PAIN INHIBITION OF SHOULDER STRENGTH IN PATIENTS WITH IMPINGEMENT SYNDROME

Fourteen patients with Stage II or III impingement syndrome (average a ge 58 years) were studied. Nine patients had full-thickness rotator cu ff tears documented by arthrograms. Patients initially underwent a tho rough shoulder examination followed by baseline isokinetic strength te sting. Abduction/adduction testing was performed utilizing a Biodex dy namometer. Maximum concentric contractions were performed, and values for peak torque (FT), total work (W), and power (P) were obtained. All patients received a subacromial injection of 5 cc 1% lidocaine plus 5 cc 0.5% bupivacaine (Marcaine). After 5 minutes the testing sequence was repeated. Clinically, patients demonstrated marked improvement fol lowing injection. Eighty-six percent reported complete pain relief; th e remaining two patients reported only mild discomfort at the extremes of motion. Improvement in functional activity of the affected shoulde r was noted by all subjects. On manual muscle testing, 13 of 14 patien ts (93%) demonstrated increased abduction strength; 11 of 14 (79%) had improvement in external rotation. Mean increases in active forward el evation and external rotation were 36-degrees and 11-degrees, respecti vely (P < .01). Postinjection isokinetic changes in PT, W, and P for a bduction/adduction were dramatic. For abduction, all patients showed s ignificant increases in P (mean 82%), W (mean 90%), and PT (mean 48%) (all P < .05). No significant differences in range of motion testing o r strength parameters were noted based on the presence or absence of a rotator cuff tear. For abduction, all patients showed significant inc reases in P (mean 208%), W (mean 183%), and PT (mean 41%) (all P < .05 ). Our findings indicate that pain is an important factor in the etiol ogy of shoulder weakness documented by both clinical examination and i sokinetic testing. Isokinetic muscle testing provides a method of quan titating the effect of pain on muscle function as measured by PT, W, a nd P. This information may be important in assessing the improvement i n strength following acromioplasty with or without rotator cuff repair .