AAOS & ABOS Basic Science MCQs: Bone Biology & Anatomy

AAOS & ABOS Basic Science MCQs (Set 3): Bone Biology, Biomechanics & Anatomy Review

Comprehensive 100-Question Exam

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Question 1

What region of the thoracic curve is most dangerous for pedicle screw insertion while performing a posterior fusion for adolescent idiopathic scoliosis?

Explanation

Morphologic and anatomic studies confirm the pedicle is smaller on the concave side of thoracic curves. The dura is also closer to the pedicle on the concave side of the curves. Liljenqvist U, Allkemper T, Hackenberg L, et al: Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction. J Bone Joint Surg Am 2002;84:359-368.

Question 2

Plots of stress versus strain for four orthopaedic biomaterials are shown in Figure 3. Referring to the figure, what is the correct identification of the curves?

Basic Science 2006 Practice Questions: Set 3 (Solved) - Figure 1

Explanation

Stress-strain plots allow easy comparison of a number of important mechanical properties, including elastic modulus (the slope of the initial straight line portion of the curve) and yield stress (the stress at the break in the curves for bone, steel, and titanium alloy). Important considerations here are much lower modulus and ultimate stress of bone and cement compared to the two metallic alloys, the fact that titanium is lower modulus but higher strength than stainless steel, and the identification of cement as the only brittle material among the four. Burstein AH, Wright TM: Fundamentals of Orthopaedic Biomechanics. Baltimore, MD, Williams and Wilkins, 1994, pp 97-129.

Question 3

A 54-year-old woman underwent prophylactic intramedullary fixation for an impending fracture of her right femur secondary to metastatic breast cancer. A bone scan revealed a second lesion in her inferior pubic ramus. Her oncologist has recommended that she receive the intravenous bisphosphonate, zoledronic acid, because the medication would

Explanation

Bisphosphonates have been reported to reduce the incidence of new osseous lesions and prevent an increase in size of existing lesions. Zoledronic acid has been reported in clinical trials to decrease the skeletal complications of patients with multiple myeloma and with bone metastases from solid tumors. Results also have demonstrated that zoledronic acid delays the initial onset of bone complications by more than 2 months in patients with non-small-cell lung cancer and other solid tumors. In two placebo-controlled clinical studies of zoledronic acid conducted in patients with bone metastases from prostate cancer or other solid tumors, there was a decrease in the number of patients with skeletal-related events compared to placebo, and the time to the first skeletal-related event was delayed. Mundy GR, Yoneda T: Bisphosphonates as anticancer drugs. N Engl J Med 1998;339:398-400.

Question 4

What is the known manner in which the growth hormone-insulin-like growth factor-I (GH-IGF-I) system functions to stimulate bone growth?

Explanation

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. 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.

Question 5

During particle-induced osteolysis around implants, what cell secretes most of the interleukin-6 (IL-6)?

Explanation

During osteolysis, IL-6 is secreted by fibroblasts in the membrane surrounding the prosthesis. IL-6 also can be secreted by osteoblasts in other settings, but they are not the predominant source of IL-6 in particle-induced osteolysis. The remaining cells are not major sources of IL-6.

Question 6

What mechanism is associated with the spontaneous resorption of herniated nucleus pulposus?

Explanation

Nonsurgical modalities remain the mainstay for treatment of herniated disks. Spontaneous resorption of herniated disks frequently is detected by MRI. Marked infiltration by macrophages and neovascularization are observed on histologic examination of herniated disks, and the resorption is believed to be related to this process. Many cytokines such as vascular endothelial growth factor, tumor necrosis factor-alpha, and metalloproteinases have been implicated in this process, but none has been found to be singularly responsible. Haro H, Kato T, Kamori H, et al: Vascular endothelial growth factor (VEGF)-induced angiogenesis in herniated disc resorption. J Orthop Res 2002;20:409-415.

Question 7

A 68-year-old woman with metastatic breast carcinoma is seen in the emergency department. She appears lethargic, and she reports abdominal pain, nausea, and constipation. An EKG reveals a shortened QT interval. The only physical finding on examination is diffuse hyporeflexia. What is the most appropriate step in management?

Explanation

Intravenous fluid administration is the best first step to treat the hypercalcemia of malignancy. Many of these patients are dehydrated, and the increased serum calcium impairs the ability of the kidney to concentrate the urine. The decreased glomerular filtration rate secondary to the hypovolemia also leads to increased tubular resorption of calcium. The establishment of normovolemia will help promote increased urinary excretion of calcium. Lasix can also be used to help promote calciuria. Mithramycin is an antibiotic derived from Streptomyces plicatus. It is part of a group of drugs referred to as chromomycin antibiotics and is the only one of this group used clinically in the United States. It is rarely used in cancer chemotherapy because of its toxicity. A number of drug-related deaths have occurred from the use of mithramycin. Its use is now limited to the treatment of hypercalcemia associated with malignancy where it is used in lower dosage than that used for the treatment of tumors. Methotrexate has no role in the treatment of hypercalcemia of malignancy. While intravenous bisphosphonates are helpful in slowing progression of metastases and may help lower cerum calcium, they are not appropriate in the emergent treatment of hypercalcemia in the metastatic cancer patient.

Question 8

What is the primary role of superficial zone protein (SZP) in articular cartilage?

Explanation

Lubricin and SZP share a similar primary structure but may differ in posttranslational modifications with O-linked oligosaccharides. The primary physiologic function of SZP appears to be boundary lubrication. SZP does not influence interleukin-1, collagenase, or TIMP directly because these proteins are associated with articular cartilage turnover. Hlavacek M: The influence of the acetabular labrum seal, intact articular superficial zone and synovial fluid thixotropy on squeeze-film lubrication of a spherical synovial joint. J Biomech 2002;35:1325-1335.

Question 9

Clinical evidence suggests that grafts for replacing a torn anterior cruciate ligament often stretch after surgery. What is the most probable mechanism for this behavior?

Explanation

The stretching of the graft occurs over time as the graft is loaded. Time-dependent deformation under load is called creep and is common in viscoelastic materials such as ligament tissue. Creep can occur under both static and cyclic load conditions; time-dependent deformation will occur as long as load is applied to the tissue. Similarly, when a graft is initially tensioned to a given deformation at surgery, the load generated in the graft will decrease over time; this behavior is called stress relaxation and also is indicative of a viscoelastic material. Water content may affect the viscoelastic properties by changing the friction between collagen fibers, but studies have shown little difference in water content between grafts and normal ligaments. Fatigue failures may manifest themselves through damage to the ligament tissue, but this would require higher loads than are routinely experienced by grafts. Elastic stretch is recoverable and, therefore, does not contribute to a permanent stretch. Similarly, gross failure at the attachment would not cause a stretch, but rather a catastrophic instantaneous instability. Boorman RS, Thornton GM, Shrive NG, et al: Ligament grafts become more susceptible to creep within days after surgery. Acta Orthop Scand 2002;73:568-574. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 596-609.

