Orthopedic Hip MCQs: Femoral Neck, THA & FAI Review

Question 1

Figure 29 shows the radiograph of a 55-year-old patient who has recurrent total hip dislocation. Dislocation is most likely to occur in this patient when the hip is in which of the following positions?

Explanation

The patient has an acetabular component that is placed in excessive anteversion; this is confirmed by the shoot-through radiograph. The most common reasons for dislocation of a total hip replacement include inappropriate positioning of the components, inadequate abductor tension, or impingement. Implants placed without adequate total anteversion tend to dislocate posteriorly, and implants with excessive anteversion tend to dislocate anteriorly. Superior dislocations can occur if the acetabular component is placed in a severely vertical position with inadequate lateral coverage.

Question 2

Back pain and ipsilateral knee pain are common long-term sequelae of hip arthrodesis. To limit these problems, what position should be avoided during fusion of the hip?

Explanation

The recommended position for a hip fusion is flexion of 20 degrees to 30 degrees, slight adduction (5 degrees) or neutral, and 10 degrees of external rotation. In long-term follow-up, patients who underwent fusion in abduction had more ipsilateral knee and low back pain than patients who were positioned in adduction. Internal rotation should be avoided to prevent interference with the opposite foot during gait. External rotation facilitates the application of shoe wear. Callaghan JJ, Brand RA, Pederson DR: Hip arthrodesis: A long-term follow-up. J Bone Joint Surg Am 1985;67:1328-1335.

Question 3

Which of the following methods most reliably detects mechanical loosening of the hip?

Explanation

Mechanical loosening of the hip is best revealed by serial radiographs of the prosthetic joint. None of the other methods of evaluation is considered reliable in diagnosing mechanical loosening. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 455-492.

Question 4

A 55-year-old man underwent cementless total hip arthroplasty for advanced painful osteoarthritis of the hip 2 years ago. The follow-up radiograph shown in Figure 30 shows

Explanation

The radiograph shows a well-osseointegrated tapered stem with a metaphyseal porous coating, spot welds in the porous region, and calcar rounding. Trochanteric stress shielding and distal cortical hypertrophy are also signs of ingrown stems but are seen more frequently in association with extensively porous-coated stems exhibiting diaphyseal ingrowth. There is no evidence of lucent lines or a pedestal, signs that suggest instability. Femoral stem subsidence can be determined only by a review of sequential radiographs. Engh CA, Massin P, Suthers KE: Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop 1990;257:107-128.

Question 5

A 52-year-old woman has bicompartmental osteoarthritis following patellectomy. Treatment should consist of

Explanation

The patient has extensive degenerative changes in both the medial and lateral compartments within the knee; therefore, arthroscopic debridement or an osteotomy will not be helpful. A patellar arthroplasty will not address the medial and lateral compartments. Because the extensor mechanism provides a significant amount of anteroposterior stability, a posterior cruciate-substituting total knee arthroplasty is the treatment of choice for this patient. Martin SD, Haas SB, Insall JN: Primary total knee arthroplasty after patellectomy. J Bone Joint Surg Am 1995;77:1323-1330.

Question 6

In hybrid arthroplasty, the use of a polymethylmethacrylate (PMMA) precoated femoral component has been shown to result in

Explanation

Precoating of the femoral stem with PMMA results in increased bonding of the stem to the cement mantle. However, this has not been shown to result in superior survivorship compared with nonprecoated stems of similar design. In one series, the rate of revision of precoated stems was greater than that of nonprecoated cohorts. The wear and infection rates have not been shown to differ between precoated and nonprecoated stems. Sporer SM, Callaghan JJ, Olejniczak JP, Goetz DD, Johnston RC: The effects of surface roughness and polymethylmethacrylate precoating on the radiographic and clinical results of the Iowa hip prosthesis: A study of patients less than fifty years old. J Bone Joint Surg Am 1999;81:481-492.

Question 7

A 72-year-old woman has had progressively increasing pain in the right knee for the past 6 months. She denies any trauma and has no pain in any other joints, but she notes occasional swelling in the knee and a catching sensation. Figures 31a and 31b show the plain radiographs and Figure 31c shows the MRI scan. Treatment should consist of

Explanation

The plain radiographs show a defect in the lateral femoral condyle and narrowing of the lateral joint space. The MRI scan shows a lesion consistent with osteonecrosis of the lateral femoral condyle. The treatment alternatives for this condition are an osteotomy or a total knee replacement, but a total knee replacement is the treatment of choice for a 72-year-old patient. Arthroscopy or an osteochondral bone graft will not address her symptoms. A valgus osteotomy will exacerbate the problem by overloading the lateral joint, which is already diseased. Lotke PA, Ecker ML: Osteonecrosis of the knee. J Bone Joint Surg Am 1988;70:470-473.

Question 8

Which of the following is considered the most appropriate indication for conversion of a hip fusion to total hip arthroplasty?

Explanation

Hip fusion provides successful long-term results (20 to 30 years). The usual mode of failure is symptomatic arthrosis of the lower back, contralateral hip, or the ipsilateral knee. Disabling low back pain is the best indication for conversion and responds well to the procedure. Degenerative changes in the other joints do not respond as well and frequently require replacement arthroplasty. Restoration of limb length is not predictable after conversion to hip replacement. Santore RF: Hip reconstruction: Nonarthroplasty, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 109-115.

Question 9

Which of the following methods is effective in correcting recurrent dislocation following total hip arthroplasty?

Explanation

Recurrent dislocation following total hip arthroplasty is a difficult problem to correct. Studies conducted by the Mayo Clinic show a failure rate of close to 40% with surgical treatment. A variety of methods have been successful, but no specific approach has been reported to be the most predictably successful. To select and institute the proper treatment option, the cause of the dislocation must be identified. Surgical options fall into several broad categories that include increasing soft-tissue tension (trochanteric advancement or longer neck lengths) or more stable articulation (larger diameter head component, bipolar prosthesis, or a constrained component). In a series of total hip arthroplasties done with a constrained cup, the loosening rates of the cup and the stem were reported to be 6% each, comparable to a reported series of complex revision total hip arthroplasties at a similar follow-up interval. Woo RY, Morrey BF: Dislocations after total hip arthroplasty. J Bone Joint Surg Am 1982;64:1295-1306.

