Muscle Atrophy Can Drive Healthcare Costs, Outcomes in Total Knee Replacement Surgery

Orthopedic surgeons perform total knee replacement (TKR) surgery seven times more often today than they did in the early 1970s. Now, experts expect that by 2030, six times as many more TKR surgeries will be performed compared to today. About three-quarters of all TKR surgeries are performed on Medicare beneficiaries, making TKR a hot topic for insurers and health economists. The average TKR cost more than $13,000 in 2004 dollars, and the United Stated spent $6.3 billion on TKR in 2004.

TKR patients often approach their surgeries with quadriceps muscle atrophy/weakness (MAW). As pre-existing MAW can slow recovery and worsen function for up to two years after surgery, a team of researchers published a study answering the question, “What are the differences in healthcare resource use, costs, or other medical outcomes between TKR patients with and without MAW?”

The investigators conducted a retrospective, naturalistic study using eligibility records and administrative claims from 33 million patients — 3 million of whom were Medicare beneficiaries. The study authors calculated total direct medical, inpatient, outpatient, and pharmacy costs adjusted to 2011 US dollars among three cohorts of patients: no MAW (as the reference cohort), MAW before TKR (pre-MAW), and MAW during or after TKR (post-MAW).

The study identified 53,696 commercially-insured patients between the ages of 50 and 64 and 46,058 Medicare beneficiaries aged 65 or older. More than 94 percent of the patients sought TKR surgery as a result of osteoarthritis, and among both study populations, the prevalence of pre-MAW and post-MAW was similar (0.9 percent to 1.1 percent and 4.2 percent to 4.6 percent, respectively). The study reported shorter hospitalizations than previous studies, which was expected given today’s more effective surgical techniques and greater reliance on community-based rehabilitation.

Patients with MAW had higher healthcare utilization and costs than those without MAW, thus identifying MAW as a key cost driver in TKR surgery. Regardless of insurance type, patients with pre- or post-MAW had significantly higher total healthcare costs. In both cohorts, the control groups’ total costs were approximately 60 percent less than those among the pre- and post-MAW cohorts. For one year following surgery, patients who developed MAW during or after TKR had the greatest increase in healthcare costs, followed by patients with no MAW.

The authors said more research is needed to determine whether certain interventions or management techniques could improve outcomes and control costs.