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Repetitive Strain Injuries (RSI)
The Anatomy of the RSI Epidemic
Repetitive Strain Injury (RSI) is fast becoming one of the most common forms of disability in the workplace. In some industries it is already the number one cause of a temporary and permanent disability. In this article I will explain why and how we develop the elusive RSI.
The definition of RSI:
Repetitive strain injury is a medical term used to describe a pain or discomfort of the upper limb. Although a ‘repetitive strain’ can occur in any area of the body, physicians typically apply the term to a pain of the arm unit including the neck, shoulder upper back, arm, forearm and hand, that is related to repetitive tasks. RSI is really an umbrella term used to catch any and all pains of the arm, but the most common forms include tennis and golfer’s elbow, carpal tunnel syndrome, ulnar neuritis, metacarpalgia, rotator cuff of the shoulder, chronic neck and upper back pain and limb numbness.
The signs and symptoms of RSI:
The signs and symptoms of RSI vary depending on the exact areas of the arm and neck involved in the pain syndrome; however, the most common RSI complaints include the following:
Background of RSI:
RSI is considered a soft tissue pain syndrome whereby the pain is derived from a disorder of the muscles and tendons of the neck and limb. To fully understand how muscles can cause disease, it is important to understand the current principles of myofascial pain (MFP) and myofascial dysfunction (MFD).
To explain, these deep spinal muscles change the spinal positioning, cause mal-rotation of the vertebrae and non-movement of the spinal segments. This will lead to premature or accelerated disk wear, disk herniation, arthritis of the facet joints, and increase the risk of compression fractures of the vertebrae. This is true at all locations of the spine, but is more prevalent at the levels of C1 to C2, C4 to C6, T11 to L1 and L4 to S1. In the case of RSI, we are typically seeing compression of the segments of C4 to C7.
Application of these principles:
Let’s look at the typical assembly worker. He or she will often perform the same group of tasks and use the same muscle groups of the neck and arm as much as six hundred times per day. The basic effect is to overwork / exercise the muscles of the neck and arm. The first changes that occur are of typical shortening of the deep spinal muscles of the base of the neck (multifidus and deep rotators) and of the shoulder outlet and forearm muscles. Specifically I see shortening and scarring at the levels of C4 to C7 and of the back of the shoulder (latissimus dorsi and subscapularis) and of the front of the shoulder (pectoral minor and major), shortening and scarring of the forearm and hand muscles (forearm flexors, extensors and hand metacarpals) are all generally affected to some degree.
Early on, the exam will show mild trigger point or tenderness along the muscle groups mentioned above. Some weakness is often present as the muscles are working below their maximum of their efficiency as a result of being shortened. The individual will often have only slightly reduced range of motion of the neck and arm unit. However, over time the range of motion becomes obviously reduced and the pain symptoms increase as the condition progresses. X-ray and CAT scan imaging will show loss of normal curvature of the neck, and examination will show forward rolling of the shoulders, winging of the scapula, decreased pulse with elevation of the limb, and even acute joint swelling of the affected joints.
The loss of normal curvature in the neck indicates prolonged and persistent shortening of the deep spinal muscles of the neck; a so-called tenting effect. As the muscles tighten, they ratchet the neck straight like a tent pole under tension. The effect on the spine is to create a persistent compression on one or more disk and vertebrae. As well, the natural or normal positioning of the vertebrae and disks is altered. The range of motion of the spinal segments becomes obviously reduced as several vertebrae actually fail to move. Disks come under pressure and start to wear at their sidewalls, much like a deflated car tire supporting an over-weighted car. The affected vertebrae will have a slight rotation to the affected side caused by the pull of the intrinsic muscles. Disk bulging and herniation can occur and can also oscillate between bulge and herniation in the early phase of disease. This explains reduced diagnostics of disk herniation during MRI in the supine position as compared to the Standing MRI. Eventually, frank herniation is seen on supine MRI.
With increasing neck compression the nerve conduction in the neck supplying the arm becomes more and more affected. Initially the nerve is temporarily and only partially interrupted. Over time, as the spinal compression and rotation deepens, the nerve interruption becomes more constant and severe. Muscles down the affected arm will shorten following a supply pattern according to nerve roots affected (Cannon’s Law). As well, repeated local muscle injury from continued repetitive work will contribute to further limb muscle shortening.
Certain Muscle groups will contribute to different symptoms of numbness, tingling, pain and weakness of the arm. In carpal tunnel, the pectoral (chest muscle) shortening will cause a traction injury to the median nerve at the front of the shoulder. This in turn, causes a pulling effect on the nerve which translates to the nerve being lifted and then caught at the undersurface of the carpal tunnel. Entrapment and swelling of the nerve will then cause numbness, tingling and pain of the thumb, index, middle and half of the ring finger recreating the ever popular pattern of carpal tunnel syndrome.
In ulnar neuritis, the lattissimus dorsi and the subscapularis muscles will shorten from reduced nerve supply of C6 to T1. This shortening will then cause a similar traction phenomenon of the ulnar nerve at the back of the shoulder. This traction will then cause the ulnar nerve to catch at the elbow causing golfers-like elbow pain and pain over the nerve when leaning on the elbow. As this progresses, the ulnar nerve actually rolls over the inner elbow or medial epicondyle and can be felt by examination by palpating the medial epicondyle and while flexing the elbow. This indicates very significant traction of the ulnar nerve coming from the back of the shoulder – otherwise known as posterior thoracic outlet syndrome. The classical symptoms will be of numbness and tingling of the little fingers and eventually pain in the fingers and ulnar side of the hand.
In tennis elbow, the outer elbow (extensors) can shorten and scar as a result of compression of C4 to C6 in the neck (due to contractures within deep intrinsic muscles of the neck at these levels) . The forearm shortening will cause persistent tension of the extensor tendon which causes inflammation of the tendon. The persistent shortening of the extensor group will apply traction to the lateral epicondyle of the affected arm causing pain, swelling and bony changes over the elbow. This mechanism helps to explain the difficult nature in treating tennis elbow, as well as the high failure rate with local elbow therapy.
Golfer’s elbow has a similar mechanism to tennis elbow, only the spinal segments involved are typically C6 to T1. Often golfer elbow is associated with ulnar neuritis as the same spinal segments are involved. Other conditions can be recreated by similar spinal and limb muscle patterns.
Computer-related RSI often proves to be more ominous than assembly work. The problem is that keyboarding is a static injury. It is evident that static repetitive work is possibly the worst case scenario, as static muscles not only shorten after injury, but also at the time of injury. In this case the weakness of the muscles can be more exaggerated as the static repetitive action does not allow for increase in muscle strength as compared with standard active repetitive work.
Furthermore, the computer-related RSI often affects the upper back area (thoracic spine); an area which has secondary nerve supply to the arm. The thoracic spine can be extraordinary to treat particularly in the presence of kyphosis. The end result of computer-related RSI is a person with a hump back, forward neck, forward shoulders, compressed disks, suffering diffuse muscle shortening and multiple entrapped nerves, and typically affecting both arms.
The Treatment of RSI: