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1. General Principles & Basic Science MCQs

Practice Set 192 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 3821

Topic: Physiology & Rehabilitation
A college football player performs bicep curls as part of his weight lifting routine. During the flexion phase of the curl, what term defines the type of muscle contraction?
. Isometric
. Isokinetic
. Isotonic
. Eccentric
. Plyometric

Correct Answer & Explanation

. Isotonic

Explanation

DISCUSSION: Muscle contractions can be classified by tension, length, and velocity. Isometric contractions involve changing tension in the muscle while the muscle stays at a constant length. An example would be pushing against a wall. Isokinetic contractions occur when the muscle maximally contracts at a constant velocity. Isotonic contractions involve constant tension throughout the range of motion. Eccentric contraction is when the muscle lengthens during contraction. Eccentric contractions have the highest risk of injury. Plyometrics are eccentric contractions at a rapid rate. REFERENCES: Simon SR (ed): Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 89-125. Evans WJ: Effects of exercise on senescent muscle. Clin Orthop 2002;403:S211-S220.

Question 3822

Topic: 1. General Principles & Basic Science

Which of the following changes occur in articular cartilage with age?

. Cell numbers increase with fairly uniform distribution.
. Chondroitin sulfate concentration increases.
. Keratin sulfate concentration decreases.
. Proteoglycan synthesis decreases.
. Water content increases.

Correct Answer & Explanation

. Cell numbers increase with fairly uniform distribution.

Explanation

Proteoglycan synthesis decreases with age, as does water content. Cell numbers of cartilage decrease compared to immature cartilage, which has a fairly uniform distribution of abundant cells. A high concentration of chondroitin 4-sulfate has been noted in immature animals, with a fairly rapid diminution in the value noted with aging accompanied by an increase in the concentration of chondroitin 6-sulfate. With advancing age, the total chondroitin sulfate concentrations fall and that of keratin sulfate increases until approximately age 30, where it levels off.

Question 3823

Topic: 1. General Principles & Basic Science
  • A physician who is currently in a fellowship program receives notification of a pending malpractice suit that refers to an incident that occurred 2 years ago when the physician was a resident. The physician would be insured if the residency program provided what type of insurance coverage?
. Indemnification
. Occurrence
. Excess liability
. Claims-made
. Nose

Correct Answer & Explanation

. Indemnification

Explanation

Occurrence covers anything that has taken place; indemnification covers the compensation against hurt, damage, or loss; excess liability covers a specified amount.

Question 3824

Topic: 1. General Principles & Basic Science

Results of a study demonstrating no difference between treatments when a difference truly exists is an example of which of the following?

. Statistical insignificance
. Type I error
. Type II error
. Fragile p-values
. Negative predictive value

Correct Answer & Explanation

. Statistical insignificance

Explanation

A type II error (also known as a beta error) occurs when results demonstrate that two groups are similar when, in reality, they are different (with regard to the statistic being measured). Type I errors show that a difference exists when, in reality, no difference exists. A statistically insignificant result may lead an investigator to conclude that no difference exists between two groups; this may be correct (and therefore not a type II error). The concept offragilep-values is that small sample sizes may result in wide variability of p-values with only one change in a data point for a given group. This singular change could be a chance occurrence, but it still can affect the statisticalsignificance of the outcomes analysis. Fragility of p-values is limited by increasing sample sizes. Negative predictive value is the proportion of patients with negative test results who are correctly diagnosed.

Question 3825

Topic: Biology, Genetics & Bone Healing

A patient with a bone mineral density (BMD) T-score of -2.6 would be considered to have

. marginally decreased bone density.
. osteopenia.
. bone within normal limits for an elderly individual.
. osteoporosis.
. metastatic bone disease.

Correct Answer & Explanation

. marginally decreased bone density.

Explanation

According to the World Health Organization, a patient with a BMD T-score of -2.5 or lower is considered to have osteoporosis. A score between -1.0 and 2.5 is considered osteopenia. The BMD T-score provides no information about metastatic bone disease.

