ABOS Part I Orthopedic Surgery Review: Proximal Humerus, Hip Arthroplasty & Acetabular Fractures | Part 21544

Correct Answer: D

The case describes a 72-year-old female with a displaced two-part surgical neck fracture. While the fracture is displaced beyond the typical non-operative criteria (>1 cm displacement, >45 degrees angulation), the text emphasizes that non-operative management is often appropriate for 'two-part surgical neck fractures in elderly, low-demand patients with minimal displacement' and for 'elderly, low-demand, sedentary patients' even with significant comorbidities. However, the patient's activity level (gardening, playing cards) suggests she is not entirely sedentary. The PROXIMAL trial (2015) specifically found no significant difference in outcomes between locking plate fixation and non-operative treatment for displaced proximal humerus fractures in adults, particularly in an older population. This supports a more critical selection of surgical candidates and often favors non-operative management initially, especially for two-part surgical neck fractures, even if displaced, in older individuals who are not high-demand athletes. Early pendulum exercises are a cornerstone of non-operative rehabilitation to prevent stiffness.

Option A (ORIF) might be considered for younger, active patients or specific fracture patterns, but for an elderly patient with a two-part surgical neck fracture, the PROXIMAL trial suggests it may not offer superior outcomes to non-operative care, and carries surgical risks.

Options B (Hemiarthroplasty) and C (RTSA) are typically reserved for more complex fractures (e.g., comminuted three- or four-part fractures, head-splitting fractures, severe osteopenia, or compromised rotator cuff), which are not described here. A two-part surgical neck fracture does not typically warrant arthroplasty as an initial treatment.

Option E (Closed reduction and percutaneous pinning) is less common for displaced surgical neck fractures in the elderly due to concerns about pin tract infection, loss of reduction, and difficulty achieving stable fixation in osteoporotic bone compared to locking plates, and is not explicitly mentioned as a primary option for this specific scenario in the text.

Correct Answer: D

The Neer classification system categorizes PHFs based on the number of displaced 'parts' (humeral head, greater tuberosity, lesser tuberosity, and surgical neck) and displacement criteria (>1 cm displacement or >45 degrees angulation). The question states 'displacement of the greater tuberosity, lesser tuberosity, and surgical neck fragments relative to the humeral head.' This means three segments (greater tuberosity, lesser tuberosity, surgical neck) are displaced relative to the humeral head, which itself is considered the fourth part. Therefore, this is a four-part fracture.

A one-part fracture is nondisplaced or minimally displaced.

A two-part fracture involves displacement of one major segment relative to the others (e.g., surgical neck, greater tuberosity).

A three-part fracture involves displacement of two segments relative to the humeral head.

A fracture-dislocation involves any of the above combined with glenohumeral dislocation, which is not described here as the humeral head remains in anatomical alignment with the glenoid.

Correct Answer: D

The text explicitly states: 'The 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.' This makes it the structure at highest risk during dissection around the surgical neck.

The Musculocutaneous nerve is located more medially and anteriorly, supplying the biceps and brachialis, and is generally less vulnerable during a standard deltopectoral approach to the surgical neck.

The Radial nerve is located more distally and posteriorly in the spiral groove, making it less susceptible to injury during proximal humerus plating via a deltopectoral approach.

The Axillary artery and vein are positioned medially and anteriorly, at risk during medial screw placement or extreme retraction, but the axillary nerve is more directly in the path of dissection around the surgical neck.

The Brachial plexus is vulnerable in high-energy injuries or fracture-dislocations but is generally not the most commonly injured structure during a standard deltopectoral approach for fracture fixation unless there is extreme retraction or a very proximal and medial dissection.

Correct Answer: D

The scenario describes 'collapse of the humeral head into a varus deformity, with several screws having penetrated the articular surface.' This is a classic presentation of screw cutout and varus collapse. The text explicitly states: 'Loss of medial calcar support significantly increases the risk of screw cutout and construct failure.' It further notes that 'Calcar Screws: Crucial for medial column support. At least one, ideally two, calcar screws should be directed inferiorly and medially towards the calcar region to resist varus collapse.' Therefore, inadequate medial calcar support is the most direct cause of varus collapse and subsequent screw cutout.

Inadequate fixation of the lesser tuberosity (A) would primarily lead to internal rotation deformity or subscapularis dysfunction, not typically varus collapse and screw cutout.

Excessive external rotation during early rehabilitation (B) could stress tuberosity repairs or lead to dislocation in unstable fractures, but is not the primary mechanism for varus collapse and screw cutout.

Disruption of the posterior circumflex humeral artery (C) contributes to avascular necrosis (AVN), which is a different complication, although AVN can eventually lead to collapse. However, the immediate description of varus collapse and screw cutout points more directly to mechanical failure of fixation due to lack of support.

Premature removal of the sling at 2 weeks post-op (E) would primarily risk loss of reduction or stress on healing soft tissues, but the fundamental mechanical failure described (varus collapse, screw cutout) is more related to the initial construct stability, particularly medial support.

Correct Answer: C

The text states, 'Displaced Greater Tuberosity Fractures: Displacement >5 mm, particularly in active patients, due to the high risk of impingement and rotator cuff dysfunction if left unreduced. Can lead to subacromial impingement and weakness.' This directly addresses the scenario of a displaced greater tuberosity fracture in an active patient.

High risk of avascular necrosis of the humeral head (A) is primarily associated with multi-part fractures (three- and four-part) and head-splitting fractures, not typically an isolated displaced greater tuberosity fracture.

Potential for internal rotation contracture (B) is more commonly associated with displaced lesser tuberosity fractures, which affect the subscapularis tendon.

