Nerve injury is one of the most serious and frequent complications of acute or gradual deformity correction or limb lengthening.1-12 Nerves cross fascial tissues and septae that usually do not stretch as other connective tissues do, resulting in entrapment and nerve compromise.

The peroneal nerve is the nerve most frequently injured in the proximal leg, close to the neck of the fibula. It can be easily decompressed by a simple surgery that includes release in two fascial tunnels in the proximal part of the leg: the superficial and deep fascia of the peroneal longus muscle and the anterior intermuscular septum of the leg.


Peroneal nerve decompression is a well recognized technique for the treatment of peroneal nerve palsy and entrapment.7,13 Indications include:

  • Acute trauma
  • Acute deformity correction
  • Signs and symptoms of nerve compromise during lengthening
  • Valgus correction or extension corrections: acute corrections over 5 degrees and gradual corrections over 15 degrees

Nerve decompression is usually an elective procedure, especially when it is done prophylactically before an osteotomy or acute deformity correction.


The primary entrapment described is at the neck of the fibula. The first entrapment tunnel is located at the fascial arcade of the peroneal muscles over the common peroneal nerve. After passing under the fascial arcade, the common peroneal nerve splits in the lateral compartment into superficial and deep branches. The superficial branch continues unimpeded through the lateral compartment, while the deep branch passes under the anterior intermuscular septum (second tunnel) between the lateral and anterior compartments to enter the anterior compartment of the leg. The anterior intermuscular septum extends from the anterior fascia covering the anterior and lateral compartments to the interosseous membrane between the tibia and the fibula at its deepest extent.

Preoperative Planning

Record in detail the results of the neurologic examination, including its motor and sensitive components. Assess neuosensory status with neuroconductive studies and the Pressure Specified Sensory Device. These data will be important in verifying changes following the procedure.

In a thin patient, palpate the common peroneal nerve subcutaneously. This orients the direction of the incision. A tourniquet could be helpful for careful dissection.

Avoid using an anesthesic block, which would not allow for adequate intra-operative control of nerve protection if there were nerve stimulation by dissection, or if a nerve stimulator were used for testing before and after decompression. Muscle relaxants are avoided for the same reason.


The patient is positioned supine, with a bump under the affected side. The leg is flexed to relax the posterior thigh and the common peroneal nerve.


Paley14 has identified two sites of entrapment and described a surgical technique to decompress both fascial tunnels.

  • Surgery can be performed with or without a tourniquet, but preferably with the patient not relaxed (use of fast-acting curare in induction and intubation) to allow observation of the foot while dissecting close to the nerve.
  • Make a 3- to 5-cm incision, ensuring that the extension is long enough to expose the entrance of the peroneal nerve into the first tunnel under the peroneous longus muscle. This is an oblique incision, and in thinner patients, it is possible to palpate the nerve about 1 cm below the fibular head. The incision must be in line with the nerve. Correct incision placement makes the decompression simple and objective.
  • Retract the skin and subcutaneous tissues, and then incise and retract the superficial fascia of the leg. At this point the common peroneal nerve is easily palpated. Isolate the common peroneal nerve and follow it into its entrance behind the peroneus longus muscle. This muscle usually has a thick fascia that should be transected in the same direction as the nerve superficially, keeping the peroneal nerve protected and under direct vision (Figure 1).

Figure 1. A short oblique skin incision is made in the same direction as the nerve. The superficial peroneal fascia is divided outside of the peroneal muscles, and the common peroneal nerve is identified. The peroneal muscle fascia is cut. The underlying peroneal muscles are retracted medially, exposing the deep peroneal muscle fascia, which is then divided.

