2. Trauma MCQs

Pitchers change rotation during adolescent growth with external rotation of the proximal humerus. The result is increased external rotation and decreased internal rotation, resulting in a normal total arc of motion. External rotation lengthens the arc of acceleration, resulting in increased velocity. The shorter arc of internal rotation, associated with a tight posterior capsule, makes deceleration of the arm more difficult, which may lead to overuse injuries.

DISCUSSION: The Willis reference states “the single most important symptom of impending compartment syndrome is pain out of proportion to the injury." This symptom requires a conscious patient. Most children requiring a reduction for a displaced upper or lower extremity fracture will become comfortable soon after the reduction has been completed. Children requiring frequent analgesia or complaining loudly about pain should be examined very carefully for possible compartment syndrome. The key wording in this question is “earliest indicator”. Pulselessness, paralysis, pallor, and parasthesias are all late indicators.

This patient has sternoclavicular joint septic arthritis with gram positive organisms. Although there is an increased incidence of Pseudomonas aeruginosa infection in IV drug users, S. aureus is still the most common organism.Ross et al states "Staphylococcus aureus is now the major cause ofsternoclavicular septic arthritis in intravenous drug users. Pseudomonas aeruginosa infection in injection drug users declined dramatically with the end of an epidemic of pentazocine abuse in the 1980s."The referenced article by Goldin et al is from the New England Journal of Medicine reports that all of their cases of SC joint septic arthritis were in intravenous drug abusers and that P. aeruginosa grew out of 3 patients and S. aureus grew out of 1 patient.A more recent article by Abu Arab et al reported that Staph aureus was most common even in IV drug users. The review article by Higginbotham and Kuhn note that risk factors for SC joint septic arthritis include hemodialysis, immunocompromise, alcoholism, and HIV. Neisseria gonorrhoeae, fungal, and candida present in HIV patients.Treatment is I&D and appropriate antibiotics, although aspiration and abx have shown some success too. CT and MRI are useful in diagnosis, and open biopsy or aspiration is recommended for definitive diagnosis.A 30-year-old man presents with a distal third tibia fracture that has healed in 25 degrees of varus alignment. The patient is at greatest risk of developing which of the following conditions as a result of this malunion?Degenerative lumbar spine changesIpsilateral ankle pain and stiffnessIpsilateral hip joint degenerative changesContralateral hip joint degenerative changesIpsilateral medial knee degenerative changesCorrect answer: 2A significant malunion of the distal tibia has important consequences for patient outcome, including pain, gait changes, and cosmesis.The first referenced article by Milner et al looked at long-term outcomes of tibial malunions and noted that varus malunion led to increased ankle/subtalar stiffness and pain regardless of the amount of radiographic degenerative changes.The second referenced article by Puno et al reinforced the concept of decreased functional outcomes of the ankle with tibial malunions, and notedthat other lower extremity joints (ipsilateral and contralateral) do not have increased rates of degeneration from such a malunion.A 33-year-old man sustains a femur fracture in a motorcycle accident. AP and lateral radiographs are provided in Figure A. Prior to surgery, a CT scan of the knee is ordered for preoperative planning. Which of the following additional findings is most likely to be discovered?Tibial eminence fractureSagittal plane fracture of the medial femoral condyleSchatzker I tibia plateau fractureCoronal plane fracture of the lateral femoral condyleAxial plane fracture through the medial femoral condyleCorrect answer: 4The "Hoffa fracture" is a coronal plane fracture of the femoral condyle that is often missed on plain radiographs of supracondylar and intercondylar femur fractures. It involves the lateral condyle more frequently than the medial.Identification is important as it may impact operative planning and likely require screw fixation in the anteroposterior plane.Nork et al. reviewed 202 supracondylar-intercondylar distal femoral fractures and found a 38% prevalence of associated coronal plane fractures. The authors recommend CT scan imaging of all supracondylar and intercondylar fractures.Ostermann et al reported on 24 unicondylar fractures of the distal femur treated with open reduction internal fixation with a screw construct. Twenty-three patients acheived satisfactory results at 5 year follow-up. Illustrations A and B are another example of a supracondylar femur fracture with an associated Hoffa fracture identified on CT scan.A 35-year-old woman presents with an elbow injury which includes a coronoid fracture involving more than 50%, a comminutedradial head fracture, and an elbow dislocation. What is the most appropriate treatment?closed reduction and early range of motionradial head resection and lateral collateral ligament reconstructionradial head resection and coronoid open reduction internal fixationradial head arthroplasty and coronoid open reduction internal fixationradial head arthroplasty, coronoid open reduction internal fixation, and lateral collateral ligament repairA terrible triad of the elbow includes dislocation of the elbow with associated fractures of the radial head and the coronoid process. Ring et al. stressed that these