Question 10

A 58-year-old woman who underwent a successful total hip replacement for degenerative arthritis 8 years ago reports groin pain for the past 6 months. A radiograph of the hip is shown in Figure 32. At revision, severe deficiency of the posterior column is noted. What reconstructive option would be most appropriate for the acetabulum?

Explanation

The radiograph shows medial migration of the cementless acetabular component, strongly suggesting acetabular discontinuity with a combined segmental and cavitary medial deficiency. The treatment of choice is a morcellized or structural graft, supported with a reconstructive cage bridging the pelvic discontinuity, and a cemented cup. Whiteside LA: Selection of acetabular component, in Steinberg ME, Garino JP (eds): Revision Total Hip Arthroplasty. Philadelphia, PA, Lippincott Williams and Wilkins, 1999, pp 209-220.

Question 11

A patient with a previously pain-free knee replacement now reports a sudden inability to ambulate. Radiographs of the knee are shown in Figures 33a and 33b. Management should consist of

Explanation

The radiographs show a patellar tendon rupture following a total knee replacement. This infrequent, but serious, complication is reported to occur in 0.17% to 1.4% of patients after total knee arthroplasty. Although the radiographs show concerning features such as incomplete tibial and femoral periprosthetic lucencies, it is most important for the surgeon to recognize extensor mechanism disruption. Insall J, Salvati E: Patella position in the normal knee joint. Radiology 1971;101:101-104. Lynch AF, Rorabeck CH, Bourne RB: Extensor mechanism complications following total knee arthroplasty. J Arthroplasty 1987;2:135-140.

Question 12

Which of the following factors will adversely affect bone ingrowth in a revision porous-coated stem?

Explanation

The optimal conditions for bony ingrowth include a pore size of 100 to 400 um, interface micromotion of 50 um or less, intimate contact between the bone and the implant, circumferential porous coating of the implant, and use of a biocompatible material. Stem designs with patch coatings have a poor record of bony ingrowth, especially in the revision setting. Failure of ingrowth in the previous stem would be the result of its own mechanical milieu and would not necessarily predict results for the new stem. Berry DJ, Harmsen WS, Ilstrup D, Lewallen DG, Cabanela ME: Survivorship of uncemented proximally porous-coated femoral components. Clin Orthop 1995;319:168-177. Cook SD, Thomas KA, Haddad RJ Jr: Histologic analysis of retrieved human porous-coated total joint components. Clin Orthop 1988;234:90-101.

Question 13

In the preoperative planning of revision acetabular reconstruction, the surgeon should identify significant posterior column deficiency by noting which of the following radiographic features?

Explanation

Proximal and medial migration of the femoral head usually indicates deficiencies of the dome or anterior column. Wear of the polyethylene may result in osteolysis and impingement, which are not indicative of any major bone deficiency. A significant osteolytic lesion in the ischium may represent a major posterior column deficiency that can create a technical challenge during the reconstruction. Paprosky WG, Magnus RE: Principles of bone grafting in revision total hip arthroplasty: Acetabular technique. Clin Orthop 1994;298:147-155.

Question 14

An 82-year-old woman reports right buttock pain after a car trip. Laboratory studies show an erythrocyte sedimentation rate of 30 mm/h and WBC of 4,600/mm3. Figure 34a shows a plain AP radiograph of the pelvis, and Figure 34b shows a delayed technetium Tc 99m bone scan. Management should consist of

Explanation

The radiograph shows bilateral cemented total hip arthroplasties. The acetabular components are loose bilaterally, but there has been no acute change. Therefore, it is unlikely that the acetabular loosening is contributing to the patient's pain. The bone scan is consistent with a sacral insufficiency fracture. This is best treated with bed rest and pain medication. Activity can be increased as the pain allows. Revision will not address the pain. Newhouse KE, el-Khoury GY, Buckwalter JA: Occult sacral fractures in osteopenic patients. J Bone Joint Surg Am 1992;74:1472-1477.

Question 15

Figures 35a and 35b show the radiographs of a patient who underwent debridement of a chronically infected, fully constrained knee prosthesis and now reports pain and instability despite bracing. History reveals that the patient has had no drainage since undergoing the last debridement 6 months ago. A C-reactive protein level and aspiration are negative for infection. Treatment should now consist of

Explanation

The radiographs show a significant loss of the proximal anterior tibial cortex, consistent with an extensively damaged or deficient extensor mechanism. Such a deficit precludes insertion of another knee arthroplasty. Arthrodesis is the treatment of choice for this patient and is indicated for loss of the extensor mechanism and knee instability. A recent report on arthrodesis following removal of an infected prosthesis showed a union rate of 91% using a short intramedullary nail. Insertion of an antibiotic-impregnated PMMA spacer is not indicated because the rationale for using a spacer is to maintain a space for reinsertion of another prosthesis. Reconstruction of the extensor mechanism would not address the loss of the joint. Amputation is the final treatment option if the arthrodesis fails. Rand JA: Alternatives to reimplantation for salvage of the total knee arthroplasty complicated by infection. J Bone Joint Surg Am 1993;75:282-289. Lai KA, Shen WJ, Yang CY: Arthrodesis with a short Huckstep nail as a salvage procedure for failed total knee arthroplasty. J Bone Joint Surg Am 1998;80:380-388.

Question 16

Which of the following is considered an advantage of metal femoral heads compared with ceramic heads?

Explanation

Ceramic-on-ceramic bearing surfaces have superior tribological properties and show lower linear wear than metal-on-metal implants. However, because of their lower strength and vulnerability to fracture, design considerations constrain the neck-length options available to ensure optimal taper fit.

Question 17

What is the most common result if the acetabulum is rotated too far anteriorly during a periacetabular osteotomy?

Explanation

In patients with hip dysplasia who undergo a periacetabular osteotomy, the authors note that the freed acetabular segment can be overcorrected for the deformity. If it is placed too anteriorly, then hip flexion is limited. Posterior dislocation is a rare complication. The other complications should not occur as a result of this procedure. Hussell JG, Rodriguez JA, Ganz R: Technical complications of the Bernese periacetabular osteotomy. Clin Orthop 1999;363:81-92.

Question 18

Which of the following radiographic views best assesses anterior coverage of the dysplastic hip?

Explanation

Anterior coverage of the hip may be best estimated by the anterior center edge angle of Lequesne and de Seze (analogous to Wiberg's angle), which is measured on the well-defined faux profil view. Evaluation with CT scans also has been described. Klaue K, Wallin A, Ganz R: CT evaluation of coverage and congruency of the hip prior to osteotomy. Clin Orthop 1988;232:15-25.

