ABSTRACT: Our case report demonstrates the importance of conducting a thorough neurological examination in the evaluation of lateral ankle sprain. The patient, a dancer, reported an inversion injury to his ankle that was associated with lateral ankle pain, numbness, and paresthesia. The patient had positive Tinel test results over the distal portion of the leg in the distribution of the sural nerve. The diagnosis was a grade 1 lateral right ankle sprain complicated by an injury to the sural nerve. Treatment included scheduled anti-inflammatory medication and limited icing of the ankle. The patient returned 1 week later and reported significant improvement; after 1 month, he had returned to full activity. Knowledge of sural nerve anatomy is essential for examining physicians to make this diagnosis. (J Musculoskel Med. 2008;25:126-128)
Injury to the sural nerve in association with lateral ankle sprain rarely is mentioned in the literature. However, this injury may occur more frequently than commonly thought, and it may be an underdiagnosed and mistreated component of ankle sprains.1
In this article, we offer a case report of a patient with sural nerve injury after ankle sprain and a discussion of the implications for diagnosis and treatment. The case demonstrates the importance of conducting a thorough neurological examination in the evaluation of the common lateral ankle sprain. We also illustrate the potential management pitfalls.
CASE REPORT
Presentation and history
A 25-year-old performer for a premier dance show reported an inversion injury to his right ankle that was associated with lateral ankle pain. Seven days later, numbness and tingling began to develop in his right heel and the lateral aspect of his right foot. When the patient was initially evaluated 11 days after the injury, he reported continued numbness in the right heel and lateral ankle region, as well as pain around the lateral malleolus. The patient had been unable to perform and was limiting his activity because of the numbness. He denied any past medical or surgical history.
Evaluation
The initial examination revealed an athletic, well-conditioned man in no acute distress but with a slightly antalgic gait. Inspection of the ankle showed mild swelling over the lateral right ankle. Palpation revealed mild pain at the anterior talofibular ligament but no pain over the calcaneofibular ligament, peroneal tendon, navicular, bifurcate ligament, base of the fifth metatarsal, or proximal fibula.
Results of the squeeze test were negative; anterior drawer testing revealed pain with stress but no laxity (Table). The patient had mild loss of range of motion of the ankle; motor testing of L3 through S1 showed 5/5 strength. The patient had positive Tinel test results over the distal portion of the leg in the distribution of the sural nerve and numbness on examination of the right heel and lateral right foot. Slump, straight-leg raise, cross-straight leg, and FABER (flexion, abduction, and external rotation) test results were negative.
Radiographs of the right ankle showed an intact mortise and no evidence of osteochondritis dissecans or acute fracture. A previous avulsion fracture was noted at the distal medial malleolus, and an anterior talar osteophyte was seen. The diagnosis was a grade 1 (mild) lateral right ankle sprain, complicated by an injury to the sural nerve.
Follow-up
Treatment involved scheduled anti-inflammatory medication and icing of the ankle for no more than 10 minutes 4 times per day. The patient was restricted in his dance to no jumping, landing, or pushing-off of the right foot. He began a home-exercise program to maintain full ankle range of motion. Bracing initially was not advised to avoid potential compression injury to the sural nerve.
