ABOS Part I & AAOS OITE Orthopaedic Review: Cervical Spine Trauma & Proximal Humerus Fractures | Part 21580

Correct Answer: C

Bilateral cervical facet dislocations are severe, high-energy injuries typically resulting from a combination of hyperflexion and distraction forces. This mechanism leads to complete, catastrophic disruption of the posterior ligamentous complex (PLC), which includes the ligamentum flavum, interspinous ligaments, supraspinous ligaments, and facet joint capsules. The posterior longitudinal ligament (PLL) and the intervertebral disc annulus are also frequently compromised. This aligns with Stage 3 or Stage 4 of the Allen and Ferguson mechanistic classification for Distraction-Flexion injuries.

Option A describes the typical mechanism for a unilateral facet dislocation, which involves flexion-rotation and generally less severe ligamentous disruption. Option B describes a hyperextension injury, which primarily affects the anterior column and ligaments. Option D describes a burst fracture, which is an axial compression injury. Option E describes a shear injury, which is less common for isolated bilateral facet dislocations.

Correct Answer: E

The Posterior Ligamentous Complex (PLC) is the primary tension band of the cervical spine, comprising the ligamentum flavum, interspinous ligaments, supraspinous ligaments, and the facet joint capsules. In bilateral cervical facet dislocation, the severe hyperflexion and distraction forces cause complete, catastrophic disruption of the PLC. While the Anterior Longitudinal Ligament (ALL), Posterior Longitudinal Ligament (PLL), and Intervertebral Disc Annulus Fibrosus are also frequently compromised (often stripped or torn), the complete failure of the PLC is the hallmark of this injury, leading to the profound instability and anterior translation of the superior vertebral body. The Ligamentum Flavum (C) is a component of the PLC, but the entire complex's disruption is the most critical factor.

Correct Answer: C

The timing of magnetic resonance imaging (MRI) in relation to closed reduction is critical. For awake, alert, and cooperative patients, rapid closed reduction via cranial traction can be attempted prior to MRI, provided serial neurological examinations are performed. However, if the patient is uncooperative, intoxicated, or comatose (as in this intubated and sedated patient with an ASIA A injury), MRI must be obtained prior to any reduction attempt. This is to evaluate for a traumatic disc herniation, which occurs in 30-60% of cases. If a massive disc herniation is present, an anterior cervical discectomy must be performed before reduction to prevent catastrophic cord compression from retropulsed disc material.

Option A is incorrect because attempting closed reduction in an obtunded patient without prior MRI carries a high risk of iatrogenic neurological deterioration. Option B is incorrect as further imaging is crucial for surgical planning and safety. Option D (CTA) is important if there's suspicion of vertebral artery injury, but MRI for disc herniation takes precedence before reduction in this scenario. Option E (methylprednisolone) is no longer routinely recommended for acute spinal cord injury due to lack of clear benefit and potential side effects.

Correct Answer: B

The standard Smith-Robinson anterior cervical approach utilizes an internervous plane to access the cervical spine. This plane is developed between the sternocleidomastoid muscle and the carotid sheath (containing the common carotid artery, internal jugular vein, and vagus nerve) laterally, and the strap muscles (sternohyoid, sternothyroid, omohyoid), trachea, and esophagus medially. This approach minimizes muscle transection and allows for safe access to the prevertebral fascia and anterior cervical spine.

Option A describes a deeper plane after the prevertebral fascia is exposed. Option C describes the initial incision through superficial layers. Options D and E describe structures within or adjacent to the vertebral column, not the primary internervous plane for the approach.

Correct Answer: B

The Magerl technique for lateral mass screw placement is a widely accepted method designed to maximize screw purchase while minimizing the risk of neurovascular injury. The starting point is typically 1 millimeter medial and 1 millimeter cephalad to the center of the lateral mass. The trajectory is 25 degrees lateral (to avoid the vertebral artery, which lies anterior and medial to the lateral mass) and parallel to the superior articular facet in the sagittal plane (typically 20 to 30 degrees cephalad, avoiding the exiting nerve root). This trajectory aims to engage the thickest part of the lateral mass.

Option A describes the Roy-Camille technique, which uses a central starting point and a straight anterior trajectory. The other options describe incorrect starting points or trajectories that would increase the risk of vertebral artery or nerve root injury.

