title: Validity of serum creatine kinase as a measure of muscle injury produced by lumbar surgery.
abstract: OBJECTIVE
  Serum creatine kinase (CK) concentrations have historically been used to investigate muscle disease and serious muscle damage, and there is a growing interest in the potential for a biochemical approach to quantifying skeletal muscle injury occurring in orthopedic surgeries and spinal injuries. The wide availability of CK measurement could foster spinal muscle injury research. However, measurement validity has never been systematically demonstrated in clinical settings. In this study, the validity of serum CK concentration elevation as an index of muscle injury was investigated using lumbar decompression surgery (LDS) as a model.
  
  
  METHODS
  Blood samples were obtained from 18 research volunteers drawn from the clinical population undergoing LDS. A baseline sample was taken in the preoperative waiting area. Each subject's highest CK concentration between 12 and 48 hours after surgery was used as the biochemical injury response. The surface area of muscle isolated (incision lengthxdepth) and strained by retraction was obtained for concurrent validity testing against biochemical measurement.
  
  
  RESULTS
  The correlation between highest total CK concentration and muscle surface area was moderate (r=0.60) and significant (P<0.01). Correlations between surface area and CK at specific time points, revealed minimal loss of association at 12 hours (r=0.57) and 24 hours (r=0.58), but weaker correlations at 6 hours (r=0.45) and 48 hours (r=0.28) after injury. Analyses for proportions of each isoenzyme making up the total CK revealed that baseline and peak CK consisted almost exclusively of skeletal muscle CK (CK-MM), with minimal representation by heart muscle (CK-MB), and brain (CK-BB).
  
  
  CONCLUSIONS
  The findings provide support for the validity of serum CK measurement as an index of skeletal muscle injury caused by LDS, and demonstrate that LDS provides a useful model for measurement testing and development studies.
authors.affiliation: McMaster Medical Rehabilitation, Department of Medicine, McMaster University, Ontario, Canada. kumbhad@mcmaster.ca
authors.forename: Dinesh
authors.initials: D
authors.lastname: Kumbhare
authors.forename: William
authors.initials: W
authors.lastname: Parkinson
authors.forename: Brett
authors.initials: B
authors.lastname: Dunlop
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D003402:Creatine Kinase / Q000032:analysis / Q000097:blood*; D019299:Decompression, Surgical / Q000009:adverse effects; D017586:Diskectomy / Q000009:adverse effects; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000601:surgery; D007796:Laminectomy / Q000009:adverse effects*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000201:enzymology / Q000293:injuries* / Q000503:physiopathology; D009135:Muscular Diseases / Q000097:blood / Q000175:diagnosis / Q000201:enzymology; D011183:Postoperative Complications / Q000097:blood* / Q000175:diagnosis* / Q000201:enzymology; D011237:Predictive Value of Tests; D012206:Rhabdomyolysis / Q000097:blood / Q000175:diagnosis / Q000201:enzymology
chemical_list: D015415:Biomarkers; D003402:Creatine Kinase