ABOS Part I & AAOS OITE Pelvic Ring Injury Review: Diagnosis, Management, Complications | Part 21567

Correct Answer: C

The patient's presentation of persistent, activity-limiting pain, a noticeable limp, and radiographic evidence of progressive vertical displacement (1.5 cm) 6 months after initial fixation, despite intact hardware, is the classic definition of residual pelvic instability. The case explicitly states that residual instability refers to 'the continued or recurrent mechanical incompetence of the pelvic ring after initial treatment, either surgical or non-operative,' often masked by temporary fixation or insufficient evaluation, leading to chronic pain and functional impairment. The progressive displacement is a key indicator of ongoing mechanical incompetence.

Option A (Acute pelvic instability requiring immediate re-stabilization) is incorrect because 'acute' refers to the immediate post-injury phase. This patient is 6 months post-injury, and the instability has developed or persisted chronically.

Option B (A stable malunion of the posterior pelvic ring) is incorrect. While there is malalignment, the key feature is that it is 'progressive' and 'symptomatic,' indicating ongoing instability rather than a stable, albeit malaligned, union. A stable malunion would typically not show progressive displacement.

Option D (Expected post-traumatic pain, manageable with conservative measures) is incorrect. While some post-traumatic pain is expected, the severity (activity-limiting), the functional impairment (limp), and especially the objective radiographic evidence of progressive displacement indicate a mechanical problem beyond typical post-traumatic pain that would likely not be resolved with conservative measures alone, as per the 'Indications for Intervention' section.

Option E (Hardware failure without associated instability) is incorrect. The case states 'despite intact hardware,' implying the hardware itself has not failed (e.g., fractured or pulled out). Even if hardware failure were present, the primary issue is the resulting instability, not just the hardware failure in isolation.

Correct Answer: D

The case content, under 'Anatomy of the Pelvic Ring' and 'Posterior Pelvic Ring,' explicitly states: 'The interosseous ligaments are the primary stabilizers, preventing distraction of the SI joint.' It further elaborates that the posterior SI ligaments (which include the interosseous) are 'extremely strong' and 'predominantly resisted by the posterior SI ligaments and the mechanical interlock of the sacrum within the iliac wings' for shear stability.

Option A (Anterior Sacroiliac Ligaments) is incorrect. The case states these are 'thinner' and 'less critical for stability than posterior ligaments.'

Option B (Sacrospinous Ligaments) is incorrect. While they 'resist external rotation and vertical shear forces,' they are not described as the 'primary stabilizers preventing distraction of the SI joint' in the same way the interosseous ligaments are.

Option C (Iliolumbar Ligaments) is incorrect. These ligaments 'connect the transverse processes of L4 and L5 to the iliac crest' and 'contribute to lumbopelvic stability and transfer lumbar forces to the pelvis,' but they are not the primary stabilizers of the SI joint itself against distraction or vertical shear.

Option E (Long Posterior Sacroiliac Ligaments) is incorrect. While they are part of the strong posterior ligamentous complex and 'resist external rotation and vertical sheer forces,' the text specifically identifies the 'interosseous ligaments' as the 'primary stabilizers, preventing distraction of the SI joint.'

Correct Answer: C

The case content, under 'Biomechanics of Pelvic Stability' and 'Radiographic insights,' explicitly states: 'The "crescent sign" (avulsion of the iliac cortical rim) is pathognomonic for severe posterior ligamentous injury.' This sign indicates a significant disruption of the strong posterior ligamentous complex, which is crucial for pelvic stability.

Option A (Anterior sacroiliac ligamentous injury) is incorrect. While anterior SI ligaments can be injured, the crescent sign specifically points to the posterior complex due to the strong attachments to the iliac rim.

Option B (Sacrotuberous ligament avulsion) is incorrect. The sacrotuberous ligament connects the sacrum/PSIS to the ischial tuberosity. While its avulsion indicates significant injury, the 'crescent sign' specifically refers to the iliac cortical rim avulsion, which is more directly associated with the posterior SI ligaments.

Option D (Iliolumbar ligamentous sprain) is incorrect. Iliolumbar ligaments connect the lumbar spine to the iliac crest and are not directly associated with the 'crescent sign' at the SI joint.

Option E (Pubic symphysis instability) is incorrect. Pubic symphysis instability is an anterior ring injury and would manifest as symphyseal widening, not an iliac cortical rim avulsion.

Correct Answer: B

The case content, under 'Summary of Key Literature / Guidelines' and 'Tile Classification,' describes: 'Type B: Rotationally unstable, vertically stable (e.g., "open book," lateral compression). Disruption of anterior and partial posterior ligaments.' The patient's initial injury, with a 'widely diastased pubic symphysis' (anterior disruption) and 'partial disruption of the posterior sacroiliac ligaments, without significant vertical displacement,' perfectly matches the description of a Tile Type B injury.

Option A (Type A: Stable) is incorrect. Type A injuries are stable and involve minimal disruption, such as isolated rami fractures or avulsions. This patient's injury involves significant anterior and partial posterior disruption, making it unstable.

Option C (Type C: Rotationally and vertically unstable) is incorrect. Type C injuries involve complete disruption of both anterior and posterior ligaments, leading to vertical instability. The patient's injury explicitly states 'without significant vertical displacement,' ruling out Type C.

Option D (Young & Burgess Vertical Shear) is incorrect. While Young & Burgess is a valid classification, the question specifically asks for the Tile classification. A Vertical Shear injury would correspond to a Tile Type C due to its vertical instability.

