ABOS Hip MCQs (Set 1): Fractures & Arthroplasty 2004

Question 1

During primary total knee arthroplasty, what is the maximum distance the joint line can be raised or lowered before poor motion, joint instability, and increased chance of revision occur?

Explanation

Positioning of the femoral and tibial components is a common cause of early failure of total knee arthroplasty. Two modes of possible position are raising or lowering the joint line from its anatomic level. Raising or lowering the joint line beyond an established threshold can cause limited range of motion, poor patellar function, and possible instability. It has been determined that a threshold of approximately 8 mm provides consistently good results after knee arthroplasty.

Question 2

Figure 1 shows the radiograph of an 18-year-old patient who has severe knee pain. Treatment consisting of osteotomy should be perfomed

Explanation

Very large corrections of tibial deformity can be achieved at or just below the tibial tubercle. This level of osteotomy maintains the relationship between the tubercle and the rest of the joint, does not alter patellofemoral mechanics, and avoids complicating possible future conversion to total knee arthroplasty. High tibial osteotomy is contraindicated for large corrections because of excessive elevation of the tibial tubercle and overhang of the lateral plateau. Correction in the tibial diaphysis creates a zig zag pattern in the tibia by correcting below the deformity and risks nonunion in cortical bone. There is no evidence that the femur is deformed; therefore, femoral osteotomy is not indicated.

Question 3

Figure 2 shows the AP radiograph of an 18-year-old woman with progressive and severe right hip pain. Nonsteroidal anti-inflammatory drugs no longer control her pain. What is the next most appropriate step in management?

Explanation

A concentric hip with acetabular dysplasia in a symptomatic patient is best treated by periacetabular osteotomy. The Salter osteotomy is less optimal because the method has limited correction, is uniaxial, cannot be tailored to the deformity, and lateralizes the entire hip joint, thereby increasing the joint reactive forces. Because the hyaline cartilage of the joint is histologically normal, rotating the hyaline cartilage into an optimal position is preferable to augmenting the acetabulum with a shelf or by Chiari osteotomy. Varus intertrochanteric osteotomy has no significant role in the treatment of acetabular dysplasia. Total hip arthroplasty may be required in the future but should not be the first choice.

Question 4

Which of the following findings is a prerequisite for a high tibial valgus osteotomy for medial compartment gonarthrosis?

Explanation

The indications for high tibial valgus osteotomy include a physiologically young age, arthritis confined to the medial compartment, 10 to 15 degrees of varus alignment on weight-bearing radiographs, a preoperative arc of motion of at least 90 degrees, flexion contracture of less than 15 degrees, and a motivated, compliant patient. Contraindications include lateral compartment narrowing of the articular cartilage, lateral tibial subluxation of greater than 1 cm, medial compartment bone loss, ligamentous instability, and inflammatory arthritis. Naudie D, Bourne RB, Rorabeck CH, Bourne TT: The Insall Award: Survivorship of the high tibial valgus osteotomy. A 10- to 22-year followup study. Clin Orthop 1999;367:18-27.

Question 5

Figures 3a and 3b show the current radiographs of a 58-year-old man who underwent total knee arthroplasty with a cruciate ligament sparing prosthesis 7 years ago. Examination reveals boggy synovitis and moderate pain, particularly anteriorly. Management should consist of

Explanation

The patient has symptoms of synovitis that are most likely the result of the release of particles from the tibial polyethylene. While observation may be warranted in a completely asymtomatic knee, some intervention is indicated for this patient as there is clear radiographic evidence of lysis in both the tibia and femur. The decision about the extent of the revision should be made at the time of surgery. A limited incision technique is not indicated. Grafting (or using graft substitute) the defect is the most appropriate approach for treating the osteolytic lesions. While a posterior stabilized prosthesis might be the solution, surgical findings might dictate otherwise.

Question 6

What is the main benefit of using metal-backed tibial components in total knee arthroplasty?

Explanation

In a normal knee, the hard subchondral bone helps to distribute loads across the joint surface. A metal-backed tibial component in total knee arthroplasty decreases the compressive stresses on the underlying, softer cancellous bone by distributing the load over a larger surface area, particularly when one condyle is loaded. Although metallic base plates also increase the tensile forces on the other condyle when one is loaded and may decrease the thickness of the polyethylene tray, these are not benefits. Compressive forces on the polyethylene tray are increased with metal backing. The conformity of the articular surfaces is not affected by metal backing of the tibial component.

Question 7

Figures 4a and 4b show the radiographs of a 32-year-old man who has right groin pain with activity or prolonged standing. Which of the following factors would not prohibit consideration of acetabular liner exchange and grafting of the defects?

Explanation

Polyethylene particles generated as mechanical wear debris can be phagocytized by macrophages and enter a metabolically active state that releases cytokines, causing periprosthetic bone resorption. Significant osteolysis can occur in the pelvis with a porous-coated cementless socket without loosening of the component. If the acetabular component is modular, well positioned, well-designed with a good survivorship record, and remains undamaged after liner removal, the polyethylene liner can be exchanged and the lytic defects can be debrided and bone grafted. This implant is well positioned, has a good survivorship record, a good locking mechanism, and is modular. The hip arthroplasty needs to be aseptic for consideration of liner exchange. Maloney WJ, Herzwurm P, Paprosky W, Rubash HE, Engh CA: Treatment of pelvic osteolysis associated with a stable acetabular component inserted without cement as part of a total hip replacement. J Bone Joint Surg Am 1997;79:1628-1634.

