title: Prospective blinded comparison of surface versus wire electromyographic analysis of muscle recruitment in shoulder instability.
abstract: BACKGROUND
  This pilot study assesses level of agreement between surface and fine-wire electromyography (EMG), in order to establish if surface is as reliable as fine wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder.
  
  
  METHODS
  Eighteen participants (11 female) with unstable shoulders were recruited after written consent and ethical approval. Anthropometric information and mean skinfold size for triceps, subscapular, biceps and suprailiac sites were obtained. Triple-stud self-adhesive surface electrodes ('Triode'; Thermo Scientific, Physio Med Services, Glossop, Derbyshire, England) were placed over pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS) at standardized locations. Participants performed five identical uniplanar standard movements (flexion, abduction, external rotation, extension and cross-body adduction). After a 20-minute rest period, a dual-needle technique for fine-wire insertion was performed and the standard movements were repeated. An experienced examiner in each technique reported if muscle activation patterns differed from agreed normal during any movement and were blinded to the other test results. Sensitivity, specificity and Kappa values for level of agreement between methods were calculated for each muscle according to the method of Altman (1991).
  
  
  RESULTS
  Fifteen participants were successfully tested. Sensitivity, specificity and Kappa values between techniques for each muscle were PM (57%, 50%, 0.07), LD (38%, 85%, 0.22), AD (0%, 76%, -0.19) and IS (85%, 75%, 0.6). Only IS demonstrated high sensitivity and specificity and a moderate level of agreement between the two techniques. There was no correlation between skinfold size and agreement levels.
  
  
  CONCLUSIONS
  The use of surface EMG may help to classify types of shoulder instability and recognize abnormal muscle patterns. It may allow physiotherapists to direct specific rehabilitation strategies, avoiding strengthening of inappropriate muscles. It has a reasonable degree of confidence to evaluate IS but may have poor sensitivity in detecting abnormal patterns in PM, LD and AD. Further work is required to see if investigator interpretation may have been a factor for the poor level of agreement.
authors.affiliation: Royal National Orthopaedic Hospital, UK. anjujaggi@hotmail.com
authors.forename: Anju
authors.initials: A
authors.lastname: Jaggi
authors.forename: Alex A
authors.initials: AA
authors.lastname: Malone
authors.forename: Joseph
authors.initials: J
authors.lastname: Cowan
authors.forename: Simon
authors.initials: S
authors.lastname: Lambert
authors.forename: Ian
authors.initials: I
authors.lastname: Bayley
authors.forename: Mindy C
authors.initials: MC
authors.lastname: Cairns
mesh_terms: D000293:Adolescent; D000328:Adult; D004566:Electrodes; D004576:Electromyography / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000534:rehabilitation; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D026741:Physical Therapy Modalities; D010865:Pilot Projects; D012680:Sensitivity and Specificity; D012785:Shoulder Joint; D016037:Single-Blind Method