Question 3826

Topic: 1. General Principles & Basic Science
  • Which of the following events is most likely to occur following a complete transection of a peripheral nerve?
. The cell body nucleus migrates centrally
. Schwann cells distal to the transection die
. Axoplasm in the proximal stump drains out
. Myelin distal to the transection is phagocytized
. Cell body protein synthesis decreases for the first 10 to 14 days

Correct Answer & Explanation

. The cell body nucleus migrates centrally

Explanation

Reference-Within a few hours of injury to a nerve fiber the cell body swells and Nissl granules disappear. The axon distal to the site of injury rapidly undergoes Wallerian degeneration with the loss of the axon and breakup of the surrounding myelin.

Question 3827

Topic: 1. General Principles & Basic Science

You have been waiting to enroll a patient into your recent institutional review board (IRB)-approved clinical research protocol. A patient is admitted who, upon initial screening, meets all inclusion criteria. However, he has late-stage dementia, and you are told by your research coordinator that this condition is an exclusionary criterion. This scenario demonstrates the need for which aspect of proper informed consent?

. Provision of information
. Competency
. Understanding
. Jurisdiction

Correct Answer & Explanation

. Provision of information

Explanation

Proper informed consent for research protocols includes the same elements as consent for invasive procedures. Jurisdiction is not one of the 5 elements, although it must be recognized that the process of obtaining proper informed consent for participation in a study protocol is mandated by the local IRB. The 5 elements of informed consent are:

Question 3828

Topic: Biology, Genetics & Bone Healing

5 mg/dL), vitamin D 50 ng/mL (reference range, 30-100 ng/mL), and urine phosphorus 2 g/24-hour collection (reference range, 0.4-1.3 g). What effect would treatment with only Calcitriol (1,25 dihydroxy vitamin D3) have?

. Restore normal limb alignment
. Restore normal limb alignment and height
. Have no effect on limb alignment and height
. Stabilize degree of genu varum, but not improve limb alignment

Correct Answer & Explanation

. Restore normal limb alignment

Explanation

This patient has familial hypophosphatemic rickets, a vitamin D-resistant form of rickets that is an X-linked inherited disorder. Patients are short (< 10th percentile). Varus occurs both in the distal femur and proximal tibia. Patients have increased urinary excretion of phosphorus, leading to hypophosphatemia. Calcium levels are within defined limits and vitamin D levels can be normal as well. Treatment should include phosphate and 1,25 dihydroxy vitamin D3 (calcitriol). Phosphate administration increases the plasma concentration,which lowers plasma ionized calcium concentration and further reduces plasma calcitriol concentration (removal of hypophosphatemic stimulus). Secondary hyperparathyroidism results because of both hypocalcemia and removal of thenormal inhibitory effect of calcitriol on parathyroid hormone (PTH) synthesis. Elevated PTH levels will increase urinary phosphate excretion, defeating the aim of oral therapy.Addition of calcitriol is necessary to increase the intestinal absorption of calcium and phosphate to prevent secondary hyperparathyroidism. Massive doses of vitamin D alone can restore normal radiographic appearances to the epiphyses, but normal growth is not restored unless phosphate replacement is adequate.A 35-year-old woman began to train for a half marathon. After 8 weeks of increasing her mileage, what changes can you expect in her Achilles tendon?Net decrease of type I collagenNet increase of type I collagenIncreased diameter of collagen fibrilsIncreased cross-sectional area of the tendonTraining increases turnover of type I collagen, promoting both synthesis and degradation of collagen and a net increase synthesis of type I collagen in tendon-related tissue.Strenuous endurance training has resulted in decreased collagen cross-links, suggesting increased collagen turnover, but decreased collagen maturation. In human studies, physical training results in increased turnover of collagen. Synthesis and degradation are elevated initially when beginning an exercise program, but degradation products decrease overall. It is not known if activity levels in humans affect the diameter of collagen fibrils or the cross-sectional area of tendons.FOR ALL MCQS CLICK THE LINK ORTHOMCQ BANK

Question 3829

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?
. 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.