Difficulty achieving union with non-operative management (D) is not the primary concern for displaced greater tuberosity fractures; rather, it's the functional impairment from malunion (impingement, cuff dysfunction) that drives operative indications.

Increased risk of axillary nerve injury with conservative care (E) is incorrect. Axillary nerve injury is a risk of the initial trauma or surgical intervention, not conservative management.

Correct Answer: D

The patient presents with a 'highly comminuted four-part proximal humerus fracture,' 'severe osteoporosis,' and a 'massive, irreparable rotator cuff tear' in an 'elderly' patient. The text explicitly states: '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 perfectly matches the patient's profile and desired outcome.

ORIF with a locking plate (A) would be highly challenging and likely to fail given the severe comminution, severe osteoporosis, and irreparable rotator cuff tear. The ability to achieve stable fixation and tuberosity healing would be severely compromised.

Hemiarthroplasty (B) has historically been an option for complex fractures in older patients, but the text notes 'outcomes can be variable, often limited by tuberosity healing and rotator cuff function.' Given the irreparable rotator cuff tear and severe osteoporosis, hemiarthroplasty would likely yield poor functional results.

Non-operative management (C) for a highly comminuted four-part fracture in a patient desiring function would likely result in significant pain, malunion, and very poor function.

Intramedullary nailing (E) is less common for complex PHFs and is generally not indicated for four-part fractures, especially with severe osteoporosis and rotator cuff compromise, due to difficulty controlling head rotation and potential for AVN.

Correct Answer: C

The text states, regarding the Beach Chair Position: 'Advantages: Excellent visualization for the deltopectoral approach, allows for easy assessment of shoulder range of motion during the procedure, less blood loss due to reverse Trendelenburg, and ability to assess rotator cuff integrity.' The image depicts a patient draped for shoulder surgery, consistent with either beach chair or lateral decubitus, but the question specifically asks about the advantages of the Beach Chair position.

Option A is incorrect; the text suggests lateral decubitus 'May offer improved stability for patients with certain comorbidities,' implying beach chair might be less stable in some cases.

Option B is incorrect; while arthroscopy can be done in beach chair, the text mentions lateral decubitus 'Can be preferred... if shoulder arthroscopy is concurrently planned.'

Option D is incorrect; the text explicitly lists 'Monitor blood pressure closely for potential cerebral hypoperfusion ("beach chair hypotension")' as a precaution, indicating a risk, not a minimization of risk.

Option E is incorrect; the text states beach chair provides 'Excellent visualization for the deltopectoral approach,' which is an anterior approach. Lateral decubitus 'Can be preferred for certain posterior approaches.'

Correct Answer: B

The text highlights the importance of CT scans: '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.' For a displaced two-part surgical neck fracture, understanding the extent of comminution and any subtle articular involvement (even if not a primary head-splitting fracture) is crucial for selecting the appropriate plate, screw trajectories, and reduction techniques to restore anatomy and prevent complications like screw cutout or post-traumatic arthritis.

Assessment of rotator cuff integrity (A) is more typically done with MRI, though severe tears might be suspected clinically. While important, CT's primary strength for fracture planning is bony detail.

Identification of brachial plexus pathology (C) is also better assessed with MRI or clinical neurophysiological studies, not typically the primary role of CT in acute fracture planning.

Confirmation of axillary nerve course (D) is generally understood anatomically (5-7 cm distal to acromion) and protected surgically; CT is not typically used to map nerve courses for routine PHF planning.

Evaluation of pre-existing shoulder arthritis (E) can be seen on radiographs and CT, but for an acute fracture, the primary focus of the CT is the fracture itself and its implications for fixation, rather than pre-existing arthritis unless it's a major factor influencing arthroplasty decision-making.

Correct Answer: C

The text describes Phase I (Immobilization and Early Passive Motion) goals as 'Protect surgical repair, minimize pain and swelling, initiate early passive range of motion (PROM) to prevent stiffness, maintain distal extremity function.' Under 'Exercises,' it specifically lists 'Pendulum Exercises: Gentle, gravity-assisted swings of the arm (flexion/extension, internal/external rotation, circumduction). Initiated early, often within the first week, based on pain and fracture stability.'

Active shoulder abduction against gravity (A) is an active movement and is explicitly contraindicated in Phase I, which states 'No active shoulder movement.'

Resistive isometric external rotation (B) is a strengthening exercise, typically introduced in Phase II or III, not Phase I.

Active-assisted shoulder flexion using a pulley system (D) is an AAROM exercise, typically introduced in Phase II, not Phase I.

Weight-bearing on the affected arm (E) is a strict precaution throughout early phases and is explicitly stated as 'No weight-bearing on the affected arm' in Phase I precautions.

Correct Answer: C

The text states, under 'Deltopectoral Groove' dissection: 'The cephalic vein is typically retracted laterally with the deltoid, but can be ligated and divided if necessary for better exposure, particularly in revision cases or when space is limited. Care should be taken to preserve smaller venous tributaries.'

Option A is incorrect because it is not routinely ligated and divided, but rather 'if necessary.'

Option B is incorrect; it is retracted laterally with the deltoid, not medially with the pectoralis major.

Option D is incorrect; there is no mention of dissecting it free and transposing it.

Option E is incorrect; while preservation is preferred, it is often retracted, and can be ligated if necessary, so 'always preserved without retraction' is too absolute.

Correct Answer: C

The text explicitly highlights the importance of the medial calcar: '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.' Furthermore, under 'Head Fixation,' it states: 'Calcar Screws: Crucial for medial column support. At least one, ideally two, calcar screws should be directed inferiorly and medially towards the calcar region to resist varus collapse.'

