Working Diagnosis:
Common peroneal nerve injury secondary to a stretching mechanism.

Treatment:
Initially held out of all activities and NWB on crutches, to be advanced to WB in boot as tolerated
Regular use of ice and NSAIDs prn for pain.
Gentle rehab guided by degree of nerve function. Reevaluation every 2-3 weeks initially.
EMG/NCS if symptoms persist more than 4-6 weeks without improvement or if develops evidence concerning for entrapment

Outcome:
At week 2, the patient was able to walk in a boot without pain.
Active ankle dorsiflexion and great toe extension slightly past neutral w/o pain and full active eversion w/o pain, 4+/5 ankle dorsiflexion; 5-/5 eversion and 3+/5 great toe extension. Dysesthesia still noted.
Advised to start gentle ROM and to slowly progress to strengthening

At week 4, full active ankle dorsiflexion and eversion; Full great toe extension
Still with strength deficit 4-/5 of EHL and 5-/5 of peronei as well as some dysesthesia, on anterior ankle along dorsal foot to 1st web space. Able to walk in boot without pain.
Recommended weaning out of boot into lace-up brace and continue with rehab and progress as tolerated

At week 7, there was subtle abnormal gait w/o pain.
There was persistent tenderness of palpation around the fibular head.
There was full active dorsiflexion and eversion of the ankle w/o pain with 5/5 resisted strength as well as full great toe extension with 4/5 resisted strength.
There was some residual paresthesia on both dorsum of the foot and 1st web space.
At this point we recommended continuing to progress rehab based on degree of nerve function. Since he was improving, we monitored his response over the next 3-4 weeks.

At week 11, there was full strength and full pain free active ROM with slight deficits with proprioception/balance and small area of dysesthesia on dorsum of great toe only.
We recommended rehab emphasizing strength, proprioception and began a gradual activity progression program that must be completed without issues before he can be cleared.

Author's Comments:
Axonal regeneration initiates around 4-6 weeks and continues at a rate of approximately 1 mm/d or 1 inch/month. At that rate, it can take up to 9-12 months for patients to fully recover from nerve injuries, if EMG/NCS were consistent with signs of regeneration.

If recovery is slow, EMG/NCS can be obtained 3-4 weeks post injury to evaluate extent of nerve injury.

If recovery is still concerning by the next 2-4 weeks after the electro- diagnostic tests, consider MRI to evaluate for entrapment.

If MRI is consistent with entrapment or complete transection of the nerve, surgery is indicated to avoid axon demyelination and irreversible fibrosis in denervated muscles.

Editor's Comments:
The anatomic location of the common peroneal (fibular) nerve exposes it to potential for injury, especially during sports competition. Being very superficial, it is vulnerable to taking a direct blow. Its orientation about the fibular head also makes it vulnerable to injury during twisting of the knee or ankle. A stretch injury causing a neurapraxia of the common peroneal nerve will manifest as loss of function of both the deep and superficial peroneal nerves, as these branch from the common peroneal. Myelin repair is slow, however, if progress is not seen, it is important to reconsider the diagnosis and further investigate either with electromyography and nerve conduction study, an MRI or both. Return to play should be based on recovery of motor function, strength, range of motion, and ability to perform desired athletic tasks.

References:
1 Evaluation and treatment of peroneal neuropathy
Jennifer Baima and Lisa Krivickas,
Author information ► Copyright and License information ►

2 Nerve injury and grades II and III ankle sprains.
Nitz AJ, Dobner JJ, Kersey D.
Am J Sports Med. 1985 May-Jun;13(3):177-82.

3 Nerve entrapments of the lower leg, ankle and foot in sport.
McCrory P, Bell S, Bradshaw C.
Sports Med. 2002;32(6):371-91.

4 Delayed Onset of Peroneal Neuropathy after Minor Ankle Torsion in a 9-Year-Old Boy.
Wang JC, Chan RC, Yang TF
J Child Neurol. 2013 Feb 21;29(6):843-845.

5 Common peroneal nerve palsy after grade I inversion ankle sprain.
Mitsiokapa EA, Mavrogenis AF, Antonopoulos D, Tzanos G, Papagelopoulos PJ.
J Surg Orthop Adv. 2012 Winter;21(4):261-5.

6 Interosseous membrane: The anatomic basis for combined ankle and common fibular (peroneal) nerve injuries.
Lalezari S, Amrami KK, Tubbs RS, Spinner RJ.
Clin Anat. 2012 Apr;25(3):401-6. doi: 10.1002/ca.21227. Epub 2011 Aug 30.

7 Electromyography and Nerve Conduction Studies
Author: Stephen Kishner, MD, MHA; Chief Editor: Jonathan P Miller, MD


8 Clinics in neurology and neurosurgery of sport: peripheral nerve injury
Davis G, Kline DG, Spinner RJ, Zager EL, Garberina MJ, Williams GR, McCrory P.
Br J Sports Med. 2009 Jul;43(7):537-40. doi: 10.1136/bjsm.2008.048231. Epub 2008 Jun 14.

9 Peroneal nerve injury associated with sports-related knee injury.
Cho D, Saetia K, Lee S, Kline DG, Kim DH.
Neurosurg Focus. 2011 Nov;31(5):E11. doi: 10.3171/2011.9.FOCUS11187.

10 Surgical treatment of peroneal nerve palsy after knee dislocation.
Giuseffi SA, Bishop AT, Shin AY, Dahm DL, Stuart MJ, Levy BA.
Knee Surg Sports Traumatol Arthrosc. 2010 Nov;18(11):1583-6. doi: 10.1007/s00167-010-1204-3. Epub 2010 Jul 17. Review. Erratum in: Knee Surg Sports Traumatol Arthrosc. 2010 Nov;18(11):1626.

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