Peroneal Nerve:From: www.wheelessonline.com - See:
- Innerv. Musc. Lower Limb
- Innervation of the Leg and Foot:
- Anatomy:
- common peroneal nerve is derived from (L4, L5, S1, S2) as a part of the sciatic nerve;
- posterior component, supplies short head of biceps femoris in thigh, crosses posterior to lateral
head of gastrocnemius, and becomes subcutaneous behind head of fibula;
- it penetrates the posterior intermuscular septum, and becomes closely opposed to the periosteum of the proximal fibula;
- it then divides into superficial & deep peroneal nerves;
- the nerve also gives off a lateral sural cutaneous brach which joins with the the medial sural cutaneous
nerve (from tibial nerve) to form the sural nerve;
- superficial peroneal nerve:
- supplies lateral compartment of leg, first passing between peroneus longus
- passes in a straight line from the common peroneal nerve;
- along the length of the proximal one third of the fibula, the superficial peroneal nerve is on the lateral cortex of the fibula;
- passes between peroneus longus & peroneus brevis;
- superficial sensory nerves:
- subcutaneous superficial sensory branch lies between peroneus brevis and EDL msucles.
- superficial peroneal nerve is accompanied by a true vascular axis that is supplied by tibialis anterior artery along its course.
- about 10-12 cm above the tip of the lateral malleolus, the superficial peroneal nerve pierces the fascia;
- about 6-7 cm distal to the fibula, the superficial peroneal nerve bifurcates into intermediate and medial dorsal cutaneous nerves;
- location of cutaneous nerves: (from Huene and Bunnell 1995)
- branches of the superficial peroneal nerve or the sural nerve may be injured during ORIF of Ankle frx;
- these nerves are most at risk at the junction of the distal and middle thirds of the lateral border of the fibula;
- in 22% of legs, braches of either nerve will cross the frx site;
- in 54% of legs, branches of superficial peroneal will lie within 5 mm of the anterolateral border of the fibula;
- safest interval is 12 mm posterior to the anterolateral border of the fibula at 10 cm from the
fibular tip, and 10 mm posterior to the anterolateral border at 5 cm proximal to the tip;
- references:
- Surgical anatomy of the superficial peroneal nerve in the ankle and foot.
- Anatomical variations in the course of the superficial peroneal nerve.
- Operative anatomy of nerves encountered in the lateral approach to the distal part of the fibula.
- Anatomic relations between ankle arthroscopic portal sites and the superficial peroneal and saphenous nerves.
A. Saito MD and S. Kikuchi. Foot and Ankle International. Vol 19. No 11. Nov 1998. p 748.
- Operative Anatomy of Nerves Encountered in the Lateral Approach to the Distal Part of the Fibula.
D.B. Huene MD, and W.P. Bunnell MD. JBJS Vol 77-A. No 7. Jul 1995.
- deep peroneal nerve:
- courses anteriorly around fibula, taking a sharp turn as it rounds the fibular neck, to enter anterior compartment of leg;
- because of the sharp turn, the nerve is more tethered than the superficial branch;
- immediately below the fibular head, the deep peroneal nerve lies on the anterior cortex of the fibula for a distance of 3-4 cm;
- the nerve passes under the intermuscular septum (between lateral and anterior compartments) which is a point of entrapment;
- note that when this septum is pulled taunt, it compresses the deep peroneal nerve w/o affecting the superficial nerve;
- it supplies anterior compartment muscles as it travels w/ the the anterior tibial artery, lying between the tibialis anterior and the EHL;
- it passes underneath the extensor retinaculum, sends a motor branch to the EDB,
and finally sends a sensory branch to the interspace between the first and second toes;
- references:
- Palsy of the deep peroneal nerve after proximal tibial osteotomy. An anatomical study.
- Relationship of the common peroneal nerve and its branches to the head and neck of the fibula.
- Peroneal Nerve Palsy:
- peroneal palsy following TKR
- nerve injury
- discussion:
- peroneal nerve palsy may lead to severe disability w/ foot drop and paresthesias;
- note that in contrast to other types of nerve palsies, peroneal palsy may demonstrate a greater motor deficit (than sensory
deficit) because the deep motor brach is subject to tethering a two points: the fibular neck and the intermuscular septum;
- traumatic peroneal palsy: may result from supracondylar frx, knee dislocation, and proximal tibial frx;
- atraumatic peroneal nerve palsy:
- may result from a large fabella which impinges on peroneal nerve behind the
knee or may result from a proximal tibiofibular synovial cyst (which is identifed by MRI);
- these patients will often have a history of lumber disc disease, ETOH use, and diabetes.
- references:
- Unusual manifestations of proximal tibiofibular joint synovial cysts. TA Damron, MG Rock. Orthopedics. Vol 20, 1997. p 225-230.
- exam:
- always consider lumbar radiculopathy during the examination;
- there may be an obvious foot drop;
- sensory loss may be difficult to determine because of variable & small autonomous zone of sensation;
- Tinel's sign over the fibular neck, helps localize the site of nerve compression;
- always check for a fabella and check to see if direct compression reproduces nerve symptoms;
- in cases of knee dislocation it is important to test for function of the tibial branch of the sciatic nerve as well;
- in some cases of peroneal nerve avulsion, there will also be a sciatic nerve traction injury;
- EMG:
- useful to objectively document the conduction block;
- if possible should be performed w/ in one month of injury;
- amplitude of the sensory potential and decreases in nerve conduction velocities are used to
confirm sensory and motor deficits, respectively;
- prognosis;
- w/ partial nerve palsy, > 80% will recover completely;
- w/ complete palsy, < 40% will have complete recovery;
- peroneal nerve in continuity which arises from a well defined etiology will tend to do better than
nerve palsies arising from idiopathic causes;
- treatment:
- if there is no neurologic improvement after 2-3 months, then operative decompression is indicated;
- nerve in continuity:
- operative treatment invovles external neurolysis of peroneal nerve at the level of the fibular head;
- the nerve and its branches need to be freed from its adherence to the proximal fibula, particularly at its most proximal
4 cm as well as a 2nd region of adherence which may lie between 7 and 15 cm from the fibular head;
- the nerve may be entrapped by thick fibrous bands which arch over the nerve as it crosses the fibular neck;
- the arch has a superficial band and a deep band;
- nerve not in continuity: (neurotomesis)
- see nerve repair
- one of the problems encountered in peroneal nerve repair following knee dislocations
(or other injuries) is that the location of the nerve injury may be well above the knee joint;
- in the case of knee dislocation, there may be concomitant tibial nerve division palsy;
- references:
- Nerve grafting for traction injuries of the common peroneal nerve. A report of 17 cases.
- Nerve grafting for traction injuries of the common peroneal nerve. A report of 17 cases.
- The operative treatment of peroneal nerve palsy. MA Mont et al. JBJS Vol 78-A. 1996. p 863-869.
- Decompression of the common peroneal nerve: experience with 20 consecutive cases.
- Fibular fibrous arch. Anatomical considerations in fibular tunnel syndrome.
H Goobe and D Chain. Acta Anat. Vol 85. 1973. p 84-87.
- Anatomic variations related to decompression of the common peroneal nerve at the fibular head.
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