Orthopedic Anatomy Review | Dr Hutaif Basic Science Rev -...

Question 1

During a posterior approach to the hip (Kocher-Langenbeck), the main blood supply to the femoral head must be protected. The deep branch of the medial femoral circumflex artery (MFCA) is most at risk during the surgical release of which of the following structures?

Explanation

The MFCA runs deep to the quadratus femoris muscle. When releasing the quadratus femoris, the surgeon must leave a cuff of muscle attached to the femur or stay superficial to avoid injury to the MFCA, which is the predominant blood supply to the femoral head.

Question 2

The primary vascular supply to the proximal pole of the scaphoid enters the bone at which of the following anatomical locations?

Explanation

The primary blood supply to the scaphoid is from the radial artery. The major vessels enter the bone along the dorsal ridge, which is distal to the scaphoid waist. The blood supply to the proximal pole is entirely retrograde, which explains the high rate of avascular necrosis and nonunion in proximal pole fractures.

Question 3

During an anterior intrapelvic approach (ilioinguinal or modified Stoppa) for an acetabular fracture, significant hemorrhage occurs while dissecting over the posterior aspect of the superior pubic ramus. The injured vessel typically represents an anastomosis between which two vascular systems?

Explanation

The corona mortis (crown of death) is a vascular anastomosis between the obturator system (internal iliac) and the external iliac or inferior epigastric system. It is located on the posterior aspect of the superior pubic ramus, typically 4 to 9 cm from the pubic symphysis, and must be identified and ligated during anterior intrapelvic approaches.

Question 4

In a direct lateral approach to the fibula for open reduction and internal fixation of a lateral malleolus fracture, the superficial peroneal nerve must be protected. At approximately what distance proximal to the tip of the lateral malleolus does this nerve typically pierce the deep crural fascia to become subcutaneous?

Explanation

The superficial peroneal nerve typically pierces the deep crural fascia to become subcutaneous at approximately 10 to 12 cm proximal to the tip of the lateral malleolus. It exits the lateral compartment to run anteriorly, innervating the dorsum of the foot.

Question 5

A patient suffers from quadrilateral space syndrome, leading to localized shoulder weakness and paresthesia. Which nerve and vessel pass through this specific anatomic space?

Explanation

The quadrangular (quadrilateral) space is bounded superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the surgical neck of the humerus. It contains the axillary nerve and the posterior humeral circumflex artery.

Question 6

A 35-year-old volleyball player presents with isolated weakness in external rotation of the shoulder but normal abduction strength. An MRI shows a paralabral ganglion cyst causing nerve compression. Where is the cyst most likely located?

Explanation

Isolated weakness of external rotation (infraspinatus) with preserved abduction (supraspinatus) implies compression of the suprascapular nerve after it has innervated the supraspinatus. This occurs at the spinoglenoid notch. Compression at the suprascapular notch would affect both the supraspinatus and infraspinatus.

Question 7

During a lateral approach to the distal humerus, the radial nerve is identified. At what approximate landmark does the radial nerve pierce the lateral intermuscular septum to pass from the posterior to the anterior compartment of the arm?

Explanation

The radial nerve runs in the spiral groove and pierces the lateral intermuscular septum approximately 10 cm (range 7.5-12 cm) proximal to the lateral epicondyle to enter the anterior compartment of the arm. Knowing this anatomy is critical for surgical approaches and safe placement of external fixator half-pins.

Question 8

In a minimally invasive or percutaneous repair of a ruptured Achilles tendon, care must be taken to avoid iatrogenic injury to the sural nerve. What is the typical relationship of the sural nerve to the Achilles tendon?

Explanation

The sural nerve typically crosses the lateral border of the Achilles tendon roughly 10 cm (average 9.8 cm) proximal to the calcaneal insertion. It proceeds distally along the lateral aspect of the hindfoot, making it vulnerable during lateral or percutaneous approaches to the Achilles tendon.

Question 9

During anterior cruciate ligament (ACL) reconstruction, understanding the functional bundles is key to restoring normal knee kinematics. Which statement correctly describes the tension patterns of the native ACL bundles?

Explanation

The ACL consists of two main bundles named for their tibial insertion: anteromedial (AM) and posterolateral (PL). The AM bundle tightens in flexion, providing the primary restraint to anterior translation at 90 degrees of flexion. The PL bundle is tight in extension, providing rotational stability and limiting anterior translation near full extension.

Question 10

A 40-year-old man undergoes an electromyography (EMG) study for a suspected nerve entrapment. The neurologist notes the presence of a Martin-Gruber anastomosis. What does this anatomic variant typically represent?

Explanation

The Martin-Gruber anastomosis is a common anomalous connection in the forearm where motor fibers from the median nerve (or anterior interosseous nerve) cross over to join the ulnar nerve. This can result in atypical EMG findings and spared intrinsic hand function in proximal ulnar nerve injuries.