Cortical screws in the greater tuberosity (A) are important for tuberosity fixation and rotator cuff integrity but do not primarily resist varus collapse of the humeral head.

Lag screws across the anatomical neck (B) are not specifically mentioned as crucial for resisting varus collapse in the context of locking plate fixation for PHFs; locking screws provide angular stability.

Screws placed through the bicipital groove (D) are not a standard or recommended practice for head fixation and could damage the biceps tendon.

Screws directed superiorly into the acromion (E) would be an extra-articular fixation and is not part of standard proximal humerus plating for head fixation.

Correct Answer: C

The most compelling indication for Total Hip Arthroplasty (THA) in this patient is the failure of comprehensive non-operative management to provide sustained symptomatic relief and functional improvement. The case explicitly states the patient had a 5-year history of debilitating pain, failed NSAIDs, physical therapy, and only transient relief from a corticosteroid injection. This, combined with severe functional limitations (walking <100m, difficulty with ADLs) and radiographic evidence of Kellgren-Lawrence Grade IV osteoarthritis, are the primary drivers for surgical intervention. While age (A), BMI (B), controlled comorbidities (D), and patient motivation (E) are all important factors in surgical decision-making, they are not the primary indications for the procedure itself. Age is a factor for implant choice and overall health, BMI is a risk factor, controlled comorbidities are necessary for medical fitness, and patient desire is crucial for compliance and realistic expectations, but none of these alone indicate the need for surgery without the underlying pathology and failure of conservative care.

Correct Answer: C

The described pattern of range of motion (ROM) restriction, particularly the significant loss of internal rotation and the presence of a fixed flexion deformity, is a classic presentation of advanced primary osteoarthritis of the hip. Osteoarthritis typically affects the anterior and superior aspects of the joint first, leading to a progressive loss of internal rotation and extension. The fixed flexion deformity is a common compensatory mechanism to reduce pain. While other conditions can cause hip pain and ROM restriction, early avascular necrosis (A) might present with pain and restricted IR but typically without the extensive fixed flexion deformity or global ROM loss seen in advanced OA. Inflammatory arthropathy (B) often presents with more symmetric polyarticular involvement and different pain characteristics (worse with rest). A labral tear (D) typically causes mechanical symptoms like clicking or catching and pain with specific movements, but not usually the global, severe ROM restriction and fixed deformity of advanced OA. Greater trochanteric bursitis (E) causes lateral hip pain and tenderness, with ROM typically preserved, especially internal rotation.

Correct Answer: D

The Kellgren-Lawrence classification system is a widely used radiographic grading scale for osteoarthritis. The described findings of 'severe tricompartmental joint space narrowing, subchondral sclerosis, extensive osteophyte formation, subchondral cyst formation, and definite deformity of bone ends' are the hallmarks of Grade IV osteoarthritis. Grade I involves doubtful narrowing and possible osteophytes. Grade II shows definite osteophytes and possible narrowing. Grade III includes moderate osteophytes, definite joint space narrowing, and some sclerosis. Grade V is not a standard Kellgren-Lawrence grade; the highest is Grade IV, which represents severe disease. The case explicitly states the Kellgren-Lawrence grade for the left hip was IV, reinforcing this answer.

Correct Answer: B

Restoration of femoral offset is most critical for optimizing abductor muscle efficiency and minimizing the risk of a post-operative Trendelenburg gait. Femoral offset refers to the horizontal distance from the center of rotation of the femoral head to the long axis of the femur. Increasing the offset lengthens the abductor lever arm, allowing the gluteus medius and minimus muscles to generate more torque with less force, thereby improving their efficiency and reducing the likelihood of abductor insufficiency (Trendelenburg gait). While acetabular inclination (A) and anteversion (C) are crucial for stability and wear, and femoral stem anteversion (E) is important for preventing impingement and dislocation, they do not directly impact the abductor lever arm as significantly as femoral offset. Femoral head diameter (D) primarily influences range of motion and jump distance for stability, but not directly abductor mechanics.

Correct Answer: C

Rheumatoid arthritis (RA) is least likely to be the primary diagnosis. The patient's presentation with mechanical pain, morning stiffness lasting 45 minutes (typical for OA, RA is usually >1 hour), and radiographic findings of osteophytes, subchondral sclerosis, and cysts are classic for osteoarthritis. RA typically presents with inflammatory pain (worse with rest), symmetric polyarthritis, and radiographic features of concentric joint space narrowing, erosions, and juxta-articular osteopenia, with an absence of osteophytes. Furthermore, inflammatory markers (ESR, CRP) would typically be elevated in active RA, which were normal in this patient. Primary osteoarthritis (A) is the most likely diagnosis. AVN (B) can cause similar pain but has distinct radiographic features (crescent sign, patchy sclerosis/lucency) and MRI is diagnostic. Post-traumatic OA (D) and DDH leading to secondary OA (E) are forms of osteoarthritis and would present with similar clinical and radiographic features to primary OA, making them plausible differential diagnoses for the type of OA, but not fundamentally different conditions like RA.

