ABOS Part I Review: Terrible Triad & Monteggia MCQs

Question 1

A 55-year-old patient presents with an elbow injury following a fall onto an outstretched hand. Radiographs reveal an elbow dislocation, a comminuted radial head fracture, and a coronoid fracture. Based on the provided case, which of the following soft tissue structures is most consistently injured in this "terrible triad" pattern?

Explanation

Correct Answer: C

The case explicitly states that with a terrible triad injury, soft tissue stabilizers of the elbow, such as the lateral collateral ligament, the anterior capsule of the elbow joint in association with the coronoid fracture, and possibly the medial collateral ligament, are expected to be injured. The LCL is a critical stabilizer against posterolateral rotatory instability, which is the common mechanism for terrible triad injuries. While the MCL can be involved, it is not as consistently injured as the LCL and anterior capsule in the initial injury pattern. The triceps tendon, biceps tendon, and posterior capsule are not typically considered primary structures injured in the terrible triad pattern.

Question 2

A 48-year-old male is diagnosed with a terrible triad injury of the elbow. After initial radiographs confirm the diagnosis, what is the most crucial next step in imaging for detailed surgical planning, as highlighted in the case?

Explanation

Correct Answer: C

The case states: "A preoperative CT scan would provide useful information regarding the degree of comminution, fracture fragment origin, degree of displacement, and other factors to be considered during the operation." While MRI can show soft tissue injuries, and stress radiographs can assess instability, the CT scan is specifically highlighted as crucial for detailed bony assessment and surgical planning in this complex fracture-dislocation pattern.

Question 3

During the operative treatment of a terrible triad injury, the primary objective is to restore stability to the elbow joint. According to the case description, which specific joint stability is the most critical to restore?

Explanation

Correct Answer: C

The case explicitly states: "Since this is an inherently unstable injury, I would advise operative treatment to restore ulnohumeral joint stability by reducing the dislocation and repairing the coronoid fracture." While the radial head replacement contributes to overall elbow stability, the primary goal is to restore the stability of the main articulation of the elbow, the ulnohumeral joint, which is disrupted by the dislocation and coronoid fracture.

Question 4

A surgeon is performing an operative repair for a terrible triad injury. After excising radial head fragments, a small, comminuted coronoid fracture is encountered, deemed too small for direct screw fixation. Based on the case, what is the most appropriate management strategy for this specific coronoid injury?

Explanation

Correct Answer: C

The case provides clear guidance: "If the coronoid fragment is too small to fix, I would perform a suture repair of the anterior capsule to the proximal ulna." It further elaborates in the operative sequence: "Depending on coronoid fragment size, I would reduce and fix the coronoid fracture with a single screw or I would suture the anterior capsule down to the coronoid footprint using suture anchors." This technique effectively reconstructs the anterior buttress of the coronoid when direct fixation is not feasible.

Question 5

During radial head replacement in the context of a terrible triad injury, the surgeon must be meticulous to avoid a common complication that can lead to persistent instability or stiffness. What specific intraoperative pitfall is emphasized in the case description regarding radial head replacement?

Explanation

Correct Answer: C

The case specifically warns against this pitfall: "The next step would be to prepare and place a radial head replacement, taking care not to 'overstuff' the joint." Overstuffing the joint can lead to increased joint reactive forces, stiffness, pain, and even persistent instability by preventing full reduction or proper tracking of the ulnohumeral joint. While other options are important considerations, 'overstuffing' is explicitly mentioned as a critical point to avoid.

Question 6

Following the initial fixation of the coronoid, radial head replacement, and LCL repair in a terrible triad injury, the elbow still demonstrates residual instability. According to the case, what are the two primary options to address this persistent instability?

Explanation

Correct Answer: C

The case clearly outlines the management for residual instability: "If residual instability persists following fixation, I would consider a separate repair of the medial collateral ligament, or alternatively, I would consider augmenting the fixation by applying an external fixator across the elbow." These two options are crucial for achieving stability when the initial repairs are insufficient.

Question 7

For the operative treatment of a terrible triad injury, the case describes a specific surgical approach. Which of the following approaches is recommended to gain access to the elbow joint and its surrounding structures?

Explanation

Correct Answer: C

The case explicitly states: "I would use the utility posterior approach to the elbow, raising thick flaps." This approach provides excellent visualization of the radial head, coronoid, and both medial and lateral collateral ligament complexes, which is essential for addressing all components of a terrible triad injury.

Question 8

During the utility posterior approach for a terrible triad repair, the ulnar nerve is a critical structure to manage. What is the specific management strategy for the ulnar nerve described in the operative sequence?

Explanation

Correct Answer: C

The case details the ulnar nerve management: "The ulnar nerve would be identified, decompressed, and protected in situ." This approach aims to prevent iatrogenic injury to the nerve during the procedure while avoiding unnecessary transposition unless indicated by preoperative symptoms or significant intraoperative tension.

Question 9

In the described operative sequence for a terrible triad injury, which of the following steps is performed first to facilitate access to deeper structures like the coronoid and anterior capsule?

Explanation

Correct Answer: C

The case clearly outlines the initial steps: "I would excise the radial head fragments first, which would give me access to the coronoid and anterior capsule." Removing the radial head fragments provides an unobstructed view and working space for addressing the coronoid fracture and anterior capsule repair, which are crucial for ulnohumeral stability.

Question 10

Prior to initiating the surgical incision for a terrible triad repair, proper patient positioning is crucial. According to the case, what is the recommended patient position for this procedure?

Explanation

Correct Answer: C

The case specifies the patient positioning: "I would position the patient in the lateral position with the affected arm over a bolster." This position allows for gravity-assisted exposure and manipulation of the elbow, providing good access to both medial and lateral aspects of the joint, which is necessary for a comprehensive terrible triad repair.