Question 3830

Topic: 1. General Principles & Basic Science
Following a vertebroplasty of L2, cement is noted to protrude directly anterior to the L2 vertebral body. The cement is closest to which of the following structures?
. Inferior vena cava
. Pancreas
. Duodenum
. Left lobe of the liver
. Descending aorta

Correct Answer & Explanation

. Descending aorta

Explanation

At the level of L2, the liver and the vena cava lie to the right. The pancreas and duodenum are anterior to the aorta. The aorta lies in the midline just in front of the vertebral body.

Question 3831

Topic: 1. General Principles & Basic Science
Figures 14a and 14b show the clinical photographs of a patient who was stranded in a subzero region for several days. The photographs were taken the morning after arrival in the hospital. The patient is otherwise healthy and fit, and takes no medication. He has no clinical signs of sepsis. He reports burning pain and tingling in both feet. What is the best treatment?
. Moist dressings and continued observation
. Debridement of the necrotic tissue
. Amputation at the metatarsophalangeal level with open wound management
. Closed forefoot amputation
. Guillotine transtibial amputation

Correct Answer & Explanation

. Moist dressings and continued observation

Explanation

The patient has no clinical or observed signs of sepsis. The skin just proximal to the gangrenous tissue appears somewhat hyperemic and is clearly viable. These wounds should be managed much like burn wounds. Moist dressings should be used until the tissue clearly demarcates. Much of the insult may simply be superficial and only require late debridement.

Question 3832

Topic: 1. General Principles & Basic Science
Long bone fracture repair following intramedullary stabilization occurs primarily through which of the following healing mechanisms?
. Haversian remodeling
. endosteal ossification only
. Intramembranous ossification only
. Endochondral ossification only
. Intramembranous and endochondral ossification

Correct Answer & Explanation

. Intramembranous and endochondral ossification

Explanation

The mechanical environment represents a major factor in the type of healing that occurs after a fracture. Intramedullary nail fixation allows for motion at the fracture site, which promotes bone formation both directly (intramembranous ossification) and through a cartilage intermediate (endochondral ossification). Absolute stability, as would be obtained with a compression plate, favors healing through the direct formation of bone without a cartilage intermediate (intramembranous ossification), or primary fracture repair. This type of healing would include the remodeling of the bone ends through the direct contact of bone, often referred to as contact healing or Haversian remodeling.

Question 3833

Topic: 1. General Principles & Basic Science
A 75-year-old woman with rheumatoid arthritis and a long history of oral corticosteroid use sustains a comminuted intra-articular distal humerus fracture. What is the best surgical option?
. Open reduction internal fixation (ORIF) with parallel plates
. ORIF with orthogonal plates and iliac crest bone grafting
. Total elbow arthroplasty (TEA)
. Closed reduction and percutaneous pinning

Correct Answer & Explanation

. Total elbow arthroplasty (TEA)

Explanation

TEA is the best surgical option. McKee and associates published a multicenter randomized controlled trial comparing ORIF with TEA in elderly patients. TEA resulted in better 2-year clinical functional scores and more predictable outcomes compared with ORIF. TEA was also likely to result in a lower resurgical rate; one-quarter of patients with fractures randomized to ORIF could not achieve stable fixation. Further, Frankle and associates reported a comparative study of TEA versus ORIF in 24 elderly women. TEA outcomes were again superior to ORIF at a minimum of 2 years of follow-up. TEA was especially useful in patients with comorbidities that compromise bone stock, including osteoporosis and oral corticosteroid use. Closed reduction and percutaneous pinning studies have not been published on the adult population.

Question 3834

Topic: 1. General Principles & Basic Science
A study is designed that examines fractures in children with osteogenesis imperfecta after being treated with bisphosphonates compared with a placebo. A difference is found for which the P value is greater than what is considered to be statistically significant. What is the next appropriate statistical analysis?
. Repeated measures analysis of variance
. F test
. Power analysis
. Analysis of variance
. Kruskal-Wallis test

Correct Answer & Explanation

. Power analysis

Explanation

DISCUSSION: When a study yields a negative result between treatment groups, the next step is to perform a power analysis. The power, by definition, is the probability of rejecting the null hypothesis: in this example the null hypothesis would be that children treated with bisphosphonates would have fewer fractures than the untreated control population. The power analysis helps answer the question as to whether the null hypothesis should be rejected and the finding is real, or whether the sample size was too small or the effect of treatment too subtle to demonstrate a difference between the treatment and control groups.

