Femoral Neck Fractures With Associated Ipsilateral Femoral Shaft Fractures in Young Adults <50 Years Old: A Multicenter Comparison of 80 Cases Versus Isolated Femoral Neck Fractures

OBJECTIVES: To analyze patients, injury patterns, and treatment of femoral neck fractures (FNFs) in young patients with FNFs associated with shaft fractures (assocFNFs) to improve clinical outcomes. The secondary goal was to compare this injury pattern to that of young patients with isolated FNFs (isolFNFs). Design: Retrospective multicenter cohort series. Setting: Twenty-six North American level-1 trauma centers. Patient Selection Criteria: Skeletally mature patients, <50 years old, treated with operative fixation of an FNF with or without an associated femoral shaft fracture. Outcome Measures and Comparisons: The main outcome measurement was treatment failure defined as nonunion, malunion, avascular necrosis, or subsequent major revision surgery. Odds ratios for these modes of treatment were also calculated. RESULTS: Eighty assocFNFs and 412 isolFNFs evaluated in this study were different in terms of patients, injury patterns, and treatment strategy. Patients with assocFNFs were younger (33.3 +/- 8.6 vs. 37.5 +/- 8.7 years old, P < 0.001), greater in mean body mass index [BMI] (29.7 vs. 26.6, P < 0.001), and more frequently displaced (95% vs. 73%, P < 0.001), "vertically oriented" Pauwels type 3, P < 0.001 (84% vs. 43%) than for isolFNFs, with all P values < 0.001. AssocFNFs were more commonly repaired with an open reduction (74% vs. 46%, P < 0.001) and fixed-angle implants (59% vs. 39%) (P < 0.001). Importantly, treatment failures were less common for assocFNFs compared with isolFNFs (20% vs. 49%, P < 0.001) with lower rates of failed fixation/nonunion and malunion (P < 0.001 and P = 0.002, respectively). Odds of treatment failure [odds ratio (OR) = 0.270, 95% confidence interval (CI), 0.15-0.48, P < 0.001], nonunion (OR = 0.240, 95% CI, 0.10-0.57, P < 0.001), and malunion (OR = 0.920, 95% CI, 0.01-0.68, P = 0.002) were also lower for assocFNFs. Excellent or good reduction was achieved in 84.2% of assocFNFs reductions and 77.1% in isolFNFs (P = 0.052). AssocFNFs treated with fixed-angle devices performed very well, with only 13.0% failing treatment compared with 51.9% in isolFNFs treated with fixed-angle constructs (P = <0.001) and 33.3% in assocFNFs treated with multiple cannulated screws (P = 0.034). This study also identified the so-called "shelf sign," a transverse >= 6-mm medial-caudal segment of the neck fracture (forming an acute angle with the vertical fracture line) in 54% of assocFNFs and only 9% of isolFNFs (P < 0.001). AssocFNFs with a shelf sign failed in only 5 of 41 (12%) cases. CONCLUSIONS: AssocFNFs in young patients are characterized by different patient factors, injury patterns, and treatments, than for isolFNFs, and have a relatively better prognosis despite the need for confounding treatment for the associated femoral shaft injury. Treatment failures among assocFNFs repaired with a fixed-angle device occurred at a lower rate compared with isolFNFs treated with any construct type and assocFNFs treated with multiple cannulated screws. The radiographic "shelf sign" was found as a positive prognostic sign in more than half of assocFNFs and predicted a high rate of successful treatment. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.