Tibial-stem dissociation in a modular revision total knee arthroplasty system: a comparative clinical outcome study.

Stem dissociation in modular revision knee arthroplasty, due to failure of the frictional lock of the Morse taper, has previously been reported in the literature. The medium-term to long-term implications of stem dissociation are however unknown because the clinical outcomes have not been reported. We report a series of 10 cases of tibial-stem dissociation in the Coordinate revision knee system (DePuy, Warsaw, Ind). At an average follow-up of 8.1 years (range, 6-11 years), there was no detriment to the clinical outcome in 9 cases in which there was a contained bony defect. In one case in which there was a significant medial-tibial uncontained bony defect, there was a failure of the prosthesis, which necessitated re-revision arthroplasty surgery at 4 years. We therefore question whether long canal-filling tibial stems are necessary in all revision knee arthroplasties, particularly when there is a contained bone defect together with optimal alignment and adequate support of the prosthesis, and a non-constrained-polyethylene insert is used.