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 3401
Topic: 1. General Principles & Basic Science
Which of the following lumbar disk components has the highest tensile modulus to resist torsional, axial, and tensile loads? Review Topic
Correct Answer & Explanation
. Nucleus pulposus
Explanation
The annulus fibrosis has a multilayer lamellar architecture mode of type I collagen fibers. Each successive layer is oriented at 30 degrees to the horizontal in the opposite direction, leading to a “criss-cross” type pattern. This composition allows the annulus, which has the highest tensile modulus, to resist torsional, axial, and tensile loads.
Question 3402
Topic: 1. General Principles & Basic Science
Which is the best initial study for the diagnostic evaluation of diskogenic low back pain? Review Topic
Correct Answer & Explanation
. MRI
Explanation
Radiography is the best initial study for the evaluation of diskogenic low back pain. The normal degenerative process can be evaluated. Vacuum phenomenon may be found within the disk space. Other possible sources for back pain should also be evaluated. The other tests may be beneficial but represent later imaging options.
Question 3403
Topic: 1. General Principles & Basic Science
What part of the glenoid labrum has the least vascularity?
Correct Answer & Explanation
. Midanterior
Explanation
DISCUSSION: The glenoid labrum receives its blood supply from the suprascapular, posterior humeral circumflex, and circumflex scapular arteries. The labral vessels arise from the capsular and periosteal vessels that penetrate the periphery of the labrum. The bone does not appear to be a source of vascularity. The posterior/superior and inferior labrum have a fairly robust vascular supply, whereas the anterior/superior labrum has relatively poor vascularity, which may influence the success of superior lateral repairs.REFERENCE: Cooper DE, Arnoczky SP, O’Brien SJ, et al: Anatomy, histology and vascularity of the glenoid labrum: An anatomical study. J Bone Joint Surg Am 1992;74:46-52.
Question 3404
Topic: Infection, Pharmacology & VTE
A 6-year-old boy is being treated for acute hematogeneous osteomyelitis of the distal femur with intravenous antibiotics. The best method to determine the success or failure of initial treatment is by serial evaluations of which of the following studies?
Correct Answer & Explanation
. Radiographs
Explanation
DISCUSSION: Successful antibiotic treatment of acute osteomyelitis should lead to a rapid decline in the CRP. The CRP is the most sensitive study to follow the treatment of osteomyelitis. The CRP should decline after 48 to 72 hours of appropriate treatment. CBC and ESR are helpful in initial evaluation and diagnosis, but remain abnormal in the early phase of treatment regardless of response. Imaging studies are useful for surgical planning or secondarily if the CRP remains elevated.REFERENCES: Unkila-Kallio L. Kallio MJ, Eskola J, et al: Serum C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in acute hematogenous osteomyelitis of children. Pediatrics 1994;93:59-62.Herring JA(ed): Tachdjian’s Pediatric Orthopaedics, ed 4. Philadelphia. PA. WB Saunders, 2008, pp 2090-2100.AL-Madena Copy
Question 3405
Topic: Biology, Genetics & Bone Healing
Which of the following mechanisms of inhibition has been linked to cigarette smoking and lumbar spinal fusion?
Correct Answer & Explanation
. Diminished revascularization of cancellous bone graft
Explanation
DISCUSSION: Cigarette smoking has been directly linked to pseudarthrosis in spinal fusions. The direct mechanism of action is diminished revascularization of cancellous bone graft. Additionally, a smaller area of revascularization is seen in these grafts, as well as an increased area of necrosis. Increased activity of osteoblasts would result in more bone production. Increased activity of osteocytes would not affect the fusion because osteocytes are mature bone cells.REFERENCE: Daftari TK, Whitesides TE Jr, Heller JG, et al: Nicotine on the revascularization of bone graft: An experimental study in rabbits. Spine 1994;19:904-911.
Question 3406
Topic: 1. General Principles & Basic Science
Which of the following medications may have a negative effect on bone healing following fracture?