Option E (AO/OTA Type 61-C3) is incorrect. While AO/OTA is a comprehensive classification, the question specifically asks for the Tile classification. Furthermore, a C3 injury in AO/OTA would imply a highly unstable, complex injury, likely with vertical instability, which is not described for this patient's initial injury.

Correct Answer: E

The case content, under 'Indications for Intervention,' lists several operative indications. This patient presents with multiple, clear indications:

• Persistent Pain: 'Unremitting or activity-limiting pain localized to the pelvis or lumbosacral region, not responsive to conservative management.' The patient has 'chronic, severe, and activity-limiting pain' refractory to 'extensive physical therapy and multiple SI joint injections.'
• Progressive Deformity: 'Radiographic evidence of ongoing displacement, widening of the pubic symphysis, or vertical migration of the hemipelvis (e.g., >1 cm displacement).' The patient has 'persistent 1.2 cm diastasis of the right SI joint and a 0.8 cm vertical migration of the right hemipelvis, which has progressed from 0.5 cm.'
• Functional Impairment: 'Significant gait disturbance (e.g., waddling gait, limb length discrepancy), difficulty with weight-bearing, or inability to perform activities of daily living due to instability.' The patient has a 'significant waddling gait, requires a walker for ambulation, and reports difficulty with all activities of daily living.'

While 'Risk of future degenerative changes' is a valid long-term concern for untreated instability, the immediate and most compelling reasons for surgery are the severe pain, functional impairment, and progressive radiographic deformity. Since all listed options (A, B, C) are strong, independent indications for surgery, and the patient exhibits all of them, 'All of the above' is the most accurate answer.

Correct Answer: C

The case content, under 'Pre-Operative Planning & Patient Positioning' and 'Detailed Radiographic Assessment,' highlights the importance of various imaging modalities. For complex fracture morphology, sacral foramina, relationship to neural structures, and planning screw trajectories, it states: 'Computed Tomography (CT) Scan: ...Axial Slices: Detailed visualization of fracture patterns, sacral foramina, SI joint pathology, and relationship of bone fragments to neural structures. Essential for identifying missed sacral fractures... 3D Reconstructions: Invaluable for understanding complex fracture morphology, planning screw trajectories (especially for SI screws), and simulating reduction maneuvers. This allows for precise measurement of any residual displacement and angulation.'

Option A (Anteroposterior (AP) Pelvis Radiographs) and Option B (Inlet and Outlet Pelvis Radiographs) are important for initial assessment of overall alignment and gross displacement, but they lack the detailed 3D information needed for complex screw trajectory planning and precise assessment of neural structures.

Option D (Magnetic Resonance Imaging (MRI)) is best for evaluating soft tissue injuries (ligamentous integrity), neurological assessment (nerve root compression), and occult fractures. While useful for soft tissue, it is not the primary modality for detailed bony morphology and screw trajectory planning in the same way CT is.

Option E (Dynamic Stress Radiographs) are useful for unmasking subtle instability not apparent on static views, particularly for dynamic components of residual instability, but they do not provide the detailed anatomical information for surgical planning of screw placement.

Correct Answer: C

The case content, under 'Complications & Management' and 'Neurological Injury,' explicitly warns about nerve injuries during iliosacral screw placement: 'For lumbosacral plexus/sciatic nerve (often with SI screw malposition or direct trauma).' The S1 nerve root is particularly vulnerable during S1 iliosacral screw placement, as it exits the S1 foramen. A 'twitching of the great toe' is a classic sign of S1 nerve root irritation or impingement, as the S1 nerve root contributes to plantarflexion and sensation in the foot, including the great toe.

Option A (Femoral nerve) and Option B (Obturator nerve) are typically at risk with anterior approaches or acetabular fixation, not directly with posterior iliosacral screw placement into S1.

Option D (Superior gluteal nerve) is at risk during open posterior approaches, particularly with extensive dissection around the greater sciatic notch, but less directly from a percutaneous S1 iliosacral screw trajectory unless the screw is significantly malpositioned laterally and superiorly.

Option E (Pudendal nerve) is located more inferiorly and medially in the pelvis and is not typically at direct risk during S1 iliosacral screw placement.

Correct Answer: C

The case content, under 'Surgical Anatomy & Biomechanics' and 'Patterns of Instability,' defines 'Lumbopelvic Dissociation' as 'A severe form of instability involving a complete disruption between the lumbar spine and the pelvis, typically through a transverse sacral fracture (Denis zone III).' Under 'Detailed Surgical Approach / Technique' and 'Sacral Non-union/Malunion,' it states that 'Spino-Pelvic Fixation' is indicated 'For high transverse sacral fractures (Denis zone III) or lumbopelvic dissociation (e.g., U-type, H-type sacral fractures). This involves connecting the lumbar spine (L4/L5) to the ilium... S2 Alar-Iliac (S2AI) screws are utilized. Rods connect the lumbar screws to the iliac/S2AI screws, creating a stable lumbopelvic construct.'

Option A (Anterior plating of the pubic symphysis) is incorrect. This addresses anterior ring instability and would not stabilize a lumbopelvic dissociation.

Option B (Percutaneous iliosacral screw fixation) is typically used for SI joint diastasis or sacral ala fractures, but it is insufficient for the severe instability and complete disruption seen in lumbopelvic dissociation.