Correct Answer: C

Hoarseness is a classic symptom of recurrent laryngeal nerve (RLN) palsy, which can occur during an anterior cervical approach due to retraction or direct injury to the nerve. Dysphagia (difficulty swallowing) is also a common complication, often transient, resulting from esophageal retraction and irritation during the anterior approach. Both complications are relatively common (RLN palsy 1-5%, dysphagia 10-30%) and are usually transient, resolving spontaneously within weeks to months. Management is typically conservative, involving speech therapy evaluation for dysphagia and vocal cord assessment for hoarseness. Severe or persistent cases may require further intervention.

Option A (C5 nerve root palsy) presents as deltoid and biceps weakness, not hoarseness or dysphagia. Option B (vertebral artery injury) would present with signs of posterior circulation stroke or significant hemorrhage. Option D (epidural hematoma) would typically cause acute neurological deterioration, not isolated hoarseness and dysphagia. Option E (hardware failure) is a long-term mechanical complication, not an acute postoperative neurological or soft tissue issue.

Correct Answer: B

Current guidelines for the management of acute spinal cord injury (SCI) emphasize maintaining adequate spinal cord perfusion to minimize the penumbra of ischemic secondary injury. This is achieved by maintaining the Mean Arterial Pressure (MAP) greater than 85 mmHg for at least 7 days post-injury. This hemodynamic target helps ensure sufficient blood flow to the injured spinal cord, which is particularly vulnerable to ischemia.

Option A is incorrect; maintaining a low SBP would compromise spinal cord perfusion. Option C is incorrect; heart rate is not the primary hemodynamic target for SCI. Option D is incorrect; fluid restriction could lead to hypovolemia and compromise MAP. Option E is incorrect; DVT prophylaxis should be initiated within 72 hours of surgery, provided there is no evidence of expanding epidural hematoma, to prevent thromboembolic complications, which are common in SCI patients.

Correct Answer: C

The Subaxial Cervical Spine Injury Severity (SLIC) score is a validated algorithm for surgical decision-making. For a bilateral facet dislocation, the score components are:

• Injury Morphology: Bilateral facet dislocation is considered a translational/rotational injury, scoring 3 points.
• Discoligamentous Complex Integrity: Complete disruption of the posterior ligamentous complex scores 2 points.
• Neurological Status: An ASIA D incomplete spinal cord injury scores 3 points.

Therefore, the total SLIC score for this patient is 3 (morphology) + 2 (PLC) + 3 (neurological status) = 8 points. A SLIC score of 5 or greater mandates surgical intervention. Thus, a score of 8 points strongly mandates surgical stabilization.

Correct Answer: C

Bilateral cervical facet dislocation is characterized by profound instability due to complete disruption of the posterior ligamentous complex. Radiographically, this manifests as significant anterior translation of the superior vertebral body on the inferior one, often exceeding 50% of the vertebral body width on lateral radiography. The inferior articular processes of the superior vertebra translate anteriorly and superiorly over the superior articular processes of the inferior vertebra, ultimately dropping into the intervertebral foramina, creating a locked configuration.

Option A describes less severe instability. Option B describes a purely ligamentous injury without facet dislocation. Option D describes a flexion teardrop fracture, which is a different injury pattern. Option E describes a stable injury, which is not characteristic of a bilateral facet dislocation.

Correct Answer: D

The Surgical Timing in Acute Spinal Cord Injury Study (STASCIS) was a pivotal prospective, multicenter cohort study that demonstrated the significant benefit of early surgical decompression (within 24 hours of injury) in patients with acute spinal cord injury. The study found that early intervention resulted in significantly improved neurological outcomes at 6-month follow-up compared to delayed decompression, without an increase in complication rates. This study fundamentally shifted the paradigm towards emergent surgical intervention for spinal cord injuries, including those associated with bilateral facet dislocations.

Option A (Panjabi and White) provided foundational biomechanical understanding of spinal instability. Option B (Allen and Ferguson) developed a mechanistic classification system for cervical spine injuries. Option C (SLIC score) provides a validated algorithm for surgical decision-making. While all these are important contributions to spine trauma, STASCIS specifically addressed the timing of surgery for SCI.

Correct Answer: D

The patient presents with a displaced surgical neck fracture, but the description notes it is 'valgus-impacted' with 'less than 1 cm displacement and approximately 30 degrees of angulation.' According to the case content, non-operative management is the treatment of choice for the majority of proximal humerus fractures, particularly one-part fractures, and often for two-part surgical neck fractures in elderly, low-demand patients with minimal displacement. Minimally displaced or nondisplaced fractures are generally defined as <1 cm displacement and <45 degrees angulation. Stable, valgus-impacted fractures also fall under non-operative indications. While she has moderate functional demands, her age, osteoporosis, and the relatively stable, minimally displaced nature of the valgus-impacted fracture make non-operative management a strong initial consideration, especially given the PROXIMAL trial's findings suggesting comparable outcomes for many displaced fractures in older populations.

