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Total Hip Arthroplasty (THA) MCQs

Practice Set 8 of 36

This practice set contains high-yield board review questions covering key concepts in Total Hip Arthroplasty (THA). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 141

Topic: Total Hip Arthroplasty (THA)
A 44-year-old woman has bilateral knee pain, and history reveals bilateral hip replacements. Radiographs are seen in Figure 28a, and histopathologic specimens from the total hip replacement are shown in Figures 28b and 28c. Laboratory studies reveal anemia. What is the most likely diagnosis?
. Osteoarthritis
. Rheumatoid arthritis
. Pigmented villonodular synovitis
. Charcot arthropathy
. Paget’s disease

Correct Answer & Explanation

. Rheumatoid arthritis

Explanation

DISCUSSION: Rheumatoid arthritis is an inflammatory arthritis that usually involves multiple joints. Radiologic findings of periarticular erosion, osteopenia, and minimal osteophyte formation favor rheumatoid arthritis over osteoarthritis. Pigmented villonodular synovitis and Charcot arthropathy are more often considered monoarticular diseases. There are no radiographic findings of Paget’s disease. REFERENCE: Dutkowsky J: Miscellaneous non traumatic disorders, in Crenshaw A (ed): Campbell’s Operative Orthopaedics. St Louis, MO, Mosby, 1992, pp 2007-2012.

Question 142

Topic: Total Hip Arthroplasty (THA)
Figure 1 shows the radiograph obtained from a 67-year-old man recently diagnosed with osteoarthritis, 8 years after receiving a left metal-on-metal total hip arthroplasty (THA). The acetabular component has a modular cobalt alloy acetabular liner. The patient states that he did very well postoperatively, but for the last 6 months has noted worsening pain and swelling in his left hip. Serum metal ion testing reveals a chromium level of 12.4 ng/mL, compared with a normal level of less than 0.3 ng/mL, and a cobalt level of 11.8 ng/mL, compared with a normal level less than 0.7 ng/mL. An MRI with metal artefact reduction sequence (MARS) was performed and is shown in Figure 2. What is the most appropriate management at this time?
. Annual monitoring of serum metal ion levels
. Repeated MRI with MARS in 6 months
. Conversion of the THA to a cobalt alloy femoral head and polyethylene bearing
. Conversion of the THA to a ceramic femoral head with an inner titanium sleeve and polyethylene bearing

Correct Answer & Explanation

. Conversion of the THA to a ceramic femoral head with an inner titanium sleeve and polyethylene bearing

Explanation

DISCUSSION: Metal-on-metal THA was initially introduced in the 1990s, with the proposed advantages of decreased wear and improved stability. However, catastrophic adverse local tissue reactions associated with their use has raised numerous concerns. The work-up of a patient with a prior metal-on-metal total hip arthroplasty involves a thorough history and physical examination; blood analysis, including the erythrocyte sedimentation rate, C-reactive protein, and metal ion levels; and secondary imaging, including ultrasonography, CT, and MRI. In a patient with clinical symptoms, elevated metal ion levels, and a large fluid collection seen on MRI, the most appropriate treatment would be removal of the metal-on-metal bearing. Given the presence of an adverse reaction involving cobalt and chromium, a revision ceramic head may be most appropriate to avoid the potential of trunnion-associated corrosion.

Question 143

Topic: Total Hip Arthroplasty (THA)

A 71-year-old man has worsening left hip pain and is indicated for a left total hip arthroplasty (THA). Figure 1 shows a preoperative plan for the patient. The patient is scheduled for a left THA using a direct anterior approach with the pictured implants. If this plan is followed as pictured, what is the likely outcome for this patient? Figure could not be loaded

