Jonathan P Gumucio1,2, Kristoffer B Sugg1,2,3, Elizabeth R Sibilsky Enselman1, Alexis C Konja1, Logan R Eckhardt1, Asheesh Bedi1,4, Christopher L Mendias1,2,4. 1. Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, Michigan, USA. 2. Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA. 3. Department of Surgery, Section of Plastic Surgery, University of Michigan Medical School, Ann Arbor, Michigan, USA. 4. Hospital for Special Surgery, 535 E 70th Street, Research Institute - S.602, New York, NY, 10021, USA.
Abstract
INTRODUCTION: Patients with anterior cruciate ligament (ACL) tears have persistent quadriceps strength deficits that are thought to be due to altered neurophysiological function. Our goal was to determine the changes in muscle fiber contractility independent of the ability of motor neurons to activate fibers. METHODS: We obtained quadriceps biopsies of patients undergoing ACL reconstruction, and additional biopsies 1, 2, and 6 months after surgery. Muscles fiber contractility was assessed in vitro, along with whole muscle strength testing. RESULTS: Compared with controls, patients had a 30% reduction in normalized muscle fiber force at the time of surgery. One month later, the force deficit was 41%, and at 6 months the deficit was 23%. Whole muscle strength testing demonstrated similar trends. DISCUSSION: While neurophysiological dysfunction contributes to whole muscle weakness, there is also a reduction in the force generating capacity of individual muscle cells independent of alpha motor neuron activation. Muscle Nerve, 2018.
INTRODUCTION:Patients with anterior cruciate ligament (ACL) tears have persistent quadriceps strength deficits that are thought to be due to altered neurophysiological function. Our goal was to determine the changes in muscle fiber contractility independent of the ability of motor neurons to activate fibers. METHODS: We obtained quadriceps biopsies of patients undergoing ACL reconstruction, and additional biopsies 1, 2, and 6 months after surgery. Muscles fiber contractility was assessed in vitro, along with whole muscle strength testing. RESULTS: Compared with controls, patients had a 30% reduction in normalized muscle fiber force at the time of surgery. One month later, the force deficit was 41%, and at 6 months the deficit was 23%. Whole muscle strength testing demonstrated similar trends. DISCUSSION: While neurophysiological dysfunction contributes to whole muscle weakness, there is also a reduction in the force generating capacity of individual muscle cells independent of alpha motor neuron activation. Muscle Nerve, 2018.
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