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Peroneal Nerve exploration and decompression

    Overview

    Learn the Peroneal Nerve exploration and decompression surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Peroneal Nerve exploration and decompression surgical procedure.
    The common peroneal nerve is vulnerable to entrapment at the peroneal tunnel as it crosses the fibular neck. There are a number of local structures that may be contributing to compression of this nerve and this guide will demonstrate how to deal with each of these in turn. Extrinsic compression may also result from a lesion such as a ganglion. The nerve may also require exploration in this region following trauma about the knee, either direct trauma associated with fracture of the proximal fibula or indirect traction trauma associated with multiligamentous knee dislocation. The peroneal nerve is prone to injury due to the relative tethering of the deep peroneal nerve as it traverses the septum between lateral and anterior compartments of the lower leg.
    Common peroneal nerve entrapment may result in weakness of the anterior or peroneal muscle groups or pain, parasthaesia and numbness in the cutaneous territories of the deep or superficial peroneal nerves.
    Entrapment of this nerve may have a variety of causes including local trauma or surgery around the knee. In our experience a great many cases result from a nerve that is recovering from a previous peroneal or sciatic level injury and undergoes ‘auto-entrapment’ in this narrow region, as it increases in volume during the recovery phase.
    Releasing the nerve in these cases can be rewarding. An immediate improvement in function is occasionally seen, but in more significant lesions to the nerve that may involve demyelination or axonopathy a longer time course for recovery should be expected. For a non-recovering nerve lesion, consideration must be given to reconstructive procedures such as tendon or nerve transfers.


    Indications

    Indication:
    In this case a young man had sustained an axonal injury to the sciatic nerve in the thigh that had initially been recovering over the expected timescale. Although recovery within the tibial nerve territory was excellent, the common peroneal nerve demonstrated very limited recovery.
    Symptoms and examination findings:
    The patient complained of paraesthesia within the deep and superficial peroneal nerve territories and had absent tibialis anterior function and very weak peroneus longus function.
    Additionally there was a very strong Tinel-Hoffman sign at the fibular neck indicating entrapment at this level.
    Investigations:
    In this situation electromyography and nerve conduction studies were a useful adjunct to decision making although this was largely made on clinical grounds.
    Further recovery into the common peroneal nerve did not occur according to the expected timescale and therefore decompressive surgery was indicated.
    Imaging of the nerve was not indicated in this case, however ultrasound or MRI may provide useful information on entrapment points, nerve continuity, extrinsic compressive lesions such as ganglia from the proximal tibiofibular joint or intrinsic nerve lessions such as peripheral nerve sheath tumours.
    Non-operative management:
    Following an acute injury elevation of the limb and symptomatic treatment with rest and ice may help reduce swelling and improve nerve function. If there is neuropathic pain, urgent surgery is warranted to prevent further deterioration in nerve function and axon death. There is no role for non-operative management of a neurophysiologically-proven compressive nerve lesion at the peroneal tunnel with motor weakness or paralysis.
    Alternative operative management and contraindications:
    Other indications for exploring this nerve include an acute nerve injury to the peroneal nerve at this level that is felt to be a Sunderland grade 3 or higher.
    A lower grade of nerve injury also requires exploration if it fails to recover in the expected timeframe, becomes worse under observation, requires decompression (as above) or if there is felt to be any doubt over the diagnosis.

    Setup

    We perform this procedure under general anaethesia without a tourniquet. We use an intra-operative nerve stimulator to aid identification and to guide the extent of decompression and provide some prognostic information.
    For some patients a thigh tourniquet may be placed and inflated intra-operatively if required. In most patients visualisation is adequate and a tourniquet may of course interfere with intraoperative nerve stimulation.
    The patient is positioned supine with a sandbag under the ipsilateral buttock and a pillow under the knee to flex the knee to 45 degrees.
    The foot and leg and lower thigh are prepped and draped.

    Operation

    Leaving the foot exposed allows identification of specific motor branches under nerve stimulation.
    Important surface landmarks are as follows
    A – Patella
    B – Lateral femoral condyle
    C- Fibula head
    D – Peroneus longus tendon
    E – Lateral malleolus

    The incision is marked once the knee is at 45 degrees of flexion. This is in line with the nerve as it crosses the neck of the fibula and is therefore may be extended as required to increase exposure of the nerve proximally and distally.

    A – Head of fibula

    An approach is made through the skin and fat ensuring that complete haemostasis is achieved at each layer. Sharp dissection is preferred using a blade or a monopolar diathermy.

    Dissecting scissors are used to carefully dissect through the fat.
    The lateral sural nerve branch towards the posterior aspect of the incision must be protected if seen.

