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Subscapularis muscle mechanics in children with obstetric brachial plexus palsy

F Einarsson1, T Hultgren, B-O Ljung

  • 1Department of Hand Surgery and Orthopedics, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden. fredrik.einarsson@vgregion.se

The Journal of Hand Surgery, European Volume
|August 9, 2008
PubMed

Insights

Children with obstetrical brachial plexus palsy show altered subscapularis muscle properties. Longstanding lack of stretch causes secondary changes, impacting muscle-to-extracellular matrix communication.

Area of Science:

  • Pediatric Orthopedics
  • Muscle Physiology
  • Biomechanical Engineering

Background:

  • Obstetrical brachial plexus palsy (OBPP) frequently leads to shoulder contractures in children.
  • Understanding the mechanical changes in affected muscles is crucial for effective treatment.

Purpose of the Study:

  • To investigate the passive mechanical properties of the subscapularis muscle in children with OBPP-related contractures.
  • To compare these properties with healthy controls.

Main Methods:

  • Muscle biopsies were obtained from nine children with OBPP undergoing surgery and seven healthy controls.
  • Passive mechanical testing was performed on single muscle fibers and bundles.
  • Key parameters included slack sarcomere length, deformation, and stiffness.

Main Results:

  • Subscapularis muscle fibers from OBPP patients exhibited shorter slack sarcomere length.
  • Fibers showed linear deformation over a wider sarcomere length range.
  • A greater relative increase in stiffness was observed in OBPP patient fibers compared to controls.

Conclusions:

  • Longstanding lack of passive stretch in OBPP leads to secondary muscle fiber property changes.
  • Compensatory alterations in the extracellular matrix are suggested.
  • A dynamic muscle-extracellular matrix communication system is implicated.

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