1. General Principles & Basic Science MCQs

In both room temperature air and physiologic fluids, titanium alloys self-passivate or spontaneously form a layer of titanium oxide very rapidly. This layer makes titanium alloys resistant to surface breakdown.

Evidence implicates an association, albeit unexplained, between Clostridium septicum infection and malignancy, particularly hematologic or intestinal malignancy. The malignancy is often at an advanced stage, compromising survival of the patients. A bowel portal of entry is postulated for most patients. In the absence of an external source in the patient with clostridial myonecrosis or sepsis, the cecum or distal ileum should be considered a likely site of infection. Increased awareness of this association between Clostridium septicum and malignancy, and aggressive surgical treatment, may result in improvement in the present 50% to 70% mortality rate.

By 5 years, the allograft cartilage will be completely acellular, so there will be no residual donor chondrocytes.Enneking et al. conducted both radiographic and histologic studies of sixteen massive retrieved human allografts four to sixty-five months after implantation. Analysis of the articular cartilage revealed no evidence that any chondrocytes had survived, even when the graft had been cryoprotected before it was preserved by freezing.A 64-year-old woman with a longstanding history of rheumatoid arthritis complains of finger dysfunction for the past 6 months. Figure A displays her hand during active extension of all fingers. Figure B displays her hand maintaining her fingers extended following passive extension. What is the next most appropriate treatment for the ring finger?Spiral oblique retinacular ligament reconstructionSagittal band reconstructionLateral band reconstructionCentral slip reconstructionTriangular ligament and transverse retinacular ligament reconstructionSagittal band disruption is often associated with rheumatoid arthritis. When this patient attempts to actively extend the affected digit, the extensor tendonsubluxates ulnarly as a result of the sagittal band rupture, and is left with an extensor lag. If one passively extends the finger fully, the patient is able to maintain this position, as the tendon is intact.Sagittal band reconstruction can be performed with Watson's technique of creating a distally based tendon graft harvested from the central third of the extensor tendon, passed deep to the intermetacarpal ligament and sutured back to itself. Illustration A depicts an intraoperative view of the tendon before reconstruction and Illustration B displays tendon following sagittal band reconstruction. Illustration C displays all of the anatomic locationsof the options listed above.A splenectomy is performed in a 7-year-old boy following a motor vehicle accident. All of the following are recommended for long-term management EXCEPT:Pneumococcal vaccinationHaemophilus influenza type B vaccinationMeningococcal group C vaccinationLifelong prophylactic antibioticsHepatitis A vaccinationAll of the responses are correct except the need for Hepatitis A vaccine. Hepatitis A is a virus with tropism for hepatocytes which causes infection from fecal-oral contaminated food/water, and shows no increased rate of either infectivity or morbidity in patients with hyposplenism.Basic recommendations for splenectomized patients include:All splenectomized patients and those with functional hyposplenism should receive pneumococcal immunization.Patients not previously immunized should receive haemophilus influenza type B vaccine.Patients not previously immunized should receive meningococcal group C conjugate vaccine.Influenza immunization should be given.Lifelong prophylactic antibiotics are still recommended (oral phenoxymethylpenicillin or erythromycin). This is seemingly despite lack of good data demonstrating a role for lifelong chemoprophylaxis and the acknowledgement that long-term compliance may be problematic.Davies et al review the current level of evidence supporting these guidelinesfor infection prevention in patients with hyposplenism. New to these guidelines are issues regarding occupational exposure and the use of the meningococcal group C and the seven-valent pneumococcal vaccine in non-immunized hyposplenic patients.Gandhi et al evaluated their nonoperative management of blunt splenic injury in pediatric trauma care. They found compared to historical controls, children with blunt splenic injuries who were hemodynamically stable could be safely monitored with a protocol which required 4 days of inpatient care, 3 weeks of quiet home activities, and 3 months of light activity. This protocol seems to allow for safe return to unrestricted activity.Incorrect Answer:Ligaments attach to bone by both direct insertion and indirect insertion. Which of the following most accurately describes the order of the four transition zones of direct insertion?Ligament > fibrocartilage > mineralized fibrocartilage > boneLigament > mineralized fibrocartilage > fibrocartilage > boneLigament > mineralized fibrocartilage > periosteum > boneLigament > Sharpey's fiber > periosteum > boneLigament > periosteum > fibrocartilage > boneThere are two types of tendon/ligament insertion into bone: direct and indirect insertion. The more common, indirect insertion, occurs when the superficial ligament fibers insert into the periosteum. Direct insertion of tendon/ligamentsinto bone occurs through a transition of 4 distinct phases: 1) ligament, 2) fibrocartilage, 3) mineralized fibrocartilage, and 4) bone.While flexing the elbow to perform a biceps curl, what type of muscle contraction is occuring?IsometricIsokineticPlyometricEccentricConcentricConcentric muscle contractions occur when a muscle shortens during contraction, as in the upward motion when performing a biceps curl. An eccentric contraction occurs when a muscle lengthens with contraction, as in the "negative" or lowering motion of a biceps curl. An example of an isometric (muscle contracts while maintaining constant length) contraction would be pushing against an immovable object. An example of an isokinetic (muscle has constant speed of contraction) occurs with specialized equipment like Cybex machines. Plyometric contractions occur when a muscle rapidly lengthens just prior to contraction - like during repetitive box jumping.Woo and Buckwalter describe the mechanisms, barriers, and molecular processes involved in ligament and tendon injury and repair.A 34-year-old laborer has her left foot crushed in a piece of farming equipment as shown in Figure A. All of the following are reasons for a poor outcome following a crush injury to the foot EXCEPT:Workers compensation injuryDevelopment of reflex sympathetic dystrophy (complex regional pain syndrome)Delayed soft-tissue coverage in mangled extremitiesImmediate skeletal stabilizationOngoing litigationThis patient has a mangled extremity. Rigid skeletal stabilization is recommended to enhance soft-tissue healing.Level 4 evidence from Myerson et al found that delayed soft-tissue coverage in mangled extremities correlated with poor outcome. Poor results also occurredif treatment was not immediately initiated (immediate debridement shown in Illustration A), if patients subsequently had neuritis or reflex sympathetic dystrophy, or if patients were involved in ongoing workers' compensation and litigation. Neuroischemia following substantial soft-tissue injury likely plays a role in the development of chronic pain after crush injuries to the foot, either through direct trauma to the peripheral nerves or by intraneural or extraneural fibrosis. This trauma to the nerve may cause chronic neuritis, which then triggers a sympathetically mediated reflex sympathetic dystrophy (complex regional pain syndrome).A 65-year-old man undergoes total knee replacement and is found to have deep vein thrombosis two days later. What molecule isthought to be involved in this process when it is released during surgical dissection?ProthrombinRANKLIL-1bThromboplastinFactor XICorrent answer: 4Thromboplastin is also known more commonly as Tissue Factor (TF), which is involved in the Extrinsic Pathology of the coagulation cascade.During surgical dissection, insults occur to the endothelial walls of blood vessels. There are three ways in which the body reacts to form a clot so that the patient does not bleed excessively. One is via vessel contraction, another is by collagen release, and a third is by tissue thromboplastin release. Thromboplastin release is part of the extrinsic coagulation pathway (seeIllustration A). Thromboplastin release activates Factor VII which activates Factor X which converts prothrombin to thrombin. Thrombin is the catalyst for converting fibrinogen to fibrin which induces clot formation. While this is useful for decreasing bleeding, it is the same mechanism by which a deep venous thrombosis (DVT) develops.Which of the following materials has a Young's modulus of elasticity that is most similar to cortical boneTitaniumZirconiaStainless steelCeramic (Al2O3)Alloy (Co-Cr-Mo)Of the materials listed Titanium has an elastic moduli closest to cortical bone. Titanium is extra-ordinarily light, strong, highly ductile, and corrosion resistant. Titanium is however very notch sensitive and has poor wear resistance.Young Modulus of Elasticity is defined as the stiffness (ability to maintainshape under external loading) of a material. On the stress vs. strain curve it is defined as the slope of the line in the elastic zone (see Illustration A). Young’s modulus is constant and different for each material. The relevant moduli (unit GPa) are approximated below:

