1. General Principles & Basic Science MCQs

The association of a nail puncture wound with a gram-negative infection (Pseudomonas aeruginosa) has been attributed to the local environmental factors in shoes.

The history and laboratory findings are consistent with osteomyelitis of the patella. The radiograph reveals bone destruction in the patella; therefore, the next most appropriate step is open biopsy and debridement of the site. Aspiration of the knee joint may be needed to rule out septic arthritis prior to patellar debridement. With this amount of bone destruction, surgical debridement is helpful to obtain cultures and to remove necrotic material. Administering antibiotics without any prior culture increases the risk of negative cultures later and a potentially incorrect choice of antibiotic. A neoplasm should be included in the differential. It would be inappropriate to initiate chemotherapy and radiation therapy without a biopsy-confirmed diagnosis. A bone scan is likely to demonstrate uptake, but radiographs have already localized the abnormality to the patella.

The MRI scan shows a posterior horn medial meniscus root avulsion with bony edema at the tibial root insertion. The radiograph shows no significant degenerative changes. If left untreated, posterior meniscal root tears lead to progressive degenerative changes as a result of the altered tibiofemoral contact pressures and areas. Nonsurgical treatment including injections, physical therapy, and unloader braces are more appropriate in the older patient with pre-existing advanced degenerative changes.

Rivaroxaban is a selective factor I0a inhibitor. Aspirin is a cyclooxygenase inhibitor. Low-molecular-weight heparin is a nonspecific anticoagulant. Warfarin is a vitamin K antagonist and reduces production of clotting factors II, VII, IX, and X.

According to the 2008 AAOS Clinical Practice Guideline, Treatment of Osteoarthritis of the Knee (Nonarthroplasty), level 1 evidence confirms that weight loss and exercise benefit patients with knee osteoarthritis. The other responses have either inclusive evidence (a valgus-directing brace) or no evidence to support their use (glucosamine 1,500 mg/day and chondroitin sulfate 800 mg/day as well as arthroscopic debridement and lavage).

Calcitonin is a hormone that reduces serum calcium concentration by directly interfering with osteoclast maturation via receptors. Calcitonin inhibits phosphate reabsorption and decreases calcium reabsorption in the kidneys. By attenuating cartilage breakdown and stimulating cartilage formation via inhibitory pathways of matrix metalloproteinases, calcitonin also has a chondro-protective effect on articular cartilage. Calcitonin has no major effects on intestinal absorption of calcium, but may aid in small-bowel secretion of sodium, potassium, chloride, and water. Calcitonin also has no receptor effect on osteoblasts.

The confidence interval provides you a range of values that with a given level of confidence (usually 95%) contains the truc value. The confidence interval also reflects the limitations of data presented (i.e. if no sepsis occurred during a two year follow-up of THR, should we believe there will never be any recurrences of sepsis rate if we perform a hundred of these exchanges in the future.) Confidence internals are also essential when presenting long-term results based on survivorship curve. Without confidence intervals the picture presented to the readers can be misleading. In these cases more data are needed before any proelic (?) statements can be made.

DISCUSSIONChronic exertional compartment syndrome (CECS) is an uncommon cause of pain that is most often encountered in athletes or military populations. The diagnosis is suggested by pain after the start of the activity with resolution of symptoms when the activity stops. Traditionally, the diagnosis was established by measuring intracompartment pressures at 1 and 5 minutes ofactivity. Roscoe and associates have shown that using continuous pressure monitoring during the activity until pain forces subjects to stop provides higher sensitivity and specificity than the traditional diagnostic technique. Palpating the leg is not as sensitive or specific as direct pressure monitoring. Although certain changes can be seen on MRI in CECS, this is not the diagnostic study of choice.

Discussion: Burks and Schaffer described an approach to the tibial insertion of the posterior cruciate ligament that uses the interval between the semimembranosus and the medial gastrocnemius. The medial gastrocnemius muscle is retracted laterally and protects the neurovascular bundle.

The development of a bacterial biofilm is a 2-stage process. The first step is the adhesion of individual bacteria to a substrate regulated by adhesions. After several bacteria have attached, quorum sensing (cell-to-cell communication) allows maturation of the biofilm and expression of genes that activate virulence factors. This can also increase the antibacterial resistance of the bacteria. Planktonic bacteria are individual free-moving bacteria.

The Chi-square test is most appropriately used for comparing proportions of categorical or ordinal data.When considering which statistical test to use the investigator must consider how many groups are being compared, and if the data collected is numerical or categorical, and parametric or non-parametric. When the study is comparing proportions of categorical data the appropriate test will be either a Chi-square test, or a Fisher exact test. The Fisher exact test is preferred when there is less than 5 data points in any group being compared.Illustration A is a flow chart demonstrating how to determine which statistical test is most appropriate.Incorrect answers:with the Mann-Whitney U test Answer 3: Comparing means of parametric data between 3 or more groups is best done with Analysis of variance (ANOVA) Answer 5: Comparing proportions of categorical data between groups when at least one group has less than 5 samples or data points is best done with the Fisher exact test

Discussion: From proximal to distal, the brachial plexus is divided into roots, trunks, divisions, and cords before forming specific peripheral nerve branches. The structure marked Q is called the posterior cord because it lies posterior to the axillary artery at the level of the cords.

Muscle lacerations immobilized for 2 weeks would likely experience significant muscle atrophy affecting final functional outcome. For muscle injuries, including partial lacerations, current literature suggests the affected extremity should be immobilized no more than 3-5 days, followed by a progressive strengthening and stretching program. Healing a muscle injury involves two competing processes: regeneration of muscle fibers and formation of granulation tissue. Starting motion too soon after injury may increase the area of fibrous scar and limit the ability of new muscle fibers to penetrate this area. Prolonged immobilization limits scar production, but penetrating muscle fibers will lack appropriate orientation, and the muscle as a whole begins to atrophy. Three to 5 days of immobilization has been shown to limit scar tissue production while the early motion helps generate appropriately organized muscle fibers and maintain strength and range of motion. Järvinen et al. present a review of muscle injury and healing. They found that immediate mobilization led to a large area of dense scar tissue that regenerating muscle fibers could not adequately penetrate. Prolonged immobilization allowed muscle fibers to regenerate but they lacked appropriate morphology. Following 3-5 days of immobilization, they found less scar tissue, better penetration of regenerated muscle fibers, and the regenerated fibers were more well aligned with the uninjured fibers surrounding them. Menetrey et al. present a mouse model of muscle laceration comparing a short period of immobilization (5 days) to suture repair of the muscle. They found quicker healing and greater strength in the suture repair group. Tetanus strength at one month after injury was (compared to an uninjured control) 81% for sutured muscle, 35% for the early mobilization only group, and 18% for the prolonged immobilization group.

