Menu

1. General Principles & Basic Science MCQs

Practice Set 419 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 8361

Topic: 1. General Principles & Basic Science

A 70-year-old female complains of severe lateral-sided right hip pain and a prominent limp. Examination reveals weakness in hip abduction and a positive Trendelenburg sign. MRI demonstrates a complete discontinuity of the tendon inserting onto the lateral facet of the greater trochanter. Which muscle is affected?

. Gluteus maximus
. Gluteus medius
. Gluteus minimus
. Tensor fasciae latae
. Piriformis

Correct Answer & Explanation

. Gluteus medius

Explanation

The gluteus medius inserts on the lateral and superoposterior facets of the greater trochanter. A tear of this tendon results in abductor weakness, a positive Trendelenburg sign, and refractory lateral hip pain.

Question 8362

Topic: Surgical Anatomy & Approaches

A 60-year-old man undergoes a total hip arthroplasty via a direct anterior approach using the primary inter-nervous plane between the tensor fasciae latae and the sartorius. Postoperatively, he complains of numbness and a burning sensation over the anterolateral aspect of his operative thigh. Which nerve was most likely injured during the surgical exposure, and what are its corresponding nerve roots?

. Femoral nerve (L2-L4)
. Sciatic nerve (L4-S3)
. Lateral femoral cutaneous nerve (L2-L3)
. Superior gluteal nerve (L4-S1)
. Obturator nerve (L2-L4)

Correct Answer & Explanation

. Lateral femoral cutaneous nerve (L2-L3)

Explanation

The direct anterior approach to the hip utilizes the superficial internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). The lateral femoral cutaneous nerve (LFCN), derived from the L2-L3 nerve roots, passes over or through the sartorius muscle and is at high risk of stretch or iatrogenic transection during this approach. Injury leads to meralgia paresthetica (numbness/burning over the anterolateral thigh).

Question 8363

Topic: Surgical Anatomy & Approaches

A 55-year-old woman undergoes a primary right total hip arthroplasty via a direct anterior approach. Postoperatively, she reports a burning sensation and numbness over the anterolateral aspect of her right thigh. Motor function of her lower extremity is completely intact. During the surgical approach, which of the following internervous planes was utilized, and which nerve is most likely injured?

. Sartorius and Tensor Fasciae Latae; Lateral femoral cutaneous nerve
. Gluteus Medius and Tensor Fasciae Latae; Superior gluteal nerve
. Sartorius and Rectus Femoris; Femoral nerve
. Gluteus Maximus and Gluteus Medius; Sciatic nerve
. Adductor Longus and Gracilis; Obturator nerve

Correct Answer & Explanation

. Sartorius and Tensor Fasciae Latae; Lateral femoral cutaneous nerve

Explanation

The direct anterior approach (Smith-Petersen) to the hip utilizes the superficial internervous plane between the sartorius (supplied by the femoral nerve) and the tensor fasciae latae (supplied by the superior gluteal nerve). The lateral femoral cutaneous nerve (LFCN) is entirely sensory, supplying the anterolateral thigh. It typically crosses over the sartorius muscle distally and is at high risk of stretch or transection during the superficial dissection of the direct anterior approach.

Question 8364

Topic: Physiology & Rehabilitation

A 70-year-old woman is evaluated 6 months after a total hip arthroplasty performed via a direct lateral (Hardinge) approach. She complains of persistent lateral hip pain and a prominent limp. On physical examination, when she stands on the operatively treated leg, her pelvis drops on the contralateral, unaffected side. To compensate during the stance phase of her gait cycle, the patient will most likely demonstrate which of the following kinematic adaptations?

. A compensatory lurch of the trunk toward the affected side
. A compensatory lurch of the trunk away from the affected side
. Excessive hip flexion resulting in a steppage gait
. Circumduction of the affected lower extremity
. Vaulting on the unaffected limb

Correct Answer & Explanation

. A compensatory lurch of the trunk toward the affected side

Explanation

The patient has a positive Trendelenburg sign due to insufficiency of the hip abductors (gluteus medius and minimus), a known complication of the direct lateral approach which splits these muscles. When standing on the affected leg, the weak abductors cannot hold the pelvis level, causing it to drop on the unaffected side. To compensate and prevent falling, the patient exhibits a Trendelenburg gait, shifting their trunk and center of gravity toward the affected stance leg. This reduces the lever arm from the center of gravity to the hip joint, thereby decreasing the torque demand on the deficient abductor muscles.

