Comparison of the iAssist™ Handheld Guidance System to Conventional Instruments for Mechanical Axis Restoration in Total Knee Arthroplasty

• Published in: The Journal of arthroplasty Vol. 33; no. 1; pp. 61 - 66
• Main Authors: Kinney, Matthew C., MD, Cidambi, Krishna R., MD, Severns, Dustyn L., PA-C, Gonzales, Francis B., MD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2018
• Subjects: Adult; Aged; Aged, 80 and over; Arthroplasty, Replacement, Knee - instrumentation; computer navigation; Female; Femur - surgery; handheld navigation; Humans; Intraoperative Period; Knee Joint - surgery; Male; mechanical axis alignment; Middle Aged; Operative Time; Orthopedics; Postoperative Period; primary total knee arthroplasty; Prospective Studies; Radiography; Stress, Mechanical; Surgery, Computer-Assisted - instrumentation; surgical technique; Tibia - surgery; Primary Total Knee Arthroplasty; Computer Navigation; Handheld Navigation; Mechanical Axis Alignment; Surgical Technique; computer navigation; handheld navigation; surgical technique; primary total knee arthroplasty; mechanical axis alignment
• ISSN: 0883-5403; 1532-8406
• DOI: 10.1016/j.arth.2017.06.004

Abstract Background Recent advances in total knee arthroplasty (TKA) include an intelligent instrument system designed to provide intra-operative guidance to reduce mechanical alignment errors. Internal position-sensing technology is integrated into microelectronic pods that attach to cutting blocks. The purpose of this prospective, randomized study was to determine if this iAssist™ system enables the surgeon to make more accurate bone resections and better restore the mechanical axis compared to conventional instruments in TKA. Methods We randomized patients undergoing TKA into two groups. Group I (n=25) underwent TKA assisted by the iAssist™ guidance system, Group II (n=25) underwent TKA using conventional instruments. Pre-operative and post-operative mechanical axes were measured from full-length lower extremity radiographs to evaluate alignment. Additional surgical parameters were also assessed, including tourniquet time and blood loss. Results Patient demographics and pre-operative mechanical axis alignments were similar between the groups. Post-operatively, 4.0% of patients had greater than 3° of tibial or femoral component mal-alignment in the guidance-assisted cohort, compared with 32.0% in the conventional group (p<0.05). Additionally, Group I showed significant improvement in variance seen in both the femoral mechanical axis (1.65 ± 0.17° vs 2.23 ± 0.33°, p<0.005) and tibial mechanical axis (1.28 ± 0.13° vs 1.71 ± 0.24°, p<0.005) compared to Group II. There were no significant differences in tourniquet time (p=0.86) or blood loss (p=0.39) between groups. Conclusion Use of the iAssist™ system in TKA results in an improved post-operative mechanical axis and decreased alignment variability compared to conventional instruments, without significantly increasing operative time.