By Joene Hendry
NEW YORK (Reuters Health) – The cumulative risk of hip dislocation after total hip arthroplasty is significantly affected by patient gender, an underlying diagnosis of osteonecrosis, and age at the time of arthroplasty, researchers reported on Sunday during the American Academy of Orthopaedic Surgeons annual meeting in Dallas.
Overall, "the lifetime risk of dislocation for patients that live several decades after hip replacement, at least for Charnley total hip arthroplasty, is higher than was previously thought," Dr. Daniel J. Berry, of the Mayo Clinic in Rochester, Minnesota, told Reuters Health in an interview during the meeting. He added that, "almost all modern hip replacement designs can trace their lineage to the Charnley total hip arthroplasty."
Dr. Berry and Dr. W. Scott Harmsen analyzed the risk of hip dislocation in 6623 patients treated consecutively at the Mayo Clinic between 1969 and 1984. The patients (2869 women) were between the ages of 13 to 95 years at the time of surgery, and all underwent Charnley total hip arthroplasties.
They found that that the cumulative risk of hip dislocation is highest during the first year after arthroplasty and continues to increase by about 0.2% each year. By 25 years post-surgery, the risk is 7%.
"The overall rate of dislocation in most papers has usually been quoted in the 2-to-3% range," Dr. Berry said, but he added that "earlier evaluations lead to lower prevalence figures."
Drs. Berry and Harmsen found that, for women, the cumulative risk of hip dislocation at 25 years post-replacement was 8.9% compared with 4.5% for men. The researchers conclude that female gender places a patient at higher risk for hip dislocation "early and indefinitely after joint arthroplasty."
Patients who are 70 years of age or older at the time of arthroplasty have a 12.5% risk of dislocation compared with a risk of 6.5% in patients younger than 70 years. For patients with osteonecrosis of the femoral head, the risk of dislocation was 14.1%, while patients with osteoarthritis had a risk of dislocation of 6.4%, both over 25 years.
"We cannot be certain how these data apply to present-day hip replacements," Dr. Berry said noting that, "specific operative surgical approaches can reduce the risk of dislocation." He added that patients need to understand that there is a constant low-level risk of dislocation following hip replacement and that this risk lasts for the life of the patient.