1. General Principles & Basic Science MCQs

A DEXA scan is most appropriately used to establish a baseline score. Even if the bone mineral density is not within the osteoporotic range (T-score less than -2.5), a prior fragility fracture is a strong risk factor for a second fracture. The guidelines of the National Osteoporosis Foundation indicate that, following a fragility hip fracture, active anti-osteoporotic medication should be initiated, whether or not a DEXA scan is performed.

Demographic factors are associated with increased risk for MRSA colonization, so it is important to identify vulnerable patients. Female gender and advanced age reduce the risk for colonization, whereas African American race increases this risk. Urban environments do not influence MRSA colonization.

DISCUSSION: Cell activation and transcription varies with the target cell, the growth factor-receptor combination, and the biologic state of the cell. The growth factors in the transforming growth factor-beta (TGF-β) superfamily signal through serine/threonine kinase receptors. Fibroblast growth factors, insulin-like growth factors, and platelet-derived growth factors signal through tyrosine kinase receptors. Growth hormone is released by the pituitary and circulates to the liver where target cells are stimulated to release insulin-like growth factor. REFERENCES: Lieberman J, Daluiski A, Einhorn TA: The role of growth factors in the repair of bone: Biology and clinical applications. J Bone Joint Surg Am 2002;84:1032-1044. Schmitt JM, Hwang K, Winn SR, et al: Bone morphogenetic proteins: An update on basic biology and clinical relevance. J Orthop Res 1999;17:269-278.

The radiograph and CT scans show a posterior wall acetabular fracture with an associated femoral head fracture. As is the case in most of these injuries, the femoral head fracture is located on the anterior aspect of the femoral head. Surgical dislocation with a trochanteric flip osteotomy as described by Solberg and associates and Henle and associates allows for exposure and treatment of the posterior wall fracture as well as surgical dislocation for treatment of the femoral head fracture. A Smith-Peterson approach or Watson-Jones approach would allow for anterior exposure and may help to address the femoral head fracture, but not the posterior wall fracture. A Kocher-Langenbach approach would allow exposure of the posterior wall fracture, but not the femoral head fracture. An extensile iliofemoral approach is unnecessary for this injury pattern.

24,25-dihydroxycholecalciferol in an inactive form of Vitamin D. High levels of 1,25-dihydroxyvitamin D stimulate the enzymatic production of 24,25-dihydroxyvitamin D, the inactive form of vitamin D, thereby self-regulating the action of 1,25-dihydroxyvitamin D.Vitamin D is paramount to proper calcium homeostasis and has important clinical implications in the orthopaedic patient. Vitamin D3 is synthesized in the skin and is converted to 25-hydroxycholecalciferol in the liver. 25-hydroxycholecalciferol is then converted in the kidney into 1,25-dihydroxycholecalciferol, the active form of vitaminD. The best test to determine Vitamin D deficiency is the measurement of 25-hydroxycholecalciferol, as it has a longer half-life and circulating levels are 1,000x more than 1,25-dihydrocholecalciferol.Patton et al. review the importance of Vitamin D in the orthopaedic patient. They discuss the implications of Vitamin D deficiency, and urge orthopaedic surgeons to be proficient in both the diagnosis and treatment of the condition.Bogunovic et al. measured the levels of 25-hydroxycholecalciferol in 723 patients who were to undergo orthopaedic surgery. 40% of these patients were noted to be deficient in Vitamin D, with the highest rates in patients scheduled to undergo trauma and sports surgery.Illustration A reviews Vitamin D metabolism. 24,25-dihydroxycholecalciferol is referred to as pre-Vitamin D.Incorrect Answers:

DISCUSSION: There is a negative change of calcium balance with a decrease in intestinal absorption and an increase in urinary calcium loss. The reduction of intestinal absorption is accompanied by reduced circulating concentrations of total, but not free 1,25-dihydroxyvitamin D. However, estrogen may also directly regulate intestinal calcium resorption independent of vitamin D. Tubular resorption of calcium is higher in the presence of estrogen. Studies of the levels of PTH in the presence of estrogen are controversial. REFERENCES: Oh KW, Rhee EJ, Lee WY, et al: The relationship between circulating osteoprotegerin levels and bone mineral metabolism in healthy women. Clin Endocrinol (Oxf) 2004;61:244-249. Reid IR: Menopause, in Favus MJ (ed): Primer on Metabolic Bone Diseases and Disorders of Mineral Metabolism, ed 4. Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 55-57.