Question 8365

Topic: Biomechanics & Biomaterials

Regarding the material properties of highly cross-linked polyethylene (HXLPE) used in total hip arthroplasty, increasing the radiation dose to enhance cross-linking primarily results in a trade-off characterized by which of the following mechanical changes?

. Decreased oxidation resistance
. Increased ultimate tensile strength
. Decreased fatigue crack propagation resistance
. Decreased melting point
. Increased volumetric wear rate

Correct Answer & Explanation

. Decreased fatigue crack propagation resistance

Explanation

Highly cross-linked polyethylene (HXLPE) is created by exposing standard ultra-high-molecular-weight polyethylene to ionizing radiation, which forms free radicals that recombine to create cross-links between polymer chains. While this significantly decreases the volumetric wear rate, it comes at the cost of decreasing several mechanical properties, particularly fatigue resistance, ductility, yield strength, and ultimate tensile strength. Therefore, decreased fatigue crack propagation resistance is the primary mechanical trade-off of higher cross-linking doses. Oxidation resistance is typically addressed by subsequent thermal treatments (remelting or annealing) or adding antioxidants like Vitamin E.

Question 8366

Topic: Surgical Anatomy & Approaches

A surgeon is performing a primary total hip arthroplasty using a direct anterior approach.

The internervous plane utilized is between the tensor fasciae latae and the sartorius superficially. During the exposure, care must be taken to avoid a nerve that typically crosses the surgical field. Injury to this structure will most likely result in:

. Weakness of hip abduction
. Weakness of hip flexion
. Sensory loss over the anterolateral aspect of the thigh
. Sensory loss over the medial aspect of the thigh
. A positive Trendelenburg gait

Correct Answer & Explanation

. Sensory loss over the anterolateral aspect of the thigh

Explanation

The direct anterior approach (Smith-Petersen) utilizes the superficial internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve (LFCN) is at significant risk during this superficial dissection. It is a purely sensory nerve providing innervation to the anterolateral thigh. Injury to the LFCN results in sensory loss, numbness, or dysesthesia over the anterolateral aspect of the thigh (meralgia paresthetica), without causing any motor weakness.

Question 8367

Topic: 1. General Principles & Basic Science

A 68-year-old male is undergoing a two-stage exchange arthroplasty for a chronically infected total hip arthroplasty. Preoperative joint aspiration cultures confirm the presence of methicillin-resistant Staphylococcus aureus (MRSA). During the first stage, the components are explanted, aggressive debridement is performed, and an articulating polymethylmethacrylate (PMMA) cement spacer is placed. Which of the following represents the most appropriate antibiotic loading strategy for the PMMA spacer in this patient?

. Vancomycin and tobramycin
. Cefazolin alone
. Penicillin and gentamicin
. Ciprofloxacin and rifampin
. Erythromycin alone

Correct Answer & Explanation

. Vancomycin and tobramycin

Explanation

In the setting of a two-stage exchange for periprosthetic joint infection (PJI), high-dose antibiotic-loaded PMMA is utilized to provide high local antibiotic concentrations while maintaining mechanical stability. For MRSA, vancomycin is the antibiotic of choice. It is highly recommended to combine vancomycin with an aminoglycoside (such as tobramycin or gentamicin) in the cement spacer. This combination is synergistic, broadens the spectrum of coverage, and importantly, increases the elution characteristics of both antibiotics from the PMMA matrix through passive diffusion (the 'synergistic elution' effect). Cefazolin, penicillin, and erythromycin do not cover MRSA. While rifampin is an excellent anti-biofilm agent used systemically, it can interfere with cement polymerization and is not typically used as the primary local antibiotic in spacers.

Question 8368

Topic: Surgical Anatomy & Approaches

During a total hip arthroplasty utilizing the direct anterior (Smith-Petersen) approach, the internervous plane is developed between the tensor fasciae latae (TFL) and the sartorius. Which of the following nerves is at greatest risk of iatrogenic injury during the superficial dissection and subsequent retractor placement?

. Superior gluteal nerve
. Femoral nerve
. Lateral femoral cutaneous nerve
. Sciatic nerve
. Obturator nerve

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior approach utilizes the internervous plane between the TFL (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve (LFCN) courses over the sartorius and is highly susceptible to injury during the superficial dissection or from retractor compression, potentially leading to meralgia paresthetica.

Question 8369

Topic: Surgical Anatomy & Approaches

The direct anterior approach (Smith-Petersen) to the hip is frequently utilized in primary total hip arthroplasty to exploit a true internervous plane. Which of the following best describes the superficial internervous plane utilized in this approach?

