Anterior & Lateral Compartments of the Leg PDF

Anterior & Lateral Compartments of the Leg Compartments of the Leg The leg is divided in to 3 compartments formed by intermuscular septa, interosseous membrane & the bones Ant...

Anterior & Lateral Compartments of the Leg Compartments of the Leg The leg is divided in to 3 compartments formed by intermuscular septa, interosseous membrane & the bones Anterior Compartment Lateral Compartment Posterior compartment Deep & superficial The muscles of each compartment share common functions & innervations Nerves supply of leg – From Sciatic Nerve Tibial nerve (purple) Posterior compartment of leg & sole of foot Common Peroneal divides in to a superficial & deep branch Superficial Peroneal (blue) Lateral Compartment Deep Peroneal (green) Anterior compartment Nerves supply of leg – From Sciatic Nerve Common Peroneal divides in to a superficial & deep branch Superficial Peroneal (blue) Lateral Compartment Deep Peroneal (green) Anterior compartment Muscles of Anterior Compartment Key principles Pass over the ankle joint therefore are dorsiflexors The long extensors pass along the dorsal aspect of the digits therefore extensors of the toes Deep peroneal nerve dorsiflexors & toe extensors Muscles of Anterior Compartment 4 Muscles Tibialis Anterior Extensor Hallicis Longus Extensor Digitorum Longus Peroneous (Fibularis) Longus If you kick something it goes THuD (Med to Lat) Tibialis Anterior Origin: Lateral condyle & superior half of lateral tibia & Interosseous membrane Inserts: Medial & Inferior surface of medial cuneiform & 1st metatarsal Action: Dorsiflexion (& inverts foot) Extensor Hallicis Longus Origin: Middle part of anterior surface of fibula & Interosseous membrane Inserts: Dorsal aspect of base of distal phalanx of great toe Action: Extends Great Toe (helps dorsiflexion of ankle) Extensor Digitorum Longus Origin: Lateral condyle of tibial & superior ¾ of medial surface of fibula and interosseous membrane Inserts: Middle & Distal phalanges of lateral 4 digits (extensor expansion) Action: Extends lateral 4 digits (helps dorsiflexion of ankle) Peroneous tertius Is a separated part of Extensor Digitorum Longus Shares it’s origin (more distal fibres along fibula) Inserts 5th metatarsal (not a phalanx) It is quite often absent (and not missed) Extensor Retinacula The deep fascia of the leg is called crural fascia 2 thickenings bind the tendons of the muscles before and after the ankle joint Extensor Retinacula Superior extensor retinaculum – strong, broad band of deep fascia Inferior extensor retinaculum – Y-shaped band of deep fascia Note the Extensor expansion Nerves supply of leg – From Sciatic Nerve Common Peroneal divides in to a superficial & deep branch Superficial Peroneal (blue) Lateral Compartment Deep Peroneal (green) Anterior compartment Muscles of Lateral Compartment Key principles Pass lateral to the ankle so will pull the foot out (Eversion) Superficial Peroneal Nerve Everts the foot Evertor compartment! Peroneus Longus Origin: Head & superior 2/3rds of lateral fibula Inserts: Base of 1st Metatarsal and Medial cuneiform Most Superficial! Pass posterior to the lateral malleolus (using it as a pulley) Enters a grove on the anterior inferior aspect of the cuboid bone and runs obliquely & distally to its attachment Like a Stirrup! Peroneus Brevis Origin: Inferior 2/3rds of lateral fibula Inserts: Dorsal tuberosity of lateral side of base of 5th tuberosity Deeper of the two muscles Passes behind lateral malleolus (using it as a pulley) Works with the longus to evert foot (help prevent excessive inversion) Dorsum of Foot Two muscles on the dorsum of the foot Extensor Digitorum Brevis Extensor Hallucis Brevis Originate from calcaneus Attach into extensor expansion and aid the long muscles in extending the digits Blood supply – Anterior Compartment Anterior Tibial Artery supplies the anterior compartment A branch of the popliteal artery it passes anteriorly through a gap in the interosseous membrane and descends (Joined by the deep peroneal nerve) Note: The neurovascular bundle Nerve & Blood Vessels have different Blood supply – Anterior Compartment For dissection: In the Leg, this NVB can be identified deep between the Tibialis anterior and Extensor Hallucis Longus Blood supply – Lateral compartment The lateral compartment does not have it’s own blood supply Perforating arteries supply this compartment Proximally – perforating arteries of anterior tibial artery Distally – perforating arteries of peroneal (fibular) artery Dorsum of Foot – Blood supply At the ankle joint the Anterior Tibial Artery changes name becoming the Dorsalis Pedis muscle The Extensor Hallucis Longus tendon crosses it On the dorsum of the foot the Dorsalis Pedis is located between Extensor Hallucis Longus and The Extensor Digitorum Longus Tendons Dorsum of Foot – Blood supply Dorsalis Pedis passes in to the first interosseous space and divides into the deep planter artery & 1st dorsal metatarsal artery Deep Planter artery anastomoses with lateral plantar artery to form deep planter arch Dorsum of Foot – Blood supply Dorsalis pedis gives off 2 branches Lateral tarsal artery Arcuate artery They anastomose to form an arterial loop These give off the metatarsal arteries Which further divide to give off dorsal digital arteries Dorsum of Foot – Blood supply The metatarsal arteries are also connected to the planter arch & plantar metatarsal arteries via perforating arteries This arch is usually hidden under Extensor digitorum brevis Dissection time Remove the skin over the leg Identify the muscles in anterior & Lateral Compartments Try to find the NVB Continue dissection over dorsum of foot Try to find dorsalis pedis