ABOS Board Review: SCFE, Köhler's Disease, Dermatomyositis, & Sprengel's Deformity | Part 32

Correct Answer: B

Rationale: Ewing's sarcoma most commonly presents in the first three decades of life, making it primarily a tumor of children, adolescents, and young adults. It is relatively rare in infants or older adults.

Correct Answer: C

Rationale: By definition, Ewing's sarcoma is considered a high-grade malignant lesion, reflecting its aggressive biological behavior and propensity for metastasis. It is never considered benign or low-grade.

Correct Answer: A

Rationale: The clinical presentation of an obese adolescent male with hip or knee pain, a limp, limited internal rotation, and obligate external rotation with hip flexion is classic for Slipped Capital Femoral Epiphysis. The radiographic findings of physeal widening and posterior/inferior displacement of the epiphysis confirm the diagnosis. Main Distractor: Legg-Calve-Perthes Disease typically affects younger, often thinner, children (4-8 years old) and presents with different radiographic findings (avascular necrosis of the femoral head).

Correct Answer: A

Rationale: The frog-leg lateral view is the most critical additional radiographic projection for diagnosing Slipped Capital Femoral Epiphysis when the AP view is equivocal. It best visualizes the characteristic posterior and inferior displacement of the femoral epiphysis relative to the metaphysis. Main Distractor: While a CT scan or MRI can confirm the diagnosis, they are not typically the initial or most critical *radiographic* view for diagnosis after an equivocal AP film. An oblique view is less specific than a frog-leg lateral for visualizing the slip.

Correct Answer: A

Rationale: Klein's line is a key radiographic sign for diagnosing Slipped Capital Femoral Epiphysis on an AP radiograph. A line drawn along the superior border of the femoral neck should normally intersect a portion of the femoral head. In SCFE, due to the posterior and inferior displacement of the epiphysis, this line will fail to intersect the lateral portion of the femoral head, or will intersect a smaller portion than on the contralateral side. Main Distractor: Widening of the physis can be an early sign of SCFE, but Klein's line is a more specific and quantifiable diagnostic criterion for the actual slip.

Correct Answer: A

Rationale: Slipped Capital Femoral Epiphysis is classified as "unstable" if the patient is unable to bear weight on the affected extremity, even with crutches. This classification is crucial as unstable slips have a significantly higher risk of complications, particularly avascular necrosis. Main Distractor: A "stable" slip is defined by the patient's ability to bear weight on the affected extremity, with or without crutches.

Correct Answer: A

Rationale: The primary pathophysiological mechanism of Slipped Capital Femoral Epiphysis involves a weakening of the hypertrophic zone of the physeal plate, often during periods of rapid growth, combined with increased shear stress across the physis. This shear stress is exacerbated by factors like obesity and the biomechanics of the hip joint. Main Distractor: Avascular necrosis of the femoral head is a serious complication of SCFE, especially unstable slips, but it is not the primary cause of the slip itself.

Correct Answer: A

Rationale: While obesity is the most common risk factor, endocrine disorders are important to consider, especially in atypical presentations of SCFE (e.g., younger age, non-obese, or bilateral slips). Hypothyroidism and growth hormone deficiency are the most commonly associated endocrine conditions that can weaken the physis and predispose to SCFE. Main Distractor: Growth hormone deficiency is also a known risk factor, but hypothyroidism is frequently cited as the most common endocrine abnormality associated with SCFE.

Correct Answer: A

Rationale: For stable Slipped Capital Femoral Epiphysis, the gold standard of treatment is in situ pinning with a single cannulated screw. This procedure stabilizes the epiphysis, prevents further slippage, and promotes physeal closure, with minimal risk of avascular necrosis. Main Distractor: Open reduction and internal fixation is a more invasive procedure with higher risks, typically reserved for severe or unstable slips, or for addressing complications like femoroacetabular impingement after physeal closure.

Correct Answer: A

Rationale: For unstable Slipped Capital Femoral Epiphysis, the immediate management involves gentle closed reduction (often with a single maneuver) to improve alignment and reduce the risk of avascular necrosis, followed by immediate in situ pinning. Aggressive reduction maneuvers should be avoided due to the high risk of further vascular compromise. Main Distractor: Immediate open reduction and internal fixation is generally avoided for acute unstable slips due to increased morbidity and risk of avascular necrosis compared to gentle closed reduction and pinning.

Correct Answer: A

Rationale: Avascular necrosis (AVN) of the femoral head is the most serious and common complication specifically associated with unstable Slipped Capital Femoral Epiphysis. The vascular supply to the femoral head can be compromised during the initial slip, during reduction attempts, or due to the instability itself, leading to AVN. Main Distractor: Chondrolysis is another potential complication, but AVN is more directly and frequently linked to the instability of the slip and its acute management.

