To evaluate the cost-effectiveness of incorporating tramadol or oxycodone into knee osteoarthritis (OA) treatment.
We used the Osteoarthritis Policy Model to evaluate long-term clinical and economic outcomes of knee OA patients with a mean age of 60 years with persistent pain despite conservative treatment. We evaluated 3 strategies: opioid-sparing (OS), tramadol (T), and tramadol followed by oxycodone (T+O). We obtained estimates of pain reduction and toxicity from published literature and annual costs for tramadol ($600) and oxycodone ($2,300) from Red Book Online. Based on published data, in the base case, we assumed a 10% reduction in total knee arthroplasty (TKA) effectiveness in opioid-based strategies. Outcomes included quality-adjusted life years (QALYs), lifetime cost, and incremental cost-effectiveness ratios (ICERs) and were discounted at 3% per year.
In the base case, T and T+O strategies delayed TKA by 7 and 9 years, respectively, and led to reduction in TKA utilization by 4% and 10%, respectively. Both opioid-based strategies increased cost and decreased QALYs compared to the OS strategy. Tramadol's ICER was highly sensitive to its effect on TKA outcomes. Reduction in TKA effectiveness by 5% (compared to base case 10%) resulted in an ICER for the T strategy of $110,600 per QALY; with no reduction in TKA effectiveness, the ICER was $26,900 per QALY. When TKA was not considered a treatment option, the ICER for T was $39,600 per QALY.
Opioids do not appear to be cost-effective in OA patients without comorbidities, principally because of their negative impact on pain relief after TKA. The influence of opioids on TKA outcomes should be a research priority.