Question 19

Figure 36a shows the current radiograph of a 65-year-old woman who slipped and fell. History reveals that prior to the fall she was actively functioning without pain. Figure 36b shows a radiograph obtained 1 year ago. Based on the fracture pattern, the failure is most likely related to

Explanation

The radiograph shows a fracture distal to the prosthesis in a stable, apparently well-fixed prosthetic stem. The well-fixed prosthesis-bone composite is stiff, creating a modulus mismatch between the proximal and distal femur. Therefore, the risk of fracture, particularly in osteoporotic bone, is increased at this level. Revision of the stem to a longer construct is unnecessary, and standard plate and screw fixation has been shown to yield union rates of greater than 90%. Nonsurgical treatment of fractures distal to the tip of the prosthesis results in high nonunion rates, reported to be from 25% to 42%. Johansson JE, McBroom R, Barrington TW, Hunter GA: Fracture of the ipsilateral femur in patients with total hip replacement. J Bone Joint Surg Am 1981;63:1435-1442. Bethea JS III, DeAndrade JR, Fleming LL, Lindenbaum SD, Welch RB: Proximal femoral fractures following total hip arthroplasty. Clin Orthop 1982;170:95-106.

Question 20

A 70-year-old man has worn through his metal-backed patellar component and sustained damage to the femoral component. Following removal of the components and debridement of the metal-stained synovium, the surgeon finds that the thickness of the remaining patella is 10 mm. Treatment should now include

Explanation

Revision of a failed patellar component can be difficult because of bone loss and damage to the extensor mechanism. Several authors have advised against reinsertion of a patellar component if the residual patellar thickness is 10 mm or less. Leaving an unresurfaced bony remnant in place at the time of revision or reimplantation surgery has been shown to be a reasonable option; however, the results are of a lower quality when compared with revision surgery where the patellar component can be retained or revised. The other treatment options have not been shown to be effective approaches to this problem. Rand JA: The patellofemoral joint in total knee arthroplasty. J Bone Joint Surg Am 1994;76:612-620. Pagnano MW, Scuderi GR, Insall JN: Patellar component resection in revision and reimplantation total knee arthroplasty. Clin Orthop 1998;356:134-138.

Question 21

A 65-year-old man has a painful and often audible crepitus after undergoing a total knee arthroplasty 8 months ago. His symptoms are reproduced with active extension of about 30 degrees. Examination reveals no effusion or localized tenderness, a stable knee, and a range of motion of 5 degrees to 120 degrees. Radiographs are shown in Figures 37a and 37b. Management should consist of

Explanation

This is a typical presentation of the patellar clunk syndrome. The syndrome usually follows implantation of a posterior stabilized prosthesis. It is thought to be the result of femoral component design and altered extensor mechanics. The condition usually resolves with arthroscopic debridement of the suprapatellar fibrous nodule. Arthrotomy or revision is seldom warranted. Beight JL, Yao B, Hozack WJ, Hearn SL, Booth RE Jr: The patellar "clunk" syndrome after posterior stabilized total knee arthroplasty. Clin Orthop 1994;299:139-142.

Question 22

What clinical parameter will most likely decrease the need for blood transfusion after total joint arthroplasty?

Explanation

Bilateral joint replacement, chronic disease, and preoperative autologous donation all increase the risk of needing blood. Young patients and a high hemoglobin level (greater than 15 g/dL) are considered clinical parameters that decrease the risk for requiring allogenic blood. Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB: An analysis of blood management in patients having a total hip or knee arthroplasty. J Bone Joint Surg Am 1999;81:2-10.

Question 23

Figure 38 shows the radiograph of a 40-year-old woman who reports severe groin pain and lack of motion of the right hip. History reveals that the patient underwent a femoral osteotomy for hip dysplasia approximately 30 years ago. Treatment should include

Explanation

Although the patient is young, a total hip arthroplasty will provide pain relief and improve her range of motion. The arthritis is too advanced for the patient to benefit from an osteotomy. In addition, periacetabular osteotomy and hip arthrodesis do not improve range of motion of the hip. It has not been established that patients with severe osteoarthritis will benefit from arthroscopic debridement of the hip.

Question 24

What is the primary concern for arthrodesis of a failed infected total knee arthroplasty using internal fixation?

Explanation

Arthrodesis of the failed infected total knee arthroplasty may be accomplished by external fixation, intramedullary rod fixation, and dual plates and screws. External fixation runs the risk of pin tract infection, although after its removal, there are no metal surfaces left in place. Intramedullary rods have been used successfully in the treatment of infected total knees, although they also leave metal within the region of the infection. The dual plate technique of knee fusion is useful in patients with rheumatoid arthritis who require fusion in the absence of infection because it provides good initial stability and avoids the use of external pins. However, in the face of infection, the large surface area of the screws and plates may serve as a site for bacteria to hide within a glycocalyx and make eradication of the infection almost impossible.

Question 25

Oxidation of polyethylene after sterilization occurs most rapidly when the implant undergoes

Explanation

The use of gamma radiation to sterilize polyethylene will result in the formation of free radicals in the material that increase the susceptibility of the material to oxidation and wear. The packaging can also have an impact. If the polyethylene is packaged in air, the oxygen in the packaging can significantly oxidize the material on the shelf prior to clinical use. Gas plasma and ethylene oxide sterilization do not appear to increase oxidation of polyethylene. Simon SR (ed): Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486. Wright TM: Ultra-high molecular weight polyethylene, in Morrey BF (ed): Joint Replacement Arthroplasty. New York, NY, Churchill Livingstone, 1991, pp 37-46.

Question 26

A 35-year-old male sustains a vertically oriented (Pauwels type III) displaced femoral neck fracture. What is the most biomechanically stable construct for internal fixation?

Explanation

Pauwels type III fractures have high shear forces. A sliding hip screw with a derotational screw provides superior biomechanical stability compared to multiple cannulated screws for vertically oriented femoral neck fractures.

Question 27

A 65-year-old female presents with recurrent posterior instability of her total hip arthroplasty. Evaluation of her acetabular component reveals 20 degrees of abduction and 0 degrees of anteversion. What is the primary cause of her posterior dislocations?