Correct Answer & Explanation
. COX-1 nonsteroidal anti-inflammatory drugs
Explanation
DISCUSSION: Nonsteroidal anti-inflammatory drugs that are COX-1 primary inhibitors have been shown in animal studies to delay or inhibit fracture healing. COX-2 inhibitors also delay healing but to a lesser extent than COX-1 inhibitors. The other medications listed do not alter fracture callus formation.REFERENCES: Gerstenfeld LC, Thiede M, Seibert K, et al: Differential inhibition of fracture healing by non-selective and cyclooxygenase-2 selective non-steroidal anti-inflammatory drugs. J Orthop Res 2003;21:670-675.Harder AT, An YH: The mechanisms of the inhibitory effects of nonsteroidal anti-inflammatory drugs on bone healing: A concise review. J Clin Pharmacol 2003;43:807-815.
Question 3407
Topic: Surgical Anatomy & Approaches
Figure 25 shows an arthroscopic thermal capsular shrinkage device being used in the anterior inferior quadrant of a patient with a subluxating shoulder. Which of the following neurologic complications is most frequently reported with this technique?
Correct Answer & Explanation
. Axillary nerve dysesthesia
Explanation
DISCUSSION: The axillary nerve lies within millimeters of the anterior inferior capsule. The inferior capsule is of varying thickness, and thermal energy used in shortening the ligament can cause damage to the sensory fibers of the axillary nerve. Clinically, this is manifested as a burnt skin sensation in the axillary nerve distribution area. The motor branch of the axillary nerve is usually spared. The suprascapular nerve and the radial nerve are far from the shrinkage zone. The musculocutaneous nerve, frequently at risk with open procedures, lies well anterior.REFERENCES: Fanton GS: Arthroscopic electrothermal surgery of the shoulder. Op Tech Sports Med 1998;6:157-160.David TS, Drez DJ Jr: Electrothermally-assisted capsular shift. IEEE Eng Med Biol Mag 1998;17:102-104.
Question 3408
Topic: Infection, Pharmacology & VTE
Hip pain of month duration has developed in a year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. The patient has a final culture that reveals methicillin-resistant Staphylococcus aureus (MRSA). If the attending physician recommends the two-stage protocol, including the use of an antibiotic-cement spacer, what is the most likely prognosis for this patient?
Correct Answer & Explanation
. Better functional outcome than that associated with infections from sensitive organisms
Explanation
DISCUSSION:The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin- resistantStaphylococcus epidermidisorganisms treated with a two-stage protocol, the failure rate was21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of CaliforniaLos Angeles Activity Score, and the 12-item Oxford Knee Score, however.
Question 3409
Topic: 1. General Principles & Basic Science
All of the following are characteristic of synovium affected by rheumatoid arthritis (RA) EXCEPT:
Correct Answer & Explanation
. Prominent intimal hyperplasia
Explanation
The basement membrane is not disrupted in rheumatoid arthritis-affected synovial tissue, as synovium lacks a true basement membrane.Normal synovium consists of two layers, the intimal and the sublining, and two types of cells, type A and B. In RA, the following changes to the synovium are seen: 1) hyperplasia, with the intimal lining increasing from two cell layers to 10-20 layers 2) decreased apoptosis of the lining 3) increased angiogenesis and 4) abundant lymphocytes around vessels, forming lymphoid follicles.The synovial pannus is invasive granulation tissue that contains fibroblast-like synoviocytes, but few inflammatory cells. The synovial cells in the pannus have anchorage-independent growth and invasive capabilities, allowing them to directly attack and destroy articular cartilage.Koch et al. note that the possible contributions of angiogenesis to the proliferation of the inflammatory synovial pannus and the ingress of inflammatory leukocytes into the synovial tissue in RA have been extensively studied. Relevant angiogenesis inducers seen in RA include FGF-2, VEGF, TGFß, TNFa, IL-1, IL-8, VCAM-1, among others. Modulation of angiogenesis may be a viable therapeutic option for RA in the future.Incorrect Answers:
Question 3410
Topic: 1. General Principles & Basic Science
Following its exit from the sciatic notch, the sciatic nerve passes between what two muscles?
