Posterior Shoulder Instability MCQs | Ortho Board Review

Question 1

A 22-year-old collegiate offensive lineman presents with recurrent posterior shoulder instability. He has not had any frank dislocations but experiences subluxations when blocking. He wishes to pursue non-operative management. A physical therapy program is initiated. Which of the following muscle groups should be the primary focus of his strengthening program?

Explanation

Correct Answer: B

Conservative management of recurrent unidirectional posterior shoulder instability focuses heavily on strengthening the dynamic posterior stabilizers of the shoulder. These primarily include the external rotators (infraspinatus and teres minor) and the posterior head of the deltoid. Strengthening these muscles helps to dynamically resist posterior translation of the humeral head during provocative activities, such as blocking in football.

Question 2

A 28-year-old male presents to the emergency department after a motor vehicle collision. He was the restrained driver and his hands were on the steering wheel at the time of impact. He complains of severe left shoulder pain and an inability to move the arm. On examination, his arm is locked in internal rotation. Which of the following positions most commonly predisposes the shoulder to this type of dislocation?

Explanation

Correct Answer: B

Posterior shoulder dislocations classically occur when an axial load is applied to the arm while it is in a position of adduction, flexion, and internal rotation. This is the typical position of the arms when holding a steering wheel during a front-end motor vehicle collision (dashboard injury). It is also the mechanism seen in seizures and electrocution due to intense muscle contractions.

Question 3

A 35-year-old male with a history of poorly controlled epilepsy presents to the clinic with chronic right shoulder pain and limited range of motion following a seizure 3 weeks ago. He is unable to externally rotate his right shoulder past neutral. An AP radiograph of the shoulder reveals a symmetric appearance of the humeral head with loss of the normal half-moon overlap. Which of the following additional radiographic findings is most specific for his suspected diagnosis?

Explanation

Correct Answer: C

The patient has a missed posterior shoulder dislocation, which is a common complication following seizures. The AP radiograph describes the "lightbulb sign," which is a symmetric appearance of the humeral head due to fixed internal rotation. The "trough line sign" represents a reverse Hill-Sachs lesion (an impaction fracture of the anteromedial humeral head against the posterior glenoid rim), which is highly specific for a posterior dislocation.

Question 4

A 40-year-old male presents with a chronic, locked posterior shoulder dislocation that occurred during an electrocution injury 4 weeks ago. A CT scan reveals an anteromedial humeral head impaction fracture (reverse Hill-Sachs lesion) involving 35% of the articular surface. Which of the following surgical interventions is most appropriate?

Explanation

Correct Answer: C

For a reverse Hill-Sachs lesion involving 20% to 40% of the articular surface, the modified McLaughlin procedure is indicated. This involves the transfer of the lesser tuberosity with its attached subscapularis tendon into the anteromedial defect to prevent recurrent engagement of the defect on the posterior glenoid rim. Defects greater than 40-50% typically require arthroplasty.

Question 5

A 19-year-old weightlifter experiences posterior shoulder pain and a sensation of instability during the bench press. Clinical examination reveals a positive jerk test. Magnetic resonance arthrography (MRA) demonstrates a tear of the posterior labrum and capsule. Which of the following capsuloligamentous structures is the primary restraint to posterior translation of the humerus when the shoulder is flexed to 90 degrees and internally rotated?

Explanation

Correct Answer: D

The posterior band of the inferior glenohumeral ligament (IGHL) is the primary static restraint to posterior translation of the humeral head when the shoulder is in 90 degrees of flexion and internal rotation. Injury to this structure is a hallmark of recurrent posterior shoulder instability.

Question 6

A 24-year-old military recruit complains of vague posterior shoulder pain and clicking. The physician suspects posterior instability. During physical examination, the patient's arm is elevated to 90 degrees of forward flexion and internally rotated. The examiner then applies a posterior force to the elbow while horizontally adducting the arm, producing a clunk and sudden pain. As the arm is returned to the starting position, a second clunk is felt. What is the name of this provocative test?

Explanation

Correct Answer: B

The Jerk test evaluates for posterior shoulder instability. A positive test occurs when a posterior force is applied to the flexed, internally rotated arm, causing the humeral head to subluxate posteriorly over the glenoid rim (first clunk). As the arm is brought back into the coronal plane, the humeral head reduces back into the glenoid fossa (second clunk).

Question 7

A 21-year-old rugby player sustains a posterior shoulder dislocation after falling on an outstretched, internally rotated arm. Following closed reduction, an MRI is obtained. It reveals a detachment of the posterior labrum and posterior capsule from the glenoid rim. What is the eponymous name for this specific lesion?

Explanation

Correct Answer: C

A reverse Bankart lesion is an avulsion of the posterior labrum and posterior capsular complex from the posterior glenoid rim. It is the posterior equivalent of the classic anterior Bankart lesion and is commonly seen following a traumatic posterior shoulder dislocation.

Question 8

Posterior shoulder dislocations account for approximately 2-5% of all shoulder dislocations. While trauma is a common cause, non-traumatic etiologies are classically associated with this injury due to intense, uncoordinated muscle contractions. Which of the following muscles' overpowering force is primarily responsible for posterior dislocation during a seizure?

Explanation

Correct Answer: A

During a seizure or electrocution, the strong internal rotators of the shoulder (pectoralis major, latissimus dorsi, and subscapularis) overpower the relatively weaker external rotators (infraspinatus and teres minor). This massive, uncoordinated contraction forces the humeral head into severe internal rotation and drives it posteriorly out of the glenoid fossa.

Question 9

A 65-year-old female presents to the orthopedic clinic with a 3-month history of severe right shoulder pain and stiffness following a fall down the stairs. She was initially told she had a shoulder sprain. On examination, she has 0 degrees of external rotation and 45 degrees of forward elevation. Radiographs show a locked posterior dislocation with severe degenerative changes of the glenohumeral joint and a reverse Hill-Sachs lesion involving 50% of the articular surface. What is the most appropriate definitive management for this patient?

Explanation

Correct Answer: D

In a chronic, missed posterior dislocation with significant articular surface involvement (greater than 40-50%) and established glenohumeral osteoarthritis, total shoulder arthroplasty (or reverse total shoulder arthroplasty depending on rotator cuff status) is the treatment of choice. Joint-preserving procedures like the McLaughlin procedure are contraindicated in the setting of severe arthritis and massive osteochondral defects.

Question 10

A surgeon is performing an open posterior stabilization for recurrent posterior shoulder instability. The classic posterior approach to the shoulder utilizes an internervous plane. Which of the following describes the correct internervous plane for this approach?

Explanation

Correct Answer: B

The classic open posterior approach to the shoulder utilizes the true internervous plane between the infraspinatus (innervated by the suprascapular nerve) and the teres minor (innervated by the axillary nerve). This approach allows safe access to the posterior capsule and glenoid without denervating the posterior rotator cuff musculature.

Question 11

A 22-year-old collegiate offensive lineman presents with recurrent posterior shoulder instability. He has not experienced any frank dislocations but reports a sensation of the shoulder 'slipping out' posteriorly when blocking. MRI shows a nondisplaced posterior labral tear without significant glenoid bone loss. He elects to undergo conservative management. A targeted physical therapy program should primarily emphasize strengthening of which of the following muscle groups?

Explanation

Correct Answer: B

Conservative management of posterior shoulder instability focuses on strengthening the dynamic posterior stabilizers of the shoulder. These include the infraspinatus, teres minor, and the posterior head of the deltoid. Strengthening these muscles helps to dynamically resist posterior translation of the humeral head during provocative positions, such as when the arm is flexed, adducted, and internally rotated.