Explanation

The safe zone for acetabular component placement is typically 40 +/- 10 degrees of abduction and 15 +/- 10 degrees of anteversion. Her cup has 0 degrees of anteversion, predisposing her to posterior dislocation upon flexion and internal rotation.

Question 28

A 28-year-old male hockey player presents with groin pain exacerbated by hip flexion and internal rotation. Radiographs demonstrate a prominent bump at the anterolateral head-neck junction. What radiographic measurement is most appropriate to quantify this deformity?

Explanation

The patient has Cam-type FAI. The alpha angle on a lateral or Dunn view is the standard measurement to quantify the loss of femoral head-neck offset, with >50-55 degrees considered abnormal.

Question 29

A healthy, independent 75-year-old community ambulator sustains a displaced femoral neck fracture. Which of the following is the primary advantage of total hip arthroplasty (THA) compared to bipolar hemiarthroplasty in this patient?

Explanation

In healthy, active elderly patients with displaced femoral neck fractures, THA provides better long-term functional outcomes and lower revision rates due to acetabular wear and groin pain compared to hemiarthroplasty.

Question 30

Following a primary total hip arthroplasty via a direct lateral approach, a patient complains of a pronounced limp. Examination reveals a positive Trendelenburg sign. Which nerve is most likely injured?

Explanation

The superior gluteal nerve innervates the gluteus medius and minimus. Injury during the direct lateral (Hardinge) approach, especially if splitting the gluteus medius >5 cm proximal to the greater trochanter, leads to abductor weakness and a Trendelenburg lurch.

Question 31

A 40-year-old female presents with activity-related hip pain. Radiographs demonstrate a "crossover sign" on the AP pelvis view. This finding is indicative of which of the following?

Explanation

The crossover sign occurs when the anterior wall of the acetabulum crosses the posterior wall on an AP radiograph. This indicates acetabular retroversion, a common cause of focal Pincer-type FAI.

Question 32

A 55-year-old male with a metal-on-metal total hip arthroplasty presents 5 years postoperatively with vague groin pain and a palpable mass. Serum cobalt and chromium levels are elevated. MRI with MARS reveals a large cystic mass communicating with the joint. What is the most appropriate next step in management?

Explanation

The patient has an Adverse Local Tissue Reaction (ALTR/pseudotumor) secondary to metal-on-metal wear. Management involves revision to a non-metal-on-metal bearing surface and excision of the pseudotumor to prevent further tissue destruction.

Question 33

A 42-year-old female presents 9 months after internal fixation of a displaced femoral neck fracture. She complains of persistent groin pain with weight-bearing. Radiographs show a prominent screw backing out and a visible radiolucent line across the fracture site. What is the most appropriate surgical treatment?

Explanation

In a young patient with a femoral neck nonunion and a viable femoral head, a valgus intertrochanteric osteotomy converts shear forces into compressive forces, promoting fracture healing.

Question 34

A 72-year-old female sustains a fall 5 years after an uncemented THA. Radiographs show a fracture at the tip of the femoral stem. The stem is radiographically loose with subsidence. According to the Vancouver classification, what type of fracture is this and what is the standard treatment?

Explanation

A fracture around or just below the stem with a loose implant but adequate bone stock is a Vancouver B2 fracture. Standard treatment is revision to a longer diaphyseal-engaging stem bypassing the fracture by at least 2 cortical diameters.

Question 35

A 38-year-old male with Cam-type FAI is considering hip arthroscopy for osteochondroplasty and labral repair. Which of the following preoperative radiographic findings is the strongest predictor of a poor clinical outcome and early conversion to total hip arthroplasty?

Explanation

Pre-existing osteoarthritis, defined radiographically as joint space width < 2 mm or Tonnis grade 2-3, is the strongest negative prognostic factor for hip arthroscopy in FAI, often leading to early conversion to THA.

Question 36

The blood supply to the femoral head is a critical factor in the development of avascular necrosis following a femoral neck fracture. Which vessel provides the primary blood supply to the adult femoral head?

Explanation

The medial femoral circumflex artery (MFCA), specifically its lateral epiphyseal branches, provides the predominant blood supply to the weight-bearing dome of the adult femoral head.

Question 37

A 68-year-old male presents with increasing hip pain 3 years after a primary THA. Aspiration of the hip joint yields fluid with a WBC count of 4,500 cells/uL and 85% neutrophils. Radiographs show progressive radiolucent lines around the acetabular component. What is the most appropriate definitive management?

Explanation

The patient has a chronic periprosthetic joint infection (symptoms > 4 weeks, high WBC > 3,000 in the late setting). The gold standard treatment in North America is a two-stage revision using an antibiotic-eluting spacer followed by delayed reimplantation.

Question 38

During physical examination of a patient suspected of having Femoroacetabular Impingement (FAI), the examiner performs the FADIR test. Which of the following motions are combined during this provocative maneuver?

Explanation

The anterior impingement test (FADIR) combines Flexion, Adduction, and Internal Rotation. It is highly sensitive for detecting anterior labral tears and evaluating FAI.

Question 39

A 25-year-old male presents with deep groin pain worsened by hip flexion and internal rotation. Radiographs show a pistol grip deformity. What is the primary mechanism of cartilage damage in this condition?

Explanation

Cam impingement is caused by an aspherical femoral head (pistol grip) squeezing into the acetabulum during flexion. This causes shear forces that lead to delamination of the anterosuperior acetabular cartilage at the chondrolabral junction.

Question 40

A 32-year-old female sustains a displaced, completely off-ended, Pauwels type III femoral neck fracture. What is the most appropriate definitive management to minimize the risk of nonunion while maximizing biomechanical stability?

Explanation

In young adults with a vertical (Pauwels III) displaced femoral neck fracture, a fixed-angle device such as a dynamic hip screw with a derotational screw provides superior biomechanical stability against shear forces compared to cancellous lag screws.

Question 41

A 65-year-old patient undergoes a primary THA. Postoperatively, the acetabular component is found to have 10 degrees of anteversion and 30 degrees of inclination. The patient is at highest risk for dislocation in which of the following positions?

Explanation

An acetabular component with relative retroversion (10 degrees of anteversion is lower than the normal target of 15-20 degrees) predisposes the hip to posterior dislocation. Posterior dislocation typically occurs with the hip in flexion, adduction, and internal rotation.

Question 42

A 58-year-old male with a metal-on-metal total hip arthroplasty presents with new-onset groin pain and a palpable mass. MRI with MARS sequencing reveals a large cystic pseudo-tumor. Which of the following serum markers is most likely elevated?