Question 8

A patient who underwent total knee arthroplasty 6 years ago now reports knee pain for the past 3 days following dental surgery. Cultures of the aspirate are positive for Staphylococcus epidermidis. Management should consist of

Explanation

The patient has an early prosthesis infection as a result of hematogenous seeding from dental surgery. Irrigation and debridement with polyethylene exchange and IV antibiotics have been successful in early postoperative infections; it is less likely to be effective for a late hematogenous infection. Immediate total component exchange also may be effective, but it should be reserved for failure of irrigation and debridement. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 323-337.

Question 9

A 32-year-old woman with systemic lupus erythematosus treated with methotrexate and oral corticosteroids reports right groin pain with ambulation and night pain. Examination reveals pain with internal and external rotation and flexion that is limited to 105 degrees because of discomfort. Laboratory studies show a serum WBC of 9.0/mm3 and an erythrocyte sedimentation rate of 35 mm/h. Figures 5a and 5b show AP and lateral radiographs of the right hip. Further evaluation should include

Explanation

The radiographs show Ficat and Arlet stage 2 osteonecrosis. The femoral head remains round, and there are sclerotic changes in the superolateral quadrant. Patients with systemic lupus erythematosus are at risk for osteonecrosis because of prednisone use and the underlying metabolic changes associated with the condition (hypofibrinolysis and thrombophilia). MRI is the best diagnostic method for detecting osteonecrosis, with a greater than 98% sensitivity and specificity. For this patient, an MRI can assess the contralateral hip for any involvement and can quantify the extent of the lesion. Mont MA, Jones LC, Sotereanos DG, Amstutz HC, Hungerford DS: Understanding and treating osteonecrosis of the femoral head. Instr Course Lect 2000;49:169-185.

Question 10

An otherwise healthy 57-year-old man has persistent, severe hip pain after undergoing total hip arthroplasty 3 months ago. What is the next most appropriate step in management?

Explanation

Any patient who is severely symptomatic this quickly after surgery must be evaluated for infection. Loosening is also a possible cause, but infection must be ruled-out. Bone scans are not helpful at this early postoperative stage. Normal laboratory values argue strongly against infection, but when abnormal, need to be supplemented with a hip aspiration. Aspiration remains the most selective and sensitive measure, especially when linked to a WBC count of the synovial tissues in the joint. There is no indication for an antiobiotic trial because it may make future culture sensitivity more difficult. Drancourt M, Stein A, Argenson JN, et al: Oral rifampin plus ofloxacin for treatment of staphylococcus-infected orthopedic implants. Antimicrob Agents Chemother 1993;37:1214-1218. Duncan CP, Beauchamp C: A temporary antibiotic-loaded joint replacement system for the management of complex infections involving the hip. Orthop Clin North Am 1993; 24: 751-759.

Question 11

A 61-year-old man reports right hip pain and limited motion after undergoing total hip arthroplasty for posttraumatic arthritis 1 year ago. Figure 6 shows an AP radiograph of the pelvis. To improve motion and relieve pain, management should consist of

Explanation

The patient has symptomatic grade IV Brooker heterotopic ossification. Once the bone has matured, it can be excised. Surgical excision should be combined with postoperative irradiation to avoid recurrence. Pharmacologic and irradiation intervention are not successful beyond the perioperative period unless they are combined with surgical excision of mature heterotopic ossification. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 417-451.

Question 12

Osteolysis after total knee arthroplasty can be minimized through prosthetic design features such as

Explanation

The incidence of osteolysis is minimal in studies reporting the use of all polyethylene or monolithic metal-backed tibial components. Osteolysis has been reported in patients with total knee arthroplasties using cementless implants with modular components. Micromotion between the tibial tray and the polyethylene results in backside wear, leading to osteolysis. Osteolysis also has been reported in cemented posterior cruciate-substituting modular components. O'Rourke and associates reported a 16% incidence of osteolysis in patients with a posterior stabilized implant because of the use of modular polyethylene and the subsequent abrasive wear. Oxidation of the polyethylene that is the result of the method of sterilization and shelf life has also been implicated in the high incidence of osteolysis, along with patient factors such as activity level and weight.

Question 13

What type of cementless femoral fixation results in the highest rate of distal femoral osteolysis?

Explanation

Despite the relatively few problems with porous-coated cementless stems, stress shielding and thigh pain do occur. One design feature of proximally coated stems that has been associated with a higher incidence of distal osteolysis is the presence of noncircumferential proximal porous coating. Tapered, modular with sleeve, and hydroxyapatite proximally porous-coated stems have all performed well. Fully porous-coated straight stems have a high survivorship rate as well. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 175-180. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 417-451.

Question 14

When performing a total knee arthroplasty using modular components, what is the minimum recommended thickness of an ultra-high molecular weight polyethylene insert for a tibial component?