Question 11

A 45-year-old male presents after a fall onto an outstretched hand, sustaining a fracture of the proximal ulna and an anterior dislocation of the radial head. Which Bado and Peril classification type does this injury most accurately describe?

Explanation

Correct Answer: A

The Bado and Peril classification defines Monteggia fractures based on the direction of radial head dislocation and the location/angulation of the ulnar fracture. Type I involves an anterior dislocation of the radial head with an associated anteriorly angulated ulnar shaft fracture. This is the most common variant, accounting for approximately 60% of all Monteggia injuries. Type II involves posterior dislocation of the radial head, Type III involves lateral/anterolateral dislocation with a metaphyseal ulnar fracture, and Type IV involves both radial and ulnar shaft fractures with anterior radial head dislocation. Galeazzi fractures involve a distal radial shaft fracture with associated distal radioulnar joint disruption.

Question 12

Which radiographic sign is most indicative of a radial head dislocation in the context of an ulnar fracture?

Explanation

Correct Answer: B

The definitive radiographic sign of radial head dislocation is the disruption of the radial head-capitellum alignment on all views (AP, lateral, and obliques if needed). A line drawn through the center of the radial shaft should always pass through the center of the capitellum, regardless of elbow flexion or forearm rotation. If this capitellar-radial head line does not intersect the capitellum, radial head dislocation is present. While fat pads indicate an effusion (suggesting injury), and an abnormal anterior humeral line suggests supracondylar or condylar fractures, only direct visualization of the radiocapitellar relationship confirms dislocation of the radial head. Widening of the joint space can be a sign but is less definitive than complete disruption of alignment.

Question 13

A 30-year-old male sustains a Monteggia Type I fracture. What is the generally accepted definitive treatment for an adult with this injury?

Explanation

Correct Answer: B

For adult Monteggia fractures (of all types, but particularly Type I), the definitive treatment is almost universally open reduction and internal fixation (ORIF) of the ulnar fracture. Achieving stable anatomical reduction and fixation of the ulna is critical. In the vast majority of cases, once the ulna is anatomically reduced and stably fixed, the radial head will spontaneously reduce due to the intact interosseous membrane and annular ligament. Closed reduction is rarely successful or stable in adults. Excision of the radial head is not indicated for acute Monteggia fractures. External fixation might be considered in highly contaminated open fractures, but ORIF remains the standard. Radial head arthroplasty is indicated for severe comminuted radial head fractures, not primary Monteggia treatment.

Question 14

A 4-year-old presents with a Monteggia Type III fracture. After closed reduction, the radial head appears concentrically reduced on fluoroscopy. What is the appropriate post-reduction immobilization?

Explanation

Correct Answer: A

For Monteggia Type III fractures (lateral/anterolateral radial head dislocation with ulnar metaphyseal fracture), which are common in children, the radial head is typically reduced by direct pressure and manipulation. To maintain reduction, especially after a lateral dislocation, the forearm is immobilized in pronation. This maneuver tightens the interosseous membrane and helps stabilize the radial head against lateral displacement. The elbow is typically flexed to 90 degrees. For Type I (anterior dislocation), immobilization is usually in supination. Therefore, a long-arm cast with the elbow at 90 degrees flexion and the forearm in full pronation is correct for Type III. A sling only would be insufficient immobilization, and the other options do not provide optimal stability for this specific injury type.

Question 15

Following successful ORIF of a Monteggia Type I fracture in an adult, the patient develops a posterior interosseous nerve (PIN) palsy. Which of the following is the most appropriate initial management step?

Explanation

Correct Answer: B

Posterior interosseous nerve (PIN) palsy is a known, albeit uncommon, complication of Monteggia fractures or their treatment. The PIN is vulnerable as it courses through the supinator muscle. Most PIN palsies associated with Monteggia injuries are neurapraxias or axonotmesis due to traction or compression, and a significant proportion resolve spontaneously over several weeks to months. Therefore, the initial management is typically observation, protection, and physiotherapy to prevent contractures, monitoring for recovery. Surgical exploration is generally reserved for cases that show no signs of recovery after 3-6 months. High-dose corticosteroids are not proven effective. EMG/NCS studies are usually performed after 3-4 weeks to establish a baseline or later if recovery is not observed. Immobilization in extension is not indicated and could cause stiffness.

Question 16

A patient undergoes ORIF for a Monteggia Type II fracture. The ulnar fracture is stably fixed. However, the radial head remains persistently dislocated posteriorly. What is the most likely cause of this persistent dislocation?

Explanation

Correct Answer: C

Even after stable anatomical reduction and fixation of the ulnar fracture, persistent dislocation of the radial head can occur. The most common cause, especially in the context of the radial head not spontaneously reducing, is the interposition of soft tissues within the radiocapitellar joint. The torn annular ligament or a portion of the joint capsule can become entrapped, creating a mechanical block to reduction. While malreduction of the ulna can prevent radial head reduction, the question specifies the ulna is 'stably fixed.' Rupture of the lateral collateral ligament complex is possible but less likely to cause an irreducible dislocation compared to mechanical blockage. Heterotopic ossification is a late complication, and implant choice doesn't directly cause irreducible dislocation if the ulna is well-fixed.

Question 17

What is a characteristic feature differentiating a Monteggia equivalent lesion from a classic Monteggia fracture?

