Opioid Use in Robotic-Arm Assisted Total Knee Arthroplasty: A Comparison to Conventional Manual Total Knee Arthroplasty

Introduction: Opioids are frequently prescribed in the postoperative management of total knee arthroplasty (TKA) with multiple factors influencing postoperative opioid use. Robotic-arm-assisted TKA (raTKA) was developed with the goal of improving alignment and outcomes while decreasing soft tissue injury. The purpose of this study was to compare postoperative opioid consumption in raTKA and conventional manual TKA (mTKA) cohorts. Materials and Methods: A consecutive series of unilateral primary TKAs performed 1/1/16 to 12/31/17 were included. Patients with major procedures requiring opioids occurring within one year of TKA were excluded. A single-surgeon raTKA cohort of 127 patients (Group 1) was compared to a same-surgeon cohort of 119 mTKAs (Group 2) using the same cemented implant design and a two-surgeon cohort of 410 mTKA (Group 3). Groups were subdivided into opioid naive (ON) and opioid exposed (OE). Length of hospitalization and postoperative opioid utilization up to one year were compared between groups and collectively without separating raTKA and mTKA. Statistical analysis included Chi-square, Student's t-test, and Wilcoxon rank sum tests. Results: For both ON and OE patients, Group 1 demonstrated reduced inpatient mean daily oral morphine milligram equivalent (MME) compared to Group 3 (ON p=0.007; OE p=0.034), a shorter hospitalization compared to Group 2 (ON p=0.02; OE p=0.012), and fewer opioids prescribed at discharge compared to Group 2 (ON p= 0.005; OE p=0.081) and Group 3 (ON p<0.001; OE p=0.036). No differences in opioid prescriptions were seen at three months or after. Regardless of surgical technique OE patients had higher inpatient opioid utilization (p<0.001) as well as cumulative outpatient prescription quantity (MME 1050 ON, 2660 OE) and duration (ON 0.5%; OE 28.3%) at one year (p<0.001). Conclusion: Less opioids were prescribed at discharge and used during hospitalization in raTKA compared to mTKA though no differences in opioid use were seen at further time points. Preoperative opioid use remains a dominant factor in postoperative opioid utilization regardless of TKA surgical technique.