. Successful THA with significant shortening of the operative limb
. Compromised THA with a high likelihood of persistent trochanteric bursitis
. Successful THA with significant lengthening of the operative limb
. Compromised THA with a Trendelenburg gait and hip instabilityThe focus should be on the pictured plan. This shows a medialized cup and a stem that has insufficient offset (distance between the center of rotation and a line down the center of the femoral shaft) to recreate the patient’s anatomy. The cup sets the hip center of rotation (dot in the middle of the cup), and the femoral head reduces to this point. In this patient, inadequate offset could lead to a decrease in abductor efficiency and a Trendelenburg gait and even worse dislocation due to component impingement and/or muscular insufficiency. Compromised THA with a high likelihood of persistent trochanteric bursitis would be accurate if too much offset was restored for the patient. Regarding limb lengths, it appears the height of the implant is sufficient and as it stands would likely not change the leg lengths much at all. The concepts of limb length and offset restoration are critical to performing a successful THA and limiting adverse events and poor outcomes from an acquired limb length discrepancy, limb instability or persistent trochanteric bursitis.

Correct Answer & Explanation

. Successful THA with significant shortening of the operative limb

Explanation

Figure 1 is the radiograph of a 73-year-old woman who had a right hip arthroplasty one year prior. Her BMI is 48. Postoperative radiographs at 6 weeks showed early stem subsidence of 4 mm compared with intraoperative radiographs. The current radiographic findings likely resulted from theA. spinal fusion.B. BMI and implant size.C. mismatch between the metaphysis and diaphysis.D. modular neck prosthesis.

Question 144

Topic: Total Hip Arthroplasty (THA)
  • The concept of an “effective joint space” surrounding a prosthetic hip replacement refers to the
. Extent of bone penetrated by reaming, prosthetic components, or acrylic cement
. Periprosthetic regions that are accessible to joint fluid and particulate wear debris
. Enveloping pseudocapsular scar tissue that develops around a prosthetic hip following surgical capsulectomy
. Soft tissue and bone that are potentially contaminated with bacteria in the setting of a prosthetic joint infection
. Potential intrapelvic joint space communication created by acetabular fixation screws or intrapelvic extruded acrylic cement

Correct Answer & Explanation

. Extent of bone penetrated by reaming, prosthetic components, or acrylic cement

Explanation

The term “effective joint space” was initiated in the article that this question was referenced from. It is defined as all the regions that are accessible to joint fluid. The significance of the effective joint space is that patterns of joint fluid flow (preferential flow) will determine the concentration and pattern of particulate wear debris. Where there is wear debris there is the potential for lytic and linear bone loss secondary to macrophage concentrations.

Question 145

Topic: Total Hip Arthroplasty (THA)
A 63-year-old woman had a primary total hip arthroplasty 7 years ago that included a proximally coated titanium stem, a cobalt alloy femoral head, a titanium hemispherical acetabular component, and a polyethylene liner. She did well for 4 years but has now had two dislocations and reports pain and weakness around the left hip. She denies any fevers, chills, or constitutional symptoms. On examination, the patient walks well without any signs of an antalgic or Trendelenburg gait. Her abductor mechanism demonstrates good strength. Her erythrocyte sedimentation rate and C-reactive protein level are normal. On radiographs, all components appear well fixed and in good alignment. What is the most appropriate treatment at this time?
. Physical therapy to improve hip stability
. Use of an abduction brace to limit the patient’s range of motion
. Conversion to a constrained acetabular liner
. Cobalt and chromium serum metal ion level testing

Correct Answer & Explanation

. Cobalt and chromium serum metal ion level testing

Explanation

Trunnionosis is a recently recognized complication following total hip arthroplasty and can occur when a cobalt alloy femoral head is used on a titanium alloy or cobalt alloy femoral stem. Patients often present with pain or swelling around the hip but at times can present with instability. In a patient with a cobalt alloy femoral head who presents with instability, swelling, and weakness around the hip, the potential for trunnionosis and an adverse local tissue reaction should be considered.

