Hip resurfacing shows satisfactory results at 5 years follow-up

No significant changes in mean flexion were seen 3- and 5-year follow-ups.

Patients who undergo hip resurfacing arthroplasty continue to show satisfactory outcomes at 5 years mean follow-up, with 97.8% surviving, according to a study by researchers in Australia.

Andrew J, Shimmin, MBBS, FS(OrthoA), and colleagues at Melbourne Orthopaedic Group, Melbourne, reviewed the results of their first 230 Birmingham hip resurfacing implants (Smith and Nephew) in 212 patients. The patients averaged 52.1 years old and had a mean body mass index of 27.02 kg/m².

The researchers compared outcomes at 5 years to those seen at 3 years mean follow-up for the same group of patients, according to the study, published in the British edition of The Journal of Bone and Joint Surgery.

Of the original 212 patients, two died from unrelated causes but had well-functioning hips at their last follow-up exam. Another two patients (two hips) had undergone revision, and one patient was lost to follow-up.

At a mean 5-year follow-up, clinical reviews were available for 208 hips and radiological reviews were available for 220 hips, according to the study. The researchers found that Harris Hip Scores averaged 95.24 points compared to 97.7 points at 3 years follow-up (P=.001). Also, the Oxford hip score averaged 14.2 points compared to 13.5 points at 3 years (P=.006).

In addition, patients had a significant change in the Short Form-12 (SF-12) physical and mental scores. SF-12 physical scores averaged 53.9 points at 3 years and 52.18 points at 5 years (P=.0003), and SF-12 mental score averaged 55.5 points at 5 years compared to 57.1 points at 3 years (P=.009), the authors reported.

There was no significant change in mean flexion with time between the 3- and 5-year follow-up points, they noted.

"Multiple regression analysis showed no correlation between the worsening HHS at 5 years; age, diagnosis, migration of the implant or the presence of radiolucent lines around the component," the authors stated.

Complications included five patients with a nerve palsy, all of which recovered by the 5-year follow-up. Also at 5 years, 52 hips (23%) experienced occasional, painless clicking and 12 hips (5.3%) had painless squeaking.

"There was no association between clicks or squeaks and radiolucent lines or migration of the femoral component," the authors wrote.

Three hips also experienced an uncomfortable 'slipping' sensation of the prosthesis while standing still, but it did not lead to instability, they added.

Radiolucent lines in zone 1 were found in four hips, and 17 hips (7.7%) had radiolucent lines around the femoral component, six of which had progressed since the 3-year review. Also, 12 hips (5.5%) developed a radiolucent area in the femoral head or neck since the 3-year review, five of which appeared to have increased in severity, according to the study.

"The cumulative survival rate at a mean of 5 years was 99.1% with two patients revised. When considering the one patient who was lost to follow-up and the two patients who had died, if a worst-case scenario is assumed of failure in these patients, the survival at 5 years is 97.8%," the authors said.

For more information:
Hing CB, Back DL, Bailey M, et al. the results of primary Birmingham hip resurfacings at a mean of five years. J Bone Joint Surg Br. 2007;89-B:1431-1438.