Evaluating the Baseline Risk Factors and Post-operative Outcomes of Patients Internally Referred to a Subspecialist Surgeon for Total Knee Arthroplasty: A Pilot Study

INTRODUCTION Orthopaedic surgeons who perform primary total knee arthroplasty (TKA) may often refer more complex patients to specialty-trained arthroplasty surgeons for definitive treatment. While this practice is often appropriate for optimal patient care, these internal referrals may represent a population that is associated with higher baseline risk and worse outcomes. This study aims to identify the risk factors and outcomes associated with primary TKA patients who are referred to subspecialists. METHODS This is an IRB-approved retrospective cohort study of all patients who underwent primary elective total knee arthroplasty by a fellowship trained adult reconstruction surgeon from 2020-2022 in a high-volume tertiary referral urban orthopaedic hospital. Internal referrals were defined as patients referred from same practice surgeons who perform primary TKAs to the subspecialist surgeon. Controls were patients who came to the subspecialist surgeon independently or from referral by a physician who does not perform TKAs. RESULTS The internal referral group had a significantly higher rate of chronic kidney disease requiring hemodialysis (1.7% vs. 0%, p = 0.02). However, other preoperative risk factors including type 1 diabetes, osteoporosis, and retained knee hardware failed to meet statistical significance. Post-operatively, unscheduled clinic visits and office contacts were also not found to be statistically significant. However, internal referrals experienced higher 90-day knee-related readmissions (19.2% vs. 10.6%, p = 0.02), reoperations (22.5% vs. 14.7%, p = 0.04), and manipulations under anesthesia due to stiffness (15% vs. 9.1%, p = 0.04). CONCLUSION While the results of this study indicate that internally referred patients undergoing primary TKA do not have a more complex preoperative risk profile, they may experience higher rates of certain adverse postoperative outcomes compared to their control counterparts. This study can serve as a pilot for future studies that are better powered or designed to detect a difference among internal referrals and further support these findings.