BACKGROUND: The purpose of this study was to estimate the incidence of reoperation and the effect of implant position on the risk of reoperation within 12 months following osteosynthesis with use of parallel implants for femoral neck fractures.

METHODS: From cases registered in the Danish Fracture Database, 1,206 consecutive surgeries for a primary femoral neck fracture treated with use of parallel implants during the period of December 2011 to November 2015, and having available radiographs and follow-up data, were reviewed. Data included age, sex, time to surgery, fracture classification, and American Society of Anesthesiologists (ASA) score. Fracture displacement, posterior tilt, the number of implants, posterior distance, calcar distance, tip-cartilage distance, and angulation of implants were measured on pre- and postoperative radiographs. Data on secondary surgeries were collected from the Danish Civil Registration System. The effects of the included variables on the risk of reoperation were evaluated using Cox regression analysis.

RESULTS: The median age was 73 years (range, 21 to 102 years); in 69% of the cases, the patient was female. Two implants were used in 997 cases and 3 implants were used in 209. In 157 cases, the patient underwent reoperation within 1 year; in 228 cases, the patient died within 1 year. The median time to reoperation was 116 days. Patients <70 years of age were more likely to undergo reoperation (18.0% compared with 9.8%) but less likely to die (7.4% compared with 26.3%) than were patients ≥70 years of age. Female sex, higher ASA score, and displaced fractures were associated with increased risk of reoperation. Time to surgery was associated with increased risk of reoperation for displaced fractures only. Of the variables pertaining to the osteosynthesis, only insufficient fracture reduction, placement of the implants with an angle to the shaft of ≤125°, and femoral head perforation significantly increased the risk of reoperation. We found no effect of the posterior distance, the calcar distance, the tip-caput distance, or whether or not the implants were parallel.

CONCLUSIONS: Insufficient reduction, varus position of the implants, and perforation of the femoral head cartilage were the only surgical factors influencing the risk of reoperation. Sufficient fracture reduction is perhaps more important than focusing on an optimal position of the implants.

LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.