The utilization of a surgical safety checklist has demonstrated substantial reductions in surgical morbidity and mortality. Checklist use has also demonstrated efficacy in increasing team adherence to life-saving care plans in operating room crises.The World Health Organization concept of a surgical safety checklist concept was validated in 2009 as a way of improving surgical outcomes. Successful implementation of a surgical checklist relies upon surgeon leadership to educate staff on its rationale and the practical components of implementation in the operating room.Haynes et al. evaluated a 19-item surgical safety checklist and evaluated its ability to reduce complications and deaths associated with surgery in a global population. Across 8 diverse hospitals in 8 cities around the world, their study demonstrated that implementation of a pre-surgical checklist resulted in a 50% reduction in mortality (1.5% to 0.8%) and a 37% reduction in inpatient complications (11% to 7%). The patients in the study were over the age of 16 and undergoing non-cardiac surgery.Conley et al. evaluated the effectiveness of implementation of surgical safety checklists in five hospitals using a series of interviews conducted with surgeons. Analysis of the survey results demonstrated that effective implementation relied upon surgeon leadership to explain the necessity of the checklist and how to effectively implement its use. When surgeon leadership failed in these functions, hospital staff failed to comprehend the utility of the checklist and were not able to appropriately use it. These failures eventually led to institutional abandonment of the safety checklist.Arriaga et al. evaluated the utility of checklists to guide the surgical team through intraoperative crisis situations (e.g., massive hemorrhage, cardiac arrest). Their study of 17 surgical teams undergoing 106 simulated surgical-crises demonstrated that use of a crisis checklist led to greater adherence to life-saving steps of a care plan. 97% of participants agreed that they desired a checklist to be present if a crisis were to occur while they themselves were undergoing surgery.Incorrect answers:

The omohyoid muscle crosses the surgical field from inferior lateral to anterior superior traveling from the scapula to the hyoid bone and may need to be transected. The posterior digastric crosses the field as well but higher near C3-4. The other muscles run longitudinally.

The current recommendations for further prevention of any fragility fracture include 1200-1500mg of elemental calcium intake per day and 400-800 IU of vitamin D per day. Of note, these doses are indicated only for prevention and not sufficient for active treatment of osteoporosis (T score less than -2.5).Medications that are approved by the FDA for active treatment of osteoporosis: alendronate, risedronate, raloxifene, estrogen, calcitonin. These medications and preventative measures help to reduce fragility fractures by as much as 50%.Freedman et al. performed a retrospective study that looked at a cohort of patients with fragility fractures and then looked at the type and frequency of osteoporosis related interventions. They found that only 60% of patients actually were either prescribed a medication, given a referral, or ordered additional workup (DEXA scan).Schulman et al. reviewed a series of 80 female patients regarding osteoporosis and bone health, and found that the outpatient sports medicine office setting was an excellent opportunity to educate patients on these topics. The patients' post-education test scores increased significantly after a brief counseling session, and increases in daily calcium intake and exercise levels were also seen.

The AMA report identified communication breakdown as the most common cause of errors that harm patients. It is extremely important to learn to communicate effectively with your patients. Understanding cultural and language differences helps avoid communication errors.

Remember 2 things Dr. Brinker has said about collagen:“collagen dehydrates when it gets older” “water follows the proteoglycans”We all know that as we get older our collagen is less pliable and, specifically, our disks shrink, bulge, and are stiffer. They’re smaller and stiffer because there’s less water. There’s less water because there’s less proteoglycans. There’s less proteoglycans because there’s less biosynthetic function. There’s less biosynthetic function because there are fewer viable cells. Why are there fewer viable cells? I don’t know. Neither do the authors of the Academy Basic Science Textbook. Presumably one day we’ll find the gene(s) / protein(s) / cue(s) that are responsible for the overall slow, programmed decline of our bodies that we call “aging.”[1]back to this question next question[1]Orthopaedic Basic Science 2nd ed. Pg 558

Transient osteoporosis of the hip is an uncommon problem, usually affecting women in the last trimester of pregnancy and middle-aged men. Symptoms include pain in the involved hip with temporary osteopenia; however, there is no joint space involvement. In this patient, the imaging findings are consistent with transient osteoporosis. Short TR/TE (repetition time/echo time) images reveal diffusely decreased signal intensity in the femoral head and intracapsular region of the femoral neck. Increased signal intensity is seen with increased T2-weighting. Within a few months, the pain, as well as the imaging findings, will completely resolve without intervention. Distinguishing the diffuse features of transient osteoporosis of the hip from the segmental findings of osteonecrosis is essential. Unlike transient osteoporosis of the hip, osteonecrosis will have a double-density signal on MRI and may progress radiographically. Surgical intervention and oral corticosteroids are not indicated for treatment. Protected weight bearing until the pain resolves may decrease symptoms while the transient osteoporosis resolves.

