1) Neutral abduction/adduction, 20° to 30° flexion, and neutral internal/external rotation
3) Neutral abduction/adduction, full extension, and neutral internal/external rotation
2) Neutral abduction/adduction, full extension, and neutral internal/external rotation
5) 10° abduction, 20° to 30° flexion, neutral internal/external rotation
4) Neutral abduction/adduction, 15º to 20° flexion, and neutral internal/external rotation
The favored position of hip arthrodesis is 20° to 30° flexion, neutral (or minimal adduction) adduction/abduction, and neutral internal/external rotation (can be slight external rotation). Insufficient flexion makes sitting difficult, while too much flexion makes standing difficult due to increased lumbar lordosis. Abduction and internal rotation should be avoided
■Correct Answer: Neutral abduction/adduction, 20° to 30° flexion, and neutral internal/external rotation
202. (1794) Q1-2193:
Which of the following total hip arthroplasty (THA) positions increases the chances of an anterior dislocation:
1) Flexion, adduction, and internal rotation
3) Extension, adduction, and external rotation
2) Flexion, abduction, and internal rotation
5) Extension, abduction, and internal rotation
4) Extension, adduction, and internal rotation
The most common direction for THA dislocation is posterior. Dislocation may be associated with a posterior approach, poor technique, or previous surgery. Posterior dislocations are accentuated by placing the hip in flexion, adduction, and internal rotation (i.e., rising from a low-seated chair). Less common anterior dislocations occur after an anterior approach or with anteversion of
the cup or femoral component (or both). The position for dislocation is accentuated by extension, adduction, and external rotation
■Correct Answer: Extension, adduction, and external rotation
203. (1795) Q1-2194:
Loosening of a cemented metal-backed polyethylene acetabular component occurs at which of the following junctions:
1) The cement-bone interface
3) The metal-polyethylene interface as a result of micromotion
2) The cement-metal interface
5) Both the cement-bone and cement-metal interface
4) Result of fracture and dissolution through the structure of the cement
Autopsy studies show that the loosening of cemented components occurs at the cement-bone interface. Loosening occurs first at the periphery and proceeds toward the dome. The bone resorption at the cement-bone interface is a response to polyethylene debris
■Correct Answer: The cement-bone interface
204. (1796) Q1-2195:
Placing a screw in the anterior-superior quadrant of the acetabulum places which of the following structures at-risk:
1) External iliaCvein
3) Bladder
2) Internal iliaCartery
5) Common iliaCartery
4) Obturator vein
Placing screws in the acetabular cup in the anterior-superior or anterior-inferior quadrant is not advised due to the proximity of the external iliaCvein and the obturator artery, respectively
■Correct Answer: External iliaCvein
205. (1797) Q1-2196:
During revision surgery for total hip arthroplasty, the accepted standard for the presence of an infection on frozen tissue histological analysis is:
1) Five mononuclear cells per high-powered field
3) Five polymorphonuclear cells per high-powered field
2) Ten mononuclear cells per high-powered field
5) One polymorphonuclear cell per high-powered field
4) Ten polymorphonuclear cells per high-powered field
Frozen section analysis is important in revision surgery to determine why a component has become loose. Ten polymorphonuclear cells per high-powered field lower the sensitivity for infection but do not reduce the specificity to diagnose an infection. Five polymorphonuclear cells per high-powered field are the current standard accepted as diagnostiCfor an infection. Mononuclear cells can be present in the face of aseptiCloosening or polywear disease. Polymorphonuclear cells are diagnostiCof biologiCinfectious response
■Correct Answer: Five polymorphonuclear cells per high-powered field
206. (1798) Q1-2197:
Which of the following is not an indication for an intertrochanteriCosteotomy:
1) Malunion of a fracture in the trochanter region
3) Avascular necrosis involving more than 50% of the femoral head
2) Shortening, lengthening, or derotation osteotomies to realign the extremity
5) Avascular necrosis involving less than 25% of the femoral head
4) Avascular necrosis involving less than 50% of the femoral head