Correct Answer: A

Rationale: The risk of a contralateral Slipped Capital Femoral Epiphysis developing in patients with a unilateral slip is significant, ranging from 20-6

Correct Answer: D

Rationale: For stable SCFE, the standard of care is immediate in situ percutaneous screw fixation to prevent further slippage and promote physeal closure. This minimizes the risk of avascular necrosis and chondrolysis associated with unstable slips or more invasive procedures. Observation is inappropriate as the slip can progress. Open reduction is generally reserved for severe, unstable slips or complications, and carries higher risks. Spica cast or traction are not definitive treatments for SCFE.

Correct Answer: B

Rationale: For unstable SCFE, the primary goal is immediate in situ screw fixation without attempting reduction. Reduction maneuvers, especially forceful ones, significantly increase the risk of avascular necrosis (AVN) due to disruption of the blood supply to the femoral head. Gentle reduction attempts are sometimes considered for very severe slips but are controversial and carry risks. Spica cast, traction, or open reduction are not the immediate primary management for an unstable slip.

Correct Answer: D

Rationale: While avascular necrosis and chondrolysis are serious complications, they are more common with unstable slips or aggressive reduction attempts. For stable SCFE treated with in situ pinning, the most common long-term complication is femoroacetabular impingement (FAI) due to the residual deformity of the femoral head-neck junction. This can lead to labral tears and early osteoarthritis. Contralateral SCFE is a common occurrence (up to 60%) but is a new slip, not a complication of the initial treatment itself. Nonunion is rare.

Correct Answer: A

Rationale: Hypothyroidism is the most commonly recognized endocrine disorder associated with SCFE, particularly in younger or unusually short children. Other endocrine abnormalities like growth hormone deficiency, panhypopituitarism, and renal osteodystrophy can also predispose to SCFE, but hypothyroidism is the most frequent. Diabetes mellitus, hyperparathyroidism, and adrenal insufficiency are less commonly linked.

Correct Answer: D

Rationale: The incidence of contralateral SCFE is significant, ranging from 30% to 60% in various studies, particularly in younger patients, those with endocrine abnormalities, or significant obesity. This high incidence is a major factor in the ongoing debate regarding prophylactic pinning of the contralateral hip, especially in high-risk groups. Therefore, options A, B, C, and E are too low or too high.

Correct Answer: B

Rationale: The frog-leg lateral view is generally considered the most sensitive radiographic view for detecting a subtle SCFE because it best visualizes the posterior and inferior displacement of the epiphysis relative to the metaphysis. The AP view is also essential but may miss subtle slips. The cross-table lateral is crucial for unstable slips where frog-leg positioning is painful or contraindicated. Oblique and false profile views are less commonly used for primary SCFE diagnosis.

Correct Answer: C

Rationale: The Southwick classification for SCFE severity is based on the epiphyseal-shaft angle on the lateral radiograph: * Mild: < 30 degrees * Moderate: 30-50 degrees * Severe: > 50 degrees A slip angle of 45 degrees falls into the moderate category. The question states the slip angle is 45 degrees, which is moderate. However, the provided options are A, B, C, D, E. Let's re-evaluate the Southwick classification. Standard Southwick classification: Mild: < 30 degrees Moderate: 30-60 degrees Severe: > 60 degrees If the question intends to use a slightly different cutoff, or if I misremembered, let's check. Commonly, some sources use: Mild: < 30 degrees Moderate: 30-50 degrees Severe: > 50 degrees Given the options, and 45 degrees, if using the 30-50 range for moderate, then B would be correct. If using 30-60 for moderate, then B would be correct. Let's assume the more common 30-50 for moderate. A 45-degree slip is considered moderate. Let me re-read the question and options carefully. "The slip angle on the lateral radiograph is measured at 45 degrees. According to the Southwick classification, how would this slip be categorized?" Options: A) Mild, B) Moderate, C) Severe, D) Critical, E) Unstable. If 45 degrees is moderate, then B is the correct answer. Let's double-check the Southwick classification. Mild: < 30 degrees Moderate: 30-50 degrees Severe: > 50 degrees This is the most widely accepted version. Therefore, 45 degrees is Moderate. Let's assume there was a typo in my initial thought process and the correct answer is B. Correct Answer: B Rationale: The Southwick classification for SCFE severity is based on the epiphyseal-shaft angle on the lateral radiograph: Mild (<30 degrees), Moderate (30-50 degrees), and Severe (>50 degrees). A slip angle of 45 degrees falls into the moderate category. Unstable refers to the patient's ability to bear weight, not the degree of slip.