Question 10

A 60-year-old man with diabetes mellitus is referred for evaluation of nonhealing ulcers of his left foot. Nonsurgical management has failed to provide relief, and a below-the-knee amputation is being considered. Which of the following studies best predicts successful amputation wound healing?

Explanation

The TcPO2 measures the O2 delivering capacity of the local vasculature. Values above 40 mm Hg have been shown to correlate with positive healing potential. The hemoglobin A1c is a good indicator of long-term glucose levels; however, it has no direct correlation with wound healing potential. Serum albumin is an indirect measure of nutritional status, and deficiencies in nutrition must be addressed before any surgery. Adequate hemoglobin levels are also necessary to promote adequate oxygenation to the amputation site. The ankle-brachial index may be falsely elevated as a result of calcified vessels in patients with diabetes mellitus. Wyss CR, Harrington RM, Burgess EM, et al: Transcutaneous oxygen tension as a predictor of success after amputation. J Bone Joint Surg Am 1988;70:203-207.

Question 11

The wear resistance of ultra-high molecular weight polyethylene can be improved by exposing the polymer to high-energy radiation (eg, gamma or electron beam), followed by a thermal treatment. What is one detrimental side effect of this process?

Explanation

Highly cross-linked polyethylene has gained widespread acceptance for joint arthroplasty components because of reported experimental and early clinical accounts of significant reductions in wear. Cross-linking is increased by imparting additional energy into the polymer (above that conventionally used for sterilization). The thermal treatments after cross-linking stabilize the material against oxidative degradation by quenching free radicals and also reduce the elastic modulus. One disadvantage of the increased cross-linking is a reduction in toughness that makes the polyethylene more susceptible to crack initiation and propagation. The reduced toughness raises concerns for gross component fracture and fracture at stress concentrations that can arise with the locking mechanisms used to secure polyethylene inserts into metallic backings. Nonconsolidated polyethylene particles have been associated with increased subsurface density secondary to oxidative degradation in conventional polyethylene implants. The quenching of free radicals by thermal treatment in highly cross-linked polyethylene should prevent this problem. Collier JP, Currier BH, Kennedy FE, et al: Comparison of cross-linked polyethylene materials for orthopaedic applications. Clin Orthop 2003;414:289-304. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 203-208.

Question 12

Which of the following best characterizes the antigenicity of allograft bone?

Explanation

Cell surface glycoproteins present in the heterogeneous population of the cells within the graft are primarily responsible for the antigenicity. Macromolocules of the matrix have also been implicated. Cryopreserved grafts have less antigenicity than fresh. Freezing, freeze-drying, or chemical sterilization and antigen extraction of the bone allograft have all been shown to reduce the antigenicity of the graft. Freeze-drying of retroviral-infected cortical bone and tendon does not inactivate retrovirus. Immunosuppression has been shown to decrease response. Hematopoietic elements along with osteogenic, chondrogenic, fibrous, and vascular cells have been shown to be antigenic. Crawford MJ, Swenson CL, Arnoczky SP, et al: Lyophilization does not inactivate infectious retrovirus in systemically infected bone and tendon allografts. Am J Sports Med 2004;32:580-586. Stevenson S, Li XQ, Davy DT, et al: Critical biological determinants of incorporation of non-vascularized cortical bone grafts: Quantification of a complex process and structure. J Bone Joint Surg Am 1997;79:1-16.

Question 13

Which of the following clinical disorders is the result of a mutation in fibroblast growth factor recepter 3 (FGFR3)?

Explanation

Camptomelic dysplasia is caused by a heterozygous loss of function of the Sox9 gene. The alternatives have genetic causes, but are not linked to Sox9. Cleidocranial dysplasia is related to a defect in Cbfa-1 (Osf-2, Runx2). Schmid metaphyseal chondrodysplasia is related to Type X collagen. Fibrous dysplasia is related to a defect in the alpha subunit of stimulatory guanine-nucleotide-binding protein (Gs). Achondroplasia is related to a defect in fibroblast growth factor receptor 3. Wagner T, Wirth J, Meyer J, et al: Autosomal sex reversal and camptomelic dysplasia are caused by mutations in and around the SRY-related gene SOX9. Cell 1994;79:1111-1120. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 111-131.

Question 14

Which of the following best characterizes bone mineralization?

Explanation

Mineralization occurs at the site of hole zones between the collagen fibrils. Crystals begin from the necessary ions of the lattice that come together with the correct orientation to form the first stable crystal. Formation of this critical nucleus is the most energy-demanding step of crystallization. Enzymes within the extracellular matrix vesicles degrade inhibitors such as adenosine triphosphate, pyrophosphate, and proteoglycans found in the surrounding extracellular matrix. Bone mineral consists of numerous impurities (carbonate, magnesium) that are more soluble, allowing the bone to act as a reservoir for calcium, phosphate, and magnesium ions. Crystals may form by addition of ions or ion clusters to the critical nucleus in many directions, with 'kink' sites forming to branch and exponentially proliferate the crystals. Macromolecules facilitate formation of the critical nucleus and increasing local concentrations of necessary ions. Once the crystals are formed and proliferating, macromolecules bind to the surface and block the growth of the crystal, regulating size, shape, and number of crystals. Lian JB, Stein GS, Canalis E, et al: Bone formation: Osteoblast lineage cells, growth factors, matrix proteins, and the mineralization process, in Favus MJ (ed): Primer on Metabolic Bone Diseases and Disorders of Mineral Metabolism, ed 4. Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 14-29.

Question 15

What is the main mechanism for nutrition of the adult disk?

Explanation

Disk nutrition occurs via diffusion through pores in the end plates. The disk has no direct blood supply, and the anulus is not porous to allow diffusion. The dorsal root ganglion does not provide blood supply to the disc. Biyani A, Andersson GB: Low back pain: Pathophysiology and management. J Am Acad Orthop Surg 2004;12:106-115. Urban JG, Holm S, Maroudas A, et al: Nutrition of the intervertebral disc: Effect of fluid flow on solute transport. Clin Orthop 1982;170:296-302.

Question 16

A study is conducted to measure the difference in bone mineral density between postmenopausal women taking a drug treatment versus those taking a placebo. What is the most important result to be reported from this study?

Explanation

A complete answer necessarily includes the means and standard deviations of bone mineral density in both groups. Given these, which are the basic results of the study, the P-value can be calculated if desired. All of the other options preclude assessment of the actual data, that is, the information collected by the study. P-values and confidence intervals should be perceived as additional information, which help to assess the certainty of relating the study's findings to the general population, but they should not be reported instead of the results (ie, the means and standard deviations).

Question 17

Figures 4a through 4c show the radiographs, CT scans, and T1-weighted MRI scan of a 19-year old man who has had increasing right hip pain and decreasing range of motion for the past several years. He also reports intermittent "locking" of the hip. What is the most likely diagnosis?

