Carpal tunnel: Normal anatomy, anatomical variants and ultrasound technique

Abstract

KEYWORDSCarpal tunnel; Ultrasound; Flexor tendons; Median nerve.Abstract The carpal tunnel is an osteofibrous canal situated in the volar wrist. The boundaries are the carpal bones and the flexor retinaculum. In addition to the medial nerve, the carpal tunnel contains nine tendons: the flexor pollicis longus, the four flexor digitorum superficialis and the four flexor digitorum profundus. Ultrasound (US) study of the carpal tunnel generally involves short-axis imaging of the tendons, and in the presence of disease, long-axis imaging and dynamic maneuvers are added. There are numerous reports of anatomical variants of the wrist involving vessels, nerves, tendons and muscles, and they can all be studied by US. Some are particularly relevant from a clinical point of view and will therefore be accurately described. The anatomy is complex, and the US operator should therefore be thoroughly familiar with the normal anatomy as well as the anatomical variants that may have a role in the pathogenesis of carpal tunnel syndrome or influence treatment.Sommario Il tunnel carpale è un canale osteo-fibroso localizzato nella regione volare del polso, delimitato profondamente, medialmente e lateralmente dalle ossa del carpo e superficialmente dal retinacolo dei flessori. Al suo interno decorrono nove tendini: il flessore lungo del pollice, i quattro flessori superficiali delle dita, i quattro flessori profondi delle dita ed un nervo, il mediano. Lo studio ecografico del tunnel carpale avviene generalmente per asse corto rispetto ai tendini ed è completato, almeno in presenza di patologia, da scansioni per asse lungo e manovre dinamiche. A livello del polso esistono poi numerose varianti anatomiche coinvolgenti vasi, nervi, tendini e muscoli, tutte ben valutabili ecograficamente. Alcune hanno una maggior rilevanza clinica e sono pertanto oggetto di una descrizione più accurata. L'anatomia normale è complessa, ma la sua conoscenza è essenziale per lo studio della patologia, come è essenziale la conoscenza delle varianti anatomiche che possono avere un ruolo nella patogenesi della sindrome del tunnel carpale o condizionarne le terapie. ª

The influence of wrist posture, grip type, and grip force on median nerve shape and cross‐sectional area

“…Nine tendons and the median nerve pass through the carpal tunnel (Presazzi et al, 2011). Nine tendons and the median nerve pass through the carpal tunnel (Presazzi et al, 2011).…”

Can decrease in hand grip strength in carpal tunnel syndrome be explained by interosseous muscle and intermetacarpal space dimensions?

“…Especially following long-term functional hand use, numbness, tingling and burning sensations are experienced in the thumb, index finger, middle finger, and radial half of the ring finger Motor symptoms such as weakness in the strength of the fingers, clumsiness and difficulty in daily life activities cause an impairment in life quality. Typically, the 190 Eur Res J 2018;4(3): [187][188][189][190][191][192] Decrease in hand grip strength in carpal tunnel syndrome dominant hand is affected [11,12]. Anatomical variations (narrow tunnel, persistent median artery), nerve compression susceptibility (diabetes mellitus, systemic neuropathy), systemic and endocrine diseases (pregnancy, amyloidal, hypothyroidism) or space-occupying lesions in the tunnel are some of the predisposing factors [5].…”

Normal Sonographic Anatomy of the Wrist With Emphasis on Assessment of Tendons, Nerves, and Ligaments

“…The flexor pollicis longus tendon, located at the radial border of the carpal tunnel, has its own sheath. The tendons of the flexors digitorum superficialis and profundus overlap on the ulnar side of the tunnel and share a common sheath 8 , 18 . The Guyon canal (Figure 6) is superficial to the carpal tunnel and extends from the pisiform to the hook of the hamate.…”

“…The tendons of the flexors digitorum superficialis and profundus overlap on the ulnar side of the tunnel and share a common sheath. 8,18 The Guyon canal ( Figure 6) is superficial to the carpal tunnel and extends from the pisiform to the hook of the hamate. It is delimited dorsally by the flexor retinaculum (floor) and volarly by the palmar carpal ligament, which is the distal extent of the antebrachial fascia and the palmaris brevis muscle (roof).…”