Study Design: Economic evaluation alongside a prospective, randomized, controlled trial from a 2-year NHS perspective.

Objective: To determine the cost-effectiveness of Titanium Cages (TC) compared to Femoral Ring Allografts (FRA) in circumferential lumbar fusion.

Summary of background data: A randomised controlled trial has shown the use of TC to be clinically inferior to the established practice of using FRA in circumferential lumbar fusion. Health economic evaluation is urgently needed to justify the continued use of TC, given that this treatment is less effective and, all things being equal, more costly than FRA.

Methods: Eighty-three patients were randomly allocated to receive either the TC or FRA as part of a circumferential lumbar fusion between 1998 and 2002. NHS costs related to the surgery and revision surgery needed during the trial period were monitored and adjusted to the base year (2005/6 pounds sterling). The Short Form-6D (SF- 6D) was administered preoperatively and at 6, 12 and 24 months in order to elicit patient utility and subsequently Quality-Adjusted Life Years (QALYs). Return to paid employment was also monitored. Bootstrapped mean differences in discounted costs and benefits were generated in order to explore cost-effectiveness.

Results: A significant cost difference of £1,942 (95% CI £849 to £3,145) in favour of FRA was found. Mean QALYs per patient over the 24 month trial period were 0.0522 (SD 0.0326) in the TC group and 0.1914 (SD 0.0398) in the FRA group, producing a significant difference of 0.1392 (95% CI 0.2349 to 0.0436). With regard to employment, incremental productivity costs were estimated at £185,171 in favour of FRA.

Conclusion: From an NHS perspective, the trial data show that TC is not cost-effective in circumferential lumbar fusion. The use of FRA was both cheaper and generated greater QALY gains. FRA patients reported a greater return to work rate.

The use of distal femoral centralising devices has been advocated in order to achieve an even cement mantle. This has been shown to improve femoral component survival but it is recognised that the presence of voids in the mantle has a deleterious effect on the mechanical strength of cement at laboratory testing and in terms of implant survival. The effect of centralising devices on the mantle in relation to the timing of stem insertion has not previously been investigated.

The purpose of this study is to assess the quality of the cement mantle in artificial bone using a polished taper stem with centralisation inserted at different stages of cement cure time and using different cements.

Three cement types were studied, 45‘saw bone’ models were used. The cementation was carried out in an operating theatre at constant temperature of 23.2Ê°C. The cement was mixed according to the manufacturers instructions and pressurised. Early, intermediate and late stem insertion times were determined for each cement type. The late group included stems with and without centralisers. Video recordings of the stem cement interface were made with a 4 mm endoscope after stem removal. Large cement mantle defects were noted in the ‘with centraliser’ group in 7 out of 15 late insertion times and all had small defects in the mantle. None of the ‘without centraliser’ group had cement mantle defects.

Based on our results we advise surgeons to be very aware of the timing of stem insertion when using centralisers.