Correct Answer: C

Rationale: The primary mechanism of SCFE is mechanical shear stress acting across a weakened physis (growth plate). Factors like rapid growth, obesity, and hormonal imbalances (e.g., hypothyroidism) contribute to physeal weakening, making it susceptible to slippage. It is not primarily a traumatic avulsion, ischemic necrosis, inflammatory process, or congenital malformation, although trauma can precipitate symptoms in an already weakened physis.

Correct Answer: C

Rationale: Klein's line (also known as the Klein's method or Klein's line sign) is used to assess for SCFE on an AP pelvis radiograph. A line is drawn along the superior border of the femoral neck. Normally, this line should intersect a portion of the femoral head. In SCFE, due to posterior and inferior displacement, the line will fail to intersect the femoral head or will intersect a smaller portion. Shenton's line assesses for hip dislocation or fracture. Perkin's line and Hilgenreiner's line are used for developmental dysplasia of the hip. Wiberg's CE angle assesses acetabular coverage.

Correct Answer: B

Rationale: The description of severe pain, stiffness, loss of motion, and joint space narrowing, particularly in the absence of signs of infection or AVN (which typically presents with collapse of the femoral head), is highly suggestive of chondrolysis. Chondrolysis is a rare but devastating complication characterized by rapid destruction of articular cartilage. While AVN is a concern, its radiographic presentation is different (sclerosis, collapse). Infection would typically present with systemic signs and purulent drainage. Hardware failure would not explain joint space narrowing. Contralateral SCFE is a new slip, not a complication of the treated hip.

Correct Answer: C

Rationale: The most significant and feared complication of forceful closed reduction attempts in unstable SCFE is avascular necrosis (AVN) of the femoral head. The blood supply to the femoral head, particularly the lateral epiphyseal vessels, is vulnerable to disruption during reduction maneuvers, especially in an acutely displaced epiphysis. Nonunion and premature physeal closure are less immediate risks. FAI is a long-term consequence of residual deformity, not a direct risk of reduction. Contralateral SCFE is a separate event.

Correct Answer: A

Rationale: For stable SCFE, a single cannulated screw placed centrally in the femoral head, perpendicular to the physis, is the standard and generally sufficient method of fixation. It provides adequate stability to prevent further slippage and allows for physeal closure. Multiple screws or plates are typically not necessary for stable slips and may increase the risk of complications like chondrolysis or hardware prominence. Two screws may be considered in some cases, but one is the most common and effective.

Correct Answer: B

Rationale: For severe, chronic SCFE with significant deformity and impingement, in situ pinning alone will not correct the deformity and will likely lead to persistent FAI and early osteoarthritis. A subcapital osteotomy, such as the modified Dunn procedure, is designed to anatomically reduce the slipped epiphysis and correct the deformity, thereby improving range of motion and preventing FAI. Intertrochanteric or valgus osteotomies are less effective at correcting the specific deformity at the femoral head-neck junction. Hip arthroscopy addresses secondary impingement but not the underlying bony deformity.

Correct Answer: C

Rationale: The primary reason for considering prophylactic pinning of the contralateral hip is the high incidence of a subsequent slip in the asymptomatic hip, which can be as high as 30-60%. Prophylactic pinning aims to prevent a potentially unstable and more morbid contralateral slip. It is not done to prevent AVN (which is a risk of the slip itself or its treatment), correct pre-existing deformity (unless a subtle slip is already present), facilitate earlier return to sports, or prevent chondrolysis.

Correct Answer: C

Rationale: Slipped Capital Femoral Epiphysis typically occurs during periods of rapid growth, usually in pre-adolescent and adolescent children. The most common age range for presentation is between 8 and 15 years, with a peak incidence around 12-14 years for boys and 10-12 years for girls. Presentation outside this range, especially in younger children, should prompt investigation for underlying endocrine disorders.

Correct Answer: D

Rationale: The single most important factor associated with an increased risk of avascular necrosis (AVN) of the femoral head in SCFE is the instability of the slip (inability to bear weight). Unstable slips have a significantly higher rate of AVN (up to 50%) compared to stable slips (<5%). This is due to the greater disruption of the blood supply to the epiphysis during the initial slip or during any reduction attempts. While age, obesity, endocrine disorders, and duration of symptoms are risk factors for developing SCFE, they are not as directly linked to AVN risk as instability.

Correct Answer: C

Rationale: The most common cause of long-term morbidity in patients treated for SCFE is early onset osteoarthritis, primarily due to residual deformity leading to femoroacetabular impingement (FAI) and subsequent articular cartilage damage. While hardware irritation, recurrence (if not adequately fixed), and leg length discrepancy can occur, FAI and subsequent osteoarthritis are the predominant long-term issues. Chronic infection is rare.

