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1. General Principles & Basic Science MCQs

Practice Set 224 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 4461

Topic: Infection, Pharmacology & VTE

The mother of a 26-month-old boy reports that he has been unwilling to bear weight on his left lower extremity since he awoke this morning. She denies any history of trauma. He has a temperature of 99.4 degrees F (37.4 degrees C), and examination reveals that abduction of the left hip is limited to 30 degrees. Laboratory studies show a WBC of 11,000/mm3 and an erythrocyte sedimentation rate of 22 mm/h. A radiograph of the pelvis is shown in Figure 13. Management should consist of

Pediatrics 2001 Practice Questions: Set 1 (Solved) - Figure 23

. aspiration of the hip.
. a bone scan.
. an MRI scan.
. bed rest, frequent temperature checks, and reevaluation in 24 to 48 hours.
. hospital admission and placement in traction.

Correct Answer & Explanation

. bed rest, frequent temperature checks, and reevaluation in 24 to 48 hours.

Explanation

The most likely diagnosis is transient synovitis. Initial management should consist of bed rest and serial observation to rule out atypical septic arthritis of the hip. In an unreliable family situation, hospitalization for bed rest and observation may be indicated. Other disorders such as proximal femoral osteomyelitis, leukemia, juvenile rheumatoid arthritis, pelvic osteomyelitis, diskitis, and arthralgia secondary to other inflammatory disorders should be considered. However, these disorders are unlikely because of the paucity of abnormal clinical signs exhibited by the patient. On the other hand, transient synovitis of the hip in children is a diagnosis of exclusion; other possibilities should be explored if the patient's symptoms do not follow a typical course and resolve in 4 to 21 days.

Question 4462

Topic: Infection, Pharmacology & VTE

An 11-year-old boy has had a fever and pain and swelling over the lateral aspect of his right ankle for the past 3 days. Examination reveals warmth, swelling, and tenderness over the lateral malleolus, and he has a temperature of 103.2 degrees F (39.5 degrees C). Laboratory studies show a WBC count of 13,200/mm3 with 61% neutrophils, an erythocyte sedimentation rate of 112 mm/h, and a C-reactive protein of 15.7. Radiographs and a T2-weighted MRI scan are shown in Figures 13a through 13c. Aspiration yields 1 mL of purulent fluid. Management should now consist of

. oral antibiotics and a follow-up office appointment the next day.
. incision and drainage of the distal fibular metaphysis.
. indium-labeled WBC scan.
. antituberculous medication for 6 months.
. three-phase technetium Tc 99m bone scan.

Correct Answer & Explanation

. incision and drainage of the distal fibular metaphysis.

Explanation

The initial signs and symptoms of acute hematogenous osteomyelitis vary widely but usually include fever, bone pain, and impaired use of the involved extremity. In lower extremity infections, the child may limp or refuse to walk. Examination often reveals bone tenderness. In more advanced cases, erythema, warmth, and swelling may be present. The WBC and neutrophil counts are not always elevated, but the erythocyte sedimentation rate will be abnormal in more than 90% of patients. When the infection is diagnosed early, before a subperiosteal abscess has formed, antibiotics alone may be adequate to treat the infection. This patient has a more advanced infection, however, with the MRI scan revealing a subperiosteal abscess that was confirmed by aspiration. When an abscess is present, surgical drainage is generally indicated to remove devitalized tissue and to enhance the efficacy of the antibiotics. Further studies, such as bone or indium scans, are not necessary and will delay definitive treatment. Scott RJ, Christofersen MR, Robertson WW Jr, et al: Acute osteomyelitis in children: A review of 116 cases. J Pediatr Orthop 1990;10:649-652.

Question 4463

Topic: 1. General Principles & Basic Science

An 18-year-old man recently underwent an uncomplicated arthroscopic partial medial meniscectomy that was complicated by reflex sympathetic dystrophy (RSD), also termed "sympathetically maintained pain" (SMP). What is the most common finding of this condition?

