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 3901
Topic: 1. General Principles & Basic Science
According to the principles of deformity correction formulated by Paley, what is the expected outcome if an osteotomy is performed at a level separate from the Center of Rotation of Angulation (CORA), but the correction axis (hinge) is placed exactly on the CORA?
Correct Answer & Explanation
. Pure angulation will occur without translation, and the anatomical axes will become collinear.
Explanation
According to Paley's Rule 2: When the osteotomy is made at a level separate from the CORA, but the hinge (axis of correction) is placed on the CORA, the correction will result in both angulation and translation at the osteotomy site. However, the mechanical/anatomical axes of the proximal and distal segments will become collinear. Paley's Rule 1 states that if both the osteotomy and hinge are at the CORA, pure angulation occurs.
Question 3902
Topic: Surgical Anatomy & Approaches
A 22-year-old rugby player undergoes an open Latarjet procedure for recurrent anterior shoulder instability with 30% glenoid bone loss. Postoperatively, he exhibits profound weakness in elbow flexion and decreased sensation over the lateral forearm. Which of the following structures was most likely injured during the surgical approach?
Correct Answer & Explanation
. Axillary nerve
Explanation
The musculocutaneous nerve is the most frequently injured nerve during the Latarjet procedure due to its proximity to the coracoid process and the conjoint tendon (which is mobilized and transferred). It pierces the coracobrachialis muscle on average 5-8 cm distal to the coracoid tip. Injury leads to biceps/brachialis weakness and numbness over the lateral cutaneous nerve of the forearm.
Question 3903
Topic: 1. General Principles & Basic Science
In deformity correction planning using the principles of Paley, a closing wedge osteotomy is performed on the tibia. If the osteotomy hinge is placed outside the center of rotation of angulation (CORA), what is the expected geometric consequence?
Correct Answer & Explanation
. Angular correction accompanied by translation of the mechanical axis
Explanation
According to the CORA principles, if an osteotomy hinge is placed at the CORA, pure angulation occurs. If the hinge is placed outside the CORA, correcting the angulation will obligatorily induce translation of the bone segments.
Question 3904
Topic: 1. General Principles & Basic Science
In deformity correction principles, if an opening wedge osteotomy is performed at a level distant to the Center of Rotation of Angulation (CORA) but the mechanical axes are subsequently realigned, what is the expected geometric result at the osteotomy site?
Correct Answer & Explanation
. Translation of the bone ends
Explanation
According to Paley's rules of deformity, performing an osteotomy at a level different from the CORA and realigning the mechanical axis will inherently result in translation of the bone segments.
Question 3905
Topic: Surgical Anatomy & Approaches
A 24-year-old female with developmental dysplasia of the hip undergoes a Bernese periacetabular osteotomy (PAO). Through the standard Smith-Petersen approach, which osteotomy is typically performed first and requires fluoroscopy to ensure it is incomplete and does not enter the joint?
Correct Answer & Explanation
. Incomplete ischial osteotomy
Explanation
The incomplete ischial osteotomy is typically the first bone cut in a Bernese PAO. It is performed just distal to the acetabulum, leaving the posterior column intact, and requires fluoroscopy to avoid intra-articular penetration.
Question 3906
Topic: 1. General Principles & Basic Science
When utilizing a Taylor Spatial Frame to correct a complex multiplanar deformity, the surgeon must input specific parameters into the software. The "mounting parameters" specifically refer to which of the following?
Correct Answer & Explanation
. The diameter of the rings and the length of the struts
Explanation
Mounting parameters describe the exact position of the reference ring in relation to the origin (the reference point on the bone, usually the CORA). This includes AP, lateral, and axial translation and angulation offsets.
Question 3907
Topic: Biomechanics & Biomaterials
Which of the following statements is true regarding articular cartilage?
Correct Answer & Explanation
. The hydrophilicity of type II collagen molecules gives cartilage its viscoelastic properties
Explanation
The one role of collagen in articular cartilage is to provide the structural framework to resist swelling under high osmotic tissue pressures created by aggrecan. Type II collagen is the predominant type in articular cartilage.Proteoglycans, the most common of which is aggrecan, are produced by chondrocytes and give articular cartilage its hydrophilic properties. Multiple glycosaminoglycans (GAGs), such as chondroitin and keratin can attach to core proteins to form aggrecans. Link proteins then help aggrecans interact with hyaluronic acid. The negative charge of this complex helps create a strong osmotic gradient, which attracts water and increases tissue pressures. Normal aging involves a decrease in the water content of the extracellular matrix while osteoarthritis is associated with increased water content, which leads to loss of strength and elasticity.Chen et al. evaluated the strain and depth related properties of articular cartilage in bovine models. They found that the zero-strain permeability, zero-strain equilibrium confined compression modulus, and deformation dependence constant differed among the layers of cartilage. They suggest that the complex strain-dependent properties of articular cartilage of different thickness and location have clinical implications for tissue engineering.Illustration A is a diagram depicting the extracellular matrix of articular cartilage. Incorrect Answers:
Question 3908
Topic: Infection, Pharmacology & VTE
Clinical staging of osteomyelitis using the Cierney-Mader classification system takes into account which of the following factors?
