title: Relationship between maximum isometric joint moment and functional task performance in patients with brachial plexus injury: A pilot study.
abstract: We evaluated whether subjects with brachial plexus injury (BPI) adapted their movements to reduce the mechanical demand on their impaired upper extremity. In 6 subjects with unilateral BPI with C5 and C6 involvement, we measured bilateral maximum isometric shoulder and elbow strength, and computed joint kinematics and net muscle-generated joint moments during 7 unimanual functional tasks. Compared to the unimpaired extremity, maximum strength in shoulder abduction, extension, and external rotation was 60% (p=0.02), 49% (p=0.02), and 75% (p=0.02) lower, respectively, on the impaired side. Significant kinematic and kinetic differences were observed only when reaching to the back of the head. However, because of substantially reduced strength in their impaired upper extremities, subjects used a significantly higher percentage of their maximum strength during several tasks and along several directions of movement. The peak percentage of maximal strength subjects used across tasks was 32% (p=0.03) and 29% (p=0.03) more on their impaired side in shoulder extension and external rotation, respectively. Subjects had less reserve strength available for performing upper extremity tasks and, therefore, may be less adaptive to strength declines due to injury progression and normal aging. Quantitatively measuring maximal strength may help clinicians ensure that patients maintain sufficient upper extremity strength to preserve long-term functional ability.
authors.affiliation: Department of Biomedical Engineering, North Carolina State University, Raleigh, NC 27695, United States. Electronic address: dlcrouch@ncsu.edu.
authors.forename: Dustin L
authors.initials: DL
authors.lastname: Crouch
authors.affiliation: Virginia Tech-Wake Forest School of Biomedical Engineering and Sciences, Winston-Salem, NC 27157, United States; Department of Biomedical Engineering, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States; Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, United States.
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Santago
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
authors.forename: Johannes F
authors.initials: JF
authors.lastname: Plate
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
authors.forename: Zhongyu
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, United States.
authors.forename: Katherine R
authors.initials: KR
authors.lastname: Saul
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001917:Brachial Plexus / Q000293:injuries*; D004551:Elbow Joint / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D059348:Peripheral Nerve Injuries / Q000503:physiopathology*; D010865:Pilot Projects; D016059:Range of Motion, Articular; D012785:Shoulder Joint / Q000503:physiopathology*; D013647:Task Performance and Analysis
keywords: Kinematics; Nerve; Shoulder; Simulation; Strength