Question 3835

Topic: Infection, Pharmacology & VTE

A 51-year-old man sustained an open fracture of his tibia in Korea 42 years ago. An infection developed and it was resolved with surgical treatment. For the past 6 months, an ulcer with mild drainage has developed over the medial tibia. The ulcer is small and there is minimal erythema at the ulcer site. A radiograph and MRI scan are shown in Figures 43a and Figure 43b. Initial cultures show Staphylococcus aureus susceptible to the most appropriate antibiotics. Laboratory studies show an erythrocyte sedimentation rate of 70 mm/h. What is the most appropriate surgical treatment at this time? Review Topic

. Irrigation and debridement of the cystic lesion and 6 weeks of IV antibiotics
. Curettage, debridement of nonviable bone, and placement of absorbable antibiotic beads, followed by a course of IV antibiotics from 1 to 4 weeks and a 6-week course of oral antibiotics
. Complete resection of the infected portion of bone, placement of an external fixator to stabilize the tibia, and 6 weeks of IV antibiotics
. Amputation
. Local debridement of bone and the overlying skin and soft tissues, 6 weeks of IV antibiotics, and free-flap wound coverage

Correct Answer & Explanation

. Irrigation and debridement of the cystic lesion and 6 weeks of IV antibiotics

Explanation

The patient has chronic tibial osteomyelitis that is due to low virulent bacteria. The history and studies do not suggest the need for an amputation or a free-flap procedure. This is a localized tibial infection that is in a healed bone; there is no need to resect the entire area of the tibia bone around the infection. The most appropriate treatment is curettage, debridement of nonviable bone, and placement of absorbable antibiotic beads, followed by a course of IV antibiotics from 1 to 4 weeks and a 6-week course of oral antibiotics. Studies have shown that in cases of localized osteomyelitis that are of low virulence, as little as 1 week of IV antibiotics followed by 6 weeks of oral antibiotics is successful.

Question 3836

Topic: Physiology & Rehabilitation
A 10-year-old boy with spastic diplegic cerebral palsy walks in a crouched position with the hips and knees flexed. Maximum knee flexion is 15 degrees during early swing phase. Instrumented gait analysis shows quadriceps activity from terminal stance throughout swing phase. Treatment should consist of:
. proximal release of the proximal tendon of the rectus femoris.
. release of the distal tendon of the rectus femoris.
. transfer of the distal rectus femoris tendon.
. V-Y lengthening of the quadriceps tendon.
. Z lengthening of the patellar tendon.

Correct Answer & Explanation

. transfer of the distal rectus femoris tendon.

Explanation

The rectus femoris muscle spans two joints and is active during running, sprinting, and walking at a fast pace during the preswing and early swing phase of gait. In these situations, the muscle helps to generate power to initiate hip flexion while absorbing or controlling the rate of knee flexion during early swing phase. Quadriceps activity, including the rectus femoris, is not normally needed when walking at a routine cadence. However, rectus femoris activity is commonly noted during preswing and the swing phase in patients with cerebral palsy, particularly those with diplegia. In an effort to initiate swing phase, the rectus femoris is overactive. As a result, the knee flexion that commonly occurs at terminal stance and initial swing is restricted. Instead of achieving the normal 50 to 60 degrees of flexion during early swing, this patient’s knee flexion is limited to 15 degrees. The goal of treatment is to retain rectus femoris activity for initiation of hip flexion but to diminish its restraint on knee flexion. Studies have shown that transfer of the distal rectus femoris tendon provides more flexion of the knee during the swing phase of gait than simply releasing the tendon. V-Y lengthening of the quadriceps tendon or a Z lengthening of the patellar tendon causes too much weakening of the quadriceps muscle and worsens the crouch deformity.

