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 3761
Topic: Biomechanics & Biomaterials
A 45-year-old active male has symptomatic isolated medial compartment osteoarthritis with a varus mechanical axis. A medial opening wedge high tibial osteotomy (HTO) is planned. To maintain native sagittal plane kinematics, where should the osteotomy gap be larger?
Correct Answer & Explanation
. Anterior cortex
Explanation
In a medial opening wedge HTO, the posterior gap should be approximately twice the anterior gap to maintain the native posterior tibial slope. Equal or larger anterior opening inappropriately increases posterior tibial slope, which can alter knee kinematics and load the ACL.
Question 3762
Topic: Infection, Pharmacology & VTE
A 25-year-old football player is diagnosed with a grade 3 medial collateral ligament (MCL) tear. MRI reveals the tear is located at the distal (tibial) insertion with the ligament flipped superficial to the pes anserinus. What is the most appropriate management?
Correct Answer & Explanation
. Hinged knee brace for 6 weeks
Explanation
A Stener-like lesion of the MCL occurs when the distal MCL avulses and flips superficial to the pes anserinus, preventing anatomic reduction and healing. This specific distal tear pattern is an indication for acute surgical repair.
Question 3763
Topic: 1. General Principles & Basic Science
A 50-year-old male presents with acute posterior knee pain after deep flexion. MRI demonstrates an extrusion of the medial meniscus >3mm and a defect at the posterior horn attachment. Which of the following best describes the biomechanical consequence of this injury?
Correct Answer & Explanation
. Increased contact pressure equivalent to a total meniscectomy
Explanation
Medial meniscus posterior root tears cause a complete loss of hoop stresses, leading to meniscal extrusion. This results in decreased contact area and increased peak contact pressures biomechanically equivalent to a total meniscectomy.
Question 3764
Topic: 1. General Principles & Basic Science
The anterolateral ligament (ALL) of the knee is increasingly recognized for its role in controlling rotational laxity. Where is the precise femoral origin of the ALL relative to the fibular collateral ligament (FCL)?
Correct Answer & Explanation
. Proximal and posterior to the FCL origin
Explanation
The femoral origin of the anterolateral ligament (ALL) is located proximal and posterior to the origin of the fibular collateral ligament (FCL) on the lateral femoral epicondyle.
Question 3765
Topic: 1. General Principles & Basic Science
A study is proposed in which 50 patients with osteonecrosis of the knee are compared with 23 patients without osteonecrosis in terms of their alcohol consumption levels. This is an example of what type of study?
Correct Answer & Explanation
. Case control
Explanation
In a case control study, all the subjects are selected based on whether they have (cases) or do not have (controls) the disease or outcome of interest. Case control studies are retrospective as they always look back to see how a certain risk factor may be different between the two groups. The main aspect of a cross-sectional study is that it is designed to look at a representative sample of the entire population of interest at a single point in time. Longitudinal studies follow groups of subjects over a period of time. A cohort study follows a particular group in relation to an event, studying them at intervals in time and uses objective outcome criteria. In a randomized controlled study, subjects are divided randomly into control and experimental groups to balance both the known and unknown differences between the groups.
Question 3766
Topic: Biomechanics & Biomaterials
When polyethylene is exposed to radiation and subsequently heated, certain chemical changes occur in the material. Which of the following statements best describes these changes?
Correct Answer & Explanation
. The process improves (lowers) the wear rate but may increase the risk of fracture.
Explanation
DISCUSSION: Exposure of polyethylene to radiation and then heating it to quench the free radicals leads to a cross-linked material. It converts a high molecular weight polyethylene macromolecule to an interpenetrating network structure of polymer chains. The ductility of the material is decreased, hence the greater risk of fracture. While the wear rate (measured as fewer and smaller particles) against a smooth counterface is markedly reduced, cross-linked polyethylene has shown a larger increase in wear rate when a rougher counterface is used compared to noncross-linked material. Due to reduced mechanical strength, highly cross-linked polyethylene is less resistant to abrasive wear. REFERENCE: Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 32-33.
