Musculoskeletal Disorders. Sean Gallagher

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Figure 2.4 The site of de Quervain’s syndrome is encircled. APL: abductor pollicis longus; EPB: extensor pollicis brevis; EPL: extensor pollicis longus.

       Anatomy/pathology

De Quervain’s disease is a specific wrist tendinopathy involving the entrapment of the tendons of the extensor pollicis brevis and abductor pollicis longus. Figure 2.4 illustrates the region associated with the development of de Quervain’s syndrome. Patients with de Quervain’s disease (as well as trigger finger) tend to exhibit a lack of inflammation in the affected region (Clarke, 1998; Sbernardori & Bandiera, 2007). Instead, there appears to be a breakdown of tissues of the gliding layer of the tendon sheath. Examination of tendons tends to reveal nodularity and tendon fraying, which is thought to be secondary to impingement by the damaged sheath. Both disorders often exhibit the development of fibrotic tissue. In the case of de Quervain’s syndrome, deposition of fibrotic tissue in the extensor retinaculum can be thickened up to five times greater than the thickness in control tissues (Clarke, 1998). Overall, signs point to a process of tissue degeneration as opposed to an inflammatory response, with the degeneration resulting from abnormal mechanical stress being imposed on the tendon and the tendon sheath (McCauliffe, 2010).

       Risk factors/activities associated with hand‐wrist tendinopathy

      Tendinopathy of the hand, wrist, and forearm has long been associated with performance of forceful and repetitive hand activities as potential causal factors (e.g., Armstrong, 1987). Studies assessing risk factors associated with hand‐wrist tendinopathy demonstrate that exposure to force, repetition, and non‐neutral postures all demonstrate positive associations; however, the combination of force and repetition demonstrate the strongest relationship with these hand‐wrist disorders (Armstrong, 1987; Barbe et al., 2013; Byström, Hall, Welander, & Kilbom, 1995; Kurrpa, Viikari‐Juntura, Kuosma, Huuskonen, & Kivi, 1991; Luopajärvi, Kuorinka, Virolainen, & Holmberg, 1979; Roto & Kivi, 1984). The study by Kurrpa et al. (1991) was prospective in nature and found that greater time on the job was associated with increased risk of hand‐wrist disorders, demonstrating temporality. Repetitive forceful activity of the thumb is often associated with the development of de Quervain’s syndrome (Freivalds, 2004).

      Lateral tendinopathy of the elbow

       Characteristics/description

Lateral epicondylitis (commonly referred to as “tennis elbow”) is a disorder characterized by pain at or near the lateral epicondyle of the humerus. The pain may be localized to this region, may radiate down the extensor muscle group of the forearm, and occasionally may radiate proximally to the upper arm (Vaquero‐Picado, Barco, & Antuña, 2017). This pain can be triggered or exacerbated by contraction of the common extensor mass in response to a variety of activities (Ahmad et al., 2013). Tenderness is most often exhibited at the site of the attachment of the extensor carpi radialis brevis (ECRB) tendon; however, pain and tenderness on palpation can also be experienced around the prominence of the lateral epicondyle. Pain intensity can be quite variable and manifest as intermittent and mild to constant and severe. The latter can affect a wide range of daily activities and may even occur at night, thereby causing a disturbance in sleep.

       Epidemiology

      Studies suggest that the prevalence of lateral epicondylitis in the general population in the United Kingdom is approximately 1–3% and is more common in adults aged 35–55 years. Gender does not appear to play a significant role as to prevalence (Smidt & van der Windt, 2006). However, the examination of the prevalence rates of lateral epicondylitis in working populations provides a different picture. A study of the prevalence of lateral epicondylitis among workers at 12 worksites indicated a prevalence rate of 5.2% in the dominant arm (Fan et al., 2009). A Finnish study found that the true incidence of lateral epicondylitis was due to the overuse of or change in biomechanics as a result of elbow pain (Shiri, Viikari‐Juntura, Varonen, & Heliövaara, 2006). Incidence was found to be variable depending on the criteria used to confirm the diagnosis. They found it to be definitely present in 1.3% of the population between the ages of 30 and 65 years and likely present in a further 2.98%.

       Anatomy/pathology

In lateral epicondylitis, it is believed that a common extensor tendon (a conglomeration of the tendons of the extensor carpi radialis brevis, the extensor digitorum, the extensor digiti minimi, and the extensor carpi ulnaris) is affected by progressive process of inflammation and then degeneration (Figure 2.5). The degeneration of the tendon is the result of repetitive application of stress, leading to the microtear development in the common tendon (Kraushaar & Nirschl, 1999). The accumulation and growth of microtears is the process by which tendinosis initiates and propagates in the tendon. If the tendon continues to experience stress in this region, these pathologic changes may ultimately lead to partial or complete rupture of the tendon (Kraushaar & Nirschl, 1999).

Figure 2.5 Location of inflamed or injured tissues in the extensor carpi radialis brevis (ECRB) tendon.

      Jacobson, J. A., Chiavaras, M. M., Lawton, J. M., Downie, B., Yablon, C.M., & Lawton, J. (2014). Radial collateral ligament of the elbow: Sonographic characterization with cadaveric dissection correlation and magnetic resonance arthrography. Journal of Ultrasound in Medicine, 33(6), 1041–1048. DOI: 10.7863/ultra.33.6.1041. Wiley.