As the popularity of unicondylar knee arthroplasty (UKA) and patello-femoral arthroplasty (PFA) have expanded more patients who have limited arthritis are undergoing partial knee arthroplasty. These procedures are performed by arthroplasty, sports medicine, and general orthopaedic surgeons alike, and with the rise in ambulatory surgery centers and utilization of robotic-assisted surgery around the county, these procedures have become much more attractive, especially for younger, active patients. However, no studies have evaluated if any regional differences in the United States (U.S.) exist between partial vs total knee arthroplasty. The purpose of this study was to utilize the American Joint Replacement Registry (AJRR) to evaluate regional differences in UKA, PFA, and TKA.
The AJRR was queried for all TKA, PFA, and UKA procedures between 2012 and 2021. Surgical volume was compared between the Midwest (MW), Northeast (NE), South (S), and West (W) regions. Procedure volume was normalized as a percentage of all arthroplasty performed in each region, as well as normalized to the population of each region. To account for fluctuations in population we used annual population and housing estimates provided by the United States Census Bureau for the years 2012 through 2021. Other parameters collected included cases performed at teaching vs. non-teaching hospitals, institution size, practice type, and rural vs urban practice. Trends were compared using multivariate logistic regression analyses and least squared mean logistic regression models.
Since 2012, there has been a steady increase in the amount of UKAs performed across the U.S., except during the COVID-19 pandemic when numbers decreased. This trend persisted when data was normalized to population changes over the study period. Logistic regression analyses demonstrated a higher likelihood of receiving a UKA compared to TKA in the NE compared to other regions, and higher likelihood of receiving a PFA in the NE and West compared to other regions over the study period. Other factors that increased the likelihood of having a UKA nationally were men, the procedure being performed at a teaching hospital, and having surgery in urban areas. Analyses further demonstrated a higher likelihood of receiving PFA in the NE compared to the S and MW, and higher odds in the S and W compared to the MW, with rates of PFA consistently lower in the MW compared to other regions.
Patients were more likely to have a UKA in the Northeast compared to other regions of the country when normalized to population. Patients had higher odds of having a PFA in the Northeast and West regions relative to the Midwest. Men had higher odds of having either UKA or PFA than women across the nation.

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