A 17-year-old boy is brought to the emergency department due to a lower extremity injury. The patient was playing football with his friends when he was tackled roughly and "felt something snap" in his right leg. He avoids bearing weight on the right foot. Examination shows a large contusion with point tenderness at the proximal lateral right leg. An x-ray of the leg is shown in the exhibit.

Which of the following would most likely be found on physical examination?

Question

A 17-year-old boy is brought to the emergency department due to a lower extremity injury. The patient was playing football with his friends when he was tackled roughly and "felt something snap" in his right leg. He avoids bearing weight on the right foot. Examination shows a large contusion with point tenderness at the proximal lateral right leg. An x-ray of the leg is shown in the exhibit.

Which of the following would most likely be found on physical examination?

Quizplus · Accepted Answer

11ec160b_35eb_f513_9249_df2c35e322a4_MD0001_00 The sciatic nerve branches into the common peroneal (fibular) nerve and the tibial nerve posteriorly in the thigh just proximal to the popliteal fossa. After coursing around the neck of the fibula, the common peroneal nerve divides into superficial and deep branches. The superficial branch innervates the muscles of the lateral compartment of the leg, which function primarily to evert the foot. The deep peroneal nerve innervates the anterior compartment of the leg, whose muscles act mainly as dorsiflexors of the foot and toes. The superficial peroneal nerve provides sensory innervation to the dorsum of the foot. The deep peroneal nerve provides sensory innervation to the region between the first and second digits of the foot. This patient has a fracture of the neck of the fibula. The common peroneal nerve is the most frequently injured nerve in the leg due to its superficial location as it courses laterally around the neck of the fibula. Injury to the common peroneal nerve from a proximal fibula fracture would cause loss of dorsal foot sensation as well as impaired dorsiflexion and eversion resulting in foot drop. (Choice A) The tibialis posterior (innervated by tibial nerve) is the major muscle involved in foot inversion. The tibialis anterior (innervated by common peroneal nerve) is less important, and patients with peroneal nerve injuries usually have normal foot inversion. (Choices B and E) The tibial nerve courses through the popliteal fossa and innervates the skin of the posterior calf, lateral foot, and sole; tissues of the knee joint; and muscles providing plantar flexion and inversion (eg, gastrocnemius, soleus, tibialis posterior). Injury to the tibial nerve would cause weakened plantar flexion and inversion of the foot as well as decreased sensation at the sole of the foot. (Choice D) Loss of sensation at the medial aspect of the leg would result from a lesion of the saphenous nerve, the largest pure sensory branch of the femoral nerve. Educational objective: The common peroneal nerve is vulnerable to injury where it courses around the neck of the fibula. Fibular neck fractures can injure this nerve, causing weakness of dorsiflexion (deep peroneal nerve) and eversion (superficial peroneal nerve) of the foot as well as loss of sensation over the dorsum of the foot.

A 17-Year-Old Boy Is Brought to the Emergency Department Due