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1. General Principles & Basic Science MCQs

Practice Set 165 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 3281

Topic: Surgical Anatomy & Approaches
A 20-year-old woman sustained the closed injury shown in Figures 49a and 49b in a motor vehicle accident. Examination reveals that this is an isolated injury; however, she has a complete radial nerve palsy. Management should consist of
. splinting for 1 to 2 weeks, followed by a humeral fracture brace.
. intramedullary nailing.
. exploration of the radial nerve and intramedullary nailing.
. exploration of the radial nerve and a humeral fracture brace.
. exploration of the radial nerve and open reduction and internal fixation with plates and screws.

Correct Answer & Explanation

. intramedullary nailing.

Explanation

DISCUSSION: Lacerated radial nerves are associated with open humeral fractures. All open humeral fractures with radial nerve palsy should be managed with radial nerve exploration and skeletal stabilization. Closed humeral fractures with associated radial nerve palsy usually have an intact nerve with neurapraxia. Most of these patients recover without surgical treatment. If the patient has multiple injuries, skeletal stabilization may be indicated to improve mobilization. For an isolated closed humeral fracture with a radial nerve palsy, the treatment of choice is splinting for 1 to 2 weeks, followed by a humeral fracture brace. REFERENCES: Ring D, Chin K, Jupiter JB: Radial nerve palsy associated with high-energy humeral shaft fractures. J Hand Surg Am 2004;29:144-147. Foster RJ, Swiontkowski MF, Bach AW, et al: Radial nerve palsy caused by open humeral shaft fractures. J Hand Surg Am 1993;18:121-124.

Question 3282

Topic: Surgical Anatomy & Approaches
A 38-year-old woman fell from a ladder onto her right hip. The radiographs and CT scan are shown in Figures 52a through 52d. What is the best surgical approach for this fracture?
. Kocher-Langenbeck
. Iliofemoral
. Ilioinguinal
. Extended iliofemoral
. Triradiate approach

Correct Answer & Explanation

. Ilioinguinal

Explanation

DISCUSSION: The fracture is an associated both column fracture. The best approach for this fracture is the ilioinguinal. The Kocher-Langenbeck is best for posterior injuries to the acetabulum and some transverse fractures. The iliofemoral alone is limited to high anterior column injuries. The extended iliofemoral and triradiate approaches, although useful for this fracture, have a higher rate of complications. REFERENCES: Letournel E: The treatment of acetabular fractures through the ilioinguinal approach. Clin Orthop Relat Res 1993;292:62-76. Matta JM: Operative treatment of acetabular fractures through the ilioinguinal approach: A 10-year perspective. Clin Orthop Relat Res 1994;305:10-19.

Question 3283

Topic: 1. General Principles & Basic Science

Patient-specific instrumentation (PSI) reliably demonstrates which benefit over conventional intramedullary guidance systems?

. Lower cost
. Improved functional outcomes
. Better coronal alignment
. Fewer trays

Correct Answer & Explanation

. Fewer trays

Explanation

DISCUSSIONCost is usually increased with PSI because the theoretical decreased number of surgical trays and shortened surgical time do not offset cost of presurgical imaging and extra cost associated with the necessary jigs. Studies do not demonstrate a reliable improvement in functional outcomes or coronal alignment when PSI is compared to standard instrumentation. Evidence reveals that PSI necessitates fewer trays than standard instrumentation.

Question 3284

Topic: Surgical Anatomy & Approaches
What complication is more likely following excessive medial retraction of the anterior covering structures during the anterolateral (Watson-Jones) approach to the hip?
. Numbness over the anterolateral thigh
. Ischemia to the leg
. Quadriceps weakness
. Abductor insufficiency
. Foot drop

Correct Answer & Explanation

. Quadriceps weakness

Explanation

DISCUSSION: The femoral nerve is the most lateral structure in the anterior neurovascular bundle. The femoral artery and vein lie medial to the nerve. Retractors placed in the anterior acetabular lip should be safe, although neurapraxia of the femoral nerve may occur if retraction is prolonged or forceful leading to quadriceps weakness. The femoral artery and nerve are well protected by the interposed psoas muscle. Damage to the lateral femoral cutaneous nerve, causing numbness over the anterolateral thigh, can occur while developing the interval between the tensor fascia latae and sartorious in the anterior (Smith-Petersen) approach but less likely in the Watson-Jones approach. Superior gluteal injury and accompanying abductor insufficiency may occur during excessive splitting of the glutei during the direct lateral (Hardinge) approach. Foot drop secondary to sciatic injury is more common with a posterior exposure or posterior retractor placement. REFERENCES: Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, p 325. Anderson JE: Grant’s Atlas of Anatomy, ed 7. Baltimore, MD, Lippincott Williams & Wilkins, 1978, pp 4-17, 4-18.