Question 146

Topic: Total Hip Arthroplasty (THA)
A 70-year-old man undergoes removal of an infected total hip arthroplasty (THA) and insertion of an articulating antibiotic-loaded spacer to treat a deep periprosthetic hip infection. While in a nursing home receiving intravenous antibiotics 3 weeks after surgery, the patient trips and falls. Examination reveals swelling in the mid and distal thigh, intact skin and neurovascular structures, and severe pain with knee or hip movement. Radiographs of the femur are shown in Figures 1 through 4. What is the most appropriate treatment for the fracture below the implant?
. Balanced traction to address concern for persistent infection with reoperation
. Open reduction and internal fixation of the fracture with a lateral plate and screws
. Removal of the articulating spacer and revision to a longer-stem antibiotic-loaded articulating spacer
. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement

Correct Answer & Explanation

. Open reduction and internal fixation of the fracture with a lateral plate and screws

Explanation

DISCUSSION: This patient has a type C periprosthetic femoral fracture. The articulating spacer is not involved in the fracture, which is well distal to the implant. The most appropriate treatment is open reduction and internal fixation of the fracture. Traction is not appropriate for this fracture because the injury can be treated surgically despite the history of previous hip infection. Traction would also be needed for at least 5 weeks and would delay the surgical treatment of the periprosthetic fracture until the time of second-stage revision THA. The fracture is fairly distal, and revision to a longer antibiotic-loaded implant or uncemented stem is not suitable for this fracture pattern, because it extends well past the isthmus. A femoral stem in the distal fragment would provide little stability for the fracture. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement is not appropriate, because it would be premature to reimplant the man's hip while he is still receiving treatment for a deep hip infection.

Question 147

Topic: Total Hip Arthroplasty (THA)
Which of the following is considered an important factor in improved cemented femoral stem survivorship?
. Precoated stem with methylmethacrylate
. Varus stem position
. 2 to 3 mm of circumferential cement mantle
. Dorr C or “stovepipe” femoral anatomy
. Sharp angled corners on the femoral stem

Correct Answer & Explanation

. 2 to 3 mm of circumferential cement mantle

Explanation

Cement technique, relative stem to canal size and position, stem design, surgical technique, and femoral anatomy are important factors in cemented stem survivorship. Varus stem position, a wide diaphyseal to metaphyseal ratio (stovepipe femur), thin cement mantles (1 mm or less), and nonrounded femoral stem designs are negative prognostic factors for stem survivorship. A 2 to 3 mm circumferential cement mantle is considered optimal for survivorship.

Question 148

Topic: Total Hip Arthroplasty (THA)
During a revision total hip arthroplasty, the surgeon encounters a severe acetabular defect. Radiographs and intraoperative findings reveal greater than 3 cm of superior component migration, destruction of the teardrop, and component medialization beyond Kohler's line. The superior hemipelvis remains mechanically in continuity with the inferior hemipelvis. According to the Paprosky classification, what is the defect grade and the most appropriate reconstructive option?
. Paprosky IIIA; hemispherical jumbo cup with multiple screws
. Paprosky IIIB; custom triflange or cup-cage construct
. Paprosky IIIC; massive structural allograft with a cemented cup
. Paprosky IVA; pelvic discontinuity requiring distraction and plating
. Paprosky IIC; highly porous titanium cup with augment

Correct Answer & Explanation

. Paprosky IIIB; custom triflange or cup-cage construct

Explanation

A Paprosky IIIB defect is characterized by severe bone loss with >3 cm of superior migration, component medialization past Kohler's line, and destruction of the teardrop, indicating non-supportive superior and medial bone (<30% host bone contact). Management typically requires a custom triflange component, a cup-cage construct, or massive structural allografts with a support ring to achieve stability, as standard hemispherical cups will not achieve adequate fixation.

Question 149

Topic: Total Hip Arthroplasty (THA)

A surgeon is considering using a dual mobility articulation for an 80-year-old patient undergoing revision THA for recurrent instability due to severe abductor deficiency. Which of the following best describes the biomechanical mechanism by which a dual mobility implant increases stability?

. It decreases the head-to-neck ratio, allowing increased range of motion before impingement
. It increases the 'jumping distance' through the use of a large effective head size consisting of a mobile polyethylene liner
. It constrains the femoral head within the liner using a locking ring mechanism
. It functions by lateralizing the center of rotation to tension the remaining soft tissues
. It exclusively relies on a bipolar design where motion occurs only at the inner interface

Correct Answer & Explanation

. It decreases the head-to-neck ratio, allowing increased range of motion before impingement

Explanation

Dual mobility implants feature a smaller inner metallic or ceramic head that articulates within a larger, mobile polyethylene sphere, which in turn articulates within a metal acetabular shell. The primary mechanism of increased stability is the large effective head size of the outer polyethylene sphere, which significantly increases the 'jumping distance' (the distance the head must translate to dislocate) and maximizes the impingement-free range of motion.

