Ph Hernigou, D Julian, I Guissou (Créteil)
Background: Total hip arthroplasty (THA) has been efficacious for treating hip fractures in healthy older patients. However, in these patients with fractures a widely variable prevalence of dislocation has been reported, partly because of varying durations of follow-up for this specific end-point. The purpose of the present study was to determine the cumulative risk of dislocation in these patients with fractures and to investigate if dual mobility or constrained liners decrease the risk of dislocation.
Matrial and methods: Between 2000 and 2005, 125 patients with neck fracture underwent primary THA using a dual mobility (50 hips) or a constrained (75 hips) liner. The results of these 125 dual mobility acetabular liners were compared with 180 THA without dual mobility or without constrained liners performed for neck fractures in the same hospital between 1995 and 2000 by the same surgical team. The mean age of the 305 patients was 75 years (65 to 85). All patients were followed for a minimum of 5 years for radiographic evidence of implant failure. The patients were followed at routine intervals and were specifically queried about dislocation. The cumulative risk of dislocation and reccurent dislocation was calculated with use of the Kaplan-Meier method.
Results: For patients without dual mobility or without constrained liners, the cumulative risk of a first-time dislocation was 5% at one month and 12% at one year and then rose at a constant rate of approximately 1% every year to 16% at five years. For patients with dual mobility liners, the cumulative risk of a first-time dislocation was 1% at one month, 2% at one year and then did not changed at 5 years. There were no differences in the mortality rates or in loosening rates among the treatment groups. The rate of secondary surgery was highest in the group without constrained or dual mobility (10% for recurrent dislocation) compared with 1% in the group treated with constrained or dual mobility liners. In absence of constrained or dual mobility liners, multivariate analysis revealed that the relative risk of dislocation for female patients (as compared with male patients) was 2.1 and that the relative risk for patients who were 80 years old or more (as compared with those who were less than 80 years old) was 1.5. Two underlying diagnoses occurring during follow-up— cognitively impaired patients or neurologic desease—were also associated with a significantly greater risk of dislocation.
Discussion and Conclusion: The cumulative long-term risk of dislocation for patients with hip fractures is greater than has been reported in short-term studies. The incidence of dislocation is highest in the first year after arthroplasty and then continues at a relatively constant rate for the life of the arthroplasty. Patients at highest risk are old female patients and those with a diagnosis of neurologic desease. Dual mobility or constrained liners in these patients is an efffective technique to prevent post operative hip dislocation