…”

Anterior Lag Screw Position and Suboptimal Reduction in Lateral Plain as Predictors of Failure in Cephalomedullary Nailing of Intertrochanteric Fractures

“…Therefore, identifying predictors of failure is particularly relevant. Though much has been published regarding predictors of failure of extramedullary implants, [4][5][6][7] nail failure has not been extensively studied [8][9][10][11]. Since the biomechanical behavior of extramedullary implants differs from that of intramedullary implants, predictors of failure may also be different.…”

Biomechanical Evaluation of Extramedullary Versus Intramedullary Reduction in Unstable Femoral Trochanteric Fractures

“…However, the overall failure rate of fixation operations for unstable femoral trochanteric fractures is 3-12%. 5 - 7 …”