The cost-effectiveness analysis of platelet-rich plasma (PRP) for knee osteoarthritis by Rajan et al. in the September 16, 2020 issue of JBJS is accompanied by 105 references. That’s just one indication of the level of interest in this anti-inflammatory and pro-angiogenic orthobiologic. Current literature suggests that PRP is safe, but its clinical efficacy in musculoskeletal conditions has been hotly debated in the orthopaedic community.
Rajan et al. applied Markov decision analysis to a clinical scenario in which a 55-year-old patient with Kellgren-Lawrence grade-II or III knee osteoarthritis (OA) undergoes either a series of 3 PRP injections and a 1-year delay to total knee arthroplasty (TKA), or TKA from the outset. Their primary outcome measures were total costs and quality-adjusted life years (QALYs), organized into incremental cost-effectiveness ratios (ICERs). In Markov analyses, if one treatment costs less and produces more QALYs than a comparative treatment, it is considered to be the “dominant” approach.
The authors found that, from a health-care payer perspective, PRP (at an estimated cost of $728 per injection in 2018 US dollars) was not cost-effective if it yielded only a 1-year delay of TKA. However, from a societal perspective (which considered both lost productivity and the need for unpaid caregiving associated with TKA surgery), PRP was cheaper over a lifetime because it delayed direct and indirect costs associated with TKA. The ICER for TKA at the outset was $4,175 per QALY, which is well below the predetermined willingness-to-pay threshold of $50,000. The authors emphasize that this favorable ICER reflects the improved quality of life after TKA compared with published results of PRP injections for knee OA.
Rajan et al. do specify a clinical scenario in which PRP may have a cost-effectiveness advantage over TKA: “…in a higher-risk patient population in whom the perioperative complication rates, TKA revision rate, or postoperative functional outcomes are projected to be worse.”
The two numbers that you’ll want to remember from the computer model-based cost-effectiveness study by McLawhorn et al. in the January 20, 2016 Journal of Bone & Joint Surgery are $13,910 and $100,000. The first number is an incremental cost-effectiveness ratio (ICER). Here, it’s the estimated added cost per quality-adjusted life year (QALY) for morbidly obese patients (BMI ≥35 kg/m2) with end-stage knee osteoarthritis who undergo bariatric surgery two years prior to total knee arthroplasty (TKA), compared with similar patients who undergo immediate TKA.
The $100,000 is the threshold “willingness to pay” (WTP) that the authors used in their evaluation. Willingness to pay reflects the amount society and healthcare payers such as Medicare and private insurers are willing to pay for a patient to accrue one year lived in perfect health.
Here’s another way to view these findings: Morbidly obese patients who undergo TKA are at increased risk for wound-healing problems, superficial and deep infections, early revision, and poor function. The authors estimated that if bariatric surgery reduces the TKA risks in these patients by at least 16%, on average, the combination of bariatric surgery followed by TKA is more cost-effective than immediate TKA alone.
Because the ICER was much less than the WTP in this model, the authors conclude that “bariatric surgery prior to total knee arthroplasty may be a cost-effective option for improving outcomes in motivated patients with a BMI of ≥35 kg/m2 with end-stage knee osteoarthritis.” However, they are quick to add that “decision modeling cannot simulate reality for every clinical situation.” While this rigorously developed model may provide a decision-making framework for surgeons and policymakers, the authors say, “this approach may be impractical for an individual patient…desiring immediate symptomatic relief from knee osteoarthritis.”