title: Torsional Fracture of the Humerus after Subpectoral Biceps Tenodesis with an Interference Screw: A Biomechanical Cadaveric Study.
abstract: BACKGROUND
  Humeral fracture following subpectoral biceps tenodesis has been previously reported; however, there are no published biomechanical studies reporting the resulting torsional strength of the humerus. Our purpose was to determine if there is an increased risk of humerus fracture after subpectoral biceps tenodesis with an interference screw and to determine if screw size is also a factor. We hypothesized that limbs receiving the procedure would have reduced failure torque and rotation under external rotation compared to untreated controls and that the larger screw size would result in inferior mechanical properties compared to the smaller.
  
  
  METHODS
  Twenty matched pairs of embalmed cadaveric humeri were subjected to subpectoral biceps tenodesis using either a 6.25 or 8.0mm interference screw, with the untreated contralateral limb serving as a control. Each humerus was mechanically tested in torsional external rotation to failure.
  
  
  RESULTS
  Maximum torque and rotation to failure were reduced in the tenodesis group compared to controls; however, there was no difference between screw sizes. When both screw sizes were combined into a single group, paired t-tests also showed similar differences.
  
  
  CONCLUSIONS
  Based on our experiment, there is an increased risk for humerus spiral fracture when subjected to torsional external rotation after subpectoral biceps tenodesis with an interference screw compared to an intact humerus; however, there is not a significant difference between a 6.25mm and 8.0mm screw. Surgeons may elect to use alternative fixation methods in patients at high risk (e.g., overhead throwing athletes, etc.) for torsional loads and fracture.
authors.affiliation: American Sports Medicine Institute, Birmingham, AL, USA. Electronic address: DavidB@asmi.org.
authors.forename: David P
authors.initials: DP
authors.lastname: Beason
authors.affiliation: Division of Orthopaedic Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: Jay P
authors.initials: JP
authors.lastname: Shah
authors.affiliation: American Sports Medicine Institute, Birmingham, AL, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Duckett
authors.affiliation: American Sports Medicine Institute, Birmingham, AL, USA.
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Jost
authors.affiliation: American Sports Medicine Institute, Birmingham, AL, USA.
authors.forename: Glenn S
authors.initials: GS
authors.lastname: Fleisig
authors.affiliation: American Sports Medicine Institute, Birmingham, AL, USA.
authors.forename: E Lyle
authors.initials: EL
authors.lastname: Cain
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D006810:Humeral Fractures / Q000209:etiology* / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000601:surgery*; D013710:Tendons / Q000601:surgery; D053656:Tenodesis / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D013718:Tensile Strength; D019415:Torque
keywords: Biceps tenodesis; Biomechanical; Humerus; Interference screw; Spiral fracture; Torsion