Question 3285

Topic: Biomechanics & Biomaterials
A 28-year-old man has left knee pain after a snow skiing accident. The MRI scan shown in Figure 47 reveals which of the following?
. Osteosarcoma
. Bucket-handle medial meniscal tear
. Lateral collateral ligament tear
. Bone bruise
. Tibial spine avulsion

Correct Answer & Explanation

. Bone bruise

Explanation

DISCUSSION: Bone bruises are often noted on MRI after anterior cruciate and medial collateral ligament injuries. The significance of these injuries awaits long-term follow-up studies. The areas of increased signal on T2-weighted images represent areas of acute hemorrhage and are secondary to microfractures of the adjacent medullary trabeculae.

Question 3286

Topic: Infection, Pharmacology & VTE

03 advancement at age 6 years. What is the most likely diagnosis?

. Osteomyelitis
. Lymphoma
. Eosinophilic granuloma
. Tuberculosis
. Ewing’s sarcomaback answer

Correct Answer & Explanation

. Osteomyelitis

Explanation

Figure 15a shows areas of permeative lucency and sclerosis in the proximal femur as well as evidence of a screw (from the previous trochanteric advancement). Figure 15b shows the CT scan of the femur with possible thickening of the cortex and a moth eaten appearance of the bone. Figure 15c shows the biopsy specimen with mixed inflammatory cells. These are all indicative of osteomyelitis. The first radiographic sign of osteomyelitis tends to be an ill-defined area of lucency, followed by areas of sclerosis and periosteal new bone formation as the bone reacts to the infection. Biopsy specimens should show mixed inflammatory cells.back to this question next question

Question 3287

Topic: 1. General Principles & Basic Science
Ceramic bone substitutes have which of the following properties?
. There is vascular ingrowth and subsequent graft resorption with host bone ingrowth.
. Their interconnectivity is similar to that of cancellous bone.
. They are brittle with significant tensile strength.
. They are resorbed at a fairly constant rate.
. Due to their strength, rigid stabilization of the surrounding bone is not necessary.

Correct Answer & Explanation

. There is vascular ingrowth and subsequent graft resorption with host bone ingrowth.

Explanation

DISCUSSION: Ceramics have the following properties: They are resorbed at varying rates, and the chemical composition of the ceramic significantly affects the rate of resorption. For example, tricalcium phosphate (TCP) undergoes biologic resorption 10 to 20 times faster than hydroxyapatite. The partial conversion of TCP to hydroxyapatite once it is in the body significantly reduces the rate of resorption. Some segments of hydroxyapatite can remain in place in the body for 7 to 10 years. In clinical trials, TCP more readily remodels because of its porosity, but it is weaker. The success of converted corals as a bone graft substitute relies on a complex sequence of events of vascular ingrowth, differentiation of osteoprogenitor cells, bone remodeling, and graft resorption occurring together with host bone ingrowth into and on the porous coralline microstructure or voids left behind during resorption. REFERENCES: Lane JM, Bostrom MP: Bone grafting and new composite biosynthetic graft materials. Instr Course Lect 1998;47:525-534. Walsh WR, Chapman-Sheath PJ, Cain S, et al: A resorbable porous ceramic composite bone graft substitute in a rabbit metaphyseal defect model. J Orthop Res 2003;21:655-661. Wright TM, Maher SA: Biomaterials, in Einhorn TA, O’Keefe RJ, Buckwalter JA (eds): Orthopaedic Basic Science: Foundations of Clinical Practice, ed 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, in press.

Question 3288

Topic: Biomechanics & Biomaterials

A concern when choosing irradiated (10 Mrad) and subsequently melted highly cross-linked polyethylene rather than lower dose–irradiated (4 Mrad) polyethylene is related to its inferior resistance to

. adhesive wear.
. abrasive wear.
. fatigue wear.
. creep.

Correct Answer & Explanation

. fatigue wear.

Explanation

DISCUSSIONThe higher the dose of radiation to the polyethylene, the higher the amount of cross-linking. Adhesive and abrasive wear resistance increases with an increase in cross-linking. However, fatigue properties of the material are decreased when polyethylene is melted (to remove free radicals) during the cross-linking process. Creep (deformation without wear) is also slightly increased with cross-linking of polyethylene.

Question 3289

Topic: Infection, Pharmacology & VTE

Six weeks after open reduction internal fixation of a closed tibial pilon fracture, a patient has a draining wound with surrounding erythema and swelling. Radiographs show lucency around screws. What is the most appropriate treatment sequence?

