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 3381
Topic: 1. General Principles & Basic Science
When planning a research study, the power of the study may be increased by
Correct Answer & Explanation
. performing a retrospective study.
Explanation
The power of a study refers to the researchers' ability to detect a true association when one exists. Power is defined as 1-beta, with beta being the probability of concluding an association does not exist when one actually does (type II error). Increasing the sample size will increase the power of a study. A power analysis can be performed for both retrospective and prospective studies and is independent of the sample population used.
Question 3382
Topic: Biology, Genetics & Bone Healing
As a diaphyseal fracture heals, peripheral callus forms about the shaft axis, creating a structure with a substantially larger diameter than the original diaphyseal shaft. What biomechanical properties does this callus impart to the healing fracture site?
Correct Answer & Explanation
. Callus decreases torsional stability and stiffness at the fracture site
Explanation
Callus formation is biomechanically benefecial because it increases the outer diameter of the bone, leading to an increase in stiffness, torsional strength, moment of inertia, and decreases resultant interfragmentary strain at the fracture site.The biomechanical role of the peripheral callus is to provide initial stability to the fracture and to act as a scaffold for gradual mineralization. Because the bending stiffness of a structure is proportional to the 4th power of the diameter, a peripherally located callus provides substantial stability to the fracture, despite the relatively low stiffness and strength of callus. For example, doubling the diameter of the callus increases the resistance to bending by a factor of 16. As mineralization progresses, the bending stiffness and strength of the healed fracture eventually may be substantially greater than that of the original, intact bone.Augat et al. review the mechanical and biological aspects of fracture healing. They report that increased diameter of periosteal callus formation benefits healing by enlarging the cross-sectional area of area of the bridging tissue and reducing interfragmentary motion. Patients with osteoporosis are known to have decreased callus mineralization and biomechanical properties.Incorrect Answers:
Question 3383
Topic: Biology, Genetics & Bone Healing
A 72-year-old man has had persistent pain after undergoing a hemiarthroplasty 18 months ago. Radiographs are shown in Figures 50a and 50b. What is the most likely cause of his problem?
Correct Answer & Explanation
. Infection
Explanation
DISCUSSION: The radiographs demonstrate a rapid erosion of the bipolar component into the acetabulum. Although acetabular erosion is more common with unipolar hip arthroplasties, it can occur with bipolar components. Haidukewych and associates noted a very low erosion rate but none in the first 2 years. The second finding on the radiographs is the linear radiolucency progressing from the joint toward the end of the stem at the cement-bone interface suggesting chronic infection or diffuse loosening. The persistent pain since implantation also suggests chronic infection. High activity levels and osteoporosis do not lead to acetabular erosion in the first 2 years after hemiarthroplasty. While the cement technique is suboptimal, loosening and erosion should not be expected from this alone. An oversized bipolar head would extrude and not erode.
Question 3384
Topic: Biology, Genetics & Bone Healing
A 3-year old child from an isolated mountain area is evaluated for multiple medical problems, including vomiting, loss of appetite, polyuria, and failure to thrive. History reveals the child was normal at birth. The parents, who appear healthy, are second cousins and have two other children who are normal. The parents state that they know of another family member who died at age 6 years after a similar medical history. Radiographs of the lower extremities show bowing of the long bones with cupping and widening of the physes. What is the most likely diagnosis?
