Shoulder muscle activation and coordination in patients with a massive rotator cuff tear: An electromyographic study

Abstract

Adaptive muscle activation strategies following a massive rotator cuff tear (MRCT) are inadequately understood, and the relationship among muscles during everyday activities has not been considered. Thirteen healthy subjects comprised the control group, and 11 subjects with a MRCT the patient group. Upper limb function was assessed using the Functional Impairment test-hand, neck, shoulder, and arm (FIT-HaNSA). Electromyography (EMG) was recorded from 13 shoulder muscles, comprising five muscle groups, during a shelf-lifting task. Mean FIT-HaNSA scores were significantly lower in MRCT patients (p 0.001), reflecting a severe functional deficit. In MRCT patients, EMG signal amplitude was significantly higher for the biceps brachii-brachioradialis (p < 0.001), upper trapezius-serratus anterior (p ¼ 0.025), muscle groups and for the latissimus dorsi (p ¼ 0.010), and teres major (p ¼ 0.007) muscles. No significant differences in the correlation among muscle groups were identified, pointing to an unchanged neuromuscular strategy following a tear. In MRCT patients, a reorganization of muscle activation strategy along the upper limb kinetic chain is aimed at reducing demand on the glenohumeral joint. Increased activation of the latissimus dorsi and teres major muscles is an attempt to compensate for the deficient rotator cuff. Re-education towards an alternate neuromuscular control strategy appears necessary to restore function.

Electromyographic assessment of muscle fatigue in massive rotator cuff tear

“…Despite the compensatory role previously advocated for LD and TM [Hawkes et al, 2011;Steenbrink et al, 2006], they showed no significant fatigue progression in this study.…”

“…According to the concept of 'adductor muscle co-contraction' during arm elevation [Steenbrink et al, 2006;Steenbrink et al, 2009], contraction of muscles with a line of pull that opposes the superior subluxing force of deltoid can balance the destabilising forces and result in a stable GHJ fulcrum. EMG and computer simulation programmes have identified compensatory roles for LD, TM and PM [Hawkes et al, 2011;Steenbrink et al, 2006;Steenbrink et al, 2009]. Referring to these muscles as 'adductors', can obscure appreciation of their essential role in supporting stability during other shoulder movements.…”

“…Study groups were the same as those reported in an earlier study of muscle activation and coordination in MRCT [Hawkes et al, 2011].…”

Importance of the subscapularis muscle after total shoulder arthroplasty

“…Ideally EMG data from deficient SC subjects would be desirable, however, as a first approximation, and since only a 50% SC deficiency was simulated, we assumed that healthy EMG data could be used. This approximation was supported by an EMG study comparing healthy subjects to rotator cuff tear patients and reporting no significant differences in inter-muscular coordination (Hawkes et al, 2012). We associated muscular deficiency with PCSA, as suggested by clinical observations (De Wilde et al, 2012;Goutallier et al, 1994).…”

Rotary Hood Massive Break Solutions? Massive Rotator Cuff Tear Solutions?

“…The ruptures of the hood are the most common musculotendinous ruptures [4], and the prevalence of massive ruptures ranges from 10% to 40% and increases with age [2,[5][6][7]. The first studies to use the term "solid rupture" date from the decades of 70, 80 [1].…”