Orthopaedic Science OITE

1. Orthopaedic ScienceOITE October 25, 2006

2. Question 3 • Which of the following arteries provides the vascular pedicle for a medial gastrocnemius rotation flap? • Femoral • Posterior tibial • Peroneal • Medial sural • Inferior medial genicular

3. Question 18 • What statistical term best describes the number of new cases of a disease or condition in a specific population over a given period of time? • Prevalence • Incidence • Frequency • Distribution • Mode

4. Question 39 • During end-stage osteoarthritis, cartilage undergoes what change? • Proteoglycan content is decreased • Water content is decreased • The number of cells per unit area of tissue increases • The percentage of nonaggregating proteoglycans is reduced • The remaining collagen network is well organized

6. Question 49 • Which of the following NSAID’s has been documented as having high gastrointestinal toxicity? • Indomethacin • Celecoxib • Nabumetone • Etodolac • Diflunisal

7. Question 59 • What experimental factor is most likely to cause an increase in the tensile properties of a ligament? • Increase strain rate • Increased temperature • One freeze-thaw cycle • Force application perpendicular to the ligament • Testing with 5° of freedom

9. Question 62 • Which of the following serologic tests is not required by the American Association of Tissue Banks when screening donated musculoskeletal tissues? • HIV 1 and 2 Ab • HTLV-I, II Ab • HbsAg • Syphilis • CMV

10. Question 70 • What is the chemical structure of hydroxyapatite? • Ca10(PO4)6(OH)2 • Ca10(Na4)6(OH)2 • Ca10(Mg4)6(OH)2 • Mg10(Ca4)6(OH)2 • Na10(Ca4)6(OH)2

11. Question 86 • A prospective experimental study is being conducted to compare the relative efficacy of drug A and drug M in treating patients with OA of the knee. Patients are randomly allocated to one of two treatments groups for 3 months and then after 1 month of no treatment, the patients are switched to the other drug treatment for 3 months. This specific design is susceptible to bias if

12. The clinical outcomes are determined in a double-blind fashion • Information is lacking on timing of exposure and outcome • There are carryover effects from the first drug treatment • There is differential loss to follow-up in the two treatment groups • The symmetry of unknown confounders cannot be maintained

13. Question 101 • What is the primary mechanism by which conventional chemotherapy kills cancer cells? • Direct tumor necrosis • Interference with cell-cell adhesion • Induction of apoptosis • Tyrosine kinase inhibition • Cell membrane lysis

14. Question 107 • What is the major source of nutrition of the growth plate? • Synovial blood vessels • Terminal branches of the nutrient artery • Metaphyseal artery • Perichondrial artery • Synovial fluid

16. Question 114 • What term best describes a decrease in physiologic stress in bone caused by a stiffer structure that shares its load? • Stress shielding • Bone resorption • Bone hypertrophy • Bone atrophy • Pressure necrosis

17. Question 117 • When performing a TKA for a 15-degree valgus deformity, the best strategy is to first identify and protect the peroneal nerve. This is best accomplished by identifying the peroneal nerve in which of the following locations? • Posterior border of the semimembranosus tendon • Posterior border of the lateral gastrocnemius muscle • Posterior border of biceps femoris • Tracing the medial sural cutaneous nerve to the popliteal fossa • Lateral joint line beneath the iliotibial tract

18. Question 122 • RNA differs from DNA in which of the following ways? • Its transcription is regulated by proximal or upstream-transcribed sequences • It has a hydrogen group instead of a hydroxyl group at the 2’ position in the ribose • It is double-stranded • It requires a primer to initiate protein synthesis • The base uracil is used in place of thymine

19. Question 128 • Most disease-modifying antirheumatic drugs target which of the following to prevent progression in rheumatoid arthritis? • Bcl-2 • Chondroitin sulfate • Bone morphogenic protein-7 • Collagen type II • Tumor necrosis factor-alpha

20. Question 133 • Which of the following findings is most predictive for postoperative infection in the first week after fracture fixation? • Increasing serial ESR • Increasing serial CRP • Persistent serous drainage • Local erythema • Periosteal new bone formation

21. C-reactive protein in patients who had operative fracture treatment. Scherer MA, Neumaier M, von Gumppenberg S. Department for Trauma and Reconstructive Surgery, University Hospital rechts der Isar der TU-Munchen, Germany. C-reactive protein as an indicator of infection, may help to detect surgical complications early and provide a better outcome for patients. To obtain a baseline for the use of C-reactive protein, the kinetics of C-reactive protein levels of 330 patients who had operative fracture treatment were studied before and after surgery. All patients who had an uneventful postoperative course had similar evolution in their C-reactive protein values: the peak level, which occurred on the second postoperative day, depended on the region of trauma (femoral fractures, 15.4 mg/dL versus ankle fractures, 3.5 mg/dL) and reflected the extent of surgical trauma. Of 47 patients with complicated courses, C-reactive protein proved helpful as a marker in risk stratification and as an early indicator for infection. Of nine patients with a deep wound infection, a high rise of C-reactive protein was recorded, and seven patients showed a rise in the C-reactive protein level before the onset of clinical symptoms. A cut-off level of 14 mg/dL on the fourth day after surgery was recorded for the patients with deep wound infection.