Correct Answer & Explanation
. Cystinosis
Explanation
Hypophosphatemia-The patients who were symptomatic had obtundation,hemolytic anemia, rhabdomyolysis, and hepatocellular injury that began during refeeding and resolved with treatment. The signs and symptoms, pathophysiology, and treatment of refeeding hypophosphatemia are reviewed.Renal Osteodystrophy-Musculoskeletal complications in patients with chronic renal failure are common and may be related to the disease itself or to treatment. The altered metabolism in patients with chronic renal failure leads to renal osteodystrophy, which consists of osteomalacia and secondary hyperparathyroidism [1]. Erosive changes attributable to secondary hyperparathyroidism may be easily confused with rheumatoid arthritis, seronegative spondyloarthropathies, infection, or even malignancy.Primary Hyperparathyroidism-Preferential involvement of cortical bone with apparent preservation of cancellous bone in primary hyperparathyroidism was confirmed by percutaneous bone biopsy. Over 80% of patients had a mean cortical width below the expected mean, whereas cancellous bone volume in over 80% of patients was above the expected mean.Skeletal disease in primary hyperparathyroidism J Bone Miner Res 1989 Jun; 4(3):283-91Nutritional vitamin D deficiency-Rickets, osteomalacia, and renal osteodystrophy are disorders of the mineralization of bone that result from a lack of available calcium, phosphorus, or both. The diseases that result from numerous mechanisms present with a symptom-sign-radiographic complex with such a high degree of stereotypy that laboratory investigation is often required to distinguish one form from another. The disorders in children, known as rickets, produce bowing and other deformities of the long bones and dwarfism. These disorders are principally related to the profound effect of the deficiency states on the epiphyseal plate; whereas the same disorders in adults produce an often severe osteopenia and pathologic fractures. Because of newer developments in our understanding of the factors affecting calcium-phosphorushemostasis and vitamin D metabolism, many of the children and Rickets, osteomalacia, and renal osteodystrophy.
Question 3385
Topic: Infection, Pharmacology & VTE
A 42-year-old woman underwent an instrumented posterior spinal fusion at L3-S1 with transforaminal lumbar interbody fusion. She had an excellent
Correct Answer & Explanation
. Observation
Explanation
The MRI scans reveal a postoperative infection. Observation and antibiotics are not appropriate choices. There is a large fluid collection and this requires decompression because the patient has neurologic changes. There is considerable debate regarding the removal of hardware. Many contend that biofilm on the implants can harbor the infection. However, these complications usually can be treated with serial irrigations, debridements, and IV antibiotics. The incidence of infection has been widely studied with varying rates in fusions with instrumentation. Rates appear to be increased with instrumentation, yet these infections usually can be managed without hardware removal.
Question 3386
Topic: 1. General Principles & Basic Science
Osteoclasts originate from which of the following cell types?
Correct Answer & Explanation
. Monocytes
Explanation
DISCUSSION: Osteoclasts originate from the monocyte/macrophage lineage. Fibroblasts and osteoprogenitor cells originate from mesenchymal stem cells and do not form osteoclasts. Plasma cells reside in the bone marrow and are derivatives of the hematopoietic system. Megakaryocytes are also in the bone marrow and synthesize platelets.
Question 3387
Topic: Surgical Anatomy & Approaches
Figures 42a and 42b show the sagittal and axial MRI scans of a 24-year-old patient who has sciatia. Which of the following combinations of physical findings is most consistent wit the MRI studies?
Correct Answer & Explanation
. Decreased ankle jerk and positive femoral nerve stretch test
Explanation
Figures 42a and 42b show a posterocentral disc herniation between L5 and S1 and will affect the S1 nerve root. This will cause sensory changes in the posterior calf and plantar foot, motor loss in the gastrocnemius/soleus complex, reflex changes in the ankle jerk, and a positive straight leg raise sign. A positive femoral nerve stretch test may indicate L2, L3, or L4 nerve root irritation. EHL function is mainly L5.
Question 3388
Topic: 1. General Principles & Basic Science
A 25-year-old female presents to the emergency room for the fourth time in the last week. She has vague complaints of extremity pain. Physical examination by a male ER resident has been limited each visit because she is terrified of the pain that the clinician may cause. On physical examination, she is withdrawn and frightened. Regions of ecchymosis are noted throughout chest and abdomen. She has requested multiple radiographs, MRI and CT scans. Today's imaging (radiographs, MRI, CT scan) has been unrevealing. What is the most likely diagnosis? Review Topic
Correct Answer & Explanation
. Malingering
Explanation
Based on the history and clinical presentation, the most likely diagnosis is intimate partner violence.Domestic violence or intimate partner violence can be in the form of mental or physical abuse, neglect or abandonment. Close to 25% of women will experience domestic violence. Risk factors include young age (19-29 years of age), females, pregnancy and lower socioeconomic status. Affected patients will have repeated visits to the emergency room, find reasons to stay in a treatment facility for an extended period of time and constantly seek approval of their partner.Shields et al. reviewed factors influence outcome in treatment of patients affected by domestic violence. They found that positive outcomes were associated with interdisciplinary approaches to management. This included better history assessment, providing written documentation regarding intervention and better access to information on community resources.Illustration A is a chart documenting the frequency of female domestic violence throughout the world as of 2012.Incorrect Answers
Question 3389
Topic: Biology, Genetics & Bone Healing
Denosumab, a monoclonal antibody used to treat osteoporosis, works through inhibition of
Correct Answer & Explanation
. receptor activator of nuclear factor kappa beta (RANK).
