title: Anatomic and biomechanical analysis of the short and long head components of the distal biceps tendon.
abstract: OBJECTIVE
  The short head bundle of the distal biceps tendon is more efficient at elbow flexion, and the long head is more efficient at forearm supination.
  
  
  METHODS
  The short and long head bundles of the distal biceps tendon were separated to the bicipital tuberosity in 6 cadavers. The area and centroid of each bundle insertion were computed from surface points measured within each footprint. Each bundle was individually loaded. The supination torque and flexion load generated were recorded at 90° of elbow flexion. The slope of the torque generated versus biceps load was used to define the supination moment arm. The ratio of the flexion load generated to biceps load applied was used to define the relative flexion efficiency.
  
  
  RESULTS
  The short head insertion was positioned distal and anterior relative to the long head and typically included the apex of the tuberosity. The areas of the long and short heads were 59 ± 15 and 94 ± 44 mm(2) (P = .07), respectively. The long head moment arm was significantly higher in supination. The short head had a significantly higher moment arm in neutral and pronation. The ratio of the flexion load to biceps load was 15% higher for the short head.
  
  
  CONCLUSIONS
  The short and long heads of the biceps have distinct insertions. The short head's insertion allows it to be relatively more efficient at elbow flexion at 90°. In the neutral and pronated forearm, the short head is the relatively more efficient supinator. In the supinated forearm, the long head becomes relatively more efficient at supination.
authors.affiliation: Department of Orthopaedics, Division of Upper Extremity Surgery, Allegheny General Hospital, Pittsburgh, PA 15212, USA.
authors.forename: Claudius D
authors.initials: CD
authors.lastname: Jarrett
authors.forename: David M
authors.initials: DM
authors.lastname: Weir
authors.forename: Eric S
authors.initials: ES
authors.lastname: Stuffmann
authors.forename: Sameer
authors.initials: S
authors.lastname: Jain
authors.forename: Mark Carl
authors.initials: MC
authors.lastname: Miller
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Schmidt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001132:Arm; D001696:Biomechanical Phenomena; D002102:Cadaver; D004551:Elbow Joint / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D011403:Pronation / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology; D013484:Supination / Q000502:physiology; D013710:Tendons / Q000033:anatomy & histology* / Q000502:physiology*