Option D (SI joint plating) is used for SI joint disruption but, like iliosacral screws, does not provide the necessary stability to bridge the lumbar spine to the pelvis for lumbopelvic dissociation.

Option E (External fixation) is generally used for acute temporary stabilization or for specific anterior ring injuries, but it is rarely a definitive solution for chronic, severe lumbopelvic dissociation.

Correct Answer: C

The case content, under 'Post-Operative Rehabilitation Protocols' and 'Immediate Post-Operative Phase,' states: 'Stable Fixation (e.g., bicortical plating of symphysis, two well-placed iliosacral screws): Protected weight-bearing (toe-touch or partial WB, typically 25-50% body weight) on the affected side using crutches or a walker.' The patient's fixation (dual plating of symphysis and two iliosacral screws) is described as 'stable fixation and good bone quality,' fitting this description.

Option A (Non-weight bearing (NWB) on both lower extremities) is generally too restrictive for stable fixation and would hinder early mobilization.

Option B (Non-weight bearing (NWB) on the affected side) is indicated for 'Less Stable Fixation (e.g., unilateral fixation, poor bone quality, spino-pelvic fusion for highly unstable injuries),' which is not the case here.

Option D (Full weight-bearing (FWB) as tolerated) is typically reserved for the intermediate rehabilitation phase (8-12 weeks) after radiographic healing is evident, not immediately post-op.

Option E (Continuous bed rest for 6 weeks) is an outdated and harmful protocol, increasing the risk of complications like DVT, pressure ulcers, and muscle atrophy. Early mobilization is a key principle of modern fracture management.

Correct Answer: C

The case content, under 'Complications & Management' and 'Hardware Failure / Loosening,' states: 'Management: Symptomatic hardware failure necessitates revision surgery. Removal of failed hardware, debridement, re-reduction, and re-fixation with stronger constructs, larger diameter screws, or different fixation points. Bone grafting for associated non-unions.' This patient has symptomatic hardware failure (fractured screw) leading to loss of reduction and recurrent instability, making revision surgery the most appropriate course of action.

Option A (Multidisciplinary pain management and continued physical therapy) and Option B (Observation with activity modification and serial radiographs) are conservative approaches that are indicated for asymptomatic malunions or stable residual deformities. They are inappropriate for symptomatic hardware failure with loss of reduction and recurrent instability, as this indicates a mechanical problem requiring surgical correction.

Option D (Hardware removal only, followed by non-weight bearing) is incorrect. Simply removing the failed hardware without addressing the underlying instability and loss of reduction would leave the patient with an unstable pelvis, likely worsening their symptoms and functional outcome. Hardware removal is typically considered only if it is symptomatic and the underlying fracture is completely healed and stable.

Option E (Consideration of amputation in extremis) is an extreme measure reserved for non-reconstructible anatomy in rare, highly comminuted chronic cases, as mentioned under 'Absolute Contraindications.' This is not indicated for a fractured iliosacral screw with loss of SI joint reduction, which is a reconstructible problem.

Correct Answer: C

The case content, under 'Biomechanics of Pelvic Stability' and 'Patterns of Instability,' describes: 'Rotational Instability: Disruption of the anterior ring (pubic symphysis or rami) combined with partial disruption of the posterior ring ligaments (e.g., external rotation injuries like "open book").' The patient's initial injury was an 'open book' type, and current imaging shows 'persistent 2.5 cm pubic symphysis diastasis' (anterior ring disruption) and a 'partially healed sacral ala fracture with some rotational malalignment' (partial posterior ring disruption), without explicit mention of significant vertical displacement, making it primarily a rotational instability.

Option A (Vertical Instability) is incorrect. Vertical instability involves 'Disruption of both anterior and posterior ring structures, including the strong posterior SI ligaments and often a sacral fracture or SI joint dislocation. This is the most severe form.' While there is a sacral fracture, the primary characteristic described is rotational malalignment and symphyseal diastasis, typical of rotational instability, not severe vertical displacement.

Option B (Lumbopelvic Dissociation) is incorrect. This is a severe form of instability involving a complete disruption between the lumbar spine and the pelvis, typically through a transverse sacral fracture (Denis zone III), which is not described here.

Option D (Combined Mechanical Instability (Young & Burgess)) is a classification type, but the question asks what the injury 'primarily represents' in terms of instability pattern. While an 'open book' injury could be classified as APC II or III (Young & Burgess), the underlying mechanical instability is rotational.

Option E (Stable Avulsion Fracture) is incorrect. A 2.5 cm pubic symphysis diastasis and a sacral fracture clearly indicate an unstable injury, not a stable avulsion.

Correct Answer: C

The patient presents with persistent hemodynamic instability despite initial resuscitation and pelvic binder application, strongly suggesting ongoing hemorrhage from the pelvic fracture. The negative FAST exam makes a significant intra-abdominal source less likely. In this scenario, the priority is to control pelvic hemorrhage. Emergent angiography with embolization is indicated for suspected arterial bleeding (often identified by CT angiography, though not yet performed here, persistent instability points to it), while preperitoneal pelvic packing is highly effective for venous bleeding, which accounts for 80-90% of significant pelvic hemorrhage. Both are critical damage control interventions aimed at stabilizing the patient before definitive fixation.

Option A (Immediate definitive internal fixation) is incorrect. Definitive fixation is typically delayed until the patient is hemodynamically stable and physiologically optimized, often following damage control procedures like embolization or packing. Attempting definitive fixation in an unstable patient increases morbidity and mortality.