Question 11

The posterior interosseous nerve (PIN) is at risk during a volar approach (Henry) to the proximal radius. Through which specific structure does the PIN pass as it enters the posterior compartment of the forearm?

Explanation

The posterior interosseous nerve (PIN), the deep motor branch of the radial nerve, passes between the superficial and deep heads of the supinator muscle. The proximal fibrous edge of the superficial head of the supinator is known as the Arcade of Frohse, which is the most common site of PIN entrapment.

Question 12

The rotator interval is a capsular space in the shoulder that is often implicated in glenohumeral instability and adhesive capsulitis. What are the correct boundaries of the rotator interval?

Explanation

The rotator interval is bounded superiorly by the anterior margin of the supraspinatus tendon, inferiorly by the superior margin of the subscapularis tendon, laterally by the transverse humeral ligament, and medially by the base of the coracoid process. It contains the long head of the biceps tendon, the coracohumeral ligament, and the superior glenohumeral ligament.

Question 13

Which of the following is considered the primary and strongest stabilizer against valgus talar tilt within the superficial component of the deltoid ligament of the ankle?

Explanation

The deltoid ligament consists of superficial and deep layers. The superficial layer mainly resists valgus forces, with the tibiocalcaneal ligament being the thickest and strongest component of the superficial deltoid. The deep layer (deep anterior and posterior tibiotalar ligaments) is the primary restraint to lateral and anterior displacement of the talus.

Question 14

During a cervical lymph node biopsy in the posterior triangle of the neck, a patient sustains an iatrogenic nerve injury leading to a laterally winged scapula. Which muscle is predominantly affected by this injury?

Explanation

The posterior triangle of the neck contains the spinal accessory nerve (CN XI), which innervates the trapezius muscle. Injury leads to lateral winging of the scapula (the scapula is displaced laterally and inferiorly). Medial winging, in contrast, is caused by injury to the long thoracic nerve, which innervates the serratus anterior.

Question 15

The posterior cruciate ligament (PCL) is the primary restraint to posterior tibial translation. Which of the following accurately describes its functional bundle anatomy and biomechanics?

Explanation

The PCL consists of the larger anterolateral (AL) bundle and the smaller posteromedial (PM) bundle. The AL bundle is tight in flexion, whereas the PM bundle is tight in extension. This is conceptually the reverse of the ACL bundles, where the AM is tight in flexion and PL in extension.

Question 16

The triangular fibrocartilage complex (TFCC) is the major stabilizer of the distal radioulnar joint (DRUJ). Which specific part of the TFCC has a rich blood supply and is therefore more amenable to primary surgical repair?

Explanation

The blood supply to the TFCC is limited to its peripheral 10-20%, which receives vessels from the ulnar artery and the palmar/dorsal branches of the anterior interosseous artery. The central and radial portions are avascular. Therefore, peripheral (ulnar-sided) tears have healing potential and are often amenable to primary repair.

Question 17

De Quervain's tenosynovitis affects the first dorsal extensor compartment of the wrist. Intersection syndrome involves friction between the first and second dorsal compartments. Which muscles comprise the second dorsal compartment?

Explanation

The first dorsal compartment contains the APL and EPB. The second compartment contains the ECRL and ECRB. Intersection syndrome occurs where the muscle bellies of the first compartment cross over the tendons of the second compartment.

Question 18

The femoral nerve is the largest branch of the lumbar plexus. It descends through the pelvis to enter the anterior thigh. What is its anatomical relationship to the psoas major muscle within the retroperitoneum?

Explanation

The femoral nerve (roots L2-L4) emerges from the lateral border of the psoas major muscle, descending in the anatomic groove between the psoas and iliacus muscles before passing under the inguinal ligament. The obturator nerve emerges from the medial border, and the genitofemoral nerve pierces the anterior surface of the psoas major.

Question 19

The superficial medial collateral ligament (sMCL) of the knee is the primary restraint to valgus stress. Where is its precise distal anatomic insertion on the tibia?

Explanation

The superficial MCL originates on the medial epicondyle of the femur and inserts on the medial surface of the proximal tibia, approximately 4.5 cm distal to the joint line. It specifically inserts deep (underneath) to the pes anserinus tendons (sartorius, gracilis, semitendinosus).

Question 20

The talus is highly prone to avascular necrosis following displaced fractures of the talar neck. Which artery provides the most significant vascular contribution to the body of the talus?

Explanation

The most robust and significant blood supply to the body of the talus comes from the artery of the tarsal canal, which is a branch of the posterior tibial artery. It forms an anastomotic sling with the artery of the sinus tarsi and supplies the vast majority of the talar body.

Question 21

A surgeon is performing a posterolateral approach to the distal tibia for a pilon fracture. What is the internervous plane utilized in this approach?