Explanation

Polyethylene wear has been identified as a major contributor to failure of total knee implants, of which thickness is an important factor. Several studies have shown that the minimum thickness should be 6 to 8 mm. While Wright and Bartel have shown that 6 to 8 mm has been recommended as the minimum thickness of an ultra-high molecular weight polyethylene insert for a tibial component in total knee arthroplasty, more recent work by Meding and associates and Worland and associates has verified the clinical efficacy of 4 mm of polyethylene in compression-molded anatomic graduated nonmodular components. Bartel DL, Bicknell VL, Wright TM: The effect of conformity, thickness, and material on stresses in ultra-high molecular weight components for total joint replacement. J Bone Joint Surg Am 1986;68:1041-1051. Wright TM, Bartel DL: The problem of surface damage in polyethylene total knee components. Clin Orthop 1991;273:261-263. Meding JB, Ritter MA, Faris PM: Total knee arthroplasty with 4.4 mm of tibial polyethylene: 10-year followup. Clin Orthop 2001;388:112-117.

Question 15

During total knee arthroplasty using a posterior cruciate-retaining design, excessive tightness in flexion is noted, while the extension gap is felt to be balanced. Which of the following actions will effectively balance the knee?

Explanation

Excessive flexion gap tightness can be addressed with a variety of techniques; including: (a) recess and release the posterior cruciate ligament; (b) resect a posterior slope in the tibia; (c) avoid an oversized femoral component that moves the posterior condyles more distally; (d) resect more posterior femoral condyle and use a smaller femoral component placed more anteriorly; and (e) release the tight posterior capsule and balance the collateral ligaments.

Question 16

What is the dominant component of articular cartilage extracellular matrix by weight?

Explanation

Articular cartilage is a highly organized viscoelastic material, and load transmission depends on the specific composition of the extracellular matrix. Articular cartilage is devoid of neural, lymphatic, and blood vessel tissue. The extracellular matrix consists of water, proteoglycans, and collagen. Water comprises most of the wet weight (65% to 80%). Type II collagen comprises 95% of the collagen. The collagen and proteoglycan (keratan sulfate and chondroitin sulfate) matrix and its high water content are responsible for the mechanical properties of the articular cartilage. Buckwalter JA, Mankin HJ: Articular cartilage: Degeneration and osteoarthritis, repair, regeneration, and transplantation. Inst Course Lect 1998;47:487-504.

Question 17

A 70-year-old man underwent primary total knee arthroplasty 3 months ago. Figures 7a and 7b show the radiograph and clinical photograph following incision and drainage of the wound 1 week ago. Aspiration of the joint reveals methicillin-sensitive Staphylococcus aureus. What is the next most appropriate step in management?

Explanation

The overriding factor determining treatment in this case is the appearance of the surgical wound. Based on MacPhearson's work, this "C" wound is best managed with two-stage exchange. The functional outcome is markedly diminished following a knee arthrodesis compared to revision knee arthroplasty. Harwin SF: The diagnosis and management of infected total knee replacement. Seminars Arthroplasty 2002;13:9-22. Goldmann RT, Scuderi GR, Insall JN: 2-stage reimplantation for infected total knee replacement. Clin Orthop 1996;331:118-124.

Question 18

A 35-year-old male laborer with isolated posttraumatic degenerative arthritis of the right hip undergoes the procedure shown in Figure 8. What is the most appropriate position of the right lower extremity?

Explanation

The primary indication for hip arthrodesis is isolated unilateral hip disease in a young, active patient. Avoiding abductor damage and preserving proximal femoral anatomy are imperative to allow conversion to a future total hip arthroplasty. Optimal positioning is 30 degrees of flexion to allow swing-through. Neutral abduction and adduction and slight external rotation allow the most efficient gait while allowing sufficient support in stance. A small degree of adduction is acceptable for a successful hip arthrodesis. Callaghan JJ, Brand RA, Pedersen DR: Hip arthrodesis: A long term follow-up. J Bone Joint Surg Am 1985;67:1328-1335.

Question 19

Which of the following factors can contribute to patellar subluxation following routine total knee arthroplasty?

Explanation

Excessive resection of the lateral facet of the patella can lead to subluxation. Rotational alignment of the components can have a significant impact on patellar tracking. Internal rotation of the femoral component leads to more lateral alignment of the patella within the trochlear groove. Internal rotation and medial placement of the tibial component results in lateralization of the tibial tubercle with an increase in the Q angle. Excessive valgus alignment of the mechanical axis, or insufficient correction of preoperative valgus, has a similar effect on the Q angle, and both can result in a higher rate of tracking problems.

Question 20

When an adult hip is surgically dislocated for relief of femoro-acetabular impingment, what is the risk of postoperative iatrogenic osteonecrosis?

Explanation

In a report of more than 70 hips treated by surgical dislocation, iatrogenic osteonecrosis failed to develop in any of the hips.

Question 21

What is the most frequent late complication of cementless fixation in total knee arthroplasty?

Explanation

The incidence of osteolysis, particularly around fixation screws in the tibia, can be as high as 30%. Stable femoral component fixation is generally maintained. Infection, subluxation of the patella, and stiffness can occur with either cemented or cementless fixation. Peters PC, Engh GA, Dwyer KA, Vinh TN: Osteolysis after total knee arthroplasty without cement. J Bone Joint Surg Am 1992;74:864-876.