Correct Answer: C

A Dorr Type B femur, characterized by good metaphyseal-diaphyseal flare and adequate cortical thickness, provides excellent bone stock for achieving primary press-fit stability. This morphology is considered ideal for a fully uncemented (cementless) femoral stem. Uncemented stems rely on this initial mechanical stability (press-fit) and subsequent biological fixation through bone ingrowth into a porous coating. Dorr Type A femurs (champagne flute, thick cortex, narrow canal) are at higher risk of fracture with uncemented stems and may sometimes benefit from cemented stems. Dorr Type C femurs (stovepipe, thin cortex, wide canal) often lack sufficient metaphyseal bone for press-fit and are typically better suited for cemented stems or specific uncemented designs that achieve diaphyseal fixation. Cemented stems (A, B) are generally preferred in osteoporotic bone or in cases where primary press-fit cannot be reliably achieved. Resurfacing arthroplasty (D) is a bone-preserving option for younger, active patients with good bone quality, but not directly related to the Dorr classification for stem fixation. Custom-made stems (E) are reserved for severe deformities or bone loss, not typically a standard Dorr Type B femur.

Correct Answer: D

In a posterior approach to the hip, the short external rotators (piriformis, gemelli, obturator internus) and the posterior capsule are incised to gain access to the hip joint. Meticulous repair of these structures at the time of closure is paramount for enhancing post-operative stability and significantly reducing the risk of posterior dislocation. This repair helps to restore the natural soft tissue restraints against posterior dislocation. The gluteus medius (A) is typically split or retracted, but its primary role is abduction, and its repair is not as directly linked to posterior stability as the rotators and capsule. The iliopsoas (B) and rectus femoris (C) are anterior structures and are not typically violated in a posterior approach. The vastus lateralis fascia (E) is part of the quadriceps mechanism and not directly involved in hip joint stability in this context.

Correct Answer: C

A Dorr Type A femur, characterized by a narrow canal and very thick cortical bone (often described as a 'champagne flute' shape), is particularly susceptible to intraoperative femoral fracture during broaching or stem impaction, especially when attempting to achieve a press-fit with an uncemented stem. The rigid, thick cortex offers little elasticity, and forceful impaction can lead to a crack or fracture. Sciatic nerve injury (A) is a risk with excessive leg lengthening or aggressive posterior retraction, but not directly from broaching in a Dorr A femur. Acetabular medial wall perforation (B) and external iliac artery injury (D) are risks associated with acetabular reaming or screw placement, not femoral preparation. Excessive leg lengthening (E) is a concern during trial reduction and final component selection, not typically a direct result of broaching itself, though an undersized stem in a large canal could contribute to instability requiring lengthening.

Correct Answer: D

For a patient who has undergone THA via a posterior approach, the combination of hip flexion beyond 90 degrees, adduction past midline, and internal rotation is the classic position that places the hip at highest risk for posterior dislocation. Therefore, patients are strictly instructed to avoid this combination of movements in the immediate post-operative period. Immediate weight-bearing as tolerated (A) is standard for uncemented components. Gentle hip abduction exercises (B) are encouraged to strengthen abductors. Sleeping on the operative side with a pillow between the legs (C) is often recommended to maintain abduction and prevent adduction. Stationary cycling (E) is a low-impact exercise that can be introduced in early rehabilitation, provided the seat height is adjusted to prevent excessive hip flexion.

Correct Answer: C

An MRI scan is considered the diagnostic gold standard for avascular necrosis (AVN) of the femoral head, especially in early stages where X-ray findings may be equivocal or normal. MRI can detect marrow edema, serpentine low signal lines, and characteristic T1/T2 signal changes indicative of AVN before subchondral collapse or other radiographic signs become apparent. Severe acetabular retroversion (A) and significant femoral anteversion (B) are bony deformities best assessed by CT scan, which provides superior bony detail and 3D reconstruction. Extensive heterotopic ossification (D) is typically visible on X-rays, and CT can provide more detail, but MRI is not the primary modality for its diagnosis. Periprosthetic joint infection (E) is diagnosed based on clinical signs, lab markers (ESR, CRP, leukocyte count), aspiration, and sometimes nuclear imaging, with MRI having limited specific utility for PJI diagnosis due to artifact from metal implants.

Correct Answer: C

The correct answer is the Anterior column. The case explicitly states that the fracture involves the anterior superior iliac spine (ASIS), extends through the iliopectineal line, and involves the superior pubic ramus. According to the 'Surgical Anatomy & Biomechanics' section, the anterior column is defined as extending from the ASIS through the iliopectineal line, crossing the anterior acetabulum to the superior pubic ramus. It also includes the anterior half of the acetabular roof. This description perfectly matches the fracture pattern described in the vignette. The posterior column, posterior wall, transverse, and both column fractures involve different anatomical structures and fracture lines as detailed in the Judet and Letournel classification.

Correct Answer: C

The correct answer is the Sciatic nerve. The 'Detailed Surgical Approach / Technique' section, specifically under the Kocher-Langenbeck Approach, highlights the sciatic nerve as a 'CRITICAL' structure. It states that the sciatic nerve lies deep to the piriformis and obturator internus, medial to the lesser sciatic notch, and 'It must be carefully identified, protected, and retracted (usually medially).' Traction on the limb should also be monitored to prevent iatrogenic nerve stretch. The femoral nerve and external iliac vein are anterior structures, primarily at risk during anterior approaches. The superior gluteal artery is vulnerable during extended iliofemoral and Kocher-Langenbeck approaches, particularly near the greater sciatic notch, but the sciatic nerve is the most prominent and consistently at risk nerve during posterior approaches. The obturator nerve is located more medially within the pelvis, deep to the quadrilateral plate.