Correct Answer: C

Rationale: This patient presents with an acute exacerbation (2-day history, inability to bear weight) on a hip that already had a chronic slip (history of chronic left hip pain for 3 months). The classification of SCFE based on duration of symptoms is: Acute (<3 weeks), Chronic (>3 weeks), and Acute-on-chronic (acute exacerbation of symptoms on a pre-existing chronic slip). The right hip is an acute-on-chronic slip, while the left is a chronic stable slip. The question asks about "this presentation" which implies the overall picture or the acute event. The most precise classification for the acutely symptomatic hip is acute-on-chronic. While it is also an unstable slip, "acute-on-chronic" describes the temporal nature of the slip more completely in this context.

Correct Answer: C

Rationale: Intra-articular screw penetration is the most common complication of screw placement during in situ fixation of SCFE. This can lead to significant pain, chondrolysis, and early osteoarthritis. Careful fluoroscopic guidance in multiple planes (AP and lateral) is crucial to ensure the screw remains entirely within the epiphysis and does not violate the articular cartilage. While AVN and chondrolysis can occur, direct screw penetration is a more frequent iatrogenic complication of the surgical technique itself. Infection and fracture are less common.

Correct Answer: C

Rationale: The clinical presentation of a 7-year-old boy with a painful limp, tenderness over the medial midfoot, and radiographic findings of fragmentation and sclerosis of the navicular bone is classic for Köhler's disease I, which is avascular necrosis of the navicular bone. Sever's disease (calcaneal apophysitis) affects the heel, and Freiberg's infraction affects the metatarsal heads. Tarsal coalition is a congenital fusion and typically presents with rigid flatfoot and pain, but the radiographic findings described are not consistent. Calcaneal apophysitis is another name for Sever's disease.

Correct Answer: C

Rationale: Köhler's disease I is specifically defined as the avascular necrosis of the navicular bone. The clinical symptoms of antalgic limp and local tenderness of the medial aspect of the foot over the navicular are direct consequences of this condition. Avascular necrosis of other tarsal bones would present differently and are distinct conditions.

Correct Answer: C

Rationale: The etiology of Köhler's disease I is unknown, but the text explicitly states that a vascular incident and a retarded bone age have been implicated. These factors contribute to the susceptibility of the navicular bone to ischemia. While repetitive microtrauma can exacerbate symptoms, it is not considered a primary etiological factor in the same way as vascular compromise. Genetic, nutritional, or infectious causes are not supported by the provided text.

Correct Answer: C

Rationale: The text states that the navicular bone might be compressed between the already ossified talus and cuneiforms, especially when the child becomes heavier. This compression involves the vessels in the central spongy bone, leading to ischemia, which is the underlying cause of avascular necrosis and subsequent fragmentation. While trauma can occur, the primary mechanism described for Köhler's disease is compression-induced ischemia, not a direct traumatic fracture. Chronic inflammation, congenital malformation, or systemic metabolic disease are not the described pathophysiology.

Correct Answer: C

Rationale: The provided text explicitly states that "the navicular is the last tarsal bone to ossify in children." This delayed ossification is implicated in its susceptibility to compression and ischemia, making it a key factor in the pathophysiology of Köhler's disease I. The other options are incorrect based on the provided information.

Correct Answer: B

Rationale: The clinical context for Fig. 13.23 states, "The child can walk with an increased weight on the lateral side of the foot." This is a common compensatory mechanism to offload the painful medial aspect of the foot where the navicular is located. An antalgic limp is a general term for a painful gait, and shifting weight laterally helps reduce pressure on the affected bone.

Correct Answer: B

Rationale: The text explicitly states, "Navicular bone might be compressed between the already ossified talus and the cuneiforms when the child becomes heavier." This compression is crucial to the pathophysiology of ischemia in Köhler's disease I. The other options involve bones that are not directly implicated in this specific compression mechanism as described.

Correct Answer: C

Rationale: The demonstration of "a complete rebuilding of the navicular bone" seven years later strongly indicates that Köhler's disease I is a self-limiting condition with a favorable prognosis, often resolving without aggressive intervention. It is not progressive, degenerative, or typically associated with long-term impairment or infection. The text does not mention surgical intervention as a typical requirement.

Correct Answer: B

Rationale: The text states, "girls with Köhler’s disease I often are younger than boys" and attributes this to "the ossification onset." Girls generally have an earlier skeletal maturation and ossification onset compared to boys, which can influence the timing of presentation for conditions related to bone development. The other options are not supported by the provided text.

Correct Answer: B

Rationale: The text explains that "Compression involves the vessels in central spongy bone leading to ischemia." This specific mechanism of vessel compression within the navicular bone itself, rather than a generalized vascular issue or external trauma, is the core of the pathophysiology. The other options describe different types of vascular problems not specific to Köhler's disease I as described.