Question 12

A 35-year-old male is brought to the emergency department following a generalized tonic-clonic seizure. He complains of severe right shoulder pain and an inability to move the arm. On examination, the arm is locked in adduction and internal rotation. An axillary radiograph reveals a posterior shoulder dislocation. Which of the following osseous defects is most likely to be identified on advanced imaging?

Explanation

Correct Answer: C

Posterior shoulder dislocations are classically associated with seizures, electrocution, or high-energy trauma with the arm in a flexed, adducted, and internally rotated position. The classic osseous lesion associated with a posterior dislocation is the reverse Hill-Sachs lesion, which is an impaction fracture of the anteromedial aspect of the humeral head caused by the posterior glenoid rim. A standard Hill-Sachs lesion (posterolateral) is seen in anterior dislocations.

Question 13

A 40-year-old male presents with a locked posterior shoulder dislocation that occurred 3 weeks ago following an unrecognized seizure. CT scan demonstrates a reverse Hill-Sachs lesion involving 35% of the articular surface. Which of the following is the most appropriate surgical management for this osseous defect?

Explanation

Correct Answer: C

The management of a reverse Hill-Sachs lesion depends on the size of the articular defect. Defects <20% can often be managed with closed reduction and immobilization if stable. Defects between 20% and 40% are typically managed with a modified McLaughlin procedure, which involves the transfer of the lesser tuberosity (along with the attached subscapularis tendon) into the anteromedial humeral head defect to prevent engagement on the posterior glenoid rim. Defects >40-50% generally require hemiarthroplasty or total shoulder arthroplasty.

Question 14

A surgeon is performing an open posterior stabilization for recurrent posterior shoulder instability. The classic posterior approach to the shoulder utilizes an internervous plane between which of the following two muscles?

Explanation

Correct Answer: B

The classic posterior approach to the shoulder utilizes the internervous plane between the infraspinatus (innervated by the suprascapular nerve) and the teres minor (innervated by the axillary nerve). This plane allows safe access to the posterior capsule and glenohumeral joint while minimizing the risk of denervating the posterior rotator cuff musculature.

Question 15

A 24-year-old weightlifter presents with deep posterior shoulder pain and clicking. He has a positive Jerk test and a positive Kim test. MRI arthrogram reveals a concealed, incomplete avulsion of the posteroinferior labrum without capsular detachment. This specific pathology is best described as:

Explanation

Correct Answer: B

A Kim lesion is defined as a concealed, incomplete avulsion of the posteroinferior labrum. Unlike a reverse Bankart lesion, the posterior capsule remains attached to the glenoid, and the labrum is not completely detached, making it sometimes difficult to visualize from a standard anterior arthroscopic portal. The Kim test and Jerk test are highly sensitive and specific for posteroinferior labral pathology.

Question 16

During the physical examination of a 19-year-old male with suspected posterior shoulder instability, the examiner places the patient's arm in 90 degrees of abduction and internal rotation. The examiner then applies an axial load to the humerus while horizontally adducting the arm. A sudden clunk is felt as the humeral head subluxates posteriorly. As the arm is returned to the starting position, a second clunk is felt. This clinical test is known as the:

Explanation

Correct Answer: C

The Jerk test is used to evaluate for posterior shoulder instability. The patient's arm is abducted to 90 degrees and internally rotated. An axial load is applied to the humerus, and the arm is horizontally adducted. A positive test is indicated by a sudden clunk as the humeral head subluxates posteriorly off the glenoid. A second clunk may be felt as the arm is returned to the starting position and the humeral head reduces.

Question 17

In the abducted and internally rotated shoulder, which of the following capsuloligamentous structures is the primary static restraint to posterior translation of the humeral head?

Explanation

Correct Answer: D

The inferior glenohumeral ligament (IGHL) complex is the primary static stabilizer of the shoulder in abduction. It consists of an anterior band, a posterior band, and an axillary pouch. In abduction and internal rotation, the posterior band of the IGHL becomes taut and acts as the primary restraint to posterior translation of the humeral head.

Question 18

During an open posterior approach to the shoulder for a posterior capsulorrhaphy, the surgeon dissects inferior to the teres minor muscle. Which of the following neurovascular structures is at greatest risk of iatrogenic injury in this specific location?

Explanation

Correct Answer: B

The axillary nerve and posterior circumflex humeral artery exit the axilla through the quadrangular space, which is bordered 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. Dissection inferior to the teres minor during a posterior approach places these structures at significant risk of injury.

Question 19

A 28-year-old male presents to the clinic with a history of recurrent posterior shoulder subluxations. To best evaluate for the presence of a reverse Hill-Sachs lesion on plain radiography, which of the following views is most appropriate?

Explanation

Correct Answer: C

The Stryker notch view is specifically designed to evaluate for posterolateral and anteromedial humeral head defects (Hill-Sachs and reverse Hill-Sachs lesions). The patient is supine with the hand placed on top of the head (arm forward flexed to ~100 degrees), and the x-ray beam is directed 10 degrees cephalad. The West Point axillary view is best for evaluating the anteroinferior glenoid rim (bony Bankart).

Question 20

A 21-year-old football player undergoes shoulder arthroscopy for recurrent posterior instability. The surgeon identifies a detachment of the posterior labrum and posterior capsule from the glenoid, with the periosteum stripped and displaced medially along the posterior glenoid neck. This specific pathoanatomic lesion is termed:

Explanation

Correct Answer: C

A POLPSA (Posterior Ligamentous Articular Pointing Sleeve Avulsion) lesion is the posterior equivalent of an ALPSA lesion. It involves an avulsion of the posterior labrum and capsule from the glenoid rim, with the periosteum remaining intact but stripped and displaced medially along the posterior glenoid neck. A reverse Bankart lesion involves a complete tear of the posterior labrum and capsule without the intact periosteal sleeve.

Question 21

A 22-year-old collegiate offensive lineman presents with a history of recurrent posterior shoulder instability. He has not had any frank dislocations but experiences pain and a sensation of subluxation when his arm is forward flexed, adducted, and internally rotated during blocking maneuvers. He is prescribed a comprehensive physical therapy program. Which of the following muscles should be the primary focus of strengthening to dynamically stabilize the glenohumeral joint against posterior translation?

Explanation

Correct Answer: Infraspinatus

Conservative management of recurrent unidirectional posterior shoulder instability emphasizes strengthening of the dynamic posterior stabilizers. The primary muscles targeted are the infraspinatus, teres minor, and the posterior head of the deltoid. These muscles work synergistically to provide a dynamic posterior buttress and compress the humeral head into the glenoid, counteracting posteriorly directed forces. Strengthening the subscapularis or pectoralis major would exacerbate the internal rotation forces that contribute to posterior instability.

Question 22

A 35-year-old male presents to the emergency department after experiencing a first-time generalized tonic-clonic seizure. He complains of severe right shoulder pain and an inability to move the arm. On physical examination, his right arm is locked in internal rotation and adduction. Radiographs confirm a posterior glenohumeral dislocation. Which of the following osseous lesions is most commonly associated with this specific mechanism of injury?

Explanation

Correct Answer: Anteromedial humeral head impaction fracture

Posterior shoulder dislocations are classically caused by seizures, electrical shocks, or high-energy trauma. The intense, uncoordinated muscle contractions during a seizure (where the stronger internal rotators overpower the external rotators) force the humeral head posteriorly. As the humeral head dislocates posteriorly, the anterior aspect of the humeral head impacts against the posterior glenoid rim, creating an anteromedial humeral head impaction fracture, known as a reverse Hill-Sachs lesion. A posterolateral impaction fracture (Hill-Sachs lesion) is seen in anterior dislocations.