• Option A (ORIF with a locking plate): While ORIF is indicated for significantly displaced two-part surgical neck fractures, this patient's fracture is described as minimally displaced and valgus-impacted, which are features favoring non-operative care. The PROXIMAL trial specifically questioned the superiority of ORIF over non-operative treatment for many displaced fractures in older adults.
• Option B (Hemiarthroplasty): Hemiarthroplasty is typically reserved for highly comminuted four-part fractures, head-splitting fractures, or severe osteopenia preventing stable fixation, especially in older patients. This is a two-part surgical neck fracture, not a complex four-part or head-splitting injury.
• Option C (Reverse total shoulder arthroplasty): RTSA is increasingly favored for complex four-part fractures in elderly patients, particularly with a compromised or irreparable rotator cuff, or severe osteopenia. It is an overtreatment for a minimally displaced two-part surgical neck fracture.
• Option E (Urgent closed reduction and percutaneous pinning): While percutaneous pinning can be used for some two-part fractures, the description of 'valgus-impacted' and 'minimally displaced' suggests inherent stability that may not require surgical reduction and pinning, especially as an urgent initial step over non-operative assessment.

Correct Answer: B

The case content explicitly states: 'The blood supply to the humeral head is predominantly from the ascending branch of the anterior circumflex humeral artery, forming the arcuate artery, which penetrates the head near the bicipital groove. The posterior circumflex humeral artery also contributes. Disruption of these vessels, particularly in multi-part fractures with significant displacement, is a major risk factor for AVN.'

• Option A (Posterior circumflex humeral artery): While the posterior circumflex humeral artery does contribute to the humeral head's blood supply, the anterior circumflex humeral artery and its ascending branch are described as the 'predominant' supply.
• Option C (Thoracoacromial artery): The thoracoacromial artery supplies the pectoralis major, deltoid, and clavicle, but not directly the humeral head.
• Option D (Suprascapular artery): The suprascapular artery supplies the supraspinatus and infraspinatus muscles and the shoulder joint, but is not the primary supply to the humeral head itself.
• Option E (Subscapular artery): The subscapular artery is a branch of the axillary artery that supplies the subscapularis, latissimus dorsi, and teres major muscles, but not the humeral head's primary vascularity.

Correct Answer: D

The case content states: 'Axillary Nerve: Most commonly injured nerve in PHFs or during surgical approaches. It wraps around the surgical neck, approximately 5-7 cm distal to the acromion, innervating the deltoid and teres minor.' The symptoms described—difficulty initiating abduction (deltoid weakness) and sensory loss over the lateral aspect of the deltoid (axillary nerve sensory distribution)—are classic signs of axillary nerve injury.

• Option A (Musculocutaneous nerve): This nerve supplies the biceps and brachialis, responsible for elbow flexion and forearm supination. Injury would present with weakness in these movements and sensory loss over the lateral forearm.
• Option B (Radial nerve): The radial nerve is located more distally and posteriorly in the spiral groove. It innervates the triceps and wrist/finger extensors. Injury would cause wrist drop and sensory loss over the posterior forearm and hand.
• Option C (Ulnar nerve): The ulnar nerve primarily innervates intrinsic hand muscles and flexor carpi ulnaris. Injury would result in claw hand deformity and sensory loss over the medial hand.
• Option E (Median nerve): The median nerve innervates forearm flexors and thenar muscles. Injury would cause 'ape hand' deformity and sensory loss over the radial aspect of the palm and fingers.

Correct Answer: C

The case content explicitly highlights the importance of the medial calcar under the 'Biomechanics' section: 'Medial Calcar: This dense trabecular bone region acts as a crucial weight-bearing structure, resisting varus collapse and providing critical support for internal fixation. Loss of medial calcar support significantly increases the risk of screw cutout and construct failure.' It is also mentioned under 'Complications' that 'inadequate medial support (calcar screws)' is a risk factor for screw cutout.

