AAOS Orthopedic MCQs: Hip Trauma 2026 Board Review

Question 1

A 65-year-old female sustains a vertically oriented (Pauwels type III) femoral neck fracture. To maximize biomechanical stability and preserve the primary vascular supply to the femoral head, which structure must be protected and what is its anatomic course?

Explanation

The deep branch of the medial circumflex femoral artery provides the predominant blood supply to the adult femoral head. It courses posterior to the obturator externus and anterior to the short external rotators before entering the capsule.

Question 2

According to modern quantitative perfusion studies, which vascular structure provides the predominant blood supply to the humeral head, and via which anatomical pathway does it enter?

Explanation

Recent studies (e.g., Hettrich et al.) demonstrated that the posterior circumflex humeral artery provides approximately 64% of the blood supply to the humeral head, entering via the posterior capsule, overriding the historical emphasis on the arcuate branch of the anterior circumflex.

Question 3

A 28-year-old male sustains a spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture) and presents with a newly identified wrist drop. The injured nerve travels through the spiral groove in direct company with which vascular structure?

Explanation

The radial nerve courses through the spiral groove of the humerus accompanied by the profunda brachii artery. Injury here typically results in a radial nerve palsy, characteristic of Holstein-Lewis fractures.

Question 4

During an anterior intrapelvic (modified Stoppa) approach for a complex acetabular fracture, massive hemorrhage occurs while dissecting bluntly over the superior pubic ramus. This bleeding most likely originates from an anastomosis between which two vascular systems?

Explanation

The 'corona mortis' is a critical vascular anastomosis between the external iliac (or inferior epigastric) and obturator vessels. It crosses the superior pubic ramus and is highly vulnerable during the modified Stoppa or ilioinguinal approaches.

Question 5

A 32-year-old unrestrained driver presents with a shortened, adducted, and internally rotated right leg following a motor vehicle accident. Post-reduction CT shows a 3 mm incarcerated intra-articular acetabular fragment. What is the most critical rationale for urgent surgical extraction?

Explanation

Incarcerated intra-articular fragments following a posterior hip dislocation prevent congruent reduction, creating excessive focal capsular tension and mechanical joint destruction. Urgent arthrotomy or arthroscopy is required to prevent rapid chondrolysis and minimize AVN risk.

Question 6

During an extensile posterior approach utilizing an olecranon osteotomy for a comminuted distal humerus fracture (AO/OTA 13C3), the surgeon isolates the ulnar nerve. Which vascular structure typically accompanies the ulnar nerve as it passes posterior to the medial epicondyle?

Explanation

The superior ulnar collateral artery branches from the brachial artery and pierces the medial intermuscular septum to accompany the ulnar nerve posterior to the medial epicondyle.

Question 7

An 80-year-old female sustains a reverse obliquity intertrochanteric proximal femur fracture (AO/OTA 31-A3). Why is a cephalomedullary nail biomechanically superior to a sliding hip screw for this specific fracture pattern?

Explanation

In reverse obliquity fractures, the intact medial cortex combined with a compromised lateral wall means a sliding hip screw will allow the femoral shaft to medialize excessively. An intramedullary nail acts as an internal lateral buttress, preventing this displacement.

Question 8

In the treatment of a 12-year-old's femoral shaft fracture, utilization of a piriformis fossa entry portal for rigid intramedullary nailing is contraindicated. Which specific vascular structure is jeopardized by this starting point?

Explanation

A piriformis fossa entry point in skeletally immature patients carries a high risk of iatrogenic avascular necrosis. It directly threatens the deep branch of the medial circumflex femoral artery at the posterosuperior femoral neck.

Question 9

A surgeon performs an anterolateral approach to the distal humerus to plate a shaft fracture. During deep dissection separating the brachialis from the brachioradialis, which nerve-artery combination must be carefully identified and protected?

Explanation

In the anterolateral approach to the distal humerus, the interval is between the brachialis (musculocutaneous/radial nerves) and brachioradialis (radial nerve). The radial nerve and the accompanying radial recurrent artery must be protected here.

Question 10

A 35-year-old male sustains a posterior hip dislocation with an associated femoral head fracture occurring inferior to the fovea capitis, alongside a posterior wall acetabular fracture (Pipkin IV). What is the primary anatomical explanation for the high rate of avascular necrosis in this injury?

Explanation

Posterior hip dislocations, particularly those associated with severe trauma like Pipkin IV fractures, stretch and tear the posterior capsule and the ascending retinacular branches of the medial circumflex femoral artery, leading to AVN.

Question 11

A 72-year-old female presents with a 4-part proximal humerus fracture featuring medial calcar comminution and significant lateral head displacement. She has a known history of severe, symptomatic rotator cuff arthropathy. Which surgical option is most appropriate?

Explanation

Reverse total shoulder arthroplasty is indicated for elderly patients with complex 4-part proximal humerus fractures, especially those with pre-existing rotator cuff arthropathy, as it relies on deltoid function and bypasses the high risk of head AVN and tuberosity nonunion.

Question 12

During a minimally invasive plate osteosynthesis (MIPO) via an anterior approach for a humeral shaft fracture, the plate is passed submuscularly beneath the brachialis. Which structure is at greatest risk of impingement if the plate drifts excessively medial in the mid-arm?