Malunion fractures in the trochanter region and shortening, lengthening, or derotation osteotomies to realign the extremity are indications for an intertrochanteriCosteotomy. Avascular necrosis involving more than 50% of the femoral head is a contraindication for intertrochanteriCosteotomy
■Correct Answer: Avascular necrosis involving more than 50% of the femoral head
207. (1799) Q1-2198:
Normal activities, such as walking 1 km/hour, create forces across the hip joint of times body weight:
1) 1
3) 3
2) 2
5) 5
4) 4
Normal activities increase forces over the hip to three times body weight. Jogging increases forces across the hip by five to eight times body weight
■Correct Answer: 3
208. (1800) Q1-2199:
The principles of osteotomy do not include which of the following:
1) Improving congruency by restoring proper biomechanics
3) Timely intervention with minimal arthrosis
2) Reorienting the weight bearing surfaces to transfer load in compression rather than shear
5) Bone-to-bone aposition
4) Advanced osteoarthritis
Principles of osteotomy include improving congruency by restoring proper mechanics, reorienting the weight bearing surfaces to transfer load in compression rather than shear, bone-to-bone aposition, and timely intervention with minimal arthrosis
■Correct Answer: Advanced osteoarthritis
209. (1801) Q1-2200:
The technical goals of osteotomy should include all of the following except:
1) Eliminating impingement
3) Sacrificing motion
2) Correcting deformity
5) Altering range of motion
4) Restoring pain-free functional range of motion
Technical goals of osteotomy include eliminating impingement, correcting deformity, and restoring a pain-free functional range of motion. Motion should not be gained or lost, but the range can be altered
■Correct Answer: Sacrificing motion
210. (1802) Q1-2202:
The best index to measure acetabular deficiency in the coronal plane is:
1) Tear drop ratio
3) Hilgenreiner angle
2) Center edge angle of Wiberg
5) Greater trochanter-pubiCratio
4) Leg length measurements
Literature from Europe and North America suggests that a patient with acetabular dysplasia whose anteroposterior radiograph shows a center edge angle of Wiberg less than 15° is a good candidate for periacetabular osteotomy
■Correct Answer: Center edge angle of Wiberg
211. (1803) Q1-2203:
In cemented total hip arthroplasty, the initial event in the loosening process of the femoral component occurs at the:
1) Bone-cement interface
3) Thin cement mantle with fatigue fractures of cement
2) Prosthesis-cement interface
5) Large cement mantles
4) Simultaneously at the bone cement and prosthesis cement interface
From the long-term observations of radiograph changes occurring around well-performed cemented total hip arthroplasties, fatigue fracture of cement, especially in areas of thin cement mantles, leads to loss of stability of the femoral component within the cement mantle
■Correct Answer: Thin cement mantle with fatigue fractures of cement
212. (1804) Q1-2204:
Loosening of the acetabular component in a cemented total hip arthroplasty most often occurs at:
1) Bone-cement interface
3) Within the cement
2) Prosthesis-cement interface
5) Within the bone
4) Simultaneously at all three locations
Loosening on the acetabular side most often occurs at the bone-cement interface. Histiocyte cell membrane proliferation incited by particulate generation proceeds from the periphery of the bone-cement interface to the dome of the acetabulum with eventual loosening
■Correct Answer: Bone-cement interface
213. (1805) Q1-2205:
The best fatigue strength for the femoral component is:
1) Coated stainless steel
3) Cold-forged stainless steel
2) Coated chromium cobalt
5) Porous-coated stainless steel
4) Fatigue strength is identical in all
Cold-worked, cold-forged micrograin femoral components provide greater fatigue strength than original casting techniques. Coated stainless steel and coated chromium cobalt have less fatigue strength then the other answer choices
■Correct Answer: Cold-forged stainless steel
214. (1806) Q1-2206:
Femoral components made of which material have the least amount of stiffness:
1) Stainless steel
3) Titanium
2) Chromium cobalt
5) Porous-coated stainless steel
4) All of the above have approximately the same amount of stiffness
Titanium has one-half the material modulus, or stiffness, of chromium cobalt or stainless steel irrespective of the type of porous coating. Titanium also has a high corrosion resistance that is attributed to an oxide layer which is chemically nonreactive to the surrounding tissue
■Correct Answer: Titanium
