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 181
Topic: Total Hip Arthroplasty (THA)
Anteromedial approach (Ludloff)
Correct Answer & Explanation
. Lateral femoral cutaneous
Explanation
DISCUSSIONThe lateral femoral cutaneous nerve can be injured during a direct anterior approach to the hip. The superior gluteal nerve enters the gluteus medius from posterior to anterior approximately 5 cm above the greater trochanter. This nerve can be injured during the direct lateral and anterolateral approaches to the hip. Branches of the inferior gluteal nerve as well as the sciatic nerve can be injured during the posterior approach, and the obturator nerve can be damaged when performing a medial approach to the hip.
Question 182
Topic: Total Hip Arthroplasty (THA)
The dorsal (Thompson) approach to the proximal forearm uses which of the following intermuscular intervals?
Correct Answer & Explanation
. Extensor digitorum communis and the extensor carpi radialis brevis
Explanation
DISCUSSION: The Thompson posterior approach is used in treatment of fractures of the proximal radius. Dissection is carried out through the interval between the extensor carpi radialis brevis (radial nerve) and the extensor digitorum communis (posterior interosseous nerve). To identify this interval, the forearm is pronated and the mobile lateral wad of muscles (the ulnar-most belly is the extensor carpi radialis brevis) is grasped with the thumb and finger and pulled from the much less mobile mass of the extensor digitorum communis. The furrow created is marked with a skin marker for subsequent skin incision. The skin incision follows a line from the lateral epicondyle of the humerus to a point corresponding to the middle of the posterior aspect of the wrist. Distally, the intermuscular plane is between the extensor carpi radialis brevis and the extensor pollicis longus. REFERENCES: Crenshaw AH Jr: Surgical techniques and approaches, in Canale ST (ed): Campbell’s Operative Orthopaedics, ed 9. St Louis, MO, Mosby-Year Book, 1998, vol 1, pp 128-129. Hoppenfeld S, deBoer P: Posterior approach to the radius, in Surgical Exposures in Orthopaedics: The Anatomic Approach, ed 2. Philadelphia, PA, Lippincott-Raven, 1992, pp 136-146. Thompson JE: Anatomical methods of approach in operations on the long bones of the extremities. Ann Surg 1918;68:309-316.
Question 183
Topic: Total Hip Arthroplasty (THA)
Design and manufacturing of a metal-on-metal articulation has an important influence on the tribology. Which of the following statements best characterizes the type of contact that is best for metal-on-metal articulations?
Correct Answer & Explanation
. Polar contact should exceed equatorial contact.
Explanation
DISCUSSION: It is important that the radii of a metal-on-metal head to cup articulation be such that there is polar contact. As the radii become closer to equal, conditions favor higher frictional torque and equatorial seizing. The “bedding in” of metal-on-metal surfaces and their stiffness are both components of the properties considered in the design of polar contact surfaces.
Question 184
Topic: Total Hip Arthroplasty (THA)
Figures 24a and 24b are the radiographs of a 7-year-old boy who fell off the monkey bars and has a closed injury. His hand appears warm and well perfused with an absent radial pulse. What is the best initial treatment?
Correct Answer & Explanation
. Immediate open reduction with an anterior approach
Explanation
DISCUSSIONIn displaced extension-type supracondylar fractures, the neurovascular structures get kinked anteriorly or anteromedially related to the displacement. In almost all cases, there is a spontaneous resolution of this kink following closed fracture reduction.
Question 185
Topic: Total Hip Arthroplasty (THA)
A 23-year-old man is involved in a motor vehicle accident. An AP radiograph is shown in Figure 29a, and axial and sagittal CT scans are shown in Figures 29b and 29c. Neurologic examination shows 1/5 strength of his quadriceps and iliopsoas on the right, with 1/5 quadriceps function on the left. Definitive treatment of his injury should consist of Review Topic
Correct Answer & Explanation
. anterior corpectomy with interbody strut.
Explanation
The imaging studies show a fracture-dislocation. Surgical treatment of this injury consists of a decompression reduction, stabilization, and fusion. A posterolateral decompression can also be performed as necessary. An isolated anterior procedure in this type of injury is contraindicated. The anterior longitudinal ligament is most likely intact; therefore, an anterior procedure further destabilizes the spine. Reduction by an anterior approach would also be difficult. Nonsurgical management of the neurologic injury in this patient is not indicated.
Question 186
Topic: Total Hip Arthroplasty (THA)
Which of the following is considered a major characteristic of hyaluronate?
Correct Answer & Explanation
. Backbone of the proteoglycan aggregate
Explanation
DISCUSSION: Hyaluronate is a naturally occurring compound that is the backbone of the central core of the proteoglycan aggregate. Hyaluronate forms the base or central core of the aggregate on which a link protein binds a protein core.
