Ultrasound of tibialis anterior muscle and tendon: anatomy, technique of examination, normal and pathologic appearance

Abstract

Lesions of the tibialis anterior muscle and tendon are not frequently reported in international literature although pathology is not rare. Pathology can be spontaneous, associated with arthropathy or more generalized conditions. Clinical assessment may not be sufficient for distinguishing conditions like tendinopathy, tears, bursitis, etc. Therefore, imaging studies are necessary to plan appropriate therapy. US has a number of advantages, including widespread availability, absence of contraindications and low cost. It can also be used for dynamic studies of the muscle during contraction and relaxation. This article reviews the anatomy of the tibialis anterior, normal variants, the technique used for standard US examination of this muscle and tendon, its normal appearance on US and the sonographic characteristics of the most common lesions that affect it including tips on US-guided injections used for treatment.

Keywords: Muscle; Sonography; Tendon; Tibialis anterior.

Fig. 1

Tibialis anterior tendon anatomy. Axial schematic drawing. 1 tibialis anterior tendon, 2 extensor hallucis longus tendon, 3 extensor digitorum longus tendon. LM lateral malleolus, MM medial malleolus

Fig. 2

Tibialis anterior tendon anatomy. Coronal schematic drawing. 1 tibialis anterior tendon, 2 extensor hallucis longus tendon, 3 extensor digitorum longus tendon. TS tendon sheath of the tibialis anterior tendon. LM lateral malleolus, Fib fibula. Sup Ret superior extensor retinaculum, Inf Ret inferior extensor tendons retinaculum

Fig. 3

Tibialis anterior tendon anatomy. Sagittal schematic drawing. 1 tibialis anterior tendon. TS tendon sheath of the tibialis anterior tendon. LM lateral malleolus, 1 Mt first metatarsal, 1 Cn medial cuneiform, Nav navicular, Fib fibula. Sup Ret superior extensor retinaculum, Inf Ret inferior extensor tendons retinaculum

Fig. 4

Tibialis anterior tendon US anatomy. a–d Transverse sonograms obtained from proximal to distal over the tibialis anterior tendon (arrows). Note how the tendon runs below the superior extensor retinaculum in (b) and in between a split of the retinaculum in (c). In (d) the arrowheads point to the inferior extensor retinaculum. Curved arrow extensor hallucis longus tendon, EHLm extensor hallucis longus muscle, MCn medial cuneiform

Fig. 5

Tibialis anterior muscle herniation. Axial sonograms obtained over the anterolateral aspect of the middle third of the leg, without (a) and with (b) local compression through the transducer, (b) longitudinal sonogram, (d) tangential radiograph. In (a) the anterior fascia (black arrow) of the tibialis anterior muscle (TAm) is torn and allows herniation of the muscle. In (b) local pressure reduces the herniation. Longitudinal sonogram depicts the defect (black arrows) in the fascia. Radiograph shows focal bulging of the muscle

Fig. 6

Tibialis anterior muscle hypotrophy. a Axial sonogram obtained over the anterolateral aspect of the middle third of the leg. b Corresponding T1 weighted MR image, c normal contralateral MR image. In (a) the tibialis anterior muscle (black arrows) appears smaller than the adjacent extensor digitorum longus muscle (EDL). Note its hyperechoic appearance related to fat infiltration. MR image (b) correlates well with US. Note the normal tibialis anterior muscle (white arrow) in (c)

Fig. 7

Tibialis anterior distal tendinopathy. a, b Longitudinal gray-scale and color Doppler sonograms obtained over the distal tibialis anterior tendon. (c) Transverse color Doppler sonogram. In (a) the middle tendon (white arrow) is normal, the distal tendon (black arrow) is swollen, irregular and hypoechoic. Note local hypervascular changes in (b). Transverse image shows the selective involvement of the tendon band inserting onto the medial cuneiform (MCn), the smaller tendon band inserting onto the first metatarsal is normal (small arrow)

Fig. 8

Tibialis anterior partial tear. a, b Longitudinal gray-scale sonograms obtained over the two bands of distal tibialis anterior tendon. c Transverse sonogram. d MR STIR image corresponding to (c). In (a) the tendon band (black arrow) inserting onto the medial cuneiform (MCn) is torn. The proximally tendon is swollen, hypoechoic and retracted (broken arrow) to the level of the tarsal navicular (Nav). In (b) the tendon band (white arrow) inserting onto the first metatarsal is normal. Transverse US and MR images (c, d) show selective tear of the tendon band inserting onto the medial cuneiform (black arrows), the tendon band inserting onto the first metatarsal is continuous (white arrows)

Fig. 9

Tibialis anterior complete tear. Longitudinal gray-scale sonogram of the tibialis anterior tendon shows the retracted irregular and swollen proximal tendon (large black arrow) and the distal tendon stump (small black arrow). Note the tendon sheath filled by fluid and debris (asterisk). TH talar head, Nav navicular, MCn medial cuneiform

Fig. 10

Tibialis anterior bursitis. a–b Axial and longitudinal sonograms obtained over the distal tibialis anterior tendon. c Standard radiograph and (d) MR STIR image corresponding to (b). The distal tendon (white arrows) is normal. Bursitis is seen as a fluid collection (asterisks) located between the tendon and the joint plane. Radiograph shows a focal nonspecific soft-tissue swelling (arrowheads). MR shows the normal tendon partially surrounded by the fluid collection

Fig. 11

Tibialis anterior distal bursitis. US-guided injection. a, b Longitudinal sonograms obtained over the distal tibialis anterior tendon and the adjacent bursitis. c Axial sonogram obtained before (c) and during (d) US-guided intrabursal injection. The tibialis anterior tendon (arrows) is normal. Note local bursitis (asterisks) probably due to local impingement on tarsal dorsal osteophytes (black arrowheads). In (d) US shows the needle (white arrowheads) correctly positioned inside the bursa. Note injected steroid with resultant posterior comet-tail artifact (curved arrow). Nav navicular, MCn medial cuneiform