215. (1807) Q1-2207:
Cement fatigue is the main cause of loosening in a cemented femoral component. Cement is strongest in:
1) Extension
3) Compression
2) Tension
5) Flexion
4) Shear
Cement is stronger in compression than in tension. Stem designs incorporate a taper to the mid and distal stem geometry to transfer the load from the stem to the cement primarily in compression
■Correct Answer: Compression
216. (1808) Q1-2208:
The most durable cemented femoral component design has which of the following surface finishes:
1) RA surface more than 1.5 (average roughness)
3) Matte finish surface
2) Grit-blasted surface
5) None of the above
4) Polished, smooth surface
Femoral components with polished, smooth surfaces and low RA surfaces have proved to be more durable than devices with a rougher finish
■Correct Answer: Polished, smooth surface
217. (1809) Q1-2209:
Noncemented femoral components must be able to resist translation and rotation in all of the following except:
1) Translation in the axial plane
3) Translation in the anteroposterior plane
2) Translation in the medial-lateral plane
5) Pivot shift test
4) Rotation in the coronal plane
Implants must resist translation in the axial, medial-lateral, and anteroposterior planes, as well as resisting rotation in the parasagittal, transverse, and coronal planes
■Correct Answer: Pivot shift test
218. (1810) Q1-2210:
Which uncemented femoral component design provides the best axial and torsional stability in the metaphyses:
1) Single wedge-shaped implant
3) Tapered implant
2) Wedge-shaped metaphyseal-filling implant
5) Diaphyseal-filling implant
4) Extensively porous-coated implant
The metaphysis provides axial and torsional stability for most wedge-shaped, proximally porous-coated, metaphyseal-filling implants. The other types of implants give stability in other areas than the metaphyses
Modularity in noncemented femoral components is popular because the design:
1) Is associated with less loosening
3) Increases particulate debris
2) Allows more versatility in matching proximal and distal femoral geometry
5) Leads to more osteolysis
4) Leads to less osteolysis
Modularity in noncemented femoral components is popular because it allows more versatility in matching proximal and distal femoral geometry. However, additional research is needed to determine if particulate debris leads to osteolysis and failure
■Correct Answer: Allows more versatility in matching proximal and distal femoral geometry
220. (1812) Q1-2213:
Patch porous-coated femoral implants failed because they:
1) Provided a poor distal fit
3) Caused stress fracture at the porous-coated site
2) Increased micromotion of the implant
5) Caused excessive polyethylene wear
4) Provided channels for egress of particulate debris
Patch porous-coated femoral implants failed because they provided channels for the particulate debris to move distally, resulting in diaphyseal osteolysis. A poor proximal fit permits the polyethylene particulate debris to erode around the femoral component
■Correct Answer: Provided channels for egress of particulate debris
221. (1813) Q1-2214:
Which of the following is the preferred thickness for hydroxyapatite coatings:
1) 5 µm
3) 50 µm
2) 20 µm
5) 400 µm
4) 200 µm
Thick hydroxyapatite coatings of 200 µm or more are at risk for fracture and delamination, and thin coatings of 20 µm or less may be resorbed too quickly. The best compromise appears to be 50 µm, which is thick enough so that resorption does not take place too quickly
■Correct Answer: 50 µm
222. (1814) Q1-2215:
PeriprosthetiCbone loss occurs by all of the following mechanisms except:
1) Stress shielding
3) Implant extraction
2) Osteolysis
5) Erosion by infection
4) Impaction grafting
Stress shielding, osteolysis, and implant extraction result in bone loss and must be minimized to maintain bone stock. Impaction grafting is a technique used to increase bone stock
■Correct Answer: Impaction grafting
223. (1815) Q1-2216:
Stress shielding occurs in the proximal femur secondary to:
1) Cemented femoral implants
3) Stiffer implants that allow more distal bone growth
2) Noncemented femoral implants
5) All of the above.
4) Modular designs
Stress shielding occurs secondary to cemented femoral implants, noncemented femoral implants, and stiffer, longer implants that allow more distal bone growth. Stress shielding is also related to the geometry of the implant and bone quality. Modular designs alone do not cause stress shielding
■Correct Answer: All of the above.
