Lower Limb Anatomy MCQ questions with answers and Explanation | Part – 4
Questions : 31- 40
Questions 31–35: A 20-year-old college student receives a severe blow on the inferolateral side of the left knee joint while playing football. Radiographic examination reveals a fracture of the head and neck of the fi bula.
31. Which of the following nerves is damaged?
(C) Common peroneal
(D) Deep peroneal
(E) Superfi cial peroneal
32. After injury to this nerve, which of the following muscles could be paralyzed?
(C) Extensor hallucis longus
(D) Flexor digitorum longus
(E) Tibialis posterior
33. If the lateral (fi bular) collateral ligament is torn by this fracture, which of the following conditions may occur?
(A) Abnormal passive abduction of the extended leg
(B) Abnormal passive adduction of the extended leg
(C) Anterior displacement of the femur on the tibia
(D) Posterior displacement of the femur on the tibia
(E) Maximal fl exion of the leg
34. Which of the following arteries could also be damaged by this fracture?
(B) Posterior tibial
(C) Anterior tibial
(E) Lateral inferior genicular
35. Which of the following conditions would occur from this fracture?
(A) Ischemia in the gastrocnemius
(B) Loss of plantar fl exion
(C) Trendelenburg’s sign
(D) Anterior tibial compartment syndrome
(E) Flat foot
36. A construction worker is hit on the leg with a concrete block and is subsequently unable to plantar fl ex and invert his foot. Which of the following muscles is most likely damaged?
(A) Extensor digitorum longus
(B) Tibialis anterior
(C) Tibialis posterior
(D) Peroneus longus
(E) Peroneus brevis
37. The obturator nerve and the sciatic (tibial portion) nerve of a 15-year-old boy are transected as a result of a motorcycle accident. This injury would result in complete paralysis of which of the following muscles?
(A) Rectus femoris
(B) Biceps femoris, short head
(D) Adductor magnus
38. A 24-year-old woman presents to her physician with weakness in fl exing the hip joint and extending the knee joint. Which scenario?
(C) Rectus femoris
(D) Vastus medialis
39. A 17-year-old boy was stabbed during a gang fight resulting in transection of the obturator nerve. Which of the following muscles is completely paralyzed?
(B) Adductor magnus
(C) Adductor longus
(D) Biceps femoris
40. A 32-year-old carpenter fell from the roof. The lateral longitudinal arch of his foot was flattened from fracture and displacement of the keystone for the arch. Which of the following bones is damaged?
(B) Cuboid bone
(C) Head of the talus
(D) Medial cuneiform
(E) Navicular bone
Answers and Explanations : 31-40
31. The Answer is C. The common peroneal nerve is vulnerable to injury as it passes behind the head of the fi bula and then winds around the neck of the fi bula and pierces the peroneus longus muscle, where it divides into the deep and superfi cial peroneal nerves. In addition, the deep and superfi cial peroneal nerves pass superfi cial to the neck of the fi bula in the substance of the peroneus longus muscle and are less susceptible to injury than the common peroneal nerve. Other nerves are not closely associated with the head and neck of the fi bula.
32. The Answer is C. The extensor hallucis longus is innervated by the deep peroneal nerve, whereas other muscles are innervated by the posterior tibial nerve.
33. The Answer is B. The lateral (fi bular) collateral ligament prevents adduction at the knee. Therefore, a torn lateral collateral ligament can be recognized by abnormal passive adduction of the extended leg. Abnormal passive abduction of the extended leg may occur when the medial (tibial) collateral ligament is torn. The anterior cruciate ligament prevents posterior displacement of the femur on the tibia; the posterior cruciate ligament prevents anterior displacement of the femur on the tibia. In addition, the posterior cruciate ligament is taut when the knee is fully flexed.
34. The Answer is C. The anterior tibial artery, which arises from the popliteal artery, enters the anterior compartment by passing through the gap between the fi bula and tibia at the upper end of the interosseous membrane. The other arteries would not be affected because they are not closely associated with the head and neck of the fi bula.
35. The Answer is D. Anterior tibial compartment syndrome is characterized by ischemic necrosis of the muscles of the anterior tibial compartment of the leg resulting from damage to the anterior tibial artery. The gastrocnemius receives blood from sural branches of the popliteal artery. Loss of plantar fl exion is due to necrosis of the posterior muscles of the leg, which are supplied by the posterior tibial and peroneal arteries. Trendelenburg’s sign is caused by weakness or paralysis of the gluteus medius and minimus muscles. Flat foot results from the collapse of the medial longitudinal arch of the foot.
36. The Answer is C. The tibialis posterior can plantar fl ex and invert the foot. The extensor digitorum longus can dorsifl ex and evert the foot, the tibialis anterior can dorsifl ex andinvert the foot, and the peroneus longus and brevis can plantar fl ex and evert the foot.
37. The Answer is D. The adductor magnus is innervated by both the obturator and sciatic (tibial portion) nerves. Hence, a lesion here could cause paralysis. The rectus femoris and sartorius are innervated by the femoral nerve. The biceps femoris long head is innervated by the tibial portion of the sciatic nerve, whereas the short head is innervated by the common peroneal portion of the sciatic nerve. The pectineus is innervated by both the femoral and obturator nerves.
38. The Answer is C. The rectus femoris fl exes the thigh and extends the leg. The sartorius can flex both the hip and knee joints. The gracilis adducts and fl exes the thigh and fl exes the leg, the vastus medialis extends the knee joint, and the semimembranosus extends the hip joint and fl exes the knee joint.
39. The Answer is C. The adductor longus is innervated by only the obturator nerve. Thus, injury here could completely paralyze the adductor longus. The pectineus is innervated by both the obturator and femoral nerves. The adductor magnus is innervated by both the obturator nerve and tibial part of the sciatic nerve. The biceps femoris is innervated by the tibial portion (long head) and common peroneal portion (short head) of the sciatic nerve. The semimembranosus is innervated by the tibial portion of the sciatic nerve.
40. The Answer is B. The keystone for the lateral longitudinal arch is the cuboid bone, whereas the keystone for the medial longitudinal arch is the head of the talus. The calcaneus, navicular, and medial cuneiform bones form a part of the medial longitudinal arch, but they are not keystones. The calcaneus also forms a part of the lateral longitudinal arch.