Question 3767
Topic: 1. General Principles & Basic Science
The Mangled Extremity Severity Score (MESS) utilizes all of the following variables EXCEPT:
Correct Answer & Explanation
. Time from admission to surgery
Explanation
DISCUSSION: The MESS is a tool utilized to help predict limb salvage success versus primary amputation at the time of presentation. As a screening tool for amputation, this scoring system has a high specificity but low sensitivity, as scores lower than 7 may also ultimately need amputation. All of the variables except choice #4 (Time from admission to surgery) are part of the scoring system. The scoring system is as follows: 1. Skeletal / soft-tissue injury: Low energy = 1; Medium energy = 2; High energy = 3; very high energy = 4; 2. Limb ischemia: Pulse reduced or absent but perfusion normal = 1; Pulseless = 2; Cool, paralyzed, insensate = 3; 3. Shock: normotensive = 0; transient hypotension = 1; persistent hypotension = 2; 4. Age: < 30 = 0; 30-50 = 1; >50 = 2. Limb category scores are doubled for ischemia > 6 hours. The system's original designers reported a cutoff of 7 as predicting amputation.
Question 3768
Topic: Biology, Genetics & Bone Healing
What is the known manner in which the growth hormone-insulin-like growth factor-I (GH-IGF-I) system functions to stimulate bone growth?
Correct Answer & Explanation
. The products of the system induce proliferation without maturation of the growth plate and thus induce linear skeletal growth.
Explanation
DISCUSSION: IGF-I, formerly known as somatomedin-C, possibly acts by both paracrine and endocrine hormone pathways. The products of the GH-IGF-I system induce proliferation without maturation of the growth plate and thus induce linear skeletal growth. The action of the thyroid hormone axis is via an active metabolite that enters target cells and signals a nuclear receptor to stimulate both proliferation and maturation of the growth plate. Increased amounts of the active steroid hormone metabolite promote proliferation and maturation of the growth plate. Calcitonin inhibits bone resorption. REFERENCES: Binder G, Grauer ML, Wehner AV, et al: Outcome in tall stature: Final height and psychological aspects in 220 patients with and without treatment. Eur J Pediatr 1997;156:905-910. Wang J, Zhou J, Cheng CM, et al: Evidence supporting dual, IGF-I-independent and IGF-I-dependent, roles for GH in promoting longitudinal bone growth. Endocrinol 2004;180:247-255. Gertner JM: Childhood and adolescence, in Favus MJ (ed): Primer on Metabolic Bone Diseases and Disorders of Mineral Metabolism, ed 4. Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 45-47.
Question 3769
Topic: 1. General Principles & Basic Science
Successful healing of a meniscal repair is most likely associated with which of the following tear patterns?
Correct Answer & Explanation
. Vertical tear in the “red-red” zone
Explanation
The blood supply to the meniscus has been well documented, and is primarily limited to the horns and outer one third of the meniscus. Both animal and human studies have clearly demonstrated healing of tears in the outer one third of the meniscus. Arnoczky et al described the vascular supply to the meniscus and showed that tears within the outer one third of the meniscus have the best healing potential. Rim width is the most important prognostic factor for meniscal repairs; the vascular one third of the meniscus is most conductive to healing. Scott et al found better results when the tear was within 2mm of the meniscosynovial junction. Stone et al found improved healing with rim widths of 6mm or less. Tenuta et al found best results within a rim width of 3mm or less.
Question 3770
Topic: Surgical Anatomy & Approaches
In the anterior forearm approach to the distal radius (Henry approach), the radial artery is located between what two structures?
Correct Answer & Explanation
. Flexor carpi radialis and brachioradialis tendons
Explanation
DISCUSSION: The standard approach to the volar aspect of the distal radius is the Henry approach. Following incision of the skin and subcutaneous tissues, the forearm fascia is incised. The radial artery and venae comitantes lie in the interval between the tendons of the flexor carpi radialis muscle and the brachioradialis muscle. This interval is developed, and the radial artery and veins are retracted in a radial direction.
Question 3771
Topic: Biomechanics & Biomaterials
During total hip arthroplasty, what characteristic of irradiated (10 Mrad) and subsequently melted highly cross-linked polyethylene should provide a more wear-resistant construct than traditional gamma- irradiated (2.5-4 Mrad)-in-air polyethylene mated with the same head?