224. (1816) Q1-2217:
Thigh pain in noncemented implants is frequently a consequence of:
1) Stem loosening
3) Bony stabilization of implant
2) Fibrous stabilization of implant
5) Stem loosening and bony stabilization of implant
4) Stem loosening and fibrous stabilization
Thigh pain in noncemented implants is frequently a consequence of stem loosening and fibrous stabilization. Thigh pain has not been associated with bony stabilization of the implant because there is no stem loosening if there is adequate bony stabilization
■Correct Answer: Stem loosening and fibrous stabilization
225. (1817) Q1-2218:
All of the following strategies are used to reduce the micromotion between the flexible bone of the femur and a stiff femoral implant except:
1) Providing external porous coatings to the tip of the stem
3) Tapering the stem tip
2) Reducing contact between the tip of the stem and cortical bone
5) Expanding the stem tip so that it compresses on the cortex
4) Cementing the femoral component
Providing external porous coatings to the tip of the stem, reducing contact between the tip of the stem and cortical bone, and tapering the stem tip are strategies that have been used to reduce micromotion. Cementing the femoral component will also reduce micromotion
■Correct Answer: Expanding the stem tip so that it compresses on the cortex
226. (1818) Q1-2219:
All of the following methods are used to reduce the modulus of elasticity of the distal stem except:
1) Stems with slots
3) Enlarging the distal stem tip
2) Slimming and boring out the center of the distal stem
5) Diaphyseal cutouts
4) Hollow distal stems
Stems with slots, diaphyseal cutouts, and hollow distal stems have been used to reduce stem stiffness. Enlarging the distal stem tip increases the modulus of elasticity of the distal stem
■Correct Answer: Enlarging the distal stem tip
227. (1819) Q1-2220:
The major biomechanical function of the femoral component in total hip arthroplasty is to:
1) Optimize leg length
3) Accomodate the femoral head
2) Anchor the prosthetiCfemoral head to the femur
5) Replace poor bone stock
4) Equalize leg length
Anchoring the prosthetiCfemoral head to the femur and substituting for the femoral head and neck are the major biomechanical functions of the femoral component in total hip arthroplasty. One can decrease or increase leg lengths by changing the size of a femoral component, specifically the neck length
■Correct Answer: Anchor the prosthetiCfemoral head to the femur
228. (1820) Q1-2221:
Which of the following is the most common cause of osteonecrosis of the femoral head:
1) Corticosteroids
3) Nitrogen bubbles
2) Displaced transcervical fracture
5) Sickle cell disease
4) Coagulopathies
Displaced transcervical fractures of the cervical neck of the femur are the most common cause of osteonecrosis of the femoral head. Although corticosteroid use, nitrogen bubbles, coagulopathies, and sickle cell disease can also cause osteonecrosis, the highest incidence is seen with displaced transcervical fractures
■Correct Answer: Displaced transcervical fracture
229. (1821) Q1-2222:
In the United States, what percentage of primary total hip replacements are performed due to osteonecrosis:
1) 3%
3) 10%
2) 5%
5) 20%
4) 15%
In the United States, approximately 10% of primary total hip replacements are performed due to osteonecrosis. The majority of total hip replacements occur secondary to osteoarthritis
■Correct Answer: 10%
230. (1822) Q1-2223:
Osteonecrosis is bilateral in what percentage of patients between 25 and 45 years of age with a diagnosis of AVN of one hip:
1) 10%
3) 30%
2) 20%
5) 50%
4) 40%
Adults between 25 and 45 years old are most frequently affected with osteonecrosis, and the condition is bilateral in more than
50% of patients. The condition is usually secondary to alcoholism, corticosteroid use, sickle cell disease, and coagulopathies, as opposed to transcervical neck fractures seen in the elderly
■Correct Answer: 50%
231. (1823) Q1-2224:
All of the mechanisms listed below have been implicated in causing osteonecrosis except:
1) Intravascular coagulation
3) Embolization of fat
2) Hemodilation of blood
5) Sickle cells
4) Nitrogen bubbles
Factors causing intravascular coagulation or thrombosis, not hemodilation, are the most important mechanisms implicated in causing osteonecrosis