injuries are prone to complications and advised against resection of the radial head due to instability, and instead recommended a radial head replacement if too comminuted for ORIF. Coronoid fractures compromise elbow stability as well and require open reduction and internal fixation as with the lateral collateral ligament. McKee et al. showed stable elbows in 34/36 with mean Mayo elbow score of 88 when the standard protocol of coronoid ORIF, radial head repair/replacement, and LCL repair were employed.The talocrural angle of an ankle mortise x-ray is formed between a line perpendicular to the tibial plafond and a line drawn:perpendicular to the medial clear spaceparallel to the talar bodybetween the tips of the malleoliperpendicular to the shaft of the fibularparallel to the subtalar jointCorrect answer: 3The talocrural angle is formed by the intersection of a line perpendicular to the plafond with a line drawn between the malleoli (average = 83+/-4deg). When the lateral malleolus is shortened secondary to fracture, this can lead to increased talocrural angle. This malunion leads to lateral tilt of the talus.Phillips et al looked at 138 patients with a closed grade-4 supination-external rotation or pronation-external rotation ankle fracture. Although the conclusions were limited due to poor follow up, they found the difference in the talocrural angle between the injured and normal sides was a statistically significant radiographic indicator of a good prognosis.Pettrone et al looked at a series of 146 displaced ankle fractures, and the effect of open or closed treatment, and internal fixation of one or both malleoli. They found open reduction proved superior to closed reduction, and in bimalleolar fractures open reduction of both malleoli was better than fixing only the medial side.Illustrations A and B are demonstrations of the talocrural angle.A 33-year-old male sustains the injury shown in Figure A. He is initially treated with a spanning external fixator followed by definitive open reduction internal fixation of the tibia and fibula. His wounds healed without infection or other complications. Two years following surgery, which of the following parameters will most likely predict a poor clinical outcome and inability to return to work?Joint line restorationDegree of fracture displacementTime before definitive ORIFOpen fractureLower level of educationCorrect answer: 5Lower level of education is the parameter that correlated most closely with a poor clinical outcome and inability to return to work.To determine what fracture- and patient-specific variables affect outcome, Williams et al evaluated 29 patients with 32 tibial plafond fractures at a minimum of 2 years from the time of injury. Outcome was assessed by four independent measures: a radiographic arthrosis score, a subjective ankle score, the Short Form-36 (SF-36), and the patient’s ability to return to work. The four outcome measures did not correlate with each other. Radiographic arthrosis was predicted best by severity of injury and accuracy of reduction. However, these variables did not show any significant relationship to the clinical ankle score, the SF-36, or return to work. These outcome measures were more influenced by patient-specific socioeconomic factors. Higher anklescores were seen in patients with college degrees and lower scores were seen in patients with a work-related injury. The ability to return to work was affected by the patient’s level of education.Pollak et al performed a retrospective cohort analysis of pilon fractures. Patient, injury, and treatment characteristics were recorded. The primary outcomes that were measured included general health, walking ability, limitation of range of motion, pain, and stair-climbing ability. A secondary outcome measure was employment status. Multivariate analyses revealed that presence of two or more comorbidities, being married, having an annual personal income of less than $25,000, not having attained a high-school diploma, and having been treated with external fixation with or without limited internal fixation were significantly related to poorer results as reflected by at least two of the five primary outcome measures.What is the most appropriate treatment for a 17-year-old boy who sustained a gunshot wound to his forearm from a handgun with a muzzle-velocity of 1000 feet/second if he is neurovascularly intact and radiographs reveal no fracture?Irrigation and local wound care in the emergency departmentEmergent irrigation and debridement in the operating room with vacuum-assisted wound closureEmergent irrigation and debridement in the operating room with 7 days of intravenous antibioticsWound closure in the emergency department with follow-up wound check in 1 weekExploration and removal of all bullet fragments in the emergency department and 10 day course of oral antibioticsThe question refers to appropriate management of a gunshot wound to the forearm. The first question that must be answered when evaluating gunshot injuries is whether the gunshot is low velocity or high velocity. Low-velocity wounds are less severe, are more common in the civilian population, and are typically attributed to bullets with muzzle velocities below 1,000 to 2,000 feet per second. Tissue damage is usually more substantial with higher-velocity (greater than 2,000 to 3,000 fps) military and hunting weapons. In this question, a muzzle velocity of 1,000 ft/sec is provided. Low velocity injuries with stable, non-operative fractures can be treated with local wound care.The two referenced articles offer guidance for treating low-velocity gunshot injuries with stable, non-operative fracture patterns. The first article by Geissler et al is a retrospective study comparing 25 patients that prospectively received local irrigation and debridement, tetanus prophylaxis and a long acting cephalosporin intramuscularly to a random retrospective sample of 25 patients with similar ballistic-induced fractures and wounds managed by local debridement and 48h of intravenous antibiotics. One infection occurred in each group, requiring further therapy. It was concluded that patients with low-velocity gunshot induced fractures can be managed without the use of short-term intravenous antibiotics with no increased risk of infection.In the second study, Dickey et al evaluated the efficacy of an outpatient management protocol for patients with a gunshot-induced fracture with a stable, non-operative configuration. 