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American Association for Hand Surgery

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Structural and Biochemical Alterations on Stroke Muscle Contractures
Olga Politikou, MD, Medical University of Vienna, Vienna, Austria, Raji Pichika, PhD, Shirley Ryan AbilityLab, Chicago, IL, Andrea Domenighetti, PhD, Northwestern University, Chicago, IL, Oskar C Aszmann, MD, PhD, CD Laboratory for Restoration of Extremity Function, Division of Plastic and Reocnstructive Surgery, Medical University of Vienna, Vienna, Austria and Richard L. Lieber, PhD, Department of Orthopaedics, Northwestern University, Chicago, IL

Introduction: Stroke is a leading cause of death in America with 610,000 people suffering first or new strokes annually. After stroke, hemiparesis, increased stretch reflex excitability, and even contractures are relatively common. Both the upper motor neuron (UMN) lesion and altered neural input may dramatically affect muscle properties. We previously reported dramatic changes in muscle structural properties after UMN in cerebral palsy (CP) which was accompanied by muscle fibrosis. However, it was not clear in our CP study whether the muscles were "born" with these properties that led to contracture or whether they developed over time. We hypothesized that the UMN in stroke would lead to a similar altered sarcomere structure and collagen content in adult muscle that we observed previously in children.
Materials and methods: During contracture release surgery, we obtained pronator teres (PT) muscle biopsies from female stroke patients (n=3) of mean age ~60 years; all had received at least two doses of botulinum toxin. Control biopsies were obtained from patients undergoing surgery for ulnar nerve decompression (n=2) with mean age ~37 years. Sarcomere length was measured by laser diffraction of tissue fixed in situ. Collagen concentration was measured using the hydroxyproline assay on frozen tissue obtained intraoperatively.
Results: Sarcomere length was significantly longer by over one micron in stroke patients (Fig. 1A). Given that sarcomeres are only a few microns in length, this is a large effect with an effect size (d) over three. Similarly, stroke muscle was clearly fibrotic as total collagen content was dramatically increased in stroke muscle compared to controls (Fig. 1B). Specifically, stroke muscle collagen concentration (~30 µg/mg tissue) was over six times that of control muscle.
Conclusions: Contracture muscle from patients demonstrate dramatic structural alterations as indicated by a dramatic sarcomere length increase and are fibrotic as indicated by a six-fold increase in collagen content. Thus, UMN results in dramatic muscle alterations even in adults. These data have surgical implications since surgical releases and lengthenings will be affected by these altered muscle properties.

(Supported by FESSH Clinical Research Grant and VA Grant IK6 RX003351)


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