Additional cuff suture provides mechanical advantage for fixation of split-type greater tuberosity fracture of humerus

Abstract

Purpose: Split type of greater tuberosity fracture has variety of surgical treatment options. This study aimed to compare the biomechanics property of additional cuff suture and other fracture fixation techniques.

Methods: Fifteen porcine humeri were categorized into three groups of fixation techniques those were proximal humeral internal locking system (PHILOS) plate with 2 cuff sutures, nonlocking (conventional, 3.5 mm) T-plate with 2 cuff sutures and T-plate with washer that had additional cuff suture (novel technique). Fracture was created by greater tuberosity osteotomy with 50˚ inclination to the line of surgical neck and then fixed with different prescribed techniques. Displacement of fracture site was measured with universal testing machine. The maximum forces to produce 3 mm, 5 mm of displacement and load to failure were recorded.

Results: The average loads to reach 3 mm, 5 mm displacement and failure were 30.8 N, 45.4 N and 161 N for nonlocking T-plate; 76.6 N, 99.2 N and 144 N for PHILOS plate; 95.8 N, 120 N and 197 N for novel technique. The differences among three groups were significant in load to displacement at 3 and 5 mm (but not significant in load to failure). For load to reach 3- and 5-mm displacement, PHILOS plate and novel technique were significantly stronger than nonlocking T-plate (P < 0.05). For load to reach 3 and 5 mm displacement, novel technique was stronger than PHILOS plate but not significant (P > 0.05). For load to failure, novel technique was stronger than nonlocking plate and PHILOS plate but not significant (P < 0.05).

Conclusion: The important factors affecting the strength of fracture fixation are type of plate and numbers of suture augmentation that tie to the plate. Fixation with additional cuff suture showed the superior biomechanics of load to reach 3 mm, 5 mm displacement with better load to failure compared with PHILOS plate and conventional T-plate alone.

Keywords: Fixation; Greater tuberosity fracture; Split-type; T-plate.