65 Repetitive Strain Injury

Repetitive Strain Injury

Repetitive Strain injury (RSI) is defined as an injury that has resulted from repeated stress affecting specific tendons, muscles, and associated nerves and blood vessels.

RSIs are reported by approximately 10% of Canadian workers (over 20 years of age) every year, with a RSI that has limited their ability to perform daily tasks.  RSI most commonly affects the neck, shoulder, upper back, arm, wrist, hand and fingers.  RSIs include overuse and repetitive strain injuries resulting in tendonitis, as well as peripheral nerve entrapment disorders (e.g., carpal tunnel syndrome).

Examples of tendon-related disorders

Rotator cuff tendonitis (i.e., due to repetitive lifting, swimming, throwing, playing volleyball),

Tennis elbow (e.g., lateral epicondylitis),

Golfer’s and baseball elbow (e.g., medial epicondylitis)

Jumper’s knee (e.g., patellar tendinitis)

Examples of peripheral nerve entrapment disorders

Carpal tunnel syndrome (wrist)

Cubital tunnel syndrome (elbow)

Risk Factors – Repetitive Strain Injury

Risk factors for developing a RSI include: repetitive activities, workload stress, genetics, family history, biological sex, and age.  Geographical location is also a risk factor, possibly due to type of occupation and sociocultural expectations for workload.  RSIs can be bilateral, but when affecting the upper extremities are most often unilateral, localized in the dominant arm, hand, or wrist.

Biological females report more symptoms, possibly due to differences in genetic or anatomical susceptibilities, or differences in activity levels.  Currently in the USA, carpal tunnel syndrome (CTS) is diagnosed in 3 to 10 times more females than males, with peak age between 45-60 years old. CTS is associated with increased BMI and low aerobic fitness.  Other predisposing factors include diabete mellitus, rheumatoid arthritis, prior injuries to the region.

Signs and Symptoms – Repetitive Strain Injury

RSIs give rise to signs and symptoms that can include inflammation (swelling, pain, redness, and warmth), stiffness, loss of strength, loss of coordination, sensory problems (e.g., numbness, tingling), and changes in skin colour or skin temperature (hot or cold).

Pathogenesis – Carpal Tunnel Syndrome

The carpal tunnel is located at the base of the palm, and is a space through which the median nerve and nine flexor tendons (and their tendon sheaths) pass through.  The posterior part of the space is lined by the carpal bones that form a posterior arch and the anterior part of the carpal tunnel space is enclosed by the carpal ligament which bridges from left to right across the bottom of the palm. The carpal tunnel space is narrow and the development of edema and pressure causes obstruction to blood flow that supplies the tissues in this region.  It has been found that a square-shaped wrist and thickened carpal ligament create a smaller carpal tunnel which predisposes to the development of CTS.

In CTS, inflammation in the wrist’s carpal tunnel region results in the median nerve becoming compressed and then progressively damaged (due to the ensuing ischemia).  Often sensory neurons are affected first, followed by motor neurons.  Paresthesia and muscle atrophy may occur and worsen if CTS is not treated.

Diagnostic Tests – Carpal Tunnel Syndrome

Many tests are done to rule out other disorders as well as assess the problem.  These tests can include physical examination, sensory and motor tests, electromyography (EMG), nerve conduction studies (NCS), and imaging (e.g., ultrasound, MRI).

Treatment – Carpal Tunnel Syndrome

Treatments include initiating recommended ergonomic workplace changes and body positioning while working, PRICE (Protection, Rest, Ice, Compression, Elevation), NSAIDs, and a rehabilitation program that typically includes a healthy lifestyle (food-guide based diet, daily physical activity, and stretching exercises).

Other conservative treatments involve using wrist splints to keep the wrist straight or neutral (rather than bent) especially while sleeping which can help minimize day and night-time symptoms.

Corticosteroid injections and/or surgical interventions are usually recommended for individuals when improvements do not occur with conservative treatments and lifestyle modifications.  Surgery often involves carpal tunnel release (i.e., the cutting of the transverse carpal ligament).