Explanation

In an anterior MIPO approach to the humerus, medial deviation of the plate or instrumentation risks injury to the brachial artery and median nerve, which course medial to the biceps and brachialis muscles.

Question 13

A 28-year-old male arrives in the trauma bay with his right lower extremity fixed in extension, external rotation, and abduction. A superior (pubic) anterior hip dislocation is confirmed. What is the most critical immediate local vascular risk to evaluate?

Explanation

Superior (pubic) anterior hip dislocations force the femoral head anteriorly and superiorly, placing it in direct proximity to the femoral neurovascular bundle, creating a high risk for common femoral artery and vein compression or laceration.

Question 14

During a Kocher-Langenbeck approach for a posterior wall acetabular fracture, the gluteus maximus is split bluntly in line with its fibers. To preserve the primary vascular supply to the superior portion of the gluteus maximus, which vessel must be protected from over-retraction?

Explanation

The superior gluteal artery exits the greater sciatic foramen superior to the piriformis and supplies the proximal/superior half of the gluteus maximus. Excessive medial retraction or proximal splitting risks tearing this friable vessel.

Question 15

Recent anatomical studies regarding the vascular supply of the proximal humerus demonstrate that the predominant blood supply to the humeral head is provided by which of the following vessels?

Explanation

Classic teaching highlighted the anterior humeral circumflex artery as the primary supply via its arcuate branch. However, recent quantitative studies prove the posterior humeral circumflex artery provides approximately 64% of the blood supply to the humeral head.

Question 16

During a posterior approach to the hip, protecting the deep branch of the medial femoral circumflex artery (MFCA) is critical to prevent avascular necrosis. Anatomically, this vessel consistently runs between which two muscles before entering the capsule?

Explanation

The deep branch of the MFCA consistently travels posterior to the obturator externus and anterior to the quadratus femoris. Protecting the obturator externus and the inferior border of the quadratus femoris ensures the preservation of this vital vessel.

Question 17

A 35-year-old male presents with a closed distal-third spiral fracture of the humeral shaft. Following closed reduction and splinting in the emergency department, he develops a new-onset complete wrist drop and inability to extend his metacarpophalangeal joints. What is the most appropriate next step in management?

Explanation

A secondary radial nerve palsy that develops after a closed reduction of a distal-third spiral humeral shaft fracture (Holstein-Lewis) strongly suggests iatrogenic nerve entrapment. This is an absolute indication for immediate surgical exploration and internal fixation.

Question 18

In the treatment of an intertrochanteric femoral fracture, preoperative templating demonstrates a lateral wall thickness of 18 mm. Which of the following is the most appropriate fixation construct to minimize the risk of mechanical failure?

Explanation

A lateral wall thickness of less than 20.5 mm in an intertrochanteric fracture defines an incompetent lateral wall. Using a sliding hip screw in this setting carries a high rate of lateral wall blowout, making a cephalomedullary nail the treatment of choice.

Question 19

A 28-year-old polytrauma patient sustains a floating elbow injury with an associated brachial artery transection resulting in an ischemic, pulseless hand. What is the correct sequence of surgical management?

Explanation

In an ischemic limb with highly unstable fractures, a temporary intravascular shunt must be placed first to quickly restore perfusion. This is followed by stable skeletal fixation, definitive arterial repair, and prophylactic fasciotomies.

Question 20

A 40-year-old male sustains a posterior hip dislocation with an associated femoral head fracture (Pipkin IV). A surgical dislocation of the hip (Ganz approach) is planned. To preserve the MFCA blood supply to the femoral head, the trochanteric flip osteotomy must keep which muscle attachments intact on the greater trochanter?

Explanation

The Ganz trochanteric flip osteotomy meticulously preserves the insertions of the gluteus medius, gluteus minimus, and vastus lateralis on the trochanteric fragment. The external rotators remain intact on the femur, thereby protecting the deep branch of the MFCA.

Question 21

During a lateral approach to the distal humerus, the surgeon must identify and protect the radial nerve. Anatomically, at what average distance from the lateral epicondyle does the radial nerve pierce the lateral intermuscular septum to enter the anterior compartment of the arm?

Explanation

The radial nerve pierces the lateral intermuscular septum to pass from the posterior to the anterior compartment approximately 10 cm (range 9-12 cm) proximal to the lateral epicondyle. Identifying this precise anatomic landmark is crucial for safe distal humerus exposures.

Question 22

A 25-year-old male sustains a high-energy Pauwels type III femoral neck fracture. Which of the following internal fixation constructs provides the highest biomechanical stability against vertical shear forces?

Explanation

Pauwels type III fractures are highly unstable vertically due to their steep shear angle. Biomechanical studies consistently show that a fixed-angle construct, such as a sliding hip screw with an anti-rotation screw, provides superior stability against vertical shear compared to cancellous screws alone.

Question 23

A patient undergoes an ilioinguinal approach for an anterior column acetabular fracture. Severe hemorrhage is encountered over the posterior aspect of the superior pubic ramus. This bleeding is most likely originating from the Corona Mortis, which is an anastomosis between which two vascular systems?

