The Acetabular Fracture Prognostic Nomogram: Does it Work for Fractures of the Posterior Wall?

Objectives: A recently proposed nomogram is an attempt to define the subset of acetabular fractures at risk for primary total hip arthroplasty (THA) within 2 years of open reduction and internal fixation (ORIF). Our objectives were to determine whether this nomogram provides information adequate to reliably (1) prognosticate outcome within 2 years after ORIF or (2) identify optimal initial treatment choice (THA vs. ORIF) for patients with a posterior wall fracture. Design: Retrospective case series. Setting: University level 1 Trauma Center. Patients: From a database of consecutive posterior wall fractures treated by ORIF, 103 patients were identified for analysis: 6 with an unsatisfactory result at less than 2 years and 97 followed 2-14 years. Intervention: Calculation of percent risk of requiring THA within 2 years using the nomogram. Main Outcome Measurements: Comparison of this percent risk to the actual clinical outcome within 2 years after ORIF, measured in 2 ways: (1) THA performed (5 patients) and (2) overall unsatisfactory hip function determined by the modified Merle d'Aubigne score (9 patients total: the 5 with THA plus 4 additional without THA but having unsatisfactory hip function). Results: The calculated percent risk ranged widely, with much overlap among patients having satisfactory or unsatisfactory results of ORIF. Statistical analysis did not yield a clinically useful positive predictive value: 0.25 [95% confidence interval (CI), 0.08-0.53] for THA and 0.44 (95% CI, 0.21-0.69) for an overall unsatisfactory clinical result. Conclusions: The acetabular fracture prognostic nomogram in its current form does not provide sufficient information to prognosticate outcome after ORIF or to determine appropriate surgical management for posterior wall fractures. Level of Evidence: Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.