Jump in Elective Total Hip and Knee Arthroplasty Numbers at Age 65 Years: Evidence for Moral Hazard?

Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are outstanding options for many older patients at the discretion of the patient and the surgeon. As patients turn 65 years, greater than 98% of the US population becomes eligible for Medicare, and this represents a time of changing healthcare coverage for many.

Patients undergoing elective TKA and THA were abstracted from the 2012 to 2018 National Surgical Quality Improvement Program database. Incidences of TKA and THA (combined and separate) were plotted and assessed by age. To assess factors associated with who "delayed" surgery until 65 years, demographic and preoperative characteristics, and postoperative adverse events were compared for the 2 years above and the 2 years below the 65-year-old mark with multivariate analysis. Significance was set at P < 0.05.

In total, 515,139 TKA and THA patients were identified (62.04% TKA and 37.95% THA). When the number of procedures was plotted by age, a discontinuity in the bell-shaped curve was noted at age 65 years. Highlighting this finding, the changes in percent population between 63 and 64 years was -1.52%, between 64 and 65 years was +15.36%, and between 65 and 66 years was -2.32%. Relative to those who were 63 and 64 years (n = 36,511), those who were 65 and 66 years (n = 41,671) were more likely to be female, be non-Hispanic White, have a lower body mass index, and have a lower functional status but were not different in the preoperative American Society of Anesthesiologists class.

In this large national sample, there was a clear step increase in undergoing TKA or THA once patients reached the age of 65 years (Medicare eligibility). This discontinuity in the bell-shaped curve may be evidence for a moral hazard in healthcare markets. Although factors in decision-making were not assessed, there were demographic factors associated with this step finding.