Question 23

A 19-year-old male weightlifter complains of vague posterior shoulder pain that worsens during the descent phase of the bench press. You suspect underlying posterior shoulder instability and a possible labral tear. Which of the following physical examination maneuvers is most specific for detecting a posteroinferior labral tear?

Explanation

Correct Answer: Kim test

The Kim test is highly sensitive and specific for detecting posteroinferior labral tears, which are often associated with posterior shoulder instability. It is performed with the patient seated and the arm in 90 degrees of abduction. The examiner applies an axial load to the elbow while simultaneously elevating the arm 45 degrees diagonally upward and backward. Sudden onset of posterior shoulder pain indicates a positive test. The O'Brien test evaluates for SLAP tears, the Apprehension test is for anterior instability, and the Speed test evaluates the long head of the biceps.

Question 24

A 40-year-old male presents with a locked posterior shoulder dislocation that occurred 3 weeks ago following an electrical shock. Computed tomography (CT) imaging reveals an anteromedial humeral head defect involving 35% of the articular surface. Which of the following is the most appropriate surgical management to prevent recurrent instability?

Explanation

Correct Answer: Transfer of the subscapularis tendon into the defect

The management of a reverse Hill-Sachs lesion depends on the size of the articular defect. For defects involving 20% to 40% of the articular surface, a McLaughlin procedure (transfer of the subscapularis tendon into the defect) or a modified McLaughlin procedure (transfer of the lesser tuberosity with the attached subscapularis tendon) is indicated. This prevents the defect from engaging the posterior glenoid rim during internal rotation. Defects less than 20% can often be managed non-operatively or with simple reduction, while defects greater than 40-50% typically require arthroplasty.

Question 25

During the evaluation of a patient with multidirectional shoulder instability, an orthopedic surgeon considers the static stabilizers of the glenohumeral joint. When the shoulder is abducted to 90 degrees and internally rotated, which of the following capsuloligamentous structures serves as the primary static restraint to posterior translation?

Explanation

Correct Answer: Posterior band of the inferior glenohumeral ligament

The inferior glenohumeral ligament (IGHL) complex is the most important static stabilizer of the shoulder. It consists of an anterior band, a posterior band, and an axillary pouch. The posterior band of the IGHL is the primary static restraint to posterior translation of the humerus when the shoulder is abducted to 90 degrees and internally rotated. The superior glenohumeral ligament and coracohumeral ligament primarily resist inferior translation in the adducted shoulder.

Question 26

A 28-year-old male presents to the urgent care clinic after a fall onto an outstretched hand. He complains of severe shoulder pain and restricted range of motion. An anteroposterior (AP) radiograph of the shoulder reveals a "lightbulb sign" and loss of the normal half-moon overlap between the humeral head and the glenoid. What is the most critical next step in the radiographic evaluation of this patient?

Explanation

Correct Answer: Axillary lateral or Velpeau view radiograph

The "lightbulb sign" on an AP radiograph is highly indicative of a posterior shoulder dislocation. It occurs because the humerus is locked in internal rotation, causing the humeral head to appear symmetric and rounded like a lightbulb. However, an AP view alone is insufficient to definitively diagnose a dislocation. An axillary lateral view is the gold standard plain radiograph for confirming the anterior-posterior relationship of the glenohumeral joint. If the patient is in too much pain to abduct the arm for a standard axillary view, a Velpeau view can be obtained.

Question 27

A surgeon is performing an open posterior bone block procedure for a patient with recurrent posterior shoulder instability and significant posterior glenoid bone loss. The surgical approach involves an incision over the posterior shoulder. To safely access the posterior joint capsule, the surgeon must develop an internervous plane. Which of the following describes the correct internervous plane for the classic posterior approach to the shoulder?

Explanation

Correct Answer: Between the infraspinatus and teres minor

The classic posterior approach to the shoulder utilizes the internervous plane between the infraspinatus (innervated by the suprascapular nerve) and the teres minor (innervated by the axillary nerve). This plane allows safe access to the posterior glenoid and capsule without denervating the posterior rotator cuff musculature. Care must be taken to avoid injuring the axillary nerve and posterior circumflex humeral artery as they exit the quadrangular space inferior to the teres minor.

Question 28

A 24-year-old male undergoes an open posterior capsulorrhaphy for recurrent posterior shoulder instability. Postoperatively, he complains of numbness over the lateral aspect of his shoulder and demonstrates weakness in active shoulder abduction beyond 15 degrees. Which of the following nerves was most likely injured during the surgical procedure?

Explanation

Correct Answer: Axillary nerve

The axillary nerve is at significant risk during posterior shoulder surgery, particularly when dissecting near the inferior capsule or the inferior border of the teres minor. The axillary nerve exits the axilla through the quadrangular space and courses around the surgical neck of the humerus. Injury to this nerve results in weakness of the deltoid muscle (impairing shoulder abduction) and numbness over the lateral aspect of the shoulder (the "regimental badge" area) supplied by the superior lateral cutaneous nerve of the arm.

Question 29

A physical therapist is designing a rehabilitation protocol for a patient with posterior shoulder instability. The protocol heavily focuses on the infraspinatus muscle. In addition to providing external rotation, what is the primary biomechanical function of the infraspinatus during active shoulder elevation?

Explanation

Correct Answer: Depression and compression of the humeral head into the glenoid

The rotator cuff muscles, including the infraspinatus, function as dynamic stabilizers of the glenohumeral joint. During active shoulder elevation, the deltoid exerts a strong superior shear force on the humerus. The infraspinatus, along with the subscapularis and teres minor, acts to depress the humeral head and compress it firmly into the glenoid concavity (concavity compression). This force couple is essential for maintaining the center of rotation of the humeral head and preventing superior migration or instability.

Question 30

Posterior shoulder instability is relatively uncommon compared to anterior instability, accounting for roughly 2-10% of all shoulder instabilities. Which of the following patient populations has the highest risk for developing recurrent microtraumatic posterior shoulder instability?

Explanation

Correct Answer: Offensive linemen in American football

Recurrent microtraumatic posterior shoulder instability is classically seen in athletes who experience repetitive posteriorly directed forces on a forward flexed, adducted, and internally rotated arm. This is the exact position assumed by offensive linemen in American football during blocking. Weightlifters (particularly during the bench press) are also at high risk. Overhead throwing athletes are more prone to anterior instability or SLAP lesions, while generalized laxity typically presents as multidirectional instability.

Question 31

A 24-year-old offensive lineman presents with recurrent posterior shoulder instability. He is undergoing a nonoperative rehabilitation program. Which of the following muscles acts as the primary dynamic posterior stabilizer of the glenohumeral joint and should be the primary focus of his strengthening program?

Explanation

Correct Answer: B (Infraspinatus)

The infraspinatus and teres minor are the primary dynamic stabilizers against posterior glenohumeral translation. Conservative management of recurrent unidirectional posterior shoulder instability heavily emphasizes the strengthening of the infraspinatus, teres minor, and posterior deltoid. The subscapularis, pectoralis major, and latissimus dorsi are internal rotators and anterior stabilizers, while the supraspinatus primarily assists in abduction and superior stability.

Question 32

A 32-year-old male presents to the emergency department with severe right shoulder pain and an inability to externally rotate his arm after a generalized tonic-clonic seizure. Radiographs reveal a posterior shoulder dislocation. Which of the following best explains the mechanism of this specific injury pattern during a seizure?