Explanation

Correct Answer: B

Monteggia equivalent lesions are a group of injuries that are biomechanically similar to Monteggia fractures (ulnar injury + radial head dislocation) but include additional or slightly different injury patterns. A common Monteggia equivalent is a Monteggia fracture with an associated fracture of the radial head (or neck) in addition to the ulnar fracture and radial head dislocation. Other equivalents include ulnar diaphyseal fracture with concomitant ipsilateral distal radial fracture, or proximal ulna physeal fracture with radial head dislocation. They are not limited to pediatric patients, and the annular ligament is almost always involved (torn or stretched). They do involve an ulnar injury, even if not always a diaphyseal fracture (e.g., physeal). Wrist joint involvement is typical for Essex-Lopresti, not standard Monteggia equivalents.

Question 18

A 55-year-old patient presents with chronic elbow pain, limited pronation/supination, and a palpable radial head dislocation that was missed 6 months ago following a fall. Radiographs confirm a Monteggia Type I malunion with chronic anterior radial head dislocation. Which of the following is the most appropriate management option?

Explanation

Correct Answer: B

A missed or chronic Monteggia fracture in an adult typically requires surgical intervention. For a chronic Monteggia Type I malunion, a staged approach often involves a corrective osteotomy of the malunited ulna to restore forearm length and rotation, followed by open reduction of the radial head. If the annular ligament is significantly disrupted or non-functional, reconstruction (e.g., using a strip of triceps fascia, forearm fascia, or allograft) is often necessary to stabilize the reduced radial head. Closed reduction is ineffective for chronic dislocations. Radial head excision alone in the presence of an intact ulna can lead to superior migration of the radius (Essex-Lopresti type sequela) and wrist pain due to disruption of forearm stability. Dynamic splinting may be used post-operatively but is not the primary treatment. Elbow arthrodesis is a salvage procedure for severe pain and instability, not initial management for a chronic Monteggia.

Question 19

What unique challenge does a Bado Type IV Monteggia fracture present compared to other types?

Explanation

Correct Answer: C

A Bado Type IV Monteggia fracture involves an anterior dislocation of the radial head, similar to Type I, but crucially includes fractures of both the ulna and the radial shaft. This presents a unique surgical challenge because the surgeon must address two diaphyseal fractures (ulna and radius) as well as ensuring concentric reduction and stability of the radial head. The goal remains anatomical reduction and stable fixation of both bone shafts, which typically leads to spontaneous radial head reduction. Other Monteggia types involve only an ulnar fracture. While nerve injuries or open fractures can occur, they are not specific differentiating challenges for Type IV.

Question 20

What is the primary role of the interosseous membrane in a Monteggia fracture?

Explanation

Correct Answer: B

The interosseous membrane (IOM) is a crucial stabilizer of the forearm. In the context of a Monteggia fracture, the IOM acts as a strong anatomical link between the radius and ulna. Its tension is critical; when the ulnar fracture is anatomically reduced and stably fixed, the tension in the IOM typically draws the radial head back into position and helps maintain its reduction by ensuring proper length and alignment of the forearm bones. The IOM does not primarily provide blood supply or prevent compartment syndrome, nor does it solely facilitate pronation/supination (though it influences it). It plays a vital role in force transmission and longitudinal stability.

Question 21

A 42-year-old female sustains a terrible triad injury of the elbow. Operative intervention is planned. Which of the following represents the most widely accepted surgical sequence for restoring stability?

Explanation

The standard surgical algorithm for terrible triad injuries begins with a deep-to-superficial repair. This involves coronoid fixation or anterior capsule reattachment, followed by radial head fixation or arthroplasty, and finally lateral collateral ligament (LCL) repair.

Question 22

A 55-year-old male presents with a fracture of the proximal third of the ulna with apex posterior angulation and an associated posterior dislocation of the radial head. According to the Bado classification, what type of Monteggia lesion is this?

Explanation

A Bado Type II Monteggia fracture is characterized by a diaphyseal or metaphyseal fracture of the ulna with apex posterior angulation and posterior dislocation of the radial head. It is the most common type seen in adults and is frequently associated with radial head fractures.

Question 23

During the repair of the lateral ulnar collateral ligament (LUCL) in a terrible triad injury, identifying the correct isometric point on the humerus is critical to prevent joint stiffness or instability. Where is the anatomical origin of the LUCL?

Explanation

The LUCL originates at the isometric center of the capitellum on the lateral epicondyle and inserts on the supinator crest of the ulna. Proper isometric placement of the humeral anchor is essential to maintain uniform ligament tension throughout the arc of elbow motion.

Question 24

A 28-year-old female sustains a Bado Type I Monteggia fracture-dislocation. On examination, she is unable to actively extend her thumb and MCP joints but has intact wrist extension with radial deviation. Which of the following is the most appropriate management for this neurologic deficit?

Explanation

The patient has a posterior interosseous nerve (PIN) palsy, which is the most common neurologic complication in Bado Type I and III Monteggia fractures. It is typically a neurapraxia that resolves spontaneously, making 3 to 6 months of observation the standard of care.

Question 25

During a terrible triad repair, the surgeon replaces a highly comminuted radial head with a metallic prosthesis. Postoperatively, radiographs show widening of the lateral ulnohumeral joint space. What is the most likely consequence of this specific technical error?

Explanation

Widening of the lateral ulnohumeral joint indicates overstuffing of the radiocapitellar joint by choosing a radial head prosthesis that is too long or thick. This increases pressure on the capitellum, leading to early cartilage wear, restricted flexion, and potential capitellar osteonecrosis.

Question 26

A surgeon is performing open reduction and internal fixation (ORIF) of a Bado Type I Monteggia fracture in an adult. After achieving anatomic reduction and rigid plate fixation of the ulna, the radial head remains anteriorly dislocated. What is the most appropriate next step?

