Effects of bone fracture and surgery on plasma myosin heavy chain fragments of skeletal muscle

Objective: Myosin heavy chain (MHC) fragment is part of a structural or for ce-bearing protein expressed in the thick filament of muscle fibres. Since MHC fragment is a contractile protein, an increase in plasma MHC concentrat ions after muscle injury indicates degradation of the contractile apparatus . This study was conducted to determine whether MHC concentrations could be a tool in the assessment of tissue damage in patients with myoskeletal inj uries. Design: Prospective, controlled study. Setting: A UK University National Health Service Centre. Patients: Thirty-eight orthopedic patients, of whom 14 received surgical tr eatments within the 2-day study period. Patients were compared with 16 nono rthopedic control subjects. Outcome measures: Serum levels of MHC, creatine kinase, cardiac troponin I (cTnI), and myoglobin were measured at the time of admission and 24 hours l ater. Data from patients undergoing surgical repairs were obtained 24 hours after surgery. A competitive radio-immunoassay for beta-type MHC was used. Results: Plasma MHC concentration was higher in the patients than in the co ntrols. The peak levels were observed 24 hours after injury or surgery (p < 0.05). cTnI concentrations were consistently below the assay detection lim it of 0.3 mu g/L, thus excluding protein release from the heart muscle (car diac beta-type MHC). Creatine kinase and myoglobin concentrations were sign ificantly higher on admission in the non-surgical patients than in the surg ically treated cases. Conclusions: Serum MHC levels could be a useful supplementary retrospective , prognostic or diagnostic tool in the study of myoskeletal disturbances in volving muscle injury or bone fractures that result in membrane leakage of myoskeletal cells.