Explanation

The Corona Mortis is a life-threatening vascular anastomosis between the external iliac (or inferior epigastric) system and the obturator (internal iliac) system. It is reliably found traversing the posterior aspect of the superior pubic ramus, averaging 5 cm from the symphysis pubis.

Question 24

An elderly patient with a highly comminuted intra-articular distal humerus fracture undergoes total elbow arthroplasty with an ulnar nerve transposition. Which blood vessel, which reliably supplies the ulnar nerve in the cubital tunnel, must be carefully managed to avoid nerve ischemia?

Explanation

The superior ulnar collateral artery reliably travels with the ulnar nerve posterior to the medial intermuscular septum and serves as its primary blood supply in the cubital tunnel. Its careful preservation during neurolysis minimizes ischemic ulnar neuropathy.

Question 25

A 30-year-old male sustains a posterior hip dislocation. Post-reduction examination reveals complete weakness in ankle dorsiflexion and great toe extension, but normal ankle plantar flexion. Which specific nerve structure is injured, and what is its most common anatomic relationship to the piriformis muscle?

Explanation

Posterior hip dislocations most commonly selectively injure the common peroneal division of the sciatic nerve. Anatomically, in the majority of the population (approx. 85%), both divisions of the sciatic nerve exit the pelvis together inferior to the piriformis muscle.

Question 26

Following a displaced subcapital femoral neck fracture, avascular necrosis frequently occurs due to the disruption of retinacular vessels. Which specific group of retinacular vessels provides the primary terminal blood supply to the weight-bearing dome of the femoral head?

Explanation

The posterosuperior retinacular vessels are the terminal branches of the deep branch of the MFCA. They course along the posterosuperior femoral neck to supply the critical weight-bearing superior dome of the femoral head.

Question 27

Which of the following vessels provides the primary blood supply to the adult femoral head and is most at risk during a posterior approach to the hip?

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) provides the predominant blood supply to the adult femoral head. It courses posterior to the femoral neck, making it highly vulnerable during posterior surgical approaches and posterior hip dislocations.

Question 28

A 35-year-old male sustains a Holstein-Lewis fracture of the humerus. Which nerve is most classically at risk for neuropraxia or entrapment in this specific injury pattern?

Explanation

A Holstein-Lewis fracture is a spiral fracture of the distal third of the humeral shaft. It is classically associated with radial nerve injury as the nerve passes through the lateral intermuscular septum and can become entrapped by the fracture fragments.

Question 29

A patient presents to the emergency department after a motor vehicle collision with a right hip dislocation. The affected leg is shortened, flexed, adducted, and internally rotated. Which nerve is at highest risk of injury in this scenario?

Explanation

The clinical presentation describes a posterior hip dislocation, which accounts for up to 90% of all hip dislocations. The sciatic nerve, particularly its peroneal division, is positioned immediately posterior to the hip joint and is at highest risk of traumatic injury.

Question 30

Based on recent quantitative vascular studies, which artery is now recognized as providing the majority of the blood supply to the humeral head, challenging classic anatomical teaching?

Explanation

While classic teaching emphasized the anterior circumflex humeral artery (arcuate branch), recent quantitative studies using MRI and cadaveric dissection demonstrate that the posterior circumflex humeral artery actually provides approximately 64% of the blood supply to the humeral head.

Question 31

A 75-year-old community-dwelling female sustains a non-displaced, valgus-impacted femoral neck fracture (Garden I). Which of the following is the most appropriate definitive management?

Explanation

For non-displaced or valgus-impacted femoral neck fractures (Garden I and II) in the elderly, in situ fixation with multiple cannulated screws is the standard of care. It minimizes surgical morbidity while effectively preventing secondary displacement.

Question 32

During an olecranon osteotomy approach for open reduction and internal fixation of a complex intra-articular distal humerus fracture, which nerve must be routinely identified and protected or transposed?

Explanation

The ulnar nerve courses directly posterior to the medial epicondyle in the cubital tunnel. It must be carefully identified, mobilized, and often anteriorly transposed to avoid iatrogenic injury during a posterior olecranon osteotomy approach to the distal humerus.

Question 33

In the Pipkin classification of femoral head fractures associated with posterior hip dislocations, which description accurately defines a Type II fracture?

Explanation

A Pipkin Type II fracture involves a posterior hip dislocation with a femoral head fracture that extends cephalad to the fovea capitis. Because it involves the major weight-bearing dome, it often requires operative fixation to restore joint congruity.

Question 34

Which of the following clinical scenarios represents an absolute indication for immediate operative fixation of a humeral shaft fracture?

Explanation

Open humeral shaft fractures represent an absolute indication for surgical management to allow for thorough debridement, irrigation, and stable fixation. Primary radial nerve palsy before reduction is generally observed, as the majority of cases are neuropraxias that spontaneously recover.

Question 35

The trochanteric anastomosis provides a crucial extracapsular collateral circulation to the hip joint. Which of the following sets of arteries primarily form this vascular ring?

Explanation

The trochanteric anastomosis is formed by the descending branch of the superior gluteal artery, the inferior gluteal artery, and the ascending branches of both the medial and lateral femoral circumflex arteries.

