Cost-effectiveness of a locking versus non-locking reconstruction plate in medial opening wedge high tibial osteotomy: the importance of costing perspective

Abstract

Purpose: Medial opening wedge high tibial osteotomy (HTO) is a surgical procedure for patients with medial compartment knee osteoarthritis (OA) and varus alignment. The osteotomy is stabilized using an internal plate, vital for bone healing and recovery during rehabilitation. Locking plates provide better stability and resistance to higher load bearing, resulting in an earlier return to full weight bearing and allow patients to return to work and other activities sooner. Locking plates may also decrease the number of postoperative complications related to bone healing (e.g., non-union). However, locking plates are more expensive than non-locking plates because of their material properties and their bulkiness can cause irritation, which may require surgical removal of the plate and introduce additional costs. The purpose of the study was to estimate the cost-effectiveness of a locking versus a non-locking plate in medial opening wedge high tibial osteotomy (HTO) for patients with medial compartment knee osteoarthritis. Methods: We conducted a retrospective study of patients who had undergone medial opening wedge HTO for varus malalignment and medial compartment knee OA between July 2005 and June 2015 at our institution. Patients prospectively completed the Knee injury and Osteoarthritis Outcome Score (KOOS) preoperatively and 12 months postoperatively. We calculated KOOS change scores to assess effectiveness. We reviewed medical charts for additional healthcare resource use from the time of HTO to 12 months following surgery, and obtained direct and indirect costs from hospital and provincial administrative databases. We calculated incremental cost-effectiveness ratios (ICER) and used the net benefit regression framework considering a range of willingness-to-pay (WTP) values to estimate cost-effectiveness from both the healthcare payer and societal perspectives. We used cost-effectiveness acceptability curves and (CEAC) and sensitivity analyses to account for uncertainty in our estimates. Results: 143 patients received a locking plate (49±8 years, 75% male) and 105 (47±9 years, 75% male) received a non-locking plate. Improvements in KOOS scores, surgical costs and healthcare resource use were similar between groups. Direct costs of the locking plate were greater (+$664.20). Indirect costs of the locking plate were lower (−$6228.21), attributed to faster return to full weight bearing and to work. The ICER values were $399.41 from the healthcare payer perspective and −$3745.26 from the societal perspective. From the payer perspective, the locking plate was not cost-effective for willingness-to-pay (WTP) values <$1,000 and uncertainty estimates suggest that even at a WTP ≥ $1,000, the probability that the locking plate is cost-effective is 55% (Fig. 1A). However, when we considered the societal perspective, the locking plate was cost-effective with 99% certainty regardless of WTP (Fig. 1B). As WTP increases, this certainty slowly declines as a result of cost savings with minimal improvement in effect. These findings were replicated through sensitivity analyses. Conclusions: Our results suggest that the HTO locking plate is highly likely to be cost-effective from the societal perspective, but not from the payer perspective. This is due to lower indirect costs associated with earlier return to full weight bearing and thus less time away from work, which offset the greater direct costs of the procedure. These findings highlight the importance in considering a societal perspective for economic evaluations of surgical procedures, particularly in publicly funded health-care systems.