41 patients with a grade I or II open, nonoperative fracture secondary to a low-velocity bullet were treated with 1gm of cefazolin administered in the emergency room and a 7-day course of oral cephalexin. No patient developed a deep infection. Thus, local I&D, tetanus, and oral antibiotics for 2-3 days is adequate for low velocity gunshot wounds.Which clinical sign is the most sensitive for the diagnosis of compartment syndrome in a child with a supracondylar humerus fracture?pulselessnesspallorparesthesiaparalysisincreasing analgesia requirementCorrect answer: 5Although pain, pallor, paresthesia, paralysis, and pulselessness are all possible signs and symptoms of compartment syndrome in children with fractures, studies have shown increasing analgesia requirement is more sensitive.Bae et al reviewed thirty-six cases of compartment syndrome in 33 pediatric patients. Approximately 75% of these patients developed compartment syndrome in the setting of fracture. "They found pain, pallor, paresthesia, paralysis, and pulselessness were relatively unreliable signs and symptoms of compartment syndrome in these children. An increasing analgesia requirement in combination with other clinical signs, was a more sensitive indicator ofcompartment syndrome."Whitesides et al summarizes the diagnosis and treatment of acute compartment syndrome. They emphasize the need for early diagnosis, as "muscles tolerate 4 hours of ischemia well, but by 6 hours the result is uncertain; after 8 hours, the damage is irreversible." They recommend fasciotomy be performed when tissue pressure rises past 20 mm Hg below diastolic pressure.A 45-year-old man sustains the injury seen in Figures A and B following a motor vehicle accident. Postoperative radiographs are seen in Figures C and D. Which of the following is the most accurate when comparing outcomes between intramedullary nailing (IMN) and open reduction internal fixation (ORIF) for this injury?Union rates at one year are higher with ORIFInfection rates are higher with IMNFunctional shoulder outcomes at one year are equivalent with IMN and ORIFIatrogenic radial nerve injury rate is higher with ORIFShoulder stiffness rates at one year are equivalent with IMN and ORIFCorrect answer: 3Although shoulder pain and stiffness is increased following IMN compared to ORIF, functional outcome scores at one year have been shown to be equivalentin both treatment groups.Diaphyseal humeral shaft fractures outcomes following IMN and ORIF are under further investigation. Diaphyseal humeral shaft fractures have historically been treated with ORIF, however proponents for IMN cite benefits of less periosteal stripping and soft tissue dissection. Recent investigations have shown outcomes with regard to nonunion, infection, re-operation, and nerve palsy appear equivalent between both groups. Rates of shoulder stiffness and shoulder pain have been demonstrated to be higher in IMN compared to ORIF. American Shoulder and Elbow Scores (ASES) have shown no difference at one year post-operatively.Bhandari et al. performed a meta-anaylsis of 3 prospective randomized trials. They found lower rates of re-operation and shoulder impingement with ORIF of humeral shaft fractures.Wali et al. performed a prospective randomized study of IMN or ORIF on 50 patients with mid-diaphyseal humeral shaft fractures. They found IMN had shorter operative time, shorter hospital stay, and lower blood loss. They found no difference in union rates, complication, or shoulder functional outcomes scores. They conclude IMN to be an effective option for treating mid-diaphyseal humeral shaft fractures.Heineman et al. have recently conducted an update on their meta-analysis to include more recent randomized studies. With the inclusion of newer studies the author found a statistically significant increase in total complication rate with the use of IM nailing compared with ORIF. The authors found no significant difference between the two treatment modalities for the secondary outcomes (nonunion, infection, nerve palsy, re-operation).Figures A and B show a diaphyseal humeral shaft fracture. Figure C and D show postoperative radiographs following intramedullary nailing of a humeral shaft fracture.Incorrect Answers:A 25-year-old female presents complaining of progressive anteromedial pain in her left ankle. She underwent operative fixation 5 months prior at an outside hospital. The operative report indicated that, due to anterior fracture blisters, a direct medial incision was utilized, centered over the posterior colliculus of the medial malleolus, without violation of the deltoid ligament. A radiograph and computed tomographic scan of her initial injury are shown in Figures A and B, respectively. On exam, she has well-healed incisions, exhibits no tenderness to palpation over