Option B (Diagnostic peritoneal lavage (DPL)) is incorrect. While DPL can detect intra-abdominal hemorrhage, the negative FAST exam makes it less urgent, and the primary concern is clearly pelvic hemorrhage given the gross pelvic instability and persistent shock. Furthermore, DPL is less commonly used now with the widespread availability of FAST and CT scans.

Option D (Transfer to the operating room for exploratory laparotomy) is incorrect. Exploratory laparotomy is indicated for intra-abdominal hemorrhage, especially if the FAST is positive or there are signs of peritonitis. With a negative FAST and clear signs of pelvic instability, the hemorrhage is most likely retroperitoneal from the pelvis, which is not directly addressed by a standard laparotomy. Preperitoneal packing is a more targeted approach for pelvic hemorrhage.

Option E (Application of a traction table for reduction of vertical displacement) is incorrect. While a traction table can aid in reduction, it is a step towards definitive fixation and does not directly address life-threatening hemorrhage. Hemodynamic stabilization takes precedence over fracture reduction in this emergent setting.

Correct Answer: C

A Young-Burgess Vertical Shear (VS) injury is a high-energy injury resulting from an axial load (e.g., fall from height landing on feet). It is characterized by complete disruption of both the anterior and posterior pelvic rings, leading to significant vertical displacement. This pattern is highly unstable, both rotationally and vertically, and carries a very high morbidity and mortality.

Option A (It is typically managed non-operatively with bed rest and pain control) is incorrect. VS injuries are inherently unstable and always require operative stabilization due to complete disruption of both anterior and posterior rings.

Option B (It is characterized by pubic symphysis diastasis less than 2.5 cm with intact posterior ligaments) is incorrect. This description aligns with a Young-Burgess Anteroposterior Compression Type I (APC I) injury, which is rotationally stable.

Option D (It is a rotationally unstable but vertically stable injury, often referred to as an 'open book' fracture) is incorrect. This describes a Young-Burgess Anteroposterior Compression Type II (APC II) injury. VS injuries are both rotationally and vertically unstable.

Option E (The primary source of hemorrhage is usually arterial, originating from the superior gluteal artery) is incorrect. While arterial bleeding (e.g., from the superior gluteal artery) can occur, the vast majority (80-90%) of significant pelvic hemorrhage, especially in high-energy unstable fractures like VS, is venous in origin, primarily from the presacral venous plexus and internal iliac veins.

Correct Answer: C

The presence of blood at the meatus and gross blood on rectal exam in a male with a pelvic fracture strongly suggests a urethral injury. A retrograde urethrogram (RUG) is the gold standard for evaluating suspected urethral trauma. It involves injecting contrast into the urethra to visualize its integrity and identify any extravasation, strictures, or ruptures.

Option A (CT cystogram) is incorrect. A CT cystogram evaluates the bladder for rupture by filling it with contrast. While bladder injury can coexist with urethral injury, the RUG specifically targets the urethra, which is the primary concern with blood at the meatus.

Option B (Intravenous pyelogram (IVP)) is incorrect. An IVP evaluates the kidneys and ureters for injury by observing the excretion of intravenous contrast. It does not directly visualize the urethra or bladder and is not the appropriate study for suspected urethral trauma.

Option D (MRI of the pelvis) is incorrect. MRI provides excellent soft tissue detail but is not typically the initial or most appropriate study for acute urethral trauma due to its cost, time, and limited availability in the acute trauma setting. It is also less effective than RUG for visualizing urethral integrity.

Option E (Repeat AP pelvis radiograph) is incorrect. A repeat AP pelvis radiograph would provide information about the bony pelvis but not about the integrity of the urethra. The initial radiographs have already classified the fracture.

Correct Answer: C

During percutaneous S1 iliosacral screw placement, the L5 nerve root is at the highest risk of iatrogenic injury. The L5 nerve root exits the sacrum through the L5-S1 foramen, which is located immediately anterior and slightly caudal to the typical entry point and trajectory for an S1 iliosacral screw. If the screw trajectory is too anterior, too caudal, or penetrates the anterior cortex of the sacrum, it can directly impinge upon or injure the L5 nerve root, leading to foot drop or other neurological deficits.

Option A (Femoral nerve) is incorrect. The femoral nerve is located more anteriorly in the thigh and is not typically at risk during posterior iliosacral screw placement.

Option B (Obturator nerve) is incorrect. The obturator nerve passes through the obturator foramen and is not directly in the path of an S1 iliosacral screw.

Option D (Sciatic nerve) is incorrect. The sciatic nerve exits the pelvis via the greater sciatic foramen, which is lateral and inferior to the S1 screw trajectory. While it can be injured in very complex sacral fractures or with extremely aberrant screw placement, the L5 nerve root is more directly vulnerable with standard S1 screw placement.

Option E (Pudendal nerve) is incorrect. The pudendal nerve exits the pelvis through the greater sciatic foramen, curves around the ischial spine, and re-enters through the lesser sciatic foramen. It is not typically at risk during S1 iliosacral screw placement.

Correct Answer: C

A Young-Burgess APC I injury (pubic symphysis diastasis < 2.5 cm, intact posterior ligaments) is considered rotationally stable. Isolated, minimally displaced pubic rami fractures, especially in a hemodynamically stable patient without associated injuries, are typically managed non-operatively. The focus is on pain control, early mobilization (weight-bearing as tolerated), and physical therapy to prevent complications like DVT and pneumonia, and to restore function.