. Start IV antibiotics, obtain wound swab for culture, perform irrigation and debridement and retain hardware
. Start IV antibiotics, obtain deep soft tissue and bone cultures in OR, perform irrigation and debridement and remove hardware
. Obtain wound swab for culture, start IV antibiotics, perform irrigation and debridement and remove hardware
. Obtain deep bone and soft tissue cultures in OR, start IV antibiotics, perform irrigation and debridement and remove hardware

Correct Answer & Explanation

. Obtain deep bone and soft tissue cultures in OR, start IV antibiotics, perform irrigation and debridement and remove hardware

Explanation

Discussion: Management of acutely infected wounds is primarily surgical. Osteomyelitis frequently involves Orthopaedic hardware, which would ideally be removed or replaced given biofilm involvement. Multiple operative cultures of fluid collections, soft tissues and bone should routinely be obtained. Culture yield is highest if cultures are obtained before empiric antibiotic treatment is started. Tissue samples are greatly preferred to swabs, which are notoriously inaccurate.

Question 3290

Topic: 1. General Principles & Basic Science

Which of the following factors has NOT been found to be a significant independent predictor of moderate or severe pain 6 months after musculoskeletal injury?

. Failure to complete high school
. Self-reported preinjury pain-related disability
. Disability compensation
. Male gender
. Moderate or severe pain at discharge from the acute hospital

Correct Answer & Explanation

. Failure to complete high school

Explanation

Age and gender have not been found to be significant independent predictors of moderate or severe pain 6 months after musculoskeletal injury.Williamson et al. performed a prospective cohort study of 1290 trauma patients in 2 Australian hospitals using a self-rated pain scale and a SF-12. They found that the prevalence of moderate or severe pain was 48% at discharge and 30% at 6 months post-injury. Failure to complete high school, self-reported preinjury pain-related disability, eligibility for compensation (payment for medical treatment, rehabilitation services, disability services, and income assistance), and moderate or severe pain at discharge from the acute hospital were found to be independent predictors of moderate or severe pain at 6 months post-injury.Vranceanu et al. published a Level 5 review reporting that psychosocial factors are important and treatable correlates of disabling musculoskeletal pain. They encourage orthopaedic surgeons to diminish pain intensity and pain-related disability by teaming up with psychologists and other health-care providers in multidisciplinary teams to address cognitive, affective, behavioral, and social aspects of pain.Incorrect Answers:

Question 3291

Topic: Infection, Pharmacology & VTE
A 5-year-old boy is seen in the emergency department with a 2-day history of refusing to walk. Examination shows that he has a temperature of 102.2°F (39°C) and limited range of motion of the right hip. The AP pelvic radiograph is normal. The WBC count is normal but the C-reactive protein and erythrocyte sedimentation rate (ESR) are elevated. What is the next step in management?
. IV antibiotics
. Oral antibiotics
. Ibuprofen
. Observation and repeat evaluation in 2 weeks
. Aspiration of the right hip

Correct Answer & Explanation

. Aspiration of the right hip

Explanation

DISCUSSION: The history, physical examination, and laboratory studies suggest a septic hip. Recent studies indicate that a child with elevated ESR, a WBC count of greater than 12,000/mm3, a temperature of greater than 38.5°C, and unwillingness to walk is very likely to have septic arthritis of the hip versus toxic synovitis. The best way to confirm the diagnosis is by hip aspiration. No medications should be started until a diagnosis is made. Toxic synovitis is common, but significantly less likely if three of the above criteria are present. This condition usually responds well to ibuprofen, but requires close observation. Septic hips are considered urgent conditions and therefore a repeat evaluation in 2 weeks is inappropriate. REFERENCES: Herring JA: Tachdjian’s Pediatric Orthopaedics, ed 4. Philadelphia, PA, WB Saunders, 2008, pp 2109-2113. Abel MF (ed): Orthopaedic Knowledge Update: Pediatrics 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, pp 62-65. Kocher MS, Mandiga R, Murphy JM, et al: A clinical practice guideline for treatment of septic arthritis in children: Efficacy in improving process of care and effect on outcome of septic arthritis of the hip. J Bone Joint Surg Am 2003;85:994-999. 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.

Question 3292

Topic: 1. General Principles & Basic Science
A cortisone injection in the subacromial space will most likely result in
. elevated blood glucose levels in patients with diabetes.
. increased instability in multidirectional patients.
. accelerated rupture of the long head of the biceps.
. accelerated osteoporosis of the tuberosity.
. altered proprioception of the glenohumeral joint.