Explanation

The radiographs reveal small ossified masses around the femoral neck. The CT scans also show these masses and suggest that they are separate from the underlying cortex of the femoral neck, although they abut it. The MRI scan does not reveal significant marrow changes in the proximal femur apart from some mild reactive changes immediately adjacent to the nodules. These findings suggest a synovial or joint-based disorder as opposed to a primary bone tumor. The most likely diagnosis is synovial osteochondromatosis, which is consistent with the patient's mechanical symptoms. Crotty JM, Monu JU, Pope TL Jr: Synovial osteochondromatosis. Radiol Clin North Am 1996;34:327-342.

Question 18

The presence of S100B tumor marker typically corresponds with which of the following as being the most likely source of the metastasis?

Explanation

Advances in development of new tumor markers and techniques of antigen retrieval have enhanced the sensitivity and reliability of identifying the primary source of metastasis. New markers such as CK7, CK20, CA125, and thyroid transcription factor-1 (TTF-1) can help to determine the origin of an adenocarcinoma or aid in the recognition of other tumors. In patients who do not have an obvious primary site of disease or screening radiographs, these new markers can help focus the search for and guide the treatment of the underlying lesion. CA125 is positive in patients with ovarian cancer, CK7 is positive in patients with breast and lung carcinoma, and CK20 is indicative of colon carcinoma if the CK7 marker is negative. Gastrointestinal stromal tumor (GIST) is positive for CD117 (c-kit) and CD34, whereas 75% of bronchogenic carcinomas are positive for TTF-1. Histochemical staining of the S100 protein family has been used for many years in the diagnosis of malignant melanoma. Recent markers HMB-45, MART-1, and Melan-A have proved to be useful in diagnosis of melanoma. S100B protein has been implicated in downregulation of p53 (oncosuppressor gene). Harpio R, Einarsson R: S100 proteins as cancer biomarkers with focus on S100B in malignant melanoma. Clin Biochem 2004;37:512-518.

Question 19

Which of the following accurately describes the biosynthetic materials tricalcium phosphate (TCP) and hydroxyapatite?

Explanation

TCP is resorbed more rapidly, at a rate of 10 to 20 times faster than hydroxyapatite, partially because its larger pore size makes it a weaker substance. It provides significantly less compressive strength than hydroxyapatite. It does partially convert to hydroxyapatite, thus slowing its resorption rate. The absorbing cell of hydroxyapatite is the foreign body giant cell, not the osteoclast. Optimum pore size appears to be between 150 and 500 um. Lane JM, Bostrom MP: Bone grafting and new composite biosynthetic graft materials. Instr Course Lect 1998;47:525-534.

Question 20

A patient undergoes cartilage implantation requiring amplification of donor cells. Which of the following statements best describes the transplants?

Explanation

Chondrocytes are obtained from cartilage harvested from non-weight-bearing areas of the knee. The extracellular matrix is digested, and the chondrocytes are expanded for later transplantation. Cells implanted into a defect are secured with a flap of periosteum. Cells are expanded to obtain 20 to 50 times the original number of cells to transplant at a cell density of 3x10-7 cells/mL. There is a direct relationship between cell number and biosynthetic activity. Osteochondral lesions of up to 8 mm may be treated with autologous transplant alone; larger depth lesions should be bone grafted at the time of harvest. Mesenchymal stem cells differentiate easily into fibrous tissue, bone, and fat; conversion of mesenchymal stem cells into cartilage in vitro currently is difficult to accomplish. Goldberg and Caplan, however, were able to obtain cartilage repair using mesenchymal stem cells transplanted into defects in rabbits in vivo. In animal studies, fluorescent-labeled cells persist for at least 14 weeks, integrate with the surrounding normal margins, and become part of the repaired tissue replete with sulfated proteoglycans and type II collagen. Brittberg M, Peterson L, Sjogren-Jansson E, et al: Articular cartilage engineering with autologous chondrocyte transplantation. J Bone Joint Surg Am 2003;85:109-115.

Question 21

The load versus deformation curve of the functional spinal unit (FSU) is made up of the neutral zone, the elastic zone, and the plastic zone. What is the plastic zone of the curve believed to represent?

Explanation

Plastic deformation of viscoelastic tissues represents deformation of the soft tissues to the point of failure. The lining up of collagen fibers would be in the "toe region" of the curve, which, in the case of the FSU, would be mainly in the neutral zone. Elastin is a minor contributor to the composition of the ligaments and would be protected by the stiffer collagen fibers. The transition between flexion and extension occurs in the neutral zone, and reversible elongation occurs in the elastic zone. Fardon DF, Garfin SR, Abitbol J, et al (eds): Orthopaedic Knowledge Update: Spine 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 15-23.

Question 22

A knock-out mouse for the Vitamin D receptor has which of the following phenotypes?

Explanation

A knock-out mouse to the Vitamin D receptor would cause loss of vitamin D function, resulting in rickets. Renal failure would not occur; although Vitamin D is converted from 25 (OH) D to 1,25 (OH) D in the kidney, the active hormone acts on the gut and bone. Osteopetrosis can be seen as the phenotype for the c fos knock-out mouse; the Jansen-type metaphyseal dysplasia phenotype results from overactivation of the PTH/PTHrp receptor. Although compensatory hyperparathyroidism would occur, excessive PTH would not be able to rescue the skeletal loss and instead phosphoturia and phosphotasia would result. Glowacki J, Hurwitz S, Thornhill TS, et al: Osteoporosis and vitamin-D deficiency among postmenopausal women with osteoarthritis undergoing total hip arthroplasty. J Bone Joint Surg Am 2003;85:2371-2377.

Question 23

A 30-year-old woman injures her knee while skiing. Based on the MRI scan shown in Figure 5, treatment should consist of

Basic Science 2006 Practice Questions: Set 3 (Solved) - Figure 5

Explanation

The MRI scan demonstrates a grade III MCL tear. Basic science and clinical studies have shown that nonsurgical management is preferred for MCL tears. Functional rehabilitation and early motion have led to consistently better results than has surgical repair.

Question 24

Intramembranous ossification during fracture repair is characterized by absence of which of the following elements?

Explanation

Intramembranous ossification occurs through the direct formation of bone without the formation of a cartilaginous intermediate. Clinically, both intramembranous and endochondral ossification occur simultaneously during fracture healing; however, the latter is characterized by the differentiation and maturation of chondrocytes, vascular invasion of a hypertrophic cartilage matrix, and bone formation. Collagens type II and X are cartilage specific and would be characteristic of endochondral ossification, not intramembranous ossification. Li J, Sandell LJ: Transcriptional regulation of cartilage-specific genes, in Rosier RN, Evans C (eds): Molecular Biology in Orthoapedics, Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 21-24.

Question 25

Patients with rheumatoid arthritis may exhibit an increase in viral load for which of the following viruses?

