Muscular variation on the dorsum of the foot and alteration of structures passing under cover of
the extensor retinacula of the lower limb – a case report
1Huban
Thomas. R*,2Prasanna, LC, 3Suhani S, 4Sneha G, 5 Prakash Babu B
1. Senior Grade Lecturer,
Department of Anatomy,
Kasturba Medical College,
Manipal University,
Manipal, India.
2. Associate Professor,
Department of Anatomy,
Kasturba Medical College,
Manipal University,
Manipal, India.
3. Senior Grade Lecturer,
Department of Anatomy,
Kasturba Medical College,
Manipal University,
Manipal, India.
4. Professor and Head
Department of Anatomy,
Kasturba Medical College,
Manipal University,
Manipal, India.
5. Associate Professor,
Department of Anatomy,
Kasturba Medical College,
Manipal University,
Manipal, India.
Corresponding Author
Huban Thomas R
Senior Grade Lecturer,
Department of Anatomy,
Kasturba Medical College,
Manipal University,
Manipal, India.
E-mail:huban_anatomy@yahoo.co.in,
Mobile No: +91 9844343546
Muscular variation on the dorsum of the foot and alteration of structures passing under cover of
the extensor retinacula of the lower limb – a case report
1Huban
1
Thomas. R*,2Prasanna, LC, 3Suhani S, 4Sneha G, 5 Prakash Babu B
Senior Grade Lecturer and Corresponding Author, 2 Associate Professor, 3Senior Grade
Lecturer,4Associate Professor, 5Additional Professor.
Department of Anatomy,Kasturba Medical College, Manipal University, Manipal. Karnataka State,
India.
Abstract
Extensor digitorum longus is one of the muscle of the anterior crural region of the leg, arises from the
upper part of the medial surface of the shaft of fibula, a small area of lateral tibial condyle, interosseous
membrane and anterior intermuscular septum of the leg. The tendon of the extensor digitorum longus
lies on the lower part of the tibia passes beneath the superior and inferior extensor retinaculum, finally
split into four digital slips and joins with the lateral three slips of extensor digitorum brevis to form the
dorsal digital expansion. Anterior tibial artery is the main artery of the anterior crural region which lies
between the extensor halluces longus and extensor digitorum longus in the lower third of the leg and
appears on the dorsum of the foot as dorsalis pedis artery.During routine dissection for undergraduate
medical students,in a middle aged male cadaver an additional tendon was observed in the extensor
digitorum longus and is attached to the middle of the shaft of the fifth metatarsal bone.Anterior tibial
artery lies lateral to the peroneus tertius muscle in the lower third of the leg, then it passes medially deep
to the peroneus tertius and extensor digitorum longus muscles. Lateral tarsal artery arises from the
dorsalis pedis artery and lies lateral to the deep peroneal nerve while the main trunk lies medial to the
nerve beneath the inferior extensor retinaculum of the lower limb. Awareness of presence of an
additional tendon in the dorsum of the foot and variation in the course of the anterior tibial artery is
crucial while treating the compartment syndrome.
Key Words: Extensor digitorum longus, anterior tibial artery, compartment syndrome
Introduction
The retinacula of the ankle are distinct structures defined as regions of localized thickening of the
superficial aponeurosis covering the deep structures of the distal portion of the leg, ankle, and foot.
These retinacula are sites of reinforcement of the superficial aponeurosis, maintaining approximation
of tendons to the underlying bone. The retinacula act as a pulley like mechanism that appears to
represent an adaptation of the body to provide both a smooth gliding surface and the mechanical strength
to prevent tendon bowstringing [1].
The superior extensor retinaculum is a transverse, roughly rectangular band located above the tibiotalar
joint. It attaches laterally on the lateral crest of the lower fibula and the lateral surface of the lateral
malleolus and medially on the anterior crest of the tibia and the medial malleolus. The structures that
pass deep in relation to this retinaculum include the tibialis anterior muscle, extensor hallucis
Longus muscle, anterior tibial blood vessels, deep peroneal nerve, extensor digitorum longus muscle,
and peroneus tertius muscle. [2].
Case Presentation
During routine dissection for undergraduate medical students in middle aged male cadaver, an additional
tendon was observed in the extensor digitorum longus and is attached to the middle of the shaft of the
fifth metatarsal bone. Anterior tibial artery lies lateral to the peroneus tertius muscle in the lower third of
the leg and deep to the superior extensor retinaculum, then it passes medially deep to the peroneus
tertius and extensor digitorum longus muscles. Lateral tarsal artery arises from the dorsalis pedis artery
and lies lateral to the deep peroneal nerve while the main trunk lies medial to the nerve beneath the
inferior extensor retinaculum of the lower limb. Arrangement of structures beneath the superior extensor
retinaculum also altered; from medio laterally these are tibialis anterior muscle, extensor hallucis
Longus muscle, deep peroneal nerve, extensor digitorum longus muscle, peroneus tertius muscle,
anterior tibial blood vessels.
Figure – Anterior view of the left leg
TA – tibialis anterior , EHL – extensor hallucis
Longus, DPA – dorsalis pedis artery, DPN– deep peroneal nerve,
EDL- extensor digitorum longus , ATA- anterior tibial artery, PT- peroneus tertius
Discussion
The extensor digitorum longus muscle frequently shows variation in the arrangement and insertion of its
tendons. It may give an additional slip to the base of the proximal phalanx of the second toe, the first
interosseous muscle and the anterior end of the fifth metatarsal bone. Sometimes, it may be connected to
the extensor hallucis longus by a slip, extensor digitorum brevis by a cross band and peroneus tertius by
a slip. Further, the digital tendon to each toe may be doubled or rarely tendon to the second and little
toes alone may be doubled. [3] Presence of an additional tendon in extensor digitorum longus muscle is
seldomly reported in the past and can be used for tendon transfer surgeries. Course of the anterior tibial
artery is deep to the peroneus tertius and extensor digitorum longus muscles. This may cause transient
compression of the anterior tibial artery leading to ischemia of the muscles of the anterior tibial
compartment of the leg causing anterior tibial compartment syndrome.
Conclusion
Knowledge of these variations is necessary for the surgeon to perform tendon transfer surgeries.
Furthermore, Knowledge of vascular anatomy of foot is essential for arterial reconstruction flap
surgeries of the foot. This can avoid amputation of foot in cases of arterial trauma like thromboangitis
obliterans, industrial automobile accidents, diabetes and severe ischaemia of lower limb. [4]
References
1.
Numkarunarunrote, N., Malik, A., Aguiar, RO., Trudell, DJ., Resnick, D,. (2007) ‘Retinacula of
the Foot and Ankle:MRI with Anatomic Correlation in Cadavers’. American Journal of
Roentgenology. Vol 188, pp 348-354.
2.
Sarrafian SK. Anatomy of the foot and ankle: descriptive, topographic, functional, 2nd ed.
(1993)Philadelphia, PA: Lippincott Williams & Wilkins,:113–158
3.
Jetti, R., Sirasanagandla, S R., Nayak, B S., Gorantla, V R., Shetty, A S,. (2014) ‘Higher division
of the extensor digitorum longus muscle: A cadaveric case report;. OA Case Reports Vol 25,
pp:12.
4.
Kulkarni, J., Paranjpe, V., Vatsalaswamy. (2012) ‘Anterior Tibial Artery Terminating as Tarsal
arteries). IOSR Journal of Dental and Medical Sciences (JDMS) Vol 1, Issue 2, PP 21-22
Declaration:
Authors declare that this Manuscript has not been published or submitted for publication
elsewhere.