Explanation

In a Monteggia fracture, the radial head usually reduces spontaneously once the ulna is anatomically restored. If it remains dislocated, open exploration of the radiocapitellar joint is required to remove interposed structures, most commonly the annular ligament or joint capsule.

Question 27

A 38-year-old male sustains a terrible triad injury. Imaging shows a Regan-Morrey Type I (tip) coronoid fracture. Which of the following describes the most appropriate management of this specific coronoid fragment during surgery?

Explanation

Small Type I (tip) coronoid fractures represent an avulsion of the anterior capsule and are often too small for screw fixation. They provide critical soft-tissue stability and are best managed by capturing the capsule and fragment using a suture lasso technique tied through the proximal ulna.

Question 28

Following surgical repair of a terrible triad injury of the elbow, the patient is started on early active range of motion. To maximally protect the lateral collateral ligament (LCL) repair during elbow extension, in what position should the forearm be maintained?

Explanation

Pronation of the forearm tightens the medial soft tissues and the extensor origin, effectively protecting the LCL repair from varus and posterolateral rotatory stress. Early active motion is typically performed with the forearm in pronation.

Question 29

A 6-year-old boy presents with an elbow injury. Radiographs reveal a fracture of the ulnar metaphysis with a lateral dislocation of the radial head. What Bado classification does this injury represent?

Explanation

A Bado Type III Monteggia lesion involves a metaphyseal fracture of the ulna with a lateral dislocation of the radial head. It occurs almost exclusively in children and is frequently associated with posterior interosseous nerve (PIN) injuries.

Question 30

In the setting of a terrible triad injury, at what point during the operation is the repair of the medial collateral ligament (MCL) primarily indicated?

Explanation

Routine repair of the MCL is not indicated in all terrible triad injuries. It is typically explored and repaired only if the elbow demonstrates residual instability in extension after the coronoid, radial head, and lateral-sided structures have been securely fixed.

Question 31

When managing a terrible triad injury, a surgeon chooses an extensile lateral approach utilizing the Kaplan interval to access both the radial head and the coronoid. Which of the following nerve structures is at greatest risk when extending this interval distally?

Explanation

The Kaplan interval utilizes the plane between the extensor digitorum communis (EDC) and the extensor carpi radialis brevis (ECRB). Extending this interval distally places the posterior interosseous nerve (PIN) at significant risk as it crosses the proximal radius within the supinator muscle.

Question 32

A 32-year-old male sustains a Bado Type I Monteggia fracture. Which of the following represents the gold standard of treatment for the ulnar shaft fracture in this adult patient?

Explanation

In adults, all Monteggia fractures require open reduction and internal fixation (ORIF) of the ulna to ensure anatomic alignment and rigid stability. Compression plating is the gold standard because intramedullary devices do not provide adequate rotational control.

Question 33

Which of the following is the most common complication following surgical treatment of a terrible triad injury of the elbow?

Explanation

Post-traumatic stiffness is the most common complication following the surgical treatment of terrible triad injuries. To combat this, achieving a stable repair that permits early active motion is a primary surgical goal.

Question 34

While reviewing elbow trauma cases, a resident notes a fracture involving the anteromedial facet of the coronoid. This specific fracture pattern is most commonly associated with which mechanism and injury pattern?

Explanation

Fractures of the anteromedial facet of the coronoid are the hallmark of varus posteromedial rotatory instability (VPMRI). They typically occur from a varus force coupled with an axial load and are often associated with LCL tears, requiring specific fixation to prevent rapid arthrosis.

Question 35

An 8-year-old child presents with a progressive cubitus valgus deformity and tardy ulnar nerve palsy. Radiographs reveal a chronic anteriorly dislocated radial head and a malunited proximal ulna fracture sustained 18 months ago. What is the most appropriate surgical treatment?

Explanation

In a child with a chronic Monteggia fracture-dislocation, the standard treatment involves a corrective opening-wedge osteotomy of the ulna to restore length and alignment. This is combined with open reduction of the radial head, as radial head excision is contraindicated in growing children.

Question 36

A 45-year-old male is involved in a motor vehicle collision. Radiographs of the forearm demonstrate fractures of both the radial and ulnar shafts, along with an anterior dislocation of the radial head. How is this injury classified?

Explanation

A Bado Type IV Monteggia lesion is defined by a dislocation of the radial head (usually anterior) accompanied by diaphyseal fractures of both the radius and the ulna. It requires rigid internal fixation of both forearm bones.

Question 37

When performing surgical reconstruction for a terrible triad injury of the elbow, which of the following represents the most widely accepted sequential order of repair?

Explanation

The standard protocol for terrible triad reconstruction is 'inside-out'. This begins with fixing the coronoid, followed by the radial head (fixation or arthroplasty), and then the lateral collateral ligament (LCL) complex. The MCL or a hinged external fixator is addressed last only if residual instability exists.

Question 38

A 40-year-old male sustains a Bado Type II Monteggia fracture-dislocation. Based on this specific injury pattern, what additional associated injury is most likely to be present?

Explanation

Bado Type II (posterior) Monteggia fractures in adults are complex injuries highly associated with radial head and neck fractures. They are often considered variants of fracture-dislocations that share features with terrible triad injuries.

Question 39

During open reduction and internal fixation of a radial head fracture in a terrible triad injury, screws are placed in the 'safe zone' to prevent impingement. Which of the following accurately describes this zone?

Explanation

The safe zone for radial head hardware placement is a 90 to 110-degree non-articulating arc on the lateral aspect of the radial head. This zone avoids impingement on the lesser sigmoid notch of the ulna during forearm pronation and supination.

