Download www.apjor.com Page 26 MUSCULAR VARIATION ON THE

Asia Pacific Journal of Research
Vol: I. Issue XXV, March 2015
ISSN: 2320-5504, E-ISSN-2347-4793
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
1
1
Huban Thomas. R*,2Prasanna, LC,3Suhani S, 4Sneha G, 5PrakashBabu B
Senior Grade Lecturer and Corresponding Author, 2 Associate Professor, 3Senior Grade Lecturer,4
Associate 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 theextensor digitorum longusand 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
www.apjor.com
Page 26
Asia Pacific Journal of Research
Vol: I. Issue XXV, March 2015
ISSN: 2320-5504, E-ISSN-2347-4793
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 pulleylike 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 dorsalispedis 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
digitorumlongus muscle, peroneus tertius muscle, anterior tibial blood vessels.
Figure – Anterior view of the left leg
TA – tibialisanterior , EHL – extensor hallucis
Longus, DPA – dorsalispedis artery, DPN– deep peroneal nerve,
EDL- extensor digitorumlongus , ATA- anterior tibial artery, PT- peroneus tertius
www.apjor.com
Page 27
Asia Pacific Journal of Research
Vol: I. Issue XXV, March 2015
ISSN: 2320-5504, E-ISSN-2347-4793
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 hallucislongus by a slip, extensor digitorumbrev is 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 digitorumlongus muscle is seldomly reported in
the past andcan 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 anteriortibial 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 thromboangitisobliterans, 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
www.apjor.com
Page 28