• Option A (To prevent impingement of the rotator cuff tendons): While proper plate positioning is important to prevent impingement, the medial calcar's primary role is not impingement prevention but structural support.
• Option B (To ensure adequate blood supply to the humeral head and prevent avascular necrosis): The integrity of the medial calcar metaphyseal extension and its periosteal attachments is vital for vascularity, but the primary biomechanical reason for supporting the calcar is to resist varus collapse, not directly to ensure blood supply. The main blood supply is from the anterior circumflex humeral artery.
• Option D (To facilitate early active range of motion and reduce post-operative stiffness): While stable fixation generally allows for earlier rehabilitation, the direct biomechanical role of the medial calcar is not to facilitate early ROM but to provide structural stability to the construct.
• Option E (To protect the axillary nerve from iatrogenic injury during screw placement): The axillary nerve is at risk during lateral plate placement and screw insertion, but the medial calcar's role is not nerve protection.

Correct Answer: E

The case content, particularly the 'Summary of Key Literature / Guidelines' section, strongly supports RTSA in this scenario: 'Reverse Total Shoulder Arthroplasty (RTSA) has gained significant traction, especially in elderly patients with complex PHFs, pre-existing rotator cuff dysfunction, or severe osteopenia. Multiple studies demonstrate more predictable pain relief and functional outcomes with RTSA compared to hemiarthroplasty or ORIF in this specific demographic, as it bypasses the need for tuberosity healing and relies on the deltoid for elevation.' This patient fits all these criteria: elderly, complex four-part fracture, severe osteopenia, and pre-existing rotator cuff tear.

• Option A (ORIF with a locking plate and suture augmentation): While LPO is the gold standard for many complex PHFs, severe osteopenia and a pre-existing rotator cuff tear significantly increase the risk of fixation failure (screw cutout, nonunion of tuberosities) and poor functional outcomes, as the rotator cuff is essential for ORIF success.
• Option B (Hemiarthroplasty with tuberosity repair): Hemiarthroplasty has historically been an option for complex four-part fractures in older patients. However, outcomes can be variable and are often limited by tuberosity healing and rotator cuff function. Given the pre-existing rotator cuff tear, tuberosity healing and function would be severely compromised, making RTSA a superior choice.
• Option C (Non-operative management with sling immobilization): For a complex, comminuted four-part fracture with significant displacement in an active patient, non-operative management would likely lead to severe malunion, pain, and very poor function.
• Option D (Intramedullary nailing): Intramedullary nailing is less common for complex PHFs and is typically used for select two-part surgical neck fractures. It would be inadequate for a comminuted four-part fracture, especially with tuberosity involvement and osteopenia.

Correct Answer: C

The case content describes the deltopectoral approach: 'Identify the cephalic vein running in the deltopectoral groove. This is the key internervous plane. The deltoid muscle is lateral (innervated by the axillary nerve), and the pectoralis major muscle is medial (innervated by the medial and lateral pectoral nerves). The cephalic vein is typically retracted laterally with the deltoid, but can be ligated and divided if necessary for better exposure...'

• Option A: While the vein can be ligated, it's typically retracted first. More importantly, it does not lie between the pectoralis minor and coracobrachialis.
• Option B: The cephalic vein is typically retracted laterally with the deltoid, not medially with the pectoralis major. The internervous plane description is correct, but the retraction direction is wrong.
• Option D: The cephalic vein is retracted laterally with the deltoid, but the plane is between the deltoid and pectoralis major, not deltoid and teres major.
• Option E: While the vein can be ligated, it lies in the deltopectoral groove, superficial to the deeper structures, but the axillary nerve is deeper and more distal, wrapping around the surgical neck. The vein is not directly superficial to the axillary nerve in the groove.

Correct Answer: D

The case content, under 'Biomechanics - Deforming Forces,' explicitly states: 'Supraspinatus: Pulls the greater tuberosity superiorly and posteriorly.' The greater tuberosity is the insertion site for the supraspinatus, infraspinatus, and teres minor tendons. Superior displacement is a classic sign of supraspinatus pull.

• Option A (Subscapularis): The subscapularis inserts into the lesser tuberosity and pulls it anteriorly and medially.
• Option B (Pectoralis major): The pectoralis major inserts more distally on the humerus and contributes to adduction and internal rotation of the shaft.
• Option C (Deltoid): The deltoid pulls the humeral shaft proximally and laterally.
• Option E (Latissimus dorsi): The latissimus dorsi inserts more distally on the humerus and contributes to adduction, extension, and internal rotation of the shaft.

Correct Answer: B

The patient's presentation of 'loss of reduction, and new varus collapse of the humeral head, with screws appearing to have migrated through the superior aspect of the humeral head' is a classic description of screw cutout and construct failure due to varus collapse. The case content explicitly states under 'Complications': 'Screw Cutout / Implant Failure... Etiology / Risk Factors: Osteoporotic bone, inadequate medial support (calcar screws), varus collapse, premature weight-bearing, poor screw purchase, poor reduction.' Inadequate medial calcar support is a critical factor in resisting varus collapse and preventing screw cutout.

