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1. General Principles & Basic Science MCQs

Practice Set 437 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 8721

Topic: Surgical Anatomy & Approaches

During surgical approaches to the adult hip, care must be taken to preserve the primary blood supply to the femoral head. This critical blood supply is predominantly derived from which of the following vessels?

. Superficial femoral artery
. Ascending branch of the lateral femoral circumflex artery
. Deep branch of the medial femoral circumflex artery
. Obturator artery via the ligamentum teres
. Inferior gluteal artery

Correct Answer & Explanation

. Deep branch of the medial femoral circumflex artery

Explanation

The major blood supply to the adult femoral head is the deep branch of the medial femoral circumflex artery (MFCA). The contribution from the artery of the ligamentum teres (obturator artery) is negligible in adults.

Question 8722

Topic: Surgical Anatomy & Approaches

The direct anterior approach to the hip utilizes an internervous plane. This plane is located between muscles supplied by which two nerves?

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

Correct Answer & Explanation

. Superior gluteal and femoral nerves

Explanation

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

Question 8723

Topic: Biomechanics & Biomaterials

Highly cross-linked polyethylene (HXLPE) is utilized in THA to substantially reduce wear rates. What is a known mechanical consequence of the post-irradiation melting or annealing process used to eliminate free radicals?

. Increased ultimate tensile strength
. Increased volumetric wear
. Decreased yield strength and fatigue resistance
. Enhanced oxidative degradation over time
. Improved resistance to impingement damage

Correct Answer & Explanation

. Decreased yield strength and fatigue resistance

Explanation

While cross-linking and subsequent melting/annealing dramatically improve wear characteristics and eliminate free radicals, the process alters the crystalline structure of the polymer. This results in reduced mechanical properties, specifically decreased yield strength, fatigue resistance, and ductility.

Question 8724

Topic: Surgical Anatomy & Approaches

During a primary total hip arthroplasty, excessive traction or errant placement of an anterior retractor over the anterior rim of the acetabulum poses the greatest risk to which of the following structures?

. Sciatic nerve
. Superior gluteal nerve
. Femoral nerve
. Obturator nerve
. Pudendal nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Retractors placed aggressively over the anterior wall of the acetabulum can compress the structures passing under the inguinal ligament. The femoral nerve and vessels are highly susceptible to stretch or compression injury in this location.

Question 8725

Topic: Surgical Anatomy & Approaches

A 65-year-old female undergoes a total hip arthroplasty via the direct anterior (Smith-Petersen) approach. Postoperatively, she demonstrates profound weakness in hip flexion and knee extension, with diminished sensation over the anterior thigh. Which of the following structures was most likely injured during the procedure?

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

Correct Answer & Explanation

. Femoral nerve

Explanation

The femoral nerve is at risk during the direct anterior approach to the hip, particularly from overly aggressive placement of the medial retractor. Injury results in weakness of the quadriceps (knee extension) and iliopsoas (hip flexion).

Question 8726

Topic: Biology, Genetics & Bone Healing
A 38-year-old man on chronic corticosteroids for systemic lupus erythematosus presents with severe left hip pain. Radiographs reveal a subchondral radiolucent line (crescent sign) with mild collapse of the femoral head, but the joint space is well preserved. What is the correct Ficat stage for this patient's disease?
. Ficat Stage I
. Ficat Stage II
. Ficat Stage III
. Ficat Stage IV
. Transient osteoporosis of the hip

Correct Answer & Explanation

. Ficat Stage III

Explanation

Ficat Stage III osteonecrosis of the femoral head is defined by the presence of a subchondral crescent sign or mild cortical collapse, with preservation of the joint space. Once the joint space is narrowed or arthritic changes occur, the disease progresses to Stage IV.

Question 8727

Topic: Biology, Genetics & Bone Healing

In particle-induced periprosthetic osteolysis surrounding a total hip arthroplasty, macrophages ingest wear debris and release inflammatory cytokines. Which downstream biological mediator is primarily responsible for the direct activation of osteoclasts in this process?

