Hip resurfacing offers added benefits over hybrid hips in patients with osteoarthritis

Researchers expressed concern with radiographic changes in both patient groups.

Issue: Issue 2 2007

GLASGOW – Young active patients with osteoarthritis may gain greater benefit from metal-on-metal hip resurfacing than with the current gold standard of hybrid hip replacement, British surgeons reported.

In a mid-term study comparing the two techniques, researchers in Bristol, England, found excellent functional outcomes in 54 patients treated with the hybrid hip and 54 patients treated with the Birmingham Hip Resurfacing System (BHR) [Smith & Nephew Orthopaedics].

However, the BHR patients demonstrated higher UCLA activity scores and EuroQol quality-of-life scores, as well as a lower revision rate, according to Thomas C.B. Pollard, MRCS. Intermediate-term follow-up revealed Oxford Hip scores at a median 13 in the BHR group and a median 14 in the hybrid hip group.

Thomas C.B. Pollard, MRCS
Thomas C.B. Pollard

“A third of the [patients with] hybrid hips continued to participate in sport and heavy manual work against our advice. But the majority of the resurfacing patients were able to return to these activities,” Pollard said at the British Orthopaedic Association Annual Congress, held here.

Follow-up, short-term results

Researchers matched patients in the two groups based on their gender, age at surgery (average, 50 years), body mass index and preoperative activity levels, Pollard said. They evaluated the hybrid hip patients at an average 80 months postoperatively and the BHR patients at an average 61 months postoperatively.

Surgeons permitted full mobilization and full weight-bearing for all patients on the first postoperative day. However, “Hybrid hips [patients] were advised to permanently avoid heavy manual work and impact activity because of concern regarding polyethylene wear,” Pollard said. “The resurfacing patients were unrestricted after 3 months.”

In the patients with hybrid hips, researchers found that “Polyethylene wear was present in over half the cases, and nine cases (18%) had periarticular osteolysis,” Pollard said.

Researchers found no sign of acetabular loosening in the BHR patients but 60% demonstrated pedestal signs and 10% experienced migration of the femoral component.

Researchers found polyethylene wear and periarticular osteolysis in the hybrid hip patients, as seen here.

This image demonstrates the pedestal or sclerotic signs that the researchers found in 60% of the resurfacing group patients. Further study is required to determine their significance, Pollard said.

Images: Pollard TCB

Revisions and intent to revise

Surgeons revised or planned to revise 8% of patients in the hybrid hip group, including three osteolysis cases and one dislocation. The BHR group had a 6% revision/intent-to-revise rate, including three fractures and one painful migration, Pollard said.

Researchers also determined impending failure, which was 12% in the hybrid hip group, based on further osteolysis and future revision as a consequence of unadvised activity rates.

“In the resurfacing group, it was 8%, and that figure was calculated from the remaining four hips with migration which aren’t yet painful but we anticipate will become so at some stage,” Pollard said.

He added: “The radiographic changes we observed in the resurfacings are cause for concern, especially if they represent osteonecrosis. Obviously, further study is required to define their etiology and progression.”

Median functional results at intermediate-term follow-up
At 5- to 7-year follow-up, researchers found similar excellent functional results between young active osteoarthritic patients treated with either a hybrid total hip arthroplasty or resurfacing (Birmingham Hip Resurfacing System).

Activity participation within 4 weeks before evaluation
Despite the excellent functional results, resurfacing patients were more active than the hybrid hip patients after surgery. However, these activity numbers for hybrid hip patients are of concern, because surgeons advised these patients to permanently refrain from sports and heavy manual labor.

Source: Pollard TCB

For more information:
Pollard TCB, Baker RP, Eastaugh-Waring SJ, Bannister GC. Treatment of the young active patients with osteoarthritis of the hip: A 5- to 7-year comparison of hybrid total hip replacement and metal-on-metal resurfacing. #138. Presented at the British Orthopaedic Association Annual Congress. Sept. 27-29, 2006. Glasgow.
Pollard TCB, Baker RP, Eastaugh-Waring SJ, Bannister GC. Treatment of the young active patients with osteoarthritis of the hip: A 5- to 7-year comparison of hybrid total hip replacement and metal-on-metal resurfacing. J Bone Joint Surg Br. 2006;88-B:592-600.
Thomas C.B. Pollard, MRCS, Oxford University, Nuffield Orthopaedic Center, Old Road, Headington, Oxford OX3 7LD, England; +44-1865-741155; tom.pollard@ndos.ox.ac.uk. He has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.