Explanation
Denosumab is a monoclonal antibody that targets and inhibits RANKL binding to the RANK receptor, which is found on osteoclasts. As a result, it inhibits activation of osteoclast cells and slows the process of bone resorption and bone turnover via osteoclast inhibition. The end result is similar to bisphosphonates in terms of effector cell, but the mechanism of action is very different. RANKL binds to RANK, but OPG inhibits RANK binding to RANKL. TNF is an inflammatory cytokine, and monoclonal antibodies to TNF are used to treat systemic inflammatory disease such as rheumatoid arthritis.
Question 3390
Topic: Biology, Genetics & Bone Healing
A 34-year-old man underwent open reduction and internal fixation of a closed both bones forearm fracture 11 months ago. The radiographs shown in Figures 32a and 32b reveal a 3-mm gap and loose screws. What is the best treatment option?
Correct Answer & Explanation
. Vascularized fibular graft
Explanation
DISCUSSION: In an atrophic nonunion with a good soft-tissue envelope, adequate plating with cancellous bone graft can be used to span defects of up to 6 cm. Cortical graft from the fibula or iliac crest is not necessary. BMP-7 is a bone graft substitute and should not be used alone in this patient because the hardware is loose.REFERENCES: Ring D, Allende C, Jafarnia K, et al: Ununited diaphyseal forearm fractures with segmental defects: Plate fixation and autogenous cancellous bone-grafting. J Bone Joint Surg Am 2004;86:2440-2445.
Question 3391
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
Correct Answer & Explanation
. increased bone turnover in the cortical area.
Explanation
DISCUSSION: 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.REFERENCES: 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.Glorieux FH, Bishop NJ, Plotkin H, et al: Cyclic administration of pamidronate in children with severe osteogenesis imperfecta. N Engl J Med 1998;339:947-952.
Question 3392
Topic: 1. General Principles & Basic Science
What is the most common bacteria cultured from dog and cat bites to the upper extremity?
Correct Answer & Explanation
. Pasteurella
Explanation
DISCUSSION: To define bacteria responsible for dog and cat bite infections, a prospective study yielded a median of five bacterial isolates per culture. Pasteurella is most common from both dog bites (50%) and cat bites (75%). Pasteurella canis was the most frequent pathogen of dog bites, and Pasteurella multocida was the most common isolate of cat bites. Other common aerobes included streptococci, staphylococci, moraxella, and neisseria.REFERENCE: Talan DA, Citron DM, Abrahamian FM, et al: Bacteriologic analysis of infected dog and cat bites. Emergency Medicine Animal Bite Infection Study Group. N Engl J Med 1999;340:85-92.
Question 3393
Topic: Infection, Pharmacology & VTE
A 30-year-old patient has had severe left hip pain and difficulty ambulating, necessitating the use of a cane, for the past 6 months. A photomicrograph of the femoral head sectioned at the time of surgery is shown in Figure 31. What is the most likely diagnosis?
Correct Answer & Explanation
. Renal osteodystrophy
Explanation
DISCUSSION: The photomicrograph demonstrates a wedge-shaped infarct with femoral head collapse; therefore, the diagnosis is osteonecrosis of the femoral head. Perthes disease and osteoarthritis do not involve a wedge-shaped defect. Tuberculosis of the hip joint results in greater destruction of the articular cartilage.REFERENCES: Basset LW, Mirra JM, Cracchiolo A III: Ischemic necrosis of the femoral head: Correlation between magnetic resonance imaging and histologic sections. Clin Orthop 1987;223:181-187.Sugano N: Osteonecrosis, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopedics. St Louis, MO, Mosby, 2002, pp 878-887.