Correct Answer: D

The correct answer is the Corona Mortis. The 'Surgical Anatomy & Biomechanics' section explicitly mentions the 'Corona Mortis (Aberrant Obturator Artery)' as an anatomical variant, a vascular connection between the obturator and external iliac/inferior epigastric arteries, often crossing the superior pubic ramus. It states that 'Laceration can lead to significant hemorrhage during Stoppa or ilioinguinal approaches.' The 'Detailed Surgical Approach / Technique' section, under the Ilioinguinal Approach, further emphasizes this, stating, 'CRITICAL: Identify and ligate the "Corona Mortis"... if present, to prevent significant hemorrhage.' While the obturator artery is involved in this anastomosis, the specific term for the variant connection at risk in this region is the Corona Mortis. The superior gluteal artery is posterior, and the femoral and inferior epigastric arteries are typically identified but the specific variant at high risk of unexpected hemorrhage in the medial window is the Corona Mortis.

Correct Answer: C

The correct answer is Open reduction and internal fixation (ORIF). The 'Indications & Contraindications' section clearly states that a primary indication for operative management is 'Displacement: Intra-articular displacement of ≥ 2 mm (some argue for 1 mm in younger patients in the weight-bearing dome).' In this vignette, the patient has a 3 mm articular step-off, which exceeds the 2 mm threshold, making operative management indicated despite the hip being stable and the posterior wall involvement (30%) being below the 40-50% threshold for inherent instability. Non-operative management is reserved for displacements less than 2 mm. Urgent closed reduction and spica cast are not appropriate for a stable, displaced posterior wall fracture. Primary total hip arthroplasty is typically considered for elderly patients with osteoporotic, complex fractures or as a salvage procedure for PTOA. Delaying ORIF beyond 3 weeks is a relative contraindication due to callus formation, making reduction more challenging.

Correct Answer: C

The correct answer is Thin-slice CT with 2D and 3D reconstructions. The 'Pre-Operative Planning & Patient Positioning' section, under 'Imaging Analysis,' explicitly states that 'Computed Tomography (CT) Scan: Essential for definitive diagnosis and surgical planning.' It further elaborates that 'Thin-slice CT with 2D and 3D Reconstructions provides detailed visualization of fracture lines, comminution, articular step-off, intra-articular fragments, quadrilateral surface involvement, and femoral head integrity. It is invaluable for understanding fracture morphology and choosing the appropriate surgical approach.' While plain radiographs are initial and help classify, they lack the detail needed for surgical planning. MRI is rarely indicated acutely unless specific soft tissue or chondral injuries are suspected. Ultrasound and bone scintigraphy have no primary role in acute acetabular fracture diagnosis and surgical planning.

Correct Answer: D

The correct answer is NSAIDs or radiation therapy. The 'Complications & Management' section lists Heterotopic Ossification (HO) as a common complication with an incidence of 10-50% (radiographically), noting it is 'More common with extended approaches, head injury, male sex, concomitant elbow injury.' The management strategy for HO prophylaxis is 'NSAIDs (e.g., Indomethacin) for 3-6 weeks post-op, or single-dose post-op radiation therapy (700-800 cGy).' Long-term oral antibiotics are not a standard prophylactic measure for HO. Early full weight-bearing is generally contraindicated in the immediate post-operative period for acetabular fractures. CPM may be used for ROM but is not specifically for HO prophylaxis. Urgent hardware removal is a treatment for hardware-related complications, not a prophylactic measure.

Correct Answer: D

The correct answer is Post-traumatic osteoarthritis (PTOA). The 'Complications & Management' section identifies PTOA as a very common long-term complication (20-80% incidence), described as 'Progressive degeneration of the articular cartilage, leading to pain, stiffness, and functional limitation. Directly correlated with quality of reduction.' The symptoms of progressive hip pain, stiffness, and radiographic findings of joint space narrowing, subchondral sclerosis, and osteophytes are classic signs of osteoarthritis. While AVN, hardware failure, HO, and nonunion are possible complications, the clinical presentation and radiographic findings described are most consistent with PTOA, especially given the 5-year post-operative timeframe and initial fracture union.

Correct Answer: C

The correct answer is Non-weight bearing (NWB) on the operative extremity. The 'Post-Operative Rehabilitation Protocols' section, under 'Phase Immediate Post-Operative (Weeks 0-6),' clearly states for weight-bearing: 'Non-Weight Bearing (NWB) on the operative extremity. Ambulation with crutches or a walker. Foot-flat weight-bearing or toe-touch weight-bearing (TTWB) may be allowed by some surgeons for stability, but NWB is generally safer.' Regarding range of motion, it advises 'Active-Assisted ROM (AAROM) and Gentle Passive ROM (PROM): Within pain limits. Avoid extremes of motion, especially positions that stress the fracture fragments (e.g., deep flexion, adduction, internal rotation for posterior fractures).' Therefore, full or partial weight-bearing and unrestricted or deep hip flexion are not appropriate in this immediate phase.

Correct Answer: D

The correct answer is Anatomical reduction with <1-2 mm step-off/gap. The 'Summary of Key Literature / Guidelines' section explicitly states: 'Long-term follow-up studies consistently demonstrate a strong correlation between anatomical reduction (< 1-2 mm step-off/gap) and superior functional outcomes, reduced rates of PTOA, and less need for subsequent THA.' While other factors like DVT prophylaxis are important for preventing complications, and surgical approach is critical for achieving reduction, the quality of the articular reduction itself is the most direct and consistently cited predictor of long-term joint health and function. Early full weight-bearing is not recommended and patient age is a risk factor for certain complications, but not the primary determinant of long-term outcome quality after fixation.