Question 150

Topic: Total Hip Arthroplasty (THA)

During the removal of a well-fixed, fully porous-coated stem in a revision THA, an extended trochanteric osteotomy (ETO) is performed. Which muscle's attachment must be meticulously preserved on the osteotomized fragment to ensure adequate blood supply and subsequent osteotomy healing?

. Gluteus maximus
. Vastus lateralis
. Iliopsoas
. Piriformis
. Rectus femoris

Correct Answer & Explanation

. Gluteus maximus

Explanation

An extended trochanteric osteotomy (ETO) involves elevating the greater trochanter and the lateral diaphyseal cortex. The blood supply to this fragment, which is crucial for union, is predominantly provided by the vastus lateralis (and its muscular branches). Preserving the attachment of the vastus lateralis (as well as the gluteus medius/minimus proximally) ensures the fragment remains vascularized and stabilizes it against proximal migration.

Question 151

Topic: Total Hip Arthroplasty (THA)

A surgeon is performing an extended trochanteric osteotomy (ETO) via a posterior approach to facilitate femoral component extraction during a revision THA. To maintain the blood supply to the osteotomized fragment and prevent superior migration, which muscle attachments must be preserved?

. Gluteus maximus and vastus intermedius
. Gluteus medius and vastus lateralis
. Gluteus minimus and rectus femoris
. Piriformis and vastus medialis
. Iliopsoas and tensor fasciae latae

Correct Answer & Explanation

. Gluteus maximus and vastus intermedius

Explanation

An extended trochanteric osteotomy (ETO) involves elevating the lateral third of the proximal femur. The gluteus medius and vastus lateralis must be left attached to the fragment. They provide an uninterrupted vascular supply to the bone flap and act as an antagonist muscle pair, maintaining the fragment's longitudinal position during healing.

Question 152

Topic: Total Hip Arthroplasty (THA)
A 68-year-old male requires a revision total hip arthroplasty for a loose femoral stem. Radiographs demonstrate a Paprosky Type IIIB femoral defect. Which of the following best defines a Type IIIB defect and indicates the most appropriate femoral implant choice?
. >4 cm of intact diaphyseal bone at the isthmus; use a fully porous-coated cylindrical stem.
. <4 cm of intact diaphyseal bone at the isthmus; use a modular fluted tapered stem.
. Complete loss of the femoral diaphysis to the supracondylar region; use a total femoral replacement.
. Intact metaphysis but an isolated greater trochanteric fracture; use a standard primary stem with a claw.
. Extensive metaphyseal bone loss with >4 cm diaphyseal fit available; use an impaction allograft reconstruction.

Correct Answer & Explanation

. <4 cm of intact diaphyseal bone at the isthmus; use a modular fluted tapered stem.

Explanation

In the Paprosky femoral defect classification, a Type IIIA defect has >4 cm of intact diaphyseal bone at the isthmus, allowing for reliable fixation with a fully porous-coated cylindrical stem. A Type IIIB defect has <4 cm of intact diaphysis, which is insufficient for cylindrical scratch fit. The standard of care for IIIB defects is a modular fluted tapered stem, which achieves rotational and axial stability in a shorter segment of distal bone.

Question 153

Topic: Total Hip Arthroplasty (THA)

A 70-year-old male with a history of multiple revision total hip arthroplasties presents with recurrent posterior dislocations. Intraoperative evaluation reveals that both the acetabular and femoral components are well-fixed and optimally aligned. However, the patient has profound and irreparable abductor deficiency. Assuming component modularity permits, what is the most reliable reconstructive option?