Explanation

Correct Answer: A (Overpowering of the external rotators by the stronger internal rotators)

Posterior shoulder dislocations classically occur during seizures or electrical shock. This is due to the massive, simultaneous tetanic contraction of the shoulder musculature. The strong internal rotators (latissimus dorsi, pectoralis major, and subscapularis) overpower the relatively weaker external rotators (infraspinatus and teres minor), forcefully driving the humeral head posteriorly out of the glenoid fossa.

Question 33

A 21-year-old collegiate weightlifter complains of deep posterior shoulder pain with bench pressing. On examination, the patient is seated with the arm abducted to 90 degrees and internally rotated. The examiner applies an axial load to the humerus while horizontally adducting the arm, which produces a sudden clunk and pain. Which of the following is the most likely diagnosis?

Explanation

Correct Answer: C (Posterior shoulder instability)

The vignette describes the Jerk test, which is highly specific for posterior shoulder instability and posterior labral tears. A positive test occurs when a posterior subluxation (clunk) is felt as the arm is horizontally adducted under an axial load, and a second clunk may be felt as the arm is returned to the starting position (reduction). This test places maximal stress on the posterior band of the inferior glenohumeral ligament and the posterior labrum.

Question 34

A 28-year-old male presents with recurrent posterior shoulder instability. Magnetic resonance arthrography (MRA) demonstrates an incomplete and concealed avulsion of the posteroinferior labrum. The articular cartilage is intact, and there is no retroversion of the glenoid. Which of the following eponyms best describes this lesion?

Explanation

Correct Answer: D (Kim's lesion)

A Kim's lesion is defined as an incomplete and concealed avulsion of the posteroinferior labrum. It is a hallmark pathoanatomic finding in posterior shoulder instability. Unlike a reverse Bankart lesion, where the labrum is completely detached from the glenoid rim, a Kim's lesion involves a deep incomplete tear between the labrum and the glenoid cartilage, often requiring probing during arthroscopy to identify.

Question 35

A 26-year-old male requires an open posterior stabilization for refractory posterior shoulder instability. The surgeon utilizes a classic posterior approach to the shoulder. Which of the following describes the correct internervous plane utilized in this approach?

Explanation

Correct Answer: B (Between the infraspinatus and teres minor)

The classic posterior approach to the shoulder utilizes the internervous plane between the infraspinatus (innervated by the suprascapular nerve) and the teres minor (innervated by the axillary nerve). This plane allows safe access to the posterior glenohumeral joint capsule and labrum without denervating the posterior rotator cuff musculature.

Question 36

During an open posterior shoulder stabilization, the surgeon dissects inferiorly along the posterior glenoid neck. Which of the following neurovascular structures is at greatest risk of iatrogenic injury in this specific location?

Explanation

Correct Answer: B (Axillary nerve)

The axillary nerve exits the quadrangular space and courses closely to the inferior capsule and the inferior aspect of the glenoid neck. Dissection inferior to the teres minor or along the inferior glenoid neck places the axillary nerve and the posterior circumflex humeral artery at significant risk of iatrogenic injury during posterior shoulder approaches.

Question 37

A 40-year-old male presents with a locked posterior shoulder dislocation that occurred 3 weeks ago. A CT scan reveals an anteromedial humeral head impaction fracture (reverse Hill-Sachs lesion) involving 35% of the articular surface. Which of the following is the most appropriate surgical management for this bony defect?

Explanation

Correct Answer: C (McLaughlin procedure or modification)

A reverse Hill-Sachs lesion involving 20-40% of the articular surface is typically managed with a McLaughlin procedure (transfer of the subscapularis tendon into the defect) or its Neer modification (transfer of the lesser tuberosity with the attached subscapularis into the defect). This prevents the defect from engaging the posterior glenoid rim. Defects >40-50% typically require arthroplasty, while defects <20% may be managed with closed reduction and stabilization alone.

Question 38

The primary muscle targeted in the conservative management of recurrent posterior shoulder instability is innervated by a nerve that passes through which of the following anatomic structures?

Explanation

Correct Answer: E (Spinoglenoid notch)

The primary muscle targeted in the conservative management of posterior instability is the infraspinatus. The infraspinatus is innervated by the suprascapular nerve. After passing through the suprascapular notch (where it innervates the supraspinatus), the nerve travels around the base of the scapular spine through the spinoglenoid notch to innervate the infraspinatus.

Question 39

A 19-year-old collegiate swimmer is diagnosed with recurrent posterior shoulder subluxation. She is prescribed a physical therapy program. In addition to strengthening the infraspinatus and posterior deltoid, she is advised to avoid positions that place the posterior capsule under maximal stress. Which of the following positions should she avoid?

Explanation

Correct Answer: B (Flexion, adduction, and internal rotation)

The posterior capsule and labrum are placed under maximal tension when the shoulder is in flexion, adduction, and internal rotation. This is the classic provocative position for posterior instability (and the position used in the Jerk test). Patients with posterior instability should avoid this position during rehabilitation and daily activities to prevent recurrent subluxation.

Question 40

A 22-year-old male with recurrent posterior shoulder instability undergoes advanced imaging. Which of the following anatomic variants of the glenoid is most strongly associated with an increased risk of posterior shoulder instability?

Explanation

Correct Answer: B (Increased glenoid retroversion)

Increased glenoid retroversion (excessive posterior tilt of the glenoid articular surface) is a well-recognized anatomic risk factor for posterior shoulder instability. Normal glenoid version is typically neutral to slightly retroverted (around 1-2 degrees). Excessive retroversion (e.g., >7-10 degrees) significantly increases the risk of posterior subluxation or dislocation by reducing the bony restraint against posterior translation.

Question 41

A 22-year-old collegiate offensive lineman presents with recurrent posterior shoulder instability. He has not had any frank dislocations but experiences a "clunking" sensation when pass blocking. Physical examination reveals a positive Jerk test. Radiographs and MRI show no significant bone loss or labral tearing. He wishes to pursue nonoperative management. A physical therapy program should primarily focus on strengthening which of the following muscle groups to provide dynamic stability against posterior humeral head translation?

Explanation

Correct Answer: Infraspinatus and teres minor

Conservative management of recurrent unidirectional posterior shoulder instability heavily emphasizes strengthening the dynamic posterior stabilizers of the glenohumeral joint. The primary muscles responsible for resisting posterior translation of the humeral head are the infraspinatus, teres minor, and the posterior head of the deltoid. Strengthening the anterior structures (such as the subscapularis and pectoralis major) can actually exacerbate posterior instability by creating an imbalance that pulls the humeral head posteriorly.

Question 42

A 35-year-old man presents to the emergency department after experiencing a first-time grand mal seizure. He complains of severe left shoulder pain and an inability to move the arm. Radiographs reveal a posterior shoulder dislocation. In what position is the glenohumeral joint most vulnerable to posterior dislocation during a traumatic event or seizure?

Explanation

Correct Answer: Flexion, adduction, and internal rotation

The classic position of vulnerability for a posterior shoulder dislocation is flexion, adduction, and internal rotation. During a seizure or electrocution, the strong internal rotators of the shoulder (latissimus dorsi, pectoralis major, and subscapularis) overpower the weaker external rotators (infraspinatus and teres minor). This intense, unbalanced muscle contraction forces the humeral head posteriorly out of the glenoid fossa. Traumatic posterior dislocations also typically occur when an axial load is applied to the arm while it is in this vulnerable position.