DISCUSSION: The patient has diskitis. Administration of IV antibiotics speeds resolution and minimizes recurrence. Bed rest and cast immobilization have been successfully used to treat this disorder but can be associated with prolonged recovery and frequent recurrence, even when oral antibiotics are administered. A perivertebral abscess seen in association with this condition usually resolves without surgery.

There are many causes of rickets and osteomalacia. Renal osteodystrophy is a common complication of chronic renal failure and is one of the most common causes of osteomalacia. Pure osteomalacia is caused by the aluminum in phosphate binders used to treat hyperphosphatemia in renal failure. Desferoxamine is an effective chelator of aluminum in patients with biopsy documented aluminum-associated osteomalacia. Pure osteomalacia also can be caused by hypophosphatemia. The other choices are part of the mechanism of bone changes in renal osteodystrophy.

The 2011 AAOS guideline,Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty, recommends the combined use of mechanical and pharmacological prophylaxis in patients who have a history of previous thromboembolism. This recommendation is a consensus opinion of the work group that established these guidelines because there is no other reliable evidence for this clinical scenario. There is strong evidence against the use of routine duplex scans in patients undergoing hip and knee replacement. The remaining two responses are less appropriate because they do not include the use of mechanical prophylaxis immediately after surgery.

Induction coupling stimulates bone growth by increasing expression of BMP7, BMP2, TGF-beta1, and by increasing osteoblast proliferation. Induction coupling has not been shown to have the effect of decreasing osteoclast differentiation.