Question 3394
Topic: Biology, Genetics & Bone Healing
The World Health Organization (WHO) developed specific criteria for osteoporosis in 1994 based on the T-score obtained by dual-energy absorptiometry (DEXA). The T-score represents the number of standard deviations that the individual's bone mineral density differs from the normal peak bone mass in young adults. Osteoporosis is defined as a T-score of 1 +2.5 or below. 2 -1.0 to -2.0.
Correct Answer & Explanation
. -2.5 or below.
Explanation
Osteoporosis is defined as a chronic, progressive disease characterized by low bone mass and decreased bone strength. Risk factors for osteoporosis include increasing age, postmenopausal women, long-term calcium deficiency, and excessive steroid or alcohol abuse. T-scores are defined as standard deviations from normal peak bone mass (young adults), whereas Z-scores compare bone density of the same age and size. Osteoporosis is defined as a T-score of -2.5 or below as defined by the WHO, and osteopenia is defined as a T-score between -1.0 and -2.5. Z-scores are not used to stratify patients into categories of "osteopenia" or "osteoporosis" in elderly patinets. They are used to aid in the diagnosis of metabolic bone disease in young patients.
Question 3395
Topic: Biology, Genetics & Bone Healing
What pharmacologic agents are preferred for the treatment of symptomatic active Paget’s disease?
Correct Answer & Explanation
. Nasal calcitonin
Explanation
DISCUSSION: Recent medical literature supports the use of bisphosphonates as the treatment of choice for active Paget’s disease.REFERENCE: Delman PD, Meunier PJ: The management of Paget’s disease. N Eng J Med 1997;336:558-566.
Question 3396
Topic: Infection, Pharmacology & VTE
A 3-year-old child has refused to walk for the past 2 days. Examination in the emergency department reveals a temperature of 102.2 degrees F (39 degrees C) and limited range of motion of the left hip. An AP pelvic radiograph is normal. Laboratory studies show a WBC count of 9,000/mm P 3 P , an erythrocyte sedimentation rate (ESR) of 65 mm/h, and a C-reactive protein level of 10.5 mg/L (normal < 0.4). What is the next most appropriate step in management?
Correct Answer & Explanation
. Technetium Tc 99m bone scan
Explanation
DISCUSSION: Examination reveals an irritable hip, creating a differential diagnosis of transient synovitis versus pyogenic hip arthritis. Kocher and associates described four criteria to help predict the presence of infection: inability to bear weight, fever, ESR of more than 40 mm/h, and a peripheral WBC count of more than 12,000/mmP3P. This patient meets three of the four criteria, with a positive predictive value of 73% to 93% for joint infection. Therefore, aspiration of the hip is warranted, with a high likelihood that emergent hip arthrotomy will be indicated. Ideally, intravenous antibiotics should be administered after culture material has been obtained from needle aspiration of the hip. An urgent bone scan is better indicated as a screening test for sacroiliitis or diskitis. If the arthrocentesis proves negative, CT or MRI of the pelvis may be indicated to rule out a pelvic or psoas abscess.REFERENCES: Del Beccaro MA, Champoux AN, Bockers T, et al: Septic arthritis versus transient synovitis of the hip: The value of screening laboratory tests. Ann Emerg Med 1992;21:1418-1422.Kocher MS, Mandiga R, Zurakowski D, et al: Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am 2004;86:1629-1635.Kocher MS, Zurakowski D, Kasser JR: Differentiating between septic arthritis and transient synovitis of the hip in children: An evidence-based clinical prediction algorithm. J Bone Joint Surg Am 1999;81:1662-1670.