Question 22

In the treatment of acetabular dysplasia, what type of pelvic osteotomy leaves the "teardrop" in its original position and redirects the acetabulum?

Explanation

The dial or spherical osteotomy leaves the medial wall or teardrop in its original position and, as a result, is intra-articular. The other pelvic osteotomies (except Chiari) redirect the acetabulum, including the medial wall. The Chiari osteotomy improves coverage without redirecting the acetabulum within the pelvis, and it leaves the teardrop in the same place. Lack W, Windhager R, Kutschera HP, Engel A: Chiari pelvic osteotomy for osteoarthritis secondary to hip dysplasia: Indications and long-term results. J Bone Joint Surg Br 1991;73:229-234. Ganz R, Klaue K, Vinh TS, Mast JW: A new periacetabular osteotomy for the treatment of hip dysplasias: Technique and preliminary results. Clin Orthop 1988;232:26-36.

Question 23

What is the correct order of the elastic modulus of the following materials from greatest to least?

Explanation

In Young's modulus of elasticity, E is a measure of the stiffness of a material and its ability to resist deformation. In the elastic region of the stress-stain curve, E = stress/strain. The moduli of elasticity for these materials are alumina ceramic = 380 Gigapascals (GPa), cobalt-chromium = 210 GPa, stainless steel = 190 GPa, titanium = 116 GPa, and PMMA = 1.1 to 4.1 GPa. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 182-215.

Question 24

Compared to similar patients who do not donate autologous blood, patients with normal baseline hemoglobin who donate autologous blood prior to undergoing primary total hip arthroplasty are likely to

Explanation

Billote and associates compared patients with normal baseline hemoglobin levels who did and did not donate autologous blood prior to total hip arthroplasty. No patients received allogeneic blood perioperatively, and the autologous donors had significantly lower hemoglobin levels at the time of surgery and in the recovery room. Of the autologous donors, 69% received an autologous transfusion. The authors concluded that autologous donation was unnecessary in patients undergoing primary total hip arthroplasty who had a normal hemoglobin. Billote D, Glisson SN, Green D, Wixson RL: A prospective, randomized study of preoperative autologous donation for hip replacement surgery. J Bone Joint Surg Am 2002;84:1299-1304.

Question 25

Which of the following best describes the resultant forces on an increased offset stem when compared with a standard offset stem?

Explanation

The increased emphasis on restoring offset in total hip arthroplasty has implications for the forces applied to the components and the fixation interfaces. Static analysis has shown that with an increased affect, joint reaction force on the articulation is decreased. When the resultant load on the hip is "out of plane" (ie, directed anterior to posterior), there is increased torsion where the stem is turned into more retroversion. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 134-180. Hurwitz DE, Andriaacchi TP: Biomechanics of the hip, in Callaghan J, Rosenberg AG, Rubash HE (eds): The Adult Hip. Philadelphia, PA, Lippincott-Raven , 1998.

Question 26

What is the most common mechanism of failure of a cemented femoral component in total hip arthroplasty?

Explanation

Aseptic loosening is the most common cause of late failure in cemented femoral stems, often due to micro-motion at the cement-bone interface or osteolysis driven by wear debris.

Question 27

Figure 3 shows an AP radiograph of an 80-year-old woman who sustained a low-energy fall. She has a nondisplaced femoral neck fracture. What is the most appropriate definitive management?

Explanation

Nondisplaced femoral neck fractures in the elderly are best treated with in situ fixation using cannulated screws to prevent displacement while preserving the native hip.

Question 28

A 45-year-old active male presents with an intertrochanteric hip fracture. Open reduction and internal fixation with a sliding hip screw is planned. To minimize the risk of screw cut-out, what is the ideal tip-apex distance (TAD)?

Explanation

A tip-apex distance (TAD) of less than 25 mm has been shown to significantly reduce the risk of lag screw cut-out in the treatment of intertrochanteric fractures.

Question 29

Figure 4 shows a pelvic radiograph of a 65-year-old man who is 5 years status post right total hip arthroplasty. He reports a squeaking sound from his hip. What bearing surface combination was most likely used?

Explanation

Squeaking is a specific complication associated with ceramic-on-ceramic bearing surfaces in total hip arthroplasty, often related to stripe wear or component malposition.

Question 30

In a patient undergoing total hip arthroplasty, placement of the acetabular component in excessive retroversion is most likely to result in which of the following complications?

Explanation

Excessive retroversion of the acetabular component predisposes the hip to posterior dislocation, particularly when combined with flexion, adduction, and internal rotation.

Question 31

A 72-year-old woman presents with a displaced femoral neck fracture. She has a history of rheumatoid arthritis and is an independent ambulator. Which of the following is the most appropriate surgical treatment?

Explanation

Total hip arthroplasty is the preferred treatment for displaced femoral neck fractures in independent, active elderly patients, particularly those with preexisting joint disease like rheumatoid arthritis.