Correct Answer: B

Rationale: The text explicitly states, "This disease occurs in children aged 5–10 years." This age range is a key diagnostic criterion for Köhler's disease I. The other age ranges are incorrect for this specific condition.

Correct Answer: C

Rationale: The clinical context for Fig. 13.23 explicitly states, "Note the fragmentation of navicular bone on right side, especially in lateral view." This fragmentation, often accompanied by sclerosis (increased density), is the hallmark radiographic finding of avascular necrosis of the navicular in Köhler's disease I. While there might be some density changes, fragmentation is the most characteristic feature. The other options describe findings not typical of Köhler's disease I.

Correct Answer: C

Rationale: The text and Fig. 13.23c clearly demonstrate that "a complete rebuilding of the navicular bone is demonstrated on radiograph" at age 13, seven years after initial presentation. This indicates a very favorable prognosis with complete resolution of the bone architecture, implying that it is a self-limiting condition with excellent long-term outcomes without permanent deformity or chronic arthritis. The other options describe negative outcomes not supported by the provided information.

Correct Answer: C

Rationale: The clinical context for Fig. 13.22 explicitly states, "Ischemia causes clinical symptoms, like antalgic limp and local tenderness of the medial aspect of the foot over the navicular." These are the defining clinical features of Köhler's disease I. While pain can be severe, inability to bear weight is not universally true, and systemic symptoms, swelling, or neurological deficits are not typical for this condition.

Correct Answer: C

Rationale: The text states, "Navicular bone might be compressed between the already ossified talus and the cuneiforms when the child becomes heavier." Increased weight places greater compressive forces on the foot, thereby increasing the likelihood of vascular compromise to the navicular. The other options are not directly implicated in the compression mechanism described.

Correct Answer: C

Rationale: The text states that Köhler's disease I "is more common in boys." While girls can be affected, and often at a younger age, the overall incidence is higher in boys. It is a rare disease, but its prevalence difference between genders is noted.

Correct Answer: C

Rationale: The text and Fig. 13.23c clearly illustrate that "a complete rebuilding of the navicular bone is demonstrated on radiograph" at age 13. This indicates that the bone undergoes revascularization and remodeling, leading to a normal or near-normal appearance and function. The other options describe negative or persistent pathological outcomes that are not typical for Köhler's disease I.

Correct Answer: C

Rationale: The clinical context for Fig. 13.23 states, "Note the fragmentation of navicular bone on right side, especially in lateral view." While fragmentation may be visible on AP views, the lateral view is specifically mentioned as being particularly good for demonstrating this characteristic finding. The other views are not highlighted for this specific purpose in the provided text.

Correct Answer: D

Rationale: The text states that "the etiology is unknown, but the vascular incident and a retarded bone age have been implicated." It further explains that "Compression involves the vessels in central spongy bone leading to ischemia." Genetic predisposition is not mentioned as an implicated factor in the provided text. While compression and ischemia are part of the pathophysiology, the initial "etiology" refers to the underlying cause leading to this susceptibility.

Correct Answer: B

Rationale: This option accurately synthesizes several key facts from the provided text: Köhler's disease I is "the rare avascular necrosis of the navicular bone," it "occurs in children aged 5–10 years," and the long-term radiographic findings (Fig. 13.23c) demonstrate "a complete rebuilding," indicating spontaneous resolution. The other options contain inaccuracies regarding the nature, age group, or prognosis of the disease.

Correct Answer: C

Rationale: Köhler’s disease I is explicitly defined as the rare avascular necrosis of the navicular bone. The clinical presentation and radiographic findings are consistent with this pathological process. Main Distractor: B) Traumatic fracture. While fragmentation is seen, the underlying process is avascular necrosis, not a direct traumatic fracture, although compression is implicated in the etiology.

Correct Answer: D

Rationale: The teaching case explicitly states that Köhler’s disease I is the avascular necrosis of the navicular bone. Main Distractor: A) Talus. While the talus is an adjacent bone, it is not the primary bone affected by avascular necrosis in Köhler's disease I.

Correct Answer: B

Rationale: The text states that Köhler’s disease I "occurs in children aged 5–10 years." Main Distractor: C) 11-14 years. This age range is typically beyond the common presentation window for Köhler's disease I.

Correct Answer: C

Rationale: The text states, "This disease occurs in children aged 5–10 years and is more common in boys, but because of the ossifi cation onset, girls with Köhler’s disease I oft en are younger than boys." Main Distractor: A) It is more common in girls than boys. This statement contradicts the provided information that it is more common in boys.

Correct Answer: C

Rationale: The text explains, "Navicular bone might be compressed between the already ossifi ed talus and the cuneiforms when the child becomes heavier. Compression involves the vessels in central spongy bone leading to ischemia." Main Distractor: A) Direct trauma leading to a primary fracture. While fragmentation is seen, the underlying cause is ischemia due to compression, not a direct traumatic fracture.