Explanation

Adverse local tissue reaction (ALTR) or pseudotumor formation is commonly associated with metal-on-metal bearings. Elevated serum cobalt and chromium ion levels indicate significant bearing wear or trunnionosis.

Question 43

When evaluating an AP pelvis radiograph for femoroacetabular impingement, which of the following findings is most specific for focal anterior acetabular overcoverage (pincer impingement)?

Explanation

The crossover sign on an AP pelvis radiograph indicates cranial acetabular retroversion, leading to focal anterior overcoverage typical of pincer impingement. An alpha angle >55 degrees indicates cam impingement.

Question 44

A 72-year-old community-dwelling male presents with groin pain 8 months after closed reduction and percutaneous pinning of a Garden II femoral neck fracture. Radiographs demonstrate nonunion with backing out of the screws and 2 cm of femoral neck shortening. What is the most appropriate management?

Explanation

In an active elderly patient with a femoral neck fracture nonunion and healthy acetabular cartilage, total hip arthroplasty provides reliable pain relief and functional restoration. Arthroplasty is preferred over osteotomy in patients over 65 due to higher failure rates of joint preservation.

Question 45

A 75-year-old female sustains a periprosthetic femur fracture 5 years after a cementless THA. Radiographs show a spiral fracture around the stem extending just distal to its tip. The femoral stem is grossly loose. There is good distal bone stock. Which of the following is the best treatment?

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose stem, adequate bone stock). The gold standard treatment is revision arthroplasty utilizing a diaphyseal engaging stem that bypasses the most distal fracture line by at least two cortical diameters.

Question 46

During surgical dislocation of the hip for treatment of FAI and a labral tear, the trochanteric flip osteotomy is performed. To preserve the blood supply to the femoral head, the osteotomy must stay superficial to which of the following structures?

Explanation

A trochanteric flip osteotomy leaves the external rotators intact to protect the medial femoral circumflex artery (MFCA). The osteotomy must be kept superficial to the quadratus femoris muscle to avoid injuring the ascending branch of the MFCA.

Question 47

Which of the following arteries provides the primary blood supply to the femoral head in an adult, making it highly vulnerable to injury in displaced femoral neck fractures?

Explanation

The lateral epiphyseal artery, a terminal branch of the medial femoral circumflex artery (MFCA), supplies the majority of the adult femoral head. It is frequently disrupted in displaced femoral neck fractures, leading to osteonecrosis.

Question 48

Following a right total hip arthroplasty, a patient complains of a prominent right-sided limp. Clinical exam shows the right leg is 2 cm longer than the left, and the shuck test demonstrates excessive soft tissue tension. How does increased femoral offset during THA affect hip biomechanics?

Explanation

Increasing femoral offset increases the lever arm of the abductor muscles. This improves abductor tension and efficiency, which subsequently decreases the overall joint reactive force across the hip joint.

Question 49

In an otherwise well-functioning cementless THA with a conventional ultra-high-molecular-weight polyethylene (UHMWPE) liner, osteolysis is typically initiated by particles of what specific size?

Explanation

Polyethylene wear particles in the submicron range, specifically between 0.1 and 1.0 micrometers, are most efficiently phagocytosed by macrophages. This initiates the inflammatory cascade that leads to osteolysis.

Question 50

A 28-year-old athlete undergoes evaluation for hip pain. The alpha angle is measured on a Dunn lateral view. What anatomical landmarks define the alpha angle?

Explanation

The alpha angle is measured between the axis of the femoral neck and a line connecting the center of the femoral head to the point where the anterior femoral head-neck junction extends beyond the margin of a best-fit circle. An angle >55 degrees indicates cam morphology.

Question 51

A 78-year-old female with severe Alzheimer's dementia sustains a displaced femoral neck fracture. She was a limited household ambulator prior to the injury. Which of the following surgical options is associated with the lowest risk of dislocation in this specific patient?

Explanation

In severe dementia patients who are low-demand ambulators, hemiarthroplasty is preferred over THA due to lower dislocation rates. The anterolateral approach further reduces the dislocation risk compared to the posterior approach.

Question 52

A 62-year-old male with a metal-on-polyethylene THA presents with painful swelling in the thigh 6 years postoperatively. Aspirate is negative for infection, but serum cobalt levels are significantly elevated. Which of the following is the most likely source of the metal debris?

Explanation

Elevated cobalt levels in a metal-on-polyethylene total hip arthroplasty most strongly point to mechanically assisted crevice corrosion (trunnionosis). This occurs at the modular head-neck taper junction.

Question 53

A 35-year-old female presents with chronic deep buttock pain. MRI shows narrowing of the space between the ischial tuberosity and the lesser trochanter, with edema in a specific muscle belly. Which muscle is most commonly compressed and pathognomonic for this condition?

Explanation

Ischiofemoral impingement occurs due to a narrowed space between the ischial tuberosity and the lesser trochanter. This leads to compression, edema, or atrophy of the quadratus femoris muscle.

Question 54

Which of the following best describes a Garden Type II femoral neck fracture?

Explanation

The Garden classification for femoral neck fractures categorizes Type II as a complete fracture across the femoral neck without any displacement.

Question 55

Following a difficult THA for developmental dysplasia of the hip, the patient develops a foot drop and is unable to actively extend the toes or dorsiflex the ankle. Sensation is intact on the plantar aspect of the foot. Which division of the sciatic nerve is most commonly injured during THA?

Explanation

The peroneal (fibular) division of the sciatic nerve is more lateral and anatomically tethered at the fibular head. It possesses less protective connective tissue than the tibial division, making it highly susceptible to stretch injuries during limb lengthening in THA.

Question 56

A 40-year-old male with symptomatic FAI and a labral tear undergoes hip arthroscopy with femoroplasty, acetabuloplasty, and labral repair. Which of the following preoperative factors is the strongest predictor of failure and eventual conversion to THA?

Explanation

Pre-existing osteoarthritis (Tönnis grade 2 or higher) or joint space narrowing (< 2 mm) is the strongest negative prognostic factor for joint preservation surgery in FAI. This frequently leads to early conversion to THA.

Question 57

When utilizing three parallel cancellous lag screws for fixation of a nondisplaced femoral neck fracture, where should the inferior (calcar) screw be positioned to provide the most optimal biomechanical construct?

