Does a non-stemmed constrained condylar prosthesis predispose to early failure of primary total knee arthroplasty?

PURPOSE: The use of unlinked constrained condylar components (CCK) has been extended to primary total knee arthroplasty (TKA); however, there is limited literature on its outcomes. The purpose of this retrospective cohort study was to assess clinical outcomes of one particular design of primary, non-stemmed, unlinked constrained TKA and to compare them with a control group of PS-TKA utilizing the same implant design.

METHODS: The clinical and radiographic outcomes of 486-cemented, non-stemmed, primary TKA's performed by two surgeons at one institution using similar surgical algorithm, technique and prosthetic design were retrospectively reviewed. Primary TKA components were used in all knees; the only difference between groups was the type of polyethylene inserts used (CCK vs PS). Pre-operative deformity, knee society scores (KSS), range-of-motion (ROM), radiographic data and revision rates were compared.

RESULTS: Both groups had comparable demographics, pre-operative coronal plane alignment, ROM and KSS. At a mean follow-up of 3.5 years, no difference was found in ROM, KSS, radiographic outcomes and revision rates.

CONCLUSIONS: Cemented, primary, non-stemmed CCK-TKA offered comparable clinico-radiographic results to PS-TKA at short-term follow-up. Use of a semi-constrained insert without additional stems did not predispose to failure due to aseptic loosening with this implant design. Moreover, the rate of revision due to instability was lowered.

LEVEL OF EVIDENCE: Retrospective cohort study, Level III.