Tension pneumothorax occurs when air trapped in the pleural space between the lung and chest wall achieves sufficient pressure to compress the lungs and shift the mediastinum. Urgent needle decompression of the pleural space air followed by definitive chest tube placement is the treatment of choice.

The intrinsic risk for colonization and subsequent infection associated with implants is exacerbated by implants’ tendency to become coated in host proteins such as fibrinogen and fibronectin shortly after implantation. Following initial adherence and colonization, bacteria are thought to form a complex matrix of an extracellular polymeric substance, serving as a protective scaffold in which they can survive despite the competence of the host’s immune system or the presence of antimicrobial agents. There is no evidence that biofilm directly inhibits antibiotics.

The plantaris tendon is often harvested to augment a tendon reconstruction. The origin of the plantaris muscle is on the posterolateral aspect of the distal femur, and the muscle lies lateral to the tibial nerve and the posterior tibial artery. The tendon then courses posteriorly between the soleus and the medial head of the gastrocnemius.

DISCUSSION: The history, physical examination, and radiographs indicate that the patellofemoral pain is most likely caused by excessive lateral patellar pressure and patellar maltracking. Because the radiographs reveal the lateral tilt of the patella and lateral subluxation, the treatment of choice is bilateral lateral releases with anteromedialization of the tibial tubercles. This procedure corrects not only the excessive lateral patellar pressure, but also the lateral subluxation. The use of patella-stabilizing braces or taping may provide temporary relief, but these implements are not well-tolerated and they will not change the underlying biomechanics of the knee. Simple lateral release is indicated for isolated lateral tilt, but it does not correct the lateral subluxation. The use of thermal capsular shrinkage for the medial retinaculum has not been proven to provide long-term correction of the deformity.

DISCUSSION: Cutaneous sensation to the buttock is provided by the superior, middle, and inferior cluneal nerves. The superior cluneal nerves are the lateral branches of the dorsal rami of the upper three lumbar nerves and penetrate deep fascia just proximal to the iliac crest. They pass distally to the skin of the buttock and will be injured if the exposure extends more than 8 cm anterolateral to the posterior superior iliac spine. The lateral femoral cutaneous nerve can be injured in an anterior ilium bone graft. The superior gluteal nerve or even the sciatic nerve can be injured if bone is removed from the sciatic notch or dissection is not kept subperiosteal; however, the rate of injury is far less than cluneal nerve injury. The L5 and S1 nerve roots are anterior and can be injured if the inner table bone is harvested and the dissection is not kept subperiosteal or is too medial; however, the rate of injury still is far less than cluneal nerve injury.

DISCUSSION: Highly cross-linked polyethylene makes material resistant to adhesive wear. Abrasive wear from third bodies does not decrease wear. The fatigue strength of this material is inferior to traditional polyethylene, and its resistance to creep is the same, if not lower, than that of traditional polyethylene.

The most likely diagnosis is toxic synovitis, and the normal C-reactive protein supports that diagnosis. Juvenile inflammatory arthritis is extremely rare to present with hip involvement. The child most likely does not have a bacterial infection because he has improved rapidly without treatment. A normal CBC with differential precludes the diagnosis of leukemia.

DISCUSSION: Fatigue from repetitive loading of the stem with the distal aspect well-fixed resulted in stem failure. If the stem had loosened, it would not have broken. Crevice corrosion occurs at a taper interface; galvanic corrosion occurs at the junction of two metals of differing electrochemical potentials, not along a uniform portion of the implant. REFERENCES: Simon SR (ed): Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486. Gruen TA, McNiece GM, Amstutz HC: “Modes of Failure” of cemented stem-type femoral components: A radiologic analysis of loosening. Clin Orthop 1979;141:17-27.