Explanation

The posterolateral approach to the tibia utilizes the internervous plane between the lateral compartment (superficial peroneal nerve) and the deep posterior compartment (tibial nerve). Specifically, the muscular interval developed is between the peroneus brevis anteriorly and the flexor hallucis longus posteriorly.

Question 22

During the ilioinguinal approach for an acetabular fracture, the surgeon develops the middle window. Which of the following structures forms the medial border of this middle window?

Explanation

The ilioinguinal approach creates three distinct surgical windows. The medial window is between the rectus abdominis and the external iliac vessels. The middle window is bordered medially by the external iliac vessels and laterally by the iliopsoas muscle. The lateral window lies lateral to the iliopsoas.

Question 23

A 45-year-old male sustains a midshaft humerus fracture and is treated with open reduction and internal fixation via an anterolateral approach. Which of the following describes the correct internervous plane for the distal extent of this approach?

Explanation

Proximally, the anterolateral approach to the humerus goes between the deltoid (axillary n.) and pectoralis major (pectoral nerves). Distally, the true internervous plane is between the brachialis (musculocutaneous n.) and the brachioradialis (radial n.). Splitting the brachialis longitudinally in its lateral third is also a common variation to protect the radial nerve.

Question 24

Which of the following muscles of the lower extremity is exclusively innervated by the common peroneal division of the sciatic nerve?

Explanation

The short head of the biceps femoris is the only muscle in the posterior compartment of the thigh that receives its innervation from the common peroneal division of the sciatic nerve. All other hamstring muscles are innervated by the tibial division.

Question 25

A patient is undergoing a volar (Henry) approach to the forearm for fixation of a proximal radial shaft fracture. In the proximal third of the forearm, the internervous plane is between which of the following two muscles?

Explanation

The volar (Henry) approach to the radius exploits the internervous plane between the brachioradialis (radial nerve) and the pronator teres (median nerve) in the proximal forearm. In the distal forearm, the plane is between the brachioradialis and the flexor carpi radialis.

Question 26

During a surgical approach to the hip via the direct lateral (Hardinge) approach, the gluteus medius and vastus lateralis are split. To avoid iatrogenic denervation of the anterior portion of the abductors, the proximal split in the gluteus medius must not extend more than how many centimeters proximal to the tip of the greater trochanter?

Explanation

The superior gluteal nerve courses approximately 3 to 5 cm proximal to the tip of the greater trochanter. Extending the longitudinal split in the gluteus medius further than 5 cm proximally places the nerve at significant risk, which can result in abductor weakness and a Trendelenburg gait.

Question 27

A 28-year-old male sustains a severe knee dislocation resulting in a popliteal artery occlusion. The popliteal artery is at high risk of stretch injury due to firm proximal and distal tethering points. Which anatomical structure forms the distal tethering point?

Explanation

The popliteal artery is firmly tethered proximally at the adductor hiatus (an opening in the adductor magnus tendon) and distally at the tendinous arch of the soleus (soleal sling). This fixed anatomical position makes the artery highly susceptible to traction injury during severe tibial translation in knee dislocations.

Question 28

A surgeon is evaluating a patient with axillary nerve entrapment. Which of the following neurovascular structures pass together through the quadrangular space of the shoulder?

Explanation

The quadrangular space is defined superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the surgical neck of the humerus. It serves as the exit for the axillary nerve and the posterior circumflex humeral artery.

Question 29

When performing an open carpal tunnel release, the surgeon must be mindful of the recurrent motor branch of the median nerve (the "million dollar nerve"). According to the Lanz classification, which anatomical variation of the recurrent motor branch is the most common?

Explanation

The extraligamentous course is the most common anatomical variation of the recurrent motor branch of the median nerve (occurring in approximately 50-75% of individuals). It branches off the median nerve distal to the transverse carpal ligament and recurrently turns to enter the thenar musculature.

Question 30

During the volar (Russe) approach to the scaphoid for open reduction and internal fixation of a waist fracture, the surgical interval for deep exposure involves incising the sheath of which of the following tendons?

Explanation

The volar approach to the scaphoid requires an incision centered over the flexor carpi radialis (FCR) tendon. The FCR tendon sheath is opened, and the tendon is retracted ulnarly (to protect the median nerve) or radially (to protect the radial artery). The deep floor of the FCR sheath is incised to access the volar radiocarpal capsule and the scaphoid.

Question 31

The deep branch of the radial nerve (posterior interosseous nerve) is at risk during surgical approaches to the proximal radius. Underneath which anatomical structure does the posterior interosseous nerve typically enter the supinator muscle?

Explanation

The posterior interosseous nerve (PIN) passes under the thick fibrous proximal edge of the superficial head of the supinator muscle, known as the Arcade of Frohse. This is the most common site for PIN entrapment (radial tunnel syndrome).

