A NOVEL MULTI-AXIS ROBOT-BASED MINIMALLY INVASIVE SPHERICAL OSTEOTOMY SYSTEM (MISOS) IMPROVES THE ACCURACY AND REPRODUCIBILITY OF RESULTING SURFACE

Spherical osteotomy is less invasive and more precise than the traditional osteotomy in the orthopedic surgery. However, the manual spherical osteotomy is still lacking of reliable controllability and precision. Herein, a minimally invasive spherical osteotomy assistant system (MISOS) based on a multi-axis surgical robot was designed to improve it. The MISOS consists of a navigation, an optical positioning subsystem, and a manipulator. The manipulator also includes a specially designed dome saw and a power source. The spherical osteotomic trajectory can be realized by the spherical center calibration and manipulator control algorithm. By using sawbone models of human acetabulum, femur, and tibia, the feasibility of MISOS assistant spherical osteotomy was verified, comparing with the conventional freehand spherical osteotomy. The deviation of osteotomic center and the section curvature were applied as the main parameters for the reproducibility and accuracy measurements. The center deviation of MISOS versus freehand spherical osteotomy was 1.48±0.93 mm v.s. 11.15 ± 3.97 mm in the acetabulum, 3.12 ± 0.75 mm v.s. 8.81 ± 3.04 mm in the femur, and 1.91 ± 0.84 mm v.s. 7.33 ± 1.53 in the tibia, respectively. The standard deviation of the osteotomy offset in the MISOS group was maintained within 1.0 mm, whereas it was as high as 3.97 mm in the manual group, indicating a onsiderably superior stability of osteotomy performed with MISOS. On the other hand, the MISOS group could obtain a relative smoother ostemotomic surface. The curvature deviation of MISOS versus freehand spherical osteotomy was 1.40 ± 0.08 mm v.s. 3.16 ± 0.56 mm in the acetabulum, 0.26 ± 0.07 mm v.s. 0.491 ± 0.21 mm in the femur, and 0.21 ± 0.02 mm v.s. 0.46 ± 0.18 in the tibia, respectively. These results indicate that MISOS can assist surgeon in completing accurate and stable spherical osteotomy. The MISOS system has the potential to become a more accurate assistant tool for minimally invasive orthopedic spherical osteotomy and possesses broader clinical application prospects.