Correct Answer & Explanation
. Piriformis and superior gemellus
Explanation
DISCUSSION: Though anatomic variations exist, both divisions of the sciatic nerve most commonly pass between the piriformis and superior gemellus. This anatomic consideration is relevant during the posterior approach to the hip, where careful retraction of the rotators avoids sciatic nerve injury.REFERENCES: Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, pp 335-348.Anderson JE (ed): Grant’s Atlas of Anatomy, ed 7. Baltimore, MD, Williams & Williams,1978, Figure 4-34.FOR ALL MCQS CLICK THE LINK ORTHOMCQ BANK
Question 3411
Topic: Infection, Pharmacology & VTE
A man who weighs 75 kg (165 pounds) is scheduled for elective total hip arthroplasty. He reports a history consistent with anaphylaxis from penicillin. Within 1 hour of the incision the patient should receive 1000 mg of
Correct Answer & Explanation
. cefazolin.
Explanation
The recommended antimicrobial prophylaxis for total hip arthroplasty is cefazolin or cefuroxime unless the patient has an allergy to beta-lactam antibiotics. Patients with an allergy should be given vancomycin 10 to 15 mg/kg or clindamycin 600 to 900 mg. Because this patient has an allergy to penicillin, he should be given 1000 mg of vancomycin within 1 hour of the skin incision.
Question 3412
Topic: Surgical Anatomy & Approaches
-Which treatment approach for acetabular fractures carries the highest risk for heterotopic ossification?
Correct Answer & Explanation
. Ilioinguinal
Explanation
Question 3413
Topic: Biomechanics & Biomaterials
A surgeon desires to use an implant that will be able to absorb as much energy as possible before it fails. The implant should be made of a material that has which of the following properties?
Correct Answer & Explanation
. A high modulus of elasticity
Explanation
High intrinsic toughness is defined as the amount of energy per volume a material can absorb without breaking. A high modulus of elasticity and a low modulus of elasticity are incorrect because the modulus of elasticity refers to the stiffness of the material. A brittle material absorbs little energy before breaking. High yield stress is incorrect because it is only one of several factors that lead to a high toughness. While the yield stress is the point at which plastic deformation begins, if coupled with a brittle material, the energy absorbed would be low relative to a ductile material.
Question 3414
Topic: 1. General Principles & Basic Science
An axillary nerve lesion may cause weakness in the deltoid and the
Correct Answer & Explanation
. teres major.
Explanation
DISCUSSION: While the most prominent functional deficit from axillary nerve lesions occurs from denervation of the deltoid, denervation of the teres minor also occurs.REFERENCE: Hollinshead WH: Anatomy for Surgeons: The Back and Limbs. New York, NY, Harper & Row, 1969.
Question 3415
Topic: Biology, Genetics & Bone Healing
Figure 11a shows the AP pelvis radiograph of a 25-year-old man who sustained a spinal cord injury 10 years ago. A bone scan and a CT scan are shown in Figures 11b and 11c. To prevent recurrence after resection, management should consist of
Correct Answer & Explanation
. radiation therapy.
Explanation
DISCUSSION: The studies reveal significant heterotopic ossification that appears to be mature. Following resection, the most reliable way to prevent recurrence is with low-dose external-beam radiation therapy. Bisphosphonate therapy can be considered; however, when terminated, heterotopic bone may reform. Heterotopic ossification is unrelated to the patient’s endocrine status and is not associated with any metabolic abnormalities.REFERENCES: Moore K, Goss K, Anglen J: Indomethacin versus radiation therapy for prophylaxis against heterotopic ossification in acetabular fracture. J Bone Joint Surg Br 1998;80:259.Stover S, Niemann K, Tullos J: Experience with surgical resection of heterotopic bone in spinal cord injury patients. Clin Orthop 1991;263:71-77.
Question 3416
Topic: Biology, Genetics & Bone Healing
Which of the following therapies has a direct anabolic effect on bone?