Option A (Emergent external fixation of the pelvis) is incorrect. External fixation is reserved for hemodynamically unstable patients or mechanically unstable fractures (e.g., APC II/III, VS) to provide temporary stability and aid in hemorrhage control. It is not indicated for stable APC I injuries.

Option B (Percutaneous iliosacral screw fixation) is incorrect. Iliosacral screw fixation addresses posterior pelvic ring instability (e.g., SI joint disruption, sacral fractures). An APC I injury has an intact posterior ring, so this intervention is not necessary.

Option D (Open reduction and internal fixation of the pubic rami) is incorrect. ORIF of isolated pubic rami fractures is rarely indicated, especially if they are minimally displaced and stable. Non-operative management is the standard.

Option E (Preperitoneal pelvic packing) is incorrect. Preperitoneal packing is a damage control procedure for life-threatening pelvic hemorrhage in hemodynamically unstable patients. It is not indicated for a stable, minimally displaced fracture in a hemodynamically stable patient.

Correct Answer: C

The CT scan identifying an 'active arterial blush' from a branch of the internal iliac artery is a direct indication for emergent angiography and embolization. Angiography allows for precise localization of the bleeding vessel, and embolization can effectively occlude the arterial source, which is crucial for controlling arterial hemorrhage. While other interventions may be part of the overall management, angiography and embolization specifically target the identified arterial bleed.

Option A (Immediate preperitoneal pelvic packing) is incorrect as the primary, most effective intervention for an identified arterial blush. While packing is effective for venous bleeding and can be used in conjunction with embolization or if embolization fails, it is not the most specific or primary treatment for an identified arterial source.

Option B (External fixation of the pelvis) is incorrect as the primary, most effective intervention for an identified arterial blush. External fixation provides mechanical stability and helps tamponade venous bleeding by reducing pelvic volume, but it does not directly control an active arterial extravasation.

Option D (Damage control laparotomy) is incorrect. A standard laparotomy primarily addresses intra-abdominal injuries. While preperitoneal packing can be performed via a suprapubic incision, a full laparotomy is not the most targeted approach for retroperitoneal arterial bleeding from a pelvic fracture, especially when angiography is available and indicated.

Option E (Application of a second pelvic binder) is incorrect. A single, properly applied pelvic binder is sufficient for external compression. Applying a second binder is unlikely to provide additional benefit and may cause skin complications.

Correct Answer: C

The image provided is an Outlet view of the pelvis. This view is characterized by the projection of the pubic symphysis over the sacrum, allowing for clear visualization of the vertical alignment of the hemipelvis. It is primarily used to assess for superior or inferior vertical migration (displacement) of the hemipelvis and to evaluate the sacral lordosis or angulation.

Option A (AP Pelvis view) is incorrect. An AP pelvis view shows the entire pelvic ring, symphysis, and SI joints without significant superimposition, but it is not the view shown. It is the initial mandatory view.

Option B (Inlet view) is incorrect. An inlet view projects the posterior structures (sacrum, SI joints) without superimposition, useful for assessing sacral kyphosis/angulation and anterior-posterior displacement of the posterior ring. The image does not show the characteristic appearance of an inlet view where the pelvic brim is clearly visualized.

Option D (Judet view (Obturator Oblique)) is incorrect. Judet views are specific for acetabular fractures. The obturator oblique view visualizes the anterior column and posterior wall of the acetabulum. The image is a pelvic ring view, not an acetabular view.

Option E (Judet view (Iliac Oblique)) is incorrect. The iliac oblique view visualizes the posterior column and anterior wall of the acetabulum. Again, the image is a pelvic ring view.

Correct Answer: C

The case study explicitly states: 'The "golden window" for definitive fixation is generally considered within 5-7 days.' This timing allows for initial resuscitation, stabilization of associated injuries, and optimization of the patient's physiological status, while still providing the benefits of early definitive stabilization, such as reduced complication rates and improved outcomes compared to prolonged external fixation.

Option A (Within 12 hours of injury) is incorrect. While emergent interventions for hemorrhage control (e.g., external fixation, embolization, packing) may occur within hours, definitive internal fixation is typically not performed this early unless the patient is fully stable and there are no other pressing issues. The focus in the immediate hours is on damage control.

Option B (Within 24-48 hours of injury) is incorrect. While some urgent fixations may occur in this timeframe, the 'golden window' is generally considered slightly longer to allow for full physiological optimization, especially in polytrauma patients or those with comorbidities.

Option D (After 2-3 weeks, once soft tissue swelling has resolved) is incorrect. Delaying definitive fixation beyond the 'golden window' can lead to increased difficulty in reduction, higher rates of malunion, and potentially increased morbidity, especially for unstable fractures.

Option E (Only if non-operative management fails after 6 weeks) is incorrect. A Tile Type B1 (APC II) fracture with 3.5 cm symphysis diastasis is rotationally unstable and requires operative stabilization. Non-operative management is not appropriate for this degree of instability, and waiting 6 weeks would lead to malunion and poor outcomes.

Correct Answer: C

A Young-Burgess Anteroposterior Compression Type II (APC II) injury is characterized by pubic symphysis diastasis greater than 2.5 cm and disruption of the anterior sacroiliac ligaments, but with intact posterior sacroiliac ligaments. This pattern makes the pelvic ring rotationally unstable (often described as an 'open book' injury) but vertically stable because the strong posterior ligaments remain intact, preventing vertical displacement.