In farm or soil-contaminated wounds, including lawnmower injuries, penicillin is added to broad-spectrum cephalosporin and aminoglycoside therapy to cover against Clostridium. Psuedomonas is frequently seen after puncture wounds through the shoes. Acinetobacter is generally a hospital-acquired infection.

Halo fixation is the most rigid form of cervical orthosis but complications can arise from improper placement of the fixation pins. A relatively safe zone for anterior pin placement is located 1 cm above and within the lateral third of the superior orbital rim. This position avoids the supraorbital and supratrochlear nerves over the medial one third of the orbit. The more lateral positions in the temporal fossa have very thin bone and can interfere with the muscles of mastication.

Atrial fibrillation is responsible for approximately 80% of all upper extremity emboli. All other cardiac conditions listed can cause upper extremity emboli; however, atrial fibrillation is the most common cause. Patients with an upper extremity embolic event should undergo prompt evaluation, with a careful history and physical examination as well as focused laboratory tests for hypercoagulability. Arterial Doppler studies or angiography are warranted. Electrocardiogram and echocardiogram are also used to evaluate for potential cardiac abnormalities. Treatment usually involves anticoagulation, embolectomy if necessary, and treatment for any recognized cardiac abnormality.

This patient with hemophilia A is presenting with an intramuscular hematoma surrounding the iliacus muscle which is likely to cause femoral nerve compression. Paresthesias would be expected in the L4 nerve distribution.Excessive bleeding into joints and muscles is a common manifestation of hemophilia. The iliacus muscle is a frequent site of hemorrhage in patients with severe or moderate hemophilia. Intramuscular hematoma of the iliacus muscle is likely to occur following play or sporting events that include forceful contraction of the hip flexor muscles. As the hematoma expands, it maycompress the adjacent femoral nerve, potentially resulting in complete femoral nerve palsy. Femoral nerve compression typically includes paresthesias in the distribution of the terminal saphenous nerve branch.Gilbert et al. review the complex relationship between recurrent bleeding, synovitis, and the development of arthritis in the patient with hemophilia. They discuss both conservative and surgical treatment modalities in these patients and recommend arthroscopic synovectomy for the knee and ankle joints. They conclude that the greatest risk to these procedures is a decreased range of motion.Kuo et al. reports on a fourteen-year-old healthy boy with an 11-day history of pain and weakness in the right lower limb following a fall. They report pain in the right lower extremity, numbness of the anterior aspect of the right thigh and medial border of the right leg and foot, inability to ambulate andweakened quadriceps muscle strength. MRI revealed an iliacus hematoma with a complete femoral nerve palsy. He underwent CT-guided percutaneous drainage for decompression with complete resolution of the palsy.Illustration A is a diagram of dermatomal distribution. Illustration B shows the lumbar plexus demonstrating the intimate relationship of the femoral nerve to the iliacus muscle.Incorrect Answers:A 45-year-old male trauma patient presents with multiple extremity injuries including the foot injury shown in Figure A. The foot fracture is treated surgically, and heals without any initial complications. At a minimum of 12 months, this patient will be expected to have which of the following scores compared to aPatients with pauciarticular juvenile rheumatoid arthritis (JRA), specifically the subgroup with elevated antinuclear antibody (ANA) titers, are associated with the highest incidence (~75%) of anterior uveitis. As a result, referral for an ophthalmology consultation is recommended.Pauciarticular JRA is the most common subgroup of JRA and typically presents between the ages of 2 to 4 years with mild swelling of one to four joints. The diagnosis is typically one of exclusion as laboratory studies, including erythrocyte sedimentation rate and rheumatoid factor, are usually within normal limits. In JRA, iridocyclitis, a type of anterior uveitis typically occurs following the onset of synovitis but may precede the joint symptoms. This iridocyclitis is frequently indolent but requires immediate ophthalmologic consultation for a slit-lamp examination because if left untreated, anterior uveitis may progress to loss of vision.Foeldavri et al. review JRA anterior uveitis. They report an overall incidence of10%, but this is dependent on the JRA subtype. They noted that a large proportion of children with JRA develop uveitis in the first year of disease and90% after 4 years. They state that early age of JRA onset, oligoarticular subtype, and ANA reactivity are the main risk factors for the development of uveitis. They conclude that JRA-associated uveitis is important to recognize and treat early to prevent any visual damage.Hawkins et al. review bilateral chronic anterior uveitis in JRA. They report that female gender, oligoarthritis, and presence of antinuclear antibodies are risk factors.They report on treatment options, including the use of biologics. They conclude that stepwise immunomodulatory therapy is indicated, with new biologic drugs being used in cases of refractory uveitis.Incorrect Answers:Anterior 4: Pompe disease is a glycogen storage disease which may lead to ptosis (drooping of the upper eyelid), not anterior uveitisA 9-year-old male with hemophilia A presents with severe groin pain, parasthesias over the medial aspect of the distal tibia, and difficulty ambulating several hours after a soccer game. He is believed to have an intramuscular hematoma surrounding the iliacus muscle. Which nerve is MOST likely to be compressed?Which of the following conditions places the patient at highest risk for anterior uveitis and necessitates referral to an ophthalmologist?Salmonella is a classic cause of osteomyelitis in patients with sickle cell disease.Sickle cell disease is a genetic disorder of hemoglobin synthesis. The disease occurs in two phenotypes: sickle cell anemia (most severe) and sickle cell trait (most common). The two most common causes of osteomyelitis in children with sickle cell disease areStaphylococcus aureus and Salmonella. Although S. aureus is the most common cause of osteomyelitis in the general population, the literature varies on which is the most common in patients with sickle cell disease. The increased risk in these patients may be associated with gastrointestinal microinfarcts, poor circulation of blood in bone, and splenic infarcts that predispose patients to infection by encapsulated bacteria (i.e., Salmonella).Piehl et al. analyzed records of seven hundred seventeen patients with sickle cell disease treated over a thirteen-year period. They identified and retrospectively reviewed sixteen cases of osteomyelitis in fifteen patients. The authors found Salmonella to be the causative organism in thirteen cases with Proteus mirabilis, Escherichia coli, and Staphylococcus aureus all affecting one patient each. The authors report the annual incidence of osteomyelitis in their series as 0.36%.Givner et al. reviewed sixty-eight cases of osteomyelitis in children with sickle cell disease and positive cultures over a ten year period. Of the sixty-eight, 50 (75%) yielded Salmonella and Staphylococci was isolated 7 (10%). Inaddition, the authors report non-speciated gram-positive cocci were isolated in11 (16%), non-speciated gram-negative rods in 5 (7%), and non-specified bacteria in 2 (3%). The authors conclude Salmonella is the most common pathogen causing osteomyelitis in patients with major sickle hemoglobinopathies.Epps et al. reviewed fifteen patients with sickle cell disease and osteomyelitis. Staphylococcus aureus was isolated in eight cases (53%), Salmonella in six (40%), and Proteus mirabilis in one (7%). The authors conclude S. aureus, not Salmonella, may be the most common cause of osteomyelitis associated in patients with sickle-cell disease.Figure A demonstrates an osteolytic lesion of the distal tibia and Figure F demonstrates sickle-shaped erythrocytes.Incorrect AnswersLow toughness is a disadvantage of ceramic bearings in total hip arthroplasty.Ceramic is a non-metal that demonstrates excellent wear characteristics when used with polyethylene in total hip arthroplasty. Although