title: Factors affecting supination strength after a distal biceps rupture.
abstract: OBJECTIVE
  This study quantified pain (visual analog pain scale [VAPS]), disability (Disabilities of the Arm, Shoulder and Hand [DASH]) and isometric supination torque at 3 forearm positions in a prospective cohort of biceps-deficient arms to assess the potential for functional return with nonoperative treatment.
  
  
  METHODS
  Twenty-three men (50 ± 11 years) with complete unilateral distal biceps avulsion underwent isometric supination strength testing of both limbs at 60° of supination, 0° (neutral), and 60° of pronation. After exclusion of 1 outlier patient, the mean time from injury to evaluation was 44 days (range, 4-455 days). Pain level (VAPS) and functional outcome (DASH) were assessed; supination strength was normalized to the uninjured arm.
  
  
  RESULTS
  The uninjured arm was stronger (P < .001), and peak torque varied with forearm position (P < .043). Peak torque was greater in pronation compared with supination, regardless of injury (P < .002). No differences were detected in supination strength as a result of forearm position or arm dominance. Supination strength did not correlate with time from injury to evaluation. One patient regained supination strength (115%) at 60° of pronation and 72% in neutral with a lengthy time from injury. VAPS (5 of 10) and DASH (39 of 100) scores decreased with time and did not relate to supination strength.
  
  
  CONCLUSIONS
  Biceps tendon rupture led to a 60% decrease in supination strength in the neutrally oriented forearm. Peak torque observations can be explained using forearm moment arms. VAPS and DASH scores decreased with time but did not affect strength. We speculate that supination strength from pronation to neutral can improve as one strengthens the brachioradialis but strength deficits from neutral to supination are more difficult to overcome.
authors: Orthopaedic Specialists- UPMC, Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA. Electronic address: cschmidthand@comcast.net.
authors: Christopher C
authors: CC
authors: Schmidt
authors: Department of Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors: Brandon T
authors: BT
authors: Brown
authors: Department of Orthopaedic Surgery and Sports Medicine, Essentia Health, Fargo, ND, USA.
authors: Prasad J
authors: PJ
authors: Sawardeker
authors: North Louisiana Orthopaedic and Sports Medicine Clinic, Monroe, LA, USA.
authors: Martin
authors: M
authors: DeGravelle
authors: Department of Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors: Mark Carl
authors: MC
authors: Miller
mesh_terms: D000328:Adult; D000368:Aged; D005543:Forearm Injuries / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000293:injuries / Q000503:physiopathology; D011403:Pronation; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D020127:Recovery of Function; D012421:Rupture; D013484:Supination; D013708:Tendon Injuries / Q000503:physiopathology*; D019415:Torque; D016896:Treatment Outcome
keywords: DASH; Level II; Prognostic Study; Ruptured biceps tendon; VAPS; conservative treatment; isometric; prospective follow-up; supination strength