22. Question 138 • What is the most abundant noncollagenous protein in bone? • Osteocalcin • Osteonectin • Osteopontin • Aggrecan • Fibronectin

24. Question 147 • For osteoarticular allografts preserved with cryopreservation and glycerol, what percentage of chondrocytes are viable 5 years after transplantation? • 0% • 1-5% • 10-25% • 50% • More than 90%

25. Observations on massive retrieved human allografts. Enneking WF, Mindell ER. University of Florida Health Center, Gainesville. Radiographic and histological studies of sixteen massive retrieved human allografts were carried out after the allografts had been in situ for four to sixty-five months. The studies demonstrated that union between the allograft and the host took place slowly at cortical-cortical junctions by the formation of an external callus derived from the cortex of the host, and it took place more rapidly at cancellous-cancellous junctions by internal callus advancing from the host into the allograft. Internal repair took place very slowly, was confined to the superficial surface and the ends of the graft, and had involved only 20 per cent of the graft by five years. The deep unrepaired portions of the graft retained their architecture, and where bone cement had been used to fix a prosthetic stem or an intramedullary rod to the allograft, there was no evidence of resorption of bone or loosening of the device. Soft tissues of the host became attached to the graft by deposition of a thin seam of new bone on the surface of the graft. A previous fracture of two grafts had healed before the time of retrieval. 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. The necrotic cartilage functioned well for as long as five years, and as it degenerated, it was covered by a pannus of fibrovascular reparative tissue. Two allografts that had been removed because of rejection were surrounded by an envelope of chronic inflammatory tissue that prevented union, adherence of soft tissue, and internal repair. Internal repair was more advanced about sites of fracture and adjacent to recurrent tumors than in other portions of the graft. These findings suggest that large frozen allografts in humans are osteoconductive rather than osteoinductive.

26. Question 158 • Microscopic examination of ligaments with direct insertions into bone reveals what morphology adjacent to the bony attachment? • Ligament • Fibrocartilage • Mineralized fibrocartilage • Periosteum • Sharpey fibers

28. Question 172 • During orthopaedic surgical dissection, what substance may be released that is involved in the pathogenesis of DVT? • Thromboplastin • Antithrombin III • Prothrombin • Factor X • Factor XII

30. Question 183 • Which of the following commonly used orthopaedic implant materials has torsional and axial stiffness (moduli) that closely mimics bone? • Alumina • Zirconia • Stainless steel • Cobalt-chrome • Titanium

31. Question 190 • What artery supplies blood to the ACL? • Superior medial genicular • Superior lateral genicular • Middle genicular • Inferior medial genicular • Inferior lateral genicular

32. Question 198 • Osteoclasts attach to bone via which of the following receptors? • Vitronectin • Fibronectin • Osteoprotegrin • PDGE • TGF-B

34. Question 207 • Osteolysis in metastatic skeletal disease is primarily mediated by which of the following actions? • Direct tumor erosion by carcinoma pressure necrosis • Tumor-induced host osteoclastic bone resorption • Tumor enzymatic destruction of host bone • Host bone destruction by macrophages • Host bone resorption by tumor neoangiogenesis

36. Question 215 • Which of the following hormones has a catabolic effect on skeletal muscle? • Insulin • Glucagon • Growth hormone • Testosterone • Anabolic steroids

37. Question 234 • What term best describes the extensive processes of osteons that establish contact and communication between osteocytes? • Haversian canals • Canaliculi • Ruffled borders • Howship’s lacunae • Pseudopodia

39. Question 250 • A mesenchymal stem cell differentiates into which of the following? • Osteoclast • Hematopoetic cell • Langerhan’s cell • Lipoblast • Killer T cell

41. Question 261 • With increasing severity of osteoporosis, the mechanical integrity of cemented implant fixation is increased as a result of • Increased trabecular bone strength • Increased cortical bone strength • Increased cement thickness between implant and the bone surface • Greater bone porosity • Greater cement porosity

42. Effect of bone porosity on the mechanical integrity of the bone-cement interface. Graham J, Ries M, Pruitt L. Department of Bioengineering, University of California, Berkeley 94720, USA. jove@socrates.berkeley.edu BACKGROUND: Osteopenia is one factor that may influence the decision about the type of implant fixation to use in total hip arthroplasty. However, clinical studies generally do not associate the outcome of an arthroplasty with the degree of osteopenia. The mechanical integrity of the cement fixation of an implant may be affected by the relative degree of osteopenia, which could account for some of the variable long-term results after total hip arthroplasty performed with cement. The purpose of this study was to determine the effects of bone porosity, trabecular orientation, cement pressure, and cement penetration depth on fracture toughness at the bone-cement interface. METHODS: Trabecular bone from the proximal part of bovine femora was used with a single brand of commercial acrylic bone cement to form compact-tension interface specimens representing a range of bone porosities, orientations, and cement pressures within a clinically achievable range. All specimens were loaded to failure with use of a servohydraulic testing machine, and fracture toughness at the interface was calculated. After testing, images of a representative sample of specimens were made with use of computed tomography to measure the penetration depth of the cement into the bone. RESULTS: Significant correlations were found between fracture toughness and bone porosity, trabecular orientation, and cement pressure, with bone porosity having the strongest effect (p < 0.000015). Examination of the computed tomographic images also showed a significant correlation between fracture toughness and maximum cement penetration depth (p < 0.033), as well as significant partial correlations between maximum and mean penetration depth and bone porosity (p < 0.0037 and p < 0.0028). CONCLUSION: The fracture resistance of the bone-cement interface is greatly improved when the ability of the cement to flow into the intertrabecular spaces is enhanced.

43. Question 267 • Which of the following statements best describes the distribution of compressive loading across the wrist in a patient with neutral ulnar variance? • 20% radius, 80% ulna • 40% radius, 60% ulna • 50% radius, 50% ulna • 60% radius, 40% ulna • 80% radius, 20% ulna