title: Absorbable scaphoid screw development: a comparative study on biomechanics.
abstract: BACKGROUND
  The scaphoid is critical for maintaining the stability and movement of the wrist joints. This study aimed to develop a new internal fixator absorbable scaphoid screw (ASS) for fixation of the scaphoid waist after fracture and to test the biomechanical characteristics of ASS.
  
  
  METHODS
  An ASS was prepared using polylactic acids and designed based on scaphoid measurements and anatomic features. Twenty fractured scaphoid waist specimens were randomly divided into experimental and control groups (n=10/group). Reduction and internal fixation of the scaphoid were achieved with either Kirschner wires (K-wires) or ASS. A moving target simulator was used to test palmar flexion and dorsal extension, with the range of testing (waist movement) set from 5° of palmar flexion to 25° of dorsal extension. Flexion and extension were repeated 2,000 times for each specimen. Fracture gap displacements were measured with a computerized tomography scanning. Scaphoid tensile and bending strengths were measured by using a hydraulic pressure biomechanical system.
  
  
  RESULTS
  Prior to biomechanical fatigue testing, fracture gap displacements were 0.16±0.02 mm and 0.22±0.02 mm in the ASS and K-wire groups, respectively. After fatigue testing, fracture gap displacements in the ASS and the K-wire groups were 0.21±0.03 mm and 1.52±0.07 mm, respectively. The tensile strengths for the ASS and K-wire groups were 0.95±0.02 MPa and 0.63±0.02 MPa, respectively.
  
  
  CONCLUSIONS
  Fixation using an ASS provided sufficient mechanical support for the scaphoid after fracture.
authors.affiliation: Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China.
authors.forename: Muguo
authors.initials: M
authors.lastname: Song
authors.affiliation: Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China.
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China.
authors.forename: YueLiang
authors.initials: Y
authors.lastname: Zhu
keywords: Kirschner wires; absorbable scaphoid screw; biomechanics; internal fixator