Sports Medicine 2001 Practice Questions: Set 1 (Solved) - Figure 24

. Joint stiffness
. Cold intolerance
. Decreased sweating
. Osteopenia
. Disproportionate pain

Correct Answer & Explanation

. Disproportionate pain

Explanation

The hallmark for RSD or SMP is the presence of pain that is out of proportion to that expected for the degree of the injury. SMP often extends well beyond the involved area and is present in a nonanatomic distribution. The pain is frequently described as a burning sensation, with extreme sensitivity to light touch. Joint stiffness can be present but is a nonspecific finding. There may be cold intolerance, but this is not a cardinal symptom. Sweating actually may be increased. Osteopenia, if present, is a late finding. Lindenfeld TN, Bach BR Jr, Wojtys EM: Reflex sympathetic dystrophy and pain dysfunction in the lower extremity. Instr Course Lect 1997;46:261-268.

Question 4464

Topic: 1. General Principles & Basic Science

A young man sustains a lumbar strain in an on-the-job motor vehicle accident. Both he and his treating physician feel that he is capable of limited duty with appropriate restrictions shortly after the injury. What term best describes his work status?

. Temporary total disability
. Temporary partial disability
. Temporary partial illness
. Permanent total disability
. Permanent partial disability

Correct Answer & Explanation

. Temporary partial disability

Explanation

Because the man is only recently removed from his injury and is judged capable of returning to work with some restrictions, the term that best describes his work status is temporary partial disability.

Question 4465

Topic: Biology, Genetics & Bone Healing

Figures 45a and 45b show the AP and lateral radiographs of a 15-year old patient who is undergoing surgery to add 3 cm of length to the femur. Based on the radiographic findings, what is the next most appropriate step in management?

. The distraction rate should be maintained.
. The distraction rate should be decreased.
. The distraction should be reversed.
. The distraction gap should be managed with bone grafting in an open procedure.
. A repeat corticotomy should be performed.

Correct Answer & Explanation

. The distraction rate should be decreased.

Explanation

Because the radiographs reveal poor regenerate bone, especially anteriorly and laterally, the first step in management is to slow the distraction rate. If this does not solve the problem, temporary reversal of the distraction, or "accordionization," can be used to induce a greater healing response. Maintaining the same distraction rate will further impair regenerate formation and delay healing. Bone grafting should be reserved as an option if decreasing the distraction rate or alternating a week of compression with a week of distraction fails to improve the callus formation. Repeat corticotomy is performed in patients with premature consolidation. Raney EM: Limb-length discrepancy, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 1519-1526.

Question 4466

Topic: Surgical Anatomy & Approaches

A 21-year-old hockey player who has recurrent shoulder subluxations undergoes an anterior capsulorrhaphy under general anesthesia, and an interscalene block is used to relieve postoperative pain. At the 1-week follow-up examination, he reports loss of sensation over the lateral region of the shoulder and is unable to actively contract the deltoid muscle. The remainder of the examination is normal. What is the best course of action at this time?

. Early exploration and possible repair of the axillary nerve
. Urgent electromyography to assess for level of nerve injury
. Continued normal postoperative care and observation of the nerve injury
. Consultation with the anesthesiologist regarding a complication of the interscalene block
. MRI to evaluate for a possible hematoma compressing the neurovascular bundle

Correct Answer & Explanation

. Continued normal postoperative care and observation of the nerve injury

Explanation

The patient has an axillary nerve injury, which is relatively uncommon after surgery for instability. This type of injury generally is the result of a stretch injury rather than transection or a hematoma. Therefore, observation is indicated in the early postoperative period. After approximately 6 weeks, electromyography can be used to confirm and document the point of injury. Interscalene blocks can cause prolonged nerve injury but usually are not limited to the axillary nerve.

Question 4467

Topic: 1. General Principles & Basic Science

Examination of a 7-year-old boy reveals 20 degrees of valgus following a lawn mower injury to the lateral femoral epiphysis. Treatment consists of total distal femoral epiphyseodesis and varus osteotomy. Following surgery, he has a limb-length discrepancy of 3 cm and 5 degrees of genu valgum. Assuming that he undergoes no further treatment, the patient's predicted limb-length discrepancy at maturity would be how many centimeters?

. Less than 7
. 7 to 10
. 11 to 13
. 14 to 17
. Greater than 17

Correct Answer & Explanation

. 14 to 17

Explanation

The distal femoral epiphysis grows approximately 1 cm per year and in boys, growth ceases at approximately age 16 years. Therefore, the patient's limb-length discrepancy at maturity would be 12 cm (9 cm plus the 3-cm discrepancy he has from the previous surgery). Little DG, Nigo L, Aiona MD: Deficiencies of current methods for the timing of epiphyseodesis. J Pediatr Orthop 1996;16:173-179.