it has a high Young's modulus, it has a low fracture toughness. Subsequently, ceramic is poorly resistant to crack formation. In contrast, UHMWPE has a high fracture toughness because of the presence of very long hydrocarbon chains.Santavirta et al. review alternative bearing materials to improve wear in total hip arthroplasty. Alumina ceramics are noted to be biostable and bioinert. The best wear properties are noted with ceramic-on-ceramic bearings. For current ceramic constructs, fracture risk is less than 1 per 1000.Lang et al. review the use of ceramics in total hip replacement. The authors note that ceramic has high compressive strength and high wettability. Low fracture toughness and linear elastic behavior increase the risk of breakage of ceramic components under stress. Processing improvements, enhanced head- neck interfaces and liner modifications have lead to a decrease in the rate of ceramic fracture.Illustration A shows a compromised ceramic head as a manifestation of the low fracture toughness of the material.Incorrect Answers:An 8-year-old African American female presents with lower extremity pain and subjective fever. On exam there is tenderness about the distal tibia. Further workup reveals elevated inflammatory markers and a lytic lesion (Figure A). An aspirate is obtained and cultures grow Salmonella. Additional investigation is most likely to reveal which of the following findings (Figure B-F)?An ideal fluid film lubrication regime minimizes friction. A larger head size results in a greater development of full-film lubrication due to the increased relative sliding velocity of the larger bearing surfaces. Increased surface roughness inhibits the formation of the film lubrication. The most important factor influencing the predicted lubrication film thicknesshas been found to be the radial clearance between the ball and the socket.Jin et al report that slight clearance, not complete congruence, is optimal for formation of the optimal fluid film lubrication. They note that full fluid film lubrication may be achieved in these hard/hard bearings provided that the surface finish of the bearing surface and the radial clearance are chosen correctly and maintained.Dumbleton reviewed the literature of metal-on-metal THA and concluded that the current literature does not show any clinical benefit of metal-on-metal compared to metal on poly. Metal-on-metal has been shown to have higher metal ion level in blood, and measurement of these levels is recommended to help identify those at risk of adverse effects from metal on metal prostheses.Low toughness is a disadvantage of which of the following bearing surfaces used in total hip arthroplasty?This attending did not fully disclose that the resident would be performing the cementing portions of the case unsupervised. This represents an ethically unsound scenario as the patient was misled regarding involvement of the resident in their surgery.The informed consent process is grounded in the ethical principle of autonomy. Informed consent represents a shared decision making process where apatient understands all the risks and benefits of a surgery fully and makes an informed decision. However, the patient's choice of surgeon is felt to be criticalto the informed consent process and any variation from that surgeon performing the surgery should be discussed explicitly. A surgeon who performs surgery or part of surgery on the patient without prior consent may be held liable for battery.Kocher presents three cases demonstrating the spectrum of "ghost surgery". They state the substitution of an authorized surgeon with an unauthorized surgeon or allowing surgical trainees to operate without appropriate guidance constitutes "ghost surgery".Deviation from what is explicitly discussed has been justified in an emergency scenario or if the treatment is aimed at an overall condition.Bhattacharyya et al reviewed malpractice claims for factors that positively correlated with successful defense. They found that those who performed informed consent in the office had lower risk of malpractice payment. They conclude surgeons can decrease their risk of malpractice claims by performing informed consent in the office and documenting the discussion.Incorrect Answers:Which of the following features of metal-on-metal total hip arthroplasty does not allow for improved fluid film lubrication between the components?The patient sustained a fragility fracture with lab work consistent with primary hyperparathyroidism.Hyperparathyroidism is commonly caused by increased activity of the parathyroid glands resulting in high levels of PTH. Increased circulating levels of PTH leads to calcium being "sucked" out of bone and into the serum. Thisalteration in calcium hemostasis leads to low-density bone and a predisposition to fragility type fractures. When present, lab values are much different from standard age-related osteoporosis. Furthermore, referral to medical and surgical endocrinology specialists for directed treatments may improve overall bone quality and prevent further fragility fractures.Fraser summarizes primary and secondary hyperparathyroidism. He describes the normal physiologic response to low calcium of an increase in PTH. Increased PTH has three downstream effects of increased tubular resorption of calcium by the kidneys, increased osteoclast activity to harvest calcium from bone, and increased active vitamin D levels leading to increased bowel absorption of calcium.Singhal et al. reviewed hyperparathyroidism and what the orthopedic surgeon should know. They state when a patient presents with a pathologic fracture and elevated serum calcium levels, an appropriate lab workup for hyperparathyroidism should be done. They stated when surgery is needed for hyperparathyroidism and fracture, surgery can safely be performed simultaneously as demonstrated by 3 case examples.Figure A exhibits a left femoral neck fracture, which is a fragility fracture associated with poor bone density. Illustration A is a figure from Fraser's article exhibiting thefeedback loop from the hypothalamus, pituitary, adrenal/glandular axis.Incorrect answers:Prior to undergoing a total knee arthroplasty at an academic medical center a patient is told during informed consent by the attending surgeon that resident involvement in the case will be limited to retracting. During the case the attending is present up to trialing of the selected components. The surgeon leaves prior to cementing to start trialing components in another case while the chief resident remains alone in the room for the completion of the case. Which of the following is true regarding the ethics of this practice?Patients in factorial randomized control trials (RCT) are assigned to groups that receive a specific combination of interventions and non-interventions.In factorial RCTs, patients are randomized to groups receiving treatment A and B, treatment A or control, treatment B or control, or no treatment. This study design is useful because two interventions can be assessed with the samestudy population and any interaction between the treatments can be determined (for example, does treatment A work differentially when combined with treatment B). Other randomized control trial designs include parallel, cluster, and crossover. Parallel studies are performed by having two or more groups that exclusively have one intervention without group overlap.Crossover studies have each group receive each intervention in a random sequence. Cluster design studies have pre-existing groups of participants(such as schools, or cities) that are randomly selected to receive or not receive an intervention.Karlsson and the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine published an exhaustive guide to research for evidence-based medicine in a step-wise fashion. They cover levels of evidence, design for randomized control trials and the CONSORT checklist. They also describe proper study design of cohort, case- control, case series, systematic review, meta-analysis studies. The second half of the guide discusses appropriate outcome measures, statistical analyses, and data interpretation, reporting complications, and concludes with steps to writing a scientific article.Incorrect Answers:A 66-year-old woman falls from standing and sustains the injury shown in Figure A. Her most recent T score was -1.9, 3 months prior to presentation. Preoperative lab work reveals elevated serum calcium, elevated alkaline phosphatase, decreased serum phosphorus, and elevated parathyroid hormone (PTH). Which