Correct Answer: C

The correct answer is Primary total hip arthroplasty (THA). The 'Summary of Key Literature / Guidelines' section, under 'Management in the Elderly,' states: 'Acetabular fractures in osteoporotic elderly patients present unique challenges. While anatomical reduction and fixation are still desirable, bone quality can make fixation tenuous. Debates continue regarding the role of primary total hip arthroplasty (THA) in severely comminuted or multi-column fractures in this population, as it may offer earlier mobilization and potentially better functional outcomes in selected cases, despite being a more extensive procedure.' Given the patient's advanced age, severe osteoporosis, and a highly comminuted both column fracture, primary THA is a recognized alternative to ORIF, which might be challenging to achieve stable fixation in poor bone quality. Non-operative management with prolonged bed rest is generally associated with high morbidity in the elderly. External fixation is typically for pelvic ring injuries or temporary stabilization, not definitive acetabular fixation. Arthrodesis is rarely performed and generally offers poorer quality of life.

Correct Answer: C

The case explicitly states, "Prolonged dislocation time directly correlates with increased rates of critical complications, particularly avascular necrosis (AVN) of the femoral head and sciatic nerve injury." It further emphasizes, "The incidence is directly proportional to the time to reduction and the energy of the injury." Numerous studies consistently demonstrate a direct inverse relationship between prompt reduction (ideally within 6 hours, optimally within 1-2 hours) and the incidence of AVN. Delays beyond 12-24 hours dramatically increase AVN rates to over 40-50%. While other factors listed can influence overall outcome, the time to reduction is the single most critical determinant for preventing AVN.

Correct Answer: C

The case highlights the "Medial Circumflex Femoral Artery (MCFA): The primary blood supply to the femoral head in adults, ascending posteriorly and superiorly along the posterior aspect of the femoral neck, deep to the quadratus femoris and obturator externus. Damage to this artery, particularly its retinacular branches, is the main etiology of femoral head AVN following dislocation." The obturator artery via the ligamentum teres provides minimal blood supply in adults. The superior and inferior gluteal arteries supply the gluteal muscles and surrounding structures, while the lateral circumflex femoral artery primarily supplies the greater trochanter and vastus lateralis, not the femoral head itself.

Correct Answer: C

The case explicitly states, "Absolute contraindications to attempting closed reduction are rare but include: Femoral neck fracture: This is a crucial contraindication. Attempting closed reduction in the presence of an ipsilateral femoral neck fracture can convert a non-displaced fracture into a displaced one, or cause further displacement, increasing the risk of AVN or nonunion. This requires careful pre-reduction imaging." Therefore, before any reduction attempt, a CT scan is essential to definitively rule out or characterize a femoral neck fracture, which would necessitate operative management.

Correct Answer: C

The case emphasizes that "A CT scan of the pelvis and hip is generally recommended after successful closed reduction to: Confirm concentric reduction. Identify incarcerated osteochondral fragments or soft tissue within the joint. Precisely characterize associated acetabular or femoral head fractures (size, displacement, articular involvement). Assess for occult femoral neck or intertrochanteric fractures missed on plain radiographs." While plain X-rays may appear concentric, a CT scan is crucial to detect subtle intra-articular fragments or occult fractures that could lead to post-traumatic arthritis or instability if not addressed. MRI is more sensitive for AVN, but AVN is a later complication, and the immediate priority after reduction is to confirm concentricity and rule out incarcerated fragments/fractures.

Correct Answer: C

The case clearly outlines the key principles for emergency closed reduction: "Regardless of the specific maneuver, key principles apply: 1. Adequate Muscle Relaxation: Absolutely paramount. Without it, forceful reduction attempts can lead to iatrogenic fractures or cartilage damage. 2. Axial Traction: Apply steady, sustained axial traction in line with the femoral shaft, aiming to distract the femoral head from the acetabulum." Forceful maneuvers without adequate relaxation increase the risk of iatrogenic injury. Hip flexion (often 60-90 degrees) is typically used to relax the powerful hip flexors and iliofemoral ligament, making option E incorrect. Immediate post-reduction weight-bearing is not recommended, especially for complex dislocations.

Correct Answer: C

The case describes the Kocher-Langenbeck approach and states, "The sciatic nerve lies deep to the piriformis and superficial to the quadratus femoris. It is highly vulnerable. Careful identification and protection are paramount. Identify the nerve early and retract it gently, typically medially." The illustration shows the posterior aspect of the hip, where the sciatic nerve is located. The femoral and obturator nerves are anterior/medial, and the superior gluteal nerve is more superior. While the medial circumflex femoral artery is critical for femoral head vascularity, the question specifically asks about a neurovascular structure to be identified and retracted during the deep dissection of the posterior approach, making the sciatic nerve the most prominent and vulnerable neural structure in this field.

Correct Answer: C

The case states, "Sciatic Nerve Injury: The peroneal division is more commonly affected due to its relative fixation and more superficial course. Most sciatic nerve palsies following hip dislocation are neurapraxias and resolve spontaneously within 6-12 months." Foot drop, weakness in ankle dorsiflexion and eversion, and sensory loss over the dorsum of the foot are classic symptoms of common peroneal nerve injury. Most of these injuries are neurapraxias (stretch injuries) and have a good prognosis for spontaneous recovery over several months.

Correct Answer: C

The case states, "Heterotopic Ossification (HO): ...Patients undergoing open reduction, especially those with associated head injuries, are at higher risk for HO. Prophylaxis with non-steroidal anti-inflammatory drugs (NSAIDs) such as indomethacin (e.g., 25 mg TID for 3-6 weeks) or a single dose of post-operative radiation (700-800 cGy) has been shown to be effective in preventing symptomatic HO." A history of TBI is a well-known risk factor for HO. LMWH is for DVT prophylaxis, not HO. Aggressive ROM or strict immobilization are not primary HO prophylaxis methods and can be detrimental.