Question 32

During closed reduction of a proximal humerus fracture, a patient sustains an iatrogenic injury to the axillary nerve. Which of the following muscles would most likely demonstrate denervation on electromyography?

Explanation

The axillary nerve is derived from the posterior cord of the brachial plexus (C5-C6). It provides motor innervation to the deltoid and the teres minor muscles, and provides sensation to the lateral aspect of the shoulder via the superior lateral brachial cutaneous nerve.

Question 33

A 35-year-old female presents with pain, weakness, and paresthesias affecting the medial aspect of her forearm and the ring and small fingers of her hand. True neurogenic thoracic outlet syndrome is suspected. Compression of which part of the brachial plexus is most characteristic of this presentation?

Explanation

True neurogenic thoracic outlet syndrome typically involves compression of the lower trunk of the brachial plexus (C8-T1). This leads to sensory symptoms in the distribution of the medial antebrachial cutaneous nerve and ulnar nerve, and motor weakness in intrinsic hand muscles supplied by the lower trunk.

Question 34

An orthopaedic surgeon is using the posterior (Kocher-Langenbeck) approach to the acetabulum. The sciatic nerve must be carefully identified and protected. In what percentage of the general population does the common peroneal division of the sciatic nerve pierce the piriformis muscle (Beaton and Anson type B)?

Explanation

Anatomical variations exist in the relationship between the sciatic nerve and the piriformis muscle. In approximately 85% of people, the entire nerve exits below the piriformis. In about 10-15% of the population, the common peroneal division pierces the piriformis while the tibial division passes below it.

Question 35

The superficial peroneal nerve provides sensation to the majority of the dorsum of the foot. At what approximate distance proximal to the tip of the lateral malleolus does the superficial peroneal nerve pierce the deep fascia to become subcutaneous?

Explanation

The superficial peroneal nerve courses downward within the lateral compartment of the leg and pierces the crural fascia to become superficial/subcutaneous approximately 10 to 12 cm proximal to the tip of the lateral malleolus. It is at significant risk during anterolateral ankle arthroscopy portals and approaches to the distal fibula.

Question 36

Anatomic reconstruction of the medial patellofemoral ligament (MPFL) requires precise femoral tunnel placement. Where is the normal anatomical footprint of the MPFL on the femur located in relation to palpable osseous landmarks?

Explanation

The femoral footprint of the MPFL is located in a saddle-like depression. It is situated distal to the adductor tubercle, and proximal and slightly posterior to the medial epicondyle. Accurate identification of this site (radiographically approximated by Schöttle's point) is crucial for a successful MPFL reconstruction to ensure isometric graft behavior.

Question 37

During a posteromedial approach to the knee for repair of a medial meniscus root tear, the fascia over the pes anserinus is incised. Which nerve is most at risk of injury when dissecting directly around the sartorius and gracilis tendons?

Explanation

The saphenous nerve is a sensory terminal branch of the femoral nerve that exits the adductor canal and runs distally along the medial aspect of the knee, typically emerging between the sartorius and gracilis muscles. It is highly vulnerable during medial-sided knee exposures, hamstring tendon harvests, and meniscal repairs.

Question 38

The artery of the tarsal canal provides the dominant blood supply to the body of the talus. From which main parent vessel does the artery of the tarsal canal directly originate?

Explanation

The posterior tibial artery gives rise to the artery of the tarsal canal, which courses through the deltoid ligament to enter the tarsal canal. It forms an anastomotic sling with the artery of the sinus tarsi (which arises from the perforating peroneal and dorsalis pedis arteries) to supply the talar body.

Question 39

A patient presents with tenderness in the anatomical snuffbox after a fall on an outstretched hand. Which of the following describes the correct tendinous boundaries of the anatomical snuffbox when the hand is in the standard anatomical position?

Explanation

In the standard anatomical position (palms facing anteriorly), the thumb is lateral. The anatomical snuffbox is bounded medially (ulnarly) by the tendon of the Extensor pollicis longus (EPL), and laterally (radially) by the tendons of the Abductor pollicis longus (APL) and Extensor pollicis brevis (EPB). The radial artery runs through its floor.

Question 40

During an anterior approach to the cervical spine (Smith-Robinson approach), blunt dissection is carried down to the prevertebral fascia. This dissection naturally passes between which two distinct anatomical sheaths/layers?

Explanation

The standard anterior approach to the cervical spine utilizes the relatively avascular interfascial plane between the carotid sheath (containing the common carotid artery, internal jugular vein, and vagus nerve) located laterally, and the visceral axis (trachea, esophagus, and thyroid gland) located medially.

Question 41

A surgeon is performing a lateral approach to the proximal humerus. To avoid iatrogenic injury to the axillary nerve, the deltoid split should not extend distal to what landmark?