Question 40

A 25-year-old female presents with a closed Bado Type I Monteggia fracture and an isolated inability to extend her fingers and thumb at the metacarpophalangeal joints. What is the most appropriate management of her nerve injury?

Explanation

Posterior interosseous nerve (PIN) palsy is the most common neurologic injury associated with Bado I and III Monteggia fractures. It is almost always a neuropraxia that recovers spontaneously, warranting observation for 3 to 6 months before considering exploration.

Question 41

To restore posterolateral rotatory stability during terrible triad surgery, the lateral ulnar collateral ligament (LUCL) must be repaired. Where is the correct distal insertion site of the LUCL?

Explanation

The LUCL originates at the lateral epicondyle and inserts distally on the supinator crest of the proximal ulna. Restoring this footprint is critical to preventing posterolateral rotatory instability.

Question 42

Which of the following best describes the typical mechanism of injury resulting in a terrible triad of the elbow?

Explanation

The terrible triad (elbow dislocation, radial head fracture, coronoid fracture) characteristically results from a fall onto an outstretched hand causing an axial load, a valgus force, and posterolateral rotation.

Question 43

In a terrible triad injury, the coronoid fracture is often a small transverse tip fragment (Regan-Morrey Type I or II). What is the primary biomechanical rationale for surgically stabilizing this small fragment?

Explanation

Small tip fractures of the coronoid involve the insertion of the anterior joint capsule. Repairing these fragments (often via suture lasso) restores the anterior capsular restraint, which is crucial for preventing recurrent posterior subluxation of the elbow.

Question 44

During surgery for a terrible triad injury, the radial head is found to be highly comminuted with more than 3 fragments and is deemed irreparable. What is the most appropriate management of the radial head?

Explanation

In the setting of a terrible triad, radial head excision alone leads to severe instability because the primary collateral ligaments are disrupted. Metallic radial head arthroplasty is indicated to restore the lateral column buttress.

Question 45

A surgeon performs a radial head arthroplasty for a terrible triad injury but accidentally sizes the implant too large. Which of the following complications is most likely to occur as a direct result?

Explanation

Oversizing or 'overstuffing' the radiocapitellar joint increases joint contact pressures significantly. This leads to accelerated capitellar wear, pain, and restricted elbow range of motion, particularly in flexion.

Question 46

A 6-year-old boy presents to the emergency department with a closed Bado Type I Monteggia fracture. What is the standard initial treatment of choice for this patient?

Explanation

Unlike adult Monteggia fractures which require rigid internal fixation, pediatric Monteggia fractures can almost always be successfully managed non-operatively with closed reduction and long-arm casting.

Question 47

Following fixation of the coronoid and radial head, and repair of the LCL in a terrible triad injury, the elbow subluxates posteriorly when extended past 30 degrees. What is the most appropriate next intraoperative step?

Explanation

If the elbow remains unstable after addressing the coronoid, radial head, and LCL, it indicates severe medial-sided injury or gross global instability. The next step is to repair the MCL and/or apply a hinged external fixator.

Question 48

A 10-year-old child presents with a 6-month history of a missed anterior Monteggia fracture. Which of the following physical examination findings is most characteristic of this chronic unreduced state?

Explanation

A chronically anteriorly dislocated radial head acts as a mechanical block. This typically restricts terminal elbow flexion and limits full forearm rotation.

Question 49

When evaluating pediatric elbow radiographs for a subtle Monteggia variant, which radiographic line is critical to assess to rule out a radial head dislocation?

Explanation

The radiocapitellar line should bisect the capitellum on every radiographic view, irrespective of the degree of elbow flexion. Failure of this line to intersect the capitellum indicates a radial head dislocation.

Question 50

A Bado Type III Monteggia fracture, characterized by lateral dislocation of the radial head, is most frequently associated with which type of ulnar fracture?

Explanation

Bado Type III fractures predominantly occur in pediatric populations. They are typically associated with a greenstick fracture of the proximal ulnar metaphysis along with a lateral radial head dislocation.

Question 51

Following a stable and anatomic surgical reconstruction of a terrible triad injury, what is the most widely recommended early rehabilitation protocol?

Explanation

Early active motion is crucial to prevent stiffness. Performing exercises with the forearm in pronation tightens the intact medial structures and protects the repaired lateral collateral ligament (LCL) from varus stress.

Question 52

An adult patient undergoes open reduction and internal fixation of a Bado Type I Monteggia fracture. Intraoperatively, after plating the ulna, the radial head remains anteriorly dislocated. What is the most common cause of this failure of reduction?

Explanation

The radial head follows the alignment of the ulna. If the radial head fails to reduce in a Monteggia fracture, the most common reason is that the ulnar length, alignment, or rotation has not been anatomically restored.

Question 53

During a radial head replacement in a terrible triad injury, which anatomical landmark is best used to determine the correct proximal-to-distal height of the radial head implant?

Explanation

The articulating margin of the radial head implant should sit level with the proximal edge of the lesser sigmoid notch of the ulna. This ensures proper tracking and avoids overstuffing or under-sizing the joint.

Question 54

A patient presents with an anteromedial facet fracture of the coronoid process. This specific fracture pattern is pathognomonic for which specific mechanism of elbow instability?

Explanation

Anteromedial facet fractures of the coronoid result from a varus force combined with posteromedial rotation. This injury pattern typically involves LCL rupture and leads to severe varus posteromedial rotatory instability.

Question 55

A 45-year-old male undergoes complex surgical fixation for a terrible triad injury. Which of the following prophylactic measures is recommended to reduce his significant risk of developing heterotopic ossification (HO)?

Explanation

Complex elbow trauma carries a high risk of heterotopic ossification. Prophylaxis with NSAIDs (such as indomethacin) or a single localized fraction of radiation is standard to mitigate this risk.

