Flexor Pollicis Longus

Anterior Interosseus Nerve, Median Nerve, Lateral and Medial Cords, Anterior Divisions, Middle and Lower Trunks, C7, C8, Tl. 

The volar surface of the body of the radius from the bicipital tuberosity to the attachment of the pronator quadratus and interosseus membrane. 

Volar surface of base of distal phalanx of thumb. 

In the middle of the forearm the needle electrode is inserted from the radial aspect just volar to the radius. The electrode will travel through the flexor carpi radialis and the flexor digitomm superfi-cialis. 

If the needle electrode is inserted too superficially it will be in the flexor digitomm sublimis. 

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A useful clinical maneuver to assess the state of the ulnar nerve is the Froment s test . The patient is asked to pinch a sheet of paper between thumb and index finger. In case of overt ulnar neuropathy, the patient grasps the paper by flexing the thumb (activation of the median-innervated flexor pollicis longus as a compensation for the weakness of dorsal interosseous muscles) (see Sect. 8.5.4.3). In patients with cubital tunnel syndrome, palpation of the ulnar nerve at the cubital tunnel may be painful and may reproduce symptoms. 

At the volar aspect of the wrist, nine flexor tendons enter the carpal tunnel to reach the fingers. There are four tendons from the flexor digitorum superficialis for the second through fifth fingers, four from the flexor digitorum profundus for the same fingers and the flexor pollicis longus tendon. 

Fig. 10.27a,b. Bifid median nerve, a Schematic drawing and b corresponding transverse 12-5 MHz US image over the ventral wrist in an asymptomatic subject reveal the radial and ulnar trunks (arrows) of a bifid median nerve. Sea, scaphoid Pis, pisiform Jpl, flexor pollicis longus tendon p and s, the tendons of the flexor digitorum profundus and superficialis... 

The flexor pollicis longus tendon traverses the thenar eminence between the superficial and deep bellies of the flexor pollicis brevis muscle. It then enters the osteofibrous canal of the thumb to insert at the volar aspect of the base of the distal phalanx. At the metacarpal head level, this tendon courses between two sesamoid bones, one (lateral) included in the combined tendon of the flexor pollicis brevis and abductor pollicis longus, the other (medial) in the adductor pollicis tendon. 

Fig. 11.38a,b. Complete tear of the flexor pollicis longus tendon in a patient with severe rheumatoid arthritis, a Longitudinal 12-5 MHz US image over the thenar compartment displays the distal end (arrowheads) of the ruptured flexor pollicis longus (arrows), which appears irregular and diffusely hypoechoic with loss of the fibrillar echoes. Observe the posterior acoustic shadowing (asterisks) related to sound-beam refraction, b Contralateral normal tendon (arrows)... 

Fig. 11.40a-d. Failed surgical repair for a complete tear of the flexor pollicis longus tendon, a Longitudinal 12-5 MHz US image obtained over the thenar compartment reveals an empty tendon sheath (open arrows) containing hypoechoic fluid and the proximal retracted end of the tendon (white arrows). Note the hyperechoic surgical stitches (arrowheads) at the tip of the tendon end. b-d Correlative transverse 12-5 MHz US images obtained at the levels (vertical white bars) indicated in a... 

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