Subpectoral Biceps Tenodesis With PEEK Interference Screw: A Biomechanical Analysis of Humeral Fracture Risk

Abstract

Purpose: To quantify the torsional load to fracture for subpectoral biceps tenodesis with interference screw fixation.

Methods: We randomized 28 specimens from 14 matched-pair full-length humeri (mean age, 55.3 years) into 3 groups: (1) empty ream group (ERG), (2) screw-only group (SOG), and (3) screw-plus-biceps tendon group (SBG). In each group, 1 humerus of each matched pair was prepared according to group allocation and the contralateral humerus remained intact as a control. In the ERG, an 8-mm unicortical hole was reamed 1 cm proximal to the inferior border of the pectoralis major tendon insertion; in the SOG, the humerus was filled with an 8-mm × 12-mm PEEK (polyether ether ketone) screw; and in the SBG, the humerus was filled with a PEEK screw and the cadaveric long head of the biceps tendon. Humeri were tested under torsional displacement at a rate of 1°/s until fracture. Maximum torque, energy to maximum torque, and linear stiffness were used to assess humerus strength.

Results: Compared with contralateral intact specimens, the maximum torque to fracture was reduced by 28% in the ERG (P = .005), 30% in the SOG (P = .014), and 20% in the SBG (P = .046). Energy to maximum torque was similarly reduced in the ERG (P = .007), SOG (P = .023), and SBG (P = .049). Stiffness was increased by 4% in the ERG (P = .498), 9% in the SOG (P = .030), and 4% in the SBG (P = .439).

Conclusions: Drilling an 8-mm unicortical hole in zone 3 of the bicipital tunnel for open subpectoral biceps tenodesis reduces the torsional load to humeral fracture up to 28% at time 0. The addition of a PEEK tenodesis screw alone reduced the maximum torque by 30%, and the addition of a screw with the long head of the biceps tendon reduced the maximum torque by 20%. The total load to fracture was reduced in all settings. Stiffness was not significantly different for the ERG and SBG, but stiffness was significantly higher for the SOG compared with the intact matched humeri at time 0.

Clinical relevance: When performing a biceps tenodesis, humeral fracture susceptibility is increased with an applied torsional load at time 0. Thus providers must be aware of this reduced integrity when a subpectoral biceps tenodesis is used.