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1. General Principles & Basic Science MCQs

Practice Set 174 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3461

Topic: Biomechanics & Biomaterials

Two years ago, a 63-year-old man underwent right total hip arthroplasty (THA) with a modular femoral head-neck and neck-stem prosthesis (a photograph of the removed implant is shown in Figure 181). He now has increasing hip pain. Radiographs reveal a stable hip arthroplasty and elevated serum cobalt and chromium levels. MR imaging is obtained, and, based on these findings, the patient’s hip is revised. Which corrosion type likely is responsible for this THA failure?

. Galvanic
. Pitting
. Fretting
. Crevice

Correct Answer & Explanation

. Galvanic

Explanation

DISCUSSIONMicromotion at the femoral head-neck or stem-neck junction can lead to fretting corrosion. Fretting corrosion is among the most common causes of failure in modular components. Modularity gives surgeons additional intraoperative flexibility but has resulted in corrosion-related failure and an implant recall. Although titanium and cobalt-chrome contain a protective surface oxide layer, continued micromotion at the modular junction may disrupt the protective layer, resulting in fretting corrosion. This may eventually lead to excessive metal ion formation and painful synovitis that necessitates a revision procedure. Galvanic corrosion is attributable to a mismatch in electrochemical gradients between dissimilar metals. Crevice or pitting corrosion occurs in fatigue cracks because of differences in oxygen tension.

Question 3462

Topic: 1. General Principles & Basic Science

Bioabsorbable polymers are used in a wide range of orthopaedic devices, including anchors, staples, pins, plates, and screws. What is the primary drawback for bioabsorbable implants?

. High cost
. Increased rates of infection
. High elastic modulus
. Brittleness
. Foreign body reaction

Correct Answer & Explanation

. High cost

Explanation

DISCUSSION: A number of bioabsorbable polymers are used in orthopaedic applications, and all have in common reports of foreign body reactions, which occur in more than 50% of patients in some series.  In general, the high cost of these polymers is offset by the elimination of a second surgery to remove the implant.  Bioabsorbable polymers are low strength in comparison to metallic alloys but of sufficient strength for many orthopaedic applications.  The elastic modulus is not as high as many other orthopaedic biomaterials, making them suitable for applications where lower stiffness is an asset.REFERENCES: Ambrose CG, Clanton TO: Bioabsorbable implants: Review of clinical experience in orthopedic surgery.  Ann Biomed Eng 2004;32:171-177.Bergsma JE, de Bruijn WC, Rozema FR, et al: Late degradation tissue response to poly(L-lactide) bone plates and screws.  Biomaterials 1995;16:25-31.

Question 3463

Topic: 1. General Principles & Basic Science

The fracture shown in Figure 32 is strongly indicative of what diagnosis?

. Osteogenesis imperfecta
. Vitamin D-resistant rickets
. Lead toxicity
. Child abuse
. Osteomyelitis

Correct Answer & Explanation

. Osteogenesis imperfecta

Explanation

DISCUSSION: Fractures that occur through the primary spongiosa at the subphyseal region of the metaphysis are highly specific for child abuse.  On radiographic studies, the metaphyseal lucency in these injuries may appear as either the so-called “bucket-handle” or “metaphyseal corner” fracture.  These fractures are not typical features of osteogenesis imperfecta or vitamin D-resistant rickets.  The ingestion of lead may lead to thick, transverse bands of increased density at the distal metaphysis.  Fractures in the subphyseal region of the metaphysis are not typically seen in children who have osteomyelitis.REFERENCES: Kocher MS, Kasser JR: Orthopaedic aspects of child abuse.  J Am Acad Orthop Surg 2000;8:10-20.Kleinman PK, Marks SC, Blackbourne B: The metaphyseal lesion in abused infants: A radiologic-histopathologic study.  Am J Roentgenol 1986;146:895-905.

Question 3464

Topic: Physiology & Rehabilitation

During the early swing phase of the normal gait cycle, what lower extremity muscle is primarily contracting?

. Tibialis posterior
. Tibialis anterior
. Vastus medialis
. Adductor longus
. Gastrocnemius

Correct Answer & Explanation

. Tibialis posterior

Explanation

DISCUSSION: Electromyography during walking reveals the tibialis anterior muscle is active during early swing, allowing the foot to clear the ground.  All of the other muscles are quiet, as the limb moves forward through space with minimal muscular effort.  The other muscles are primarily active during weight acceptance or push-off.REFERENCES: Gage JR: An overview of normal walking.  Instr Course Lect 1990;39:291-303.Wootten ME, Kadaba MP, Cochran GV: Dynamic electromyography II:  Normal patterns during gait.  J Orthop Res 1990;8:259-265.