Explanation

Rheumatoid arthritis (RA) is a complex multisystem disorder. It has been suggested that patients with RA have an impaired capacity to control infection with Epstein-Barr virus. Epstein-Barr virus has oncogenic potential and is implicated in the development of some lymphomas. Recent publications provide evidence for an altered Epstein-Barr virus-host balance in patients with RA who have a relatively high Epstein-Barr virus load. Large epidemiologic studies confirm that lymphoma is more likely to develop in patients with RA than in the general population. The overall risk of development of lymphoma has not risen with the increased use of methotrexate or biologic agents. Histologic analysis reveals that most lymphomas in patients with RA are diffuse large B cell lymphomas, a form of non-Hodgkin lymphoma. Epstein-Barr virus is detected in a proportion of these. Patients with RA do not have prevalence for infection with any of the other mentioned viruses. Callan MF: Epstein-Barr virus, arthritis, and the development of lymphoma in arthritis patients. Curr Opin Rheumatol 2004;16:399-405.

Question 26

A mutation in the gene encoding Carbonic Anhydrase II leads to an autosomal recessive form of osteopetrosis. Which of the following best describes the fundamental cellular defect resulting from this mutation?

Explanation

Carbonic anhydrase II generates protons that are pumped by vacuolar H+-ATPase into the resorption pit (Howship's lacuna). A defect prevents matrix acidification, which is essential for the dissolution of hydroxyapatite by osteoclasts.

Question 27

In orthopedic biomechanics, bending stiffness of a solid circular implant is proportional to the area moment of inertia. If the radius of a solid intramedullary rod is doubled, the bending stiffness increases by a factor of:

Explanation

The area moment of inertia for a solid cylinder is proportional to the radius to the fourth power (r^4). Therefore, doubling the radius (2^4) increases the bending stiffness 16-fold.

Question 28

Sclerostin, a glycoprotein produced primarily by osteocytes, is a critical regulator of bone formation and the target of the monoclonal antibody romosozumab. What is its mechanism of action?

Explanation

Sclerostin inhibits osteoblastogenesis and bone formation by antagonizing the Wnt signaling pathway. It specifically binds to the LRP5/6 co-receptors, preventing Wnt ligand binding and subsequent beta-catenin accumulation.

Question 29

To improve the wear characteristics of ultra-high-molecular-weight polyethylene (UHMWPE) for total joint arthroplasty, it undergoes highly cross-linking via irradiation followed by remelting. What is the primary biomechanical tradeoff of the remelting process?

Explanation

Remelting UHMWPE (heating above its melting point) effectively eliminates residual free radicals, significantly reducing long-term oxidation risk. However, it decreases the polymer's crystallinity, which subsequently lowers its yield strength and fatigue resistance.

Question 30

Articular cartilage is divided into specific structural zones. Which of the following best characterizes the superficial (tangential) zone of articular cartilage?

Explanation

The superficial zone has the highest water content, lowest proteoglycan content, and highly organized collagen fibers aligned parallel to the articular surface. It is specialized to resist shear forces.

Question 31

When comparing a slotted (open-section) intramedullary nail to an unslotted (closed-section) intramedullary nail of the same diameter and wall thickness, what is the primary biomechanical consequence of the slot?

Explanation

A closed-section (unslotted) tube has a much higher polar moment of inertia compared to an open-section (slotted) tube. Therefore, slotting significantly decreases the torsional rigidity of an intramedullary nail.

Question 32

During skeletal muscle excitation-contraction coupling, the release of intracellular calcium initiates the cross-bridge cycle. To which specific protein does calcium bind to facilitate this process?

Explanation

Calcium binds to Troponin C, causing a conformational change that moves tropomyosin away from the myosin-binding sites on the actin filament. Troponin I inhibits actin-myosin interaction, and Troponin T binds the troponin complex to tropomyosin.

Question 33

X-linked hypophosphatemic rickets (XLH) is the most common heritable form of rickets. What is the underlying pathophysiology of this condition?

Explanation

XLH is caused by a PHEX gene mutation, leading to unchecked levels of FGF-23. High FGF-23 causes renal phosphate wasting and downregulates 1-alpha-hydroxylase, leading to low 1,25-dihydroxyvitamin D.

Question 34

A surgeon plans to revise a fractured femoral plate but decides to mix a titanium locking plate with stainless steel screws. What is the primary concern regarding galvanic corrosion in this construct?

Explanation

In a galvanic cell with dissimilar metals, the less noble metal acts as the anode and undergoes corrosion. Titanium is highly noble and acts as the cathode, causing the less noble stainless steel (anode) to preferentially corrode.

Question 35

Scurvy results from a severe deficiency of Vitamin C, leading to impaired wound healing, weakened capillary walls, and fragile bones. What is the specific biochemical role of Vitamin C in collagen synthesis?

Explanation

Vitamin C is a required cofactor for prolyl hydroxylase and lysyl hydroxylase. These enzymes hydroxylate proline and lysine residues, a step crucial for the formation of stable collagen triple helices.

Question 36

The pullout strength of an orthopedic cortical screw is directly proportional to several design factors. Which of the following screw parameters most significantly increases its pullout strength?

Explanation

Screw pullout strength is primarily determined by the volume of bone caught between the threads, which is mathematically proportional to the outer (major) diameter, thread engagement length, and shear strength of the bone.

Question 37

Viscoelastic materials, such as ligaments and articular cartilage, exhibit time-dependent mechanical properties. Which of the following correctly describes 'stress relaxation'?

Explanation

Stress relaxation refers to the decrease in applied stress required to maintain a given, constant strain (deformation) over time. Creep, in contrast, is the progressive deformation under a constant load.

Question 38

Understanding normal cervical spine anatomy is crucial during anterior approaches and lateral mass screw placement to avoid iatrogenic injury. The vertebral artery typically enters the transverse foramen at which cervical level?

Explanation

The vertebral artery typically branches from the subclavian artery and enters the transverse foramen at C6. It normally bypasses the C7 transverse foramen.

Question 39

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to delay fracture healing in animal models. What is the primary molecular mechanism by which selective COX-2 inhibitors impair bone repair?

Explanation

COX-2 mediates the synthesis of prostaglandins, specifically PGE2, which are essential for both intramembranous and endochondral ossification during the early stages of fracture healing.

Question 40

Aggrecan is the most abundant proteoglycan in articular cartilage and is essential for its compressive properties. Which of the following best describes the molecular assembly of aggrecan in the extracellular matrix?

Explanation

Aggrecan monomers consist of a core protein with chondroitin sulfate and keratan sulfate side chains. Dozens of these monomers bind non-covalently to a single hyaluronic acid chain, stabilized by a link protein, creating large aggregates that draw in water to resist compression.

Question 41

The insertion of a tendon or ligament into bone, known as a direct enthesis, gradually transitions to dissipate mechanical stress. What is the correct sequential histological arrangement of the four zones from tendon to bone?