of the following correctly describes the underlying etiology of her osteopenia?The most recent update of the CDC guidelines for the prevention of SSI issues a category IA strong recommendation stating that "in clean and clean- contaminated procedures, do not administer additional antimicrobial prophylaxis doses after the surgical incision is closed in the operating room, even in the presence of a drain."The previous 2002 CDC guidelines for the prevention of SSI focused on three performance parameters: (1) initiation of parenteral antibiotics within 1 hour of the surgical incision, (2) selection of an appropriate antibiotic, and (3) discontinuation of antibiotics within 24 hours. The most recent updated 2017CDC guidelines for the prevention of SSI has several notable changes with an emphasis that additional doses of antibiotics after initial prophylaxis are no longer recommended.Berrios-Torres et al. review the 2017 updates to the CDC guidelines for prophylaxis against SSI. Strong recommendations include that in clean and clean-contaminated cases, additional antimicrobial prophylaxis should not be administered after the surgical incision is closed in the operating room, even in the presence of a drain. Furthermore, the authors discuss that there is no evidence that re-dosing intraoperative antibiotics or continuation of antibiotics until surgical drains have been removed provides any additional protection against surgical site infection.O'Hara et al. highlights the key updates in the most recent CDC guidelines for prevention of SSI. The authors present specific suggestions for translating these recommendations into evidence-based policies and practices. They conclude that the implementation of new and existing guidelines in SSI prevention requires thoughtful and careful collaboration with several inter- professional and interdisciplinary teams.Incorrect Answers:Which of the following study designs describes a randomized controlled trial in which two interventions are applied separately or in combination to study groups?The patient has an allergy to cephalosporins and a history of an MRSA infection. Of the choices listed, vancomycin is the best preoperative antibiotic for this patient.The choice of preoperative antibiotics is of great interest given the largemedical and economic cost of periprosthetic infections. Standard preoperative prophylaxis in patients undergoing total joint arthroplasty consists of cefazolin or cefuroxime. In patients with beta-lactam allergies, the treatment options include clindamycin or vancomycin. Vancomycin is often the antibiotic of choice given it's higher efficacy with regard to MRSA prevention. In those patients who are considered at risk for MRSA infection and a beta-lactam allergy, vancomycin can be supplemented with an aminoglycoside (gentamicin) or aztreonam.Bratzler et al. review antimicrobial prophylaxis for surgery and state for orthopedic joint replacement procedures cefazolin or cefuroxime is the recommended antibiotic. For patients with a confirmed beta-lactam allergy, they recommend vancomycin or clindamycin. They also state antibiotics should be stopped within 24hrs after surgery.Dellinger et al. review antibiotics for surgical prophylaxis. They state the standard antibiotics for orthopedic procedures are cefazolin or cefuroxime. They state if there is also a concern for MRSA infection vancomycin can be added in addition to the above antibiotics.Incorrect Answers:Which of the following is STRONGLY recommended by the most recent (2017) Centers for Disease Control and Prevention (CDC) Guidelines with regard to antimicrobial prophylaxis for the prevention of surgical site infection (SSI)?Clindamycin is a bacterial protein synthesis inhibitor by inhibiting ribosomal translocation at the 50S subunit.Clindamycin is primarily bacteriostatic but may be bactericidal at higher concentrations.Side effects of clindamycin may include a hypersensitivity reaction and pseudomembranous colitis. Resistance to clindamycin is conferred by a plasmid that alters the 50s ribosome binding site for clindamycin. The D- zone test is used to determine whether an organism has inducible resistanceto clindamycin.Marcotte and Trzeciak published a review on community-acquired methicillin- resistant Staphylococcus aureus (CA-MRSA). They reported that CA-MRSAdoes not have predictable susceptibility to clindamycin. They conclude that clindamycin also presents a risk for the development of Clostridium difficile colitis and inducible clindamycin resistance for which a D-zone test should be performed when culture results reveal erythromycin resistance.Steward et al. performed a lab study to determine the efficacy of testing for induced clindamycin resistance in erythromycin-resistant Staphylococcus aureus. They reported that resistance to erythromycin and clindamycin can occur through methylation of their ribosomal target site (50s), which is mediated by erm genes. They conclude that disk diffusion is the preferred method for testing S. aureus isolates for inducible clindamycin resistance.Incorrect Answers:A 68-year-old man is scheduled to undergo total hip arthroplasty. He states he had an anaphylactic reaction after taking cefazolin for an MRSA hand infection 10 years ago. Which of the following best describes the preoperative antibiotic that should be administered for this patient?Advanced glycation end-products (AGEs) cause excessive cross-linking of collagen in aging articular cartilage. As a result, the stiffness is increased.AGEs are produced by spontaneous nonenzymatic glycation of proteins when sugars (glucose, fructose, ribose) react with lysine or arginine residues. The most abundant matrix protein in cartilage is Type II collagen. AGEs cause changes to the aging cartilage matrix and the aging chondrocyte. The increased cross-linking of Type II collagen results in an increase in cartilage stiffness (i.e. increase in the modulus of elasticity) and an increase in brittleness (i.e. less strain needed to go from the yield point to the fracture point on the stress-strain curve). As a result of the change in the aging cartilage’s biomechanical properties, it's susceptible to fatigue failure. Additionally, AGEs decrease the anabolic response of chondrocytes from autocrine signaling via TGF-beta, IGF-1, BMP-7, and OP-1. These two initial mechanisms contribute to aging cartilage to eventually lead to the development of osteoarthritis.Li et al. reviewed age-related changes in cartilage and seek to define the differentmechanisms between aging cartilage and osteoarthritis. They state that with AGEs, there is excessive collagen cross-linking increases cartilage stiffness, while shortening/degradation of aggrecan leads to loss of sugar side chains and water-binding ability. Additionally, increased levels of AGEs are associated with a decline in anabolic activity. They state that these changes to cartilage make it more vulnerable to damage and therefore the onset of osteoarthritis. This is contrast to the initial steps in the mechanism of osteoarthritis which is characterized by cell proliferation, formation of chondrocyte clusters, increased synthesis of irregular cartilage matrix, and eventually a pro-catabolic and pro-inflammatory state that results in an imbalance in cartilage homeostasis and cartilage matrix breakdown.Anderson et al. reviewed the relationship between osteoarthritis and aging.They state that knee cartilage thins with aging, especially on the femoral and patellar sides, suggesting a gradual loss of cartilage matrix. AGEs formation leads to modification of type II collagen by cross-linking of collagen molecules, increasing stiffness and brittleness and increasing susceptibility to fatigue failure. Furthermore, describe the senescent phenotype of the chondrocyteand its similarities with osteoarthritic chondrocyte phenotype.Incorrect Answers:Which of the following antibiotics works by binding to the 50S ribosomal subunit?The patient has clinical signs and symptoms of gout. Figure D would correspond to this diagnosis as it shows negatively birefringent needle-shaped monosodium urate crystals.Gout is an idiopathic disorder of nucleic acid metabolism that leads to hyperuricemia and deposition of monosodium urate crystals, most commonly in the joints of the lower limb (knee, ankle, and classically the 1st metatarsophalangeal joint). Diagnosis can be confirmed with joint arthrocentesis revealing negatively birefringent needle-shaped crystals. Treatment of acute gout flares is generally comprised of NSAIDs and