Analysis of the morphometry and variations in the extensor digitorum brevis muscle: an anatomic guide for muscle flap and tendon transfer surgical dissection

Abstract

The extensor digitorum brevis muscle (EDB) is a practical option for use as an island flap or free flap when reconstructing soft tissue defects in the ankle as well as in the entire lower limb. It is frequently used to correct crossover toe deformity and other painful toe disorders. We evaluated the morphometry of the EDB in 44 formalin-fixed limbs. Length and width of the muscles were measured. Surface area was calculated as the product of length and width of the muscle. The length of each tendon was also measured from its origin to the point of distal attachment. Presence of any additional tendons was noted. Mean length, width, and surface area of the muscle were 7.39±0.71 cm, 4.1±0.37 cm, and 30.5±4.78 cm(2) on the right side and 7.2±0.84 cm, 3.9±0.37 cm, and 28.4±5.35 cm(2) on the left side, respectively. Morphometry of the tendons revealed that the tendon of the great toe had the highest mean length (9.5 cm) and the tendon of the fourth toe had the lowest mean length (6.3 cm). Four of the limbs studied (9.09%) had only three tendons. Three of the limbs studied (6.81%) had five tendons, and in one exceptional case (2.27%), six tendons were detected. These observations have significant value and are applicable to plastic and orthopedic surgery.

Keywords: Crossover toe deformity; Extensor digitorum brevis; Morphometry; Reconstruction; Tendon transfer.

Fig. 1

Dissection of the dorsum of the right foot showing the proximal and distal attachments of the extensor digitorum brevis (EDB) muscle. EDL, extensor digitorum longus; ML, muscle length; MW, muscle width; TL1, length of tendon to the great toe; TL2, length of tendon to the second toe; TL3, length of tendon to the third toe; TL4, length of tendon to the fourth toe.

Fig. 2

Dissection of the dorsum of the left foot showing the proximal and distal attachments of the extensor digitorum brevis (EDB) muscle. Note that the number of EDB tendons is only three and the tendon for the fourth toe is absent. MF, muscle fasciculus; T1, tendon to the great toe; T2, tendon to the second toe; T3, tendon to the third toe.

Fig. 3

Dissection of the dorsum of the left foot showing the proximal and distal attachments of the extensor digitorum brevis (EDB) muscle. Note the additional EDB tendon for the second toe (T2a). T1, tendon to the great toe; T2, tendon to the second toe; T3, tendon to the third toe; T4, tendon to the fourth toe.

Fig. 4

Dissection of the dorsum of the left foot showing the proximal and distal attachments of the extensor digitorum brevis (EDB) muscle. Note the additional EDB tendon for the third toe (T3a). T1, tendon to the great toe; T2, tendon to the second toe; T3, tendon to the third toe; T4, tendon to the fourth toe.

Fig. 5

Dissection of the dorsum of the right foot showing the proximal and distal attachments of the extensor digitorum brevis (EDB) muscle. Note that the second head (SH) of EDB is divided into three tendons: medial, intermediate, and lateral. The medial tendon (PP2) is attached to the base of the proximal phalanx of the second toe. The intermediate tendon is attached to the fascia over the shaft of the third metatarsal bone (M3). The lateral tendon is inserted to the lateral side of the extensor digitorum longus tendon for the second toe (EDL2). EHL, extensor hallucis longus; T1, tendon to the great toe; T2, tendon to the second toe; T2a & T2b, additional tendons from the SH of EDB; T3, tendon to the third toe; T4, tendon to the fourth toe.