Posterior Deltoid Function After Transfer of Branch to the Long Head Triceps Brachii of the Radial Nerve to the Anterior Branch of the Axillary Nerve

PURPOSE

The aim of this study was to evaluate the function of the posterior part of the deltoid after nerve transfer of the long head triceps branch of the radial nerve to the anterior branch of the axillary nerve in patients with an upper brachial plexus injury or isolated axillary nerve injury.

METHODS

We retrospectively reviewed 26 patients diagnosed with an upper brachial plexus injury or isolated axillary nerve injury who underwent nerve transfer of the long head triceps muscle branch of the radial nerve to the anterior branch of the axillary nerve in our institute between 2012 and 2017. Data on age, sex, the mechanism of injury, the pattern of injury, and operative treatment were collected from medical records. Preoperative and postoperative clinical examinations, including motor powers of shoulder abduction and extension according to Medical Research Council grading, were evaluated. At a minimum of 2 years after the operation, we evaluated the recovery of the posterior deltoid function using the swallow-tail test.

RESULTS

Twenty-two patients (84.6%) had recovery of posterior deltoid function confirmed by the swallow-tail test. There were 23 patients (88.5%) who achieved at least Medical Research Council grade 4 of shoulder abduction.

CONCLUSIONS

Nerve transfer from the branch to the long head triceps to the anterior branch of the axillary nerve is an effective technique for restoring deltoid function in an upper brachial plexus injury or isolated axillary nerve injury. This technique can provide shoulder abduction and shoulder extension, which are the functions of the posterior deltoid muscle.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Electromyographic and kinematic study of reverse total shoulder arthroplasty: an observational prospective cohort study

BACKGROUND

Reverse total shoulder arthroplasty (RTSA) procedures have significantly increased in the last decade as an alternative to the current treatments for cuff-tear arthropathy. Since Grammont's theory in 1987, few data about the in vivo kinetics of the shoulder-girdle musculature in patients with RTSA have been available. The goals of this study are to (1) describe the contribution of principal muscles around the shoulder by electromyography and (2) access the range of motion of 5 movements of patients with RTSA compared with normal shoulders.

METHODS

This is an observational prospective cohort study of 21 patients divided into 11 patients with RTSA and 10 controls. The muscular activity was recorded with bipolar cutaneous electrodes, whereas the range of motion was synchronized and recorded by 8 motion cameras. Five movements (flexion, abduction, neutral external rotation, external rotation in 90° of abduction, and internal rotation in 90° of abduction) were studied.

RESULTS

The upper trapezius is the main activator in all directions with early and constant activity (P < .01). The latissimus dorsi demonstrates increased muscular activity in internal rotation (P < .01) as well as the posterior deltoid in external rotation in the RTSA group compared with control (P < .01).

CONCLUSION

RTSA shoulder muscle activation is significantly different than in normal shoulders. The significant contribution of the trapezius in all directions, latissimus dorsi in internal rotation, and posterior deltoid in external rotation has never been described within the same study until today. New rehabilitation protocols targeting those muscles could demonstrate better and more homogeneous results and increase patient satisfaction.

Electromyographic analysis of selected shoulder muscles during rehabilitation exercises

BACKGROUND

Overhead work-activities and repetitive use of arm in occupational tasks are known risk factors to cause shoulder injury that often develops to functional disability. Rehabilitation exercises (REs) are capable of slowing this development.

OBJECTIVE

The main objective of the present work is to experiment with common REs and to identify those which produce significant integrated electromyography (iEMG) activation of selected shoulder muscles namely, posterior deltoid, infraspinatus, teres minor, upper trapezius, middle trapezius and lower trapezius.

METHODS

  Ten healthy male occupational workers, exposed to the risk of shoulder injury, performed six REs while iEMG activities of concerning muscles are recorded using Biopac MP 150 system. REs are cross-examined statistically to select those which yield higher iEMG activations.

RESULTS

Results indicate that upper trapezius presents the highest iEMG activity in exercise 6 (standing ER at 90∘ abduction and 90∘ elbow flexion). Middle trapezius and lower trapezius show highest activation in exercise 1 (prone horizontal abduction at 90∘ with full external rotation with thumb right up). Also, posterior deltoid, infraspinatus, and teres minor have the highest iEMG activity in this exercise.

CONCLUSIONS

Results provide basic information to select appropriate rehabilitation programs for occupational workers exposed to the risk of shoulder injury.

TESTING INFRASPINATUS AND DELTOID MUSCLES WITH NEW TECHNIQUE TO DECREASE DELTOID ACTIVITY DURING TESTING USING EMG ANALYSIS

BACKGROUND

Muscle strength testing of an injured infraspinatus muscle (IM) is confounded by actions of synergistic muscles such as the posterior deltoid (PD).

HYPOTHESIS/PURPOSE

The purpose of this study was to describe a condition for testing of the IM that results in less EMG activity of the PD musculature. The researchers hypothesized that greater inhibition of the PD could be achieved through active adduction (AA), creating reciprocal inhibition of the PD.

STUDY DESIGN

Prospective cohort descriptive study.

METHODS

Thirty-four (19 females and 15 males) right-handed subjects between the ages of 22- 31 (mean 24.2 years + /- 6.2) with no previous history of shoulder surgery or pathology participated. Surface electrodes were placed over the muscle bellies of the IM and PD of the right shoulder along with a ground electrode over the C7 spinous process. EMG activity was recorded during resisted external rotation in four different testing conditions (seated active and passive adduction, and side-lying active and passive adduction). The order of test positions was randomly assigned, and each subject completed all four positions with appropriate rest. During AA conditions, subjects were asked to adduct the humerus against a sphygmomanometer (using 80% maximum force output) while maximal effort external rotation was manually resisted.

RESULTS

PD activity was significantly less during AA than with no AA (p<0.05) in both test positions. No significant difference occurred between IM EMG activity in the various test conditions.

CONCLUSION

The results of this study suggest that clinicians can reduce activity of the PD without reducing activity of the IM by using AA of the humerus before applying manual resistance to test the IM during manual muscle testing.

LEVELS OF EVIDENCE

1b.

Rapid plasticity of motor corticospinal system with robotic reach training

Goal-directed reaching is important for the activities of daily living. Populations of neurons in the primary motor cortex that project to spinal motor circuits are known to represent the kinematics of reaching movements. We investigated whether repetitive practice of goal-directed reaching movements induces use-dependent plasticity of those kinematic characteristics, in a manner similar to finger movements, as had been shown previously. Transcranial magnetic stimulation (TMS) was used to evoke upper extremity movements while the forearm was resting in a robotic cradle. Plasticity was measured by the change in kinematics of these evoked movements following goal-directed reaching practice. Baseline direction of TMS-evoked arm movements was determined for each subject. Subjects then practiced three blocks of 160 goal-directed reaching movements in a direction opposite to the baseline direction (14 cm reach 180° from baseline direction) against a 75-Nm spring field. Changes in TMS-evoked whole arm movements were assessed after each practice block and after 5 min following the end of practice. Direction and the position of the point of peak velocity of TMS-evoked movements were significantly altered following training and at a 5-min interval following training, while amplitude did not show significant changes. This was accompanied by changes in the motor-evoked potentials (MEPs) of the shoulder and elbow agonist muscles that partly explained the change in direction, mainly by increase in agonist MEP, without significant changes in antagonists. These findings demonstrate that the arm representation accessible by motor cortical stimulation under goes rapid plasticity induced by goal-directed robotic reach training in healthy subjects.