colchicine, and chronic gout is treated with allopurinol to prevent the build-upof uric acid.Shmerling et al. prospectively analyzed the synovial fluid test results of 100 consecutive patients undergoing diagnostic arthrocentesis. They noted that synovial fluid white blood cell count (WBC) and the percentage of polymorphonuclear cells performed well as discriminators between inflammatory and noninflammatory diseases. Given the diagnostic value of synovial WBCs, the authors concluded that ordering of chemistry studies of synovial fluid should be discouraged because they are likely to provide misleading or redundant information.Chiodo et al. review the use of intra-articular aspiration and injections for both diagnosis and treatment of disorders of the lower extremity such as infectious arthritis, gout, pigmented villonodular synovitis (PVNS), rheumatoid arthritis, and hemophilia. The authors discuss the importance of knowledge of regional anatomy, procedural indications, and appropriate techniques for successful aspiration/injection. The authors review safe and effective aspiration and injection techniques for the lower extremity, including the hip, knee, foot, and ankle.Figure A reveals hemosiderin stained multinucleated giant cells consistent with PVNS. Figure B is a gram stain revealing gram-positive cocci in clusters consistent with Staphylococcus aureus. Figure C reveals rhomboid-shaped, positively birefrigerant crystal consistent with calcium pyrophosphate/pseudogout. Figure D reveals negatively birefringent needle- shaped crystals of monosodium urate/gout. Figure E reveals a collection of histiocytes and inflammatory cells around prominent intimal hyperplasia.Incorrect AnswersAn increase in advanced glycation end-products (AGEs) is characteristic of which of the following clinical conditions and results in which pathologic process?Regardless of the number of level I studies included in a systematic review, having one study with <80% follow-up decreases the level of evidence for this review from level I to level II.After classifying the type of study (e.g. therapeutic study, prognostic study, diagnostic study, economic analysis, or decision analysis) the “level of evidence” is then determined. The level of evidence (on a scale of I through V) for medical research is determined. It is important to consider the characteristics of a study’s design. This would include the percent follow-up, utilization of a control group, presence of blinding, heterogeneity of results, and process of randomization. Specific to meta-analyses and systematic reviews, it is important to know that the lowest quality study used in the review determines the level of evidence. In evidence-based medicine, higher levels of evidence have a larger impact on clinical recommendations.Bhandari et al. analyzed the interobserver agreement among reviewers in categorizing the type of study, level of evidence, and subclassification for different clinical studies. The authors had 6 different surgeons with different levels of training in epidemiology analyzed 51 separate papers published in JBJS. The results demonstrated that the interobserver absolute agreement for the type of study and the level evidence was 82% and 67%, respectively. The epidemiology-trained reviewers had nearly perfect agreement in categorizing the type of study, level of evidence, and subclassification.Wright et al. published an editorial introducing the different types of study designs and defined the different levels of evidence. Illustration A is a figure from this editorial.Incorrect Answers:A 55-year-old male, alcoholic, presents to the ER with acute right knee swelling and pain x 3 days. He admits to prior episodes of this pain that resolve after a few days. Serum labs reveal an ESR of 40 mm/hr and CRP of 5 mg/dl. He undergoes right knee aspiration and based on the results, he is discharged home on colchicine with the presumed diagnosis of gout. Which of the following images of the aspiration results are consistent with this diagnosis?conclude that the patient populations and outcomes measure are homogenous and you do not have any concerns with randomization. You notice one ofthe studies included had 70% follow-up, yet the remaining studies had>80% follow-up. Knowing this, you appropriately assign what level of evidence to the systematic review?The correct sequence of events should be the surgeon reads the surgical information on the consent to the patient, then the surgeon marks the surgical site with the patient’s assistance, then allows the anesthesia team to perform their procedure, and then performs a final Time-Out with the surgical team immediately prior to the surgical incision.Orthopedic surgical patients are at risk of surgical errors due the number of procedures that can be performed on the bilateral extremities. The responsibility to identify the correct surgical procedure at the correct location has expanded beyond only the surgeon. The entire surgical team isresponsible for confirming the patient, surgical site, and surgical procedure. All members on the surgical team should be valued and emboldened to “speak up’ and actively participate. To help improve communication and reduce complications, surgical safety checklists have become common. In a statementpublished by the AAOS is 2015, they support the use of standardized surgical systems, including the use checklists, as it is critically important to keep patients safe. In 1998, the AAOS introduced the “Sign Your Site” safety program to reduce wrong-site surgeries through improved site identification. Permanent ink should be used to mark the site(s) with the patient's assistance prior to surgery, and the site(s) should be confirmed by the surgical team during the Time-Out immediately before the start of the surgical procedure.Singer et al. performed a study to evaluate the association between surgical teamwork and surgery safety checklist performance. Their results emphasized the importance of surgeon buy-in and clinical leadership to initiating and maintaining surgical safety checklists. In addition to surgeon buy-in and clinical leadership, factors that help maintain high-quality and consistent surgical teamwork were communication, coordination, respect, and assertiveness.Incorrect Answers:You are reviewing a systematic review on the 90-day complication rate and outcome for same day total joint arthroplasty for publication. After you analyze the methodology of the 6 randomized controlled trials included in the review, youpreoperative paperwork outside the room. The patient is taken to surgery and receives an interscalene block on the left shoulder after sedation. At the final Time- Out, the surgeon realizes a discrepancy with the laterality when the consent is read aloud. The surgeon aborts the case and wakes the patient. What is the correct sequence of events that should have happened to prevent this error? A: The surgeon beginsthe surgery B: The surgical team performs a Time-Out C: The surgeon marks the surgical site D: The surgeon reads the surgical information on the consent to the patient E: The anesthesia team administers a local extremity blockEnchondral ossification occurs with relative stability constructs, which is represented by the bridge plate in figure C.Fracture healing is a complex process that occurs in several key steps. The type of healing that occurs is dependent on the stability and strain of the fracture environment. In constructs with very little strain, also referred to as absolute stability, there is primary bone healing through Haversian remodeling. This produces very little callus and does not rely on a cartilage precursor. Relative stability constructs with higher strains produce a cartilage precursor, which subsequently ossifies in later stages of healing, also referred to as enchondral ossification.Perren reviewed the biological mechanisms of fracture healing. The author discussed the importance of skeletal stiffness for limb function in addition to the healing process that utilizes soft tissue compensatory mechanisms to aidin fracture healing. The author concluded that the goal of fracture healing is to obtain a functional limb to allow for daily mobility and activity.Gerstenfeld et al. investigated the effect of non-selective and COX-2 selective NSAIDs effects on bone healing in a rat model. They reported a significantly higher nonunion rate in valdecoxib treated rats compared to the ketorolac group. They also noted that withdrawal of either drug at six days resulted in prostaglandin E2 levels returning