Correct Answer & Explanation
. Host status and extent of infected bone
Explanation
DISCUSSION: The Cierney-Mader classification system takes into account host status (A: healthy, B: comorbidities, C: treatment morbidity > infection) and the extent of infected bone (type I: medullary, type II: superficial, type III: localized, type IV: diffuse).
Question 3909
Topic: Biology, Genetics & Bone Healing
Intermittent daily administration of recombinant parathyroid hormone (rhPTH) is an FDA-approved treatment for osteoporosis. Intermittent rhPTH treatment targets which of the following cells in osteoporotic patients?
Correct Answer & Explanation
. Osteoclasts
Explanation
PTH is an anabolic agent that enhances osteoblastic bone formation on both cortical and cancellous surfaces. It is synthesized in the parathyroid glands as a 115 amino acid precursor and is cleaved into the active 84 amino acid form. The biological activity in the clinically used recombinant PTH is in the 1-34 amino acid sequence at the N-terminus of the molecule. There are PTH receptors expressed by osteoblasts that mediate the anabolic bone response to intermittent PTH administration. Chronic elevation of PTH leads to stimulation of osteoclasts, producing bone loss.
Question 3910
Topic: Infection, Pharmacology & VTE
Hip pain of 1-month duration has developed in a 72-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/ฮผL (reference range 4,500 to 11,000 cells/ฮผL) 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
. Poorer prognosis for eradication of infection than that associated with infection 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-resistant Staphylococcus epidermidis organisms treated with a two-stage protocol, the failure rate was 21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of California Los Angeles Activity Score, and the 12-item Oxford Knee Score, however.
Question 3911
Topic: Infection, Pharmacology & VTE
The figure below shows the abdominal radiograph obtained from a 70-year-old woman who experiences nausea and abdominal tightness 48 hours following left total knee arthroplasty performed under general anesthesia. She received 24 hours of cefazolin antibiotic prophylaxis and a patient-controlled analgesia narcotic pump for pain management. She has been receiving warfarin for thromboembolic prophylaxis. Her severe abdominal distension and markedly decreased bowel sounds are most likely secondary to the administration of
Correct Answer & Explanation
. narcotics.
Explanation
DISCUSSION: The radiograph reveals severe intestinal dilatation, which has occurred as the result of acute colonic pseudo-obstruction and is associated with excessive narcotic administration following total joint arthroplasty. Anesthetic type, antibiotic administration, and warfarin have not been associated with this obstruction. Electrolyte imbalances such as hypokalemia have been associated with postsurgical acute colonic pseudo-obstruction.
Question 3912
Topic: 1. General Principles & Basic Science
A study is being designed to compare the effectiveness of an antibiotic. The choice of the number of patients (i.e., the sample size) depends on several factors. What type of calculation assesses the potential of the study to successfully address the effectiveness of the antibiotic?
Correct Answer & Explanation
. Power analysis
Explanation
Power analysis is used to determine the minimum number of specimens (sample size) such that, if a difference is found that is large enough to be clinically important, the associated level of statistical reliability will be high enough for the investigators to conclude that the difference observed in the study also holds in general.
Question 3913
Topic: 1. General Principles & Basic Science
When compared with cobalt-chromium and stainless steel implants, a titanium implant has what biomechanical properties?
Correct Answer & Explanation
. Lower modulus of elasticity
Explanation
DISCUSSION: Titanium implants are commonly used in spinal surgery, especially when MRI may be needed after implantation. Titanium implants have a lower modulus of elasticity when compared with cobalt-chromium and stainless steel implants. This is felt to allow less stress shielding for these types of implants. The other properties do not apply to titanium implants.
Question 3914
Topic: 1. General Principles & Basic Science
While experts disagree whether the postpolio syndrome is caused by a reactivation of the dormant virus or by an attritional aging phenomena of muscles that have been overworked over a period of time, both groups recommend which of the following guidelines for optimizing function in this population?
Correct Answer & Explanation
. Exercise daily at a subexhaustion level.
Explanation
DISCUSSION: Most leaders in orthopaedic surgery support Jacqueline Perryโs theory that the postpolio syndrome is an attritional degenerative process that is the result of overuse of muscles and joints that are unable to adequately tolerate overload, and have little functional reserve. For that reason, aerobic conditioning and exercise are important. Overload and exhaustion of involved muscles should be avoided.