Question 3465

Topic: Surgical Anatomy & Approaches

A 35-year-old man has profound deltoid weakness after sustaining a traumatic anterior shoulder dislocation 6 weeks ago. Electromyographic (EMG) studies confirm an axillary nerve injury. Follow-up examination at 3 months reveals no recovery of function. What is the best course of action?

. Surgical repair of the Bankart lesion
. Exploration of the axillary nerve
. MRI neurography
. Repeat EMG studies
. Continued observation and physical therapy

Correct Answer & Explanation

. Surgical repair of the Bankart lesion

Explanation

DISCUSSION: Documenting the status of recovery at this time is appropriate; therefore, repeat EMG studies should be conducted to check for early signs of reinnervation.  Timing of nerve exploration in this setting is debated, with authors suggesting exploration if there is no sign of recovery at 6 to 9 months.REFERENCES: Perlmutter GS: Axillary nerve injury.  Clin Orthop 1999;368:28-36.Artico M, Salvati M, D’Andrea V, et al: Isolated lesions of the axillary nerves: Surgical treatment and outcome in twelve cases.  Neurosurgery 1991;29:697-700.Vissar CP, Coene LN, Brand R, et al: The incidence of nerve injury in anterior dislocation of the shoulder and its influence on functional recovery: A prospective clinical and EMG study.  J Bone Joint Surg Br 1999;81:679-685.Pasila M, Jarma H, Kiviluoto O, et al: Early complications of primary shoulder dislocations.  Acta Orthop Scand 1978;49:260-263.

Question 3466

Topic: 1. General Principles & Basic Science

-What is the most appropriate initial treatment?

. Run a wound culture and return to the operating room for arthrotomy, irrigation, and debridement.
. Return to the operating room, blister debridement, split-thickness skin grafting, and prophylactic intravenous (IV) penicillin G (PCN G) every 6 hours
. Return to the operating room, blister debridement, apply topical aloe, and prophylactic IV PCN G every 6 hours
. Bedside blister debridement, apply topical aloe, and prophylactic IV PCN G every 6 hours

Correct Answer & Explanation

. Run a wound culture and return to the operating room for arthrotomy, irrigation, and debridement.

Explanation

DISCUSSION FOR QUESTIONS 83 AND 84Based upon the history and description of the wound, this patient has sustained a frostbite injury to the anterior skin without evidence of infection. Frostbite, a thermal injury to local tissues, can be classified into first-, second-, third-, and fourth-degree injuries. First-degree injuries are characterized by a central whitish area surrounded by erythema. Second- and third-degree injuries are characterized by blisters that appear within the first 24 hours. Second-degree blisters are clear or cloudy, while third-degree blisters are hemorrhagic. Fourth-degree injuries are characterized by tissue necrosis. Treatment of a frostbite injury should begin as soon as it is identified, even if severity has not been determined. Treatment includes protection against mechanical irritation and keeping the injured area away from heat. The limb should be elevated and clear blisters debrided; dark blisters should be drained but not debrided. Topical treatment includes aloe application every 6 hours (silver sulfadiazine for open wounds). Nonsteroidal anti-inflammatory drugs can be given along with PCN G (500,000 U) or clindamycin (600 mg) IV every 6hours for 48 to 72 hours as prophylaxis against infection.Multiple skin incisions on the front of the knee place the skin at healing risk after surgery.Skin oxygenation is further compromised by a lateral release, which disrupts the superior lateral geniculate artery in the peripatellar vascular anastomosis. When addressing compromised perfusion to the skin, the orthopaedic surgeon may consider not performing a lateral release, using the medial parapatellar incision,and/or not using a tourniquet during surgery. In this patient, the use of cold therapy further compromised perfusion to the skin. This patient’s wound does not reflect infection, but rather frostbite from the compromised skin perfusion and the application of cold therapy.The physiologic responses to the effects of freezing temperatures on limbs have been categorized into 4 phases. Phase I, cooling and freezing, is characterized by vasoconstriction and vasospasm. The freezing results in mechanical destruction of cell membranes in endothelial cells in small capillaries. Phase II,rewarming, initiates as heat absorbed by the limb begins an exothermic reaction as extracellular and intracellular crystals melt. Intracellular swelling occurs and small capillaries become highly permeable,resulting in extravasation of fluid and causing edema and blisters. Phase III is characterized by progressive tissue injury resulting from inflammation, vascular stasis, and thrombosis leading to ischemia.Phase IV is recovery that can progress along 3 potential pathways: complete healing, healing with later sequelae, or early tissue necrosis leading to gangrene.CLINICAL SITUATION FOR QUESTIONS 85 THROUGH 87Figure 85 is the radiograph of a 13-year-old right-handed baseball player who has experienced 2 months of right-dominant shoulder pain. As a pitcher, he says he cannot “throw hard” without pain, and he develops a dull ache if he throws more than 15 pitches.

