Electromyographic assessment of muscle fatigue in massive rotator cuff tear

Abstract

Shoulder muscle fatigue has not been assessed in massive rotator cuff tear (MRCT). This study used EMG to measure fatigability of 13 shoulder muscles in 14 healthy controls and 11 patients with MRCT. A hand grip protocol was applied to minimise artifacts due to pain experience during measurement. The fatigue index (median frequency slope) was significantly non-zero (negative) for anterior, middle, and posterior parts of deltoid, supraspinatus and subscapularis muscles in the controls, and for anterior, middle, and posterior parts of deltoid, and pectoralis major in patients (p ≤ 0.001). Fatigue was significantly greater in patients compared to the controls for anterior and middle parts of deltoid and pectoralis major (p ≤ 0.001). A submaximal grip task provided a feasible way to assess shoulder muscle fatigue in MRCT patients, however with some limitations. The results suggest increased activation of deltoid is required to compensate for lost supraspinatus abduction torque. Increased pectoralis major fatigue in patients (adduction torque) likely reflected strategy to stabilise the humeral head against superior subluxing force of the deltoid. Considering physiotherapy as a primary or adjunct intervention for the management of MRCT, the findings of this study generate a base for future clinical studies aiming at the development of evidence-based protocol

Electromyographic Activity of Shoulder Girdle Muscles in Patients With Symptomatic and Asymptomatic Rotator Cuff Tears: A Systematic Review and Meta‐Analysis

“… Methods used: A/D = analog‐to‐digital conversion; Fmax = maximum force; MDF = median frequency. Mean differences: positive values indicate RCT group had greater values than the control or asymptomatic group. Cordasco et al [33]: Positive value means asymptomatic RC group had a greater %MVC compared with the symptomatic %MVC RCT group. Duc et al [25]: Positive value means control group had longer duration of EMG activity relative to movement time; negative value means RC group had longer duration. Hawkes et al [34]: Positive values means RC group had greater average EMG amplitude (normalised to means) compared with controls. Hawkes et al [26]: Positive value means that RC group had greater fatigue, shown as MDF slope (%/min), compared with controls. RCT = rotator cuff tear; MRI = magnetic resonance imaging; US = ultrasound; SSP = supraspinatus; ISP = infraspinatus; SUBS = subscapularis; UT = upper trapezius; LD = latissimus dorsi; PM = pectoralis major; SA = serratus anterior; AD = anterior deltoid; MD = middle deltoid; PD = posterior deltoid; MVIC = maximal voluntary isometric contraction; SD = standard deviation; MVC = maximum voluntary contraction; AR = activation ratio; TM = teres major; DE = deltoid; SIS = subacromial impingement syndrome; GHJ = gleno‐humeral joint; BB = biceps brachii; Br = brachioradialis; RMS = root mean square.…”

“…Hawkes et al [26]: Positive value means that RC group had greater fatigue, shown as MDF slope (%/min), compared with controls.…”

“…Corrected results [24] for the study by de Witte et al [21] were included in this review. Two of the 9 articles were found during the database search update [25,26].…”

“…Four studies [20‐22,33] excluded patients with subscapularis tears. Hawkes et al [26,34] included patients with tears of at least 2 rotator cuff tendons, with 6 patients also having subscapularis tears. Patients included in the study by Kido et al [35] had a full‐thickness tear; however, specific rotator cuff muscles were not stated.…”

Quantification of Stabilization Efforts of Shoulder Muscles using Surface Electromyography

“…The deltoid, biceps and triceps muscles played important roles in stabilizing the shoulder joint during static arm exertions. (Hawkes et al, 2015;Itoi et al, 1993).…”