Evaluation of femoral neck fracture migration after internal fixation with an angle stable implant compared with gold standard cannulated cancellous screws in young adults: Study protocol for a clinical RCT using radiostereometric analysis

Background Hip fractures are most commonly suffered by elderly patients, but 2–11% of hip fractures affect younger patients. In young adults with femoral neck fractures, internal fixation is the recommended treatment for both displaced and non-displaced fractures. However, treatment with internal fixation carries a high complication rate. A known complication of internal fixation after gold standard cannulated cancellous screws is fracture compression resulting in shortening of the femoral neck, which is associated with clinically important decreases in functional outcome. New osteosynthesis implants have been developed to prevent fracture compression and improve the outcomes of internal fixation of femoral neck fractures. Recent preliminary clinical and biomechanical studies show that implants with interlocking screws and/or angle stability have promising results compared to standard internal fixation with cannulated cancellous screws. Measurement and comparison of three-dimensional fracture displacement requires precise method, which may be accommodated with CT bone models and weight-bearing radiostereometric imaging in the months after surgery. Methods A total of 54 young adults under 65 years of age with femoral neck fractures will be electronically randomised to treatment with either internal fixation with cannulated cancellous screws (gold standard) or an angle stable implant (Dynaloc, Swemac). Patients will be excluded if they are unable to understand the study information, have a transcervical, basicervical or pathological fracture, or present clinically as frail. Primary outcome measure is fracture migration at 12 weeks measured in radiostereometric imaging using CT bone models and AutoRSA software. Secondary outcomes will be fracture migration in terms of femoral neck shortening at 6 weeks, function scores and pain Verbal Rating Scale at 6 and 12 weeks, surgical complications, reoperation, and mortality at event. Discussion This clinical trial will examine fracture migration and the functional outcomes of internally fixated femoral neck fractures in young adults by comparing the results of an angle stable implant (Dynaloc, Swemac) compared with cannulated cancellous screws. The study has perspective to provide scientific evidence for empirical decision-making when choosing implants for femoral neck fractures in young adults. Trial registration ClinicalTrials.gov ID: NCT06521671. Registered July 22nd 2024