Correct Answer & Explanation
. Resistance to adhesive wear B. Resistance to abrasive wear C. Resistance to fatigue wear
Explanation
DISCUSSION:Highly cross-linked polyethylene makes material resistant to adhesive wear. Abrasive wear from third bodies does not decrease wear. The fatigue strength of such material is inferior to that of traditional polyethylene, and its resistance to creep is the same, if not lower, than that of traditional polyethylene.
Question 3772
Topic: 1. General Principles & Basic Science
An orthopaedic surgeon frequently uses hip and knee prostheses from a specific manufacturer. The surgeon becomes acquainted with the manufacturer's representative who provides the support for these prostheses in the hospital. They develop a personal relationship outside of work through a common interest in sailing. Together they become interested in buying a sailboat. The manufacturer's representative suggests a partnership in a boat costing $200,000. The manufacturer's representative would purchase a 90% interest and the surgeon a 10% interest in the boat. There would be no restrictions on use of the boat by the surgeon. What should the orthopaedic surgeon do?
Correct Answer & Explanation
. Accept the offer because it would allow the physician to have a boat and enjoy a hobby of sailing with a minimal financial outlay.
Explanation
Rejecting this proposal is the only appropriate course of action. Accepting it would, in essence, be receiving a huge gift from industry in the form of a sailboat. Physicians frequently assert that they are not influenced by gifts and relationships with industry representatives, but evidence is to the contrary. Such an arrangement constitutes a tremendous incentive to use the manufacturer's products. The fact that the boat partnership seems completely outside of the orthopaedic business relationship does not excuse it. Conflicts of interest should always be resolved and in the best interest of patient care, and in this case the best course clearly is to avoid the conflict of interest totally. An equal interest in the boat does not eliminate the conflict of interest.
Question 3773
Topic: Biology, Genetics & Bone Healing
0 sustained a subcapital fracture of her hip. She is an avid tennis player, and history reveals no previous fractures. What is the most appropriate follow-up care? Review Topic
Correct Answer & Explanation
. A repeat dual-energy x-ray absorptiometry scan (DEXA) and treatment if the T-score is less than -2.5
Explanation
A DEXA scan is most appropriately used to establish a baseline score. Even if the bone mineral density is not within the osteoporotic range (T-score less than -2.5), a prior fragility fracture is a strong risk factor for a second fracture as a result of factors other than bone density, such as worsening vision or balance, confusion, or other predispositions to falls. The guidelines of the National Osteoporosis Foundation indicate that, following a fragility hip fracture, active anti-osteoporotic medication should be initiated, whether or not a DEXA scan is performed. A recent study showed that antiresorptive therapy following a hip fracture reduces not only the risk of a second fracture but also overall mortality.
Question 3774
Topic: Surgical Anatomy & Approaches
Which of the following is considered the preferred approach to resect a lesion in the posterior one third of the proximal humerus?
Correct Answer & Explanation
. Between the lateral head of the triceps and the deltoid muscle
Explanation
DISCUSSION: At least 8 cm of the posterior aspect of the proximal region of the humeral diaphyseal cortex can be exposed through the interval between the lateral head of the triceps and the deltoid muscle. No nerves or blood vessels need to be exposed in the dissection. The deltoid muscle is innervated by the axillary nerve and the triceps muscle by the radial nerve. This is a true internervous plane. REFERENCE: Berger RA, Buckwalter JA: A posterior surgical approach to the proximal part of the humerus. J Bone Joint Surg Am 1989;71:407-410.
Question 3775
Topic: Infection, Pharmacology & VTE
A 65-year-old woman with type II diabetes mellitus (most recent Hgb A1C was 8.2) has had 3 days of left knee pain. Physical examination of the left knee reveals erythema, warmth and a large effusion. Range of motion is painful and limited to 30 degrees of flexion. She is found to be hypotensive and not responding to volume resuscitation. She requires phenylephrine to maintain Mean Arterial Pressure (MAP) of 70. ESR and CRP are elevated and Lactate is 3.1 mmol/L. What is the next best intervention for this patient’s treatment?