. Between the Sartorius (femoral nerve) and Tensor Fasciae Latae (superior gluteal nerve)
. Between the Rectus Femoris (femoral nerve) and Gluteus Medius (superior gluteal nerve)
. Between the Pectineus (femoral nerve) and Iliopsoas (femoral nerve)
. Between the Gluteus Maximus (inferior gluteal nerve) and Gluteus Medius (superior gluteal nerve)
. Between the Adductor Longus (obturator nerve) and Gracilis (obturator nerve)

Correct Answer & Explanation

. Between the Sartorius (femoral nerve) and Tensor Fasciae Latae (superior gluteal nerve)

Explanation

The direct anterior approach (Smith-Petersen) utilizes the true internervous and intermuscular plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve) superficially. The deep interval is between the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).

Question 8370

Topic: Biology, Genetics & Bone Healing

Which of the following Magnetic Resonance Imaging (MRI) findings is considered highly specific for the early diagnosis of avascular necrosis (osteonecrosis) of the femoral head prior to the appearance of radiographic changes?

. Diffuse bone marrow edema extending into the intertrochanteric region
. A solitary large subchondral cyst
. The 'double-line' sign on T2-weighted images
. Thickening and hyperintensity of the ligamentum teres
. Significant intra-articular joint effusion with synovial hypertrophy

Correct Answer & Explanation

. The 'double-line' sign on T2-weighted images

Explanation

The 'double-line' sign seen on T2-weighted MRI is considered highly specific for osteonecrosis (AVN) of the femoral head. It represents the reactive interface between necrotic and viable bone. The inner hyperintense (bright) line represents highly vascularized granulation tissue, while the outer hypointense (dark) line corresponds to sclerotic bone. Diffuse bone marrow edema without a focal lesion is more characteristic of transient osteoporosis of the hip.

Question 8371

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is routinely utilized in total hip and knee arthroplasty to minimize perioperative blood loss and reduce transfusion requirements. Which of the following best describes the precise mechanism of action of tranexamic acid?
. It reversibly binds to lysine receptor sites on plasminogen, inhibiting the conversion of plasminogen to plasmin.
. It irreversibly binds to cyclooxygenase, inhibiting the synthesis of thromboxane A2.
. It directly inhibits Factor Xa in the common coagulation pathway.
. It enhances the activity of antithrombin III, accelerating the inactivation of thrombin.
. It stimulates the endothelial release of von Willebrand factor and Factor VIII.

Correct Answer & Explanation

. It reversibly binds to lysine receptor sites on plasminogen, inhibiting the conversion of plasminogen to plasmin.

Explanation

Tranexamic acid (TXA) is a synthetic analog of the amino acid lysine. It acts as an antifibrinolytic agent by reversibly binding to the lysine-binding sites on plasminogen molecules. This competitive inhibition prevents plasminogen from interacting with fibrin and delays its activation into plasmin. As a result, the degradation (fibrinolysis) of existing fibrin clots is significantly reduced, stabilizing clots and decreasing surgical bleeding.

Question 8372

Topic: Surgical Anatomy & Approaches
A 42-year-old woman with severe bilateral hip dysplasia presents for right THA. Preoperative standing AP pelvis radiographs demonstrate proximal migration of the femoral head such that it articulates with a false acetabulum. The proximal migration is measured at 110% of the normal vertical height of the femoral head. According to the Crowe classification, what is the appropriate diagnosis, and what adjunctive surgical technique is most likely required during THA?
. Crowe II; structural bone grafting of the superior acetabulum
. Crowe III; greater trochanteric advancement
. Crowe IV; subtrochanteric femoral shortening osteotomy
. Crowe IV; release of the transverse acetabular ligament only
. Crowe III; femoral nerve release

Correct Answer & Explanation

. Crowe IV; subtrochanteric femoral shortening osteotomy

Explanation

The Crowe classification characterizes the severity of DDH based on proximal migration. Crowe IV is defined as >100% proximal migration (or >20% of the pelvic height). In Crowe IV hips, bringing the femoral head down to the true acetabulum often results in excessive tension on the sciatic nerve. To safely reduce the hip and protect the neurovascular structures, a subtrochanteric femoral shortening osteotomy is frequently required.

Question 8373

Topic: Surgical Anatomy & Approaches

A surgeon is performing a primary total hip arthroplasty utilizing the direct anterior approach (Smith-Petersen). Development of the superficial internervous plane is required for initial exposure. Which two muscles define this superficial plane, and what are their respective innervations?