    A small split in the fascia, posterior to the fibula reveals a several fasicial layers beneath. Once divided these will reveal some fat and it is here that the common peroneal nerve should be initially found.
    In a slim person one can palpate the nerve as one progresses to ensure the approach is not veering away from the nerve
    An prominent epineurial vessel seen within th efatty layer often heralds the appearance of the nerve.

    Once the nerve is identified, further dissection will allow a sloop to be placed around it. This can be one with the aid of a pair of Mixter forceps. One must proceed with great care until the nerve is adequately exposed and its exact location and anatomy defined to avoid inadvertent injury.
    The sloop allows identification and safe manipulation of the nerve with minimal handling and allows gentle traction to be exerted whilst dissecting further.
    When placing or resiting retractors around exposed nerves great care must be taken to avoid injuring exposed nerves.

    The fascia overlying Peroneus longus, is now divided sharply in the line of the nerve, exposing the individual muscle compartments and the intermuscular sepatae between them.
    Identification of the leading edge of peroneus longus reveals the posterior crural intermuscular septum which crosses the nerve often causing a tight compression effect as the it is pinched between this band and the fascial bands deep to the nerve at this level. Both must be divided under direct vision taking care to protect the nerve throughout.

    As the peroneus longus muscle belly if retracted anteriorly, the posterior crural intermuscular septum is divided completely.

    Before decompressing further, nerve stimulation should be used to establish baseline stimulation thresholds and identify all key motor components of the nerve that are functioning. Further stimulation after complete decompression may then give an early indication about whether the conduction through the nerve has improved.
    In this case there was some stimulation within the superficial peroneal component at a threshold of 2mA (higher than normal) and only some weak EHL function in the deep peroneal at the even higher threshold of 4mA.
    Some knowledge of the topographical organisation of fascicles within the nerve may be useful in certain situations in particular for nerve reconstruction. The central component contains sensory fibres wch are sandwiched between deep peroneal fibres proximally and superficial peroneal fibres in the distal aspect.

    Next the peroneus longus muscle in retracted posteriorly to expose the anterior crural intermuscular septum between peroneus longus and extensor digitorum longus. Again this is to be divided releasing a further compression point over the nerve as it crosses.

    The final septum lies between extensor digitorum longus and tibialis anterior. An assistant is required to provide adequate retraction of the muscle bellies whilst each of these septae undergoes division.

    The decompression is almost complete.
    One must now look deep to the nerve as it sits much more freely at this stage. Any tight fascial band causing compression or kinking can be divided under direct vision whilst protecting the nerve.

    One may now identify each component of the common peroneal nerve as it splits into it’s various branchces at this level. Here a blue sloop has been placed around the superficial peroneal nerve and a Mixter is being guided around the deep peroneal nerve in order to pass a sloop around it.

    The branches have all been slooped and are stimulated once more
    A – Common peroneal nerve
    B – Tibialis anterior and articular branch
    C – Deep Peroneal nerve
    D – Superficial peroneal nerve

    Any remaining deep fascial bands can be excised

    The anterior most fibres of soleus can be recessed over 1-2cm just behind the nerve if this muscle is prominent and and felt to be contributing to a tight space for the nerve.

    Careful haemostasis is important. The wound is irrigated. A drain is not usually required.

    A layered closure is performed. this can be supported with steristrips and a non adherent dressing followed by soft bandage such as wool and crepe.

    Post Operative

    The patient is discharged home later the same day or the following morning once pain is controlled and safe mobilisation has been confirmed.
    Full weight bearing is permitted immediately. Some patients may require the use of a walking aid but this is not essential.
    The patient is advised to mobilise as pain allows and to keep the leg elevated when at rest. Oral analgesia is prescribed.
    The wound is routinely checked in clinic at 1 week following surgery. Sutures are trimmed or removed if required at 2 weeks.
    There may be some immediate relief of nerve pain and possible improvement in motor or sensory function. Often a further improvement is seen at about 3 months following surgery as re-myelination occurs. There is often a slower element of recovery that may be seen as axonal regrowth occurs.
    Signs to look for that suggest ongoing improvement is a distally migrating Tinel-Hoffman sign and sequentially improving sensory and motor function.

    Recommended Reading

    A number of series evaluating outcomes following common peroneal nerve decompression suggest that outcomes.
    1. J Neurosurg. 2007 Aug;107(2):314-8.
    Humphrey’s et al published a series of fifty one patients. 83% of those with motor dysfunction improved. 84% of those with pain improved and 49% of those with sensory disturbance improved.
    Numerous other series with smaller cohorts show satisfactory results.
    2. ANZ J Surg. 2011 Oct;81(10):707-12.
    3. Orthop Traumatol Surg Res. 2013 Oct;99(6):719-22. doi: 10.1016/j.otsr.2013.05.004. Epub 2013 Aug 27.

    Reference

    • orthoracle.com

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