Question 36

According to the Neer classification for proximal humerus fractures, what criteria must be met for a fracture segment to be considered a separate, "displaced" part?

Explanation

The Neer classification defines a "part" as displaced if there is greater than 1 cm of separation or greater than 45 degrees of angulation between the fracture fragments relative to their normal anatomical position.

Question 37

When evaluating an intertrochanteric hip fracture, which anatomical feature is the most critical determinant of fracture stability following internal fixation?

Explanation

The integrity of the posteromedial cortex, often referred to as the calcar, is the most critical determinant of stability in intertrochanteric fractures. It functions as a primary buttress against compressive forces, and its loss leads to varus collapse and implant failure.

Question 38

In the posterior compartment of the arm, the profunda brachii (deep brachial) artery travels in intimate association with which of the following nerves?

Explanation

The profunda brachii artery travels alongside the radial nerve through the spiral groove in the posterior compartment of the arm. Both structures are vulnerable to injury in midshaft humerus fractures and lateral surgical approaches.

Question 39

During surgical approaches to the anterior acetabulum, the "Corona Mortis" is a significant vascular hazard. Which of the following best describes this structure?

Explanation

The corona mortis (crown of death) is a highly variable vascular anastomosis between the obturator system and the external iliac or inferior epigastric vessels. It crosses over the superior pubic ramus and is at severe risk of catastrophic bleeding during anterior intrapelvic approaches.

Question 40

A 40-year-old female presents with an isolated coronal shear fracture of the capitellum involving a large segment of subchondral bone. How is this fracture classified according to the Bryan and Morrey system?

Explanation

A Bryan and Morrey Type I fracture, also known as a Hahn-Steinthal fracture, involves a large coronal shear fracture of the capitellum that includes a significant portion of subchondral bone. Type II (Kocher-Lorenz) involves an articular cartilage sleeve with very little bone.

Question 41

During a standard deltopectoral approach to the proximal humerus, meticulous retraction must be used near the coracoid process. Where does the axillary nerve course relative to the conjoint tendon?

Explanation

The axillary nerve courses inferior to the conjoint tendon as it travels from the posterior cord of the brachial plexus toward the quadrilateral space. Aggressive retraction inferior to the coracoid process places the axillary nerve at significant risk for neuropraxia.

Question 42

In a completely displaced subtrochanteric femur fracture, the proximal fracture fragment undergoes predictable multiplanar deformation. Which set of deforming forces accurately describes the position of the proximal fragment?

Explanation

The proximal fragment in a subtrochanteric fracture is characteristically flexed by the iliopsoas, abducted by the gluteus medius and minimus, and externally rotated by the short external rotators. Recognizing these forces is critical for achieving an accurate reduction.

Question 43

A 6-year-old child sustains a completely displaced supracondylar humerus fracture. On examination, the hand is pink but lacks a palpable radial pulse. Capillary refill is less than 2 seconds. What is the most appropriate initial management?

Explanation

For a "pink, pulseless" hand following a supracondylar fracture, the initial step is urgent closed reduction and percutaneous pinning. Restoration of skeletal alignment relieves kinking of the brachial artery, which frequently restores palpable pulses without the need for open vascular exploration.

Question 44

The anterior (Smith-Petersen) approach to the hip is a true internervous plane. Which two muscles form the superficial surgical interval for this approach?

Explanation

The superficial internervous plane of the anterior (Smith-Petersen) approach is between the sartorius, which is innervated by the femoral nerve, and the tensor fasciae latae (TFL), which is innervated by the superior gluteal nerve.

Question 45

Following locked plate fixation of a proximal humerus fracture, what is the most common biomechanical cause of subsequent varus collapse and secondary screw cut-out?

Explanation

Inadequate medial support, often due to a failure to restore the medial calcar hinge or failure to place an inferomedial calcar screw, is the primary biomechanical cause of varus collapse and hardware cut-out following locked plating of proximal humerus fractures.

Question 46

To significantly decrease the incidence of avascular necrosis (AVN) of the femoral head following a traumatic posterior hip dislocation, within what critical time frame should the hip be ideally reduced?

Explanation

Expeditious reduction of a traumatic hip dislocation within 6 hours is critically important. Prolonged dislocation beyond 6 hours significantly increases the risk of avascular necrosis due to sustained disruption or kinking of the vulnerable intracapsular blood supply.

Question 47

A 35-year-old male sustains a posterior hip dislocation in a motor vehicle collision. Which of the following arteries provides the primary blood supply to the adult femoral head and is most at risk in this injury?

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) provides the predominant blood supply to the adult femoral head. It is particularly vulnerable to stretching or tearing during a posterior hip dislocation.

Question 48

During a posterior approach to the humerus for internal fixation of a distal third shaft fracture, the surgeon visualizes the radial nerve. Which vascular structure runs directly with the radial nerve in the spiral groove?

Explanation

The profunda brachii (deep brachial) artery travels with the radial nerve through the spiral groove of the posterior humerus. It subsequently divides into the radial collateral and middle collateral arteries.