her hardware, but does endorse pain with deep palpation along the anteromedial joint line. Figure C shows an anteroposterior left ankle radiograph taken today. Labs are obtained and reveal a white blood cell count of 9.0 k/uL (reference range 4.5-11.0 k/uL) and a C-reactive protein value of 0.8 mg/dL (<0.9 mg/dL). What is the next best step in managing her problem?Syndesmotic fixationIntra-articular corticosteroid injectionReferral to physical therapySurgical correction of malunionRemoval of hardwareCorrect answer: 4This patient sustained a supination-adduction (SAD) injury with a vertical shear fracture of her medial malleolus and a fibular avulsion fracture. She sustained a medial plafond articular impaction injury that was not addressed at the time of surgery.In SAD injuries, supination of the foot is combined with inward rotation at the ankle, adduction of the hindfoot, and inversion of the forefoot. This results in the following sequence of events: 1. Talofibular sprain or distal fibular avulsion (equivalent to Weber A). 2. Vertical medial malleolus fracture as the talus strikes the tibia. Associated injuries may include osteochondral damage to the talus and marginal impaction of the medial plafond. It is important to evaluate the medial plafond for articular impaction. When present, an arthrotomy must be performed, typically utilizing an anteromedial incision, with direct visualization of the articular surface to restore the joint line appropriately.Weber et al. provided a review article on corrective osteotomies for malleolar fracture malunions. They stress that malunions can lead to ankle instability, abnormal load transfer, and post-traumatic arthritis. They conclude that corrective osteotomies that restore anatomical alignment show good results in long-term follow-up.Perera et al. provided additional commentary on the surgical reconstruction of malunited ankle fractures. The authors emphasize the link between malunion and poor outcomes. They state that successful salvage procedures involve a clear understanding of the deformity, careful preoperative planning, and a solid understanding of reconstructive techniques. They provide several instructive case examples in their review.McConnell et al. provided a discussion on SAD ankle fractures at their institution and emphasized the importance of recognizing marginal impaction of the tibial plafond when treating these injuries. Of 800 ankle fractures identified over a 5-year period, 44 were SAD injuries, 19 of the 44 displayed a vertical shear fracture of the medial malleolus, and 8 of the 19 demonstrated marginal impaction of the tibial plafond. These 8 impaction injuries were treated with open reduction internal fixation with elevation of the articular impaction; all had good to excellent outcomes without arthritic changes at lastfollow-up.Figure A is an anteroposterior left ankle radiograph demonstrating a SAD injury with a vertical shear fracture of the medial malleolus, a fibular avulsion fracture, and articular impaction of the medial tibial plafond. Figure B is a coronal CT demonstrating articular impaction of the medial plafond. Illustration A is an intra-operative photograph with the medial malleolus retracted allowing inspection of the articular surface; mild anteromedial plafond impaction is present.Incorrect Answers:A 90-year-old female slips and falls at home. She is a community ambulator and has no medical problems. She reports right hip pain at this time. Injury radiographs are shown in Figures A & B. Delay of more than 48 hours may result in:Increased intraoperative timeIncreased 30-day mortalityNo impact on the rate of postoperative pneumoniaHigher rates of blood transfusionIncreased risk of post-operative infectionCorrect answer: 2Figures A & B demonstrate a right, unstable intertrochanteric femur fracture. Surgical stabilization within 48 hours improves short-term and 30-day mortality.Hip fractures are common and mortality rates vary. In the elderly, mortality rates may reach 10% at 1-month, 20% at 4-months, and 30% at 1-year. Time to surgery has found to be a decisive factor. A pre-operative delay may lead to an increase in mortality and adversely influence other clinical outcomes.Clinical guidelines recommend immediate operative stabilization, given the patient is medically fit for surgery.Nyholm et al. performed a retrospective study of the Danish Fracture Database to investigate whether a surgical delay increases 30-day and 90-day mortality rates for patients with proximal femoral fractures. The 30-day and 90-day mortalities were 10.8% and 17.4%, respectively. The risk of 30-day mortality increased with increasing time intervals of more than 12 hours, 24 hours, and more than 48 hours. 90-day mortality increased with a surgical delay of more than 24 hours. They conclude that rapid surgical treatment should be performed by attending orthopaedic surgeons.Moja et al. performed a meta-analysis and meta-regression to assess the relationship between surgical delay and mortality in elderly patients with a hip fracture. They analyzed 35 independent studies with 191,873 patients and 34,448 deaths. The majority of studies had a cut-off of 48 hours. They report that early hip surgery was associated with a lower risk of death and pressure sores. They conclude that early hip fracture surgery appears to provide a survival benefit compared to later intervention.Rodriguez-Fernandez et al. performed a study examining 2 groups with hip fractures. The first group was studied retrospectively and had an average delay of surgical treatment of more than 1-week while the second group was studied prospectively, and