■Correct Answer: Hemodilation of blood
232. (1824) Q1-2225:
Which of the following is the most common factor implicated in the development of osteonecrosis:
1) Excessive alcohol intake
3) Nonsteroidal anti-inflammatory drugs (COX 1)
2) Gout medication
5) Nonsteroidal anti-inflammatory drugs (COX 2)
4) Ciprofloxin administration
Excessive alcohol intake and chroniCsteroid administration are the common factors implicated in the development of osteonecrosis. Although there have been case reports indicating nonsteroidal anti-inflammatory drugs, it is questionable if this was the cause
■Correct Answer: Excessive alcohol intake
233. (1825) Q1-2226:
What percentage of patients exposed to heavy alcohol consumption will develop osteonecrosis:
1) 5%
3) 15%
2) 10%
5) 25%
4) 20%
Less than 5% of patients exposed to heavy alcohol consumption develop osteonecrosis
■Correct Answer: 5%
234. (1826) Q1-2227:
What percentage of patients exposed to high dosages of corticosteroids develop avascular necrosis:
1) 10%
3) 30%
2) 20%
5) 50%
4) 40%
Five percent to 10% of patients who receive high doses of corticosteroids develop avascular necrosis. Why only a small percentage of patients develop avascular necrosis is poorly understood, and there may be some genetiCpredisposition
■Correct Answer: 10%
235. (1827) Q1-2228:
Subtle coagulation defects are found in what percentage of patients with osteonecrosis:
1) 20%
3) 40%
2) 30%
5) 70%
4) 50%
Seventy percent of patients with osteonecrosis have some subtle coagulation defect
■Correct Answer: 70%
236. (1828) Q1-2229:
The radiolucent crescent sign on radiographs of the hip:
1) Is present only in the stage II disease avascular necrosis
3) Is caused by collapse of the subchondral trabeculae
2) Occurs in the articular cartilage
5) Is present only after articular cartilage loss
4) Is more clearly seen on magnetiCresonance imaging
The crescent sign is caused by subchondral trabeculae collapse before flattening of the articular surface. The success of core decompression is markedly diminished after this finding is seen on radiographs
■Correct Answer: Is caused by collapse of the subchondral trabeculae
237. (1829) Q1-2230:
The articular cartilage of the femoral head remains intact until after trabecular collapse because:
1) Nutrition comes from the metaphyseal bone
3) Nutrition comes from the epiphysis
2) Nutrition comes from the synovial fluid
5) Nutrition comes from the diaphysis by way of vessels in the metaphysis
4) Nutrition comes from the synovial membrane
Cartilage receives its nutrition through the synovial fluid. Only after collapse of the head is articular cartilage subjected to abnormal mechanical pressures that lead to degeneration
■Correct Answer: Nutrition comes from the synovial fluid
238. (1830) Q1-2231:
On radiograph, what stage of osteonecrosis is associated with a dense necrotiClesion with a sclerotiCborder but no crescent sign:
1) Stage I
3) Stage III
2) Stage II
5) Stage V
4) Stage IV
Stage II of osteonecrosis has good cartilage space without collapse, and a dense necrotiClesion with sclerotiCborder but does not have a crescent sign. Stage I is detected on magnetiCresonance imaging, and stages III and IV are advanced forms of osteonecrosis
■Correct Answer: Stage II
239. (1831) Q1-2232:
The early stages of osteonecrosis are best detected by:
1) Anteroposterior and lateral radiographs
3) MagnetiCresonance image (MRI)
2) Bone scans
5) Single photon computed tomography
4) Computed tomography
If present, radiographiCchanges are detected by MRI in more than 90% of cases. MRI remains the most sensitive test for osteonecrosis and becomes positive before changes are present on the roentgenogram
■Correct Answer: MagnetiCresonance image (MRI)
240. (1832) Q1-2233:
What percentage of hips diagnosed clinically with osteonecrosis go on to femoral head collapse:
1) 30%
3) 50%
2) 40%
5) 80%
4) 70%
Approximately 70% of hips diagnosed clinically with osteonecrosis go on to femoral head collapse. The majority of hips progress to the severe form of the disease and will ultimately require total joint arthroplasty
■Correct Answer: 70%
241. (1833) Q1-2235:
The most promising results with electrical stimulation for treatment of osteonecrosis are with:
1) Direct current
3) Pulsing electromagnetiCfields