Question 49

A 28-year-old female presents with a Pipkin Type II femoral head fracture following trauma. Which of the following best describes this specific fracture pattern?

Explanation

In the Pipkin classification, Type I is below the fovea, while Type II extends superior to the fovea capitis, involving the critical weight-bearing portion of the femoral head. Types III and IV involve associated neck or acetabular fractures, respectively.

Question 50

A 40-year-old male sustains a closed spiral fracture of the distal third of the humerus. On initial exam, radial nerve function is intact. Following closed reduction and splinting, he develops a complete radial nerve palsy. What is the most appropriate next step in management?

Explanation

A secondary radial nerve palsy that develops following closed reduction of a humeral shaft fracture (especially a Holstein-Lewis variant) is a classic indication for immediate surgical exploration. The nerve may be entrapped in the fracture site during the reduction maneuver.

Question 51

During an anterior intrapelvic (modified Stoppa) approach for an acetabular fracture, significant hemorrhage occurs near the superior pubic ramus. This is most likely due to injury to the "corona mortis", which is an anastomosis between which two vascular systems?

Explanation

The "corona mortis" is a vascular anastomosis between the external iliac (or inferior epigastric) and the obturator vessels. It lies on the posterior aspect of the superior pubic ramus and is highly vulnerable during anterior intrapelvic approaches.

Question 52

Recent anatomical studies have redefined the primary blood supply to the proximal humerus. Which of the following vessels is now considered to supply the majority of the humeral head?

Explanation

Historically, the anterior humeral circumflex artery (via the arcuate artery) was thought to provide the main blood supply. However, recent quantitative studies demonstrate that the posterior humeral circumflex artery supplies up to 64% of the humeral head.

Question 53

A 75-year-old female sustains a highly comminuted distal humerus fracture with severe osteopenia. Which of the following factors most strongly supports the use of Total Elbow Arthroplasty (TEA) over Open Reduction and Internal Fixation (ORIF)?

Explanation

The primary indication for TEA in elderly patients with distal humerus fractures is poor bone quality and comminution precluding stable ORIF. Stable fixation is absolutely essential for early range of motion to prevent profound elbow stiffness.

Question 54

A 22-year-old male is evaluated for an intertrochanteric hip fracture. Preoperative radiographs reveal a significantly comminuted lateral wall. What is the biomechanical consequence of this finding if treated with a standard sliding hip screw (SHS)?

Explanation

Loss of lateral wall integrity converts an intertrochanteric fracture into a highly unstable pattern. Using an SHS in this setting permits excessive medialization of the shaft, leading to high rates of construct failure and malunion.

Question 55

In the management of a Type III pediatric supracondylar humerus fracture, after closed reduction and pinning, the patient's hand remains a "pink, pulseless hand". Capillary refill is less than 2 seconds. What is the most appropriate next step?

Explanation

A "pink, pulseless hand" with excellent perfusion (capillary refill <2 seconds) after reduction and pinning typically indicates vascular spasm rather than complete occlusion. The standard of care is close inpatient observation, as the pulse often returns within 24 to 48 hours.

Question 56

A 30-year-old male falls from a height and sustains a vertical shear femoral neck fracture (Pauwels Type III). What is the predominant biomechanical force acting across the fracture site?

Explanation

Pauwels Type III femoral neck fractures feature a fracture line angle greater than 50 degrees from the horizontal. This steep angle subjects the fracture site to incredibly high shear forces, increasing the risk of varus collapse and nonunion.

Question 57

When performing a Smith-Petersen (anterior) approach to the hip, which internervous plane is utilized for the superficial dissection?

Explanation

The Smith-Petersen approach utilizes the superficial internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 58

A patient with a comminuted proximal humerus fracture undergoes an open reduction internal fixation (ORIF). Disruption of the medial hinge (calcar) is noted intraoperatively. What is the primary complication associated with failure to restore the medial calcar?

Explanation

The medial calcar provides crucial structural support to the proximal humerus. Failure to restore medial cortical contact or utilize calcar screws leads to a high risk of varus collapse, resulting in hardware penetration into the glenohumeral joint.

Question 59

An anteroposterior radiograph of a pelvis shows a "spur sign" on the obturator oblique view. This radiographic finding is pathognomonic for which type of acetabular fracture?

Explanation

The "spur sign" is pathognomonic for a both-column acetabular fracture. It represents the intact strut of the ilium that remains attached to the axial skeleton, protruding posterosuperiorly relative to the medially displaced articular fragments.

Question 60

Which of the following arteries provides the predominant blood supply to the weight-bearing portion of the femoral head in an adult?

Explanation

The deep branch of the medial circumflex femoral artery (MFCA) is the primary blood supply to the adult femoral head. It supplies the superior, weight-bearing aspect of the head via the lateral epiphyseal artery. Disruption of this vessel in femoral neck fractures highly increases the risk of avascular necrosis.

Question 61

Recent quantitative anatomical studies have demonstrated that the predominant blood supply to the humeral head is derived from which of the following vessels?

Explanation

Historically, the anterior circumflex humeral artery (arcuate branch) was thought to be the primary supply. However, recent quantitative injection studies demonstrate that the posterior circumflex humeral artery provides the overwhelming majority of the blood supply to the humeral head.