Question 56

When utilizing a bone anchor to repair the avulsed lateral collateral ligament complex during a terrible triad reconstruction, where is the exact anatomic isometric origin on the lateral humerus?

Explanation

The LUCL originates at the isometric point on the lateral epicondyle, which corresponds to the central axis of elbow rotation (capitellum). Proper isometric placement ensures the ligament maintains appropriate tension throughout the flexion-extension arc.

Question 57

A 45-year-old female presents with a terrible triad injury of the elbow. During surgical reconstruction, what is the most widely accepted sequential order of repair to restore elbow stability?

Explanation

The standard surgical sequence for a terrible triad injury works deep to superficial: fixing the coronoid/anterior capsule first, followed by the radial head, and finally repairing the LUCL. Reassessing stability afterward determines if MCL repair or an external fixator is needed.

Question 58

A 32-year-old male sustains a Bado Type I Monteggia fracture-dislocation. Following anatomic rigid plate fixation of the ulna, intraoperative fluoroscopy reveals that the radial head remains subluxated anteriorly. What is the most likely cause of this persistent subluxation?

Explanation

In Monteggia fractures, the radial head should spontaneously reduce once the ulnar anatomy is perfectly restored. Persistent subluxation is most commonly caused by malreduction of the ulna, particularly a failure to restore its length or anatomic apex-posterior bow.

Question 59

A 50-year-old male undergoes radial head arthroplasty as part of a terrible triad reconstruction. Postoperatively, he has persistent medial elbow pain, a 15-degree loss of terminal flexion, and widening of the medial joint line on AP radiographs. What is the most likely iatrogenic cause of these findings?

Explanation

Overstuffing the radiocapitellar joint with a radial head prosthesis that is too long causes increased pressure on the capitellum, restricted flexion, and gaping of the medial radioulnar joint due to tension on the medial structures.

Question 60

Which of the following describes the most appropriate management for a closed Bado Type III Monteggia fracture in a 6-year-old child who develops a complete posterior interosseous nerve (PIN) palsy upon presentation?

Explanation

PIN palsies in pediatric Monteggia fractures are typically neuropraxias resulting from nerve stretch over the dislocated radial head. The standard of care is closed reduction and casting with clinical observation, as spontaneous recovery usually occurs within 3 to 6 months.

Question 61

During the lateral approach for a terrible triad injury, the surgeon decides to use the Kaplan interval instead of the Kocher interval to access the radial head. Between which two muscles does the Kaplan approach pass, and what structure is at higher risk compared to the Kocher approach?

Explanation

The Kaplan approach utilizes the interval between the extensor digitorum communis (EDC) and the extensor carpi radialis brevis (ECRB). It places the PIN at greater risk distally compared to the Kocher approach (ECU and anconeus), though it generally preserves the LUCL better.

Question 62

In the setting of a terrible triad injury, an O'Driscoll Type 2 (anteromedial facet) coronoid fracture is identified. What specific pattern of elbow instability is classically associated with this fracture subtype if left unaddressed?

Explanation

Anteromedial facet fractures of the coronoid result in loss of the buttress against varus forces, classically causing varus posteromedial rotatory instability (VPMRI). They typically require fixation with an anteromedial buttress plate to restore stability.

Question 63

A 40-year-old male requires plate fixation for a comminuted radial head fracture in a terrible triad injury. To prevent impingement on the proximal radioulnar joint during forearm rotation, the plate must be placed within the "safe zone." How is this safe zone defined anatomically?

Explanation

The safe zone for radial head plating is approximately a 90 to 110-degree arc on the non-articulating lateral surface of the radial head. It corresponds distally to the area between the radial styloid and Lister's tubercle with the forearm in neutral rotation.

Question 64

After completing the fixation of the coronoid, radial head, and repairing the LUCL in a terrible triad injury, the elbow remains unstable and continues to dislocate posteriorly at 30 degrees of flexion. What is the most appropriate next step in management?

Explanation

If the elbow remains unstable (specifically tending to dislocate at >30 degrees of flexion) after addressing the coronoid, radial head, and LUCL, the next step is either to repair the MCL or to apply a hinged elbow external fixator to maintain a concentric reduction.

Question 65

A 55-year-old male sustains a Bado Type II Monteggia fracture. Which of the following associated elbow injuries is most frequently seen with this specific adult Monteggia variant?

Explanation

Bado Type II Monteggia fractures (posterior dislocation of the radial head with an apex-posterior ulnar fracture) are the most common type in adults. They are frequently associated with a radial head fracture and coronoid fracture, essentially making them Monteggia-variant fracture-dislocations.

Question 66

A 10-year-old boy presents with a missed Bado Type I Monteggia fracture 8 months after the initial injury. The patient has progressive valgus deformity and loss of elbow flexion. What is the most critical surgical step required to successfully maintain a reduced radial head in this chronic setting?

Explanation

In chronic missed Monteggia fractures in children, simply pulling the radial head back into place is insufficient due to relative ulnar shortening and overgrowth of the radius. An ulnar osteotomy (angulation and lengthening) is critical to decompress the radiocapitellar joint and maintain reduction.

Question 67

When repairing the lateral ulnar collateral ligament (LUCL) during a terrible triad reconstruction, anatomic placement of the suture anchor on the humerus is crucial. What is the correct anatomic origin of the LUCL?

Explanation

The LUCL originates on the lateral epicondyle at the isometric point corresponding to the center of capitellar rotation. It inserts distally onto the supinator crest of the ulna.

Question 68

Which of the following techniques is considered the "gold standard" for achieving fixation of a comminuted, transverse Type I (tip) coronoid fracture during a terrible triad reconstruction?

