Nikhil N Dixit1, Carolyn M McCormick2, Eric Warren1, Jacqueline H Cole2, Katherine R Saul3. 1. Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC. 2. Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC; Joint Department of Biomedical Engineering, University of North Carolina Chapel Hill and North Carolina State University, Chapel Hill and Raleigh, NC. 3. Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC. Electronic address: ksaul@ncsu.edu.
Abstract
PURPOSE: Brachial plexus birth injury can differ in presentation, depending on whether the nerve ruptures distal to, or avulses proximal to, the dorsal root ganglion. More substantial contracture and bone deformity at the shoulder is typical in postganglionic injuries. However, changes to the underlying muscle structure that drive these differences in presentation are unclear. METHODS: Seventeen Sprague-Dawley rats received preganglionic or postganglionic neurectomy on a single limb on postnatal days 3 and 4. Muscles crossing the shoulder were retrieved once the rats were sacrificed at 8 weeks after birth. External rotation range of motion, muscle mass, muscle length, muscle sarcomere length, and calculated optimal muscle length were measured bilaterally. RESULTS: Average shoulder range of motion in the postganglionic group was 61.8% and 56.2% more restricted at 4 and 8 weeks, respectively, compared with that in the preganglionic group, but affected muscles after preganglionic injury were altered more severely (compared with the unaffected limb) than after postganglionic injury. Optimal muscle length in preganglionic injury was shorter in the affected limb (compared with the unaffected limb: -18.2% ± 9.2%) and to a greater extent than in postganglionic injury (-5.1% ± 6.2%). Muscle mass in preganglionic injury was lower in the affected limb (relative to the unaffected limb: -57.2% ± 24.1%) and to a greater extent than in postganglionic injury (-28.1% ± 17.7%). CONCLUSIONS: The findings suggest that the presence of contracture does not derive from restricted longitudinal muscle growth alone, but also depends on the extent of muscle mass loss occurring simultaneously after the injury. CLINICAL RELEVANCE: This study expands our understanding of differences in muscle architecture and the role of muscle structure in contracture formation for preganglionic and postganglionic brachial plexus birth injury.
PURPOSE: Brachial plexus birth injury can differ in presentation, depending on whether the nerve ruptures distal to, or avulses proximal to, the dorsal root ganglion. More substantial contracture and bone deformity at the shoulder is typical in postganglionic injuries. However, changes to the underlying muscle structure that drive these differences in presentation are unclear. METHODS: Seventeen Sprague-Dawley rats received preganglionic or postganglionic neurectomy on a single limb on postnatal days 3 and 4. Muscles crossing the shoulder were retrieved once the rats were sacrificed at 8 weeks after birth. External rotation range of motion, muscle mass, muscle length, muscle sarcomere length, and calculated optimal muscle length were measured bilaterally. RESULTS: Average shoulder range of motion in the postganglionic group was 61.8% and 56.2% more restricted at 4 and 8 weeks, respectively, compared with that in the preganglionic group, but affected muscles after preganglionic injury were altered more severely (compared with the unaffected limb) than after postganglionic injury. Optimal muscle length in preganglionic injury was shorter in the affected limb (compared with the unaffected limb: -18.2% ± 9.2%) and to a greater extent than in postganglionic injury (-5.1% ± 6.2%). Muscle mass in preganglionic injury was lower in the affected limb (relative to the unaffected limb: -57.2% ± 24.1%) and to a greater extent than in postganglionic injury (-28.1% ± 17.7%). CONCLUSIONS: The findings suggest that the presence of contracture does not derive from restricted longitudinal muscle growth alone, but also depends on the extent of muscle mass loss occurring simultaneously after the injury. CLINICAL RELEVANCE: This study expands our understanding of differences in muscle architecture and the role of muscle structure in contracture formation for preganglionic and postganglionic brachial plexus birth injury.
Authors: Zhongyu Li; Jianjun Ma; Peter Apel; Cathy S Carlson; Thomas L Smith; L Andrew Koman Journal: J Hand Surg Am Date: 2008-03 Impact factor: 2.230
Authors: Sia Nikolaou; Elizabeth Peterson; Annie Kim; Christopher Wylie; Roger Cornwall Journal: J Bone Joint Surg Am Date: 2011-03-02 Impact factor: 5.284
Authors: Nikhil N Dixit; Daniel C McFarland; Matthew B Fisher; Jacqueline H Cole; Katherine R Saul Journal: J Biomech Date: 2020-01-24 Impact factor: 2.712
Authors: Raveena M Doshi; Monique Y Reid; Nikhil N Dixit; Emily B Fawcett; Jacqueline H Cole; Katherine R Saul Journal: J Orthop Res Date: 2021-09-05 Impact factor: 3.102