had surgical treatment within 48 hours. They found a larger number of complications in the group with a delay in surgical treatment. They conclude that elderly patients with hip fractures should be treated as soon as their medical condition permits.Figures A and B are the AP and lateral radiographs demonstrating a right, unstable intertrochanteric femur fracture. Illustration A is an intertrochanteric femur fracture, stabilized with a cephalomedullary nail.Incorrect Answers:A 22-year-old healthy left hand dominant male presents to the ED with left shoulder pain after falling from an ATV. Figure A is the radiograph of his left clavicle. He is neurovascularly intact and there is no evidence of skin tenting or open fracture. Which of the following most predisposes this patient to nonunion?Diaphyseal fractureFracture displacementAgeMale GenderInjury involving the dominant extremityCorrect answer: 2Displaced clavicle fractures are associated with higher rates of nonunion.Nonunion occurs in roughly 5-6% of clavicle fractures and can result in slower functional return, poor cosmesis and muscle fatigability. Clavicle fractures can be sub-classified using the Allman classification into medial, diaphyseal, and lateral injuries (Illustration A). The Neer classification for diaphyseal injuries describes fractures as "nondisplaced" (less than 100% displacement) and "displaced" (greater than 100% displacement).Robinson et al. performed a prospective cohort study to identify risk factors for nonunion after nonoperative management of clavicle fractures. The overall nonunion rate was 6.2% and was highest in lateral third fractures (11.5%).Diaphyseal fractures had the lowest nonunion rate (4.5%). Additionally, the authors found that the risk for nonunion was increased by advancing age, female gender, fracture displacement, and comminution.Jorgensen et al. performed a systemic review of the literature looking for predictors of non-union and malunion in mid shaft clavicle fractures treated non-operatively. They found fracture comminution, displacement, older age, female gender, and the presence of smoking to be his factors for non-union. Of these, displacement was the most likely factor that can be used to predict nonunion.Figure A demonstrates a displaced left clavicle diaphyseal fracture. Note that the medial fragment is displaced superiorly by the deforming force of the sternocleidomastoid. Illustration A represents the Allman classification.Illustration B demonstrates the deforming forces acting on the clavicle.Incorrect Answers:A 24-year-old male presents with ankle pain after being involved in a motor vehicle accident. His injury radiograph is shown in Figure A. Which of the following has been shown to contribute to the development of post-traumatic arthritis in this injury pattern?Initial superficial zone cartilage cell death via apoptosis at the fracture marginsInitial superficial zone cartilage cell death via apoptosis remote from the fracture marginsInitial superficial zone cartilage cell death via necrosis remote from the fracture marginsInitial superficial zone cartilage cell death via necrosis at the fracture marginsDelayed superficial zone cartilage cell death via necrosis at the fracture marginsFigure A demonstrates a tibial plafond fracture. Initial superficial zone cartilage cell death via necrosis at the fracture margins has been shown to contribute to post-traumatic arthritis.Post-traumatic osteoarthritis typically occurs after an intra-articular fracture. Impacted chondrocytes die by either necrosis or apoptosis, which have both been implicated in post-traumatic osteoarthritis. Initial cell death in the superficial cartilage zones at the fracture margins occurs by necrosis. Apoptosis occurs in a delayed fashion and is mitigated by several bioactive agents.Apoptosis also affects the superficial cartilage zones near the fracture margins. Deep cartilaginous zones and areas away from the fracture margins do not seem to be involved in these processes.McKinley et al. performed a review of the basic science of intra-articular fractures and posttraumatic osteoarthritis. They report that initial damage to the cartilage in combination with the ensuing pathomechanical and pathobiologic response of the cartilage after a fracture contribute to posttraumatic arthritis. Chronic abnormal joint loading is also thought to contribute to this process as well. They conclude that the relative contribution of each is unknown.Tochigi et al. performed a study to determine the distribution and progression of chondrocyte damage after intra-articular ankle fractures. They harvested 7 normal human ankles and subjected them to impaction. They found that immediate superficial zone chondrocyte death was greater in fracture-edge regions than on-fracture regions. Subsequent cell death over the next 48 hours was significantly higher in fracture-edge regions as well. They conclude that cartilage damage in intra-articular fractures was characterized by chondrocyte death at fracture margins.Figure A is an ankle mortise radiograph demonstrating an intra-articular tibial plafond fracture.Incorrect Answers:A 35-year-old male presents with left knee pain after sustaining the injury seen in Figure A. He is neurovascularly intact and can perform a straight leg raise, but has pain with passive range of motion. Figures B and C show an anteroposterior and lateral radiograph of the left knee, respectively. 175 cc of saline is injected into the superolateral quadrant with no egress of fluid from the inferolaterallaceration. What percentage of traumatic arthrotomies would be detected with this test?

