Electromyographic and nerve block analysis of the subscapularis liftoff test.
The inability to perform the "liftoff" test has been attributed to a subscapularis muscle or tendon injury. The goals of this study were to evaluate the activity of the glenohumeral muscles during performance of the "liftoff" maneuver and to identify the most effective initial upper extremity placement that isolates the subscapularis musculotendinous unit. In the first phase of this study 15 subjects accomplished four proposed versions to the "liftoff" test while their intramuscular electromyographic activity in select glenohumeral muscles was recorded. The second phase of this study assessed the ability of five subjects with a nonfunctional subscapularis musculotendinous unit to perform the same proposed versions. On the basis of electromyographic data none of the proposed versions to the "liftoff" maneuver isolated the upper and lower subscapularis muscle from either the teres major, latissimus dorsi, posterior deltoid, or rhomboid muscles (p > 0.05). In the presence of a nonfunctional subscapularis musculotendinous unit, the subjects were able to perform all of the proposed versions of the "liftoff" maneuver except one: elevation of the dorsum of the hand from the posterior-inferior border of the scapula (maximum internal rotation test). Although significant electromyographic activity was generated in the potentially confounding shoulder girdle muscles during the maximum internal rotation "liftoff" test, a successful test appears to be dependent on the isolated glenohumeral internal rotation function of the subscapularis muscle.
Stefko
J M
JM
Centinela Hospital Medical Center, Biomechanics Laboratory, Inglewood, CA 90301, USA.
Jobe
F W
FW
VanderWilde
R S
RS
Carden
E
E
Pink
M
M
D000328:Adult; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000293:injuries* / Q000294:innervation; D009407:Nerve Block; D010808:Physical Examination / Q000379:methods* / Q000592:standards; D011187:Posture; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012399:Rotation; D012783:Shoulder Dislocation / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D013708:Tendon Injuries; D013710:Tendons / Q000294:innervation