Blood transfusion, hospital stay and learning curve in robotic assisted total hip arthroplasty.

Total Hip Arthroplasty (THA) has been defined the surgical procedure of the century considering its outcome and cost-benefit ratio (1). Both standard and robotic assisted procedures are increasing, thus, comparison between standard and robotic surgery become useful to understand the cost-benefit of the latter. The prerequisites of the robotic assisted arthroplasty are precision, accuracy, limitation of errors and safety but, on the other hand, its cost is the main drawback. The primary endpoint of our research was to evaluate differences in terms of blood transfusion rates between standard manual and robotic arm assisted THA. All the robotic procedures have been managed using semi active Robotic Arm interactive orthopaedic System (RIO® MAKO Stryker surgical corporation) in a group of patients who underwent primary uncemented total hip arthroplasty (THA) for osteoarthritis or avascular necrosis. Secondary endpoints were the evaluation of length of hospital stay (LOS), age category, gender and the impact of the learning curve on surgical time in the robotic surgery sample. Our retrospective cohort study was conducted between July 2014 and December 2018. Data have been collected from the Tuscany regional hospital discharge register, extracting the relative Hospital Discharge Forms (SDO). During the period of the study, 1537 patients underwent uncemented total hip arthroplasty for osteoarthritis or avascular necrosis. The sample was divided in two subgroups: 1142 patients (74.3%) operated on with standard manual technique and 395 patients (25.7%) operated on with Mako- Stryker Robotic System. In the descriptive analysis, the average values of age and days of hospitalization with 95% CI were calculated. Mean significance was assessed by the T student test. The association between surgical modality and gender was assessed with the chi-square test. The multivariate logistic regression model was used to evaluate the risk of transfusion (outcome variable), between conventional and robotic surgical techniques. The significance threshold was set up at p <0.05. During the period of the study we observed a decrease in standard surgery and an increase in robotic surgery; an increasing number of women per year underwent total uncemented total hip arthroplasty. We found a statistical significance in favor of robotic procedures in terms of transfusion percentage (OR 6.10, 95% CI 2.96-12.59, p<0,001), highlighting the greatest risk in women (OR 1.90, 95%CI 1.30-2.78, p=0.001 ), length of hospital stay (Mr=4.24, SD=2.04, 95% CI 4.04-4.44) (Ms=8.04, SD=2.84, 95%CI 7.88-8.21), (p<0.01). Operative time in the robotic sample decreased substantially with the rise of surgical experience (106.75±13.4 mins in 2014; 82.79±15.95 mins in 2018) (p<0.01). Since the Robotic procedure is a technologically demanding process, an adequate surgical learning curve is mandatory. Our paper, comparing conventional vs robotic assisted THA, showed in favor of the robotic one, a statistically significant reduction of number of transfusions (p<0.001) and length of hospital stay (p<0.01).