Question 4468

Topic: Biology, Genetics & Bone Healing

Figure 49 shows the radiograph of a 3-year-old child with progressive bowlegs. Laboratory studies show a calcium level of 9.5 mg/dL (normal 9.0 to 11.0 mg/dL), a phosphorus level of 4.2 mg/dL (normal 3 to 5.7 mg/dL), and an alkaline phosphatase level of 305 IU/L (normal 104 to 345 IU/L). What is the most likely diagnosis?

Pediatrics Board Review 2001: High-Yield MCQs (Set 4) - Figure 6

. Blount's disease
. Hypophosphatemic rickets
. Nutritional rickets
. Schmid metaphyseal dysostosis
. Jansen metaphyseal dysostosis

Correct Answer & Explanation

. Schmid metaphyseal dysostosis

Explanation

The patient has bowlegs associated with very wide physes, particularly noted at the hips. The widening of the growth plates is a classic sign of rickets; however, the normal levels of calcium, phosphorus, and alkaline phosphatase rule out both nutritional and hypophosphatemic rickets. Patients with nutritional rickets or hypophosphatemic rickets have hypophosphatemia and increased alkaline phosphatase levels. Jansen metaphyseal dysostosis has very severe radiographic findings that are not found in this patient; however, these radiographic findings are classic for Schmid metaphyseal dysostosis. This disorder is caused by a mutation in the gene for type X collagen, which is found only in the growth plates of growing children. Lachman RS, Rimoin DL, Spranger J: Metaphyseal chondrodysplasia - Schmid type: Clinical and radiographic delineation with a review of the literature. Pediatr Radiol 1988;18:93-102.

Question 4469

Topic: Infection, Pharmacology & VTE
Figure 33 shows the venogram of a patient who has a long history of alcohol abuse. Warfarin should be used cautiously because of the interaction with which of the following factors?
. II
. V
. VI
. VII
. VIII

Correct Answer & Explanation

. VII

Explanation

Warfarin acts by inhibiting clotting factors II, VII, IX, and X. The actual mechanism of action is by inhibition of hepatic enzymes, vitamin K epoxide, and perhaps vitamin K reductase. This inhibition results in lack of carboxylation of vitamin K-dependent proteins (II, VII, IX, X). The anticoagulant effect of warfarin can be reversed with vitamin K or fresh-frozen plasma. The use of alcohol may lead to liver dysfunction and an even more limited margin of available factors.

Question 4470

Topic: 1. General Principles & Basic Science

Duchenne's muscular dystrophy is a genetic disorder that is transmitted by which of the following modes of inheritance?

Pediatrics Board Review 2007: High-Yield MCQs (Set 2) - Figure 20

. X-linked
. Autosomal-dominant
. Autosomal-recessive
. Chromosomal duplication
. Chromosomal deletion

Correct Answer & Explanation

. X-linked

Explanation

Patients with Duchenne's muscular dystrophy show progressive muscular weakness because of the absence of dystrophin and have the clinical picture of progressive muscle weakness. The condition is an X-linked genetic disease. Fitzgerald RH, Kaufer H, Malkani AL: Orthopaedics. St Louis, MO, Mosby Year Book, 2002, pp 1573-1583.

Question 4471

Topic: Biology, Genetics & Bone Healing

Osteoclasts are primarily responsible for bone resorption of malignancy. Which of the following stimulates osteoclast formation?

. RANKL gene (NF-kB ligand)
. Osteoprotegerin (OPG)
. Interleukin-5 (IL-5)
. Matrix metalloproteinase-2 (MMP-2)
. Collagen type I

Correct Answer & Explanation

. RANKL gene (NF-kB ligand)

Explanation

Bone destruction is primarily mediated by osteoclastic bone resorption, and cancer cells stimulate the formation and activation of osteoclasts next to metastatic foci. Increasing evidence suggests that receptor activator of NF-kB ligand (RANKL) is the ultimate extracellular mediator that stimulates osteoclast differentiation into mature osteoclasts. In contrast, OPG inhibits osteoclast development. IL-8 but not IL-5 is known to play a role in osteoclastogenesis. MMP-2 and collagen type I do not have a direct role in osteoclastogenesis. Kitazawa S, Kitazawa R: RANK ligand is a prerequisite for cancer-associated osteolytic lesions. J Pathol 2002;198:228-236.

