Menu

1. General Principles & Basic Science MCQs

Practice Set 70 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 1381

Topic: 1. General Principles & Basic Science

A 55-year-old male feels a pop in the posterior aspect of his knee while deep squatting. An MRI reveals the finding typically associated with the image below.

If this specific medial meniscal lesion is left untreated, what is the primary biomechanical consequence?

. Increased anterior tibial translation
. Loss of hoop stresses leading to contact pressures equivalent to a total meniscectomy
. Isolated lateral compartment osteoarthritis
. Increased patellofemoral joint reaction forces
. Chronic patellar instability

Correct Answer & Explanation

. Loss of hoop stresses leading to contact pressures equivalent to a total meniscectomy

Explanation

A posterior root tear of the medial meniscus disrupts the circumferential fibers, leading to medial meniscus extrusion and a complete loss of hoop stresses. Biomechanically, this results in peak tibiofemoral contact pressures identical to a complete medial meniscectomy, accelerating osteoarthritis.

Question 1382

Topic: 1. General Principles & Basic Science

During an inside-out repair of a posterior horn tear of the medial meniscus, which of the following neurologic structures is at greatest risk of iatrogenic injury?

. Common peroneal nerve
. Deep peroneal nerve
. Saphenous nerve
. Sural nerve
. Tibial nerve

Correct Answer & Explanation

. Saphenous nerve

Explanation

The saphenous nerve (specifically its infrapatellar branch and the main trunk) is at greatest risk during an inside-out repair of the medial meniscus. A posteromedial incision is utilized to protect this nerve and carefully retrieve the needles.

Question 1383

Topic: 1. General Principles & Basic Science

When performing a clinical examination for a suspected isolated flexor digitorum superficialis (FDS) laceration in the middle finger, the examiner holds the index, ring, and small fingers in full extension. What is the biomechanical rationale for this maneuver?

. It isolates the lumbrical muscles to prevent PIP extension
. It neutralizes the flexor digitorum profundus (FDP) because it shares a common muscle belly for digits 3 through 5
. It relaxes the extensor digitorum communis (EDC) to prevent antagonist action
. It tautens the transverse retinacular ligament to isolate FDS glide
. It restricts motion at the carpometacarpal (CMC) joints

Correct Answer & Explanation

. It neutralizes the flexor digitorum profundus (FDP) because it shares a common muscle belly for digits 3 through 5

Explanation

The FDP tendons to the middle, ring, and small fingers typically share a common muscle belly. Holding the adjacent digits in full extension anchors the FDP, allowing isolated testing of the FDS which has independent muscle bellies.

Question 1384

Topic: 1. General Principles & Basic Science

Following a Zone II flexor tendon repair, what is the primary source of nutrition for the tendon during the initial stages of healing?

. Direct vascular supply via the vincula longa and brevia
. Synovial fluid diffusion
. Vascular ingrowth from the paratenon
. Marrow elements from the adjacent phalanges
. Arterial supply from the lumbrical muscle belly

Correct Answer & Explanation

. Synovial fluid diffusion

Explanation

While the vincula provide some segmental vascularity, the primary source of nutrition for flexor tendons in Zone II (within the synovial sheath) is diffusion from synovial fluid. Motion enhances this diffusion, further supporting early active rehabilitation protocols.

Question 1385

Topic: 1. General Principles & Basic Science

A 55-year-old female sustains a medial meniscus posterior root tear while squatting. Biomechanically, how does this specific injury alter knee joint loading?

. It behaves biomechanically identical to a total medial meniscectomy
. It causes an isolated increase in shear forces without affecting contact area
. It equates to a 25% reduction in contact pressure
. It shifts peak contact pressures to the lateral compartment
. It causes primary valgus instability

Correct Answer & Explanation

. It behaves biomechanically identical to a total medial meniscectomy

Explanation

A posterior root tear of the medial meniscus disrupts the circumferential hoop stresses of the meniscus. Biomechanically, this results in extrusion of the meniscus and is equivalent to a total medial meniscectomy in terms of peak contact pressures and joint loading.

Question 1386

Topic: 1. General Principles & Basic Science

Which of the following best describes the vascular supply of the adult meniscus, which fundamentally determines the healing potential of surgical meniscal repairs?

. The central 75% is vascularized by branches of the middle genicular artery
. The peripheral 10-25% is vascularized by the medial and lateral genicular arteries
. The entire meniscus receives its vascularity exclusively from synovial fluid diffusion
. The anterior horn is entirely avascular, while the posterior horn is highly vascularized
. Vascularity strictly increases from the central zone to the innermost free edge

Correct Answer & Explanation

. The peripheral 10-25% is vascularized by the medial and lateral genicular arteries

Explanation

The adult meniscus is predominantly avascular, relying on synovial diffusion for nutrition in the inner zones. Only the peripheral 10-25% (the 'red-red' zone) has a direct blood supply from the perimeniscal capillary plexus formed by the genicular arteries, providing the best healing potential.

Question 1387

Topic: Surgical Anatomy & Approaches

When planning surgery for a severe, fixed positive sagittal imbalance in an adult deformity patient, which of the following osteotomies reliably provides the greatest amount of sagittal plane correction per level without complete segmental resection?

. Smith-Petersen osteotomy (SPO)
. Ponte osteotomy
. Pedicle subtraction osteotomy (PSO)
. Transforaminal lumbar interbody fusion (TLIF)
. Anterior longitudinal ligament (ALL) release

Correct Answer & Explanation

. Pedicle subtraction osteotomy (PSO)

Explanation

A Pedicle Subtraction Osteotomy (PSO) involves resection of the posterior elements and a wedge of the vertebral body, providing approximately 30 to 40 degrees of sagittal lordosis at a single level. SPOs and Ponte osteotomies typically provide only 10 degrees per level.