Correct Answer: D

The case outlines the management of Pipkin fractures: "Pipkin Type I (below fovea) and Type II (above fovea): Require anatomical reduction and stable internal fixation (typically headless compression screws). Excision of small, non-weight-bearing fragments may be considered." Given that the fragment is displaced and involves the weight-bearing superior aspect of the femoral head, anatomical reduction and stable internal fixation are crucial to restore articular congruity and prevent post-traumatic arthritis. Excision is typically reserved for very small, non-weight-bearing fragments. THA is generally reserved for end-stage arthritis or advanced AVN, not as an immediate treatment for an acute Pipkin Type II fracture in a 42-year-old.

Correct Answer: C

The case details post-operative rehabilitation: "Open Reduction / Associated Fractures (e.g., posterior wall): Strict non-weight-bearing (NWB) for 6-12 weeks, depending on fracture stability, hardware, and surgeon preference. This protects the healing capsule, repaired soft tissues, and any internal fixation. Range of Motion (ROM): Gentle, pain-free ROM within protective limits. Avoid the 'dislocating position' (flexion > 90°, adduction, internal rotation)." Full or partial weight-bearing would jeopardize the healing fracture and fixation. Unrestricted ROM or full flexion/internal rotation would risk re-dislocation or damage to the repair. Therefore, strict NWB with protected ROM is the safest initial approach.

Historical teaching emphasized the ascending branch of the anterior humeral circumflex artery. However, recent perfusion studies demonstrated that the posterior humeral circumflex artery supplies approximately 64% of the blood to the humeral head.

The direct anterior approach utilizes the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve courses superficially across this interval and is highly susceptible to traction or transection injury.

The corona mortis is a critical vascular anastomosis between the obturator (internal iliac system) and external iliac (or inferior epigastric) vessels located over the superior pubic ramus. It must be identified and ligated during ilioinguinal or modified Stoppa approaches to prevent life-threatening hemorrhage.

In reverse shoulder arthroplasty for fractures, the deltoid reliably restores forward elevation regardless of tuberosity healing. However, anatomical healing of the greater tuberosity (which houses the infraspinatus and teres minor) is crucial for restoring active external rotation and maximizing functional scores.

A T-type fracture involves a transverse fracture through both columns combined with an inferior vertical split through the obturator ring. Because a portion of the articular roof remains attached to the intact posterior ilium, it is excluded from being an associated both-column fracture.

Squeaking in ceramic-on-ceramic THA is frequently caused by edge loading of the bearing surfaces. This edge loading is typically secondary to cup malposition, specifically excessive inclination (a steep cup) and excessive anteversion, which leads to stripe wear.

If a humeral prosthesis is placed too proud, it leads to over-tensioning of the rotator cuff and severe subacromial impingement. The correct height is typically achieved by aligning the top of the prosthetic head 5-8 mm above the superior tip of the greater tuberosity.

The absolute indication for surgical fixation of a posterior wall acetabular fracture is hip joint instability. While fragment size greater than 20-50% suggests instability, dynamic fluoroscopic stress testing under anesthesia is the most accurate and definitive method to determine the need for surgery.

Patients with a stiff lumbar spine fail to adequately increase pelvic retroversion when transitioning from standing to sitting, which limits anterior clearance and increases the risk of posterior dislocation. To compensate, the acetabular cup should be placed in increased anteversion and inclination.

The axillary nerve courses horizontally across the deep surface of the deltoid approximately 5 to 7 cm distal to the lateral edge of the acromion. It serves as the definitive distal limit when performing a deltoid-splitting approach to avoid denervating the anterior portion of the deltoid.

The sciatic nerve is at high risk during the Kocher-Langenbeck approach, primarily due to retractor compression. The peroneal division is anatomically lateral, has less supportive connective tissue, and is tethered at the fibular head, making it significantly more susceptible to stretch and compression injuries.

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. It has been shown to be a highly specific and sensitive synovial fluid biomarker for diagnosing periprosthetic joint infection, particularly in cases with borderline traditional inflammatory markers.

The patient exhibits a sensory deficit in the regimental badge area, indicating an axillary nerve injury, which is common in anterior fracture-dislocations. The axillary nerve originates from the posterior cord and receives its primary sensory and motor fibers from the C5 and C6 nerve roots, with C5 being the predominant sensory contributor to this area.

The ilioinguinal approach utilizes three surgical windows. The middle window is bounded laterally by the iliopsoas muscle (and accompanying femoral nerve) and medially by the external iliac vessels, providing excellent access to the pelvic brim and quadrilateral plate.

According to Hertel's criteria, the disruption of the medial hinge (displacement > 2 mm) and a short calcar segment attached to the articular fragment (< 8 mm metaphyseal extension) are highly predictive of humeral head ischemia.

The iliopectineal line represents the anterior column of the acetabulum on an AP pelvic radiograph. Disruption of this line indicates a fracture involving the anterior column.

The direct anterior approach utilizes the Smith-Petersen interval. Superficially, this is between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve).

The "spur sign" on an obturator oblique view is pathognomonic for an associated both-column acetabular fracture. It represents the lowest piece of the intact ilium that remains solidly attached to the axial skeleton.

Reverse total shoulder arthroplasty is indicated for elderly patients with complex 4-part proximal humerus fractures and poor bone stock. It bypasses the need for tuberosity healing to achieve active forward elevation by relying on the deltoid.

Increasing femoral offset lengthens the abductor moment arm, which subsequently decreases the necessary abductor muscle force required to level the pelvis. This effectively decreases the overall joint reactive force but increases the varus torque on the stem.

The sciatic nerve passes posterior to the hip joint. Maintaining the hip in extension and the knee in flexion relaxes the nerve, reducing the risk of iatrogenic traction injury during a posterior approach.