Explanation

A direct (fibrocartilaginous) enthesis consists of four distinct continuous zones: tendon (or ligament), uncalcified fibrocartilage, calcified fibrocartilage (separated by the tidemark), and bone.

Question 42

The anterior cruciate ligament (ACL) receives its primary blood supply from which of the following vascular structures?

Explanation

The middle genicular artery, a branch of the popliteal artery, pierces the posterior capsule to provide the primary blood supply to the cruciate ligaments via the synovial fold.

Question 43

Osteocalcin is the most abundant non-collagenous protein in bone matrix and serves as a marker of osteoblast activity. Its ability to bind calcium and regulate mineralization is dependent on a post-translational modification requiring which vitamin?

Explanation

Osteocalcin undergoes post-translational gamma-carboxylation of specific glutamic acid residues, which allows it to bind to hydroxyapatite and calcium. This specific enzymatic process is strictly Vitamin K-dependent.

Question 44

Bone Morphogenetic Proteins (BMPs), such as BMP-2 and BMP-7, play pivotal roles in osteoblast differentiation and fracture healing. Which intracellular signaling pathway is primarily activated upon BMP binding to its cell surface receptors?

Explanation

BMPs are members of the TGF-beta superfamily. Upon binding their serine/threonine kinase receptors, they phosphorylate and activate the canonical receptor-regulated Smad proteins, primarily Smads 1, 5, and 8, to regulate transcription.

Question 45

During clinical evaluation of glenohumeral instability, understanding the specific capsuloligamentous restraints is required. Which structure provides the primary restraint to inferior translation of the humerus when the arm is adducted in neutral rotation?

Explanation

In the adducted (0 degrees of abduction) shoulder, the superior glenohumeral ligament (SGHL) and the coracohumeral ligament (CHL) are the primary static restraints against inferior translation of the humeral head.

Question 46

Which of the following cells secretes osteoprotegerin (OPG) to regulate bone resorption?

Explanation

Osteoblasts secrete OPG, which acts as a decoy receptor for RANKL, preventing it from binding to RANK on osteoclasts. This inhibits osteoclastogenesis and reduces bone resorption.

Question 47

In articular cartilage, which zone has the highest concentration of water and collagen, but the lowest concentration of proteoglycans?

Explanation

The superficial zone consists of flattened chondrocytes and collagen fibers oriented parallel to the joint surface. It has the highest water content and lowest proteoglycan content of all the zones.

Question 48

The phenomenon where an orthopaedic biomaterial subjected to a constant load exhibits a progressive increase in strain over time is known as:

Explanation

Creep is the time-dependent deformation of a viscoelastic material under a constant load. Stress relaxation, conversely, is the decrease in stress over time under a constant strain.

Question 49

The predominant blood supply to the adult femoral head arises from the deep branch of the medial femoral circumflex artery (MFCA). This vessel courses between which two muscles to reach the joint capsule?

Explanation

The MFCA passes between the pectineus and iliopsoas anteriorly, then courses posteriorly between the obturator externus and quadratus femoris to supply the femoral head.

Question 50

A solid cylindrical intramedullary nail's resistance to bending is proportional to its area moment of inertia. If the radius of the nail is doubled, its bending stiffness increases by a factor of:

Explanation

The area moment of inertia for a solid cylinder is proportional to the radius to the fourth power (r^4). Therefore, doubling the radius increases bending stiffness by a factor of 2^4 = 16.

Question 51

Which of the following intracellular signaling molecules is directly phosphorylated upon binding of Bone Morphogenetic Protein-2 (BMP-2) to its serine/threonine kinase receptor?

Explanation

BMP signaling utilizes the Smad 1/5/8 intracellular pathway to promote osteoblastic differentiation. Smad 2/3 is associated with TGF-beta signaling, while beta-catenin is involved in the Wnt pathway.

Question 52

A patient presents with a foot drop and an inability to evert the foot following a proximal fibular fracture. Sensation is decreased over the anterolateral leg and dorsum of the foot. Which nerve is injured?

Explanation

The common peroneal nerve wraps around the fibular neck and innervates both the anterior (deep peroneal) and lateral (superficial peroneal) compartments. Injury results in foot drop and loss of eversion.

Question 53

The "working length" of a screw used in orthopaedic fracture fixation is defined as:

Explanation

The working length of a screw is the length of bone specifically engaged by the screw threads. For a plate, working length is the distance between the two closest fixation points on either side of the fracture.

Question 54

Secondary bone healing differs from primary bone healing primarily due to the formation of:

Explanation

Secondary bone healing occurs via endochondral ossification, which involves the formation of a soft cartilaginous callus that is subsequently mineralized. Primary healing utilizes cutting cones without callus formation.

Question 55

Which of the following factors is the primary driving force for galvanic corrosion when two dissimilar metals are implanted in the body?

Explanation

Galvanic corrosion occurs when two metals with different electrochemical potentials are placed in contact within a conductive fluid. The less noble metal acts as an anode and corrodes.

Question 56

Sclerostin, a protein that negatively regulates bone mass, achieves its effect primarily by inhibiting which of the following signaling pathways?

Explanation

Sclerostin is secreted by osteocytes and binds to LRP5/6 receptors on osteoblasts, competitively inhibiting the Wnt/beta-catenin pathway. This results in decreased osteoblastogenesis and bone formation.

Question 57

The posterior interosseous nerve (PIN) enters the posterior compartment of the forearm by passing between the two heads of which muscle?

Explanation

The PIN, a continuation of the deep branch of the radial nerve, enters the posterior compartment of the forearm by passing through the arcade of Frohse between the superficial and deep heads of the supinator muscle.

Question 58

The generation of polyethylene wear debris in a standard metal-on-polyethylene total joint arthroplasty most commonly occurs through which mode of wear?

Explanation

Adhesive wear is the most common mode in standard metal-on-polyethylene joints, occurring when microscopic asperities on the metal head bond to the softer polyethylene, tearing off small particles during motion.

Question 59

When comparing typical lumbar vertebrae to typical thoracic vertebrae, the pedicles of the lumbar spine are anatomically oriented in which manner?

Explanation

Lumbar pedicles are larger in diameter and oriented more sagittally than thoracic pedicles, making pedicle screw insertion generally safer and allowing for larger screw diameters.

Question 60

Which enzyme is responsible for the final conversion of 25-hydroxyvitamin D to its most active form, 1,25-dihydroxyvitamin D?

Explanation

1-alpha-hydroxylase, located primarily in the proximal tubules of the kidney, catalyzes the conversion of 25(OH)D to the active 1,25(OH)2D. Its activity is stimulated by PTH and hypophosphatemia.

Question 61

On a stress-strain curve representing an orthopaedic biomaterial, the area under the elastic region is defined as:

Explanation

Resilience is the capacity of a material to absorb energy in the elastic range, represented by the area under the elastic portion of the stress-strain curve. Toughness is the total area under the entire curve.

