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Unicompartmental knee arthroplasty can be converted to a patient’s advantage
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Achieving a primary outcome with revision unicompartmental knee arthroplasty is possible, but according to a researcher, surgeons need to understand the typical pitfalls and possible failure modes for the procedure to give their patients a better chance at a quality long-term outcome.
Christopher A. Dodd, MB, FRCS, of Oxford, United Kingdom, presented several suggestions to help surgeons avoid a failed unicompartmental knee arthroplasty (UKA) in their patients.
“The first and most common tip is to avoid unnecessary pain. As with a total knee replacement, do not revise for unexplained pain. Three-quarters of unicompartmental knee arthroplasties revised for unexplained pain failed to improve. We have shown that in an interesting study, which shows the revision is easy. You must resist that temptation,” Dodd said.
Revisions may be necessary
“UKA has gained increasing popularity in the last 5 years and is appropriate in up to 30% of patients requiring knee replacement,” Dodd told Orthopaedics Today Europe.
Postoperative Oxford knee scores from a New Zealand study at 6 postoperative months showed that UKA has a five times higher failure rate compared to total knee replacement (TKR). Pain should not be the driving force for a revision, Dodd said at a meeting, and it should be treated conservatively.
Surgeons also must be wary of tibial loosening and radiolucency, which can be indicative of infection, he said. A chronic infection will present early with lateral joint space narrowing or clear pathological radiolucency. One of the most common reasons for failure of a UKA is a misdiagnosis of a painful radiolucency, which can lead to unnecessary revision.
If revision of a UKA is necessary, Dodd said at a meeting surgeons should be aware of several difficult revision settings.
“Poorly performed tibial preparation with a stress fracture can leave a nightmare of a revision,” Dodd said at a meeting. In such a situation, patients are likely to require metaphyseal cones or tibial stems with standard augments, so they can be difficult procedures, he noted.
Primary outcomes for UKA
Dodd said the most common reasons for UKA failures in 20 years were lateral compartment progression and component loosening. Pain often led to revisions as well. The majority of revisions could be converted to a primary TKR prosthesis, and occasionally revision TKR implants were required.
To achieve a primary outcome when revising a UKA, Dodd said, “Treat unexplained pain expectantly, beware [of] normal radiolucency, and avoid unnecessary surgery. During surgery, careful attention needs to be paid when dialing in femoral component rotation. Infection and failed tibia plateau fracture usually require revision components with tibial stems. Most other revisions require primary total knees, usually with a 2-mm thicker poly insert. Those treated with primary components have results approaching primary total knees, unless revised for unexplained pain. Do please beware of unexplained pain.” – by Robert Linnehan
- Reference:
- Dodd CA. Paper #45. Presented at: Current Concepts in Joint Replacement Spring Meeting; May 18-21, 2014; Las Vegas.
- For more information:
- Christopher A. Dodd, MD, FRCS, can be reached at the Oxford Knee Group, Oxford Orthopaedics, Manor Hospital, Beech Road, Headington, Oxford, OX3 7RP, United Kingdom; email: christineprior@privatepractice.co.uk.
Disclosure: Dodd receives royalties from Biomet for speaking, teaching, funding for consulting and intellectual property.