In today’s medical world, we are expected to be near-perfect diagnosticians as well as surgeons. No one told us that we would have to be counselors and small-business owners as well as economists. Cost-effective is a term bandied about that means “I am supposed to pick the least costly alternative assuming all outcomes are the same.” This seems straightforward until we recognize that all treatments do not have identical outcomes achieved for the same length of time and with identical complication rates.

And this is where we jump into being economists, with terms like ICER (incremental cost-effectiveness ratio) and QALY (quality-adjusted life-year) written and talked about with the same nonchalance that we orthopaedists toss about terms like OCD (osteochondritis dissecans) and SLAP (superior labral anterior-posterior) lesions. What we really want is a long-term study comparing similar populations undergoing one of three operations—high tibial osteotomy (HTO), unicompartmental knee arthroplasty (UKA), or total knee arthroplasty (TKA)—and comparing outcomes, revision rates, and long-term costs. Alas, that is unlikely to ever happen, so the authors of “The Cost-Effectiveness of Surgical Treatment of Medial Unicompartmental Knee Osteoarthritis in Younger Patients: A Computer Model-Based Evaluation” have attempted to do so using a computer model.

As with any computer model, it is important to remember all of the assumptions that go into making the model but also not to let those “if” statements prevent the reader from drawing important conclusions. The authors wisely point out that if certain assumptions change (such as the conversion rate of HTO to TKA changing from 2.3% to 2.6% annually), then the conclusions change as well. We also need to remember that not all patients with unicompartmental arthritis (e.g., those with obesity) are candidates for an HTO.