Ishijima T1, Muraki T2, Sekiguchi Y2, Ishikawa H2, Ishijima Y3, Morise S4, Yashima Y1, Sato K1, Izumi S-I5
1IMS Meirikai Sendai General Hospital, Rehabilitation, Sendai, Japan, 2Tohoku University Hospital, Rehabilitation, Sendai, Japan, 3Nishi-sendai Hospital, Rehabilitation, Sendai, Japan, 4Sendai Medical Center, Rehabilitation, Sendai, Japan, 5Tohoku University Graduate School of Medicine, Department of Physical Medicine and Rehabilitation, Sendai, Japan
Background: Sufficient upper rotation movement of the scapula is considered essential for the elevation of the glenohumeral joint, and torque in the scapular movement is achieved by the scapular force couple. Therefore, disequilibrium in the activation of the muscle group responsible for the force couple has been reported to limit the angle of the upper rotation of the scapula in lifting the arm and an insufficient angle can be a factor that triggers subacromial impingement. This condition is a characteristic symptom in patients with painful partial-thickness rotator cuff tears (PTRCT), and is known to be the primary cause of pain on movement. However, the problems with upper rotation scapular muscle activation in patients with painful PTRCT are unknown, and there is a lack of specific findings that can serve as indicators for treatment.
Purpose: This study aimed to elucidate the upper rotation scapular muscle-activation ratio in patients with PTRCT.
Methods: The subjects were 20 adult women [8 rotator cuff tear patients (67±10.4 years old) and 12 healthy persons (68±11.7 years old)]. The details of research were fully explained to the candidate and consent was obtained. Muscle activities were measured in upper trapezius, lower trapezius, and in serratus anterior muscle by the surface electromyogram. The activation of the muscles was divided into three groups, [a] upper and lower trapezius (UT/LT), [b] UT/serratus anterior (SA), and [c] LT/SA. In addition, individual target muscle activities were compared. Measurement positions were on scapular plane with upper limb elevation angles of 30°, 60°, 90° and 120°. The examiner guided the upper limbs to the measurement position, and held them for 5 seconds. We took 30 seconds of break totally 3 times each time after the implementation. Analysis period of EMG data for each muscle was 3 seconds, which was the mean of measured 5 seconds. We normalized the analyzed value at each measurement degree（30°, 60°, 90°, and 120°）with upper limb elevation by analyzed value at upper limb elevation 15°. Two-way ANOVA was conducted on EMG data obtained by comparing PTRCT patients with healthy individuals, and multiple comparisons by Tukey-Kramer test was conducted as the post facto official approval.
Results: We found a significant difference in the scapular muscle-activation ratio in upper rotation in the LT/SA ratio at 120° (p 0.05).Comparison between the individual muscle groups showed that activity of the LT increased as the measured angle widened, and the difference was significant at 120°(p 0.01) .
Conclusion(s): Our results suggest that changes in the upper rotation scapular muscle activation in patients with painful PTRCT occur as compensation for reduced articular torque in the glenohumeral joint.
Implications: When elevating the upper limb, the upper rotation muscle-activation ratio tends to change with the increase in the upper limb angle. Furthermore, a comparison of individual muscle activity showed increased activation of the LT with upper limb elevation.
Keywords: Painful partial-thickness rotator cuff tears, Upper rotation scapular muscle, Activation ratio
Funding acknowledgements: Department of Physical Medicine and Rehabilitation, Tohoku University Graduate School of Medicine
Purpose: This study aimed to elucidate the upper rotation scapular muscle-activation ratio in patients with PTRCT.
Methods: The subjects were 20 adult women [8 rotator cuff tear patients (67±10.4 years old) and 12 healthy persons (68±11.7 years old)]. The details of research were fully explained to the candidate and consent was obtained. Muscle activities were measured in upper trapezius, lower trapezius, and in serratus anterior muscle by the surface electromyogram. The activation of the muscles was divided into three groups, [a] upper and lower trapezius (UT/LT), [b] UT/serratus anterior (SA), and [c] LT/SA. In addition, individual target muscle activities were compared. Measurement positions were on scapular plane with upper limb elevation angles of 30°, 60°, 90° and 120°. The examiner guided the upper limbs to the measurement position, and held them for 5 seconds. We took 30 seconds of break totally 3 times each time after the implementation. Analysis period of EMG data for each muscle was 3 seconds, which was the mean of measured 5 seconds. We normalized the analyzed value at each measurement degree（30°, 60°, 90°, and 120°）with upper limb elevation by analyzed value at upper limb elevation 15°. Two-way ANOVA was conducted on EMG data obtained by comparing PTRCT patients with healthy individuals, and multiple comparisons by Tukey-Kramer test was conducted as the post facto official approval.
Results: We found a significant difference in the scapular muscle-activation ratio in upper rotation in the LT/SA ratio at 120° (p 0.05).Comparison between the individual muscle groups showed that activity of the LT increased as the measured angle widened, and the difference was significant at 120°(p 0.01) .
Conclusion(s): Our results suggest that changes in the upper rotation scapular muscle activation in patients with painful PTRCT occur as compensation for reduced articular torque in the glenohumeral joint.
Implications: When elevating the upper limb, the upper rotation muscle-activation ratio tends to change with the increase in the upper limb angle. Furthermore, a comparison of individual muscle activity showed increased activation of the LT with upper limb elevation.
Keywords: Painful partial-thickness rotator cuff tears, Upper rotation scapular muscle, Activation ratio
Funding acknowledgements: Department of Physical Medicine and Rehabilitation, Tohoku University Graduate School of Medicine
Topic: Musculoskeletal: upper limb; Musculoskeletal
Ethics approval required: Yes
Institution: IMS Meirikai Sendai General Hospital
Ethics committee: Tohoku University Graduate School of Medicine
Ethics number: Receipt number of ethics panel:2012
All authors, affiliations and abstracts have been published as submitted.