Option A (Rotationally and vertically unstable) is incorrect. This describes an APC III or Vertical Shear (VS) injury, where both anterior and posterior ligamentous complexes are disrupted.

Option B (Rotationally stable and vertically stable) is incorrect. This describes an APC I or LC I injury, which are considered stable pelvic fractures.

Option D (Vertically unstable but rotationally stable) is incorrect. This combination is not typical for a primary pelvic ring injury pattern. Vertical instability almost always implies rotational instability due to posterior ring disruption.

Option E (Stable to all forces due to intact posterior arch) is incorrect. While the posterior arch (posterior SI ligaments) is intact, the anterior disruption (symphysis diastasis > 2.5 cm and anterior SI ligament disruption) makes the pelvis rotationally unstable.

Correct Answer: B

The case study explicitly states that percutaneous iliosacral screw placement is performed under fluoroscopic guidance using 'inlet, outlet, lateral sacral views, +/- Judet views for SI joint'. These three views (inlet, outlet, and lateral sacral) are crucial for confirming the correct trajectory of the guide wire and screw, ensuring it remains within the safe corridor of the sacral ala and body, avoiding the sacral foramina and neurovascular structures. The inlet view assesses anterior-posterior displacement and sacral kyphosis, the outlet view assesses vertical displacement and sacral lordosis, and the lateral sacral view confirms the depth and trajectory within the sacral body.

Option A (AP pelvis and lateral hip views) is incorrect. While an AP pelvis is a standard initial view, a lateral hip view is not specific for iliosacral screw placement. The image provided is an outlet view, which is one of the critical views.

Option C (Judet views (iliac oblique and obturator oblique)) is incorrect. Judet views are primarily used for acetabular fractures and are not the primary views for iliosacral screw placement, although they can be helpful for assessing the SI joint itself.

Option D (Frog-leg lateral and cross-table lateral views) is incorrect. These are typically hip views and are not used for iliosacral screw placement.

Option E (CT scan with 3D reconstruction only) is incorrect. While a pre-operative CT scan with 3D reconstruction is invaluable for planning, intra-operative fluoroscopy is essential for real-time guidance during screw insertion. Relying solely on a pre-operative CT without intra-operative imaging is unsafe.

Correct Answer: D

The patient's symptoms of severe pain, swelling, tenderness, neurological deficits (sciatic nerve distribution), and elevated intracompartmental pressures in the gluteal region are classic signs of compartment syndrome. While rare in the gluteal compartment, it can occur after high-energy pelvic trauma, especially with high-volume fluid resuscitation and prolonged immobilization. Urgent fasciotomy is indicated for this life-threatening condition.

Option A (Deep venous thrombosis (DVT)) is incorrect. While DVT is a common complication of pelvic fractures, its symptoms typically include leg swelling, pain, and tenderness, but not elevated intracompartmental pressures or acute neurological deficits in the sciatic nerve distribution.

Option B (Heterotopic ossification (HO)) is incorrect. HO is a late complication involving ectopic bone formation in soft tissues, usually presenting weeks to months after injury with stiffness and pain, not acute compartment syndrome.

Option C (Pin site infection) is incorrect. Pin site infections are associated with external fixation and present with localized redness, warmth, drainage, and pain around the pins, not diffuse gluteal swelling, neurological deficits, and elevated intracompartmental pressures.

Option E (Malunion) is incorrect. Malunion is a late complication where the fracture heals in an unacceptable position, leading to chronic pain and dysfunction, not an acute post-operative emergency like compartment syndrome.

Anteroposterior compression (APC) injuries typically cause tearing of the anterior branches of the internal iliac artery system, most notably the internal pudendal and obturator arteries. In contrast, lateral compression injuries are more frequently associated with bleeding from posterior branches like the superior gluteal artery.

Denis Zone III sacral fractures involve the central sacral canal and have the highest rate of neurologic injury (up to 57%). These injuries frequently disrupt the sacral nerve roots governing sphincter control, leading to bowel, bladder, and sexual dysfunction.

The patient has a Morel-Lavallée lesion, a closed degloving injury separating the subcutaneous tissue from the underlying fascia. Surgical incisions made directly through this compromised, necrotic tissue carry a notoriously high risk of deep postoperative infection.

Pelvic binders must be centered over the greater trochanters to effectively compress the pubic symphysis and reduce the pelvic volume. Placement higher up over the iliac crests is ineffective and can actually cause paradoxical widening of the true pelvis.

The findings describe a dysmorphic sacrum, which features an acute alar slope, residual S1/S2 disc space, and articulating L5 transverse processes. The 'safe zone' for S1 iliosacral screws in a dysmorphic sacrum is dramatically reduced and obliquely oriented, significantly increasing the risk of extraosseous screw placement.

A U-shaped sacral fracture represents spinopelvic dissociation, meaning the axial skeleton is disconnected from the pelvic ring. Bilateral lumbopelvic fixation is the construct of choice to bridge the dissociation, stabilize the spine to the pelvis, and permit early mobilization.

The pelvic outlet view (directed 45 degrees cephalad) projects the sacrum en face and is the optimal view for assessing vertical displacement (cranial/caudal translation) of a hemipelvis.

Blood at the urethral meatus and a high-riding prostate are classic signs of a posterior urethral injury. A retrograde urethrogram (RUG) must be performed prior to any catheter insertion to avoid converting a partial urethral tear into a complete transection.