Large diameter metal heads (>36 mm) increase the frictional torque at the modular head-neck junction. This leads to micromotion, trunnion wear, and mechanically assisted crevice corrosion, potentially causing an adverse local tissue reaction (ALTR).

The patient has an axillary nerve injury, the most common neurologic complication of proximal humerus fractures. The axillary nerve exits the axilla through the quadrangular space alongside the posterior humeral circumflex artery.

A transverse acetabular fracture crosses the acetabulum horizontally, dividing the innominate bone into upper and lower halves. Consequently, it involves and disrupts both the anterior (iliopectineal line) and posterior (ilioischial line) columns.

Squeaking in ceramic-on-ceramic hips is primarily associated with component malpositioning (e.g., steep acetabular cup inclination or excessive version), which leads to loss of fluid film lubrication and subsequent edge loading and stripe wear.

The most common hardware-related complication of locked plating in the proximal humerus is primary or secondary intra-articular screw penetration. Dynamic fluoroscopy through a full range of motion is critical to detect unrecognized primary screw penetration.

The corona mortis is a vascular anastomosis between the external iliac (or inferior epigastric) and obturator vessels. It typically crosses the superior pubic ramus approximately 4 to 6 cm lateral to the pubic symphysis.

This is a Vancouver B2 periprosthetic fracture, characterized by a fracture around the stem with a loose implant but adequate bone stock. The standard of care is revision arthroplasty using a long, uncemented diaphyseal-fitting stem that bypasses the fracture.

The superior border of the pectoralis major insertion is a highly reliable anatomic landmark in complex proximal humerus fractures. It is located approximately 5.6 cm distal to the superior aspect of the articular surface of the humeral head.

This fracture pattern represents an associated posterior column and posterior wall fracture. The Kocher-Langenbeck approach provides excellent, direct visualization of the entire posterior column and posterior wall for definitive reduction and fixation.

Dual mobility components utilize a smaller inner head articulated within a large mobile polyethylene liner. This design maximizes the effective head size, thereby significantly increasing the functional jump distance and head-to-neck ratio, effectively reducing dislocation risk.

Hertel's criteria identify metaphyseal head extension (calcar length) < 8 mm, disruption of the medial hinge > 2 mm, and a basicervical fracture pattern as strong predictors of humeral head ischemia. A short calcar segment indicates loss of crucial blood supply from the ascending branch of the anterior humeral circumflex artery.

The corona mortis is a vascular anastomosis between the external iliac or inferior epigastric system and the obturator system. It is classically located 3 to 5 cm from the pubic symphysis and is at high risk during dissection over the superior pubic ramus.

Macrophages phagocytose polyethylene wear debris, initiating a foreign-body inflammatory response. They release cytokines such as TNF-alpha, IL-1, and IL-6, which subsequently stimulate osteoclast-mediated bone resorption.

Intra-articular screw penetration is the most common complication following locked plating of proximal humerus fractures, often due to settling of the fracture or unrecognized penetration during surgery. It rapidly leads to secondary glenoid cartilage destruction if not promptly addressed.

The iliac oblique view primarily profiles the posterior column and the anterior wall of the acetabulum. Conversely, the obturator oblique view best demonstrates the anterior column and the posterior wall.

This is a Vancouver B2 fracture (fracture around the stem, loose stem, adequate bone stock). The standard of care for B2 fractures is revision to a longer stem that bypasses the fracture, typically using a fully porous-coated or fluted tapered modular stem.

Increasing femoral offset increases the abductor moment arm, which improves abductor muscle efficiency and decreases the overall joint reaction force. This enhances joint stability and helps prevent a Trendelenburg gait.

The "spur sign" seen on an obturator oblique view represents the intact portion of the ilium that remains attached to the axial skeleton while the acetabular articular surface is displaced medially. It is pathognomonic for a both-column acetabular fracture.

Reverse total shoulder arthroplasty (RTSA) is the treatment of choice for elderly patients with complex three- or four-part proximal humerus fractures and poor bone quality. RTSA provides more reliable pain relief and functional overhead elevation compared to hemiarthroplasty, which depends heavily on tuberosity healing.

The peroneal (fibular) division of the sciatic nerve is injured in up to 80% of traumatic sciatic nerve palsies associated with posterior hip dislocations. It is more susceptible because it is tethered at the fibular head and lies lateral and posterior within the sciatic notch, directly in the path of the displaced femoral head.

Squeaking is a well-documented complication unique to ceramic-on-ceramic total hip arthroplasty bearings. It is thought to result from edge loading, microseparation, or stripe wear, leading to resonance within the component materials.

Loss of the medial hinge leads to varus collapse of the humeral head and subsequent screw cut-out. Adding an intramedullary fibular strut allograft acts as a mechanical buttress, restoring medial cortical support and significantly increasing the load-to-failure of the construct.

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-polyethylene THA with large metal heads are typically caused by trunnionosis. This is mechanically assisted crevice corrosion at the modular head-neck (trunnion) junction.

Marginal impaction refers to articular segments that are driven into the underlying cancellous bone. To restore joint congruity and prevent post-traumatic osteoarthritis, these fragments must be meticulously elevated and the resulting void filled with bone graft.

The lateral femoral cutaneous nerve (LFCN) is a purely sensory nerve at high risk during the superficial dissection of the direct anterior approach to the hip. Injury results in meralgia paresthetica, presenting as numbness or burning over the anterolateral thigh.

The Neer classification defines a "part" only if the fragment is displaced > 1 cm or angulated > 45 degrees. Since the greater tuberosity is displaced only 8 mm, it is not considered a separate part; thus, this is a two-part surgical neck fracture.