Question 62

A 25-year-old male sustains a high-energy Pauwels type III femoral neck fracture. To biomechanically resist the high shear forces associated with this fracture pattern, which of the following internal fixation constructs is most appropriate?

Explanation

Pauwels type III fractures are characterized by a vertical fracture line that is highly unstable due to significant shear forces. A fixed-angle device such as a dynamic hip screw (with an anti-rotation screw) provides superior biomechanical stability against shear compared to multiple parallel cancellous screws.

Question 63

A 35-year-old sustains a closed, spiral fracture of the distal third of the humeral shaft. Initial exam shows intact radial nerve function. Following closed reduction and splinting, the patient develops a complete wrist drop. What is the most appropriate next step in management?

Explanation

A secondary radial nerve palsy that develops after closed reduction of a humeral shaft fracture is an indication for immediate surgical exploration. This presentation suggests the nerve may have become entrapped within the fracture site during the reduction maneuver.

Question 64

An 80-year-old female presents with a reverse oblique intertrochanteric femur fracture (OTA 31-A3). Biomechanically, why is a cephalomedullary nail preferred over a sliding hip screw (SHS) for this specific fracture pattern?

Explanation

Reverse oblique intertrochanteric fractures lack a competent lateral wall to buttress the proximal fragment. If an SHS is used, the proximal fragment tends to slide laterally while the shaft medializes, leading to fixation failure, making a cephalomedullary nail the implant of choice.

Question 65

According to Hertel's criteria, which of the following radiographic findings is a strong predictor of humeral head ischemia following a proximal humerus fracture?

Explanation

Hertel described several predictors for humeral head ischemia, including a metaphyseal head extension (calcar length) of less than 8 mm, disruption of the medial hinge greater than 2 mm, and an anatomic neck fracture pattern. These factors indicate severe disruption of the vascular supply.

Question 66

During a posterior approach to the hip, aggressive release of the quadratus femoris muscle insertion on the proximal femur puts which of the following vascular structures at greatest risk?

Explanation

The deep branch of the medial circumflex femoral artery runs anterior to the quadratus femoris and posterior to the obturator externus. Aggressive release or division of the quadratus femoris too close to its femoral insertion can easily sever this vital artery, jeopardizing the femoral head blood supply.

Question 67

When performing a transolecranon approach for a complex distal humerus fracture, an apex-distal chevron osteotomy is often preferred over a simple transverse osteotomy primarily to:

Explanation

An apex-distal chevron osteotomy provides a larger surface area for bone healing and confers inherent rotational and translational stability compared to a transverse osteotomy. This interlocking geometry aids in accurate anatomic reduction when repairing the olecranon.

Question 68

A 40-year-old male sustains a traumatic posterior hip dislocation. Following closed reduction, he exhibits foot drop and an inability to actively extend his great toe. Which division of the sciatic nerve is most commonly injured in this scenario, and what sensory deficit is expected?

Explanation

The sciatic nerve is injured in 10-20% of posterior hip dislocations. The peroneal (fibular) division is far more susceptible to stretch injury due to its lateral position and secure tethering at the fibular neck, leading to foot drop and dorsal foot/first web space sensory loss.

Question 69

During a deltopectoral approach for open reduction and internal fixation of a proximal humerus fracture, the surgeon encounters the 'three sisters'. These structures consist of two venae comitantes and which of the following arteries?

Explanation

The 'three sisters' refer to the anterior circumflex humeral artery and its two accompanying veins. They are consistently found running transversely across the inferior border of the subscapularis muscle and often require ligation to mobilize the subscapularis.

Question 70

A patient presents with a posterior hip dislocation and an associated fracture of the femoral head that extends cephalad to the fovea capitis. According to the Pipkin classification, what type of fracture is this, and what is the primary indication for surgical fixation?

Explanation

A Pipkin II fracture involves the femoral head superior to the fovea capitis, which includes the primary weight-bearing surface. Open reduction and internal fixation is indicated if the fragment is displaced to restore joint congruity and prevent post-traumatic arthritis.

Question 71

In a displaced surgical neck fracture of the humerus, the proximal shaft is typically displaced anteromedially. Which muscle is the primary deforming force responsible for this specific displacement?

Explanation

In surgical neck fractures, the pectoralis major acts as the primary deforming force on the humeral shaft, pulling it medially and anteriorly. Meanwhile, the proximal fragment remains neutral or abducted due to the balanced pull of the rotator cuff muscles.

Question 72

During an anterior intrapelvic (modified Stoppa) approach for an acetabular fracture, significant hemorrhage occurs near the superior pubic ramus. This is most likely due to injury to the 'corona mortis', which is an anastomosis between the:

Explanation

The 'corona mortis' (crown of death) is a highly variable vascular anastomosis between the external iliac system (usually via inferior epigastric vessels) and the internal iliac system (obturator vessels). It crosses the superior pubic ramus and is highly vulnerable during anterior pelvic surgical approaches.

Question 73

When performing a lateral approach to the distal humerus, understanding the course of the radial nerve is critical. On average, at what distance proximal to the lateral epicondyle does the radial nerve pierce the lateral intermuscular septum to enter the anterior compartment?

