Musculoskeletal Disorders. Sean Gallagher

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       Risk factors/activities associated with CTS

      A review undertaken by the NIOSH included over 600 epidemiological studies concerning workplace factors associated with numerous MSDs (including CTS) (NIOSH, 1997). The summary of their review on CTS indicated strong evidence for a relationship between exposure to combinations of force and repetition, or force and posture, and development of CTS. CTS frequently presents in working‐aged adults, especially those experiencing prolonged and repetitive flexion and extension of the wrist, especially when combined with forceful gripping (Palmer, 2011). Other potential occupational risk factors may include exposure to HAV and/or exposure to cold conditions. There are several personal risk factors for CTS as well. Of these, being female is one of the strongest (Lee et al., 2019). Females have 2‐3 times the risk compared to males (Lee et al., 2019). Other common personal risk factors include increasing age, having a narrow carpal tunnel, previous wrist trauma or injury, diabetes, rheumatoid arthritis, hypothyroidism, and presence of other neurological disorders (Geoghegan, Clark, Bainbridge, Smith, & Hubbard, 2004).

      Cubital tunnel syndrome (ulnar nerve entrapment)

       Characteristics/description

      Cubital tunnel syndrome is the second most common mononeuropathy of the upper extremity (Cutts, 2007; Saito et al., 2018). It involves the entrapment of the ulnar nerve within the cubital tunnel at the elbow, which is of clinical significance since the ulnar nerve is one of the primary nerves supplying motor information to many forearm muscles and most of the hand muscles and sensory information from part of the hand. In addition to compression within the cubital tunnel, the ulnar nerve can also be compressed in the neck at cervical level 8 (C8), in the thoracic outlet (thoracic outlet syndrome), and at the wrist in Guyon’s canal (Fadel, Lancigu, Raimbeau, Roquelaure, & Descatha, 2017). A double crush syndrome is possible and would mean that the ulnar nerve is compressed in two or more of these various sites. Symptoms of cubital tunnel syndrome at any level of entrapment can lead to an intermittent altered sensation in the little and ring fingers, such as sensory loss (typically the first reported symptom), paresthesia (a burning or prickling sensation), or formication (the sensation of having insects crawling on or under the skin) (Fadel et al., 2017). As the condition progresses, there may be development of pain in the medial elbow and hand weakness, and eventually, atrophy of many of the intrinsic muscles of the hand.

       Epidemiology

      As with all nerve disorders, individuals with diabetes mellitus (diabetes type 2) have increased susceptibility for symptoms of ulnar nerve neuropathy, although these symptoms may occur secondary to a microvascular injury of the nerve, thus causing a local ischemia, or by interfering with local metabolism. Although there have been only a small number of studies examining occupational contributions to cubital tunnel syndrome, its prevalence ranges from 5.9 to 6.9% in workers in the Saint Louis metropolitan area (An, Evanoff, Boyer, & Osei, 2017), Missouri, USA (5.9%), a 6.9% prevalence rate in dock workers in Sao Paulo, Brazil (Saito et al., 2018), and 6.7% in floor cleaners in a systematic review performed in 2009 (van Rijn, Huisstede, Koes, & Burdorf, 2009). It is also reported to be more common in patients whose work involves protracted elbow flexion (e.g., holding a telephone) and flexion of the elbow on hard surfaces, workers who handle vibratory tools, and individuals with past elbow fractures, direct trauma of the ulnar nerve, or marked valgus or varus deformities of the elbow (Cutts, 2007; Saito et al., 2018).

       Anatomy/pathology

The ulnar nerve is formed from terminal branches of the medial cord of the brachial plexus and contains nerve processes that originate from spinal cord roots located at cervical 8 and thoracic 1 levels. The ulnar nerve descends distally down the arm toward the elbow just anterior to a medially located intermuscular septum (a connective tissue sheath that both divides and provides attachment for the triceps brachial muscles located posteriorly, and brachialis muscle located anteriorly). The ulnar nerve pierces this septum and passes through a fibro‐osseous space behind the medial epicondyle of the humus that is known as the cubital tunnel. Thereafter, the ulnar nerve passes between the two heads of the flexor carpi ulnaris muscle of the forearm before proceeding distally to the medial wrist and hand. The ulnar nerve innervates several medially located forearm muscles and most of the intrinsic muscles of the hand (such as those acting on the little and ring fingers, the medial two lumbricals, interosseous muscles, and two muscles of the thumb including the adductor pollicis).

      This anatomical arrangement places the ulnar nerve posterior to the elbow’s axis of motion, so that during elbow flexion, the nerve is required to stretch up to 5 mm longer than its length at rest as well as slide through the cubital tunnel (Cutts, 2007; Fadel et al., 2017). Alterations in the fibro‐osseous space and increase in intraneural pressure are believed to be key to the pathogenesis of cubital tunnel syndrome. Flexion of the elbow changes the cubital tunnel’s shape from ovoid to ellipse, decreases the cross‐sectional area of the space by 55%, and increases intraneural pressure up to 20 times higher than resting pressure (Apfelberg & Larson, 1973; Novak, Lee, Mackinnon, & Lay, 1994). The floor of the tunnel is made up of the elbow joint capsule and a supporting ligament; bones act as walls on either side (the medial epicondyle of the humerus and the olecranon process of the ulna), while the roof is made of elastic connective tissue (a retinaculum). This retinaculum has a variable structure (and may even be missing) with variations in its tightness perhaps also contributing to cubital tunnel syndrome (O’Driscoll, Horii, Carmichael, & Morrey, 1991).

       Risk factors/activities associated with cubital tunnel syndrome

      Although more studies are needed, known risk factors for cubital tunnel syndrome include work that involves holding the elbow in a flexed position for long periods, particularly when on a hard surface (Cutts, 2007), performing repetitive tasks with high force requirements (Fadel et al., 2017), and performing repetitive tasks with vibratory tools (Cutts, 2007). The prevalence for cubital tunnel syndrome is also higher in workers over 50 years of age and in those who have worked for more than 1 year in the job (thus, duration) (Saito et al., 2018; van Rijn et al., 2009). Obesity and presence of diabetes may also increase the risk, particularly for a mechanical double crush of the ulnar nerve (Cutts, 2007).

      Hand‐arm Vibration Syndrome

      Characteristics/description

      Hand‐arm vibration syndrome (HAVS) is a disorder associated with exposure to HAV, usually as the result of the prolonged use of powered hand tools. HAVS can be a painful and potentially disabling condition, with symptoms including pain, numbness, tingling, and nerve dysfunction. These symptoms can affect the hands, wrists, and forearms and may interfere with sleep. HAVS may also lead to a pallor or cyanosis of the fingers as well as numbness, tingling, and pain. Episodes typically last 5–30 min; however, the duration and severity of symptoms may increase with disease progression. Musculoskeletal symptoms can include decreased grip strength and, in some cases, Dupuytren’s contractions—a condition in which fingers in the hand (usually the two fingers farthest from the thumb)—are permanently contracted and cannot be fully straightened out.

      Epidemiology

HAV is defined as the transfer of vibration from a tool to a worker’s hand and arm. The amount of HAV is characterized by the acceleration level of the tool when grasped by the worker and in use. The vibration is typically measured on the handle of tool while in use to determine the acceleration levels transferred to the worker. HAVS was first widely recognized as a potential occupational hazard in the mid‐1980s. However, the earliest reports of vibration white finger (VWF) were СКАЧАТЬ