Question 187
Topic: Total Hip Arthroplasty (THA)
A surgeon contemplates performing a hemiarthroplasty (HA) or total hip arthroplasty (THA) for an active, community ambulating 70-year-old female with a displaced femoral neck fracture. Which of the following is true for these options?
Correct Answer & Explanation
. Perioperative complication rate is greater after THA than bipolar HA
Explanation
THA has a higher perioperative complication rate than HA.There are a few differences between THA and HA performed in the setting of displaced FNF. THA has a higher dislocation rate, greater blood loss, requires a larger exposure than HA, and the operation is longer. HA often requires reoperation because of progressive acetabular erosion. Patient outcomes and function are greater following THA than HA.Florschultz et al. reviewed current management of FNF. They concluded that CRIF / ORIF is indicated for displaced femoral neck fractures in younger individuals, select active elderly, and medically unfit patients. HA is indicated for lower demand ambulatory older patients. THA is indicated for the active elderly and those with preexisting acetabular disease.Avery et al. reviewed 7-10 year results of an RCT comparing THA with HA. More HA patients had died during follow-up. All surviving patients had polyethylene wear (THA) and acetabular erosion (HA). They concluded that there was lower mortality and a trend towards superior function in patients with a THA in the medium term.Hedbeck et al. performed a RCT comparing HA and THA. At 4 years, there was improved function and quality of life with THA. They recommend THA in elderly, lucid patients with a displaced FNF.Incorrect Answers:
Question 188
Topic: Total Hip Arthroplasty (THA)
The stiffness of a 16-mm femoral stem is mostly influenced by the
Correct Answer & Explanation
. diameter of the femoral stem.
Explanation
The stiffness is most influenced by the geometry, in particular the diameter of the stem. The bending rigidity increases to the fourth power of the radius. The elastic modulus of the material increases as a direct linear relationship. The surface coating does not affect the bending rigidity greatly unless it increases the diameter significantly.
Question 189
Topic: Total Hip Arthroplasty (THA)
A 55-year-old male complains of a loud 'squeaking' noise coming from his hip 3 years after a ceramic-on-ceramic total hip arthroplasty. He is otherwise asymptomatic. Radiographs show a well-fixed implant. Which of the following is the most likely primary etiology of this phenomenon?
Correct Answer & Explanation
. Third-body wear from retained cement debris
Explanation
Squeaking in ceramic-on-ceramic THA is heavily associated with edge loading, which typically occurs due to component malposition (e.g., increased acetabular anteversion/inclination or loss of femoral offset). Edge loading leads to stripe wear on the ceramic head, altering fluid film lubrication and generating the audible squeak. It is generally not caused by galvanic corrosion or cement debris.
Question 190
Topic: Total Hip Arthroplasty (THA)
A patient is undergoing deformity correction for a midshaft tibial malunion. According to Paley's rules of osteotomies, if the osteotomy is performed at a site separate from the Center of Rotation of Angulation (CORA) and the proximal and distal mechanical axes are aligned, what is the inevitable geometric result?
Correct Answer & Explanation
. Translation (displacement) at the osteotomy site
Explanation
According to Osteotomy Rule 2, when the osteotomy is performed outside the CORA and the axes are realigned, the bone ends will translate (displace) at the osteotomy site. This translation must be accommodated to restore the mechanical axis.
Question 191
Topic: Total Hip Arthroplasty (THA)
Figure 1 shows the radiograph obtained from a 60-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 4 ng/mL, compared with a normal level of less than 3 ng/mL, and a cobalt level of 8 ng/mL, compared with a normal level less than 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?
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 have raised numerous concerns. 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 192
Topic: Total Hip Arthroplasty (THA)
A 55-year-old highly active male underwent a primary total hip arthroplasty 2 years ago using a ceramic-on-ceramic bearing. He is very satisfied with his pain relief but complains of an audible 'squeaking' noise from the hip when rising from a chair. Which of the following factors is most strongly associated with this complication?
Correct Answer & Explanation
. Use of an undersized femoral stem
Explanation
Squeaking is a specific complication of ceramic-on-ceramic (CoC) bearings, occurring in up to 10% of patients. The noise is strongly associated with component malposition (e.g., steep inclination or excessive anteversion of the acetabular cup), which leads to edge loading. This causes micro-separation, disrupts fluid film lubrication, and leads to stripe wear and the resulting squeak.
Question 193
Topic: Total Hip Arthroplasty (THA)
During a total hip arthroplasty via a posterior approach, the surgeon inadvertently utilizes a femoral component with significantly less femoral offset than the patient's native anatomy, though leg lengths are perfectly restored. Postoperatively, the patient experiences recurrent posterior dislocations. Decreasing femoral offset contributes to joint instability primarily through which of the following mechanisms?