Question 4472

Topic: 1. General Principles & Basic Science

During a transperitoneal approach to the L5-S1 interspace, care must be taken to protect the superior hypogastric plexus from injury. Which of the following techniques reduces the risk of neurologic injury?

Spine Surgery 2000 Practice Questions: Set 1 (Solved) - Figure 3

. Transverse incision across the posterior peritoneum and disk space, reflecting the tissues toward the sacral promontory
. Transverse incision across the posterior peritoneum and disk space, reflecting the tissues toward the confluence of the iliac veins
. Vertical midline incision of the posterior peritoneum, reflecting the prevertebral tissues beginning at the margin of the left iliac vein and extending toward the right iliac vein
. Vertical midline incision of the posterior peritoneum, reflecting the prevertebral tissues beginning at the margin of the right iliac vein extending toward the left iliac vein
. Vertical midline incision of the posterior peritoneum, reflecting the prevertebral tissues bilaterally away from the midline

Correct Answer & Explanation

. Vertical midline incision of the posterior peritoneum, reflecting the prevertebral tissues beginning at the margin of the left iliac vein and extending toward the right iliac vein

Explanation

Retrograde ejaculation is the sequela of superior hypogastric plexus injury. This structure needs protection, especially during anterior exposure of the L5-S1 disk space. Only blunt dissection should be used, and use of monopolar electrocautery should be avoided. If possible, preserve and retract the middle sacral artery. Once the iliac veins are isolated, blunt dissection is begun along the course of the medial edge of the left iliac vein, reflecting the prevertebral tissues toward the patient's right side. The dissection goes from left to right because the parasympathetic plexus is more adherent on the right side.

Question 4473

Topic: 1. General Principles & Basic Science

During a left-sided transforaminal lumbar interbody fusion at the L4-5 level, the surgeon notes a significant amount of bleeding that cannot be controlled while using a pituitary rongeur. What anatomic structure has been injured?

. Aorta
. Common iliac artery
. Common iliac vein
. External iliac artery
. External iliac vein

Correct Answer & Explanation

. Common iliac artery

Explanation

The surgeon perforated the anterior longitudinal ligament and injured the common iliac artery. Bingol and associates described injuries to the vascular structures during lumbar disk surgery. The common iliac artery was most commonly affected and constituted 76.9% of injuries.

Question 4474

Topic: 1. General Principles & Basic Science
Human menisci are made up predominantly of what collagen type?
. I
. II
. III
. V
. VI

Correct Answer & Explanation

. I

Explanation

Type I collagen accounts for more than 90% of the total collagen content. Other minor collagens present include types II, III, V, and VI.

Question 4475

Topic: Biology, Genetics & Bone Healing

Figures 28a and 28b show the radiographs of a 79-year-old man who has constant knee pain. Prior to performing elective knee replacement surgery, management should include

. reduction of the serum alkaline phosphatase level by 50%.
. preoperative radiation therapy of 600 cGy to the surgical site.
. aspiration of the knee joint with cell count.
. insertion of a vena caval filter.
. administration of 25 mg of indomethacin three times a day.

Correct Answer & Explanation

. reduction of the serum alkaline phosphatase level by 50%.

Explanation

The radiographs show established Paget's disease. Bony expansion is evident, with thickened trabeculae consistent with the disordered bone remodeling process. A reduction of the serum alkaline phosphatase level to 50% of the pretreatment level may reduce pain from Paget's disease, and it is recommended prior to consideration of joint replacement. In elective cases, treatment of Paget's disease should begin at least 6 weeks prior to surgery. The other modalities are not related to the treatment of Paget's disease. Kaplan FS, Singer FS: Paget's disease of bone: Pathophysiology, diagnosis, and management. J Am Acad Orthop Surg 1995;3:336-344. Simon SR (ed): Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 129-184.

