title: Combined effect of change in humeral neck-shaft angle and retroversion on shoulder range of motion in reverse total shoulder arthroplasty - A simulation study.
abstract: BACKGROUND
  We studied combined effect of change in humeral neck shaft angle and retroversion on shoulder ROM in reverse total shoulder arthroplasty using 3-dimensional simulations.
  
  
  METHODS
  Using a 3D model construct based on the CT scans of 3 males and a 3-dimensional analysis program, a humeral component of reverse total shoulder arthroplasty was implanted in 0°, 10°, 20°, 30°,40° retroversion and 135°, 145°, and 155° neck shaft angle. Total horizontal range of motion (sum of horizontal adduction and abduction) at 30° and 60° scaption, adduction in the scapular plane and IR behind the back were measured for various combinations of neck shaft angle and retroversion.
  
  
  RESULTS
  Change in retroversion didn't show any effect on total horizontal range of motion. Total horizontal range of motion at both 30° and 60° scaption, showed maximum values at 135° neck shaft angle and minimum values at 155° neck shaft angle. With any combination of retroversion angles, adduction deficit was maximum at 155° neck shaft angle and no adduction deficit at 135° neck shaft angle. Every 10° decrease in neck shaft angle resulted in an average 10.4° increase in adduction. For every 10° increase in retroversion, there was loss of internal rotation behind the back up to at least one vertebral level.
  
  
  CONCLUSIONS
  135° neck shaft angle resulted in maximum total horizontal range of motion both at 30° and 60° scaption regardless of retroversion angles. 135° neck shaft angle also reduced the chances of scapular impingement. Decrease in retroversion angle resulted in more amount of internal rotation behind the back.
authors.affiliation: Department of Mechatronics Engineering, College of Engineering, Chungnam National University, Deajeon, South Korea.
authors.forename: Byung-Kwan
authors.initials: BK
authors.lastname: Jeon
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Catholic University, Daejeon St. Mary's Hospital, Deajeon, South Korea.
authors.forename: Karnav A
authors.initials: KA
authors.lastname: Panchal
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Catholic University, Daejeon St. Mary's Hospital, Deajeon, South Korea. Electronic address: jijh87@gmail.com.
authors.forename: Jong-Hun
authors.initials: JH
authors.lastname: Ji
authors.affiliation: Department of Mechatronics Engineering, College of Engineering, Chungnam National University, Deajeon, South Korea.
authors.forename: Yuan-Zhu
authors.initials: YZ
authors.lastname: Xin
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Catholic University, Daejeon St. Mary's Hospital, Deajeon, South Korea.
authors.forename: Sung-Ryeoll
authors.initials: SR
authors.lastname: Park
authors.affiliation: Department of Mechatronics Engineering, College of Engineering, Chungnam National University, Deajeon, South Korea.
authors.forename: Joong-Hui
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Mechatronics Engineering, College of Engineering, Chungnam National University, Deajeon, South Korea. Electronic address: sjyang@cnu.ac.kr.
authors.forename: Seok-Jo
authors.initials: SJ
authors.lastname: Yang
mesh_terms: D000328:Adult; D019643:Arthroplasty, Replacement / Q000379:methods*; D001696:Biomechanical Phenomena; D006801:Humans; D006811:Humerus / Q000503:physiopathology / Q000601:surgery*; D021621:Imaging, Three-Dimensional; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology*; D012540:Scapula / Q000503:physiopathology / Q000601:surgery*; D019534:Shoulder Impingement Syndrome / Q000517:prevention & control; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: 3D simulation; Humeral retroversion; Neck-shaft angle; Reverse total shoulder arthroplasty; Shoulder range of motion