The corona mortis is a critical vascular anastomosis connecting the external iliac system (usually inferior epigastric) to the internal iliac system (usually the obturator artery or vein). It courses over the superior pubic ramus and is highly vulnerable during anterior pelvic approaches.

Current guidelines emphasize that patients with major pelvic fractures are at exceptionally high risk for VTE. Pharmacologic prophylaxis (e.g., LMWH) should be initiated within 24 hours of surgical stabilization, provided there is no active bleeding or coagulopathy.

On the pelvic inlet view, the anterior boundary of the safe zone is defined by the anterior cortex of the S1 sacral body. Violating this boundary anteriorly risks devastating injury to the internal iliac vessels and the L5 nerve root.

Sexual dysfunction, including dyspareunia in females and erectile dysfunction in males, is a very common complication following major anterior pelvic ring disruptions. It is typically attributed to local nerve injury (pudendal nerve branches), soft-tissue scarring, and pelvic floor dysfunction rather than hardware complications.

While LC-I fragility fractures are minimally displaced, intractable pain preventing mobilization carries significant morbidity and mortality in the elderly. Minimally invasive posterior fixation (e.g., percutaneous IS screws) provides stability, significantly relieves pain, and allows for early mobilization.

A crescent fracture involves a fracture of the posterior iliac wing extending into the sacroiliac joint, leaving the posterior sacroiliac ligaments intact. This is the hallmark posterior lesion of a Lateral Compression Type II (LC-II) injury.

Destot's sign is characterized by a superficial hematoma above the inguinal ligament, within the scrotum, or in the proximal thigh. It indicates retroperitoneal bleeding that has tracked along fascial planes, strongly suggesting a major pelvic fracture.

The posterior sacroiliac complex, specifically the interosseous sacroiliac ligament, is the strongest ligament in the body and serves as the primary static stabilizer of the pelvic ring, primarily resisting vertical shear and distraction forces.

Open pelvic fractures complicated by fecal contamination and sphincter injury carry a massive risk for overwhelming pelvic sepsis. Immediate mechanical bowel diversion via a colostomy is mandatory, in addition to aggressive debridement and pelvic stabilization.

An LC-III or 'windswept' pelvis occurs when a severe lateral compression force continues across the pelvic ring, causing an internal rotation injury on the impacted side and an external rotation (open book) injury on the contralateral side.

APC-II injuries involve disruption of the symphysis, anterior sacroiliac ligaments, and the sacrotuberous/sacrospinous ligaments, but the strong posterior sacroiliac ligaments remain intact. APC-III injuries involve complete disruption of both anterior and posterior sacroiliac complexes, causing complete spinopelvic instability.

Pelvic binders should be placed centered over the greater trochanters to effectively close the pelvic ring and reduce volume. Placement over the iliac crests or ASIS is less effective and may paradoxically open the pelvic ring or cause localized pressure necrosis.

The pelvic inlet view is obtained by angling the x-ray beam 45 degrees caudad (from the head towards the feet). This view optimally evaluates anterior or posterior translation of the hemipelvis and internal/external rotational deformities.

The corona mortis ('crown of death') is a common vascular anastomosis connecting the external iliac system (usually the inferior epigastric artery/vein) with the internal iliac system (obturator artery/vein). It is located on the posterior aspect of the superior pubic ramus and is highly susceptible to iatrogenic injury.

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST exam (indicating no major intra-abdominal hemorrhage), the pelvic bleeding must be addressed. Pelvic angiography with embolization (or preperitoneal pelvic packing) is the standard of care for retroperitoneal hemorrhage.

Dysmorphic sacrums feature an upper sacral segment located above the iliac crests, non-circular (teardrop) upper sacral foramina, a residual S1-S2 disc space, and an acute alar slope. These morphological variants severely restrict the safe zone for S1 iliosacral screws.

The L5 nerve root courses directly anterior to the sacral ala. A drill or screw breaching the anterior cortex of the upper sacrum in this region places the L5 nerve root at high risk for iatrogenic injury.

An anterior sacral ala impaction fracture combined with transverse or oblique pubic rami fractures is characteristic of a Lateral Compression Type 1 (LC-1) injury. This is a rotationally unstable but vertically stable injury pattern.

In the setting of a posterior urethral disruption associated with a pelvic ring injury, placement of a suprapubic catheter is the standard initial management. Transurethral catheterization is contraindicated as it may convert a partial tear into a complete tear.

A Morel-Lavallée lesion is a closed internal degloving injury where skin and subcutaneous tissue are sheared from the underlying fascia, leading to a hemolymphatic fluid collection. If not adequately decompressed/debrided before internal fixation, it carries a very high risk of deep bacterial infection.

Denis Zone 3 involves the central sacral canal. Fractures in this zone have the highest rate of neurologic injury (over 50%), specifically involving the sacral nerve roots (S2-S4), which classically present with sphincter paralysis and bowel/bladder dysfunction.

The Young-Burgess LC-2 pattern is characterized by a lateral compression force that causes an anterior pubic rami fracture and an ipsilateral posterior iliac wing fracture extending into the sacroiliac joint, known as a 'crescent' fracture.

The most common nerve complication associated with the INFIX procedure is irritation or injury to the lateral femoral cutaneous nerve (LFCN) due to the subcutaneous placement of the connecting rod and supra-acetabular screws.

The vast majority (80-90%) of bleeding in pelvic fractures is venous in origin. The highly vascular cancellous bone and the extensive presacral venous plexus are the most common sources of hemorrhage.