By placing the forearm at neutral rotation, as shown in Figures 43c and 43d, the distal fragment has become malrotated by 90 degrees. This is evident by the fact that the bicipital tuberosity is rotated 90 degrees to the radial styloid. Normally, it should be directly opposite (180 degrees) to the radial styloid. The correct alignment was present in the original radiographs shown in Figures 43a and 43b. Another clue to the malrotation in the postreduction radiographs is the difference in the diameters of the opposing radial shafts. To correct this rotational malalignment, the distal fragment needs to be remanipulated into supination so that it is correctly aligned with the supinated proximal radius.

The patient has a very low T-type acetabular fracture; however, the head is not congruent under the dome so surgical reduction is necessary. The anterior and posterior columns are displaced and will move independent from each other. The extended iliofemoral is the only approach allowing for visualization and reduction of each column. A combined anterior and posterior approach may also be used. The timing of surgery should be within the first 3 weeks of injury to optimize chances of obtaining an accurate reduction because this is an important factor in determining outcome.

DISCUSSION: From birth until the age of 4 years, the primary blood supply to the femoral head is from the medial and lateral circumflex arteries that traverse the femoral neck. After the age of 4 years, the contribution of the lateral femoral circumflex artery, which traverses the anterior portion of the femoral neck, becomes negligible. The posterosuperior and posteroinferior retinacular vessels, branches of the medial femoral circumflex artery, become the primary blood supply to the epiphysis. The contribution of the artery of the ligamentum teres is minimal after the age of 4 years.