Correct Answer & Explanation
. Joint aspiration and blood cultures
Explanation
DISCUSSION: The patient is demonstrating signs of septic shock. Administration of antibiotics should not be delayed. Aspirating the knee joint and obtaining blood cultures can be rapidly accomplished to obtain accurate specimens. This should be followed immediately by administration of broad spectrum IV antibiotics. Patients with septic shock can be identified with a clinical construct of sepsis with persisting hypotension requiring vasopressors to maintain mean arterial pressure (MAP) ≥ 65 mmHg and having a serum lactate level > 2 mmol/L (18 mg/dL) despite adequate volume resuscitation. With these criteria, hospital mortality is in excess of 40%.
Question 3776
Topic: Infection, Pharmacology & VTE
What is the typical MRI signal intensity of bone marrow affected by acute osteomyelitis?
Correct Answer & Explanation
. Decreased on T1-weighted imaging, increased on T1-weighted imaging with gadolinium enhancement, increased on T2-weighted imaging
Explanation
DISCUSSION: The classic MRI findings of osteomyelitis are a decrease in the normally high signal intensity of marrow on T1-weighted images and normal or increased signal intensity on T2-weighted images. This is the result of replacement of marrow fat by inflammatory cells and edema, which causes lower signal intensity than fat on T1-weighted images and higher signal intensity than fat on T2-weighted images. The addition of gadolinium to a T1-weighted sequence reveals increased signal intensity in the hyperemic marrow.
Question 3777
Topic: Surgical Anatomy & Approaches
During the ilioinguinal approach to the pelvis, the corona mortis artery must be identified and ligated if present. The corona mortis artery joins the external iliac artery with which other major artery?
Correct Answer & Explanation
. Obturator
Explanation
DISCUSSION: The "corona mortis" (translated as “crown of death”) artery is a vascular variant that joins the external iliac and the obturator artery as it crosses the superior pubic ramus. The corona mortis can be injured in superior ramus fractures and iatrogenically while plating pelvic ring injuries using the ilioinguinal approach.
Question 3778
Topic: Biology, Genetics & Bone Healing
It has been shown that bisphosphonate-based supportive therapy (pamidronate or zoledronate) reduces skeletal events (onset or progression of osteolytic lesions) both in patients with multiple myeloma and in cancer patients with bone metastasis. The use of biphosphonate therapy has been associated with Review Topic
Correct Answer & Explanation
. increased medical complications of treatment.
Explanation
The use of bisphosphonates has been recently associated with the development of osteonecrosis of the jaw. Length of exposure seems to be the most important risk factor for this complication. The type of bisphosphonate may play a role and previous dental procedures may be a precipitating factor. Bisphosphonates are a class of therapeutic agents originally designed to treat loss of bone density (ie, alendronate). The primary mechanism of action of these drugs is inhibition of osteoclastic activity, and it has been shown that these drugs are useful in diseases with propensities toward osseous metastases. In particular, they are effective in diseases in which there is clear upregulation of osteoclastic or osteolytic activity, such as breast cancer and multiple myeloma, and have developed into a mainstay of treatment for individuals with these diseases. Although shown to reduce skeletal events, there has been no improvement in patient survival.
Question 3779
Topic: 1. General Principles & Basic Science
Up to what time frame are the risks minimized in anterior revision disk replacement surgery? Review Topic
Correct Answer & Explanation
. 3 days
Explanation
Revision anterior exposure within 2 weeks of total disk replacement incurs relatively little additional morbidity because adhesion formation is minimal. Surgeons should have a low threshold for revising implants that are clearly dangerously malpositioned or show early migration within this 2-week window. Beyond this time period, a revision strategy must be individualized to the particular clinical situation. A posterior fusion with instrumentation with or without a laminectomy is currently the most effective salvage procedure.
Question 3780
Topic: Surgical Anatomy & Approaches
Which of the following nerves supply the muscles on each side of internervous plane identified when performing the anterior (Smith-Petersen) approach to the hip?
Correct Answer & Explanation
. Femoral and obturator nerves
Explanation
The anterior (Smith-Peterson) approach to the hip utilizes the superficial internervous plane between the sartorius (femoral nerve) and the tensor fascia lata (superior gluteal nerve). The deep internervous plane is between the rectus femoris (femoral nerve) and the gluteus medius (superior gluteal nerve).
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