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Polyethylene wear
4%
175/4882
Bearing "spin-out"
2%
83/4882
Infection
1%
32/4882
Tibial plateau stress fracture
5%
223/4882
Progression of osteoarthritis
89%
4351/4882
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The most common reason for revision surgery after a unicompartmental arthroplasty is for progression of arthritis to the contralateral (lateral compartment if a medial compartment arthroplasty is performed) and patellofemoral compartments. Unicompartmental arthroplasty is an excellent procedure with good long-term clinical outcomes if appropriate indications are used for patient selection. Common causes for revision include progression of arthritis (most common), aseptic loosening, polyethylene wear, and infection. In order to avoid progression of arthritis, is is important to under-correct the deformity and place the components in the appropriate rotation to avoid impingement. Argenson et al. evaluated 62 patients (70 knees) at a mean follow-up of 20 years after undergoing unicompartmental arthroplasty. Fourteen of the 70 knee required a revision procedure, with causes including progression of arthritis (n=12), aseptic loosening (n=2), polyethylene wear (n=5), and late infection (n=1). Price and Svard review the results of 682 medial Oxford unicompartmental arthroplasties. Of these patients, 29 had revision procedures: 10 for arthritis progression, nine for aseptic loosening, five for infection, two bearing dislocations, and three for unexplained pain. Figures A-C show radiographs of a well-fixed, well-positioned, fixed bearing, medial unicompartmental arthroplasty. Illustration A shows how over-correction of the deformity can lead to contralateral compartment arthritis. Incorrect Answers: Answer 1: Revision for polyethylene wear occurs less frequently than for progression of arthritis. Answer 2: Bearing "spin-out" is a complication of mobile bearing unicompartmental arthroplasties. The radiographs do not suggest a mobile bearing device, and additionally, this occurs with less frequency than progression of arthritis. Answer 3: Infection is a relatively uncommon reason for revision of unicompartmental arthroplasties. Answer 4: Tibial plateau stress fractures are rare and are thought to be caused by multiple drill holes used for tibial instrumentation.
4.5
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