Question 3467

Topic: 1. General Principles & Basic Science

Histologically, synovial chondromatosis is characterized by

. exuberant synovitis (Pannus).
. loose fragments of articular cartilage embedded in the synovium.
. ossified cartilage nodules embedded in the synovium.
. the presence of granulomas in the synovium.
. hemosiderin deposition in the synovium.

Correct Answer & Explanation

. exuberant synovitis (Pannus).

Explanation

DISCUSSION: Histologically, there is metaplastic cartilage arising from the synovium.  These lobules of zonates hyaline cartilage are of variable size, are embedded within edematous synovium, and protrude into the joint.  The lobules calcify and ossify, leading to the characteristic radiographic appearance.  Inflammatory synovitis is not characteristic of synovial chondromatosis.  The fluid is clear and serosanguin, not blood tinged.REFERENCES: Milgram JM: Synovial osteochondromatosis: A histopathological study of thirty cases.  J Bone Joint Surg Am 1977;l59:792-801.Murphy FP, Dahlin DC, Sullivan CR: Articular synovial chondromatosis.  J Bone Joint Surg Am 1962;44:77.

Question 3468

Topic: 1. General Principles & Basic Science

What is the primary indication for performing an arthroscopic synovectomy on a patient with hemophilia that is the result of factor VIII deficiency? Review Topic

. Joint pain with radiographic evidence of joint space narrowing
. Joint stiffness that has not improved with physiotherapy and bracing
. Recurrent joint bleeding despite optimal medical management
. Prophylaxis for joint preservation in severe hemophilia (factor VIII level <1%)
. Decreasing ambulatory endurance despite optimal medical management

Correct Answer & Explanation

. Joint pain with radiographic evidence of joint space narrowing

Explanation

Improved medical management has changed musculoskeletal outcomes for individuals with hemophilia. Patients with severe hemophilia receiving prophylactic administration of factor VIII may never develop a target joint that requires further orthopaedic intervention. Patients with moderate hemophilia and those patients with severe hemophilia not receiving prophylactic treatment will still develop joints that have recurrent hemarthroses. When recurrent hemarthrosis continues despite optimal medical management, synovectomy is indicated. While synovectomy is predictable in its ability to decrease joint bleeding, it does not necessarily improve joint range of motion or prevent the development of hemophilic arthropathy over time. It will not reverse articular damage to the joint once it has developed.

Question 3469

Topic: 1. General Principles & Basic Science

Figures 37a and 37b show the clinical photographs of a 43-year-old patient with type I diabetes mellitus who has a stump ulcer after undergoing successful transtibial amputation 1 year ago. Which of the following is considered the most predictable method of healing the ulcer and preventing recurrent ulceration?

. Refrain from using the prosthesis until the ulcer heals.
. Refrain from using the prosthesis and apply platelet-derived growth factor daily until the ulcer heals.
. Have a prosthetist relieve the area of the anterior-distal tibia to eliminate pressure and allow the ulcer to heal.
. Replace the prosthetic socket liner with a thick silicone liner.
. Perform a wedge resection of the infected tissue, create a soft-tissue envelope with muscle covering the bone, and allow primary healing of the skin.

Correct Answer & Explanation

. Refrain from using the prosthesis until the ulcer heals.

Explanation

DISCUSSION: The ulcer occurred as the result of a mismatch between the shape of the residual limb and the prosthetic socket.  With the mismatch, the residual limb pistoned and the tissue failed because of the applied shear forces.  The most predictable short- and long-term solution is reconstruction of the residual limb.  Refraining from use of the prosthesis will prevent the patient from walking for months.  It is unlikely that prosthetic socket modification will allow resolution of this large ulcer.REFERENCE: Hadden W, Marks R, Murdoch G, et al: Wedge resection of amputation stumps: A valuable salvage procedure.  J Bone Joint Surg Br 1987;69:306-308.

