Background: A total hip arthroplasty (THA) is often used as treatment for failed osteosynthesis of femoral neck fractures and is now also used for acute femoral neck fractures. To investigate the results of THA after femoral neck fractures, we used data from the Norwegian Arthroplasty Register (NAR).
Patients and methods: The results of primary total hip replacements in patients with acute femoral neck fractures (n = 487) and sequelae after femoral neck fractures (n = 8,090) were compared to those of total hip replacements in patients with osteoarthrosis (OA) (n = 55,109). The hips were followed for 0-18 years. The Cox multiple regression model was used to construct adjusted survival curves and to adjust for differences in sex, age, and type of cement among the diagnostic groups. Separate analyses were done on the subgroups of patients who were operated with Charnley prostheses.
Results: The survival rate of the implants after 5 years was 95% for the patients with acute fractures, 96% for the patients with sequelae after fracture, and 97% for the OA patients. With adjustment for age, sex, and type of cement, the patients with acute fractures had an increased risk of revision compared to the OA patients (RR 1.6, 95% CI: 1.0-2.6; p = 0.05) and the sequelae patients had an increased risk of revision (RR 1.3, 95% CI: 1.2-1.5; p < 0.001). Sequelae hips had higher risk of revision due to dislocation (RR 2.0, 95% CI: 1.6-2.4; p < 0.001) and periprosthetic fracture (RR 2.2, 95% CI: 1.5-3.3; p < 0.001), and lower risk of revision due to loosening of the acetabular component (RR 0.72, 95% CI; 0.57-0.93; p = 0.01) compared to the OA patients. The increased risk of revision was most apparent for the first 6 months after primary operation.
Interpretation: THA in fracture patients showed good results, but there was an increased risk of early dislocations and periprosthetic fractures compared to OA patients.