Correct Answer: C

Rationale: The text explicitly states, "Ischemia causes clinical symptoms, like antalgic limp and local tenderness of the medial aspect of the foot over the navicular." Main Distractor: A) Trendelenburg limp. A Trendelenburg limp is associated with hip abductor weakness, which is not described as a symptom of Köhler's disease I.

Correct Answer: C

Rationale: The text states, "Ischemia causes clinical symptoms, like antalgic limp and local tenderness of the medial aspect of the foot over the navicular." Main Distractor: E) Dorsum of the foot over the cuneiforms. While the cuneiforms are adjacent, the navicular is the primary affected bone and the site of tenderness.

Correct Answer: C

Rationale: Fig. 13.23 a–c states, "Note the fragmentation of navicular bone on right side, especially in lateral view." This is the hallmark radiographic finding in the acute phase. Main Distractor: B) Sclerosis of the talus. While sclerosis of the navicular can occur, sclerosis of the talus is not a characteristic finding of Köhler's disease I.

Correct Answer: B

Rationale: Fig. 13.23 a–c explicitly states, "Seven years later at age 13 a complete rebuilding of the navicular bone is demonstrated on radiograph (c)." This indicates the self-limiting and reconstructive nature of the disease. Main Distractor: A) Persistent fragmentation and collapse of the navicular. This describes the acute phase, not the typical healed phase of Köhler's disease I.

Correct Answer: B

Rationale: The text states, "The child can walk with an increased weight on the lateral side of the foot." This is a compensatory mechanism to offload the painful medial aspect of the foot. Main Distractor: C) By increasing weight on the medial side of the foot. This would exacerbate the pain over the affected navicular bone.

Correct Answer: B

Rationale: The text states, "as the navicular is the last tarsal bone to ossify in children." This delayed ossification is implicated in its vulnerability to compression and ischemia. Main Distractor: A) It is the first tarsal bone to ossify. This is the opposite of what is stated in the text.

Correct Answer: C

Rationale: The text states, "Compression involves the vessels in central spongy bone leading to ischemia." This is the direct link between mechanical compression and the avascular necrosis. Main Distractor: A) Compression directly causes a fracture of the navicular. While fragmentation is seen, it is a consequence of avascular necrosis, not a direct traumatic fracture from compression.

Correct Answer: C

Rationale: The term "avascular necrosis" literally means death of tissue due to a lack of blood supply (a-vascular). Main Distractor: A) Nerve supply. While nerve supply is crucial for sensation, "avascular" specifically refers to the absence of blood vessels, not nerves.

Correct Answer: B

Rationale: The provided text describes dermatomyositis as a "systemic immune disorder, a primary inflammatory myopathy with autoimmune pathogenesis." This directly aligns with option B. Option A is incorrect because while it is autoimmune, "localized vasculitis" does not fully characterize the systemic inflammatory myopathy described.

Correct Answer: C

Rationale: The text states that dermatomyositis is associated with "substantial muscle weakening in its course, especially proximally in the extremities." This directly supports option C. Option A is incorrect as distal muscle weakness is not the characteristic pattern described for dermatomyositis.

Correct Answer: C

Rationale: The clinical context explicitly states, "Women are affected twice more than men." Therefore, option C is the correct answer. Option B is incorrect as it presents the inverse of the stated gender prevalence.

Correct Answer: D

Rationale: The text indicates, "First skin signs can appear during childhood as well as in adults." This makes option D the correct answer. Option A is incorrect because the text explicitly mentions childhood onset of skin signs.

Correct Answer: B

Rationale: The text states, "In 7–66% of cases of adult dermatomyositis, different malignant tumors can develop." This highlights the strong association with malignancy in adults, making option B correct. Option C, while a common concern in elderly females, is not specifically listed as a direct comorbidity of adult dermatomyositis in the provided text.

Correct Answer: B

Rationale: Figure 12.18b explicitly describes "heliotrope rush and heliotrope edema of the eyelids." This characteristic purplish discoloration and swelling is a hallmark of dermatomyositis. Option A, malar rash, is typically associated with systemic lupus erythematosus and is not the specific term used for the eyelid finding in this context.

Correct Answer: C

Rationale: Figure 12.19 clearly labels the depicted lesions as "Gottron’s papules over the metacarpophalangeal joints (violet-colored skin pigmentation on the extensor surface of small joints)." Option D, Mechanic's hands, is another skin finding in myositis but is not the specific term used to describe the lesions shown in the image or the primary characteristic finding on the MCP joints.