Question 3470

Topic: 1. General Principles & Basic Science

-Figure 162 is the CT scan of a 74-year-old woman who struck her head during a ground-level fall and has severe neck pain. Examination reveals normal strength and sensation in her upper and lower extremities.What is the most appropriate treatment option?

. Cervical traction
. Halo-vest orthosis
. Anterior single-level fusion
. Posterior single-level fusion
. Posterior multilevel fusion

Correct Answer & Explanation

. Cervical traction

Explanation

Question 3471

Topic: 1. General Principles & Basic Science

Tendon fibroblasts detect applied strain through what mechanism?

. Induced apoptosis from tendon loading
. Induced cell elongation from tendon loading
. Tendon loading-mediated cell pressurization
. Deflection of cell-cilia from tendon loading

Correct Answer & Explanation

. Induced apoptosis from tendon loading

Explanation

The primary cilium is a cellular extension present in nearly every cell of the body, and has been shown to have critical importance in numerous functions. Emerging evidence in tendon mechanobiology suggests that mechanotransduction signaling is also mediated by the deflection of the primary cilium in response to tendon loading. "Induced apoptosis from tendon loading" would infer that each time a tendon was loaded and a portion of the tenocytes apoptosed, there would be fewer cells left, and no hope for a hypertrophy response to the loads applied. Tendon loading-mediated cell pressurization and cell elongation were previously suggested as possible means for a mechanism to mediate mechanotransduction.

Question 3472

Topic: 1. General Principles & Basic Science

A 27-year-old woman sustained a bilateral C5-6 facet subluxation in a motor vehicle accident. Neurologic evaluation reveals normal motor, sensory, and reflex functions. She is awake, alert, and cooperative. Initial management should consist of

. halo application.
. skeletal traction and attempted closed reduction.
. a soft cervical collar.
. immediate transfer to the operating room for closed reduction.
. immediate transfer to the operating room for open reduction and stabilization posteriorly.

Correct Answer & Explanation

. halo application.

Explanation

DISCUSSION: As long as the patient is alert and cooperative, an attempt can be made to reduce the dislocation.  This should not be attempted in a patient who is obtunded, comatose, or uncooperative.  If any neurologic changes are noted during the reduction maneuver, the attempt should be stopped, appropriate radiographic studies obtained, and open reduction and stabilization planned in the operating room.REFERENCE: Eismont FJ, Arena MJ, Green BA: Extrusion of an intervertebral disc associated with traumatic subluxation or dislocation of cervical facets: Case reports.  J Bone Joint Surg Am 1991;73:1555-1560.

Question 3473

Topic: Infection, Pharmacology & VTE
  • An otherwise healthy 65-year-old man has had chronic pain in his prosthetic knee for the past 9 months. Repeated aspirations reveal a coagulase-negative staphylococcus infection. To eradicate the infection while maintaining the best possible joint function, management should consist of
. Long-term administration of IV and oral antibiotics
. Open soft-tissue debridement, retention of prosthetic components, and IV antibiotics
. Immediate exchange arthroplasty with antibiotic-impregnated cement
. Two-stage surgical prosthetic exchange and IV antibiotics
. Resection arthroplasty and IV antibiotics

Correct Answer & Explanation

. Long-term administration of IV and oral antibiotics

Explanation

Postoperative wound infections following total joint arthroplasty are generally classified as acute or chronic. The time period is either 2 or 4 weeks from the time of implantation depending on whom you read. This will, generally, determine if you can attempt a one-stage procedure. The other considerations are the bacteria’s resistance to antibiotics and whether or not it produces glycocalyx. If the microorganism elaborates glycocalyx it is highly likely that it will remain after surgical removal of the implants and debridement of the joint.Present recommendations are to avoid a one-stage reconstruction in a patient in whom a glycocalyx elaborating microorganism has been isolated. In one study 52% of the isolates of S. epidermidis and 28% of the isolates of S. aureus elaborated glycocalyx. The microbiology laboratory can be asked to determine if the microorganisms elaborate glycocalyx. In the present case it should be assumed that the staphylococci elaborate glycocalyx and are resistant to antibiotics. A two-stage procedure is indicated for these reasons alone.Antibiotic therapy alone has been used for a select group of patients who could not medically tolerate either a one-stage or a two-stage arthroplasty. The patient in this case is listed as otherwise healthy.The decision to perform a resection arthroplasty as a definitive procedure without reimplantation is based on the bacteria’s resistance to antibiotics, quality of the local soft tissues, the complexity of the reconstruction, the patient’s refusal to have another operation, the patient’s overall health, or a combination of these factors. None of which appear to be present in this case.