Question 62

A patient sustains a traction injury to the upper trunk of the brachial plexus (C5-C6). Which physical exam finding is most likely to be present?

Explanation

Erb's palsy involves the C5-C6 roots (upper trunk), affecting the axillary, suprascapular, and musculocutaneous nerves. This leads to weakness in shoulder abduction, external rotation, and elbow flexion.

Question 63

During physeal growth and endochondral ossification, the primary site of longitudinal growth occurs in which zone of the physis?

Explanation

The proliferative zone is responsible for longitudinal growth via chondrocyte division and matrix production. The hypertrophic zone is responsible for matrix calcification and is the weakest zone where most physeal fractures occur.

Question 64

Increasing the working length of a locked plating construct by leaving empty screw holes over the fracture site has what biomechanical effect?

Explanation

Increasing the working length of a plate increases the flexibility of the construct. This allows for controlled micromotion at the fracture site, promoting secondary bone healing through callus formation.

Question 65

Teriparatide, a recombinant human parathyroid hormone (PTH) analog, promotes bone formation primarily through which mechanism?

Explanation

While continuous PTH exposure leads to net bone resorption, intermittent administration of PTH analogs exerts an anabolic effect by directly stimulating osteoblast activity and extending their lifespan.

Question 66

Pullout strength of a cortical screw is most heavily influenced by which of the following screw design parameters?

Explanation

Screw pullout strength is directly proportional to the outer diameter, the length of thread engagement, and the shear strength of the bone. The inner (core) diameter determines the torsional and bending strength of the screw, not the pullout strength.

Question 67

During osteoclast-mediated bone resorption, which of the following enzymes is primarily responsible for the generation of intracellular protons required to acidify the resorption pit?

Explanation

Carbonic anhydrase II catalyzes the conversion of carbon dioxide and water into protons (H+) and bicarbonate. The protons are then actively pumped into the ruffled border resorption pit by the V-type H+ ATPase pump.

Question 68

A 16-year-old male undergoes a deltopectoral approach for a proximal humerus fracture. Aggressive medial retraction of the conjoined tendon places which of the following nerves at highest risk of injury?

Explanation

The musculocutaneous nerve typically enters the coracobrachialis muscle 5 to 8 cm distal to the coracoid process. Vigorous medial retraction of the conjoined tendon during a deltopectoral approach can stretch and injure this nerve.

Question 69

Which of the following best describes the phenomenon of "creep" in viscoelastic orthopaedic materials?

Explanation

Creep is a viscoelastic property defined as the progressive deformation of a material when subjected to a constant load over time. Stress relaxation, conversely, is the decrease in internal stress over time when a material is held at a constant deformation.

Question 70

The corona mortis, which is at risk of iatrogenic injury during an ilioinguinal approach to the acetabulum, is typically an anastomotic connection between the obturator vessels and which of the following?

Explanation

The corona mortis is an anastomosis between the external iliac system (specifically the inferior epigastric vessels) and the obturator vessels. It crosses the superior pubic ramus and is highly vulnerable during anterior pelvic approaches.

Question 71

Gamma irradiation of ultra-high molecular weight polyethylene (UHMWPE) in an inert environment (e.g., argon or vacuum) followed by remelting is primarily performed to achieve which of the following?

Explanation

Gamma irradiation facilitates cross-linking to improve wear resistance but also creates free radicals that can lead to oxidative degradation. Remelting the polyethylene eliminates these free radicals, stabilizing the material against oxidation at the cost of slight decreases in mechanical strength.

Question 72

In the structural composition of articular cartilage, which molecule is responsible for covalently stabilizing the aggrecan core protein to the hyaluronic acid backbone?

Explanation

Aggrecan, the major proteoglycan in articular cartilage, interacts non-covalently with hyaluronic acid to form massive aggregates. Link protein stabilizes this interaction, securely anchoring the aggrecan monomers to the hyaluronan chain.

Question 73

A patient with a history of recurrent fractures and dense, brittle bones on radiographs is diagnosed with malignant infantile osteopetrosis. This condition is most commonly caused by a loss-of-function mutation affecting which of the following?

Explanation

Osteopetrosis represents a failure of osteoclast-mediated bone resorption. The most common mutation in the severe autosomal recessive form involves TCIRG1, which encodes a subunit of the V-type H+ ATPase required to acidify the resorption pit.

Question 74

Decreasing the distance between the two innermost screws (closest to the fracture site) in a plate-and-screw construct for a diaphyseal fracture will have which of the following biomechanical effects?

Explanation

Working length is defined as the distance between the two nearest fixation points on opposite sides of the fracture. Decreasing the working length restricts motion at the fracture site, thereby increasing the overall stiffness of the construct.

Question 75

Nitrogen-containing bisphosphonates (e.g., alendronate, zoledronic acid) inhibit osteoclast function primarily by targeting which of the following enzymes in the mevalonate pathway?

Explanation

Nitrogen-containing bisphosphonates inhibit farnesyl pyrophosphate (FPP) synthase within the mevalonate pathway. This prevents the prenylation of small GTP-binding proteins (like Ras and Rho), leading to osteoclast apoptosis.

Question 76

Which of the following orthopaedic biomaterials has a Young's modulus of elasticity most closely matching that of human cortical bone?

Explanation

Human cortical bone has a Young's modulus of approximately 15-20 GPa. Titanium alloys (~110 GPa) are closer to cortical bone than stainless steel (~200 GPa) or cobalt-chromium alloys (~220 GPa), resulting in less stress shielding.

Question 77

In the synthesis of Type I collagen, the polypeptide chains form a tight triple helix. This structural conformation fundamentally relies on the presence of which amino acid at every third position?

Explanation

Collagen possesses a characteristic repeating motif of Gly-X-Y, where X is often proline and Y is often hydroxyproline. Glycine, the smallest amino acid, is required at every third position to allow the three chains to pack tightly into the triple helix.

Question 78

The primary vascular supply to the anterior cruciate ligament (ACL) is derived from which of the following arteries?

Explanation

The middle genicular artery originates from the popliteal artery, pierces the posterior capsule, and provides the primary vascular supply to the central pivot structures of the knee, including the ACL and PCL.

Question 79

Sclerostin is a glycoprotein secreted by osteocytes that serves as a potent negative regulator of bone formation. It achieves this primarily by binding to which of the following cellular targets?

Explanation

Sclerostin binds to the LRP5/6 coreceptors on the surface of osteoblasts. This action blocks the canonical Wnt/beta-catenin signaling pathway, effectively inhibiting osteoblast differentiation and bone formation.

Question 80

During a posterolateral approach to the spine for a T10-T11 disc herniation, a major radicular artery is injured, resulting in anterior spinal artery syndrome. This artery (of Adamkiewicz) most frequently enters the spinal canal at which level and on which side?

Explanation

The artery of Adamkiewicz provides the major blood supply to the lower two-thirds of the spinal cord. In roughly 80% of individuals, it arises on the left side between the T9 and L2 vertebral levels.