Correct Answer & Explanation

. elevated blood glucose levels in patients with diabetes.

Explanation

A cortisone injection in the subacromial space will most likely result in elevated blood glucose levels in patients with type I diabetes mellitus. Patients should be warned of this potential complication. Cortisone does not have an effect on instability or proprioception, and a single injection would not affect osteoporosis. Repetitive injections or injection into the tendon itself could accelerate rupture of the biceps tendon.

Question 3293

Topic: 1. General Principles & Basic Science
Which of the following is a recognized consequence of hip fusion?
. Low back pain
. Contralateral knee laxity
. Difficulty delivering children
. Meralgia paresthetica
. Contralateral abductor weakness

Correct Answer & Explanation

. Low back pain

Explanation

Low back pain is an expected long-term complication of fusion; ipsilateral knee laxity is frequently encountered, as is degeneration of the contralateral hip. Hip fusion is equally valuable for both men and women, with both genders reporting satisfactory sexual function. Female patients often deliver by elective Cesarean section, although vaginal deliveries are reported.

Question 3294

Topic: Biology, Genetics & Bone Healing

Which of the following growth factors binds and activates the lipoprotein receptor-related protein 5/6 (LRP5/6) during bone development? Review Topic

. Transforming growth factor-beta
. Platelet-derived growth factor
. Parathyroid hormone
. Bone morphogenetic protein
. Wnt protein

Correct Answer & Explanation

. Wnt protein

Explanation

Wnt and Hedgehog (Hh) signaling pathways are key regulators of bone formation. Mutations in the Wnt and Hh pathways result in skeletal malformations as well as osteoarthritis. Wnts are a large family of secreted proteins (19 different members in the human genome) that transduce their signal through several pathways. The most studied of these pathways is the Wnt/beta-catenin pathway, in which Wnt protein binds to the LRP5/6 receptor at the cell surface and activates an intracellular cascade. This cascade leads to translocation of beta-catenin into the nucleus to activate transcription of genes that control osteoblast differentiation. Agents that stimulate this pathway are under investigation for treatment of osteoporosis.

Question 3295

Topic: 1. General Principles & Basic Science
A 50-year-old alcoholic man has erythema and swelling in his entire dominant upper extremity. He has a WBC of 15,000/mm3, a temp of 101°F (38.3°C), and a blood pressure of 90/60 mm Hg. After hemodynamic stabilization, the cellulitic forearm is longitudinally incised dorsally and volarly. The forearm muscles are normal in appearance; however, the subcutaneous fat is necrotic. A culture will most likely reveal
. Bacteroides
. E. coli
. Staph. aureus
. group A streptococcus
. Clostridium perfringens

Correct Answer & Explanation

. group A streptococcus

Explanation

Necrotizing fasciitis is frequently caused by strep infections. Cellulitis, which is an inflammatory infection of the subcutaneous tissues, is usually due to Staph or Strep infections (Haemophilus is also seen in children). Significant Streptococcal infections include erysipelas, which produces a progressively enlarging red, raised painful plaque, severe toxicity, fever, leukocytosis and bacteremia; Necrotizing fasciitis produces extensive tissue necrosis. Clostridium perfringens typically causes gas gangrene (which can also develop from gram-negative and strep infections), presenting as progressive pain, distal edema, and a malodorous serosanguinous discharge.

Question 3296

Topic: 1. General Principles & Basic Science

A 16-year-old football player is participating in the second session of two-a-day preseason practices. He complains of dizziness and fatigue. He is brought to the sideline by the athletic trainer where examination demonstrates confusion and disorientation. Ambient temperature is 82°F. What would be the next most appropriate step in his treatment?

. Rapid cooling via ice bath, cold water and fans
. Transportation via ambulance to a local emergency department
. Rapid rehydration via oral and IV fluids
. Immediate administration of acetaminophen or other anti-pyretics

Correct Answer & Explanation

. Rapid cooling via ice bath, cold water and fans

Explanation

Heat exhaustion and heat stroke reflect varying degrees of heat illness, with both marked by increased heat production with impaired heat dissipation. Heat exhaustion typically involves a core body temperature between 37°C (98.6°F) and 40°C (104°F) and usually presents with heavy sweating, as well as nausea; vomiting; headache; fainting; weakness; and cold or clammy skin. Fatigue, malaise, and dizziness may occur, but necessary to the diagnosis is normal mentation and stable neurologic status. Heat stroke is defined by a core body temperature >40°C (>104°F) and disturbances of the central nervous system, such as confusion, irritability, ataxia, and even coma. Heat exhaustion is a less urgent scenario and can usually be treated with rest, elevation, and rehydration. Heat stroke, confirmed here by the presence of mental status changes, is a more critical situation. The most important immediate step is rapid body cooling through whatever means are available, as this has been clearly shown to improve outcomes. Ideally, a whole body ice bath would be used, with ice towels, ice packs, cold water, and air fans all utilized if needed. Emergency department transportation and rehydration may be considered as well but are not as important as immediate lowering of body temperature. Anti-pyretics have no role in this process.