• Option A (Iatrogenic axillary nerve injury during surgery): Axillary nerve injury would cause deltoid weakness and sensory loss, but not directly lead to varus collapse or screw cutout.
• Option C (Development of a deep surgical site infection): While infection is a serious complication, it typically presents with signs of inflammation, fever, and wound drainage, and while it can lead to nonunion or implant loosening, it's not the primary mechanism for acute varus collapse and screw cutout as described.
• Option D (Premature and aggressive post-operative rehabilitation): While this can contribute to implant failure, the fundamental structural weakness often stems from inadequate initial fixation, particularly medial support, which allows the varus collapse to initiate.
• Option E (Failure to repair the rotator cuff tendons to the plate): Suture augmentation of tuberosities is important for tuberosity healing and stability, but its absence is less directly linked to varus collapse of the humeral head and screw cutout than the lack of medial calcar support.

Correct Answer: C

The case content, under 'Pre-Operative Planning - Imaging,' states: 'Computed Tomography (CT) Scan: Indispensable for complex fractures, particularly three- and four-part fractures, fracture-dislocations, and head-splitting injuries. Provides detailed information on comminution, articular involvement, glenoid impression fractures, and precise tuberosity displacement. 3D reconstructions are invaluable for understanding fracture morphology and planning reduction maneuvers.'

• Option A (To assess for rotator cuff integrity and associated ligamentous injuries): MRI is generally better for assessing soft tissue structures like the rotator cuff and ligaments.
• Option B (To evaluate for brachial plexus pathology): While CT can show bony impingement, MRI or electrodiagnostic studies are more definitive for brachial plexus pathology.
• Option D (To confirm the presence of a fracture-dislocation, which is typically missed on standard radiographs): While CT can confirm, standard radiographs (AP, scapular Y, axillary lateral) are usually sufficient for initial diagnosis of fracture-dislocation. CT provides more detail, not just confirmation.
• Option E (To determine the extent of avascular necrosis (AVN) of the humeral head): AVN is a complication that develops over time. While CT can show signs of AVN in later stages, it's not the primary acute indication for CT in a fresh fracture-dislocation.

Correct Answer: B

The case content, under 'Patient Positioning - Beach Chair Position,' explicitly states: 'Precautions: Ensure adequate padding to all pressure points, especially the contralateral elbow, sacrum, and heels. Monitor blood pressure closely for potential cerebral hypoperfusion ('beach chair hypotension').'

• Option A (Ensuring the operative arm is tightly adducted to prevent nerve stretch): The operative arm is typically draped free to allow full manipulation, and tight adduction is not a standard precaution; rather, care is taken to avoid excessive traction or positioning that could stretch nerves.
• Option C (Placing an axillary roll under the dependent axilla to prevent brachial plexus compression): An axillary roll is a critical precaution for the lateral decubitus position, not typically for the beach chair position where the patient is semi-recumbent.
• Option D (Maintaining the patient in a steep Trendelenburg position to improve venous return): The beach chair position often involves a reverse Trendelenburg (head up) to reduce blood loss, not a steep Trendelenburg.
• Option E (Securing the head in maximal extension to facilitate airway management): The head is typically secured in a neutral or slightly flexed position, often in a horseshoe headrest, to protect the cervical spine and prevent nerve injury, not maximal extension.

Correct Answer: C

The case content, under 'Post-Operative Rehabilitation Protocols - Phase I Immobilization and Early Passive Motion,' states: 'Goals: Protect surgical repair, minimize pain and swelling, initiate early passive range of motion (PROM) to prevent stiffness... Exercises: Pendulum Exercises: Gentle, gravity-assisted swings... Initiated early, often within the first week... Passive Range of Motion (PROM): Forward Elevation (Flexion): Supine patient, therapist assists arm into flexion, staying below 90 degrees initially... Precautions: No active shoulder movement. No lifting, pushing, or pulling.'