A U-shaped or H-shaped sacral fracture represents a spinopelvic dissociation, disconnecting the axial spine from the pelvis. It requires extremely rigid stabilization to withstand vertical shear forces, best achieved through lumbopelvic fixation (spanning from the lower lumbar pedicles to the ilium).

Patients with pelvic ring injuries are at a very high risk for DVT/PE. Current guidelines recommend initiating chemical prophylaxis (typically LMWH) within 24 to 48 hours of injury, provided bleeding is controlled, and continuing it throughout the perioperative period.

If an APC-III injury (which has complete anterior and posterior instability) is treated with isolated anterior plate fixation without stabilizing the posterior ring, the anterior hardware will bear excessive stress, most commonly leading to screw pull-out or hardware failure.

The Day classification describes the amount of ilium remaining attached to the sacrum. Type 1 enters the anterior aspect of the SI joint (leaving a large crescent attached to the sacrum). Type 2 enters the middle aspect, and Type 3 enters the posterior aspect (leaving a small crescent attached).

Open pelvic fractures with massive perineal soft tissue injury and rectal involvement carry an exceptionally high risk of overwhelming sepsis. A diverting colostomy is critical to prevent ongoing fecal contamination of the open fracture hematoma.

The pelvic outlet view (angled 45 degrees cephalad) projects the sacrum in its true en face orientation. It is the most accurate radiographic view for evaluating superior-inferior (vertical) displacement of the hemipelvis and sacral foraminal asymmetry.

Pelvic binders should be placed centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is incorrect and can paradoxically widen the true pelvis.

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST scan, the source of bleeding is likely retroperitoneal. The standard of care is immediate hemorrhage control via pelvic angiography with embolization or pre-peritoneal pelvic packing.

The corona mortis is a vascular anastomosis between the obturator and external iliac systems (or inferior epigastric vessels) located over the superior pubic ramus. It is at high risk of iatrogenic injury during anterior intrapelvic approaches.

The L5 nerve root is highly susceptible to traction injury during vertical shear injuries as it drapes over the sacral ala. Cephalad displacement of the hemipelvis places significant tension on this nerve.

The pelvic inlet view best demonstrates anterior-posterior translation of the pelvic ring. It is essential for verifying reduction of the sacroiliac joint and confirming the screw does not violate the anterior sacral cortex.

The bulbomembranous junction is the most frequent site of posterior urethral injury in males with severe anterior pelvic ring disruptions. The firm attachment of the membranous urethra to the pubic bone causes shearing forces during diastasis.

Radiographic signs of sacral dysmorphism include an acute (steep) alar slope, residual intervertebral discs, non-circular neural foramina, an elevated upper sacrum, and the presence of mammillary bodies.

An LC-2 injury is defined by an anterior ring fracture combined with a posterior crescent fracture of the ilium. The LC-1 involves a sacral compression fracture.

A Denis Zone 3 sacral fracture involves the central sacral canal. It carries the highest risk (up to 50%) of neurologic injury, particularly bowel, bladder, and sexual dysfunction due to injury to the sacral nerve roots.

This presentation describes a Morel-Lavallée lesion, a closed degloving injury. It results from severe shearing forces that separate the subcutaneous fat from the underlying investing fascia, creating a potential space that fills with blood and lymph.

In a completely unstable pelvic ring injury (APC-III), isolated anterior fixation is biomechanically insufficient. Failure to adequately address and fix the posterior pelvic ring instability is the leading cause of anterior hardware failure.

Current trauma guidelines recommend initiating pharmacologic DVT prophylaxis (e.g., LMWH) 24 to 48 hours after injury or surgery in pelvic trauma patients, provided there are no active bleeding issues or other contraindications.

Prolonged application of a pelvic binder (especially > 24 hours) strongly increases the risk of skin necrosis and pressure ulcerations, most commonly over the greater trochanters. Binders should be removed or converted to definitive fixation as soon as hemodynamically feasible.

The lateral femoral cutaneous nerve (LFCN) is highly susceptible to compression or traction injury from the INFIX bar or pedicle screws, leading to meralgia paresthetica. Proper implant positioning is critical to minimize this risk.

In the Tile classification, Type A injuries are stable, Type B are rotationally unstable but vertically stable, and Type C injuries are both rotationally and vertically unstable due to complete disruption of the posterior pelvic floor.

The interosseous sacroiliac ligament is the strongest ligament in the body and acts as the primary stabilizer against both vertical shear and anterior-posterior translational forces at the SI joint.

On an outlet view, the superior border of the sacral ala (alar slope) forms the "roof" of the safe zone. A screw placed above this line will exit the sacrum superiorly, endangering the L5 nerve root.

Open pelvic fractures with perineal or rectal involvement carry a very high risk of fatal sepsis. Aggressive wound debridement combined with a diverting colostomy is essential to minimize fecal contamination and reduce mortality.

APC-III injuries (open book pelvis) result in a massive increase in pelvic volume, allowing for unchecked retroperitoneal hemorrhage. They are associated with the highest rates of massive transfusion and overall mortality compared to other patterns.

While a single iliosacral screw adequately resists vertical and anterior-posterior translation, a second screw provides significantly increased resistance to rotational forces, which is essential in highly unstable injuries.

Approximately 80% of pelvic hemorrhage following trauma originates from the presacral venous plexus and fractured cancellous bone surfaces. Arterial bleeding accounts for a smaller percentage but may require arterial embolization.