Question 3474

Topic: Surgical Anatomy & Approaches

A 25-year-old male involved in a motor vehicle accident sustains multiple injuries. He undergoes operative treatment for his humeral shaft fracture. Figures A and B show his preoperative and postoperative radiographs. The distal interlocks for this implant place which of the following nerves at risk?

. Radial
. Ulnar
. Anterior interosseous
. Axillary
. Musculocutaneous

Correct Answer & Explanation

. Radial

Explanation

With intramedullary (IM) nailing of the humerus, the distal anterior-to-posterior interlocking screws place the musculocutaneous nerve at high risk for injury as it goes through the coracobrachialis muscle and courses anteriorly along the brachialis (of which it innervates the medial half).Rupp et al performed a cadaveric study with IM nails utilizing either lateral-to-medial or anterior-to-posterior distal interlocking screws. They showed that anterior-to-posterior screws placed the musculocutaneous nerve at high risk, while lateral-to-medial screws placed the radial nerve at high risk as it courses laterally distally along the humerus.OrthoCash 2020

Question 3475

Topic: 1. General Principles & Basic Science

What is the main biologic effect of aggrecan in cartilage? Review Topic

. Extracellular matrix protein involved in the organization of collagen
. Proteoglycan involved in the hydrophilic behaviour of cartilage
. Cartilage matrix protein that plays a role in cartilage tissue organization
. Collagen component responsible for stability
. Non-collagenous extracellular matrix protein that regulates chondrocyte proliferation

Correct Answer & Explanation

. Extracellular matrix protein involved in the organization of collagen

Explanation

Aggrecan binds hyaluronic acid to attract water, which accounts for its hydrophilic property.Aggrecan is the predominant proteoglycan in cartilage. It contains a large number of negatively charged sequences that attract water called sulfated glycosaminoglycan (GAG) chains. Its the N-terminal globular domain of aggrecan that binds hyaluronan to form huge aggregates. Together with its chondroitin sulfate chains, they help to create a hydrophilic viscous gel that decreases the coefficient of friction as well as to help absorb compressive loads.Ulrich-Vinthe et al. reviewed the biology of articular cartilage. They report that matrix metalloproteinases and aggrecanases play a major role in aggrecan degradation and their production is upregulated by mediators associated with joint inflammation and overloading.Illustration A shows a depiction of the function of aggrecan in articular cartilage. In the relaxed state, the aggregates draw water into cartilage. With compressive loads, the water is displaced to cushion the load. Upon removal of the load, the water content is restored.Incorrect Answers:

Question 3476

Topic: Biology, Genetics & Bone Healing

What gene is expressed the earliest during the differentiation of a chondrocyte during endochondral ossification?

. Aggrecan
. Sox-9
. Collagen type II
. Collagen type IV
. Collagen type XI

Correct Answer & Explanation

. Aggrecan

Explanation

DISCUSSION: Transcription factors regulate the activation or repression of cartilage-specific genes. Sox-9, considered a major regulator of chondrogenesis, regulates several cartilage-specific genes during endochondral ossification, including collagen types II, IV, and XI and aggrecan.REFERENCES: 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.Sandell LJ: Genes and gene expression.  Clin Orthop 2000;379:S9-S16.

Question 3477

Topic: Biology, Genetics & Bone Healing

A female cross-country runner has an insidious onset of right groin pain. Radiographs of the right hip reveal a tension-side stress fracture. History reveals that she was treated for a “foot” fracture 1 year ago. In addition to performing internal fixation of the femoral neck, which of the following should be obtained?

. Menstrual history
. Family history
. Serum calcium level
. MRI of the hip
. Contralateral hip radiograph

Correct Answer & Explanation

. Menstrual history

Explanation

DISCUSSION: Stress fractures in female long distance runners are frequently associated with the Female Athletic Triad.  The triad consists of osteoporosis, amenorrhea, and altered eating habits.  A thorough menstrual history, including age of menarche, history of amenorrhea, and use of oral contraceptives, is imperative.  Amenorrhea leads to osteoporosis and predisposes the athlete to fractures.  An MRI of the hip is not necessary because a fracture is evident on the radiograph.  Serum calcium levels are normal in osteoporosis, a family history would be noncontributory, and it is highly unlikely that a contralateral hip radiograph will yield useful information.REFERENCES: Bennell KL, Malcolm SA, Thomas SA, et al: Risk factors for stress fractures in track and field athletes: A twelve-month prospective study.  Am J Sports Med 1996;24:810-818.Barrow GW, Saha H: Menstrual irregularity and stress fractures in collegiate female distance runners.  Am J Sports Med 1988;16:209-216.