This question requires one to recall pelvic/sacral anatomy along with classification of sacral fractures which according to the first cited article ) Denis, Clinical Orthopedics, 1988) include the following 3 zones: Zone 1-Ala region, lateral to the foraminal line (i.e. distracters #1 and #5);associated with partial damage to the 5th lumbar root (5.9%). Zone 2-Sacral foramina region, outside of the sacral canal (i.e. distracters #3 and #4); associated with sciatica (28.4%) but rarely bladder dysfunction. Zone 3-Central sacral canal (AKA: Transverse Fx) (i.e. correct answer #2); associated with saddle anesthesia and loss of sphincter tone; neurologic damage (56.7%) and involvement of bowel, bladder, and sexual dysfunction (76.1%).

DISCUSSION: A Weber type B ankle fracture occurs with a supination external rotation mechanism of injury. The fibula generally fails with a spiral fracture pattern. The lag screws provide compression, and the plate acts to neutralize rotational and angular bending forces.

Aminoglycosides work by inhibiting peptide elongation by binding to the 30S-ribosomal subunit.Aminoglycosides are among the oldest classes of antibiotics. They are act by binding to the 30S ribosomal subunit and are considered bactericidal. Due to their effectiveness on Gram-negative bacteria they are often used in conjunction with cephalosporins for treatment of open fractures. Care must be taken when using aminoglycosides due to their potential nephrotoxicity and ototoxicity.Mader et al. present an instructional course lecture reviewing common antibiotics and their mechanisms of action. For aminoglycosides, they comment that their primary use is for aerobic Gram-negative organisms, particularly enterobacter species and P. aeruginosa. Aminoglycosides have realtively poor activity against Gram-positive organisms and should not be used for staph or strep species.Illustration A is a diagram showing the mechanism of action of different antibiotics. Incorrect Answers:

Unreamed nails disrupt the diaphyseal cortical circulation by about 30% as compared to reamed nails that disrupt the circulation about 70%. This aids in healing of open fractures. Because of the smaller diameter used with unreamed nails they are weaker and therefore are made solid without cannulation for added strength. Unreamed nails have a lower rate of infection than plates. External fixators are used for periarticular fractures with compromised soft tissue and when the foreign body might attribute to higher rates of infection like a nail or plate.

DISCUSSION: According to the article by Wang et al the risk of viral transmission following a screened blood donation is: 1 in 1.9 million donations for human immunodeficiency virus (HIV), 1 in 1.8 million donations for hepatitis C virus (HCV), and 1 in 205,000 donations for hepatitis B virus (HBV). West Nile and Human T-cell leukemia viruses are even more rare in the general population, and both are screened in blood banks. Hepatitis A virus is not a blood borne viral disease. It is contracted by the fecal-oral route. Staph aureus is a bacteria, not a virus.

