Asymmetry of Twisting and Range of Motion in the Transverse Plane: A Fully Automated 3D Surface Topographic Measurement of AIS Patients

Benjamin Groisser ¹ Emily Wong ³ Howard Hillstrom ³ Ankush Thakur ² Hila Otremski ⁵ Kira Page ² Kyle Morse ² Matthew Cunningham ² Michael T. Hresko ⁴ Ron Kimmel ⁶ Alon Wolf ⁷ Roger Widmann ²

¹Biorobotics and Biomechanics Laboratory, Technion-Israel Institute of Technology, Israel
²Orthopedics, Hospital for Special Surgery, USA
³Rehabilitation, Hospital for Special Surgery, USA
⁴Orthopedic Surgery, Boston Children's Hospital, USA
⁵Pediatric Orthopedic, Dana Dwek Children's Hospital, USA
⁶Computer Science, Technion-Israel Institute of Technology, Israel
⁷Mechanical Engineering, Technion-Israel Institute of Technology, Israel

Surface topographic scanning has limited use in orthopedics to date. Adolescent Idiopathic scoliosis (AIS) may be a potential application for 3D surface topographic scanning in pediatric orthopedics. Two topographic parameters, the asymmetry of twisting and ROM in the transverse plane have received limited attention in the literature although scoliosis is considered a triplanar deformity. The purpose of this study is to determine the feasibility of using asymmetry of twisting and ROM in the transverse plane to distinguish AIS patients from healthy controls.

A prospectively obtained cohort of 96 patients with AIS patients between 11 to 21 years of age and 29 age-matched controls underwent whole-body surface scanning (3dMD). Each AIS patient and control subject was asked to rotate clockwise maximally and then counter-clockwise maximally about the long axis of their body while standing upright with their shoulders abducted to 90 degrees and their elbows flexed to 90 degrees. The asymmetry index for twisting (ASItwisting(%)) was computed as well as the total ROM in the transverse plane for each subject.

The ASItwisting(%) resulted in a mean(sdv) of 16.60(8.96) for controls and 23.99(25.59) for AIS patients (p=0.13). The transverse plane ROM(deg) was 92.90(26.92) for controls and 81.54(27.44) for AIS patients (p=0.031).

Transverse plane ROM was significantly reduced in AIS patients compared with controls. ASItwisting(%) was not significantly different between AIS patients and controls most likely a function of the large standard deviation in AIS patients due to the diversity of their curve severities. Interest in both parameters remains from this initial analysis and will be followed by psychometric analyses. AIS patients demonstrated differences in transverse plane movements compared with controls using a 3D topographic measurement that has a fully automated work flow and does not employ ionizing radiation.