Question 43

A 28-year-old weightlifter presents with vague posterior shoulder pain and weakness in external rotation. He has a history of recurrent posterior shoulder subluxations. Physical examination demonstrates atrophy of the infraspinatus fossa but normal bulk of the supraspinatus. MRI reveals a posterior labral tear with an associated paralabral cyst. At which of the following anatomic locations is the cyst most likely compressing the affected nerve?

Explanation

Correct Answer: Spinoglenoid notch

Posterior labral tears can allow synovial fluid to leak and form paralabral cysts. These cysts frequently extend into the spinoglenoid notch. The suprascapular nerve passes through the suprascapular notch (innervating the supraspinatus) and then travels through the spinoglenoid notch to innervate the infraspinatus. Compression at the spinoglenoid notch results in isolated infraspinatus weakness and atrophy, while sparing the supraspinatus. Compression at the suprascapular notch would affect both muscles. The quadrilateral space contains the axillary nerve, which innervates the deltoid and teres minor.

Question 44

A 40-year-old man presents with a locked posterior shoulder dislocation following an electrocution injury 3 weeks ago. A CT scan demonstrates an anteromedial humeral head impaction fracture (reverse Hill-Sachs lesion) involving 25% of the articular surface. The glenoid is intact. Which of the following is the most appropriate surgical management?

Explanation

Correct Answer: Open reduction and transfer of the lesser tuberosity into the defect

A reverse Hill-Sachs lesion is an anteromedial impaction fracture of the humeral head caused by the posterior glenoid rim during a posterior dislocation. The treatment depends on the size of the defect. Defects less than 20% can often be managed nonoperatively or with simple reduction if stable. Defects between 20% and 40% are at high risk for engaging the posterior glenoid and causing recurrent instability. These are best treated with a McLaughlin procedure (transfer of the subscapularis tendon into the defect) or a modified McLaughlin procedure (transfer of the lesser tuberosity with the attached subscapularis into the defect). Defects greater than 40-50% typically require hemiarthroplasty or total shoulder arthroplasty.

Question 45

A 19-year-old male presents with posterior shoulder pain. The examiner suspects a posteroinferior labral tear. The examiner elevates the patient's arm to 90 degrees of abduction in the scapular plane, applies an axial load to the elbow, and simultaneously applies a downward and posterior force to the proximal humerus while elevating the arm diagonally upward. The patient experiences sudden onset of posterior shoulder pain. Which of the following tests was performed?

Explanation

Correct Answer: Kim test

The Kim test is specifically designed to detect posteroinferior labral lesions. It is performed with the patient seated and the arm in 90 degrees of abduction. The examiner applies an axial load and a downward/posterior force while elevating the arm diagonally upward. A positive test is the elicitation of posterior shoulder pain. The Jerk test is performed with the arm in 90 degrees of abduction and internal rotation; the arm is horizontally adducted while an axial load is applied, producing a "clunk" or pain as the humeral head subluxates posteriorly.

Question 46

A surgeon is performing an open posterior approach to the shoulder for a posterior bone block procedure to address recurrent posterior instability. After incising the deltoid in line with its fibers, an internervous plane is utilized to access the posterior joint capsule. This plane is located between which of the following two muscles?

Explanation

Correct Answer: Infraspinatus and teres minor

The classic open posterior approach to the shoulder utilizes the internervous plane between the infraspinatus (innervated by the suprascapular nerve) and the teres minor (innervated by the axillary nerve). This plane allows safe access to the posterior capsule and glenoid. Care must be taken not to extend the dissection too far inferiorly to avoid injury to the axillary nerve as it exits the quadrilateral space just inferior to the teres minor.

Question 47

A 45-year-old man presents to the emergency department with shoulder pain after a fall from a ladder. Anteroposterior (AP) radiographs of the shoulder reveal a "lightbulb" sign and a "trough line" sign. Which of the following is the most likely diagnosis?

Explanation

Correct Answer: Posterior shoulder dislocation

Posterior shoulder dislocations are notoriously missed on standard AP radiographs because the humeral head may appear to be in the glenoid. The "lightbulb" sign occurs because the humerus is locked in internal rotation, causing the humeral head to appear symmetric and rounded, resembling a lightbulb. The "trough line" sign represents the impaction fracture on the anteromedial humeral head (reverse Hill-Sachs lesion) created by the posterior glenoid rim. An axillary or scapular Y view is essential to confirm the posterior direction of the dislocation.

Question 48

During a biomechanical study of the glenohumeral joint, researchers selectively section various capsuloligamentous structures to determine their contribution to posterior stability. Which of the following structures is the primary static restraint to posterior translation of the humerus when the arm is flexed, adducted, and internally rotated?

Explanation

Correct Answer: Posterior band of the inferior glenohumeral ligament

The inferior glenohumeral ligament (IGHL) complex is the most important static stabilizer of the shoulder. It acts like a hammock. The posterior band of the IGHL is the primary static restraint to posterior translation of the humeral head when the arm is in the vulnerable position of flexion, adduction, and internal rotation. The superior glenohumeral ligament and coracohumeral ligament primarily resist inferior translation in the adducted arm.

Question 49

A 26-year-old male undergoes an open posterior bone block procedure (using an iliac crest autograft) for recurrent posterior shoulder instability with significant posterior glenoid bone loss. Postoperatively, the patient is noted to have weakness in shoulder abduction and decreased sensation over the lateral aspect of the shoulder. Which of the following nerves was most likely injured during the procedure?

Explanation

Correct Answer: Axillary nerve

The axillary nerve is at significant risk during the posterior approach to the shoulder, particularly when dissecting inferior to the teres minor or when placing retractors at the inferior aspect of the glenoid neck. The nerve exits the quadrilateral space just inferior to the teres minor and wraps around the surgical neck of the humerus. Injury results in denervation of the deltoid (causing weakness in abduction) and teres minor, as well as numbness over the lateral shoulder (in the distribution of the superior lateral cutaneous nerve of the arm).

Question 50

A 20-year-old female gymnast presents with bilateral shoulder pain and a feeling of her shoulders "slipping out of place." She can voluntarily subluxate her shoulders posteriorly. Physical exam reveals a positive sulcus sign of 3 cm bilaterally that does not reduce with external rotation. She has generalized ligamentous laxity with a Beighton score of 7/9. What is the most appropriate initial management for this patient's posterior instability?

Explanation

Correct Answer: Aggressive physical therapy focusing on periscapular and rotator cuff strengthening

This patient presents with multidirectional instability (MDI), characterized by generalized laxity, voluntary subluxation, and a positive sulcus sign that persists in external rotation (indicating rotator interval incompetence). The hallmark of MDI treatment is a prolonged, dedicated course of physical therapy (typically at least 6 months) focusing on strengthening the dynamic stabilizers, specifically the rotator cuff and periscapular muscles. Operative intervention (such as an inferior capsular shift) is strictly reserved for patients who fail extensive conservative management, and voluntary dislocators often have poor surgical outcomes.

Question 51

A 35-year-old electrician presents to the emergency department after sustaining a high-voltage electrical shock. His right arm is locked in internal rotation and he resists any external rotation. A CT scan confirms a posterior shoulder dislocation. The classic bony defect associated with this injury is located on which aspect of the humerus?

Explanation

A reverse Hill-Sachs lesion is an impaction fracture located on the anteromedial aspect of the humeral head. It occurs when the anteromedial humeral head impacts the posterior glenoid rim during a posterior dislocation.

Question 52

During a physical examination for suspected posterior shoulder instability, the examiner performs the Jerk test. The patient is seated, and the arm is placed in 90 degrees of forward flexion and internal rotation. While applying an axial load to the humerus, the examiner moves the arm in which of the following directions to elicit a clunk?

