OBJECTIVES: Prices of implants used in total knee replacement (TKR) vary widely. Key implant features are fixation, constraint, materials, and bearing mobility. Cemented, cruciate retaining, metal-on-polyethylene, fixed bearing implant constructs are the most used, but it is not known which combination is the most cost-effective.

METHODS: We assessed the cost-effectiveness of 12 constructs using a discrete lifetime Markov model for women and men aged 0-55, 55-64, 65-74, 75-84, and 85+ years. The probabilities that patients required one or more revision surgeries or died were estimated from analysis of over 1 million patients in the National Joint Registry (NJR). Other inputs included implant prices (NJR Price Benchmark database), revision costs (National Collection of Costs), and utilities (Patient Reported Outcome Measures data in England). The model was fully probabilistic and implemented in R. We estimated the expected value of partial perfect information (EVPPI) to identify key drivers of decision uncertainty.

RESULTS: For each patient group, the top three cost-effective implants have similar costs and quality-adjusted life years. The cemented, cruciate-retaining, metal-on-polyethylene, fixed construct was the most cost-effective construct for men and women of all age groups (e.g., net monetary benefits for males 65-74= £166,397; 95%CI £162,102, £170,238), followed by the posterior stabilised version for all except men aged 75-84 years, and the cruciate retaining, mobile version as third for all except men aged >75 years. Results are robust to a wide range of sensitivity analysis, but uncertain, with all constructs having low probabilities of being the most cost-effective choice. Long-term revision rates are the most uncertain parameters with highest EVPPI (up to £150 million).

CONCLUSIONS: Most implant constructs have similar cost-effectiveness profiles, with no evidence that any combination is better than the most used cemented, cruciate retaining, metal-on-polyethylene, fixed construct. There was more uncertainty in choice for men older than 75 years.