Question 32

What is the most accurate method to diagnose an adverse local tissue reaction (ALTR) in a patient with a metal-on-metal total hip arthroplasty?

Explanation

MARS MRI is the most sensitive and specific imaging modality for diagnosing and evaluating the extent of ALTR or pseudotumors in patients with metal-on-metal bearings.

Question 33

A 68-year-old man presents with groin pain 7 years after total hip arthroplasty. Radiographs show eccentric wear of the polyethylene liner and osteolysis in Gruen zones 1 and 7. What is the primary biological mediator responsible for this osteolysis?

Explanation

Polyethylene wear particles are phagocytosed by macrophages, which then release inflammatory cytokines like IL-1, IL-6, and TNF-alpha, leading to osteoclast activation and periprosthetic osteolysis.

Question 34

Figure 6 shows the radiograph of an 82-year-old man who sustained a Vancouver B2 periprosthetic femur fracture around a cemented femoral stem. What is the most appropriate surgical management?

Explanation

A Vancouver B2 fracture is characterized by a loose stem with adequate bone stock. The standard of care is revision to a long uncemented stem, bypassing the fracture by two cortical diameters.

Question 35

During a posterior approach to the hip, which muscle is most critical to protect and repair to minimize the risk of postoperative dislocation?

Explanation

The short external rotators, particularly the obturator internus and piriformis, along with the posterior capsule, should be meticulously repaired during a posterior approach to enhance stability.

Question 36

Which of the following is considered the "safe zone" for acetabular component placement in total hip arthroplasty as described by Lewinnek?

Explanation

Lewinnek's safe zone for acetabular cup placement is historically defined as 40 +/- 10 degrees of abduction (inclination) and 15 +/- 10 degrees of anteversion to minimize dislocation risk.

Question 37

A 25-year-old man sustains a basicervical femoral neck fracture. Which of the following fixation constructs provides the most biomechanical stability for this specific fracture pattern?

Explanation

Basicervical fractures are mechanically unstable and behave more like extracapsular fractures. A sliding hip screw, often supplemented with a derotation screw, provides superior biomechanical stability.

Question 38

Based on Figure 9 showing an intertrochanteric fracture with posteromedial comminution, what is the primary advantage of a cephalomedullary nail over a sliding hip screw?

Explanation

Intramedullary devices have a shorter lever arm because their intramedullary position is closer to the mechanical axis of the femur, making them mechanically advantageous for unstable fracture patterns.

Question 39

A 55-year-old woman complains of lateral hip pain after an uncomplicated total hip arthroplasty performed via a direct anterior approach. What structure is most likely contributing to her symptoms?

Explanation

The direct anterior approach uses the internervous plane between the tensor fasciae latae (TFL) and sartorius. Retraction and trauma to the TFL can lead to postoperative lateral hip pain.

Question 40

When converting an ankylosed (arthrodesed) hip to a total hip arthroplasty, the patient should be counseled about an increased risk of which of the following complications compared to primary THA?

Explanation

Conversion of a hip arthrodesis to a total hip arthroplasty carries a significantly higher risk of nerve injury, particularly to the sciatic nerve, due to altered anatomy and the need to restore leg length.

Question 41

Highly cross-linked polyethylene is primarily used in total hip arthroplasty to reduce which of the following?

Explanation

Highly cross-linked polyethylene (HXLPE) was developed to significantly reduce volumetric wear rates compared to conventional polyethylene, decreasing the incidence of wear particle-induced osteolysis.

Question 42

A 60-year-old male is evaluated for a painful THA. Aspiration yields a synovial fluid white blood cell (WBC) count of 4,500 cells/uL with 85% polymorphonuclear leukocytes. What is the most appropriate next step?

Explanation

A synovial WBC > 3,000 cells/uL with > 80% PMNs in a hip more than 6 weeks post-op is highly suggestive of a periprosthetic joint infection (PJI), making two-stage revision the gold standard treatment.

Question 43

Increasing femoral offset in a total hip arthroplasty has what primary biomechanical effect on the joint?

Explanation

Increasing femoral offset lengthens the abductor moment arm, which decreases the force required by the abductors to stabilize the pelvis. This consequently decreases the overall joint reaction force on the hip.

Question 44

A 75-year-old active community ambulator sustains a displaced femoral neck fracture. Compared to hemiarthroplasty, total hip arthroplasty for this patient is associated with:

Explanation

In active older adults, total hip arthroplasty for displaced femoral neck fractures has a lower reoperation rate and better functional scores than hemiarthroplasty. This benefit comes despite a higher dislocation risk and increased surgical time and blood loss.

Question 45

A 45-year-old man sustains a subtrochanteric femur fracture. Which muscle group is primarily responsible for the flexion and external rotation deformity of the proximal fragment?

Explanation

The proximal fragment in a subtrochanteric fracture is characteristically flexed by the iliopsoas, abducted by the gluteus medius and minimus, and externally rotated by the short external rotators.

Question 46

An 82-year-old woman presents with a periprosthetic femur fracture around a cementless THA stem. Radiographs show a fracture at the tip of the stem, and the stem is radiographically loose. According to the Vancouver classification, what is the most appropriate management?

