SLR - October 2015 - Brandon L. Tucker

Natural History of Sensory Nerve Recovery After Cutaneous Nerve Injury Following Foot and Ankle Surgery

Reference: Bai L, Han Y, Zhang WT, Huang W, Zhang HL. Natural History of Sensory Nerve Recovery After Cutaneous Nerve Injury Following Foot and Ankle Surgery. Neural Regen Res. 2015 Jan;10(1):99-103.

Scientific Literature Review

Reviewed By: Brandon L. Tucker, DPM
Residency Program: University Hospital, Newark, NJ

Podiatric Relevance: One of the most common complications following foot and ankle surgery is cutaneous nerve injury. However, the clinical treatment and recovery of cutaneous nerve injuries around the foot and ankle are often ignored. Cutaneous nerve injuries may lead to sensory abnormalities that may impact the patient’s quality of life and lead to an unsatisfactory outcome. The presented article aims to establish the pattern of recovery of cutaneous nerves after iatrogenic injury.

Methods: A total of 279 patients underwent ankle surgery between August 2012 and July 2013. Of those, 23 were diagnosed with cutaneous nerve injury of the ankle. After data collection, 17 patients were utilized for this study. This included 13 men and 4 women with an average age of 33.6 (25-61) years. There were seven cases of sural nerve injury, five with superficial peroneal nerve injury, and five with saphenous nerve injury. After the definitive diagnosis of cutaneous nerve injury was made, the patients received oral Vitamin B12 2micrograms twice daily and oral Methylcobalamin 0.5 mg daily for one month. The Medical Research Council Scale was used to assess nerve sensory function in consecutive follow-up of patients. Follow up was immediately after surgery, at six weeks, three, six, and nine months, and one year after surgery. Sensory function was determined utilizing hot and cold sensation and both static and movable two-point discrimination tests (S2PD and M2PD respectively). The Medical Research Council Scale classifies nerve function into five levels, S0-S4. S0 is a loss of single sensory innervation zone; S1, recovery of deep single sensory innervation zone; S2, certain recovery of pain and touch senses in the single superficial sensory innervation zone; S3, recovery of pain and touch senses in the single superficial sensory innervation zones and disappearance of hypersensitivity, S2PD >15mm, M2PD >8mm; S3+, further recovery with S2PD 6-15mm, M2D 4-8mm; and S4, complete recovery demonstrated by S2PD being 2-3mm and M2PD being 2-5mm.  Rank Sum Tests were used to compare numerical data at different follow-up observation periods. Kaplan-Meier curves and chi-square tests were used to evaluate the recovery of neurological function in relation to time.  A value of P <0.05 was considered statistically significant.

Results: At six weeks, half the sural nerves had recovered only to the S2 level while both the superficial peroneal nerves and saphenous nerves had returned almost to normal in a few patients. After three months, the sural nerve sensation began to recover, but there were no cases of complete recovery. There were a few cases of superficial peroneal nerve and saphenous nerve complete recovery after three months. Hyperalgesia started to disappear by six weeks after surgery in most cases and largely disappeared at three months except in patients with painful neuromas. All the involved nerves eventually healed with recovery becoming slower after nine months. No significant difference between nine months and one year in the Medical Research Council Scale. No significant difference between the different nerve-injury groups in terms of nerve recovery.  However, the saphenous and superficial peroneal nerves recovered more at six months than the sural nerve. By nine months and one year, neurological functions were significantly recovered than when compared to immediately after surgery. Recovery of sural sensory nerve function was unsatisfactory in one patient. Two patients developed painful neuroma, one from a patient with superficial peroneal nerve injury and one with a saphenous nerve injury. Conservative treatment failed with neuroma management and surgical intervention was required. Three months after surgery appeared to be an important time point for nerve recovery with the majority of patients being classified as S3 or higher by that point.  

Conclusion: Cutaneous nerve injury is common after ankle surgery secondarily to the incision, contusions, or entrapment of the nerves by suture. However, the follow-up of cutaneous nerve injuries is often neglected. In this study, all patients experienced abnormal sensation in the cutaneous nerve innervation region for at least six weeks. After three months the sensation disorders were gradually relieved with a few returning to normal, but the majority still had residual deficits. Recovery of the superficial peroneal nerve was the fastest overall, likely secondary to the ramus communicans and nerve distribution region. Nevertheless, generally recovery to normal of cutaneous nerves takes about six months to one year after surgery.  For a patient, that is a long time for abnormal sensation in their feet. Therefore, it’s important when planning the incision to take into consideration nerve distribution patterns. It also remains important for the podiatric surgeon to maintain atraumatic technique during dissection in order to avoid unnecessary damage to cutaneous nerve structures.

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