Explanation

The axillary nerve crosses the humerus approximately 5 to 7 cm distal to the lateral edge of the acromion. Extending a deltoid split beyond 5 cm places the nerve at significant risk of transection.

Question 42

The volar (Henry) approach to the radius utilizes a distinct internervous plane. Proximally, this plane is developed between which two muscles?

Explanation

The proximal internervous plane of the volar Henry approach is between the brachioradialis (radial nerve) and the pronator teres (median nerve). Distally, the plane transitions between the brachioradialis and the flexor carpi radialis.

Question 43

During a posterolateral (Kocher) approach to the radial head for a comminuted fracture, the internervous plane is developed between the anconeus and which other muscle?

Explanation

The Kocher approach utilizes an internervous plane between the anconeus (innervated by the radial nerve) and the extensor carpi ulnaris (innervated by the posterior interosseous nerve).

Question 44

The anterolateral (Watson-Jones) approach to the hip exploits the plane between the tensor fasciae latae (TFL) and the gluteus medius. Which nerve innervates both of these muscles?

Explanation

Both the TFL and gluteus medius are innervated by the superior gluteal nerve. Therefore, the Watson-Jones approach utilizes an intermuscular, rather than a true internervous, plane.

Question 45

When harvesting hamstring autografts for ACL reconstruction, the surgeon must identify the pes anserinus. From anterior to posterior, what is the correct arrangement of the tendons at their insertion on the proximal medial tibia?

Explanation

The correct anterior-to-posterior orientation of the pes anserinus insertion is Sartorius, Gracilis, and Semitendinosus. A useful mnemonic is 'Say Grace before Tea'.

Question 46

A 45-year-old male presents with a posterolateral disc herniation at the L4-L5 level. Which nerve root is most commonly compressed by this specific pathology?

Explanation

In the lumbar spine, a typical posterolateral disc herniation affects the traversing nerve root. Therefore, an L4-L5 herniation will most commonly compress the L5 nerve root.

Question 47

A volleyball player presents with isolated weakness in external rotation of the shoulder but normal abduction initiation. MRI shows a paralabral cyst. Where is the cyst most likely located?

Explanation

Entrapment of the suprascapular nerve at the spinoglenoid notch affects only the motor branch to the infraspinatus, causing isolated external rotation weakness. Entrapment at the suprascapular notch would also affect the supraspinatus.

Question 48

Which flexor tendon pulleys of the hand are mechanically most critical to preserve during surgery to prevent bowstringing of the flexor tendons?

Explanation

The A2 (proximal phalanx) and A4 (middle phalanx) pulleys are the major mechanical pulleys of the digital flexor sheath. They must be preserved to prevent bowstringing and subsequent loss of mechanical advantage.

Question 49

In the most common anatomical variant of the sciatic nerve's relationship to the piriformis muscle, where do the common peroneal and tibial nerve divisions exit the pelvis?

Explanation

In over 80% of individuals, the undivided sciatic nerve passes completely inferior to the piriformis muscle through the greater sciatic foramen. Variations involving the peroneal division piercing or passing above the piriformis are less common.

Question 50

The Lisfranc ligament is essential for the stability of the midfoot and the tarsometatarsal articulation. It connects which two bony structures?

Explanation

The true Lisfranc ligament runs from the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is the largest and strongest of the tarsometatarsal ligaments.

Question 51

During a dorsal approach to the wrist, Lister's tubercle serves as a key landmark. The tendon of the extensor pollicis longus (EPL) typically runs in which direction relative to this structure?

Explanation

The EPL tendon courses in the third dorsal extensor compartment, which is located immediately ulnar to Lister's tubercle. It uses the tubercle as a fulcrum to redirect its path toward the thumb.

Question 52

A patient sustains a vertically unstable pelvic fracture involving the sacral ala. Postoperatively, the patient demonstrates an inability to plantarflex the great toe and loss of sensation over the lateral plantar aspect of the foot. Which nerve root was most likely injured?

Explanation

The S1 nerve root provides motor innervation for plantar flexion and sensation to the lateral and plantar aspect of the foot. Sacral ala fractures traversing the sacral foramina commonly place the L5 or S1 nerve roots at risk.

Question 53

A runner develops acute exertional compartment syndrome requiring fasciotomies. Which of the following muscles is located exclusively within the deep posterior compartment of the leg?

Explanation

The deep posterior compartment of the leg contains the tibialis posterior, flexor hallucis longus, and flexor digitorum longus muscles. It also houses the posterior tibial artery and the tibial nerve.

Question 54

The popliteofibular ligament is a primary stabilizer against external rotation of the tibia. It originates from the popliteus tendon and attaches to which anatomical structure?

Explanation

The popliteofibular ligament arises from the popliteus musculotendinous junction and inserts on the posteromedial aspect of the fibular styloid. It is a crucial isometric component of the posterolateral corner of the knee.