Anterolateral bowing of the tibia is associated with confirmed neurofibromatosis in approximately 50% of patients. Although the risk of fracture with the development of pseudarthrosis exists, the initial treatment consists of bracing through maturity.

In treating tibial plateau fractures, calcium phosphate has been shown to have the least amount of articular subsidence on follow-up examinations. The referenced study by Russell et al noted a significantly increased rate of subsidence at 12 months with autograft as compared to calcium phosphate cement (in types I-VI). The other referenced study by Lobenhoffer et al noted improved radiographic outcomes and earlier weightbearing with usage of calcium phosphate cement.

DISCUSSION: Malposition of a proximal lag screw may result in cut-out similar to that seen with a sliding hip screw. Varus malreduction also can result in implant failure. Studies have shown no difference in complication or healing rates when comparing short and long cephalomedullary nails.

DISCUSSION: Minimally displaced fractures of the proximal humerus have a good outcome if physical therapy is initiated within 2 weeks of the injury. Results are not affected by age, open reduction and internal fixation, or involvement of the greater tuberosity. Immobilization for longer than 3 weeks will often result in stiffness. REFERENCES: Koval KJ, Gallagher MA, Marsicano JG, et al: Functional outcome after minimally displaced fractures of the proximal part of the humerus. J Bone Joint Surg Am 1997;79:203-207. Hodgson SA, Mawson SJ, Stanley D: Rehabilitation after two-part fractures of the neck of the humerus. J Bone Joint Surg Br 2003;85:419-422.

This patient has a posterior knee dislocation with an ischemic limb that does not reverse following reduction. Emergent vascular exploration and reconstruction is indicated. Knee dislocations are associated with popliteal artery injury in 18-45% of cases and range from intimal tears to complete transection. Amputation rates of 85% have been reported if revascularization is delayed greater than 6 to 8 hours. Neurologic injury occurs in 15-40% of cases and is most common after posterolateral dislocation. The peroneal nerve is more commonly injured.

An anterior approach to the sacroiliac (SI) joint is indicated with displaced SI joint dislocations that cannot be reduced with closed or percutaneous techniques. One contraindication to anterior exposure of the SI joint is comminuted sacral fracture patterns.Posterior pelvic ring injuries that are unable to be reduced by closed techniques may require open reduction via anterior or posterior approaches. Relative contraindications to anterior approach include comminuted sacral fractures, morbid obesity, iliac wing external fixation, and ipsilateral diverting colostomy. In the presence of a comminuted sacral fracture, aggressive medial dissection would be required and would place the L5 nerve root at risk.Simpson et al describe their initial results with open reduction and internal fixation of the SI joint via an anterior exposure in a series of 16 patients. They note that sacral alar comminution is a contraindication to the anterior approachJones provides an overview of the operative treatment of posterior pelvic ring injuries. He demonstrates reduction and fixation techniques via both anterior and posterior exposures.Incorrect Answers:

Although femur fractures are common in children, fractures in nonambulatory children carry a very high specificity for abuse. Metabolic bone disease is less commonly a cause of femur fractures. Birth trauma, from which femur fractures have been reported, would have been healed by 5 months of age. Accidental trauma generally does not occur in nonambulatory children. Orthopaedic surgeons, like all physicians, are mandated to report suspected cases of child abuse.

Biomechanical studies dictate that for periprosthetic femur fractures, the fixation plate must overlap the well-fixed femoral stem by a minimum of 2 cortical diameters. This reduces the stress riser effect at the tip of the stem.

This is a Vancouver B2 fracture, characterized by a fracture around a loose stem with adequate surrounding bone stock. The standard of care is revision arthroplasty using a diaphyseal-engaging stem that bypasses the fracture by at least two cortical diameters.