Question 81

When a patient uses a cane in the hand contralateral to an osteoarthritic hip, what is the primary biomechanical reason for the observed reduction in joint reaction force at the affected hip?

Explanation

Using a cane in the contralateral hand provides an upward force with a long moment arm. This massively reduces the force the ipsilateral hip abductors must exert to keep the pelvis level during stance, which accounts for the majority of the hip joint reaction force.

Question 82

Endochondral ossification is the primary mechanism of bone formation in fracture callus. Which of the following transcription factors is recognized as the master regulator of chondrocyte differentiation in this process?

Explanation

Sox9 is the crucial transcription factor for chondrocyte differentiation and cartilage matrix production during endochondral ossification. Runx2 (Cbfa1) is the master transcription factor for osteoblast differentiation.

Question 83

Figure 1 displays a stress-strain curve for a typical metallic orthopaedic implant.

The exact point on the curve where the material transitions from completely recoverable elastic deformation to non-recoverable plastic deformation is defined as the:

Explanation

The yield point characterizes the transition from elastic to plastic behavior on a stress-strain curve. Loading the material beyond this specific point results in permanent (plastic) deformation.

Question 84

Continuous, chronic elevation of parathyroid hormone (PTH) leads to net bone resorption. This resorptive effect is primarily mediated by PTH initially binding to receptors on which cell type?

Explanation

Osteoclasts lack PTH receptors. PTH binds directly to receptors on osteoblasts, causing them to increase expression of RANKL and decrease expression of OPG, which secondarily stimulates osteoclast recruitment and bone resorption.

Question 85

Galvanic corrosion in orthopaedic implants occurs under which of the following conditions?

Explanation

Galvanic corrosion occurs when two electrochemically dissimilar metals are in direct physical contact within a conductive fluid environment (e.g., body fluids). The less noble metal acts as an anode and undergoes accelerated corrosion.

Question 86

The primary mechanism of action of denosumab in treating osteoporosis is through binding to and inhibiting which of the following molecules?

Explanation

Denosumab is a human monoclonal antibody that binds to RANKL, preventing its interaction with RANK on osteoclasts. This effectively inhibits osteoclast formation, function, and survival.

Question 87

In the context of tendon biomechanics, which of the following best describes the phenomenon of stress relaxation?

Explanation

Stress relaxation is a viscoelastic property where the stress in a material decreases over time when it is held at a constant deformation. In contrast, creep is the continued deformation over time under a constant load.

Question 88

During a volar approach to the forearm for plating a radius fracture, the surgeon must be cautious of the anterior interosseous nerve (AIN). Which of the following muscles is innervated by the AIN?

Explanation

The AIN innervates the flexor pollicis longus, the radial half of the flexor digitorum profundus, and the pronator quadratus. The other listed muscles are innervated by the median nerve proper or the radial nerve.

Question 89

A surgeon considers using a titanium screw to secure a stainless steel plate. Which of the following best describes the primary biomechanical and biologic concern regarding this construct?

Explanation

Mixing different metals, such as stainless steel and titanium, in an aqueous environment like the human body sets up an electrochemical cell. This leads to galvanic corrosion, where the less noble metal undergoes accelerated corrosion.

Question 90

During distraction osteogenesis (e.g., Ilizarov technique), new bone is formed primarily through which of the following processes?

Explanation

Distraction osteogenesis under stable fixation and an appropriate distraction rate typically proceeds via intramembranous ossification. This process directly forms bone without a cartilaginous intermediate stage.

Question 91

The main blood supply to the adult femoral head is primarily derived from which of the following vessels?

Explanation

The medial femoral circumflex artery (MFCA), specifically its deep branch, provides the predominant blood supply to the adult femoral head via the lateral epiphyseal arteries. Injury to this vessel increases the risk of avascular necrosis.

Question 92

The torsional strength of a solid intramedullary nail is proportional to its radius raised to which power?

Explanation

The polar moment of inertia for a solid cylinder, which determines torsional stiffness and strength, is proportional to the radius to the fourth power (r^4). Therefore, small increases in nail diameter exponentially increase its torsional strength.

Question 93

A patient with severe malnutrition presents with bleeding gums, petechiae, and poor wound healing. A deficiency in which of the following vitamins is responsible for these symptoms by impairing the hydroxylation of proline and lysine in collagen synthesis?

Explanation

Vitamin C (ascorbic acid) is an essential cofactor for prolyl and lysyl hydroxylase in collagen synthesis. Deficiency causes scurvy, characterized by defective collagen cross-linking and subsequent tissue fragility.

Question 94

Parona's space is a potential anatomic space in the distal forearm that can serve as a conduit for deep infections. Which of the following constitutes its dorsal border?

Explanation

Parona's space lies in the deep volar forearm. Its volar border is formed by the flexor digitorum profundus and flexor pollicis longus tendons, and its dorsal border is the pronator quadratus muscle and interosseous membrane.

Question 95

Which of the following orthopedic materials has a Young's modulus (modulus of elasticity) that most closely matches that of cortical bone?

Explanation

Titanium alloy has a Young's modulus much closer to that of cortical bone compared to stiffer materials like stainless steel and cobalt-chromium. This closer modulus match helps reduce stress shielding around implants.

Question 96

Sclerostin is a protein that regulates bone mass. It functions primarily by antagonizing which of the following cellular signaling pathways?

Explanation

Sclerostin, produced primarily by osteocytes, binds to LRP5/6 receptors on osteoblasts. This action inhibits the canonical Wnt/beta-catenin signaling pathway, leading to decreased bone formation.

Question 97

During a tarsal tunnel release, the surgeon identifies the structures passing posterior to the medial malleolus. Moving from anterior to posterior, what is the correct order of the structures?

Explanation

The mnemonic "Tom, Dick, And Very Nervous Harry" describes the order from anterior to posterior. The structures are Tibialis posterior, flexor Digitorum longus, posterior tibial Artery/Vein, tibial Nerve, and flexor Hallucis longus.

Question 98

Increasing the inner (root) diameter of a cortical screw primarily improves which of the following mechanical properties?

Explanation

The bending strength of a screw is proportional to the inner (root) diameter to the third power. Pull-out strength, on the other hand, is primarily determined by the outer diameter, thread pitch, and bone quality.

Question 99

Bone morphogenetic proteins (BMPs) initiate intracellular signaling through transmembrane serine/threonine kinase receptors. Which of the following downstream intracellular mediators are primarily activated by BMPs?

Explanation

BMPs signal primarily through the phosphorylation of Smad 1, 5, and 8. These phosphorylated Smads then form a complex with Smad 4 to translocate to the nucleus and regulate gene transcription for osteoblastogenesis.

Question 100

In total joint arthroplasty, the generation of ultra-high molecular weight polyethylene (UHMWPE) wear debris typically incites an inflammatory response that leads to osteolysis. Which of the following cell types is the primary effector responsible for phagocytosing this debris and releasing pro-inflammatory cytokines?

