title: The Importance of Preserving the Radial Tuberosity During Distal Biceps Repair.
abstract: BACKGROUND
  The radial tuberosity contributes to the biceps supination moment arm and the elbow flexion moment. The purpose of our study was to compare the impact of a cortical bone trough versus an anatomic repair on measurements of the forearm supination moment arm and elbow flexion force efficiency. Our hypothesis was that a trough repair would decrease the tuberosity height, the native biceps supination moment arm, and elbow flexion force efficiency compared with an anatomic repair.
  
  
  METHODS
  The isometric supination moment arm and elbow flexion force efficiency were measured in ten matched pairs of cadaveric upper limbs. After testing, the geometry of the proximal aspect of the radius was reconstructed with use of stereophotogrammetry. All of the repair sites were three-dimensionally reconstructed to quantify the disturbance of the trough on native anatomy. The tuberosity distance was defined as the distance between the central axis of the radius and the centroid of the respective repair site.
  
  
  RESULTS
  Specimens with a trough repair had a 27% lower supination moment arm at 60° of supination (p = 0.036). There were no differences found for pronation or neutral forearm positioning (p > 0.235). Flexion force efficiency was not significantly different between the trough and anatomic repair groups. The average tuberosity distance was 11.0 ± 2.1 mm for the anatomic repairs and 8.3 ± 1.4 mm for the trough repairs (p = 0.003). The percentage of distance lost due to the trough was 25%. Furthermore, the supination moment arm in the supinated position was significantly correlated with the tuberosity distance.
  
  
  CONCLUSIONS
  The trough technique resulted in a significant decrease (p = 0.036) in the moment arm of a 60° supinated forearm and a significant reduction (p = 0.003) in radial tuberosity height. The loss of the supination moment arm was correlated with the decrease in tuberosity height, providing evidence that the radial protuberance acts as a mechanical cam.
  
  
  CONCLUSIONS
  The anterior protuberance of the radial tuberosity functions as a supination cam; therefore, consideration should be given to preserve its topographical anatomy during a distal biceps repair.
authors.affiliation: Orthopaedic Specialists-UPMC, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 9104 Babcock Boulevard, Suite 5113, Pittsburgh, PA 15237. E-mail address: schmidtc@upmc.edu.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Schmidt
authors.affiliation: Department of Mechanical Engineering, University of Pittsburgh, 609 Benedum Hall, 3700 O'Hara Street, Pittsburgh, PA 15213.
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Brown
authors.affiliation: Comprehensive Orthopedic Specialists, 82 South 1100 East, Suite 303, Salt Lake City, Utah 84102.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Williams
authors.affiliation: Premier Orthopaedics, 2400 Patterson Street, Suite 300, Nashville, TN 37203.
authors.forename: James H
authors.initials: JH
authors.lastname: Rubright
authors.affiliation: Department of Mechanical Engineering, University of Pittsburgh, 609 Benedum Hall, 3700 O'Hara Street, Pittsburgh, PA 15213.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Schmidt
authors.affiliation: Department of Mechanical Engineering, University of Pittsburgh, 609 Benedum Hall, 3700 O'Hara Street, Pittsburgh, PA 15213.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Pic
authors.affiliation: Brielle Orthopedics, 457 Jack Martin Boulevard, Brick, NJ 08724.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Nakashian
authors.affiliation: Department of Mechanical Engineering, University of Pittsburgh, 609 Benedum Hall, 3700 O'Hara Street, Pittsburgh, PA 15213.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Schimoler
authors.affiliation: Biomechanics Laboratory, Allegheny General Hospital, 10th Floor South Tower, 320 East North Avenue, Pittsburgh, PA 15212.
authors.forename: Mark Carl
authors.initials: MC
authors.lastname: Miller
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D004551:Elbow Joint / Q000502:physiology*; D005260:Female; D005543:Forearm Injuries / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D011403:Pronation; D011884:Radius / Q000033:anatomy & histology / Q000601:surgery*; D016059:Range of Motion, Articular; D013484:Supination; D013708:Tendon Injuries / Q000601:surgery*