to normal levels after 14 days. The authors concluded that COX-2 specific NSAIDs inhibited bone healing greater than nonspecific NSAIDs with the magnitude of the effect dependent on the duration of treatment, but the effects on prostaglandin E2 levels appear reversible with discontinuation of the drug.Figure A is the AP radiograph of the left distal tibia with three lag screws through a spiral fracture. Figure B is the lateral radiograph of the right elbow with an olecranon plate.Figure C is the AP radiograph of the right distal femur with a lateral bridge plate. Figure D is an AP radiograph of the left ankle with a lag screw and neutralization plate on the distal fibula. Figure E is the lateral radiograph of the forearm with a compression plate on the radius.Incorrect Answers:A 31-year-old man is scheduled to undergo a right shoulder arthroscopic labral repair. The surgeon is running behind and hurries to the preoperative holding area. The surgeon greets the patient and verbally confirms the operative site with the patient. The surgeon leaves the patient’s room and completes the appropriateThe yield point is the transition point between elastic and plastic deformation. The yield strength is defined as the amount of stress necessary to produce a specific amount of permanent deformation.Stress is the amount of force applied to a material and strain is the deformation resultingfrom that stress. This is graphically depicted as a stress- strain curve, where the X-axis represents strain and the Y-axis represents stress. The elastic modulus of a material is the linear region of the graph (rise over run/stress on strain). Remember, an elastic material is one that resists a change in shape (less strain or deformation under increasing stress). Non- linear regions include the toe region for some materials (tendons/ligaments) and the plastic zone, which occurs after the yield point.Mantripragada et al. provide a review of recent advances in designing orthopaedic implants. Of note, they discuss modifications to metallic implants to reduce unwanted effects, such as nickel-free stainless steel. They also go over newer alloys with desirable mechanical and biological properties, such as tantalum, niobium, zirconium, and magnesium.Kennedy et al. provide a classic in-vitro tension study of the human knee ligaments. They used an Instron Tension Analyzer to test the ultimate failure of the medial collateral, lateral collateral, anterior cruciate, and posterior cruciate ligaments at different loading rates. They found that the posterior cruciate ligament was the strongest (the other ligaments were all ofcomparable strength) and that microscopic failure occurred before macroscopic failure. Illustration A represents a stress-strain curve.Incorrect Answers:is a phenomenon especially associated with a ductile material; the diameter of the material is diminished prior to fracture.material can absorb before fracture and is the area under the stress-strain curve. Answer 5: The toe region is seen in materials such as ligaments and tendons and represents the straightening of the crimped ligament fibers.Which of the following fixation constructs would achieve fracture healing through enchondral ossification?The preosteoclast (precursor to the osteoclast) is the only cell of myeloid origin. The remainder of the cells involved in bone formation, remodeling, and metabolism are of mesenchymal origin.Osteoclast signaling, function, and biology have grown increasingly well understood over the past few decades. Osteoclast activity is regulated byosteoblasts, thereby coupling bone formation and resorption. Osteoclast differentiation from myeloid precursor cells is stimulated by key molecules including RANK, PU-1, and CSF-1. An understanding of these molecular pathways is essential to developing effective directed anti-resorptive therapies.Zaidi et al. present a comprehensive review of proliferation, differentiation, and hormonal regulation of cells of the bone. The authors specifically discuss the unique origin of the osteoclast from the myeloid lineage and conversely the mesenchymal origin of the osteoblast. Furthermore, they highlight themost recent understanding of the molecular mechanisms involved in osteoclast formationand signaling, including M-CSF and RANKL.Caterson et al. discusses mesenchymal differentiation in the context of musculoskeletal regeneration. The authors review the growth factors and bioactive signaling molecules involved in directed differentiation itno the various mesodermal lineages including bone, cartilage, muscle, tendon, marrow, and adipose. They emphasize the importance of understanding these pathways to regenerative medicine.Illustration A is a diagram illustrating the difference between mesenchymal and myeloid lineages.Incorrect answers:The point on a stress-strain curve that separates the plastic and elastic regions is defined as which of the following:Due to the risk of inducible clindamycin resistance in erythromycin-resistant MRSA, a D-test should be performed.Isolates of MRSA that are resistant to erythromycin have been shown to become resistant to clindamycin through a process called inducible resistance, which is conferred by a plasmid that alters the 50S ribosome binding site for both clindamycin and erythromycin. Thus, when culture results reveal erythromycin-resistant MRSA, a D-zone test should be performed to check for inducible clindamycin resistance. The D-zone test is performed byplacing an erythromycin disk in proximity to a clindamycin disk on an agar plate inoculated with methicillin-resistant S aureus (MRSA). A zone of inhibition in the shape of the letter "D" is seen with an inducible strain and is considered a positive test. If the D- zone test is positive, then clindamycin should not be used because the strain of MRSA can become resistant to the treatment.Marcotte et al. published a review on community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). They reported that clindamycin has activity against Streptococcus species, but it is not as predictable against CA- MRSA. Clindamycin also presents a risk for the development of Clostridium difficile colitis and inducible clindamycin resistance. for which a D-zone test should be performed when culture results reveal erythromycin resistance.Steward et al. performed a study to determine the efficacy of testing for induced clindamycin resistance in erythromycin-resistant Staphylococcus aureus. They reported that resistance to erythromycin and clindamycin can occur through methylation of their ribosomal target site (25), which is typically mediated by erm genes. They found that disk diffusion is the preferred method for testing S. aureus isolates for inducible clindamycin resistance.Illustration A is an image of a positive D-zone test, which indicates inducible clindamycin resistance.Incorrect Answers:Which of the following cells involved in bone metabolism derives from a myeloid origin?Enoxaparin primarily exerts its effects by inhibiting Factor Xa, which is labeled C in Figure A.Enoxaparin is a low molecular weight heparin (LMWH) that primarily exerts its effects by inhibiting Factor Xa. It achieves this by binding to antithrombin to form a complex that irreversibly inactivates clotting factor Xa. Enoxaparin has the advantage of not requiring laboratory monitoring and can be reversed with protamine sulfate. However, it is important to note that protamine sulfate is less effective in reversing enoxaparin compared to unfractionated heparin (UFH).Hyers published a review on the past, present, and future management of venous thromboembolism. He found that, for the most part, LMWH and other newer anticoagulants have been shown to be superior to UFH in terms of the venographic endpoint. He also reports that several meta-analyses have demonstrated that LMWH offers superior benefit to UFH for VTE prevention in hip and knee surgery patients.Tørholm et al. performed a study to determine outcomes of thromboprophylaxis using LMWH compared to placebo in elective hip surgery. They found that 9 (16%) patients in the treatment group and 19 (35%) in the placebo group developed deep venous thrombosis. The risk of thrombosis in the placebo group was increased with prolonged surgery and occurred more frequently during the first 4 postoperative days. They concluded that LMWH offers safe and easily administered thromboprophylaxis in total hip replacement.Figure  A  is an image  of  the coagulation  cascade.  