Explanation

Macrophages phagocytose UHMWPE wear particles and release pro-inflammatory cytokines such as TNF-alpha, IL-1, and IL-6. This inflammatory cascade subsequently stimulates osteoclast-mediated bone resorption, leading to osteolysis.

None

Detailed Chapters & Topics

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51 Chapters

Chapter 1 47 min

Orthopedic Anatomy Review | Dr Hutaif Basic Science Rev -...

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Chapter 2 103 min

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Chapter 3 56 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 1)

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Chapter 4 55 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 2)

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Chapter 5 56 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 3)

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Chapter 6 55 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 4)

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Chapter 7 52 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 1)

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Chapter 8 55 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 2)

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Chapter 9 56 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 3)

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Chapter 10 58 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 4)

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Chapter 11 77 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 1)

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Chapter 12 74 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 2)

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Chapter 13 56 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 3)

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Chapter 14 58 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 4)

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Chapter 15 72 min

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 1)

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Chapter 16 77 min

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 2)

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Chapter 17 78 min

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 3)

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Chapter 18 73 min

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 4)

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Chapter 19 56 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 1)

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Chapter 20 55 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 2)

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Chapter 21 75 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 3)

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Chapter 22 79 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 4)

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Chapter 23 77 min

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 5)

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Chapter 24 55 min

Anatomy Board Review (Set 2): Musculoskeletal & Neurovascular MCQs | AAOS, ABOS Prep

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Chapter 25 53 min

Orthopedic Anatomy MCQs (Set 3): Bone Structure, Joint Kinematics & Ligaments | ABOS & AAOS Review

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Chapter 26 48 min

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Chapter 27 50 min

AAOS & ABOS Basic Science MCQs (Set 2): Biomechanics, Anatomy & Bone Healing

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Chapter 28 51 min

AAOS & ABOS Basic Science MCQs (Set 3): Orthopedic Biomechanics & Bone Physiology | OITE Review

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Chapter 29 50 min

Orthopedic Basic Science MCQs (Set 4): Biomechanics, Bone Physiology & Biomaterials | AAOS, ABOS Review

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Chapter 30 49 min

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Chapter 31 56 min

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Chapter 32 50 min

AAOS Basic Science MCQs (Set 1, 2002): Biomechanics, Bone Healing & Anatomy for ABOS & OITE

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Chapter 33 48 min

AAOS Basic Science Orthopedic MCQs (Set 3): Bone Metabolism, Biomechanics & Cartilage Biology | Board Review

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Chapter 34 49 min

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Chapter 35 52 min

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Chapter 36 52 min

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Chapter 37 55 min

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Chapter 38 51 min

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Chapter 39 53 min

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Chapter 40 51 min

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Chapter 41 50 min

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Chapter 42 53 min

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Chapter 43 54 min

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Chapter 44 50 min

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Chapter 45 52 min

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Chapter 46 38 min

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Chapter 47 53 min

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Chapter 48 50 min

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Chapter 49 53 min

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Chapter 50 56 min

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Chapter 51 57 min

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Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 1)

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 2)

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 3)

Orthopedic Basic Science 2026 MCQs: Board Review Questions & Answers (Part 4)

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 1)

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 2)

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 3)

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 4)

Orthopedic Anatomy 2026 MCQs: Board Review Questions & Answers (Part 5)

Anatomy Board Review (Set 2): Musculoskeletal & Neurovascular MCQs | AAOS, ABOS Prep

Orthopedic Anatomy MCQs (Set 3): Bone Structure, Joint Kinematics & Ligaments | ABOS & AAOS Review

AAOS & ABOS Orthopedic Basic Science MCQs (Set 1): Anatomy, Biomechanics & Bone Biology | OITE Prep

AAOS & ABOS Basic Science MCQs (Set 2): Biomechanics, Anatomy & Bone Healing

AAOS & ABOS Basic Science MCQs (Set 3): Orthopedic Biomechanics & Bone Physiology | OITE Review

Orthopedic Basic Science MCQs (Set 4): Biomechanics, Bone Physiology & Biomaterials | AAOS, ABOS Review

AAOS & ABOS Anatomy MCQs (Set 2): Musculoskeletal, Neuro, & Regional Topography for Board Review

AAOS Orthopedic Anatomy MCQs (Set 3): Musculoskeletal & Skeletal System | ABOS Board Prep

AAOS Basic Science MCQs (Set 1, 2002): Biomechanics, Bone Healing & Anatomy for ABOS & OITE

AAOS Basic Science Orthopedic MCQs (Set 3): Bone Metabolism, Biomechanics & Cartilage Biology | Board Review

AAOS Basic Science MCQs (Set 4): Bone Healing, Cartilage Biology & Biomechanics | ABOS Exam Prep

AAOS, ABOS & OITE Anatomy MCQs (Set 2): High-Yield Skeletal, Joint & Muscle Systems

AAOS & ABOS Anatomy MCQs (Set 3): Musculoskeletal & Skeletal System Questions | Board Review

Anatomy Board Review MCQs (Set 4): Peripheral Nerve & Musculoskeletal Systems | AAOS ABOS OITE

AAOS Basic Science MCQs (Set 1): Bone Physiology, Biomechanics & Pharmacology | Ortho Board Review

AAOS Basic Science MCQs (Set 2): Bone Healing & Orthopedic Biomechanics | ABOS, OITE Prep

AAOS Basic Science MCQs (Set 3): Bone & Cartilage Biology, Ortho Biomechanics | ABOS Exam Prep

AAOS & ABOS Basic Science MCQs (Set 4): Bone Biology, Biomechanics & Physiology | Orthopedic Board Prep

AAOS Basic Science MCQs (Set 1): Biomechanics & Bone Biology | ABOS Board Prep

AAOS & ABOS Basic Science MCQs (Set 2): Biomechanics, Bone Physiology & Pharma | Board Review

Orthopedic Anatomy Practice Questions (Set 1): Musculoskeletal & Clinical Concepts for AAOS/ABOS

AAOS & ABOS Anatomy MCQs (Set 3): Skeletal, Joint, and Muscle Anatomy | Orthopedic Board Prep

Anatomy Board Review MCQs (Set 4): Peripheral Nerves, Major Joints, & Muscle Anatomy | USMLE & ABOS Prep

AAOS Orthopedic Anatomy MCQs (Set 5): Musculoskeletal & Regional Review

AAOS & ABOS Basic Science MCQs (Set 1): Biomechanics, Bone Physiology & Cartilage Biology for OITE

AAOS Orthopedic Basic Science MCQs (Set 2): Musculoskeletal Anatomy, Biomechanics & Physiology | Board Review

AAOS Basic Science MCQs (Set 3): Bone Physiology & Biomechanics | ABOS Board Review

AAOS Basic Science MCQs (Set 4): Bone Physiology, Biomechanics, & Biomaterials

Guide Overview