Effect of shoulder abduction on the fixation of humeral greater tuberosity fractures: a biomechanical study for three types of fixation constructs

Abstract

Background: An abduction brace and abduction exercises are commonly employed after humeral greater tuberosity fracture repair. However, the effects of glenohumeral abduction on the biomechanical strength have seldom been elucidated.

Method: We studied 24 pairs of female fresh frozen porcine shoulders randomly divided into 3 groups. After creation of a greater tuberosity fracture on each shoulder, 3 fixation techniques were used for the 3 groups: double-row suture anchor fixation (DR), suture bridge technique (SB), and 2-screw fixation (TS). This biomechanical study was conducted to compare the forces that create 3- and 5-mm displacements and the ultimate failure load at the simulated shoulder abduction angles of 0° and 45° among the 3 groups.

Results: In the DR group, the mean forces to create 3- and 5-mm displacements and the failure load at 0° were higher than those at 45° (P = .036, P = .012, P = .027). By contrast, in the SB group, the mean forces to create 3- and 5-mm displacements at 45° were greater than those at 0° (P = .012, P = .012). There were no significant differences in the forces to create 3- and 5-mm displacements and construct failure between 0° and 45° in the TS group (P = .575, .327, .478).

Conclusion: The DR group had greatest initial fixation strength at a low abduction angle, whereas the SB group had the highest initial fixation strength at a high abduction angle. The TS group appeared unaffected by the abduction angle.

Keywords: Humeral greater tuberosity fracture; abduction; biomechanics; screw; surgery; suture anchor.