Explanation

Small, transverse Type 1 coronoid tip fractures often cannot hold a screw. The "suture lasso" technique, capturing the anterior capsule and passing sutures through drill holes in the proximal ulna, provides robust fixation and restores the anterior stabilizing buttress.

Question 69

A surgeon approaches a complex proximal ulna fracture with radial head dislocation using the Boyd approach. Which of the following complications is historically highly associated with the extensive muscle stripping required by this approach?

Explanation

The Boyd approach exposes the proximal ulna and radius by elevating the supinator and anconeus off the ulna. This extensive subperiosteal stripping in the region of the interosseous membrane carries a notoriously high risk of developing proximal radioulnar synostosis.

Question 70

A 28-year-old male undergoes surgical treatment for a terrible triad injury. Postoperatively, what forearm position is theoretically most protective of the repaired lateral ulnar collateral ligament (LUCL) during early range of motion exercises?

Explanation

Forearm pronation tensions the medial soft tissues and the intact medial hinge, thereby crossing the radius over the ulna and protecting the repaired lateral side (LUCL) from varus stress and subluxation during early rehabilitation.

Question 71

In evaluating a pediatric patient with an isolated, traumatic bowing (plastic deformation) of the ulna and an intact radius, which of the following occult injuries MUST be explicitly ruled out with high-quality radiographs?

Explanation

Traumatic plastic deformation of the ulna in a child effectively shortens the bone and changes its bow. This is a classic Monteggia variant, and the clinician must meticulously assess the radiocapitellar alignment to rule out an occult radial head dislocation.

Question 72

You are templating a radial head arthroplasty for an irreparable radial head fracture in a terrible triad injury. What intraoperative landmark is most reliable for determining the correct height of the radial head prosthesis?

Explanation

To avoid overstuffing the joint, the articular surface of the radial head prosthesis should sit flush with, or up to 1-2 mm proximal to, the proximal edge of the lesser sigmoid notch of the ulna when the elbow is reduced.

Question 73

What is the most common long-term complication following operative management of a terrible triad injury?

Explanation

Post-traumatic elbow stiffness, particularly loss of terminal extension, is the most common complication following the surgical treatment of terrible triad injuries. Early, stable fixation allowing for immediate range of motion is critical to minimize this.

Question 74

According to the Bado classification, a fracture of the ulnar diaphysis with lateral dislocation of the radial head is classified as which type?

Explanation

A Bado Type III Monteggia fracture is characterized by a metaphyseal fracture of the ulna with a lateral dislocation of the radial head. It is most commonly seen in pediatric patients.

Question 75

A patient presents with an anterior elbow dislocation, a comminuted radial head fracture, and a diaphyseal fracture of both the radius and the ulna. Based on the classification of fracture-dislocations of the forearm, how is this injury categorized?

Explanation

Bado Type IV Monteggia fractures are characterized by fractures of both the radius and ulna shafts accompanied by an anterior dislocation of the radial head.

Question 76

During the reduction of a terrible triad injury, the surgeon performs the 'hanging arm test' under fluoroscopy. What is the primary purpose of this maneuver?

Explanation

The hanging arm test places the elbow in extension to allow gravity to provide a valgus stress. It is used after coronoid, radial head, and LCL fixation to assess the competence of the MCL and determine if further stabilization is needed.

Question 77

A 45-year-old male sustains a terrible triad injury of the elbow. Operative management is planned. To optimize biomechanical stability, what is the most widely accepted sequence of structural repair?

Explanation

The standard sequence of repair in a terrible triad injury proceeds from deep to superficial: coronoid fixation, radial head repair or replacement, and LCL repair. MCL repair or a hinged external fixator is only added if the elbow remains persistently unstable after the lateral side is reconstructed.

Question 78

A 32-year-old female presents with a Bado Type I Monteggia fracture-dislocation. She exhibits an inability to actively extend her thumb and fingers at the metacarpophalangeal joints, though wrist extension is preserved with radial deviation. Which nerve is most likely injured?

Explanation

The PIN is the most commonly injured nerve in Bado Type I and III Monteggia fractures due to anterior or lateral radial head dislocation tethering the nerve. It typically presents as a neurapraxia with spontaneous recovery expected.

Question 79

During surgery for a terrible triad injury, a severely comminuted radial head is replaced with a modular prosthesis. Postoperatively, radiographs reveal a widened medial joint clear space, and the patient lacks full elbow flexion and extension. What is the most likely cause?

Explanation

Overstuffing the joint with a radial head prosthesis that is too long "cams" the joint open medially, causing a widened medial clear space. This increases joint contact pressures and significantly restricts the range of motion.

Question 80

A 50-year-old male undergoes open reduction and internal fixation for a Bado Type II Monteggia fracture. Following rigid plate fixation of the ulna, the radial head remains subluxated posteriorly. What is the most critical next step in management?

Explanation

In Monteggia fractures, the key to reducing the radial head is anatomic restoration of the ulna's length and alignment. Persistent radial head subluxation after ulnar plating indicates ulnar malreduction, which must be addressed first.

Question 81

A patient with an elbow fracture-dislocation is found to have an O'Driscoll anteromedial facet fracture of the coronoid. If left untreated, this specific fracture pattern is most likely to result in which of the following complications?

Explanation

The anteromedial facet of the coronoid is critical for resisting varus forces. Failure to fix these fractures typically leads to varus posteromedial rotatory instability and rapid onset of elbow arthrosis.

Question 82

When evaluating pediatric forearm radiographs for a suspected Monteggia equivalent injury, which radiographic line is most reliable to confirm a reduced radiocapitellar joint?

