Study backs findings that most unicompartmental knee arthroplasty failures occur in the short-term

Gulraj S. Matharu

COPENHAGEN, Denmark — Researchers from the United Kingdom have provided further evidence that most unicompartmental knee arthroplasty failures occur within 3 years to 4 years postoperatively and can be attributed to aseptic component loosening.

The findings were presented by Gulraj S. Matharu, BSc, at the 12th EFORT Congress 2011.

“A number of studies have reported the early failure of the Oxford unicompartmental knee replacement [Biomet Orthopedics Inc.], with mean time ranging from about 1.5 years to 6.6 years,” Matharu said. “Core means of failure we have seen include aseptic component loosening and disease progression in the lateral compartment … the aims of the present study were to determine the time to failure and mode of failure of the Oxford medial unicompartmental knee replacement when performed at our institution and also to look at the outcomes following revision to total knee replacement.”

Revision to cemented TKA

Matharu’s group prospectively collected data — including patient demographics, revision surgery indications and time to revision — on consecutive patients who underwent unicompartmental knee replacement (UKR) with the design and were revised to total knee arthroplasty (TKA) at their center between January 2000 and December 2009. The group also looked at clinical and radiological outcomes following the completion of revision arthroplasty.

Matharu reported that 20 of the 494 UKRs (4%) performed at his institution underwent revision to a TKA, at a mean time of 3.2 years. Reasons for revision included aseptic loosening of the femoral or tibial component, undiagnosed pain and patellofemoral pain. The mean age at the time of revision surgery was 61.8 years. Each patient was revised to a cemented TKA, and most did not require bone grafts.

Follow-up for the 20 patients ranged from 0.5 years to 5.8 years. One patient underwent a second revision TKA for instability. Furthermore, there was one superficial wound and no evidence of radiological failure.

No lateral disease progression

The study findings, Matharu concluded, are consistent with the literature in terms of early failure with UKR.

“The present study has demonstrated that the time and mode to failure for UKRs at our institution is similar to what has been seen in other studies,” he said. “The majority of our cases were due to aseptic loosening of the components and occurred within 4 years of the index procedure. However, we did not see any cases of lateral disease progression in the lateral compartments, which has been noticed by a number of other studies. Revision to total knee replacement was achieved without the need for augments and stems in 65% of cases.”

“We feel the majority of revisions performed in this series were technically relatively straightforward, and indeed in the short-term, the clinical outcome was satisfactory,” he added.

Matharu did add, however, that while the short-term outcomes appear satisfactory it is still important for longer follow-up and further studies to determine whether the results remain. – by Robert Press

References:

• Matharu G, Robb C, Baloch K, Pynsent P. Time to failure for the Oxford unicompartmental knee arthroplasty and outcome following revision. Paper #3062. Presented at the 12th EFORT Congress 2011. June 1-4. Copenhagen, Denmark.

• Gulraj S. Matharu, BSc, can be reached at Department of Trauma, Selly Oak Hospital, University Hospital Birmingham NHS Trust, Selly Oak, Birmingham, West Midlands, B29 6JD, UK; email: gsm@doctors.org.uk
• Disclosure: Matharu has no relevant financial disclosures.

Jack M. Bert

This study confirms that short-term failures are usually implant failure related, whereas longer-term failures are secondary to osteoarthritis progression in the lateral compartment or persistence of pain. Early implant failure is not necessarily related to component type or design, but can have several etiologies such as inadequate cement technique with resultant component loosening, abnormal alignment, or unrecognized arthritis with patellofemoral or contralateral compartment pain. Multiple studies have confirmed the above failure modes, and the key to long-term success with this procedure is appropriate patient selection and surgical technique.

— Jack M. Bert, MD
Orthopedics Today Business of Orthopedics Section Editor
Woodbury, Minn.
Disclosure: Bert has no relevant financial disclosures.