Question 3837

Topic: Physiology & Rehabilitation
Creatine is currently being used by athletes as a dietary supplement in an attempt to enhance performance. What is the physiologic basis for its use?
. Assists in carbohydrate metabolism and glycogen synthesis by producing adenosine diphosphate (ADP) to enhance aerobic activities
. Converts to phosphocreatine (PCr), which acts as an energy reservoir for adenosine triphosphate (ATP) in muscle tissue
. Converts to PCr, which enhances the production of ADP and promotes the metabolism of triglycerides as an energy source
. Converts to PCr, which enhances the production of ADP and promotes the metabolism of proteins as an energy source
. Converts to ADP by creatine kinase (CK) providing an energy reservoir for the production of ATP

Correct Answer & Explanation

. Converts to phosphocreatine (PCr), which acts as an energy reservoir for adenosine triphosphate (ATP) in muscle tissue

Explanation

Creatine is currently used as a nutritional supplement in an attempt to enhance athletic performance. The physiologic basis for its use is based on its conversion by CK to PCr, which acts as an energy reservoir in muscle cells for the production of ATP. A number of studies that examined the effect of creatine supplementation on performance concluded that while creatine does not increase peak force production, it can increase the amount of work done in the first few anaerobic short duration, maximal effort trials. The mechanism for this enhancement of work is unknown, but it is most likely secondary to the increase in the available PCr pool.

Question 3838

Topic: 1. General Principles & Basic Science

Fluoroquinolones work by inhibiting what enzyme?

. DNA gyrase
. RNA gyrase
. DNA polymerase
. Ribosomal transferase
. DNA telomerase

Correct Answer & Explanation

. DNA gyrase

Explanation

Fluoroquinolones are commonly used antibiotics used to treat orthopaedic infections and are popular because of their equivalency in IV or oral formulations and their gram-positive and gram-negative antibacterial activity. It is part of a larger class ofantibiotics called quinolones that interfere with DNA metabolism. Fluoroquinolones are synthetic derivatives of nalidixic acid. Its mechanism of action involves interfering with the function of DNA gyrase. DNA gyrase ia a type-II topoisomerase, and "unwinds" DNA to allow replication.

Question 3839

Topic: Surgical Anatomy & Approaches
When performing a Kocher approach to the radial head for open reduction internal fixation, the forearm is held in pronation. What structure is this maneuver attempting to protect?
. Median nerve
. Brachial artery
. Anterior interosseous nerve
. Radial nerve
. Posterior interosseous nerve

Correct Answer & Explanation

. Posterior interosseous nerve

Explanation

DISCUSSION: Dilberti et al quantified the dimensions of a surgically safe zone (with respect to the posterior interosseous nerve) when using the posterolateral approach to the radial head between the anconeus and the extensor carpi ulnaris. They found that the safe zone increased with pronation and decreased with supination.

Question 3840

Topic: 1. General Principles & Basic Science

A 17-year-old African American high school football player is in the afternoon session of an August “2-a-day” practice. He tells his trainer he is experiencing weakness, dizziness, and nausea. The ambient temperature is 31°C with a relative humidity of 70%. An examination by the team trainer reveals a body temperature of 39°C and headache, chills, confusion, and disorientation. What is the most likely diagnosis?

. Sickle-cell crisis
. Heat exhaustion
. Heatstroke
. Dehydration

Correct Answer & Explanation

. Heatstroke

Explanation

DISCUSSIONHeat exhaustion and heatstroke are both forms of heat illness during which the body is unable to self-regulate internal temperature. The hallmarks of heatstroke are altered mental status and/or core temperature higher than 40°C. Heat exhaustion may be marked by nausea, vomiting, headache, dizziness, chills, and excessive sweating, but there are no mental statuschanges. In heatstroke, sweating can often slow or cease as dysregulation worsens. Simple dehydration would not result in mental status changes or elevated core temperature. Sickle-cell crisis is marked by extreme pain, with location depending on the site of crisis. Four main patterns are common: bone, chest, abdominal, or joint crises. Sickle-cell crisis can be precipitated by dehydration, although it also can occur as a result of cold exposure.

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