Explanation

For maximum stability, an inverted triangle configuration is commonly used. The inferior screw must be positioned along the dense bone of the calcar (inferior cortex) to provide cortical support and resist inferior displacement forces.

Question 58

A 28-year-old male athlete presents with groin pain exacerbated by hip flexion and internal rotation. Radiographs reveal an alpha angle of 70 degrees. Which of the following is the most likely primary mechanism of cartilage damage in this condition?

Explanation

Cam impingement (alpha angle > 55 degrees) involves a non-spherical femoral head engaging the acetabulum during flexion. The resulting shear forces characteristically cause outside-in delamination of the anterosuperior acetabular cartilage and subsequent labral separation.

Question 59

A 28-year-old male sustains a vertically oriented, Pauwels type III femoral neck fracture after a high-energy motor vehicle collision. Which of the following internal fixation constructs provides the highest biomechanical stability for this specific fracture pattern?

Explanation

A sliding hip screw combined with a derotation screw provides superior biomechanical stability compared to multiple parallel cancellous screws for vertically oriented (Pauwels type III) femoral neck fractures, as it better resists vertical shear forces.

Question 60

In an effort to minimize the risk of dislocation following a total hip arthroplasty, a surgeon aims to increase the 'jump distance.' Which of the following modifications will most effectively accomplish this goal?

Explanation

Jump distance is the distance the femoral head must translate to dislocate from the acetabulum. Increasing the diameter of the femoral head directly increases the jump distance, thereby enhancing the stability of the total hip arthroplasty.

Question 61

A 32-year-old female presents with chronic anterior groin pain exacerbated by hip flexion and internal rotation. An anteroposterior (AP) radiograph of the pelvis demonstrates a 'crossover sign.' This radiographic finding is most indicative of which of the following?

Explanation

The crossover sign occurs when the anterior wall of the acetabulum projects laterally to the posterior wall on an AP pelvis radiograph. It is a classic radiographic indicator of acetabular retroversion, a primary cause of pincer-type femoroacetabular impingement.

Question 62

A 75-year-old patient sustains a periprosthetic femur fracture around a total hip arthroplasty placed 10 years ago. Radiographs show a fracture at the tip of the stem. The stem is clinically and radiographically loose, but the proximal femoral bone stock remains adequate. What is the most appropriate surgical management?

Explanation

This describes a Vancouver B2 periprosthetic fracture (fracture around a loose stem with good bone stock). The gold standard of treatment is revision to a long, diaphyseal-fitting (often fluted and tapered) uncemented stem to bypass the fracture and achieve stable distal fixation.

Question 63

When evaluating a patient for suspected cam-type femoroacetabular impingement (FAI), measurement of the alpha angle is most accurately assessed using which of the following radiographic views?

Explanation

The alpha angle is used to quantify the loss of femoral head sphericity seen in cam-type FAI. It is best evaluated on an axial or modified axial view of the proximal femur, such as the Dunn view or a cross-table lateral radiograph.

Question 64

A 68-year-old male presents with new-onset groin pain and a palpable mass 8 years after a metal-on-polyethylene total hip arthroplasty. Serum cobalt levels are significantly elevated, while chromium levels are normal. Inflammatory markers are within normal limits. What is the most likely diagnosis?

Explanation

Elevated serum cobalt levels with normal chromium in the setting of a metal-on-polyethylene bearing strongly suggests mechanically assisted crevice corrosion at the modular head-neck junction (trunnionosis), leading to an adverse local tissue reaction (ALTR).

Question 65

An active, independent 78-year-old community ambulator sustains a displaced femoral neck fracture. Compared to treatment with bipolar hemiarthroplasty, treatment with total hip arthroplasty (THA) is associated with which of the following?

Explanation

In active, independent elderly patients with displaced femoral neck fractures, THA provides superior long-term functional outcomes and lower reoperation rates compared to hemiarthroplasty, although THA carries a slightly higher initial risk of dislocation.

Question 66

During a safe surgical dislocation of the hip (Ganz approach) for the treatment of femoroacetabular impingement, a trochanteric flip osteotomy is performed. This technique is specifically designed to protect which critical vascular structure?

Explanation

The safe surgical dislocation of the hip utilizes a trochanteric flip osteotomy leaving the external rotators intact to the proximal femur. This protects the deep branch of the medial femoral circumflex artery (MFCA), preventing avascular necrosis of the femoral head.

Question 67

A 45-year-old active male is undergoing total hip arthroplasty. Which of the following bearing surface combinations is associated with the lowest volumetric wear rate?

Explanation

Ceramic-on-ceramic bearing surfaces exhibit the lowest volumetric wear rates in total hip arthroplasty. However, they carry unique risks, including component fracture and squeaking.

Question 68

A 35-year-old male presents with a nonunion of a femoral neck fracture 8 months after initial fixation with parallel cancellous screws. MRI confirms the femoral head remains viable with no evidence of avascular necrosis. What is the most appropriate surgical treatment?

Explanation

In a young patient with a femoral neck nonunion and a viable femoral head, a valgus-producing intertrochanteric osteotomy alters the mechanical axis, converting shear forces at the fracture site into compressive forces, thereby promoting fracture healing.

Question 69

To minimize the risk of dislocation after total hip arthroplasty, the acetabular component should ideally be placed within the 'Lewinnek safe zone'. Which of the following represents these correct target angles?

Explanation

The classic Lewinnek safe zone for acetabular cup placement dictates an inclination (abduction) of 40 ± 10 degrees and an anteversion of 15 ± 10 degrees to reduce the risk of postoperative dislocation.

Question 70

In the pathophysiology of cam-type femoroacetabular impingement, the aspherical portion of the femoral head engages the acetabulum during hip flexion and internal rotation. Where does the resulting chondral delamination characteristically occur?

Explanation

Cam impingement causes shear stress as the non-spherical femoral head enters the joint during flexion, leading to classic inside-out chondral delamination and labral tears primarily in the anterosuperior quadrant of the acetabulum.

Question 71

A 60-year-old female complains of persistent groin pain 1 year after an uncomplicated total hip arthroplasty. The pain is particularly sharp when she lifts her leg to get out of a car or performs an active straight leg raise. Radiographs reveal a prominent anterior edge of the acetabular component. What is the most likely etiology of her pain?

