5-year cost/benefit analysis of revision of failed unicompartmental knee replacements (UKRs); not “just” a primary total knee replacement (TKR)

A number of studies suggest that one advantage of a unicompartmental knee replacement (UKR) is ease of revision to a total knee replacement (TKR). We aimed to perform a cost/benefit analysis of patients undergoing this procedure at our centre to evaluate its economic viability.

From our own prospective joint replacement database we identified 812 consecutive tibio-femoral UKRs performed (1994–2007) of which 23 were revised to TKR (2005–2008). These were then matched to a cohort of primary TKRs (42 patients). Data were collected regarding patient demographics, cost of surgery, clinical outcome (OKS) and follow-up costs at five years.

There was no significant difference in implant costs or in length of stay, however tourniquet time was significantly higher in the revision group (average 93 min (UKR) vs 75 min (TKR) p < 0.0001).

At five years there was no significant difference in clinical outcome between the revision UKR and primary TKR groups, mean OKS 27 and 32 respectively (p = 0.20). The revision group had a greater complication and revision rate, attending significantly more follow-up appointments (average 6 (UKR) vs 2 (TKR) p < 0.0001) and consultant appointments (average 4 (UKR) vs 0.4 (TKR) p < 0.0001). This was translated to significantly higher follow-up costs.

Revision of UKR to TKR is not universally a straightforward procedure comparable to a standard primary replacement. Despite cost of components not being significantly higher than primary TKR there are multiple hidden follow-up costs. The clinical outcomes are however similar at 5 years.