Question 3397
Topic: 1. General Principles & Basic Science
A 30-year-old man underwent replantation of his dominant thumb at the metacarpophalangeal joint level 2 days ago. Since replantation, the temperature of the thumb has been between 87.8 F (31 C) and 93.2 F (34 C). The temperature is now 82.4 F (28 C), and there is brisk capillary refill and venous engorgement. Management at this time should include
Correct Answer & Explanation
. Surgical exploration
Explanation
Discussion: The patient is experiencing impending failure of the replanted thumb. In a study by Moneim and Chacon, they found that vascular thrombosis in the postoperative period is the major factor in failure after replantation. When it occurs, it has to be aggressively dealt with by surgical exploration and revision of the vascular repair. The best results are obtained within 11 hours of the repair and nonsurgical management uniformly led to failure.
Question 3398
Topic: 1. General Principles & Basic Science
04 Which of the following laboratory studies is predictive of wound healing prior to performing a lower extremity amputation?
Correct Answer & Explanation
. Total protein level
Explanation
A serum albumin level of below 3.5 g/dl indicates malnourished patient. An absolute lymphocyte count below 1500/mm3 is a sign of immune deficiency. If possible, amputation surgery should be delayed in such patients. An absolute Doppler pressure of 70 mm Hg is the minimum inflow level. The ischemic index is the ratio of the Doppler pressure at the level being tested to the brachial systolic pressure. Genreally accepted to require an ischemic index of 0.5 or greater. Transcutaneous partial pressure of oxygen (TcpO2) is the present gold standard of vascular inflow. TcpO2 values of 40 mm Hg correlate with acceptable wound healing(eliminates false positive predictions with using area under the Doppler waveform). Pressures less than 20 mm Hg are predictive of poor healing. Miller 505-6back to this question next question
Question 3399
Topic: Physiology & Rehabilitation
What is the primary immediate source of energy for muscle?
Correct Answer & Explanation
. Glycolytic pathway
Explanation
The basic source of energy for muscle contraction is ATP. ATP is also the immediate energy source for muscle. The body then utilizes glucose to produce ATP. Glycolysis splits glucose to form two molecules of pyruvic acid and two ATP.Almost 90% of the total ATP formed by glucose metabolism is formed during oxidative phosphorylation. This is accomplished by a series of enzymatically catalyzed reactions in the mitochondria. When the body’s stores of carbohydrates decrease below normal, glucose can be formed from the breakdown of protein and fat via gluconeogenesis to yield more ATP.
Question 3400
Topic: 1. General Principles & Basic Science
When a Workers' Compensation patient recovers after an injury to a point that further restoration of function is no longer anticipated, he or she is said to have reached which of the following?
Correct Answer & Explanation
. Functional capacity
Explanation
This is the definition of maximum medical improvement (MMI). The patient has essentially reached the plateau of his improvement.Functional capacity evaluations (FCE) are based upon a theoretical model of comparing job demands to worker capabilities. The results of FCEs are often used to determine musculoskeletal capacity to return to work.Strong et al. reported on the use of FCE in the Workers' Compensation system, and note how these FCE results are required by employers to determine the level of return to work of their employees. They also mention that the reports are frequently perceived with a negative tone. The employees reported a wider range of restrictions in their varied life roles than did the FCE reports, which deal more narrowly with work roles.Pransky et al. reported that although FCE's are relied upon for determination of ability to perform physical work, several scientific, legal, and practical concerns persist. They note that test criteria often do not accurately reflect real-life job requirements or performance, and subjective evaluation remains common. They conclude that more research into predictive linking of FCE outcomes with occupational outcomes is necessary to determine their role in the Workers' Compensation system.Incorrect Answers:1: A functional capacity evaluation (FCE) is set of tests, practices and observations that are combined to determine the ability of the evaluated to function in a variety of circumstances (most often employment) in an objective manner. 3: Permanent disability is any lasting disability that results in a reduced earning capacity after maximum medical improvement is reached; this implies that MMI must be reached before this is determined. 4: Impairment rating is an objective data point obtained by a physician reviewing the patient's overall condition during a functional capacity evaluation. 5: This is the process a patient uses to tell their employer they want a personal physician to treat them for a work injury.
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