Explanation

This describes a Vancouver B2 fracture (fracture around the stem, loose prosthesis, adequate bone stock). The standard of care is revision arthroplasty utilizing a long bypass stem to achieve stable diaphyseal fixation past the fracture site.

Question 47

When utilizing a sliding hip screw for an intertrochanteric femur fracture, maintaining a tip-apex distance (TAD) of less than 25 mm is primarily associated with a decreased risk of:

Explanation

Baumgaertner et al. demonstrated that achieving a tip-apex distance (TAD) of less than 25 mm on AP and lateral radiographs significantly minimizes the risk of lag screw cutout in intertrochanteric fractures.

Question 48

A 30-year-old man sustains a Pauwels type III femoral neck fracture. To maximize biomechanical stability and prevent shear failure, the optimal construct should include:

Explanation

Pauwels type III fractures are highly vertically oriented, exposing the fracture to high shear forces. A fixed-angle device such as a sliding hip screw, often supplemented with a derotational screw, provides superior biomechanical stability against shear compared to multiple cancellous screws.

Question 49

A 55-year-old man with a metal-on-metal total hip arthroplasty presents with groin pain 5 years postoperatively. Workup reveals a solid pseudotumor and elevated serum cobalt and chromium levels. This reaction is primarily mediated by which type of hypersensitivity?

Explanation

Adverse local tissue reaction (ALTR) or ALVAL in metal-on-metal implants is primarily mediated by a Type IV delayed hypersensitivity reaction. It is a T-cell mediated response to metal ions (cobalt and chromium).

Question 50

In a patient undergoing primary THA with a ceramic-on-ceramic bearing, what is a specific known complication related to this bearing choice compared to others?

Explanation

Ceramic-on-ceramic articulations have excellent wear properties and minimal osteolysis risk, but they are uniquely associated with "squeaking" (an audible noise during movement) in approximately 1% to 10% of patients.

Question 51

A 65-year-old woman is evaluated for a painful THA 3 years postoperatively. Her serum CRP is 25 mg/L and ESR is 45 mm/hr. Hip aspiration yields 4,500 WBCs/uL with 85% neutrophils. What is the most appropriate next step?

Explanation

This patient has a chronic periprosthetic joint infection, diagnosed by elevated inflammatory markers and an aspirate >3,000 WBCs/uL with >80% PMNs. The gold standard treatment in the United States for chronic PJI is a 2-stage revision arthroplasty.

Question 52

Following a primary THA using a posterior approach, the patient demonstrates a foot drop and inability to extend the great toe. Sensation is decreased over the dorsum of the foot. Which specific neural structure was most likely injured?

Explanation

The peroneal division of the sciatic nerve is the most commonly injured nerve during THA, often due to retractor placement or limb lengthening. Injury presents with foot drop and sensory loss over the anterolateral leg and dorsum of the foot.

Question 53

When performing an anterior approach to the hip (Smith-Petersen), the internervous plane utilized is between muscles innervated by which two nerves?

Explanation

The Smith-Petersen approach uses the superficial internervous plane between the tensor fasciae latae (supplied by the superior gluteal nerve) and the sartorius (supplied by the femoral nerve).

Question 54

To minimize the risk of dislocation, the acetabular component in a THA should ideally be placed within the "safe zone" described by Lewinnek. What are these target angles?

Explanation

Lewinnek's safe zone for acetabular cup placement is historically defined as 40 +/- 10 degrees of abduction (inclination) and 15 +/- 10 degrees of anteversion to minimize dislocation risk.

Question 55

Highly cross-linked polyethylene is now commonly used in THA. The primary negative biomechanical effect of increasing the cross-linking radiation dose in polyethylene is:

Explanation

While high levels of cross-linking significantly decrease the volumetric wear rate of polyethylene, they also diminish its ultimate tensile strength, fatigue strength, and fracture toughness.

Question 56

A patient with a history of severe heterotopic ossification (HO) following a contralateral THA is undergoing an ipsilateral THA. Which of the following is the most proven prophylactic treatment against HO?

Explanation

A single dose of radiation (typically 700 cGy) given within 24 hours preoperatively or postoperatively is a highly effective and proven method for heterotopic ossification prophylaxis. A course of NSAIDs like indomethacin is an alternative proven method.

Question 57

A 28-year-old woman with systemic lupus erythematosus presents with groin pain. Radiographs show a subchondral lucent line (crescent sign) in the femoral head but no gross collapse. What Ficat and Arlet stage does this represent?

Explanation

The crescent sign represents a subchondral fracture and is the hallmark of Ficat Stage III avascular necrosis. It indicates impending mechanical collapse of the femoral head and makes joint-preserving procedures like core decompression less effective.

Question 58

Hip resurfacing arthroplasty is most appropriately indicated for which of the following patient profiles?

Explanation

Hip resurfacing is best suited for young, active males with osteoarthritis and strong bone stock. Contraindications include poor bone quality, large cystic changes, extensive avascular necrosis, and significant leg length discrepancies.

Question 59

Stress shielding of the proximal femur following cementless THA is most commonly seen with which type of femoral stem design?

Explanation

Fully porous-coated, extensively coated stems achieve rigid distal diaphyseal fixation, leading to stress unloading (stress shielding) of the proximal metaphyseal bone. This results in subsequent proximal bone resorption over time.