Illustration A is an image     of  thecoagulation cascade with the sites of action of the various anticoagulants labeled.Incorrect Answers:A 42-year-old IV drug user presents to the emergency department with a large abscess on his forearm. A bedside I&D is performed and he is started on broad-spectrum IV antibiotics. Initial results from his cultures demonstrate methicillin-resistant Staphlycoccus aureus (MRSA) that is also resistant to erythromycin. The team would like to transition him to oral clindamycin. Prior to transitioning him to clindamycin, which additional laboratory test should be performed?Teriparatide promotes bone formation in patients at high risk of fractures due to severe osteoporosis that is refractory to multiple treatments, including bisphosphonates and cement augmentation. Teriparatide is a human recombinant N-terminal parathyroid hormone.Teriparatide administered in daily injections results in bony formation, whereas continuous infusion results in bony resorption. In rat models, teriparatide caused an increase in the incidence of osteosarcoma, and thus should only be prescribed for patients for whom the potential benefits outweigh the potential risk. It can be administered in isolation or as an adjunct treatment during bisphosphonate therapy. However, in patients on long-term bisphosphonate therapy, discontinuation of bisphosphonates are advised to reduce potential complications of atypical femur fractures and jaw osteonecrosis.Watts et al. published a review article on postmenopausal osteoporosis. They reported that bisphosphonates can accumulate in bone, thus after a period of treatment, lower- risk patients should be offered a drug holiday. Denosumab, on the other hand, is not sustained when treatment is discontinued, so no drug holiday is warranted. They concluded that, although there are safetyconcerns regarding atypical femoral fracture and osteonecrosis of the jaw with long term use, the benefit of hip fracture risk reduction far outweighs the risk of these relatively uncommon side effects.Song et al. performed a meta-analysis to investigate the effect of teriparatide monotherapy and the additive effect of teriparatide on antiresorptive agents in postmenopausal women with osteoporosis. They reported that teriparatide monotherapy significantly improved bone mineral density (BMD) in the lumbar spine, total hip, and femoral neck compared with placebo; the additive effectof teriparatide over hormone replacement therapy (HRT) and denosumab agents was evident in all 3 skeletal sites; however, teriparatide plus alendronate did not demonstrate additive effect in total hip and femoral neck. They concluded that, for patients with osteoporosis who were at high risk for fracture, BMD increased more in patients receiving teriparatide than in those receiving alendronate.Saag et al. compared the use of teriparatide or alendronate in the management of glucocorticoid-induced osteoporosis. They reported that BMD had increased more in the teriparatide group than in the alendronate group in the lumbar spine and total hip at 6 and 12 months, respectively. They also reported significantly fewer new vertebral fractures in the teriparatide group compared to the alendronate group. They concluded that in severely osteoporotic patients at high risk for fracture, BMD increased more in patients receiving teriparatide than in those receiving alendronate.Figure A depicts multiple vertebral insufficiency fractures in the setting of a prior cement augmentation procedure.Incorrect Answers:Where in the coagulation cascade shown in Figure A does enoxaparin primarily exert its effects?This patient is presenting with signs of a septic nonunion after open reduction and internal fixation (ORIF) of a radial shaft fracture. Of the choices listed, C- reactive protein (CRP) is the best predictor of infection in the setting of nonunion.Nonunions after fracture fixation may occur from infection. The most sensitive and readily-available laboratory marker to detect infection is the CRP. CRP is an acute phase reactant that significantly rises within 6 hours after tissue damage or onset of clinical infection. CRP then peaks 2-3 days later and returns to normal levels 5-21 days after the inciting event if it is treated (e.g. antibiotics for cellulitis). In septic nonunions, the chance of fracture healing is low if the infection is not properly treated, and chronic infection can lead to substantially elevated CRP values.Wang et al. evaluated the effectiveness of laboratory tests in the diagnosis ofinfected nonunion. They reported that the sensitivity and specificity of CRP for detection of infected nonunions are both higher than those of IL-6. They concluded that the diagnostic utility of CRP was superior to IL-6, which is contrary to similar studies comparing these markers in prosthetic joint infection patients.Stucken et al. performed a study to investigate the utility of a standardized protocol to rule out infection in high-risk patients and to evaluate the efficacy of each component of the protocol. They reported that the ESR and the CRP levels were both independently accurate predictors of infection. Theyconcluded that their protocol can help surgeons to risk-stratify patients prior to the surgical treatment of a nonunion, allowing them to counsel patients more appropriately.Figure A depicts a nonunion of a radial shaft fracture after ORIF. Incorrect Answers:An 85-year-old woman presents with severe back pain and the CT shown in Figure A. Her history is notable for prior vertebral compression fractures for which she underwent a cement augmentation procedure. She has been on bisphosphonates for the last 5 years, without improvement of her osteoporosis. She has no history of malignancy. What is the mechanism of action of the medication that should be prescribed for her refractory osteoporosis?A receiver operating characteristic (ROC) curve is used to determine responsiveness.Responsiveness is a measure of the diagnostic ability of different tests. It can be determined by calculating the C-statistic, which represents the area under aReceiver Operating Characteristic (ROC) curve. On a ROC curve, the false positive rate (1 - specificity) is plotted on the x-axis, while the true positive rate (sensitivity) is plotted on the y-axis. The higher the area under the curve, the more responsive the outcome measure. A value of 0.5 indicates a random chance and a therefore useless test, while values above 0.75 usually are considered to be adequately responsive.Kocher et al. published a review on clinical epidemiology and biostatistics for orthopaedic surgeons. They reported that the relationship between the sensitivity and specificity of a diagnostic test can be portrayed with use of a receiver operating characteristic (ROC) curve. A ROC graph shows the relationship between the true- positive rate (sensitivity) on the y-axis and the false-positive rate (1 − specificity) on the x-axis plotted at each possible cutoff. Overall diagnostic performance can be evaluated on the basis of the area under the ROC curve.Hanley et al. published a review on the meaning and use of the area under a receiver operating characteristic (ROC) curve. They reported that it represents the probability that a randomly chosen diseased subject is (correctly) rated or ranked with greater suspicion than a randomly chosen non-diseased subject.Illustration A is an example of a ROC curve. Illustration B is an example of a funnel plot. Illustration C is an example of a Kaplan-Meier curve. Illustration D is a table outlining the interpretation of the Cronbach alpha coefficient. Illustration E is an example of a forest plot.Incorrect Answers:A 32-year-old man underwent open reduction and internal fixation for an open radial shaft fracture 6 months ago. He is now experiencing fevers and chills at night and pain and swelling over the surgical site. A current radiograph is depicted in Figure A. What is the most accurate laboratory test for assessing his most likely diagnosis?The Patient-Reported Outcomes Measurement Information System (PROMIS) has been shown to have reduced floor and ceiling effects compared to other assessment tools.The PROMIS system was developed to produce a highly reliable, precise, and versatile assessment of outcomes. When administered in a computerized adaptive mode, each question that is answered is followed with a customized follow-up question based on the previous response, which allows for reduced testing items and time. Further, the results of the assessment are reported in T-scores with 50 being the population norm and with a standard deviation of