. Interleukin-10 (IL-10)
. Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL)
. Osteoprotegerin (OPG)
. Transforming Growth Factor-beta (TGF-beta)
. Bone Morphogenetic Protein-2 (BMP-2)

Correct Answer & Explanation

. Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL)

Explanation

Macrophage-released cytokines (such as TNF-alpha, IL-1, and IL-6) upregulate the expression of RANKL. RANKL then binds to the RANK receptor on osteoclast precursors, stimulating their differentiation and direct activation, leading to osteolysis.

Question 8728

Topic: Infection, Pharmacology & VTE

A 52-year-old female presents with persistent lateral hip pain exacerbated by prolonged walking and lying on the affected side. Physical examination reveals localized point tenderness directly over the greater trochanter. She has failed physical therapy and NSAIDs. When performing a corticosteroid injection, which anatomical space is the primary target?

. Intra-articular hip joint
. Subgluteus minimus bursa
. Subgluteus medius bursa
. Subgluteus maximus (trochanteric) bursa
. Ischial bursa

Correct Answer & Explanation

. Subgluteus maximus (trochanteric) bursa

Explanation

Greater trochanteric pain syndrome (GTPS) is most commonly related to pathology of the gluteus medius/minimus tendons or inflammation of the overlying bursa. Therapeutic corticosteroid injections for GTPS are targeted into the subgluteus maximus (trochanteric) bursa.

Question 8729

Topic: Surgical Anatomy & Approaches

A 68-year-old woman is scheduled for a total hip arthroplasty via a direct anterior approach. Which of the following neurologic structures is at greatest risk of injury during the superficial surgical dissection?

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

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior approach to the hip uses the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve is at highest risk during the superficial dissection.

Question 8730

Topic: Surgical Anatomy & Approaches

A 40-year-old woman undergoes a periacetabular osteotomy (PAO) for symptomatic developmental dysplasia of the hip. During the procedure, the ilioischial osteotomy is performed. Which of the following nerves is at greatest risk of injury during this specific osteotomy cut?

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

Correct Answer & Explanation

. Sciatic nerve

Explanation

The sciatic nerve lies in close proximity to the posterior column of the acetabulum. It is at highest risk of injury during the ilioischial (posterior) osteotomy phase of a Bernese periacetabular osteotomy if the osteotome penetrates too deeply.

Question 8731

Topic: Surgical Anatomy & Approaches

A 65-year-old woman undergoes a direct anterior approach THA. Postoperatively, she reports a patch of numbness over the anterolateral aspect of her proximal thigh. Motor function is intact. Which nerve was most likely injured during the surgical exposure?

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

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The lateral femoral cutaneous nerve is at risk during the direct anterior approach (Smith-Petersen interval) to the hip, leading to sensory loss over the anterolateral thigh without motor deficits.

Question 8732

Topic: Surgical Anatomy & Approaches

A 62-year-old woman undergoes a primary THA via a direct anterior approach. Postoperatively, she reports numbness and a burning sensation over the anterolateral aspect of her operative thigh. Which anatomic interval was most likely utilized, leading to this specific nerve injury risk?

. Tensor fasciae latae and sartorius
. Gluteus medius and tensor fasciae latae
. Gluteus maximus and medius
. Rectus femoris and vastus lateralis
. Sartorius and rectus femoris

Correct Answer & Explanation

. Sartorius and rectus femoris

Explanation

The direct anterior (Smith-Petersen) approach exploits the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve crosses this interval and is at risk for iatrogenic injury.

Question 8733

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for a total hip arthroplasty, the surgeon develops the internervous plane between the tensor fasciae latae and the sartorius. Which of the following neurologic structures is at greatest risk of injury during the superficial dissection?

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

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior approach utilizes the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve courses superficially over the sartorius and is highly vulnerable to traction or transection during the superficial dissection.