Successful antibiotic treatment of acute osteomyelitis should lead to a rapid decline in the CRP. The CRP is the most sensitive study to follow the treatment of osteomyelitis. The CRP should decline after 48 to 72 hours of appropriate treatment. CBC and ESR are helpful in initial evaluation and diagnosis, but remain abnormal in the early phase of treatment regardless of response. Imaging studies are useful for surgical planning or secondarily if the CRP remains elevated.

Acute Charcot neuroarthropathy is driven by a localized inflammatory response marked by elevated pro-inflammatory cytokines (e.g., TNF-alpha, IL-1beta, IL-6). These cytokines powerfully stimulate the Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL) pathway, shifting the balance away from osteoprotegerin (OPG) and leading to unchecked osteoclastogenesis and aggressive bone resorption. This osteolysis characterizes Eichenholtz stage I (development/fragmentation phase).

A Pipkin type II fracture is a femoral head fracture extending superior to the fovea capitis (weight-bearing portion). Because the posterior blood supply (medial circumflex femoral artery) is already at risk from the posterior dislocation, an anterior approach (Smith-Petersen) or a trochanteric flip / surgical hip dislocation is preferred. A Kocher-Langenbeck (posterior) approach requires further dissection of the critical posterior soft tissues and jeopardizes the remaining blood supply to the femoral head.

The popliteal artery is tightly tethered proximally as it exits the adductor hiatus (the opening in the adductor magnus at the distal end of Hunter's canal) and distally where it passes deep to the tendinous arch of the soleus muscle. This rigid fixation makes it highly susceptible to stretch and shear injuries during profound tibiofemoral translation seen in knee dislocations.

The 'corona mortis' (crown of death) is an anatomical variant defined as a vascular anastomosis between the obturator vessels (branching from the internal iliac system) and the external iliac or inferior epigastric vessels. It lies on the posterior aspect of the superior pubic ramus, typically 4 to 6 cm from the symphysis pubis, and is at high risk of iatrogenic injury during anterior pelvic approaches.

A posterior root tear of the medial meniscus disrupts its circumferential fibers. This leads to meniscal extrusion and a complete loss of hoop stresses, effectively mimicking the biomechanical state and rapid chondral wear of a total meniscectomy.

The patient is exhibiting signs of an impending atypical femur fracture (AFF) associated with long-term bisphosphonate use. Because she is symptomatic (thigh pain) and has radiographic evidence of an incomplete fracture (radiolucent line/lateral spiking), prophylactic intramedullary nailing is indicated to prevent completion.

The peroneal (fibular) division of the sciatic nerve is located laterally and is more securely tethered than the tibial division. This anatomy makes it highly susceptible to stretch or contusion injuries during a posterior dislocation of the hip, manifesting as a foot drop.

Eccentric strengthening for tendinopathies has proved most helpful in the later stages of rehabilitation. Although the exact mechanism of the effect of eccentric exercises is not known, the most widely accepted theory is that the absence of concentric stretching disrupts the normal lengthening/shortening cycle which may cause shearing in the tendon and injury to the collagen.

The sympathetic trunk runs longitudinally along the medial border of the psoas. The ilioinguinal nerve emerges along the upper lateral border of the psoas and travels to the quadratus lumborum, and the genitofemoral nerve lies more laterally on the psoas. The ureter is adherent to the posterior peritoneum and falls away from the psoas and the spine in the dissection, as does the aorta.

The standard of care is a legal concept that is elusive and amorphous. Most commonly, the standard of care is that which a reasonable physician would have done under similar circumstances. Expert testimony from other physicians is often required to educate a jury in a medical malpractice trial about the applicable standard of care. As a general rule, treatment that exhibits knowledge, skill, diligence, and care on the part of the physician is likely to fall within the standard of care.

The patient has MRI findings throughout her lumbar spine consistent with old compression fractures. Given the imaging findings and advanced age, she is at high risk for osteoporosis and subsequent fragility fractures. Management should consist of a DEXA scan to evaluate her degree of osteoporosis and begin medical treatment as appropriate. Because acute fracture is unlikely, and she has no neurologic compromise, neither bracing nor surgical treatment is indicated.

A patient sustains a displaced diaphyseal humerus fracture following a motor vehicle accident. Open reduction internal fixation is indicated due to concomitant lower extremity trauma and is planned through an anterior approach. Which intramuscular interval is exploited during the deep dissection of the mid-humerus in this approach?A.   Lateral head of triceps (radial nerve) and brachialis(musculocutaneous nerve)B.   Lateral head of the triceps (radial nerve) and biceps brachii(musculocutaneous nerve)C.   Lateral brachialis (radial nerve) and medial brachialis(musculocutaneous nerve)D.   Brachialis (musculocutaneous nerve) and coracobrachialis(musculocutaneous nerve)