Correct Answer: B

Rationale: The description for Figure 12.19 states that Gottron's papules are "often complicated with cutaneous ulcers and poor wound closure or poor healing." This directly supports option B. While other skin changes can occur, cutaneous ulcers and poor healing are specifically mentioned as common complications of Gottron's papules.

Correct Answer: C

Rationale: Figure 12.20a, b describes "Calcareous deposits in subcutis of an 8-year-old boy in anteroposterior (a) and lateral (b) radiograph." The text further links this to "severe and debilitating calcinosis." Therefore, option C is the correct term. Option B, heterotopic ossification, is a broader term for bone formation in soft tissue, but "calcinosis" is the specific term used in the context of dermatomyositis for these deposits.

Correct Answer: C

Rationale: The text states that "severe and debilitating calcinosis can be observed because of calcification of muscles with contractures." This directly explains the musculoskeletal complication of extensive calcinosis, making option C correct. Option A, pathological fractures, is not specifically mentioned as a direct consequence of calcinosis in the provided text.

Correct Answer: C

Rationale: The text lists "pulmonary fibrosis" as one of the "other extraskeletal differences" associated with dermatomyositis. This aligns with the patient's symptoms of progressive shortness of breath and cough. Option D, pleural effusion, is not specifically mentioned as an extraskeletal manifestation in the provided text.

Correct Answer: A

Rationale: The clinical context explicitly lists myocarditis as one of the extraskeletal differences associated with dermatomyositis. Other cardiac manifestations include conduction abnormalities, arrhythmias, coronary artery disease, and pericarditis. Aortic stenosis, mitral valve prolapse, atrial fibrillation, and ventricular septal defect are not specifically highlighted as direct associations in the provided text, although arrhythmias (D) are mentioned, myocarditis (A) is a more direct and severe cardiac involvement listed.

Correct Answer: A

Rationale: Pulmonary fibrosis is explicitly listed as an extraskeletal difference associated with dermatomyositis. The symptoms of shortness of breath and dry cough, along with restrictive lung disease, are consistent with pulmonary fibrosis. Asthma, bronchiectasis, emphysema, and pleural effusion are not specifically mentioned as direct associations in the provided text.

Correct Answer: A

Rationale: Dysphagia is specifically listed as an extraskeletal difference associated with dermatomyositis. Difficulty swallowing is a common and significant complication. Gastric ulcer, cholecystitis, pancreatitis, and diverticulitis are not mentioned as direct associations in the provided text.

Correct Answer: A

Rationale: Retinopathy is explicitly listed as an extraskeletal difference associated with dermatomyositis. The reported visual changes are consistent with retinal involvement. Cataracts, glaucoma, optic neuritis, and conjunctivitis are not specifically mentioned as direct associations in the provided text.

Correct Answer: A

Rationale: The clinical context states that dermatomyositis is associated with "substantial muscle weakening in its course, especially proximally in the extremities." It also mentions "symmetrical, proximal muscle weakness" in the context of calcinosis, reinforcing this pattern. Therefore, the weakness is typically symmetrical and proximal. Asymmetrical or distal weakness is not characteristic of dermatomyositis.

Correct Answer: A

Rationale: The image description and clinical context explicitly define "Gottron’s papules over the metacarpophalangeal joints (violet-colored skin pigmentation on the extensor surface of small joints)." This is a pathognomonic skin finding for dermatomyositis. Heliotrope rash is periorbital, Shawl sign and V-sign are rashes on the upper back/shoulders and anterior chest respectively, and Mechanic's hands are rough, cracked skin on the lateral and palmar aspects of the fingers, not violet papules.

Correct Answer: A

Rationale: The clinical context for Fig. 12.19 explicitly states that Gottron's papules "It is often complicated with cutaneous ulcers and poor wound closure or poor healing." This directly matches the patient's presentation. Hyperkeratosis, psoriatic plaques, fungal infections, and contact dermatitis are not specifically mentioned as complications of Gottron's papules in the provided text.

Correct Answer: A

Rationale: The clinical context for Fig. 12.20 a, b describes "Calcareous deposits in subcutis of an 8-year-old boy." This finding is specifically referred to as calcinosis in the text, which is a known complication of dermatomyositis, particularly in children. Osteoporosis, osteomyelitis, rhabdomyolysis, and gouty tophi are distinct conditions and do not describe subcutaneous calcareous deposits in this context.

Correct Answer: A

Rationale: The clinical context for Fig. 12.20 a, b states that "severe and debilitating calcinosis can be observed because of calcification of muscles with contractures." This directly links calcinosis to the development of muscle contractures, which would explain the loss of joint range of motion. Pathological fractures, joint dislocations, ligamentous laxity, and nerve entrapment are not specifically mentioned as direct sequelae of calcinosis in the provided text.