Explanation

The Jerk test is performed by placing the arm in 90 degrees of forward flexion and internal rotation, applying an axial load, and moving the arm into horizontal adduction. A sudden clunk indicates posterior subluxation of the humeral head off the glenoid.

Question 53

A 42-year-old male presents with a locked posterior shoulder dislocation following a seizure 3 weeks ago. Imaging reveals a reverse Hill-Sachs defect that involves 30% of the articular surface. He is highly active and wishes to retain his native joint. Which of the following is the most appropriate surgical intervention?

Explanation

For reverse Hill-Sachs lesions involving 20-40% of the articular surface, a modified McLaughlin procedure (transfer of the lesser tuberosity with the attached subscapularis) is indicated. This provides a bone-to-bone healing surface and mechanically prevents the defect from engaging the posterior glenoid.

Question 54

A 24-year-old professional baseball pitcher presents with vague posterior shoulder pain that affects his performance. He denies any frank instability. During which phase of the throwing motion is posterior shoulder instability and capsular stress most commonly symptomatic?

Explanation

Posterior shoulder instability in throwing athletes typically manifests during the deceleration and follow-through phases. During this phase, extreme compressive and distractive forces are placed on the posterior capsule and labrum to slow the arm down.

Question 55

An AP radiograph of a 30-year-old trauma patient reveals a 'rim sign' suspicious for a posterior shoulder dislocation. The rim sign is considered positive when the distance between the medial aspect of the humeral head and the anterior glenoid rim exceeds what measurement?

Explanation

The rim sign on an AP radiograph is highly suggestive of a posterior shoulder dislocation. It is defined as a gap of greater than 6 mm between the medial border of the humeral head and the anterior glenoid margin.

Question 56

A 28-year-old male is undergoing an open posterior capsular shift for recurrent posterior shoulder instability. During dissection and capsular release at the inferior-most aspect of the glenoid (6 o'clock position), which of the following nerves is at greatest risk of iatrogenic injury?

Explanation

The axillary nerve, specifically its posterior branch, lies in close proximity (often within 10-15 mm) to the inferior and posteroinferior glenoid rim. Care must be taken during capsular dissection and suture passing at the 6 o'clock position to avoid tethering or injuring this nerve.

Question 57

During diagnostic arthroscopy for chronic posterior shoulder pain in a contact athlete, the surgeon identifies a 'Kim lesion'. Which of the following best describes this pathoanatomic finding?

Explanation

A Kim lesion is an incomplete, concealed avulsion of the posteroinferior labrum where the superficial articular cartilage and periosteum remain intact. It results in loss of normal posteroinferior labral height and retroactive capsular laxity.

Question 58

A 16-year-old female presents with the ability to painlessly dislocate her shoulder posteriorly on command. She demonstrates this by elevating her arm and contracting her muscles, then easily reduces it. Imaging shows no structural defects. What is the most appropriate initial management?

Explanation

Volitional, painless posterior instability is a hallmark of atraumatic, multidirectional instability (AMBRI spectrum). The mainstay of treatment is extensive physical therapy focusing on periscapular strengthening and biofeedback to retrain muscle firing patterns.

Question 59

A 27-year-old rugby player presents with recurrent posterior shoulder instability. Advanced imaging reveals a posterior glenoid bone loss of 25%. Soft tissue structures are relatively preserved. What is the most appropriate surgical management to prevent recurrent instability?

Explanation

In the setting of posterior glenoid bone loss exceeding 15-20%, soft tissue repairs alone have an unacceptably high failure rate. A posterior bone block augmentation (using iliac crest or distal tibia allograft) is indicated to restore the articular arc.

Question 60

Biomechanical studies have demonstrated that the primary static restraint to posterior glenohumeral translation with the arm resting in 0 degrees of abduction and neutral rotation is which of the following structures?

Explanation

At 0 degrees of abduction, the primary restraints to posterior and inferior translation are the superior glenohumeral ligament (SGHL) and the coracohumeral ligament (CHL), often referred to as the rotator interval structures.

Question 61

An anteroposterior (AP) radiograph of a shoulder reveals a 'lightbulb sign'. This classic radiographic appearance is directly caused by which of the following anatomic positions of the humerus?

Explanation

The 'lightbulb sign' occurs in posterior shoulder dislocations because the arm is locked in pronounced internal rotation. This rotation causes the tuberosities to overlap the humeral head head-on, giving the head a symmetrical, rounded appearance resembling a lightbulb.

Question 62

A 68-year-old male with chronic epilepsy presents with a missed posterior shoulder dislocation of 8 months duration. CT scan shows a reverse Hill-Sachs lesion involving 55% of the articular surface with severe secondary glenohumeral osteoarthritis. Which of the following is the most appropriate definitive treatment?

Explanation

For chronic posterior dislocations with articular defects >45-50% and concurrent glenohumeral osteoarthritis, joint replacement (total shoulder arthroplasty or hemiarthroplasty depending on glenoid wear) is the treatment of choice. Joint-preserving procedures are contraindicated with such massive defects.

Question 63

On a standard AP radiograph of a patient with a suspected posterior dislocation, a dense vertical line is noted on the medial aspect of the humeral head. This 'trough line' represents which of the following pathologic findings?

Explanation

The 'trough line' is a dense vertical line seen on an AP radiograph corresponding to the reverse Hill-Sachs lesion. It represents the cortical impaction fracture on the anteromedial aspect of the humeral head as it wedges against the posterior glenoid.

Question 64

A patient undergoes an open posterior capsulorrhaphy for recalcitrant posterior instability. Postoperatively, if the posterior capsule is over-tightened during the repair, the patient is at greatest risk for clinically significant loss of which shoulder motion?

Explanation

Over-tightening of the posterior capsule during surgical stabilization restricts the normal excursion required for internal rotation. Patients will characteristically present with a prominent loss of internal rotation postoperatively.

Question 65

The classic (original) McLaughlin procedure, utilized for the treatment of moderate-sized anteromedial humeral head defects, involves the transfer of which of the following structures into the bony defect?

Explanation

The classic McLaughlin procedure involves detaching the subscapularis tendon and transferring it into the anteromedial humeral head defect. The modified McLaughlin improves upon this by transferring the lesser tuberosity with the attached tendon to achieve bone-to-bone healing.

Question 66

During standard shoulder arthroscopy for a posterior labral tear, the surgeon is establishing the standard posterior viewing portal. What are the correct anatomic landmarks for placing this portal?

Explanation

The standard posterior portal is established in the 'soft spot' located approximately 2 cm inferior and 1 cm medial to the posterolateral corner of the acromion. This provides an optimal trajectory into the glenohumeral joint.

Question 67

A 22-year-old weightlifter presents with posterior shoulder instability. MRI reveals a POLPSA lesion. Which of the following accurately describes the pathology of a POLPSA lesion?

Explanation

POLPSA stands for Posterior Labrocapsular Periosteal Sleeve Avulsion. It is characterized by the posterior labrum being avulsed from the glenoid rim along with an intact sleeve of periosteum, leading to a redundant posterior recess.

Question 68

A 21-year-old collegiate swimmer with recurrent posterior subluxations has failed 6 months of targeted physical therapy. Diagnostic arthroscopy reveals a severely patulous posterior capsule but a completely intact and well-fixed posterior labrum. What is the most appropriate arthroscopic surgical step?