Creating an environment where all members of the healthcare team feel empowered to express their beliefs increases communication, the key element in decreasing sentinel events.Research has shown that 70% of sentinel event errors are caused by improper communication. Specific ways to improve communication include effective clinical handover between shifts and breaking down the "hierarchy" so that all members of the team can discuss their expectations and concerns. Barriers to effective communication include distractions, cultural differences, power distance relationships, time pressures, and lack of organization.Leonard et al. describe specific clinical experiences in the application of surgical briefings, properties of high reliability perinatal care, the value of critical event training and simulation, and benefits of a standardised communication process in the care of patients transferred from hospitals to skilled nursing facilities. They recommend embedding standardized tools and behaviors to bridge differences in communications styles between clinicians.Incorrect Answers:

Children with spina bifida and bilateral symmetrical dislocation of the hips usually do not require treatment. A level pelvis and good range of motion of the hips are more important for ambulation than reduction of bilateral hip dislocations. Because the patient has good sitting and standing balance and good range of motion, maintenance of that range of motion and symmetry is more important than reduction. Surgery is not recommended.

Anisotropic materials have mechanical properties that vary based on the direction of loading. The relative values of Young’s modulus for tendon, ligament, and bone are not relevant to isotropy. The mechanical properties of tendon do change with preconditioning, but this change is related to viscoelasticity. The intrinsic mechanical properties of tendon do vary with the rate of loading, but this variance is related to viscoelasticity.