Explanation

The radiocapitellar line is drawn through the center of the radial shaft and neck. To rule out a radial head dislocation, this line must intersect the center of the capitellum on every radiographic view, regardless of the elbow's flexion angle.

Question 83

During the lateral reconstruction phase of a terrible triad injury, the LCL complex must be reattached to its anatomic footprint to ensure isometric stability. Where is the precise isometric origin of the LCL on the humerus?

Explanation

The isometric point for the LCL (specifically the lateral ulnar collateral ligament, LUCL) is located at the center of rotation of the capitellum. This corresponds to the base of the lateral epicondyle.

Question 84

A 6-year-old child presents with an isolated plastic deformation of the ulna and an anterior radial head dislocation that occurred 3 weeks ago. Closed reduction attempts in the emergency department fail. What is the most appropriate management?

Explanation

Plastic deformation of the ulna acts as a Bado Type I Monteggia equivalent. Failure to correct the ulnar bowing prevents stable reduction of the radial head; therefore, an ulnar osteotomy is required.

Question 85

After completing rigid internal fixation of the coronoid and radial head, and repairing the LCL in a terrible triad injury, the elbow drops out of joint when extended past 30 degrees. What is the most appropriate next step?

Explanation

If the elbow remains unstable in extension after addressing the coronoid, radial head, and LCL, it indicates severe capsuloligamentous injury involving the MCL. The next step is MCL repair or a hinged external fixator to allow early range of motion.

Question 86

Which of the following characteristics is most closely associated with a Bado Type II Monteggia fracture-dislocation compared to other Bado types?

Explanation

Bado Type II involves posterior dislocation of the radial head and a posterior angulated ulnar fracture. It is highly associated with elbow fracture-dislocations, including concomitant radial head and coronoid fractures.

Question 87

To mitigate the high risk of heterotopic ossification following operative management of a terrible triad injury, what is the most appropriate pharmacological prophylaxis?

Explanation

Indomethacin (a nonsteroidal anti-inflammatory drug) is frequently utilized as prophylaxis against heterotopic ossification following severe elbow trauma. Radiation therapy is another prophylactic option.

Question 88

When utilizing the Kaplan approach for exposure of the radial head in a terrible triad injury, the surgical interval is developed between which two muscle bellies?

Explanation

The Kaplan approach utilizes the interval between the EDC and the ECRB. In contrast, the Kocher approach utilizes the interval between the ECU and the anconeus.

Question 89

In the surgical treatment of an adult with a Bado Type I Monteggia fracture, which surface of the ulna provides the best biomechanical position for plate placement to utilize the tension band principle?

Explanation

The posterior surface of the ulna is the tension side. Placing the plate posteriorly utilizes the tension band principle, providing the most biomechanically stable fixation.

Question 90

The coronoid process acts as the primary bony constraint to which of the following forces in the elbow joint?

Explanation

The coronoid is the primary bony restraint against posterior translation of the ulna relative to the distal humerus, acting as an anterior buttress. It also provides significant stability against varus stress via its anteromedial facet.

Question 91

A Bado Type III Monteggia fracture-dislocation is radiographically defined by which of the following features?

Explanation

Bado Type III injuries feature a lateral or anterolateral dislocation of the radial head combined with a fracture of the proximal ulnar metaphysis. This pattern is primarily seen in pediatric patients.

Question 92

During the postoperative rehabilitation of a successfully reconstructed terrible triad injury (coronoid, radial head, and LCL repaired), immediate active-assisted range of motion is initiated. To maximally protect the LCL repair during elbow flexion and extension, the forearm should be held in what position?

Explanation

Pronation of the forearm positions the intact or repaired medial structures to act as a hinge, relaxing the LCL complex and protecting the lateral repair from varus stress during early range of motion.

Question 93

The accepted mechanism of injury for a Bado Type I Monteggia fracture is most commonly associated with:

Explanation

The most widely accepted mechanism for Bado Type I (anterior) injuries is forced hyperpronation during a fall on an outstretched hand, which leverages the radius anteriorly while fracturing the ulna.

Question 94

When performing open reduction and internal fixation of the radial head using a plate, the hardware must be placed within the "safe zone" to prevent impingement on the proximal radioulnar joint (PRUJ). This safe zone corresponds to an arc of approximately how many degrees?

Explanation

The "safe zone" for radial head hardware placement spans approximately 90 to 110 degrees on the non-articulating lateral aspect of the radial head. It is defined by an arc from the radial styloid to Lister's tubercle with the forearm in neutral rotation.

Question 95

Which of the following structures must be preserved or carefully repaired during the Boyd approach to the proximal ulna to prevent a debilitating complication in Monteggia fracture management?

Explanation

The Boyd approach reflects the supinator and anconeus off the proximal ulna. If dissection proceeds too far anteriorly or distally without protecting the lateral ligamentous complex, the LUCL can be compromised, resulting in iatrogenic posterolateral rotatory instability (PLRI).

Question 96

In the setting of a terrible triad injury, if a Type 1 (tip) coronoid fracture is deemed too small for screw fixation or a plate, what is the most appropriate surgical technique to stabilize it?

Explanation

For small, comminuted, or unfixable coronoid tip fractures, a suture lasso technique through the anterior capsule, passed through drill holes in the proximal ulna, effectively restores anterior stability.

100 High-Yield Orthopedic MCQs: Shoulder & Elbow | Mock Exam 251

ABOS Part I Orthopaedic Review: Elbow Terrible Triad & Monteggia Fractures | Part 22230

Key Takeaway

ABOS Part I Orthopaedic Review: Elbow Terrible Triad & Monteggia Fractures | Part 22230

Chapter Index