Clinical literature abounds with articles about repetitive injury and conditions related to the use of electronic devices, especially stationary or desktop computers and work stations. One of these conditions that frequently brings patients to the chiropractic clinical practice has been called "mouse shoulder." Here's how to identify and resolve this all-too-common condition.
British osteopath Jane O'Connor gives us a succinct description of the etiology of mouse shoulder, pointing out: "The shoulder and shoulder blade attach to the body by various muscles that insert into the spine, ribcage, neck and base of the skull. Holding a mouse ... causes these muscles to contract to support the weight of the arm."1 Dr. O'Connor also notes that repetitive strain can cause shoulder pain and weakness to the mouse user; and that similar injury may accompany other repetitive work-related tasks, such as operating machinery.
Ranasinghe, et al., observe that "complaints of arm, neck and/or shoulders (CANS) affect millions of office workers."2 They further differentiate the complaints by noting they are "not caused by acute trauma or by any systemic disease." The costs of CANS are astronomical. As the "leading cause of occupational illness in the United States," Bongers, et al., estimate that work-related neck and upper-limb problems cost industry "$45 to $54 billion annually."3
Signs and Symptoms
The patient with mouse shoulder tends to have a readily recognizable pattern of presenting complaints. They report fairly diffuse shoulder pain with focal interscapular point tenderness, and generalized myalgia over the upper trapezius. There may also be tenderness to digital pressure at the head of the glenohumeral joint and on the lateral humerus at the deltoid tubercle. Many patients recognize the underlying cause of their complaint to be associated with use of computers and other devices.
Common examination findings reveal taut and tender fibers in the shoulder and related muscles including the supraspinatus, deltoid, levator scapulae and upper trapezius. Deep palpation in the interscapular region on the side of shoulder involvement almost invariably shows tightness of deep paraspinal muscles such as the rhomboids.
Point tenderness is frequently encountered along the medial border of the scapula, as well as along the costovertebral junction of the upper thoracic spine. Rib humping and prominent interscapular soft-tissue bunching can be readily detected in most cases. A positive shoulder depressor finding often manifests on the side of shoulder involvement from chronic tightness in the upper trapezius.
The patient with mouse shoulder may also complain of intermittent numbness or tingling in the hands and distal extremities. However, biceps deep-tendon reflexes and vibrational sensitivity are usually within normal limits. The patient may demonstrate some pain-limited range of motion while abducting and externally rotating the involved shoulder.
A negative Codman (drop-arm) test helps to eliminate the likelihood of tears and other injuries to the rotator cuff muscles – notably the supraspinatus. Be alert to patient reports of pain in the rotator cuff and deltoid region during the Codman test, because that may be indicative of chronic overuse of the shoulder muscles.
One explanation for the mouse shoulder phenomenon may be contracture of interscapular muscles, especially the rhomboids and portions of the trapezius. Because these muscles are under constant and long-term load to stabilize the shoulder as the mousing arm is working, they may become fatigued and less pliable. Consequently, when the arm is raised or moved into abduction and rotation, the shoulder muscles encounter unanticipated resistance and demonstrate stiffness and pain with motion.
Correcting Mouse Shoulder
Chiropractic intervention for an uncomplicated presentation of mouse shoulder typically involves attention to three areas of involvement:
Adjusting procedures may use manual technique or instrument-assisted correction, or a combination of both.
Thoracic: Locate thoracic segments to be adjusted by palpating for taut and tender paraspinal fibers and prominent transverse processes on the side of involvement. These vertebral misalignments are almost always on the side of the shoulder complaint at the levels of T2-T4. To adjust an upper thoracic vertebra, take a scissors stance on the side of involvement. For a manual correction, use a single-hand contact with the fleshy pisiform of the inferior hand. Stabilize by placing the palm of the superior hand over the dorsum of the contact hand. Apply a posterior to anterior and slightly superior and medial thrust to the high transverse. For an instrument-assisted correction, contact the prominent transverse and apply a thrust with an anterior, medial and slightly superior line of drive.
Costovertebral: When a costovertebral articulation misalignment is present with a complaint of mouse shoulder – and it frequently will be – contact the rib manually or with the instrument, about a centimeter lateral to the transverse process. Apply an anterior and slightly lateral thrust to the rib. A manual thrust may also include a torque component (clockwise on the right, counterclockwise on the left) to facilitate release of the rib fixation. Release of the rib at the costotransverse articulation often produces immediate abatement of some of the symptoms associated with the mouse shoulder complaint.
Lower Cervical: Segmental fixation of a lower cervical vertebra – usually C7 or C5 – is frequently encountered with mouse shoulder. Use a conventional manual or instrument-assisted adjusting procedure to correct cervical segmental fixation.
Glenohumeral: Manual and instrument-assisted correction of the glenohumeral joint component of mouse shoulder usually involves a posterior and slightly superior thrust to the head of the humerus. One strategy for manual adjusting is to take a scissors stance at about the level of the patient's elbow. Use the inferior hand to take a broad stabilizing contact over the scapula. Reach under the shoulder and contact the exposed head of the humerus with a stabilized middle finger of the superior hand. Apply an anterior and superior thrust to the scapula with the inferior hand, while simultaneously using the superior hand to apply a posterior and superior thrust to the humerus.
This method tends to work most effectively using a table with a drop mechanism. To correct the glenohumeral joint with an instrument, reach over and retract the shoulder with the inferior hand. Apply a posterior and superior thrust to the exposed head of the humerus.
References
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