Explanation

In patients with a patulous posterior capsule and an intact labrum, arthroscopic posterior capsular plication (often utilizing suture anchors or capsule-to-capsule sutures) is the procedure of choice to reduce capsular volume and restore stability.

Question 69

Bilateral posterior shoulder dislocations are a rare clinical entity but are highly specific to a particular mechanism of injury. Which of the following etiologies is most classically associated with simultaneous bilateral posterior dislocations?

Explanation

Bilateral posterior shoulder dislocations are classically caused by violent muscle contractions, such as those occurring during generalized seizures or electrocution. The strong internal rotators (latissimus dorsi, pectoralis major, subscapularis) overpower the weaker external rotators.

Question 70

A biomechanical evaluation of a cadaveric shoulder is being performed. The shoulder is placed in 90 degrees of forward flexion and maximal internal rotation. Which structure acts as the primary static restraint to posterior translation in this specific position?

Explanation

The posterior band of the inferior glenohumeral ligament (IGHL) complex is the primary static restraint to posterior translation when the shoulder is placed in 90 degrees of flexion and internal rotation.

Question 71

A 24-year-old weightlifter presents with vague posterior shoulder pain. On examination, with the arm in 90 degrees of forward flexion and internal rotation, an axial load is applied while horizontally adducting the arm. A sudden clunk is felt, followed by a second clunk when the arm is returned to the starting position. Injury to which anatomical structure is most strongly associated with this positive provocative test?

Explanation

The clinical scenario describes a positive Jerk test, which is highly specific for posteroinferior instability. The posterior band of the inferior glenohumeral ligament (IGHL) is the primary static restraint to posterior translation in this position.

Question 72

A 40-year-old electrician is evaluated in the emergency department following an electrocution injury. An AP shoulder radiograph reveals a 'trough line' sign. This radiographic finding corresponds to which of the following pathoanatomic lesions?

Explanation

The 'trough line' is an impaction fracture of the anteromedial aspect of the humeral head (reverse Hill-Sachs lesion). It is created when the anterior humeral head impacts the posterior glenoid rim during a posterior dislocation.

Question 73

A 32-year-old male sustains a locked posterior shoulder dislocation during a seizure. CT imaging reveals an anteromedial humeral head impaction fracture involving 35% of the articular surface. The glenoid is completely intact. Which of the following is the most appropriate surgical management?

Explanation

For reverse Hill-Sachs lesions involving 20% to 40% of the articular surface, the modified McLaughlin procedure (transfer of the lesser tuberosity and subscapularis into the defect) is indicated to prevent engagement. Defects greater than 40-50% generally require arthroplasty.

Question 74

A 21-year-old collegiate rower undergoes shoulder arthroscopy for chronic, painful posterior shoulder instability. The surgeon visualizes an incomplete, concealed avulsion of the posteroinferior labrum. The articular margin remains intact, but there is loss of normal labral height. What is the correct eponym for this specific lesion?

Explanation

A Kim lesion is an incomplete, concealed avulsion of the posteroinferior labrum characterized by a superficial, intact articular margin but a deep tear causing retroversion of the labrum. It is common in athletes with repetitive posterior microtrauma.

Question 75

A 26-year-old male volleyball player presents with insidious onset posterior shoulder pain and weakness in external rotation. MRI reveals a posterosuperior labral tear with a multiloculated cyst occupying the spinoglenoid notch. Which of the following physical examination findings is most likely present?

Explanation

A paralabral cyst in the spinoglenoid notch typically compresses the suprascapular nerve after it has innervated the supraspinatus. This leads to isolated denervation and atrophy of the infraspinatus muscle.

Question 76

A 65-year-old male presents with a missed chronic posterior shoulder dislocation 6 months after a fall. CT imaging demonstrates a reverse Hill-Sachs lesion involving 55% of the humeral head articular surface and severe glenohumeral osteoarthritis. What is the most appropriate definitive treatment?

Explanation

Total shoulder arthroplasty is indicated for chronic locked posterior dislocations with humeral head defects greater than 50% and concurrent advanced glenohumeral osteoarthritis.

Question 77

A 15-year-old female presents with the ability to spontaneously dislocate her shoulder posteriorly without pain. She demonstrates this by bringing her arm into elevation and internal rotation, then easily reduces it. She has no history of trauma. What is the most appropriate initial management?

Explanation

Volitional, non-traumatic posterior shoulder instability is best managed non-operatively. Physical therapy incorporating biofeedback to retrain asynchronous periscapular and rotator cuff muscle firing is the standard of care.

Question 78

A 30-year-old male is evaluated in the trauma bay following an explosion. He securely holds his right arm internally rotated against his abdomen. The AP shoulder radiograph demonstrates a 'lightbulb' sign. What causes this specific radiographic appearance?

Explanation

The 'lightbulb' sign is seen on AP radiographs in posterior dislocations due to the fixed internal rotation of the humeral head. This rotation hides the greater tuberosity profile, creating a symmetric, rounded appearance.

Question 79

A 25-year-old rugby player has recurrent posterior shoulder instability despite a previous arthroscopic posterior labral repair. Preoperative CT imaging reveals excessive glenoid retroversion of 22 degrees and 25% posterior glenoid bone loss. What is the most appropriate surgical intervention?

Explanation

Open posterior bone block augmentation (e.g., using distal tibia or iliac crest) is indicated for recurrent posterior instability with significant posterior glenoid bone loss (>20%) or severe glenoid retroversion (>15 degrees).

Question 80

During a physical examination for posterior instability, the examiner performs the Kim test to identify a concealed posteroinferior labral tear. Which combination of joint positions and forces best isolates the posteroinferior labrum during this specific test?

Explanation

The Kim test isolates the posteroinferior labrum by elevating the arm to 120 degrees, applying an axial load, and directing a posteroinferior force while horizontally adducting the arm.

Question 81

A 29-year-old tennis player complains of posterior shoulder pain during the follow-through phase of his serve. Exam reveals posterior joint line tenderness and a positive posterior apprehension sign. What is the primary pathoanatomic mechanism causing posterior labral shear during this specific athletic motion?

Explanation

During the follow-through phase of overhead sports (like a tennis serve or pitching), the posterior rotator cuff and capsulolabral structures undergo massive eccentric loads to decelerate the arm, leading to posterior labral shear and microtrauma.

Question 82

A 28-year-old male undergoes an open posterior capsulorrhaphy for refractory posterior shoulder instability. Postoperatively, he develops a severe limitation in forward elevation, cross-body adduction, and internal rotation. What is the most likely iatrogenic cause of this complication?

Explanation

Overtightening the posterior capsule during open or arthroscopic stabilization can lead to obligate anterior translation of the humeral head and significantly restrict internal rotation, cross-body adduction, and forward elevation.

Question 83

When performing an arthroscopic posterior Bankart repair, the surgeon needs an optimal trajectory to place suture anchors at the 7 o'clock position in a right shoulder. Which accessory portal is most commonly utilized to achieve the best approach angle for this region?

Explanation

The posterolateral portal (often called the Port of Wilmington) provides the ideal deadman's angle for anchor insertion into the posteroinferior glenoid (7 o'clock in a right shoulder, 5 o'clock in a left shoulder).

Question 84

A 27-year-old military paratrooper suffers from recurrent posterior shoulder subluxations. Imaging demonstrates a posterior labral tear, 5% posterior glenoid bone loss, and 5 degrees of glenoid retroversion. After failing 6 months of non-operative management, what is the surgical treatment of choice?

Explanation

In the absence of significant glenoid retroversion (<10-15 degrees) or substantial bone loss (<10-20%), soft-tissue stabilization via an arthroscopic posterior capsulolabral repair is the gold standard surgical treatment.