• Option A (Active resistive strengthening exercises with light weights): This belongs to Phase III (Progressive Strengthening), much later in rehabilitation, after radiographic fracture union is confirmed.
• Option B (Full active range of motion (AROM) exercises, including overhead lifting): Full AROM and overhead lifting are typically not introduced until Phase II or III, and certainly not at 3 weeks post-op, as active movement and lifting are contraindicated in Phase I.
• Option D (Return to light recreational activities, such as golf or swimming): Return to light recreational activities is typically in Phase III, 4-6 months post-op, after full strength and range of motion are achieved.
• Option E (Manipulation Under Anesthesia (MUA) to address early stiffness): MUA is a surgical intervention for significant, persistent stiffness, usually considered much later (e.g., several months) if conservative therapy fails, not an early rehabilitation activity.

Historically, the arcuate branch of the anterior humeral circumflex artery was thought to provide the main blood supply to the humeral head. Recent quantitative studies have demonstrated that the posterior humeral circumflex artery provides the vast majority (approx. 64%) of the blood supply to the humeral head.

RTSA provides more reliable functional outcomes in elderly patients with 4-part proximal humerus fractures compared to hemiarthroplasty. Unlike hemiarthroplasty, the success of RTSA is not strictly dependent on the anatomic healing of the tuberosities.

The strongest predictors for nonunion of a Type II odontoid fracture are initial displacement > 5 mm, angulation > 10 degrees, and age > 50 years. Halo vest immobilization in the elderly is associated with high morbidity and mortality, making collar or surgery (if tolerable) the preferred choices.

Unilateral facet dislocations of the cervical spine typically result from a combined mechanism of flexion, distraction, and rotation. This causes one inferior articular process to ride forward and over the superior articular process of the vertebra below.

Hertel et al. identified specific predictors of humeral head ischemia. A metaphyseal head extension (calcar length) < 8 mm, disruption of the medial hinge, and an anatomic neck fracture pattern are the most accurate predictors of avascular necrosis.

Central cord syndrome is classically seen in elderly patients with pre-existing cervical spondylosis following a hyperextension injury. It presents with disproportionately greater motor impairment in the upper extremities compared to the lower extremities, typically affecting distal hand function the most.

Varus collapse of the humeral head after locked plating frequently leads to intra-articular screw penetration (screw cut-out). Placing inferior medial calcar screws during surgery provides crucial inferomedial support to prevent this specific complication.

Levine-Edwards Type IIA Hangman's fractures result from flexion-distraction and have a disrupted C2-C3 intervertebral disc. Skeletal traction is strictly contraindicated as it will further distract the injury and can cause severe neurologic compromise.

In the setting of reverse total shoulder arthroplasty for fracture, healing of the greater tuberosity is strongly correlated with improved active external rotation. Forward elevation is primarily restored by the deltoid muscle acting on the reverse biomechanical construct.

The presence of sensory or motor function in the lowest sacral segments (S4-S5) defines the injury as incomplete. Since sensory function is preserved (sacral sparing) but no motor function is preserved below the neurologic level, it is classified as ASIA B.

In an awake, cooperative, and neurologically intact patient with a cervical facet dislocation, rapid closed reduction via skeletal traction is safe and recommended without the need for a pre-reduction MRI. MRI is indicated prior to reduction only in obtunded or uncooperative patients.

The axillary nerve is the most commonly injured nerve in proximal humerus fractures. It supplies motor function to the deltoid and teres minor, and sensation to the lateral aspect of the proximal arm (superior lateral brachial cutaneous nerve).

The Rule of 12 (Harris lines) is used to diagnose atlanto-occipital dissociation. A basion-dental interval (BDI) or basion-axial interval (BAI) > 12 mm on a plain lateral radiograph or sagittal CT reconstruction is highly indicative of AOD.

To minimize the risk of subacromial impingement while ensuring adequate proximal screw purchase, the optimal position of a proximal humerus locking plate is 5-8 mm distal to the superior tip of the greater tuberosity.

According to the Rule of Spence, a combined lateral mass overhang of C1 on C2 greater than 6.9 mm on an AP open-mouth radiograph implies a rupture of the transverse ligament. This indicates a highly unstable C1 ring injury.

The deltopectoral approach utilizes the internervous plane between the deltoid (innervated by the axillary nerve) and the pectoralis major (innervated by the medial and lateral pectoral nerves). This protects the neurovascular supply to both muscles during deep dissection.

In the SLIC system, a facet fracture (morphology) is 1 point, disrupted discoligamentous complex (DLC) is 2 points, and intact neurologic status is 0 points. A total score of 3 generally indicates indeterminate management, often treated non-operatively in a collar depending on surgeon preference.

The vast majority of minimally displaced proximal humerus fractures are treated successfully with a sling. Early initiation of passive range of motion exercises (typically within 1 to 2 weeks) is crucial to prevent adhesive capsulitis and ensure optimal functional recovery.