Question 8734

Topic: Surgical Anatomy & Approaches

A 45-year-old woman with Crowe Type IV developmental dysplasia of the hip is scheduled for a total hip arthroplasty. Her femoral head is completely dislocated superior to the true acetabulum. If the acetabular component is placed in the true acetabulum, which of the following is most likely required to achieve reduction and prevent nerve injury?

. Greater trochanteric advancement
. Femoral nerve release at the inguinal ligament
. Subtrochanteric femoral shortening osteotomy
. Acetabular structural bone grafting
. Psoas tendon lengthening

Correct Answer & Explanation

. Subtrochanteric femoral shortening osteotomy

Explanation

In Crowe IV dysplasia, the femoral head is dislocated proximally. Bringing the hip down to the true acetabulum significantly lengthens the leg, placing the sciatic nerve at high risk for traction injury, which necessitates a subtrochanteric femoral shortening osteotomy.

Question 8735

Topic: Biomechanics & Biomaterials
Irradiation of ultra-high molecular weight polyethylene (UHMWPE) is commonly performed to improve wear characteristics. What is the primary disadvantage of increasing the irradiation dose during the cross-linking process?
. Increased oxidation potential
. Decreased fatigue strength
. Decreased adhesive wear resistance
. Increased abrasive wear
. Decreased ultimate tensile strength by free radical formation

Correct Answer & Explanation

. Decreased fatigue strength

Explanation

Highly cross-linked polyethylene significantly improves wear resistance but at the cost of diminished mechanical properties. The primary disadvantage is a reduction in fatigue strength, ductility, and fracture toughness.

Question 8736

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for total hip arthroplasty, the surgeon develops the superficial internervous plane. Which two nerves supply the muscles that form the boundaries of this specific interval?

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

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

The superficial interval of the direct anterior approach is between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The deep interval is between the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).

Question 8737

Topic: Infection, Pharmacology & VTE

A 4-year-old boy presents with right hip pain, refusal to bear weight, a temperature of 38.8 C (101.8 F), an ESR of 45 mm/hr, and a serum WBC count of 13,000/mm3. According to the Kocher criteria, what is the probability that he has septic arthritis?

. 2%
. 40%
. 71%
. 93%
. 99%

Correct Answer & Explanation

. 99%

Explanation

The four Kocher criteria are non-weight-bearing, temperature >38.5 C, ESR >40 mm/hr, and WBC >12,000. With all 4 criteria present, the probability of septic arthritis is approximately 99%.

Question 8738

Topic: Surgical Anatomy & Approaches

Following a primary total hip arthroplasty via a direct anterior approach, the patient complains of numbness over the anterolateral aspect of the thigh. Motor function of the lower extremity is intact. Which nerve is most likely affected?

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

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior approach utilizes the internervous plane between the tensor fasciae latae and sartorius. The lateral femoral cutaneous nerve is at highest risk, leading to meralgia paresthetica if injured.

Question 8739

Topic: Surgical Anatomy & Approaches

The direct anterior approach for total hip arthroplasty utilizes an internervous plane between which two muscles?

. Tensor fasciae latae and gluteus medius
. Sartorius and tensor fasciae latae
. Gluteus medius and piriformis
. Rectus femoris and vastus lateralis
. Adductor longus and gracilis

Correct Answer & Explanation

. Sartorius and tensor fasciae latae

Explanation

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

Question 8740

Topic: Physiology & Rehabilitation

During the single-leg stance phase of gait, the hip abductor musculature must generate a force approximately how many times body weight to maintain a level pelvis?

. 0.5 times
. 1 times
. 2.5 times
. 4.5 times
. 6 times

Correct Answer & Explanation

. 2.5 times

Explanation

To counteract the moment arm of body weight acting on the center of gravity during single-leg stance, the hip abductors must exert a force roughly 2.5 times body weight. This results in a total joint reaction force of about 3.5 times body weight.

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