Question 3297

Topic: 1. General Principles & Basic Science
Failure of high tibial osteotomy (HTO) is most closely associated with which of the following factors?
. Patient age of less than 50 years at the time of surgery
. Stable fixation of the osteotomy
. Development of deep venous thrombosis postoperatively
. Type of osteotomy performed (ie, opening wedge versus dome osteotomy)
. Presence of a lateral tibial thrust preoperatively

Correct Answer & Explanation

. Patient age of less than 50 years at the time of surgery

Explanation

DISCUSSION: Long-term survivorship studies have attempted to clarify patient factors related to good outcomes in HTO. One particular study showed that a patient age of less than 50 years was related to good outcomes in those who had good preoperative knee flexion. The same study found no relation between HTO failure and the presence of postoperative infection or deep venous thrombosis. The presence of a lateral tibial thrust is a contraindication to performing this surgery. As expected, good patient selection is critical to obtaining good long-term results with HTO. REFERENCES: Naudie D, Borne RB, Rorabeck CH, Bourne TJ: Survivorship of the high tibial valgus osteotomy: A 10- to 22-year followup study. Clin Orthop 1999;367:18-27. Rinonapoli E, Mancini GB, Corvaglia A, Musiello S: Tibial osteotomy for varus gonarthrosis: A 10- to 21-year followup study. Clin Orthop 1998;353:185-193. Coventry MB, Ilstrup DM, Wallrichs SL: Proximal tibial osteotomy: A critical long-term study of eighty-seven cases. J Bone Joint Surg Am 1993;75:196-201.

Question 3298

Topic: 1. General Principles & Basic Science
  • A patient is in respiratory distress as a result of a high-speed motor vehicle accident. After emergent intubation, the arterial blood is poorly oxygenated, and examination shows left-sided tracheal deviation, absence of breath sounds on the right side and tympany on percussion over the right side of the chest. Management should include
. Positive-pressure ventilation
. An immediate radiograph of the chest
. Adjustment of the position of the endotrachael tube
. Insertion of a large-bore needle into the pericardial space
. Insertion of a large-bore needle in the right second intercostal space, midclavicular line

Correct Answer & Explanation

. Positive-pressure ventilation

Explanation

This patient has a tension pneumothorax and needs immediate decompression to convert it to a simple pneumothorax until definitive treatment with a chest tube can be performed. The other choices are inappropriate.

Question 3299

Topic: Infection, Pharmacology & VTE
Which of the following is considered a specific advantage of using COX-2 inhibitors over COX-1 inhibitors?
. Conversion of arachidonic acid to prostaglandins
. Higher degree of efficacy
. Does not affect platelet function and can be used during the perioperative period
. Can be used in patients with congestive heart failure and renal disease
. High levels of COX-2 (cyclooxygenase) found in normal tissue

Correct Answer & Explanation

. Does not affect platelet function and can be used during the perioperative period

Explanation

DISCUSSION: Inflammation is mediated through two isoforms of cyclooxygenase that convert arachidonic acid to prostaglandins. Selectivity, but not specificity, is one of the unique characteristics of this process that has been able to provide more protection from the effects of gastric mucosal alterations using the COX-2 selective inhibitors. The use of COX-1 selective inhibitors is associated with side effects such as ulcerative conditions and platelet interference, both of which have been difficult to control in the past until the advent of the COX-2 inhibitors. PGE2 inhibition by COX-1 in the intestinal tract can then be bypassed, thereby reducing ulceration complications associated with use of nonsteroidal anti-inflammatory drugs. REFERENCES: Lane JM: Anti-inflammatory medications: Selective COX-2 inhibitors. J Am Acad Orthop Surg 2002;10:75-78. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000.

Question 3300

Topic: 1. General Principles & Basic Science

-The center of rotation of the knee can be best described as

. remaining fixed during flexion.
. moving posterior as flexion increases.
. shifting forward and then back with flexion.
. shifting posterior on the lateral side with flexion.
. sliding forward on the medial side with increasing flexion.

Correct Answer & Explanation

. remaining fixed during flexion.

Explanation

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