Question 4476

Topic: Biology, Genetics & Bone Healing

In children with moderate to severe osteogenesis imperfecta (OI), intravenous pamidronate therapy has been shown to increase the thickness of cortical bone. This occurs primarily as a consequence of

. increased bone turnover in the cortical area.
. inhibition of osteoclast-mediated bone resorption.
. improved mineralization of cortical bone.
. improved osteoblast organic matrix production.
. improved organization of collagen matrix.

Correct Answer & Explanation

. inhibition of osteoclast-mediated bone resorption.

Explanation

Histologic studies have shown that increased bone turnover is the rule in OI. Pamidronate (and all bisphosphonates) reduce osteoclast-mediated bone resorption. Osteoblastic new bone formation on the periosteal surface of long bones is minimally impaired. With inhibition of osteoclastic bone resorption on the endosteal surface, the cortex of the bone can begin to thicken as it does with normal growth in individuals unaffected by OI. Mineralization and collagen matrix organization are not directly affected by pamidronate. Zeitlin L, Fassier F, Glorieux FH: Modern approach to children with osteogenesis imperfecta. J Pediatr Orthop B 2003;12:77-87. Falk MJ, Heeger S, Lynch KA, et al: Intravenous bisphosphonate therapy in children with osteogenesis imperfecta. Pediatrics 2003;111:573-578.

Question 4477

Topic: 1. General Principles & Basic Science

A study is conducted to measure the difference in bone mineral density between postmenopausal women taking a drug treatment versus those taking a placebo. What is the most important result to be reported from this study?

. The P-value from a t-test comparing the mean densities
. The P-value from a Wilcoxon rank test comparing the densities
. The difference between the mean bone mineral densities of the two groups
. The ratio of the mean mineral density of the experimental group to that of the control group, along with the P-value
. The means and standard deviations of the bone mineral densities for the two groups

Correct Answer & Explanation

. The means and standard deviations of the bone mineral densities for the two groups

Explanation

A complete answer necessarily includes the means and standard deviations of bone mineral density in both groups. Given these, which are the basic results of the study, the P-value can be calculated if desired. All of the other options preclude assessment of the actual data, that is, the information collected by the study. P-values and confidence intervals should be perceived as additional information, which help to assess the certainty of relating the study's findings to the general population, but they should not be reported instead of the results (ie, the means and standard deviations).

Question 4478

Topic: 1. General Principles & Basic Science

Femoral osteotomy for dysplasia of the hip will most likely result in

. improved range of motion.
. improved abduction strength.
. pain relief.
. equal limb lengths.
. a normal gait.

Correct Answer & Explanation

. pain relief.

Explanation

Patients should expect pain relief after femoral osteotomy for hip dysplasia. Patients should not expect improved motion or abduction strength and should be counseled about a postoperative limp and unequal limb lengths. Pellicci PM, Hu S, Garvin KL, Salvati EA, Wilson PD Jr: Varus rotational femoral osteotomies in adults with hip dysplasia. Clin Orthop 1991;272:162-166.

Question 4479

Topic: Biology, Genetics & Bone Healing

What pharmacologic agents are preferred for the treatment of symptomatic active Paget's disease?

Basic Science 2005 Practice Questions: Set 3 (Solved) - Figure 5

. Nasal calcitonin
. Bisphosphonates
. Nonsteroidal anti-inflammatory drugs
. Furosemide
. Antiviral therapy

Correct Answer & Explanation

. Bisphosphonates

Explanation

Recent medical literature supports the use of bisphosphonates as the treatment of choice for active Paget's disease.

Question 4480

Topic: 1. General Principles & Basic Science

An AP radiograph of the pelvis is shown in Figure 4. What muscle attaches to the avulsed fragment of bone identified by the arrow?

Anatomy 2002 Practice Questions: Set 1 (Solved) - Figure 7

. Short head of the biceps femoris
. Adductor longus
. Pectineus
. Piriformis
. Semitendinosus

Correct Answer & Explanation

. Semitendinosus

Explanation

The radiograph reveals an avulsion of the ischial apophysis, most likely the result of violent contraction of the attached hamstring tendons (semimembranosus, semitendinosus, and long head of the biceps femoris). The short head of the biceps femoris arises from the linea aspera on the posterior femur. The pectineus and adductor longus attach to the pubic portion of the pelvis. The piriformis runs from the sacrum to the femur. Woodburne RT (ed): Essentials of Human Anatomy. New York, NY, Oxford University Press, 1978, pp 542-545.

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