Fractures in the ankylosed spine are highly unstable "chalk stick" type injuries and behave like long-bone fractures. Non-operative management or short-segment fusions have unacceptable failure rates; long-segment posterior instrumentation and fusion is the standard of care.

Vertebral artery injury is highly associated with cervical spine trauma involving subluxation, facet dislocations, and fractures extending into the transverse foramen. CT angiography is commonly recommended to screen for occlusion, dissection, or intimal tears in these patients.

In elderly patients with severe medical comorbidities, Type II odontoid fractures are increasingly managed non-operatively with a rigid cervical collar due to high morbidity and mortality associated with surgery and halo vests. Despite higher nonunion rates, clinical outcomes and survival are often equivalent to or better than aggressive surgical intervention in this high-risk group.

Unilateral facet dislocations typically result from a mechanism involving flexion combined with rotation. Radiographically, they classically present with less than 50% anterior translation of the vertebral body, whereas bilateral facet dislocations (hyperflexion-distraction injuries) present with 50% or more anterior translation.

This patient has Central Cord Syndrome, which classically occurs in older patients with cervical spondylosis who sustain a hyperextension injury. The mechanism involves pinching of the spinal cord between a bulging disc/osteophytes anteriorly and buckling ligamentum flavum posteriorly, leading to central gray matter hemorrhage and edema that disproportionately affects the medially located cervical motor tracts.

In an awake, cooperative, and neurologically intact patient with a cervical facet dislocation, rapid awake closed reduction with cranial traction is indicated before an MRI. Serial neurological exams are crucial; if the patient's neurologic status worsens during traction, the reduction attempt must be immediately aborted, and an emergent MRI should be obtained.

A Levine-Edwards Type IIa Hangman's fracture is characterized by severe angulation with minimal translation, resulting from a flexion-distraction injury. Cervical traction is strictly contraindicated as it will further distract the already disrupted C2-C3 intervertebral disc, potentially leading to catastrophic neurological compromise.

The patient is presenting with neurogenic shock, characterized by hypotension and bradycardia secondary to a loss of sympathetic tone. Norepinephrine is typically the first-line vasopressor because it provides both alpha-1 (vasoconstriction) and beta-1 (inotropy/chronotropy) adrenergic stimulation to effectively counteract the unopposed parasympathetic tone.

The Harris measurements, which include the basion-dental interval (BDI) and basion-axial interval (BAI), are considered highly sensitive for evaluating atlanto-occipital dissociation (AOD). A BDI > 12 mm on plain radiographs (or > 8.5 mm on CT scan) is highly indicative of AOD.

Hertel et al. identified that a calcar length of less than 8 mm attached to the articular segment, disruption of the medial hinge, and an anatomical neck fracture are the most reliable predictors of humeral head ischemia. The posterior circumflex humeral artery is the primary blood supply to the humeral head.

In an awake, alert, and cooperative patient with a cervical facet dislocation and neurologic deficit, immediate closed reduction with cranial traction is indicated without delaying for an MRI. An MRI is required prior to reduction only if the patient is obtunded or cannot reliably participate in a serial neurologic examination.

The axillary nerve is at high risk during surgical approaches to the proximal humerus, and its injury leads to deltoid and teres minor weakness (causing external rotation and abduction deficits). The anterior branch is particularly vulnerable if dissection strays beyond 5 cm distal to the lateral acromion.

Recent quantitative studies demonstrate that the posterior circumflex humeral artery provides roughly 64% of the blood supply to the humeral head. This updates historical teaching which incorrectly emphasized the anterior circumflex humeral artery and its anterolateral (arcuate) branch.

The Rule of Spence dictates that a combined lateral mass overhang of C1 on C2 greater than 6.9 mm on an open-mouth odontoid radiograph indicates a highly probable transverse ligament rupture. This dictates an unstable Jefferson fracture pattern requiring rigid immobilization or surgical fusion.

Placement of inferomedial calcar screws provides structural support to the medial column of the proximal humerus. This mechanically resists varus settling of the humeral head, which is the most common reason for secondary intra-articular screw cutout.

This patient has Central Cord Syndrome, characterized by motor deficits more severe in the upper extremities (especially distally) than the lower extremities. Prognosis for ambulation is generally good, but patients often suffer from permanent deficits in fine motor hand function.

In rTSA for fracture, successful healing of the tuberosities correlates with significantly improved active external rotation and overall joint stability. Failure of tuberosity healing can lead to poor external rotation strength and an increased risk of prosthesis dislocation.