Question 85

Which imaging modality and specific measurement technique represent the gold standard for quantifying glenoid retroversion in a patient evaluated for recurrent posterior shoulder instability?

Explanation

Glenoid version is most accurately measured on 2D axial CT images using the Friedman line, which connects the medial border of the scapula to the center of the glenoid vault.

Question 86

A 23-year-old male trips and falls forward onto an outstretched hand, sustaining an acute posterior shoulder dislocation. Which specific biomechanical position of the arm at the moment of impact most strongly predisposes the shoulder to this type of dislocation?

Explanation

The classic mechanism for a traumatic posterior shoulder dislocation is an axial load applied to an arm that is positioned in forward flexion, adduction, and internal rotation.

Question 87

A 45-year-old male presents with severe shoulder pain after a motor vehicle accident. The AP shoulder radiograph shows a distance of 8 mm between the anterior glenoid rim and the medial aspect of the humeral head. What is this radiographic sign called, and what diagnosis does it strongly suggest?

Explanation

The 'Rim sign' is a widening of the glenohumeral joint space greater than 6 mm on an AP radiograph. It strongly suggests a posterior shoulder dislocation, as the humeral head is displaced laterally away from the anterior glenoid rim.

Question 88

The Neer modification of the classic McLaughlin procedure is commonly used for chronic posterior shoulder dislocations with large anteromedial humeral head defects. This modification specifically involves the transfer of which anatomical structure into the defect?

Explanation

The classic McLaughlin procedure transfers the subscapularis tendon directly into the reverse Hill-Sachs defect. The Neer modification improves upon this by transferring the lesser tuberosity bone block along with the attached subscapularis tendon, providing bone-to-bone healing.

Question 89

A 40-year-old male presents with a locked posterior shoulder dislocation following a seizure. Computed tomography reveals an anteromedial humeral head defect (reverse Hill-Sachs lesion) involving 30% of the articular surface. The glenoid is intact. Which of the following is the most appropriate surgical management?

Explanation

Defects involving 20% to 40% of the articular surface are typically managed with a modified McLaughlin procedure (lesser tuberosity transfer) or structural allograft to prevent engagement. Defects greater than 40% generally require arthroplasty, while those less than 20% may be managed non-operatively if stable after reduction.

Question 90

During the physical examination of a patient with suspected posterior shoulder instability, the examiner seats the patient, abducts the arm to 90 degrees, and applies an axial load to the elbow while elevating the arm diagonally upward and forward. The patient experiences sudden posterior shoulder pain without a mechanical clunk. Which provocative test was performed?

Explanation

The Kim test involves elevating the arm diagonally upward with an axial load and specifically detects posteroinferior labral lesions (Kim's lesion), indicated by pain. The Jerk test involves horizontally adducting the arm and typically yields a mechanical 'clunk' as the humeral head subluxates over the posterior glenoid rim.

Question 91

A biomechanical study is evaluating the capsuloligamentous restraints of the shoulder joint. At 90 degrees of forward flexion and internal rotation, which of the following structures serves as the primary static restraint to posterior humeral head translation?

Explanation

The posterior band of the inferior glenohumeral ligament (IGHL) is the primary static stabilizer against posterior translation when the arm is in a position of forward flexion, adduction, and internal rotation.

Question 92

A 25-year-old weightlifter presents with recurrent posterior shoulder subluxations that have failed extensive physical therapy. Preoperative computed tomography demonstrates excessive glenoid retroversion. Above what threshold of glenoid retroversion is a posterior opening wedge osteotomy or bone block generally indicated over isolated soft tissue stabilization?

Explanation

Normal glenoid version is typically 2 to 7 degrees of retroversion. In patients with recurrent posterior instability, glenoid retroversion exceeding 15 to 20 degrees is an indication for bony correction (osteotomy or bone block), as isolated soft tissue repair has a high failure rate.

Question 93

During diagnostic arthroscopy for chronic posterior shoulder pain and subtle instability, the surgeon notes an incomplete, concealed avulsion of the posteroinferior labrum. The articular margin of the labrum remains intact, but there is a distinct loss of normal labral height and retroversion. What is the correct diagnosis for this pathoanatomy?

Explanation

A Kim's lesion is a concealed, incomplete tear of the posteroinferior labrum characterized by intact articular margins but loss of labral height. In contrast, a reverse Bankart lesion is a complete detachment of the posterior labrum and capsule from the glenoid margin.

Question 94

A 30-year-old male undergoes an open posterior capsulorrhaphy for recurrent posterior shoulder instability. Postoperatively, he complains of significant restriction in his range of motion, significantly affecting his activities of daily living. Overtightening of the posterior capsule is most likely to restrict which of the following motions?

Explanation

The posterior capsule restricts internal rotation and cross-body adduction. Overtightening during posterior stabilization primarily limits internal rotation, particularly when the arm is positioned in 90 degrees of abduction or forward flexion.

Question 95

A 55-year-old male presents with chronic right shoulder pain 4 months after a prolonged seizure. Clinical examination reveals a rigid block to external rotation. Radiographs confirm a locked posterior dislocation. Which of the following findings is the strongest indication for proceeding with shoulder arthroplasty rather than a joint-preserving reconstruction?

Explanation

Arthroplasty is indicated in chronic posterior dislocations when the reverse Hill-Sachs defect involves greater than 40% of the humeral head articular surface, or when there is advanced secondary glenohumeral osteoarthritis. Smaller defects (20-40%) without arthritis are amenable to joint-preserving procedures like a lesser tuberosity transfer.

Question 96

A surgeon is performing an arthroscopic posterior stabilization for a reverse Bankart lesion. To achieve the most optimal trajectory for suture anchor insertion into the posteroinferior glenoid rim (7 o'clock to 9 o'clock positions), which of the following arthroscopic portals should be utilized?

Explanation

The accessory posteroinferior portal (often called the 7 o'clock portal) is placed approximately 2 cm inferior to the standard posterior portal. It provides the ideal angle of approach for anchor placement in the posteroinferior quadrant, avoiding medial skiving of the anchor.

Question 97

A 6-year-old child with a history of an obstetric brachial plexus palsy (Erb's palsy) presents with an internal rotation contracture of the shoulder. Imaging reveals progressive posterior subluxation of the humeral head and early glenoid dysplasia. What is the most critical initial surgical intervention to halt the progression of this joint deformity?

Explanation

In obstetric brachial plexus palsy, muscle imbalance characterized by strong internal rotators and weak external rotators leads to an internal rotation contracture and secondary posterior glenohumeral dysplasia. Early release or lengthening of the subscapularis (with or without pectoralis major release) is critical to restore balance and allow glenoid remodeling.

Question 98

A 42-year-old male undergoes surgery for a locked posterior shoulder dislocation with a 30% anteromedial humeral head defect. The surgeon performs an open reduction and transfers both the subscapularis tendon and the lesser tuberosity into the articular defect. Which eponymous procedure does this describe?

Explanation

The modified McLaughlin procedure (described by Neer) involves the transfer of the lesser tuberosity along with the attached subscapularis tendon into the reverse Hill-Sachs defect. This provides reliable bone-to-bone healing, improving upon the original McLaughlin procedure which transferred only the subscapularis tendon.

Comprehensive Guide to Posterior Glenohumeral Instability: Diagnosis, Causes & Anatomy

Posterior Shoulder Instability MCQs - Orthopedic Board Review

Posterior Shoulder Instability MCQs - Orthopedic Board Review

Chapter Index