. Revision of the acetabular shell to increase anteversion
. Revision to a dual-mobility construct
. Revision to a constrained acetabular liner
. Proximal femoral osteotomy
. Trochanteric advancement

Correct Answer & Explanation

. Revision of the acetabular shell to increase anteversion

Explanation

In the setting of recurrent instability due to severe, unrepairable abductor deficiency with well-positioned and well-fixed components, a constrained acetabular liner is the most appropriate option. While dual-mobility constructs are excellent for instability, they rely on a functional dynamic soft-tissue envelope (abductors) and may still dislocate in profound abductor deficiency.

Question 154

Topic: Total Hip Arthroplasty (THA)

Following insertion of trial components during a primary THA, the hip is stable. However, intraoperative measurement shows the operated leg is 15 mm longer than the contralateral side, and the global offset is 5 mm less than desired. Which of the following component adjustments will most effectively restore equal leg length while simultaneously increasing global offset?

. Use a shorter femoral head with a longer neck modularity
. Use a high-offset femoral stem combined with a shorter neck modularity
. Increase the acetabular cup size to achieve more medialization
. Change to a standard offset stem with a longer neck
. Use a lateralized acetabular liner with a standard femoral head

Correct Answer & Explanation

. Use a shorter femoral head with a longer neck modularity

Explanation

To correct an overly long leg, the neck length must be decreased (e.g., using a shorter modular head). However, this alone would further decrease offset. Changing from a standard stem to a high-offset stem increases offset independently of leg length. Therefore, using a high-offset stem with a shorter modular neck/head corrects both problems: it reduces leg length while maintaining or increasing the offset.

Question 155

Topic: Total Hip Arthroplasty (THA)

When utilizing a polished, collarless, taper-slip cemented femoral stem during a primary THA, which of the following biomechanical principles governs its fundamental design and function?

. It is designed to achieve rigid chemical bonding to the polymethylmethacrylate (PMMA) mantle
. It relies on macro-interlock with the cement mantle to resist subsidence
. It subsides within the cement mantle to increase radial compressive forces (hoop stresses)
. It acts strictly as a composite beam with the cement to transfer stress proximally
. It requires a structural collar to prevent distal migration and excessive hoop stresses

Correct Answer & Explanation

. It is designed to achieve rigid chemical bonding to the polymethylmethacrylate (PMMA) mantle

Explanation

Polished, collarless, taper-slip stems (e.g., Exeter) are designed to subside slightly ('slip') within the cement mantle under axial loading. Because they are tapered, this subsidence wedges the stem into the cement, converting axial loads into radial compressive forces (hoop stresses) that strengthen the construct. They do not bond to the cement, unlike composite-beam stems.

Question 156

Topic: Total Hip Arthroplasty (THA)

During a primary total hip arthroplasty via a posterior approach, the surgeon inadvertently utilizes a femoral component with significantly less offset than the patient's native anatomy, while maintaining equal leg lengths. Which of the following biomechanical consequences is most likely to occur?

. Increased abductor muscle mechanical advantage.
. Decreased joint reactive force across the hip articulation.
. Increased tension on the greater trochanteric musculature.
. Increased joint reactive force and an increased likelihood of impingement.
. Decreased varus bending moment on the femoral stem leading to lower risk of stem loosening.

Correct Answer & Explanation

. Increased joint reactive force and an increased likelihood of impingement.

Explanation

Decreasing the femoral offset brings the femur closer to the pelvis. This shortens the abductor lever arm, decreasing the mechanical advantage of the abductor muscles. To maintain a level pelvis during single-leg stance, the abductors must fire with significantly greater force, which in turn increases the total joint reactive force across the hip. Additionally, the decreased clearance between the femur and pelvis increases the risk of bony or soft tissue impingement, which can precipitate dislocation.

Question 157

Topic: Total Hip Arthroplasty (THA)

A 62-year-old male with a metal-on-polyethylene (MoP) total hip arthroplasty (large cobalt-chromium head on a titanium stem) presents with new-onset hip pain 5 years post-operatively. Workup reveals a cystic mass and normal inflammatory markers. If mechanically assisted crevice corrosion (trunnionosis) is the primary pathology, serum metal ion testing will most likely demonstrate:

. Elevated titanium levels with undetectable cobalt and chromium.
. Markedly elevated chromium levels with normal cobalt.
. Markedly elevated cobalt levels with normal or slightly elevated chromium.
. Equally elevated levels of both cobalt and chromium.
. Undetectable metal ions, as trunnionosis only produces local tissue reactions.