A typical Hangman's fracture (traumatic spondylolisthesis of C2) is caused by hyperextension and axial loading, commonly seen in motor vehicle accidents or falls. However, Levine-Edwards Type IIA fractures uniquely involve flexion-distraction and require avoidance of traction during treatment.

In elderly patients with Type II odontoid fractures, halo vest immobilization is associated with high morbidity and mortality (up to 40% complication rate). Nonoperative management with a rigid cervical collar is generally preferred for stable patterns in frail elderly patients, accepting a higher nonunion rate for survival.

The "Bow-tie" or "Bat-wing" sign on a lateral cervical radiograph indicates rotational deformity characteristic of a unilateral facet dislocation. It represents the non-superimposed visual profiles of the right and left articular pillars.

Current EAST guidelines support the removal of the cervical collar in obtunded trauma patients following a negative high-quality, fine-cut CT scan. MRI or dynamic radiographs are no longer routinely required for clearance in this specific scenario if the CT is pristine.

Restoring appropriate humeral head height and version is critical in proximal humerus hemiarthroplasty. The superior border of the pectoralis major insertion is a highly reliable landmark, consistently located approximately 5.6 cm distal to the top of the humeral head.

Neurogenic shock occurs due to the loss of sympathetic tone following severe spinal cord injury, leading to unopposed parasympathetic activity. This presents classically as hypotension, bradycardia, and warm, peripherally vasodilated extremities.

Greater tuberosity fractures displaced more than 5 mm (and sometimes >3 mm in active overhead athletes) superiorly require surgical fixation. Nonoperative management of superiorly displaced fractures leads to severe subacromial impingement and loss of abduction.

In the presence of an extruded disc compressing the ventral cord following a facet dislocation, an anterior approach (ACDF) is mandatory. A direct posterior reduction maneuver in this setting can pull the herniated disc further into the spinal canal, causing iatrogenic cord injury.

During a deltopectoral approach, the cephalic vein is usually retracted laterally with the deltoid muscle. This preserves the primary venous drainage of the deltoid and minimizes postoperative swelling, although medial retraction is occasionally preferred by some surgeons.

An avulsion fracture of the lower cervical spinous processes (C6 or C7) is known as a Clay Shoveler's fracture. It is a stable injury, and conservative management with symptomatic pain control and a soft collar or early mobilization is the standard of care.

Surgical neck nonunions with a varus deformity require correction of the mechanical axis to succeed. A valgus-producing osteotomy combined with bone grafting and rigid locked plate fixation converts shear forces into compressive forces, optimizing the environment for union.

Anterior cord syndrome involves damage to the anterior two-thirds of the spinal cord (corticospinal and spinothalamic tracts), leading to loss of motor function and pain/temperature sensation. The posterior columns are spared, preserving proprioception, vibration, and fine touch.

Recent anatomic injection studies demonstrate that the posterior circumflex humeral artery provides the predominant blood supply (up to 64%) to the humeral head. This challenges the historical belief that the anterior circumflex humeral artery and its anterolateral branch (arcuate artery) were the primary sources.

Reverse total shoulder arthroplasty (RTSA) is indicated for elderly patients with displaced 4-part proximal humerus fractures, particularly when concurrent rotator cuff arthropathy or severe osteoarthritis is present. RTSA provides superior functional outcomes and more predictable pain relief compared to hemiarthroplasty or ORIF in this demographic.

In elderly patients with Type II odontoid fractures, rigid cervical collar immobilization is often preferred due to the high morbidity and mortality associated with halo vests and surgical intervention. Although nonunion rates are high with a collar, a stable fibrous nonunion is typically well-tolerated in this population.

Inferomedial calcar screws provide critical structural support to the medial column in proximal humerus fractures. Their proper placement significantly increases the biomechanical stability of the construct and reduces the risk of postoperative varus collapse and secondary screw cut-out.

According to Spence's rule, a combined lateral mass overhang of the C1 masses on C2 greater than 6.9 mm on an open-mouth odontoid radiograph indicates a competent transverse ligament rupture. MRI is often used today for confirmation, but 6.9 mm remains the classic threshold for instability.

The Neer classification defines a distinct fracture "part" only if the fragment is displaced by more than 1 centimeter or angulated by more than 45 degrees relative to the other major fragments.

Cervical spine fractures extending into the foramen transversarium, as well as significant subluxations like facet dislocations, pose a highly elevated risk for vertebral artery injury. CTA of the neck is the recommended screening modality for these specific, high-risk injury patterns.