Question 55

A patient suffers a midshaft humeral fracture. During a lateral approach to the humerus, the radial nerve is identified piercing the lateral intermuscular septum. At what approximate distance proximal to the lateral epicondyle does this transition occur?

Explanation

The radial nerve pierces the lateral intermuscular septum, transitioning from the posterior compartment to the anterior compartment, approximately 10 cm proximal to the lateral epicondyle.

Question 56

In a healthy adult, the predominant blood supply to the weight-bearing dome of the femoral head is provided by the lateral epiphyseal artery. This vessel is a terminal branch of which of the following?

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) is the primary vascular supply to the adult femoral head. It gives rise to the lateral epiphyseal vessels that perfuse the superolateral weight-bearing dome.

Question 57

From anterior/medial to posterior/lateral, what is the correct anatomical order of structures passing behind the medial malleolus in the tarsal tunnel?

Explanation

The correct sequence from anterior to posterior is Tibialis posterior, flexor Digitorum longus, Artery (posterior tibial), Vein, Nerve (tibial), and flexor Hallucis longus. This follows the classic mnemonic 'Tom, Dick, And Very Nervous Harry'.

Question 58

A 35-year-old male presents with posterior shoulder pain and numbness over the lateral deltoid. An MRI reveals a space-occupying lesion in the quadrilateral space. Which of the following structures form the superior and inferior borders of this space, respectively?

Explanation

The quadrilateral space is bounded superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the humeral shaft. It transmits the axillary nerve and posterior circumflex humeral vessels.

Question 59

Which of the following statements most accurately describes the vascular supply of the adult meniscus?

Explanation

In adults, only the peripheral 10% to 30% of the meniscus is vascularized (the 'red-red' zone) by branches of the genicular arteries. The avascular inner zones rely entirely on diffusion from the synovial fluid.

Question 60

During a lateral approach to the proximal humerus for open reduction and internal fixation, the axillary nerve must be identified and protected. What is the average distance of the axillary nerve from the lateral edge of the acromion, and what structure does it run deep to?

Explanation

The axillary nerve runs transversely from posterior to anterior approximately 5 to 7 cm distal to the lateral edge of the acromion. It courses on the deep surface of the deltoid muscle, crossing the humerus from posterior to anterior.

Question 61

A direct lateral (Hardinge) approach to the hip requires splitting the gluteus medius. To avoid iatrogenic denervation, the proximal split should not extend beyond what distance from the tip of the greater trochanter?

Explanation

The superior gluteal nerve supplies the gluteus medius, gluteus minimus, and tensor fasciae latae. Splitting the gluteus medius more than 5 cm proximal to the tip of the greater trochanter places this nerve at significant risk of transection.

Question 62

During a posterolateral (Kocher) approach to the radial head, the internervous plane utilized is between the anconeus and the extensor carpi ulnaris (ECU). The posterior interosseous nerve (PIN) is most at risk of injury when retracting which of the following muscles?

Explanation

The PIN enters the forearm between the two heads of the supinator at the arcade of Frohse. During a Kocher approach, the supinator must be carefully elevated off the radius and retracted anteriorly to protect the PIN lying within its substance.

Question 63

The anterior approach to the hip (Smith-Petersen) utilizes an internervous plane between the sartorius and the tensor fasciae latae. Which of the following nerves is at greatest risk during the superficial dissection?

Explanation

The lateral femoral cutaneous nerve emerges near the anterior superior iliac spine (ASIS) and passes distally over the sartorius. It is highly susceptible to injury or traction during the superficial dissection of the Smith-Petersen approach.

Question 64

A patient presents with a high-energy knee dislocation (KD III) resulting in an abnormal ankle-brachial index (ABI). Angiography reveals an occlusion of the popliteal artery. The popliteal artery is relatively fixed and highly susceptible to tethering and intimal injury between which two anatomic structures?

Explanation

The popliteal artery is firmly tethered proximally at its exit from Hunter's canal (the adductor hiatus) and distally at the fibrous arch of the soleus. This anatomic fixation prevents mobility during high-energy knee dislocations, increasing the risk of vascular injury.

Question 65

During a Latarjet procedure for recurrent anterior shoulder instability, the conjoined tendon is retracted medially. The musculocutaneous nerve typically penetrates the coracobrachialis at what average distance distal to the tip of the coracoid process?

Explanation

The musculocutaneous nerve enters the medial aspect of the coracobrachialis roughly 3 to 8 cm (average 5 cm) distal to the tip of the coracoid process. Vigorous distal or medial retraction of the conjoined tendon can cause severe neuropraxia.

Question 66

An extensile lateral approach is planned for an intra-articular calcaneus fracture. The sural nerve is at risk in the posterolateral corner of the flap. From which two nerves does the sural nerve primarily derive its origins?