. Sartorius (Femoral nerve) and Tensor fasciae latae (Superior gluteal nerve)
. Rectus femoris (Femoral nerve) and Gluteus medius (Superior gluteal nerve)
. Tensor fasciae latae (Superior gluteal nerve) and Gluteus medius (Superior gluteal nerve)
. Gluteus maximus (Inferior gluteal nerve) and Tensor fasciae latae (Superior gluteal nerve)
. Sartorius (Obturator nerve) and Gracilis (Obturator nerve)

Correct Answer & Explanation

. Sartorius (Femoral nerve) and Tensor fasciae latae (Superior gluteal nerve)

Explanation

The direct anterior approach utilizes a true internervous and intermuscular plane. Superficially, the dissection passes between the sartorius muscle (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). The deep intermuscular plane is between the rectus femoris (femoral nerve) and the gluteus medius (superior gluteal nerve).

Question 8374

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for total hip arthroplasty, the surgeon dissects through an internervous plane. Which two nerves supply the muscles that form the superficial boundary of this interval?

. Femoral nerve and Obturator nerve
. Superior gluteal nerve and Inferior gluteal nerve
. Femoral nerve and Superior gluteal nerve
. Sciatic nerve and Superior gluteal nerve
. Femoral nerve and Sciatic nerve

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

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

Question 8375

Topic: Surgical Anatomy & Approaches

During a direct anterior approach to the hip, which internervous plane is utilized?

. Femoral nerve and Superior gluteal nerve
. Femoral nerve and Sciatic nerve
. Superior gluteal nerve and Inferior gluteal nerve
. Obturator nerve and Femoral nerve
. Sciatic nerve and Superior gluteal nerve

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

The direct anterior approach (Smith-Petersen) utilizes the true internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 8376

Topic: Surgical Anatomy & Approaches

The direct anterior (Smith-Petersen) approach to the hip is popular for total hip arthroplasty because it exploits a true internervous plane. Which two muscles define the superficial interval of this approach?

. Tensor fasciae latae and sartorius
. Gluteus medius and tensor fasciae latae
. Sartorius and rectus femoris
. Gluteus maximus and gluteus medius
. Pectineus and adductor longus

Correct Answer & Explanation

. Tensor fasciae latae and sartorius

Explanation

The superficial interval for the direct anterior approach is between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 8377

Topic: Surgical Anatomy & Approaches

A 30-year-old male sustains a posterior hip dislocation in a motor vehicle collision. After closed reduction, he exhibits a foot drop and decreased sensation over the dorsum of his foot. Which nerve division is most likely injured?

. Femoral nerve
. Tibial division of sciatic nerve
. Peroneal division of sciatic nerve
. Obturator nerve
. Superior gluteal nerve

Correct Answer & Explanation

. Peroneal division of sciatic nerve

Explanation

Posterior hip dislocations most commonly injure the sciatic nerve. The common peroneal division is more susceptible to injury than the tibial division because of its more lateral position and tighter tethering at the fibular head.

Question 8378

Topic: Surgical Anatomy & Approaches

A 35-year-old male sustains an anterior column and anterior wall acetabular fracture. The surgeon elects to use an ilioinguinal approach. Which structure is located in the middle window of this surgical approach?

. Iliopsoas muscle and femoral nerve
. External iliac artery and vein
. Spermatic cord (or round ligament)
. Obturator artery and nerve
. Sciatic nerve

Correct Answer & Explanation

. External iliac artery and vein

Explanation

The ilioinguinal approach has three windows. The middle window contains the external iliac vessels, positioned between the iliopectineal fascia and the conjoint tendon.

Question 8379

Topic: Surgical Anatomy & Approaches

A primary THA is performed via the direct anterior approach. The internervous plane utilized is between muscles innervated by which of the following nerves?

. Superior gluteal and femoral nerves
. Superior gluteal and inferior gluteal nerves
. Femoral and obturator nerves
. Sciatic and superior gluteal nerves
. Inferior gluteal and obturator nerves

Correct Answer & Explanation

. Superior gluteal and femoral nerves

Explanation

The direct anterior approach uses the true internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). This preserves the abductor mechanism and minimizes denervation.

Question 8380

Topic: Infection, Pharmacology & VTE

A patient with a severe penicillin allergy (anaphylaxis) is undergoing THA. Current guidelines recommend which of the following single agents as the best alternative for surgical prophylaxis?

. Cefazolin
. Vancomycin
. Erythromycin
. Ciprofloxacin
. Aztreonam

Correct Answer & Explanation

. Vancomycin

Explanation

For patients with a severe, IgE-mediated penicillin allergy (e.g., anaphylaxis), Vancomycin or Clindamycin are the recommended single-agent alternatives for surgical prophylaxis in total joint arthroplasty.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page