Explanation

Groin pain provoked by active hip flexion (e.g., straight leg raise) following THA, especially in the presence of an anteriorly prominent or retroverted acetabular cup, is highly characteristic of iliopsoas tendon impingement.

Question 72

Following a total hip arthroplasty via a posterior approach, a patient is noted to have a foot drop and inability to extend the great toe. The peroneal division of the sciatic nerve is injured. Which anatomic feature explains why the peroneal division is more susceptible to injury than the tibial division?

Explanation

The peroneal division of the sciatic nerve is more vulnerable to stretch injuries during THA because it is tethered distally at the fibular head, lies more laterally (closer to the retractors), and has larger fascicles with less protective connective tissue than the tibial division.

Question 73

When evaluating a patient with a femoral neck fracture, which of the following is the most significant prognostic factor for the subsequent development of avascular necrosis of the femoral head after internal fixation?

Explanation

The initial degree of fracture displacement (e.g., Garden classification) is the single most important predictor of avascular necrosis after a femoral neck fracture, as greater displacement correlates directly with more severe disruption of the retinacular blood supply.

Question 74

A 25-year-old male sustains a vertically oriented femoral neck fracture (Pauwels type III). What fixation construct provides the greatest biomechanical stability for this specific pattern?

Explanation

A sliding hip screw with a derotational screw provides superior biomechanical stability for highly unstable, vertically oriented (Pauwels III) femoral neck fractures compared to parallel cannulated screws by resisting shear forces.

Question 75

A patient presents with recurrent anterior dislocations following a total hip arthroplasty performed via a posterior approach. Radiographs show the acetabular component has 55 degrees of inclination and 45 degrees of anteversion. What is the primary cause of dislocation in this patient?

Explanation

Excessive acetabular anteversion (normal target is 15-20 degrees) predisposes the hip to anterior dislocation. This typically occurs when the hip is placed in extension and external rotation.

Question 76

During hip arthroscopy for femoroacetabular impingement, a classic Cam lesion is identified. Where is the most common location of the associated chondral injury?

Explanation

Cam impingement typically causes shear forces on the anterosuperior acetabular cartilage. This frequently leads to chondral delamination and labral detachment in this quadrant.

Question 77

A 65-year-old male with a metal-on-polyethylene total hip arthroplasty presents with groin pain 5 years postoperatively. Aspiration yields cloudy fluid with negative cultures but elevated serum cobalt levels. MRI demonstrates a large cystic pseudotumor. What is the most likely diagnosis?

Explanation

Trunnionosis is mechanically assisted crevice corrosion at the modular head-neck junction. It can cause an adverse local tissue reaction (ALTR) or pseudotumor even in metal-on-polyethylene bearings, evidenced by elevated serum metal ions.

Question 78

In the treatment of displaced femoral neck fractures in young adults, which of the following is the most reliable predictor of developing avascular necrosis (AVN)?

Explanation

The degree of initial fracture displacement is the most significant and reliable predictor of AVN and nonunion in young patients with femoral neck fractures. The role of timing and capsulotomy remains controversial in recent literature.

Question 79

A 45-year-old female undergoes total hip arthroplasty with a ceramic-on-ceramic bearing. Three years later, she complains of a reproducible squeaking noise during gait. Which of the following factors is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is most strongly associated with edge loading. This is typically due to acetabular component malposition, particularly excessive inclination or anteversion, or impingement.

Question 80

Which of the following radiographic findings on an AP pelvis is most characteristic of Pincer-type femoroacetabular impingement caused by acetabular retroversion?

Explanation

The crossover sign on an AP pelvis radiograph indicates cranial acetabular retroversion, a common cause of Pincer morphology. It occurs when the anterior rim line crosses the posterior rim line.

Question 81

A 70-year-old female sustains a basicervical femoral neck fracture. Which of the following statements regarding this fracture pattern is true?

Explanation

Basicervical fractures are at the extracapsular base of the neck and are biomechanically unstable. They behave like intertrochanteric fractures and typically require a sliding hip screw or cephalomedullary nail rather than multiple parallel screws.

Question 82

A 75-year-old female falls and sustains a periprosthetic femur fracture around a cemented THA stem. Radiographs show a fracture around the stem tip, a loose femoral component, and excellent distal bone stock (Vancouver B2). What is the optimal surgical management?

Explanation

A Vancouver B2 fracture is characterized by a fracture around the stem with a loose stem but adequate bone stock. The standard of care is revision of the femoral component to a diaphyseal bypassing, distally fixing uncemented stem.

Question 83

When measuring the alpha angle to evaluate for Cam morphology on a Dunn lateral radiograph or MRI, an angle greater than what threshold is traditionally considered abnormal?

Explanation

An alpha angle greater than 55 degrees is widely considered the threshold for identifying a symptomatic Cam deformity. It measures the extent to which the femoral head deviates from perfectly spherical.

Question 84

A patient reports persistent groin pain and catching when actively rising from a seated position following an uncemented THA. A diagnostic injection of lidocaine into the iliopsoas bursa provides complete relief. What radiographic finding is most likely present?

Explanation

Iliopsoas impingement is typically caused by a prominent anterior edge of the acetabular component catching the tendon. It classically presents with groin pain upon active hip flexion and is diagnosed via image-guided injection.

Question 85

Based on the HEALTH trial and recent evidence, which of the following is true regarding THA compared to hemiarthroplasty for displaced femoral neck fractures in active older adults?

Explanation

THA for displaced femoral neck fractures yields a higher risk of dislocation compared to hemiarthroplasty. However, overall mortality is similar, and THA may offer slight functional benefits in very active patients.

Question 86

A patient presents 6 weeks after a primary THA with a draining sinus tract communicating directly with the joint. According to the 2018 International Consensus Meeting (ICM) criteria, what is the next best step for diagnosing infection?

Explanation

A sinus tract communicating with the joint is a major criterion for periprosthetic joint infection (PJI). It definitively establishes the diagnosis, meaning no further diagnostic testing is required to confirm PJI before planning surgical intervention.

Question 87

What is the most common nerve-related complication following hip arthroscopy due to portal placement and limb traction?

Explanation

Lateral femoral cutaneous nerve (LFCN) neurapraxia is the most common neurologic complication of hip arthroscopy. It is directly related to the placement of the anterior portal and limb traction.

Question 88

A 35-year-old female presents with persistent groin pain 8 months after internal fixation of a femoral neck fracture. Radiographs reveal varus collapse with a visible fracture line. MRI demonstrates a viable femoral head. What is the most appropriate management?