Explanation

The sural nerve is formed by the confluence of the medial sural cutaneous nerve (a branch of the tibial nerve) and the sural communicating branch (from the lateral sural cutaneous nerve, a branch of the common peroneal nerve).

Question 67

A patient sustains a spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture) and presents with wrist drop. The radial nerve is at high risk as it pierces which muscle septum to transition from the posterior to the anterior compartment of the arm?

Explanation

The radial nerve runs in the spiral groove of the humerus and pierces the lateral intermuscular septum approximately 10 cm proximal to the lateral epicondyle. It transitions from the posterior compartment to the anterior compartment at this level.

Question 68

An anterolateral approach to the proximal tibia is performed for a Schatzker type III tibial plateau fracture. Dissection is carried out between the tibialis anterior and extensor digitorum longus. Which neurovascular bundle supplies this compartment and courses on the anterior surface of the interosseous membrane?

Explanation

The anterior compartment of the leg is supplied by the deep peroneal nerve and the anterior tibial artery. These structures run together distally on the anterior surface of the interosseous membrane.

Question 69

A patient presents with shoulder weakness and pain two months after a radical neck dissection for squamous cell carcinoma. Examination reveals winging of the scapula with lateral translation of the inferior pole. Which muscle is denervated, and what is its primary motor nerve?

Explanation

Lateral winging of the scapula is characteristic of trapezius palsy, which is innervated by the spinal accessory nerve (CN XI). Medial winging is typically caused by serratus anterior paralysis due to long thoracic nerve injury.

Question 70

The volar (Henry) approach to the forearm utilizes the internervous plane between the brachioradialis and the pronator teres proximally. Which of the following nerves innervates the brachioradialis?

Explanation

Although the brachioradialis acts as a flexor of the elbow, it is innervated by the radial nerve. The internervous plane for the proximal Henry approach is between the brachioradialis (radial nerve) and the pronator teres (median nerve).

Question 71

A patient with an isolated nerve injury is unable to actively flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger, resulting in a positive "OK" sign. Which of the following muscles is ALSO innervated by the affected nerve?

Explanation

The patient has an anterior interosseous nerve (AIN) palsy. The AIN is a pure motor branch of the median nerve that innervates the flexor pollicis longus, the flexor digitorum profundus to the index and middle fingers, and the pronator quadratus.

Question 72

In the developing child prior to physeal closure, the primary blood supply to the capital femoral epiphysis is derived from the lateral epiphyseal artery. This vessel is a terminal branch of which artery?

Explanation

The medial femoral circumflex artery (MFCA) gives rise to the lateral epiphyseal vessels. These vessels provide the predominant blood supply to the capital femoral epiphysis in children, as the physis blocks the metaphyseal vessels.

Question 73

During a medial approach to the midfoot for an accessory navicular excision, a tendinous crossover is encountered under the navicular known as the "Master Knot of Henry." This anatomical landmark is formed by the intersection of which two tendons?

Explanation

The Master Knot of Henry is located in the plantar midfoot. It is formed where the flexor digitorum longus (FDL) crosses superficial (plantar) and lateral to the flexor hallucis longus (FHL) tendon.

Question 74

A professional volleyball player presents with insidious onset, painless weakness of shoulder external rotation. MRI reveals a paralabral cyst located in the spinoglenoid notch. Which muscle exhibits denervation atrophy?

Explanation

The suprascapular nerve innervates the supraspinatus before passing through the spinoglenoid notch to innervate the infraspinatus. Compression at the spinoglenoid notch spares the supraspinatus but causes isolated infraspinatus denervation.

Question 75

In patients with neurogenic thoracic outlet syndrome, compression most commonly occurs within the interscalene triangle. What are the anatomical borders of this triangle?

Explanation

The interscalene triangle is bordered anteriorly by the anterior scalene, posteriorly by the middle scalene, and inferiorly by the first rib. The brachial plexus trunks and the subclavian artery pass through this triangle.

Question 76

During an anterior cervical discectomy and fusion (ACDF), aggressive lateral dissection past the uncinate process risks catastrophic injury to the vertebral artery. At which cervical level does the vertebral artery typically enter the transverse foramen?

Explanation

The vertebral artery arises from the first part of the subclavian artery and typically enters the transverse foramen of the cervical spine at the C6 level, bypassing the C7 transverse foramen.

Question 77

During a lateral transpsoas approach to the lumbar spine, the lumbar plexus is at risk of injury as it lies within the substance of the psoas major. At the L4-L5 disc space, where is the lumbar plexus generally located relative to the psoas muscle?

Explanation

In the lateral transpsoas approach, the lumbar plexus predictably migrates anteriorly as it descends. At the L4-L5 level, the plexus is located in the posterior third of the psoas major, requiring the surgeon to stay in the anterior half of the muscle.