Correct Answer: A

Rationale: The clinical context for Fig. 12.18 a, b explicitly mentions "lipodystrophy" as a finding in this patient. Lipodystrophy refers to an abnormal distribution of fat in the body. Lipoatrophy is specifically fat loss, while lipodystrophy encompasses both loss and accumulation. Lipoma, cellulitis, and panniculitis are distinct conditions not directly describing the general fat distribution changes seen in dermatomyositis.

Correct Answer: A

Rationale: The provided text explicitly states, "Women are affected twice more than men." This is a direct epidemiological fact about dermatomyositis. The other options contradict this statement.

Correct Answer: A

Rationale: The text states, "First skin signs can appear during childhood as well as in adults." This indicates that dermatomyositis can manifest cutaneously across a broad age range, including pediatric and adult populations. The other options are incorrect based on this information.

Correct Answer: A

Rationale: The introductory sentence of the text describes dermatomyositis as a "systemic immune disorder." The presence of muscle weakness, skin manifestations, and involvement of multiple organ systems (pulmonary and cardiac in this vignette) strongly supports its systemic nature. It is not merely a localized skin condition, pure muscular dystrophy, or neuropathic disorder, and it clearly has systemic involvement.

Correct Answer: A

Rationale: The text explicitly states that dermatomyositis is a "primary inflammatory myopathy." The biopsy findings of inflammatory infiltrates are consistent with this classification. Metabolic, congenital, toxic, and dystrophic myopathies represent different categories of muscle disorders with distinct underlying etiologies and pathological features.

Correct Answer: A

Rationale: The text clearly states that dermatomyositis is a "systemic immune disorder, a primary inflammatory myopathy with autoimmune pathogenesis." This directly identifies its underlying cause as autoimmune. While genetic factors may play a role in susceptibility, and infections can sometimes trigger autoimmune responses, the primary pathogenesis is autoimmune, not purely infectious, genetic, traumatic, or due to nutritional deficiency.

Correct Answer: A

Rationale: The text explicitly states, "The prevalence is 1:100,000." This is a direct factual recall from the provided information. The other options are incorrect prevalence figures.

Correct Answer: A

Rationale: The image context (Fig. 12.18 a, b) shows a "rash over the breast (a)" and "heliotrope rush and heliotrope edema of the eyelids (b)" in the same patient. While the rash over the breast is not given a specific name in the text (it's often called a V-sign or Shawl sign), the question asks for *another* characteristic skin finding. The heliotrope rash is explicitly mentioned in the same figure's context as a key feature of dermatomyositis. Psoriatic plaques, urticaria, eczema, and rosacea are not characteristic skin findings of dermatomyositis.

Correct Answer: C

Rationale: Sprengel's deformity is defined as a congenital abnormal elevation of one or both scapulas from the normal anatomic scapula position. Options A, B, D, and E describe incorrect definitions or unrelated conditions. The main distractor, E, incorrectly states scapular depression.

Correct Answer: B

Rationale: The text explicitly states that abnormal articulations of the scapula with the vertebral column are named as omovertebral bone. Options A, C, D, and E are either unrelated conditions or incorrect anatomical terms for this specific anomaly. The main distractor, D, is an associated anomaly but not the specific articulation.

Correct Answer: C

Rationale: The text lists "a defective musculature, unable to draw the scapula caudally" as a possibility for the failure of descent. It also mentions "a normal musculature, which is unable to draw the scapula caudally too." Options A, B, D, and E are not explicitly mentioned as pathogenic mechanisms for Sprengel's deformity in the provided text. The main distractor, E, describes a muscle that elevates the scapula, but the pathogenesis focuses on the inability to draw it caudally.

Correct Answer: D

Rationale: The text states, "This anomaly is often associated with other anomalies of the skeletal system and other organs." While other organs can be involved, the skeletal system is explicitly mentioned as commonly affected. Options A, B, C, and E are not specifically highlighted as commonly associated in the provided text. The main distractor, E, is not as broadly stated as the skeletal system.

Correct Answer: B

Rationale: Figure 13.3 description states, "The scapula is rotated about the sagittal axis, bringing the upper medial angle away from the spinal column and the lower angle close to it." Options A, C, D, and E describe incorrect or incomplete rotational patterns. The main distractor, A, reverses the correct description.

Correct Answer: B

Rationale: The text explicitly states, "One third of patients has omovertebral bone." Options A, C, D, and E are incorrect prevalence rates. The main distractor, C, is a common guess but incorrect based on the text.

Correct Answer: B

Rationale: The text states the omovertebral bone "most commonly the fourth to seventh cervical vertebrae (C4-C7) spinous processes, lamina, or transverse processes." Options A, C, D, and E describe incorrect vertebral levels or anatomical locations. The main distractor, A, is too high in the cervical spine.