Explanation

In a young patient with a femoral neck nonunion and a viable femoral head, a valgus intertrochanteric osteotomy is indicated. This procedure converts detrimental shear forces into compressive forces to promote fracture healing.

Question 89

Which historical sterilization method for ultra-high-molecular-weight polyethylene (UHMWPE) is most associated with subsequent severe oxidation, delamination, and rapid wear in THA?

Explanation

Gamma irradiation in air produces free radicals that react with ambient oxygen over time. This leads to severe oxidation, chain scission, and catastrophic delamination and wear of the polyethylene.

Question 90

A 40-year-old female runner complains of deep gluteal pain radiating down the posterior thigh. MRI reveals narrowing of the space between the lesser trochanter and the ischium, with edema within the intervening muscle. What is the diagnosis?

Explanation

Ischiofemoral impingement occurs due to a narrowed space between the lesser trochanter and the ischial tuberosity. It classically presents with deep posterior pain and MRI findings of quadratus femoris muscle edema.

Question 91

Histologic evaluation of periprosthetic tissue from a failed metal-on-metal THA demonstrates an adverse local tissue reaction (ALTR). Which cellular finding is characteristic of an Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion (ALVAL)?

Explanation

ALVAL is a type IV delayed hypersensitivity reaction to metal ions. Histologically, it is classically characterized by a robust perivascular lymphocytic infiltrate and varying degrees of tissue necrosis.

Question 92

A patient presents with an intracapsular femoral neck fracture that extends distally to the level of the lesser trochanter. If internal fixation is planned, what is the most biomechanically sound implant choice?

Explanation

Femoral neck fractures with basicervical or subtrochanteric extension are highly unstable. A cephalomedullary nail or a long sliding hip screw is required to bypass the subtrochanteric region and prevent catastrophic hardware failure.

Question 93

A patient complains of an apparent leg length discrepancy immediately following a primary THA. Examination reveals the operative leg appears longer, but true leg length measurement (ASIS to medial malleolus) is equal bilaterally. What is the most likely cause?

Explanation

An apparent leg length discrepancy with equal true leg lengths is often caused by pelvic obliquity. This can result from preexisting spinal deformity, adductor contracture, or abductor weakness, and often resolves with targeted physical therapy.

Question 94

A 68-year-old woman presents with recurrent posterior dislocations following a primary total hip arthroplasty. Evaluation reveals the acetabular component is placed in 5 degrees of retroversion and 40 degrees of inclination. During which of the following activities is she at the highest risk for dislocation?

Explanation

Posterior dislocation of a THA is most commonly associated with hip flexion, internal rotation, and adduction. A retroverted acetabular component exacerbates this risk by failing to provide adequate posterior head coverage during these specific motions.

Question 95

A 32-year-old male sustains a displaced, vertically oriented (Pauwels type III) femoral neck fracture in a motor vehicle collision. Which of the following fixation constructs provides the most biomechanically stable fixation for this specific fracture pattern?

Explanation

Pauwels type III femoral neck fractures are highly unstable due to high vertical shear forces across the fracture site. A sliding hip screw (a fixed-angle device) combined with an anti-rotation screw provides superior biomechanical stability against these shear stresses compared to multiple cancellous lag screws.

Question 96

A 24-year-old male collegiate hockey player presents with insidious onset of deep groin pain, exacerbated by deep squatting and prolonged sitting. Radiographs demonstrate a prominent osseous bump at the anterolateral femoral head-neck junction. Which of the following physical examination maneuvers is most likely to be positive in this patient?

Explanation

The patient's presentation and radiographs are classic for Cam-type femoroacetabular impingement (FAI). The FADIR test is highly sensitive for assessing anterior impingement and labral pathology, consistently reproducing groin pain in these patients.

Question 97

A 55-year-old man who underwent a metal-on-polyethylene total hip arthroplasty 5 years ago presents with new-onset groin pain and a palpable fluid collection. Radiographs show well-fixed components with a large femoral head and a modular neck. Laboratory testing reveals elevated serum cobalt and normal chromium levels. What is the most likely diagnosis?

Explanation

Trunnionosis is caused by mechanically assisted crevice corrosion at the modular head-neck or neck-stem taper junction. It is characterized by adverse local tissue reactions (pseudotumors) and isolated elevated serum cobalt levels out of proportion to chromium, even in metal-on-polyethylene bearings.

Question 98

A 75-year-old cognitively intact, highly active community ambulator sustains a displaced femoral neck fracture. Compared to a cemented bipolar hemiarthroplasty, surgical treatment with a total hip arthroplasty (THA) is most likely associated with which of the following?

Explanation

In active, cognitively intact older adults with displaced femoral neck fractures, THA provides better long-term functional outcomes (e.g., Harris Hip Scores) and lower reoperation rates compared to hemiarthroplasty. However, THA does carry a higher risk of dislocation, longer operative time, and greater blood loss.

Question 99

An anteroposterior (AP) pelvis radiograph is performed to evaluate a 30-year-old female with chronic groin pain. The radiograph demonstrates a "crossover sign" and an "ischial spine sign". Which of the following underlying pathomorphologies is most strongly associated with these radiographic findings?

Explanation

The crossover sign (where the anterior acetabular wall crosses the posterior wall line) and the ischial spine sign (projection of the ischial spine into the pelvic basin on an AP view) indicate focal acetabular retroversion. This morphology leads to anterior overcoverage and is a primary cause of Pincer-type femoroacetabular impingement.

Question 100

Following a primary total hip arthroplasty performed via a posterior approach, the patient is noted in the recovery room to have an inability to dorsiflex the great toe or evert the foot. Sensation is decreased over the anterolateral leg and the dorsum of the foot. Which specific neural structure is most likely injured?

Explanation

The common peroneal division of the sciatic nerve is uniquely susceptible to stretch injury during THA, particularly when the limb is lengthened or retractors are placed posteriorly. It provides motor innervation to the ankle dorsiflexors and everters, and sensory innervation to the anterolateral leg and dorsum of the foot.

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

Orthopedic Hip MCQs (Set 4): Femoral Neck Fractures, THA Complications & FAI | AAOS & ABOS Review

Key Takeaway

Orthopedic Hip MCQs (Set 4): Femoral Neck Fractures, THA Complications & FAI | AAOS & ABOS Review

Chapter Index