Explanation

The radial nerve courses from posterior to anterior by piercing the lateral intermuscular septum on average 10-12 cm proximal to the lateral epicondyle. Identifying this landmark is essential to safely dissect and protect the nerve during lateral or anterolateral approaches.

Question 74

In a classical subtrochanteric femur fracture, the proximal fragment assumes a predictable deformed position. Which combination of muscles is primarily responsible for the flexion, abduction, and external rotation of the proximal fragment?

Explanation

The iliopsoas flexes the proximal fragment, the gluteus medius and minimus abduct it, and the short external rotators externally rotate it. Overcoming these deforming forces is critical for achieving anatomic reduction during intramedullary nailing.

Question 75

A 45-year-old female presents with an atrophic nonunion 8 months after sustaining a transverse middle-third humeral shaft fracture treated initially with functional bracing. She has no nerve deficits. What is the most reliable definitive surgical management?

Explanation

The gold standard for an atrophic humeral shaft nonunion is open reduction and internal fixation using rigid compression plating coupled with autologous bone grafting. This addresses both the mechanical instability and the biological deficiency characteristic of atrophic nonunions.

Question 76

A 72-year-old female sustains a 4-part proximal humerus fracture. According to the Hertel criteria, which of the following radiographic findings is the most reliable predictor of subsequent humeral head ischemia?

Explanation

The Hertel criteria identify predictors of humeral head ischemia, most notably a metaphyseal head extension (calcar length) of less than 8 mm and a medial hinge disruption of greater than 2 mm. These findings suggest severe disruption of the critical medial periosteal blood supply.

Question 77

During open reduction and internal fixation of a posterior glenoid rim fracture via a classic posterior approach, the surgeon dissects near the quadrangular space. Which vascular structure passes through this space alongside the axillary nerve?

Explanation

The posterior circumflex humeral artery travels with the axillary nerve through the quadrangular space. This space is bordered by the teres minor (superior), teres major (inferior), long head of the triceps (medial), and surgical neck of the humerus (lateral).

Question 78

An orthopedic surgeon is performing an ilioinguinal approach for an anterior column acetabular fracture. Severe hemorrhage occurs over the superior pubic ramus near the symphysis. This bleeding is most likely due to injury of the corona mortis, which represents an anastomosis between which two vascular systems?

Explanation

The corona mortis is a vascular anastomosis between the external iliac (or its inferior epigastric branch) and the obturator vessels. It is located on the posterior aspect of the superior pubic ramus and is highly vulnerable during anterior intrapelvic approaches.

Question 79

When performing a surgical dislocation of the hip via a trochanteric flip osteotomy, the deep branch of the medial femoral circumflex artery (MFCA) must be protected. To preserve this vessel, the osteotomy must exit proximal to which of the following structures?

Explanation

The deep branch of the MFCA runs superior to the quadratus femoris. Ensuring the trochanteric osteotomy exits proximal to the insertion of the quadratus femoris protects this vital vascular supply to the femoral head.

Question 80

A 6-year-old child presents with a grossly displaced extension-type supracondylar humerus fracture. Following closed reduction and percutaneous pinning, the hand is pink and capillary refill is less than 2 seconds, but the radial pulse remains completely absent. What is the most appropriate next step in management?

Explanation

According to AAOS guidelines, a 'pink, pulseless hand' following satisfactory reduction and pinning of a supracondylar fracture indicates adequate collateral perfusion. The standard of care is close observation and admission, as pulses typically return over time.

Question 81

During a deltopectoral approach for proximal humerus plating, the cephalic vein is identified. To preserve the primary venous drainage of the deltoid muscle and minimize bleeding, the vein is typically retracted in which direction, and which artery's branch travels in this same interval?

Explanation

The cephalic vein receives numerous small tributaries from the deltoid muscle. Therefore, it is typically retracted laterally with the deltoid to prevent avulsing these branches, taking care to preserve the deltoid branch of the thoracoacromial artery.

Question 82

The main blood supply to the adult femoral head is derived from the deep branch of the medial femoral circumflex artery (MFCA). At what key anatomical location does the MFCA cross the obturator externus muscle?

Explanation

The deep branch of the MFCA travels anterior to the superior gemellus and obturator internus but constantly crosses posterior to the obturator externus tendon. This relationship makes the vessel vulnerable during posterior approaches if the obturator externus is violated.

Question 83

An 80-year-old female presents with an anterior shoulder dislocation and an expanding axillary hematoma. A traction injury to the axillary artery is suspected. The axillary artery is formally divided into three distinct anatomical parts by which of the following structures?

Explanation

The axillary artery is anatomically divided into three segments based on its relationship to the pectoralis minor muscle. The first part is medial, the second part lies posterior, and the third part lies lateral to the pectoralis minor.

Question 84

A patient undergoes selective embolization for an actively bleeding subtrochanteric fracture. The interventional radiologist notes robust collateral flow through the cruciate anastomosis of the thigh. Which of the following arteries is NOT a direct contributor to this anastomotic network?