Question 3915
Topic: 1. General Principles & Basic Science
A study was conducted in 500 patients to measure the effectiveness of a new growth factor in reducing healing time of distal radial fractures. The authors reported that average healing time was reduced from 9.2 to 8.9 weeks (P < 0.0001). Because the difference was highly statistically significant, they recommended routine clinical use of this drug despite its high cost. A more appropriate interpretation of these results is that they are
Correct Answer & Explanation
. statistically significant but perhaps not clinically significant.
Explanation
DISCUSSION: The results are statistically significant (at the arbitrary level of P < 0.05). However, because the statistical power of a study increases with the number of subjects included (sample size), a difference that is trivial clinically can occur with a very high level of statistical significance if enough patients are included in the study. Because of this, the P-value alone, no matter how small, does not establish clinical significance or importance. In this example, the reduction in healing time of only a few days is probably clinically unimportant.
Question 3916
Topic: 1. General Principles & Basic Science
Which treatment is associated with decreased complications related to femoral nerve blocks for TKA?
Correct Answer & Explanation
. Knee immobilizer
Explanation
DISCUSSION: TKA among elderly patients can be problematic, considering their potential for complex comorbidities including diminished cognitive function. As patients age, their tolerance for certain medications diminishes. Regional anesthesia is an important adjunct to a multimodal pain program, which can reduce narcotic pain medication use and improve cognitive function through less reliance on systemic medications. With regional pain management such as femoral nerve blocks comes potential for an increase in complications such as falls. Femoral nerve blocks improve pain but also have a large impact on quadriceps and motor function, which places patients at higher risk for falls. (Note: The provided options do not directly address the reduction of falls associated with femoral nerve blocks; however, based on standard orthopedic literature, none of these options are the primary solution, but the question implies a search for a specific clinical association.)
Question 3917
Topic: Biology, Genetics & Bone Healing
A tendon repair is thought to be weakest during which phase of tendon healing?
Correct Answer & Explanation
. Inflammatory
Explanation
Healing after a tendon repair or rupture has the following stages: inflammatory, cellular proliferation, and remodeling. During the inflammatory phase, neutrophils and macrophages migrate into the injury site and release chemotactic factors that recruit fibroblasts. A tendon is thought to be weakest 5 to 21 days after repair, which coincides with the inflammatory phase. During the proliferative phase, inflammatory cells secrete cytokines and growth factors (platelet-derived growth factor, insulin-like growth factor, bone morphogenetic protein (BMP)-12 and BMP 13, and transforming growth factor-beta) that promote differentiation of fibroblasts. Fibrosis and decreased cellularity are the hallmarks of the remodeling stage.
Question 3918
Topic: 1. General Principles & Basic Science
During an anterior approach to the bicipital tuberosity, you encounter a nerve overlying the brachioradialis fascia (Figure 58). It provides innervation to the
Correct Answer & Explanation
. skin on the anterolateral forearm.
Explanation
DISCUSSION: The structure shown is the lateral antebrachial cutaneous nerve (LABC). It is the terminal sensory branch of the musculocutaneous nerve and runs superficial to the brachioradialis. It supplies sensation to the anterolateral surface of the forearm. The flexor pollicis longus is innervated by the anterior interosseous nerve. The extensor indicis proprius is innervated by the radial nerve. The LABC does not innervate the skin of the anteromedial forearm. Careful identification and protection of this nerve is critical to prevent the most common nerve injury during distal biceps repair.
Question 3919
Topic: 1. General Principles & Basic Science
Figures 40a and 40b show the pre- and postoperative radiographs of an 82-year-old woman with bilateral hip pain who has had staged total hip arthroplasties. To minimize potential injury to the sciatic nerve at the time of surgery, the surgeon should
Correct Answer & Explanation
. perform a femoral shortening.
Explanation
To improve hip biomechanics and secure more suitable bone for acetabular fixation, the true acetabulum is often resurfaced in patients who have developmental dysplasia of the hip, thus lowering the hip center and lengthening the leg. Acute lengthening of more than 3 cm will place excessive tension on the sciatic nerve and require a femoral shortening to avoid sciatic nerve injury. The other maneuvers will not relieve sciatic nerve tension because of limb lengthening.
Question 3920
Topic: 1. General Principles & Basic Science
A 22-year-old male undergoes an inside-out meniscal repair for a longitudinal tear of the posterior horn of the medial meniscus. Which of the following neurovascular structures is at the highest risk of injury during the placement of the posterior incision for suture retrieval?
Correct Answer & Explanation
. Common peroneal nerve
Explanation
During an inside-out repair of the medial meniscus, an accessory posteromedial incision is made between the medial head of the gastrocnemius and the posterior capsule to retrieve the needles. The saphenous nerve and its infrapatellar branch are at highest risk during this approach and must be protected. The common peroneal nerve is at risk during a posterolateral approach for a lateral meniscal repair.
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