Do bone loss and reconstruction procedures differ at revision of cemented unicompartmental knee prostheses according to the use of metal-back or all-polyethylene tibial component?

INTRODUCTION: Results of unicompartmental knee arthroplasty (UKA) revision are known but the severity of bone loss and the need for reconstruction are not detailed for different tibial implants.

HYPOTHESIS: Metal-backing UKA revision exposes the patient to more severe tibial bone loss and requires more substantial reconstruction procedures than cemented polyethylene UKA revision.

MATERIALS AND METHODS: This retrospective series of 23 revisions of UKA to total knee arthroplasty (TKA) compared 11 all-polyethylene UKAs with 12 metal-backing UKAs. Factors that contributed to failure were aseptic loosening (n=12) and osteoarthritis evolution (n=11). Both groups were similar regarding the demographic and clinical features. We reported bone loss and the reconstruction procedure to fill it according to the initially used tibial implant. The results were evaluated with the IKS score to a follow-up of 37 months (range, 24-67 months).

RESULTS: There were more tibial segmental bone loss (10 versus 3) and more metal wedges (8/12 versus 2/11) in metal-backing UKA revision (P<0.05). Tibial stems were more often used in metal-backing UKA revision (12/12 versus 7/11) (P=0.04). The results of TKA at follow-up did not differ according to whether the revised tibial implant was all polyethylene (IKS=155 [range, 107-195]) or metal-back (IKS=155 [range, 127-172]).

DISCUSSION: This study suggests that metal-backing UKA revision exposes the patient to more severe tibial bone loss requiring more substantial reconstruction. These results must be confirmed on a larger population, but surgeons should be alerted to this kind of revision surgery, which warrants having available a revision knee prothesis.

LEVEL OF EVIDENCE: Level III, case-control study.