Correct Answer & Explanation
. Bisphosphonates
Explanation
Bisphosphonates are antiresorptive agents that act by targeting osteoclatic bone resorption. Calcitonin also inhibits osteoclastic bone resorption. Excessive cortisol decreases intestinal calcium absorption, increases calcium loss from the kidney, inhibits bone matrix formation, and causes secondary hyperparathyroidism. TNF-a inhibits osteoblastic activity and enhances osteoclastic bone resorption. Intermittent administration of PTH isoforms is anabolic, whereas persistent elevated levels of PTH promotes bone resorption.
Question 3417
Topic: 1. General Principles & Basic Science
A 30-year-old patient has acetabular dysplasia and moderate secondary osteoarthrosis. Which of the following studies will best help predict the success of periacetabular osteotomy?
Correct Answer & Explanation
. High-resolution CT with coronal and sagittal reconstructions
Explanation
DISCUSSION: Improvement in the appearance of the hip joint on functional radiographic evaluation (abduction/adduction views) has been shown to be predictive of outcome following joint preserving surgery. CT and MRI findings have not been shown to be predictive of outcome.REFERENCE: Murphy S, Deshmukh R: Periacetabular osteotomy: Preoperative radiographic predictors of outcome. Clin Orthop 2002;405:168-174.
Question 3418
Topic: Infection, Pharmacology & VTE
Acetaminophen is an antipyretic medication. It exerts its pharmacologic effects by inhibiting which of the following enzymes?
Correct Answer & Explanation
. Cyclooxygenase-2 (COX-2)
Explanation
DISCUSSION: Acetaminophen inhibits prostaglandin E2 production via IL-1 β, without affecting cyclooxygenase-2 enzymatic activity. The therapeutic concentrations of acetaminophen induce an inhibition of IL-1 β-dependent NF-kappa β nuclear translocation. The selectivity of this effect suggests the existence of an acetaminophen-specific activity at the transcriptional level that may be one of the mechanisms through which the drug exerts its pharmacologic effects. Acetaminophen does not affect any of the other enzymes named above.REFERENCE: Mancini F, Landolfi C, Muzio M, et al: Acetaminophen down-regulates interleukin-1beta-induced nuclear factor-kappaB nuclear translocation in a human astrocytic cell line. Neurosci Lett 2003;353:79-82.
Question 3419
Topic: Biomechanics & Biomaterials
What is the correct order of the elastic modulus of the following materials from greatest to least?
DISCUSSION: In Young’s modulus of elasticity, E is a measure of the stiffness of a material and its ability to resist deformation. In the elastic region of the stress-stain curve, E = stress/strain. The moduli of elasticity for these materials are alumina ceramic = 380 Gigapascals (GPa), cobalt-chromium = 210 GPa, stainless steel = 190 GPa, titanium = 116 GPa, and PMMA = 1.1 to 4.1 GPa.REFERENCES: Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 182-215.Brinker MR: Basic science section 8: Biomechanics and biomaterials, in Miller MD (ed): Review of Orthopaedics, ed 3. Philadelphia, PA, WB Saunders, 2000, pp 120-123.
Question 3420
Topic: Physiology & Rehabilitation
Which of the following types of exercise used to increase flexibility is considered most beneficial in increasing joint range of motion?
Correct Answer & Explanation
. Ballistic stretching
Explanation
DISCUSSION: Evidence has shown that PNF is the treatment of choice to increase joint range of motion and flexibility. PNF has the advantage of pushing the patient to stretch a little further when the muscle tendon unit is relaxed by a partner. While isokinetic and eccentric exercises can improve flexibility, and therefore increase range of motion, their main purpose is to increase strength and endurance. Ballistic stretching involves a large load applied rapidly; however, evidence has shown that static stretching, where a low load is applied for a long duration, offers a more significant benefit.REFERENCES: Sady SP, Wortman M, Blanke D: Flexibility training: Ballistic, static or proprioceptive neuromuscular facilitation? Arch Phys Med Rehabil 1982;63:261-263.Tanigawa MC: Comparison of the hold-relax procedure and passive mobilization on increasing muscle length. Phys Ther 1972;52:725-735.Wallin D, Ekblom B, Grahn R, Nordenberg T: Improvement of muscle flexibility: A comparison between two techniques. Am J Sports Med 1985;13:263-268.
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