Correct Answer & Explanation

. Markedly elevated cobalt levels with normal or slightly elevated chromium.

Explanation

In metal-on-polyethylene (MoP) THA utilizing a cobalt-chromium (CoCr) head on a titanium (Ti) alloy stem, mechanically assisted crevice corrosion can occur at the head-neck taper (trunnionosis). This specific galvanic and mechanical corrosion process preferentially releases cobalt over chromium. Therefore, serum analysis typically shows significantly elevated cobalt levels with normal or only slightly elevated chromium levels. This contrasts with wear in metal-on-metal (MoM) articulations, where both Co and Cr are typically elevated.

Question 158

Topic: Total Hip Arthroplasty (THA)
A revision total hip arthroplasty is planned for a patient with a loose femoral stem. Preoperative templating and intraoperative findings demonstrate severe proximal bone loss with less than 3 cm of intact diaphyseal bone available for distal fixation. According to the Paprosky femoral defect classification, which of the following stem designs is most appropriate for reliable fixation?
. A fully porous-coated cylindrical non-modular stem.
. A cemented, polished, double-tapered collarless stem.
. A fluted, tapered, modular uncemented stem.
. A short metaphyseal-fitting proximally coated stem.
. A standard length, proximally porous-coated tapered wedge stem.

Correct Answer & Explanation

. A fluted, tapered, modular uncemented stem.

Explanation

This is a Paprosky Type IIIB femoral defect. It is characterized by severe proximal bone loss and an unsupported diaphysis with less than 4 cm of scratch fit available for a cylindrical stem. A fully porous-coated cylindrical stem (which requires at least 4 cm of intact diaphysis, i.e., Type IIIA) has a high failure rate in this setting. The treatment of choice for a Type IIIB defect is a fluted, tapered uncemented stem (often modular), which relies on a 3-point bending fit and axial splining rather than pure cylindrical diaphyseal scratch fit.

Question 159

Topic: Total Hip Arthroplasty (THA)

During a complex revision THA requiring removal of a well-fixed porous-coated stem, the surgeon decides to perform an Extended Trochanteric Osteotomy (ETO). To optimize the probability of bony union of the osteotomized fragment, meticulous care is taken to preserve its vascular pedicle. The primary blood supply to the ETO fragment is maintained by the attachments of which of the following muscles?

. Gluteus medius and minimus.
. Tensor fasciae latae.
. Vastus lateralis.
. Quadratus femoris.
. Piriformis and superior gemellus.

Correct Answer & Explanation

. Vastus lateralis.

Explanation

The Extended Trochanteric Osteotomy (ETO) is a highly reliable technique for extraction of fixed femoral components. The osteotomy involves the greater trochanter and a lateral strut of the femoral diaphysis. To ensure healing, the vascular supply to the lateral diaphyseal bone must be preserved. This is primarily provided by the vastus lateralis muscle (which receives its blood supply from the descending branch of the lateral femoral circumflex artery). The gluteus medius provides some supply to the proximal tip, but the extensive diaphyseal portion relies on the vastus lateralis.

Question 160

Topic: Total Hip Arthroplasty (THA)
A patient undergoing revision THA is found to have an acetabular defect with severe ischial osteolysis, superior migration of the acetabular component greater than 3 cm, and the radiographic "teardrop" is completely absent on the AP pelvis radiograph. The Kohler line remains intact. What is the Paprosky classification of this acetabular defect?
. Paprosky IIB
. Paprosky IIC
. Paprosky IIIA
. Paprosky IIIB
. Pelvic discontinuity

Correct Answer & Explanation

. Paprosky IIIA

Explanation

Paprosky IIIA represents severe bone loss with >3 cm of superior migration (often measured from the obturator foramen), severe ischial lysis, and an absent teardrop, but the Kohler line is intact (meaning no medial migration). Paprosky IIIB defects involve medial migration past the Kohler line.

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