Question 60

Figure 1 shows the radiograph of a 72-year-old man with severe groin pain 5 years after an uncemented total hip arthroplasty. Inflammatory markers are normal.

What is the most likely cause of his pain if symptoms are exacerbated by active hip flexion against resistance?

Explanation

Iliopsoas impingement typically presents with anterior groin pain that is exacerbated by active hip flexion or a straight leg raise. It is often caused by a prominent anterior edge of the acetabular component rubbing against the iliopsoas tendon.

Question 61

In active, healthy elderly patients who sustain a displaced femoral neck fracture, what is the primary clinical advantage of total hip arthroplasty (THA) compared to hemiarthroplasty?

Explanation

THA provides better functional outcomes and eliminates the risk of progressive acetabular wear and erosion seen with hemiarthroplasty in active patients. However, THA does carry a higher risk of postoperative dislocation compared to hemiarthroplasty.

Question 62

Which of the following vessels provides the primary blood supply to the adult femoral head and is at highest risk of injury during a displaced femoral neck fracture?

Explanation

The medial femoral circumflex artery (MFCA) provides the predominant blood supply to the adult femoral head via its lateral epiphyseal branches. Disruption of this supply in displaced femoral neck fractures leads to a high risk of avascular necrosis.

Question 63

When evaluating a patient for a primary total hip arthroplasty, increasing the femoral head offset without altering leg length will have which of the following biomechanical effects?

Explanation

Increasing femoral offset increases the abductor lever arm, which decreases the abductor force required to maintain pelvic stability. This consequently decreases the overall joint reaction force.

Question 64

A 68-year-old woman sustains a posterior dislocation of her primary total hip arthroplasty 4 weeks postoperatively. Closed reduction is successful in the emergency department. What is the most appropriate initial management?

Explanation

For a first-time early posterior dislocation of a THA successfully treated with closed reduction, initial management consists of immobilization in an abduction brace. This allows the posterior soft tissues and capsule to heal.

Question 65

A 78-year-old community-ambulating woman with mild dementia sustains a displaced femoral neck fracture. According to recent literature, which of the following surgical options is associated with the best functional outcome and lowest reoperation rate?

Explanation

In independent, community-ambulating older adults, total hip arthroplasty for displaced femoral neck fractures provides better functional outcomes and lower reoperation rates compared to internal fixation or hemiarthroplasty.

Question 66

In total hip arthroplasty, which of the following bearing surface combinations is most characteristically associated with the phenomenon of "stripe wear"?

Explanation

Stripe wear is a characteristic wear pattern seen almost exclusively in ceramic-on-ceramic articulations. It often occurs during microseparation when the edge of the cup contacts the femoral head.

Question 67

Six months after a primary total hip arthroplasty, a patient presents with new-onset hip pain. Inflammatory markers are elevated. Aspiration yields 35,000 WBCs/mcL with 90% neutrophils. What is the most appropriate definitive management?

Explanation

For chronic periprosthetic joint infections presenting more than 4 weeks postoperatively, two-stage exchange arthroplasty is the gold standard of treatment. Debridement and modular exchange are typically reserved for acute infections.

Question 68

Which of the following radiographic fracture patterns makes an intertrochanteric femur fracture inherently unstable and prone to collapse with a sliding hip screw?

Explanation

Unstable intertrochanteric fractures are characterized by a loss of the posteromedial calcar support, a reverse obliquity pattern, or a deficient lateral wall. These patterns are typically better treated with an intramedullary device.

Question 69

A 65-year-old man is undergoing preoperative templating for a total hip arthroplasty. To accurately restore leg length and offset, which anatomical landmark is most commonly used to reference the inferior margin of the acetabular component on an AP pelvis radiograph?

Explanation

The radiographic teardrop is a reliable and constant bony landmark on the AP pelvis. It is routinely used to establish the anatomic center of rotation and guide vertical positioning of the acetabular cup.

Question 70

In a cementless, fully porous-coated femoral component, initial mechanical stability (primary fixation) is most heavily dependent on which of the following factors?

Explanation

Primary stability in cementless stems relies on a tight initial "scratch fit" or press-fit between the implant and the host bone. This limits micromotion, which is essential to allow for subsequent secondary biological ingrowth.

Question 71

Following a primary total hip arthroplasty performed via a posterior approach, the patient demonstrates a foot drop and decreased sensation over the dorsum of the foot. Which specific neural structure is most likely injured?

Explanation

The sciatic nerve is the most commonly injured nerve in THA, particularly with a posterior approach. Its peroneal division is anatomically lateral and has less connective tissue support, making it highly susceptible to stretch injury.

Question 72

A 72-year-old woman on long-term bisphosphonate therapy presents with atraumatic thigh pain. Radiographs reveal a transverse, non-comminuted subtrochanteric fracture with a medial spike and lateral cortical thickening. What is the most appropriate surgical treatment?

Explanation

Atypical femur fractures associated with prolonged bisphosphonate use are best treated with intramedullary nailing (such as a cephalomedullary nail). This optimally addresses the diaphyseal stress riser and biomechanically supports healing.