2) Capacitive coupling
5) Concurrent bone grafting
4) Indirect current
The results of a multicenter study show promising results with pulsing electromagnetiCfields. Pulsing electromagnetiCfields were found effective as a symptomatiCmanagement in precollapsed lesion and as effective as core decompression
■Correct Answer: Pulsing electromagnetiCfields
242. (1834) Q1-2236:
Core decompression for osteonecrosis of the femoral head does not act through which of the following mechanisms:
1) Decreasing the intraosseous pressure
3) Stimulating the repair process
2) Opening channels for vascular ingrowth
5) Increasing vascularity to the avascular area
4) Increasing structural integrity
Core decompression is affected by a number of mechanisms including decreasing the intraosseous pressure, opening channels for vascular ingrowth, and stimulating the repair process through increased vascularity. Core decompression does not increase structural integrity of the area
■Correct Answer: Increasing structural integrity
243. (1835) Q1-2237:
Urbaniak and associates reported a success rate of treating osteonecrosis before collapse:
1) 10%
3) 50%
2) 30%
5) 90%
4) 70%
Urbaniak and associates reported a success rate of 70% with mild collapse and 80% before collapse. Their results have not been duplicated as yet. The results of their study are much better than those reported with fibular graft
■Correct Answer: 70%
244. (1836) Q1-2238:
The incidence of deep infection complicating primary total hip arthroplasty is:
1) 0.25%
3) 1%
2) 0.5%
5) 3%
4) 2%
The incidence of deep infection in primary total hip replacement is 1%. After revision hip surgery, the percentage increases 3% to
4%. Repeated revisions are associated with increasing infection rates
■Correct Answer: 1%
245. (1837) Q1-2239:
The most common organism implicated in an infected total hip replacement is:
1) Staphylococcus aureus
3) Staphylococcus epidermidis
2) Streptococcus
5) Salmonella typhi
4) Escherichia coli
Staphylococcus epidermidis accounts for 50% to 75% of all arthroplasty infections. This is the most common organism cultured from the skin of preoperative patients
■Correct Answer: Staphylococcus epidermidis
246. (1838) Q1-2240:
Organisms survive on biosynthetiCsurfaces, such as total hips, because of:
1) Sulphate molecules on the surface
3) Polysaccharide biofilm on the surface
2) Their natural occurrence in the human body
5) Mucopolysaccharide present in the synovial fluid
4) They are protected by the sodium hyalurinate
AntibiotiCresistance, the organismâs ability to form a glycocalyx or polysaccharide biofilm, and a slime layer enable the organism to survive on implants. This is one of the reasons why it is difficult to clear up an infection using only antibiotics
■Correct Answer: Polysaccharide biofilm on the surface
247. (1839) Q1-2241:
Preoperatively, what percentage of patients undergoing total hip replacement have methicillin-resistant Staphylococcus aureus
(MRSE) organisms on their skin:
1) 10%
3) 35%
2) 25%
5) 65%
4) 40%
Preoperatively, 25% of skin swabs taken in 100 patients undergoing total hip replacement were MRSE resistant. This is probably a direct result of the overuse of antibiotics by practicing physicians
■Correct Answer: 25%
248. (1840) Q1-2242:
After analyzing 148,359 primary total hip arthroplasties, the Swedish Registry found the lowest risk of revision was:
1) Ventilated suits
3) Palacos-gentamicin cement
2) Laminar flow
5) Palacos cement
4) Sugeon dependent
The Swedish Registry found the lowest risk of revision was in patients who had palacos-gentamicin cement. No effect was found with ventilated suits or laminar flow
■Correct Answer: Palacos-gentamicin cement
249. (1841) Q1-2243:
The erythrocyte sedimentation rate (ESR) returns to normal how long after a total hip replacement:
1) 6 weeks
3) 6 months
2) 2 months
5) 1 year
4) 9 months
The ESR takes more than a year to return to normal after a total hip replacement
■Correct Answer: 1 year
250. (1842) Q1-2244:
An erythrocyte sedimentation rate (ESR) of what level is considered a good cutoff for guiding an index of suspicion for infection:
1) 10 mm/hr
3) 30 mm/hr
2) 20 mm/hr
5) 60 mm/hr
4) 40 mm/hr
With an ESR of 30 mm/hr to 35 mm/hr, sensitivities have been reported from 0.60 to 0.96 and specificities from 0.65 to