Question 3478

Topic: 1. General Principles & Basic Science

In regards to a genetic disorder, which of the following is an example of "anticipation?"

. Gene characteristics more severe and earlier in onset in subsequent generations
. A disorder inherited from a genetic mutation specific to maternal DNA
. Gene characteristics expressed to varying degrees in different individuals
. Variation in the relative frequency of a genotype due to chance
. The presence of an extra copy of a chromosome

Correct Answer & Explanation

. Gene characteristics more severe and earlier in onset in subsequent generations

Explanation

Genetic anticipation is a phenomenon in which a genetic disorder becomes progressively more severe and earlier in onset with each generation. Examples of disorders exhibiting anticipation include Huntington's disease and myotonic dystrophy.Genetic anticipation is an important concept in understanding the development and genetic implications of many heritable disorders. It is a common phenomenon in trinucleotide repeat expansion disorders. These disorders are due to unstable microsatellite trinucleotide repeats that expand beyond the normal threshold. In subsequent generations these expansions become longer and thus express disease characteristics at a younger age of onset, and often with greater severity.Martorell et al. investigated the development of CTG trinucleotide repeats in patients with myotonic dystrophy type 1 (DM1) and their relatives. They discovered unaffected individuals carry a pre-mutation sequence which can lead to trinucleotide repeat expansion in subsequent generations and thus produce offspring with the disorder.Kamsteeg et al. compare the characteristics of DM1 and DM2. Both are due to trinucleotide repeat expansions. However, while DM1 can present with earlier onset and increasing severity in each generation, DM2 does not exhibit this genetic anticipation.Incorrect Answers

Question 3479

Topic: 1. General Principles & Basic Science

Stiffness relates the amount of load applied to a structure like a long bone or an intramedullary nail to the amount of resulting deformation that occurs in the structure. What is the most important material property affecting the axial and bending stiffness of a structure?

. Elastic modulus
. Ductility
. Ultimate stress
. Yield stress
. Toughness

Correct Answer & Explanation

. Elastic modulus

Explanation

DISCUSSION: The amount of deformation resulting in response to an applied load depends on the stress distribution that the load creates in the structure and the stress versus strain behavior of the material that makes up the structure.  Axial and bending loads create stress distributions that involve normal stresses and normal strains.  Although all five responses are indeed material properties, only one, elastic modulus, relates normal stresses to normal strains.  In fact, axial and bending stiffness are directly proportional to modulus, so that a nail made from stainless steel will have nearly twice the stiffness of a nail made from titanium alloy (because their respective elastic moduli differ by about a factor of two).REFERENCES: Hayes WC, Bouxsein ML: Analysis of muscle and joint loads, in Mow VC, Hayes WC (eds): Basic Orthopaedic Biomechanics, ed 2.  New York, NY, Lippincott-Raven, 1997, pp 74-82.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 159-165.Wright TM, Maher SA: Biomaterials, in Einhorn TA, O’Keefe RJ, Buckwalter JA (eds): Orthopaedic Basic Science: Foundations of Clinical Practice, ed 3.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, in press.

Question 3480

Topic: 1. General Principles & Basic Science

Which structure is shown in Video 27? 27

. Superficial medial collateral ligament
. Semimembranosus tendon
. Posterior oblique ligament
. Medial patellofemoral ligament

Correct Answer & Explanation

. Superficial medial collateral ligament

Explanation

DISCUSSIONVideo 27 shows the medial patellofemoral ligament running from the medial epicondyle of the femur to the medial portion of the patella. The posterior oblique ligament and the superficial medial collateral ligament run from medial epicondyle to the tibia.RECOMMENDED READINGSBabb JR, Detterline AJ, Noyes FR. AAOS Orthopaedic Video Theater. The Key to the Knee: A Layer-by-Layer Video Demonstration of Medial and Anterior Aatomy. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2009.Hoppenfeld S, deBoer P. Surgical Exposures in Orthopedics. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2003:493-568.

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