Explanation

The cruciate anastomosis of the proximal thigh is formed by the inferior gluteal artery, the transverse branches of the medial and lateral femoral circumflex arteries, and the first perforating branch of the profunda femoris. The superior gluteal artery does not participate.

Question 85

During an anterolateral approach to the distal humeral shaft, the surgeon longitudinally splits the brachialis muscle. What is the primary anatomic rationale for ensuring the lateral half of the brachialis remains intact against the bone?

Explanation

The radial nerve runs between the brachialis and the brachioradialis. Splitting the brachialis longitudinally allows the lateral portion of the muscle to serve as a protective soft-tissue cushion between the hardware and the radial nerve.

Question 86

A 35-year-old sustains a comminuted subtrochanteric femur fracture. Biological plating is planned. The surgeon must be cautious of the perforating branches of the profunda femoris. Between which two muscular structures do these perforators typically pass to reach the posterior compartment of the thigh?

Explanation

The perforating branches of the profunda femoris artery travel posterolaterally by piercing the tendinous insertions of the adductor magnus and the vastus lateralis near the linea aspera.

Question 87

During a medial approach to the humerus for vascular exploration, the medial intermuscular septum is encountered. The ulnar nerve passes from the anterior to the posterior compartment by piercing this septum. Which vascular structure typically accompanies the ulnar nerve through this septum?

Explanation

The superior ulnar collateral artery originates from the brachial artery and reliably pierces the medial intermuscular septum alongside the ulnar nerve to enter the posterior compartment of the arm.

Question 88

A 24-year-old male suffers a posterior hip dislocation. Reduction is performed 8 hours post-injury. Which pathophysiological mechanism most directly contributes to the high risk of femoral head osteonecrosis in this specific clinical scenario?

Explanation

Osteonecrosis following posterior hip dislocation is primarily driven by direct mechanical stretching, kinking, or intimal tearing of the deep branch of the medial femoral circumflex artery (MFCA) during the dislocation event.

Question 89

A 35-year-old male requires open reduction and internal fixation of a Pipkin Type II femoral head fracture. The surgeon elects to use an anterior (Smith-Petersen) approach. Which vascular structure consistently crosses the internervous plane of this approach and typically requires ligation?

Explanation

The Smith-Petersen (anterior) approach utilizes the internervous plane between the sartorius (femoral nerve) and tensor fascia lata (superior gluteal nerve). The ascending branch of the lateral circumflex femoral artery transversely crosses this plane and usually requires ligation to achieve adequate deep exposure without tearing.

Question 90

A 68-year-old female undergoes open reduction and internal fixation of a 3-part proximal humerus fracture via a deltopectoral approach. To safely mobilize the proximal fragment, the surgeon must be mindful of the axillary nerve. Which vascular structure courses with this nerve through the quadrangular space, and what are the boundaries of this space?

Explanation

The axillary nerve and posterior circumflex humeral artery exit the axilla posteriorly through the quadrangular space. The boundaries are the teres minor (superior), teres major (inferior), long head of the triceps (medial), and the surgical neck of the humerus (lateral).

Question 91

A 78-year-old female undergoes cephalomedullary nailing for an unstable intertrochanteric femur fracture. Postoperatively, she develops a progressively expanding pulsatile mass in the medial thigh and unexplained tachycardia. Injury to which vessel is most likely responsible, and what is the typical iatrogenic mechanism?

Explanation

Pseudoaneurysm of the profunda femoris artery is a classic vascular complication of cephalomedullary nailing for intertrochanteric fractures. It is most commonly caused by over-plunging of the drill bit or using screws that are too long during the placement of distal interlocking screws.

Question 92

A 6-year-old boy presents with a Gartland type III extension-type supracondylar humerus fracture. Examination reveals a pink, pulseless hand with intact capillary refill. Following closed reduction and percutaneous pinning, the radial pulse remains absent, but the hand remains pink and well-perfused. What is the most appropriate next step in management?

Explanation

In a pediatric supracondylar humerus fracture, a pink, pulseless hand following adequate closed reduction and pinning indicates sufficient collateral circulation. Current AAOS guidelines recommend close observation and admission rather than routine immediate vascular exploration, provided the hand remains well-perfused.

Question 93

A 30-year-old male presents with a displaced intracapsular femoral neck fracture. The decision is made to perform urgent open reduction and internal fixation. A capsulotomy is planned to decompress the intracapsular hematoma. To avoid compromising the remaining blood supply to the femoral head, what is the recommended orientation and location of the capsulotomy?

Explanation

A T-shaped or longitudinal capsulotomy along the anterior femoral neck allows for adequate hematoma decompression and direct visualization for fracture reduction. This approach safely avoids the critical lateral epiphyseal vessels, which are terminal branches of the medial circumflex femoral artery located in the posterosuperior retinaculum.

Orthopedic Board Review Set 675: 100 MCQs for ABOS, OITE, FRCS – Hip Focus

AAOS Orthopedic MCQs (Set 1): Hip & Humerus Trauma, Vascular Anatomy | 2026 Board Review

Key Takeaway

AAOS Orthopedic MCQs (Set 1): Hip & Humerus Trauma, Vascular Anatomy | 2026 Board Review

Chapter Index