Question 78

The recurrent motor branch of the median nerve (the "million dollar nerve") innervates the thenar musculature. Which of the following muscles is primarily innervated by the deep branch of the ulnar nerve rather than the median nerve?

Explanation

The adductor pollicis and the deep head of the flexor pollicis brevis are innervated by the deep branch of the ulnar nerve. The median nerve supplies the LOAF muscles: Lumbricals 1 & 2, Opponens pollicis, Abductor pollicis brevis, and the superficial head of the Flexor pollicis brevis.

Question 79

During an axillary approach to the shoulder, the surgeon must identify the boundaries of the quadrangular space to protect its neurovascular contents. Which of the following muscles forms the inferior border of this anatomical space?

Explanation

The quadrangular space is bounded superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the surgical neck of the humerus. It contains the axillary nerve and the posterior humeral circumflex artery.

Question 80

A 28-year-old volleyball player presents with isolated weakness in external rotation of the shoulder without any deficit in abduction. At which of the following anatomical locations is the involved nerve compression most likely occurring?

Explanation

Compression of the suprascapular nerve at the spinoglenoid notch affects only the infraspinatus muscle, leading to isolated external rotation weakness. Compression at the suprascapular notch would affect both the supraspinatus (abduction) and infraspinatus (external rotation).

Question 81

A patient develops an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger following a forearm injury. Sensation is completely intact. Which of the following structures is most likely causing compression of the involved nerve?

Explanation

This presentation describes anterior interosseous nerve (AIN) syndrome, characterized by pure motor loss to the FPL, FDP (index/middle), and pronator quadratus. The AIN is most commonly compressed by the tendinous edge of the deep head of the pronator teres or the fibrous arch of the FDS.

Question 82

While performing a percutaneous or minimally invasive repair of an acute Achilles tendon rupture, the surgeon must be cautious of the sural nerve. At what approximate distance proximal to the calcaneal insertion does the sural nerve typically cross the lateral border of the Achilles tendon?

Explanation

The sural nerve crosses from the midline to the lateral border of the Achilles tendon approximately 10 cm proximal to its insertion on the calcaneus. Dissection or percutaneous suturing proximal to this level carries a higher risk of sural nerve injury.

Question 83

During a direct lateral (Hardinge) approach to the hip, proximal splitting of the gluteus medius is limited to prevent denervation of the anterior portion of the muscle. The superior gluteal nerve is at greatest risk if the split extends more than what distance proximal to the tip of the greater trochanter?

Explanation

The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. It is located approximately 5 cm proximal to the tip of the greater trochanter, marking the superior limit of the "safe zone" for splitting the gluteus medius.

Question 84

During a posterolateral approach to the knee for ligamentous reconstruction, the surgeon identifies the structures of the posterolateral corner. What is the correct anatomical relationship of the popliteus tendon footprint on the lateral femoral condyle relative to the lateral collateral ligament (LCL) origin?

Explanation

On the lateral femoral condyle, the popliteus tendon inserts in the popliteal sulcus, which is located distal and anterior to the origin of the lateral collateral ligament. This relationship is critical during anatomical posterolateral corner (PLC) reconstructions.

Question 85

A surgeon is performing an anterolateral approach to the distal tibia. To avoid injury to the superficial peroneal nerve, the surgeon must be aware of its typical exit site from the deep fascia. At approximately what distance proximal to the lateral malleolus does this nerve pierce the crural fascia?

Explanation

The superficial peroneal nerve transitions from the lateral compartment by piercing the deep crural fascia approximately 10 to 12 cm proximal to the tip of the lateral malleolus. It then divides into the medial and intermediate dorsal cutaneous nerves.

Question 86

The blood supply to the talar body is tenuous, predisposing it to avascular necrosis following displaced talar neck fractures. Which of the following arteries provides the majority of the blood supply to the talar body?

Explanation

The artery of the tarsal canal is a branch of the posterior tibial artery and provides the dominant blood supply to the talar body. The artery of the tarsal sinus (from the anterior tibial/dorsalis pedis and peroneal arteries) supplies the talar head and neck.

Question 87

In the surgical treatment of a midfoot deformity, a surgeon exposes the plantar aspect of the foot and encounters the Master Knot of Henry. Which of the following best describes the anatomical relationship at this specific location?

Explanation

At the Master Knot of Henry, located in the plantar midfoot, the flexor hallucis longus (FHL) tendon crosses deep (dorsal) to the flexor digitorum longus (FDL) tendon. The FDL crosses from medial to lateral over the FHL.

AAOS & ABOS Basic Science MCQs (Set 3): Bone Biology, Biomechanics & Anatomy Review

Orthopedic Anatomy Review | Dr Hutaif Basic Science Rev -...

Key Takeaway

Orthopedic Anatomy Review | Dr Hutaif Basic Science Rev -...

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