Correct Answer & Explanation
. Increasing the distance between the greater trochanter and the center of rotation
Explanation
Femoral offset is the horizontal distance from the center of rotation of the femoral head to a line bisecting the long axis of the femur. Decreasing femoral offset shortens the lever arm of the abductor musculature. This results in relative soft tissue laxity and weakness of the abductors, which significantly decreases the stability of the hip joint and increases the risk of dislocation. It can also lead to earlier bony impingement between the greater trochanter and the pelvis.
Question 194
Topic: Total Hip Arthroplasty (THA)
A 55-year-old highly active female underwent a right total hip arthroplasty using a ceramic-on-ceramic bearing 3 years ago. She now complains of a high-pitched squeaking noise during gait, particularly when extending her hip. Which of the following component position factors is most strongly associated with this phenomenon?
Correct Answer & Explanation
. Acetabular cup retroversion
Explanation
Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which often results from an unacceptably steep acetabular cup (inclination > 55 degrees). Edge loading disrupts the fluid film lubrication, leading to stripe wear and audible squeaking.
Question 195
Topic: Total Hip Arthroplasty (THA)
A 70-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Intraoperatively, she is noted to dislocate anteriorly with the hip in extension, external rotation, and adduction. What is the most likely cause of this specific instability pattern?
Correct Answer & Explanation
. Inadequate offset of the femoral stem
Explanation
Anterior dislocation of a THA (occurring in extension and external rotation) is classically caused by excessive combined anteversion, most commonly due to excessive anteversion of the acetabular component. Retroverted cups tend to dislocate posteriorly in flexion and internal rotation.
Question 196
Topic: Total Hip Arthroplasty (THA)
A patient dislocates their total hip arthroplasty anteriorly during extension and external rotation. Which of the following component malpositions is most commonly associated with this specific direction of instability?
Correct Answer & Explanation
. Excessive retroversion of the acetabular component
Explanation
Anterior dislocation of a THA typically occurs with the hip in extension and external rotation. It is most commonly associated with excessive anteversion of the acetabular or femoral components.
Question 197
Topic: Total Hip Arthroplasty (THA)
A 55-year-old female presents with persistent anterior groin pain exacerbated by active straight leg raise 6 months after a total hip arthroplasty. What is the most common iatrogenic cause of this condition?
Correct Answer & Explanation
. Retroversion of the acetabular component
Explanation
Iliopsoas impingement post-THA is classically caused by anterior overhang of the acetabular shell. The iliopsoas tendon rubs against the prominent metal edge during active flexion, causing pain and tendinitis.
Question 198
Topic: Total Hip Arthroplasty (THA)
A 70-year-old female is evaluated for a total hip arthroplasty (THA). Radiographs reveal a prior L2-S1 posterior spinal fusion. Standing and sitting lateral spinopelvic radiographs demonstrate a change in pelvic tilt of 5 degrees. Based on her spinopelvic biomechanics, what THA component positioning strategy is recommended to minimize dislocation risk?
Correct Answer & Explanation
. Increase acetabular cup anteversion
Explanation
This patient has a stiff spinopelvic junction (<10 degrees change in pelvic tilt from standing to sitting). To compensate for the lack of increased pelvic retroversion while sitting, the surgeon should increase the acetabular cup anteversion and/or inclination to prevent anterior impingement and posterior dislocation.
Question 199
Topic: Total Hip Arthroplasty (THA)
A 59-year-old active woman undergoes elective total hip replacement in which a posterior approach is used. She has minimal pain and is discharged to home 2 days after surgery. Four weeks later, she dislocates her hip while shaving her legs. She undergoes a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?
Correct Answer & Explanation
. Observation and patient education regarding hip dislocation precautions
Explanation
First-time early dislocations are often treated successfully without revision surgery, especially when no component malalignment is present. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful but is usually reserved for patients with recurrent dislocations.
Question 200
Topic: Total Hip Arthroplasty (THA)
A 55-year-old woman undergoes a primary THA using a ceramic-on-ceramic bearing. Two years later, she complains of an audible squeaking sound from her hip during walking, without associated pain. Radiographs show well-fixed components. Which of the following is most strongly associated with the development of squeaking in ceramic-on-ceramic THA?
Correct Answer & Explanation
. Edge loading due to component malposition
Explanation
Squeaking in ceramic-on-ceramic THA is most commonly associated with edge loading, which typically occurs due to component malposition (e.g., excessive cup anteversion, excessive cup abduction, or extreme combinations causing microseparation during gait).
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