title: Biomechanical characterization of unicortical button fixation: a novel technique for proximal subpectoral biceps tenodesis.
abstract: OBJECTIVE
  Proximal biceps tenodesis is one method for treating biceps-related pain. Tenodesis protects the length-tension relationship of the biceps muscle, maintains strength, and provides a better cosmetic appearance than tenotomy. The purpose of this investigation was to compare the mechanical properties of a unicortical metal button and an interference screw in proximal biceps tenodesis.
  
  
  METHODS
  Six pairs of fresh-frozen shoulders were dissected, leaving the proximal biceps tendon as a free graft. On each pair of shoulders, a biceps tenodesis was performed using an interference screw or a unicortical metal button. The specimens were mounted and a cyclic load (10-60 N) was applied at 1 Hz for 200 cycles, followed by an axial load to failure. The displacement, ultimate load to failure, and mode of failure were recorded.
  
  
  RESULTS
  Displacement in response to cyclic loading was 3.7 ± 2.2 mm for the interference screw and 1.9 ± 1.0 mm for the cortical button (P = 0.03). Load at failure for the interference screw was 191 ± 64 N (stiffness: 24 ± 11 N/mm) and 183 ± 61 N (stiffness: 24 ± 7. N/mm) for the unicortical button (P = n.s. for both cases).
  
  
  CONCLUSIONS
  As a novel technique for subpectoral biceps tenodesis, a unicortical button demonstrated significantly less displacement in response to cyclic loading than the interference screw. The ultimate load to failure and stiffness for the two methods were not different. In this way, a unicortical button may provide a reliable alternative method of fixation with a potentially lower risk of post-operative humeral fracture and a construct that permits early mobilization following biceps tenodesis.
authors.affiliation: Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Stoneman 10, Boston, MA, USA. jpdeangelis@yahoo.com.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: DeAngelis
authors.affiliation: Department of Orthopaedic Surgery, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.|Harvard Medical School, Boston, MA, USA.
authors.forename: Alvin
authors.initials: A
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.|Department of Biomedical Engineering, Boston University, Boston, MA, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Wexler
authors.affiliation: Department of Orthopaedic Surgery, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.|Department of Biomedical Engineering, Boston University, Boston, MA, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hertz
authors.affiliation: Department of Orthopaedic Surgery, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Leandro
authors.initials: L
authors.lastname: Grimaldi Bournissaint
authors.affiliation: Department of Orthopaedic Surgery, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Ara
authors.initials: A
authors.lastname: Nazarian
authors.affiliation: Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Stoneman 10, Boston, MA, USA.
authors.forename: Arun J
authors.initials: AJ
authors.lastname: Ramappa
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002062:Bursitis / Q000503:physiopathology / Q000601:surgery*; D002102:Cadaver; D006801:Humans; D018482:Muscle, Skeletal / Q000503:physiopathology / Q000601:surgery*; D019651:Plastic Surgery Procedures / Q000295:instrumentation*; D053441:Suture Anchors; D013710:Tendons / Q000503:physiopathology / Q000601:surgery*; D053656:Tenodesis / Q000379:methods*; D058971:Tenotomy / Q000379:methods