Question 73

According to AAOS guidelines, what is the recommended duration of pharmacological venous thromboembolism (VTE) prophylaxis following an elective total hip arthroplasty?

Explanation

Standard guidelines (including AAOS and ACCP) recommend extending pharmacological VTE prophylaxis to up to 35 days postoperatively for patients undergoing major orthopedic surgeries like total hip arthroplasty.

Question 74

Following surgical fixation of an osteoporotic intertrochanteric hip fracture, when is the optimal time to initiate intravenous zoledronic acid to reduce the risk of subsequent fractures without delaying fracture union?

Explanation

Initiation of bisphosphonate therapy is typically recommended within 2 to 6 weeks postoperatively. This slight delay allows the initial fracture callus to form without disruption, while still significantly reducing future fracture risk.

Question 75

During a total hip arthroplasty utilizing the direct anterior (Smith-Petersen) approach, which of the following internervous planes is utilized superficially?

Explanation

The direct anterior approach exploits the internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 76

A patient presents with mechanical groin pain 10 years after a cementless THA. Radiographs show a continuous, progressive radiolucent line greater than 2 mm extending through all three DeLee and Charnley zones. This finding is most pathognomonic for which of the following?

Explanation

A continuous radiolucent line greater than 2 mm that is progressive and present in all three DeLee and Charnley zones is the radiographic hallmark of aseptic loosening of the acetabular component.

Question 77

A 35-year-old man sustains a completely displaced, vertically oriented (Pauwels Type III) femoral neck fracture after a motor vehicle collision. Which of the following fixation constructs provides the most biomechanically stable fixation for this specific fracture pattern?

Explanation

Vertically oriented (Pauwels Type III) femoral neck fractures experience high shear forces. A sliding hip screw (often with a derotational screw) provides superior biomechanical stability against shear stress compared to parallel cannulated screws.

Question 78

A surgeon utilizes the direct anterior approach (Smith-Petersen) for a primary total hip arthroplasty. Which of the following is an expected potential neurologic complication specific to this surgical approach?

Explanation

The direct anterior approach uses the internervous plane between the sartorius and tensor fasciae latae. The lateral femoral cutaneous nerve is uniquely at risk, which can lead to dysesthesia over the anterolateral thigh.

Question 79

Which of the following is a uniquely recognized complication of ceramic-on-ceramic total hip arthroplasty compared to other modern bearing surfaces?

Explanation

Ceramic-on-ceramic bearings offer the lowest volumetric wear rates of all modern bearing combinations. However, they are associated with unique complications, most notably component fracture and audible squeaking.

Question 80

A 65-year-old man presents with progressive thigh pain 10 years after a cementless total hip arthroplasty. Radiographs demonstrate eccentric positioning of the femoral head within the acetabular shell and focal endosteal radiolucencies in Gruen zones 1 and 7. What is the primary biologic mechanism responsible for these radiographic findings?

Explanation

Polyethylene wear debris in the 0.1 to 1.0-micron size range is phagocytosed by macrophages. These activated macrophages release inflammatory cytokines (e.g., TNF-alpha, IL-1, IL-6) that stimulate osteoclasts, ultimately leading to periprosthetic osteolysis.

Question 81

Figure 4 illustrates a radiograph of an 82-year-old woman who sustained a low-energy fall resulting in a reverse obliquity intertrochanteric femur fracture. Based on the fracture morphology, what is the most biomechanically stable surgical intervention?

Explanation

Reverse obliquity intertrochanteric fractures are inherently unstable and prone to medial displacement of the distal fragment when fixed with a sliding hip screw. An intramedullary nail provides an internal medial buttress, making it the most biomechanically superior construct for this specific fracture pattern.

Question 82

Following a primary total hip arthroplasty performed via a posterolateral approach, the patient develops a foot drop and decreased sensation over the dorsum of the foot. Which of the following intrinsic anatomic factors makes the affected nerve particularly susceptible to this surgical injury?

Explanation

The peroneal division of the sciatic nerve is most commonly injured during total hip arthroplasty due to its more lateral, exposed position. Furthermore, it is structurally composed of larger and fewer fascicles with less protective epineurium compared to the tibial division, increasing its vulnerability to stretch and compression.

Question 83

A 35-year-old patient presents with a vertically oriented, displaced femoral neck fracture (Pauwels Type III) after a motor vehicle collision. To minimize the risk of varus collapse, which of the following internal fixation strategies provides the greatest biomechanical stability?

Explanation

Pauwels Type III (vertical) femoral neck fractures are subjected to high vertical shear forces that frequently lead to varus collapse and fixation failure. A fixed-angle device, such as a sliding hip screw, combined with a supplemental anti-rotation screw is biomechanically superior to multiple cancellous screws in resisting these extreme shear forces.

Orthopedic Board Review Set 675: 100 MCQs for ABOS, OITE, FRCS – Hip Focus

AAOS Orthopedic MCQs (Set 1): Hip Fractures & Arthroplasty | ABOS Board Review 2004

Key Takeaway

AAOS Orthopedic MCQs (Set 1): Hip Fractures & Arthroplasty | ABOS Board Review 2004

Chapter Index