  • The peroneal muscle belly should be kept intact. Retract the muscle belly medially and transect the deep peroneus longus fascia, freeing the nerve underneath. In most cases, it is now possible to see the common peroneal nerve dividing into deep and superficial branches, the superficial running down in the lateral compartment and the deep branch going in the direction of the anterior compartment of the leg.
  • Retract the peroneus longus muscle from medial to lateral and isolate the anterior intermuscular septum, which divides the peroneus longus muscle (lateral compartment of the leg) from the extensor digitorum longus muscle(anterior compartment of the leg). Ensure that  both sides of the anterior intermuscular septum are well isolated and then transect the septum horizontally, under direct vision. Use caution to avoid transecting the deep branch of the peroneus nerve that should be crossing the septum at this point. It is very important to completely transect this septum to allow the deep peroneus nerve to completely decompress (Figure 2).

Figure 2. The transverse fascial incision is extended towards the tibia, crossing the intermuscular septum between the anterior and lateral compartments of the leg. The muscle on either side is retracted, and the septum is transected under direct vision. The deep peroneal nerve passes under this septum but is not visualized.

  • The procedure is then completed. Closure should address subcutaneous tissue and skin.


  • Nerve injury
  • Infection
  • Hematoma

Postoperative Care and Outcome

Dressings are applied and changed every 3 days. Assess neurologic status just after the end of procedure, with the patient still in the recovery room – some post-decompression findings can be immediately detected. Improvement in pain is usually the first effect of decompression, followed by sensory and motor function.

Improvement in the patient’s condition can usually be observed in 2 to 6 months after surgery. The greatest level of improvement occurs when nerve decompression is performed as soon as possible after the first symptoms and signs of nerve compromise are detected.


Nogueira et al 15 found that peroneal nerve decompression is efficacious for the treatment of peroneal nerve injury secondary to acute and gradual deformity correction and lengthening. Nerve stretch injuries are caused when distraction overcomes the nerve fibers’ elastic and plastic properties.

These injuries have been the subject of many studies.16-18 It has been assumed that nerve injury resulting from limb lengthening and from acute valgus to varus deformity correction is a stretch injury. When nerve decompression was performed on patients undergoing limb lengthening, intraoperative findings included hemorrhage, nerve flattening, narrowing of the nerve at the entrance of the fascial tunnel, and reduction of the perineural vascularization at the site of compression. These findings are typical of nerve entrapment and not of stretch injury.15

Paley and Herzenberg14,15 used peroneal nerve decompression both prophylactically and therapeutically when performing acute valgus to varus deformity corrections around the knee. Intraoperative potential nerve monitoring was used in some cases, and a sudden loss of nerve potentials was observed minutes after acute valgus to varus correction. Immediate decompression of the nerve leads to restoration of normal potentials.

Nogueira et al 15 documented that when peroneal nerve injuries are caused by limb lengthening, acute deformity correction, or gradual deformity correction, the timing of decompression affected the rate of nerve recovery. Early decompression resulted in patients experiencing an early recovery; late decompression resulted in patients experiencing a late recovery.15 However, this study failed to find a relationship between nerve injury and the amount or percent of lengthening, suggesting again that entrapment and not stretch injury is the cause.

Nerve entrapment might also be a factor when stretch, acute trauma, or compression injury occurs. Injury leads to inflammation. The peroneal tunnels are normally very tight, leaving little space to accommodate additional swelling. Consequently, a secondary injury might follow the original stretch injury when the nerve swells against the nonexpandable walls of the peroneal tunnels. Prophylactic or therapeutic decompression is the standard of care for the median nerve of the hand. The carpal tunnel is much more capacious than the peroneal tunnels. Prophylactic or therapeutic nerve decompression within 24 hours should also become the standard of care for the peroneal nerve. If tension can precipitate entrapment, then decompression should be able to reduce the tension on the peroneal nerve.

A cadaver study 19 demonstrated that the two fascial tunnels described above are important points of entrapment of the peroneal nerve. Nerve tension increases after varus osteotomy and decreases after peroneal nerve decompression, returning to the initial normal levels.

These studies indicate that early decompression is warranted while the initial injury is recoverable; the secondary injury might make the situation irrecoverable.


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