Question 1388

Topic: Surgical Anatomy & Approaches

An adult patient with severe fixed positive sagittal imbalance and previous long-segment lumbar fusion requires surgical correction. The surgeon plans a three-column osteotomy to achieve the necessary lordosis. Approximately how much lordotic correction can typically be obtained from a single-level pedicle subtraction osteotomy (PSO)?

. 5 to 10 degrees
. 15 to 20 degrees
. 30 to 40 degrees
. 45 to 55 degrees
. 60 to 70 degrees

Correct Answer & Explanation

. 30 to 40 degrees

Explanation

A single-level pedicle subtraction osteotomy (PSO) typically provides approximately 30 to 40 degrees of sagittal correction. This is in contrast to a Smith-Petersen osteotomy (SPO), which provides about 10 degrees of correction per level.

Question 1389

Topic: Surgical Anatomy & Approaches

Which surgical approach provides the best exposure for ORIF of a radial head fracture while minimizing the risk to the posterior interosseous nerve (PIN)?

. Posterolateral approach (Kocher approach)
. Anterior approach (Henry approach)
. Medial approach
. Direct posterior approach
. Lateral approach with anconeus muscle split

Correct Answer & Explanation

. Posterolateral approach (Kocher approach)

Explanation

Correct Answer: AThe posterolateral approach, also known as the Kocher approach, is widely preferred for radial head fractures. It uses the interval between the anconeus and extensor carpi ulnaris (ECU) muscles. This approach protects the posterior interosseous nerve (PIN), which typically lies within the supinator muscle, distal and anterior to the radial head. The anterior (Henry) approach risks the PIN more directly, and medial or direct posterior approaches are generally not suitable for radial head fixation. The lateral approach with anconeus muscle split is similar to Kocher but the key is the safe interval.

Question 1390

Topic: Surgical Anatomy & Approaches

Regarding the posterior interosseous nerve (PIN) during surgical approaches to the radial head, at what point is it most vulnerable?

. As it passes anterior to the humerus
. As it exits the radial tunnel
. As it pierces the superficial head of the supinator muscle
. Distal to the radial tuberosity
. Proximally, near the axilla

Correct Answer & Explanation

. As it pierces the superficial head of the supinator muscle

Explanation

Correct Answer: CThe posterior interosseous nerve (PIN) is a branch of the radial nerve. It becomes vulnerable as it enters and passes through the supinator muscle (often referred to as the Arcade of Frohse, the proximal edge of the superficial head of the supinator). During surgical approaches to the radial head, particularly if the dissection extends too far anterior or distal, the PIN can be at risk, especially where it pierces the superficial head of the supinator muscle within the radial tunnel. This is why the Kocher approach, staying posterior, is preferred.

Question 1391

Topic: 1. General Principles & Basic Science

A 35-year-old male lacerates the volar aspect of his index finger, resulting in a Zone II flexor tendon injury. A multi-strand core suture repair is planned. Which of the following factors has been shown biomechanically to be the most direct determinant of the initial tensile strength of the tendon repair?

. The caliber of the core suture material
. The number of core suture strands crossing the repair site
. The type of knot tied at the repair site
. The depth of the epitendinous suture purchase
. The integrity of the flexor tendon sheath repair

Correct Answer & Explanation

. The number of core suture strands crossing the repair site

Explanation

The initial tensile strength of a flexor tendon repair is most directly proportional to the number of core suture strands crossing the repair site. While adding an epitendinous suture can increase strength by up to 50%, the number of core strands remains the primary determinant.

Question 1392

Topic: 1. General Principles & Basic Science

During the repair of a Zone II flexor tendon laceration in a 28-year-old manual laborer, which of the following biomechanical factors most significantly increases the initial tensile strength of the repair?

. The caliber of the epitenon suture
. The use of a locking over a grasping suture technique
. The location of the knots (inside versus outside the repair)
. The number of core suture strands crossing the repair site
. The use of a braided nonabsorbable suture instead of a monofilament

Correct Answer & Explanation

. The number of core suture strands crossing the repair site

Explanation

The most important factor determining the initial strength of a flexor tendon repair is the number of core suture strands crossing the laceration site. Increasing the number of strands (e.g., from 2 to 4 or 6) significantly improves load-to-failure, permitting early active motion protocols.

Question 1393

Topic: Surgical Anatomy & Approaches

A 40-year-old male sustains a posterior wall acetabular fracture with an associated posterior hip dislocation. Which neurologic deficit is most likely to be observed on physical examination?

. Inability to extend the knee (femoral nerve)
. Inability to adduct the hip (obturator nerve)
. Inability to actively plantarflex the ankle (tibial division of the sciatic nerve)
. Inability to actively dorsiflex the ankle (peroneal division of the sciatic nerve)
. Numbness over the medial aspect of the calf (saphenous nerve)

Correct Answer & Explanation

. Inability to actively dorsiflex the ankle (peroneal division of the sciatic nerve)

Explanation

Posterior hip dislocations and posterior wall acetabular fractures most commonly injure the sciatic nerve. The peroneal division is more lateral, tightly tethered, and has larger fascicles with less connective tissue, making it much more susceptible to injury than the tibial division.

Question 1394

Topic: Biomechanics & Biomaterials

Which factor primarily determines the bending stiffness of an intramedullary nail construct?

. The material's yield strength.
. The number of interlocking screws.
. The cross-sectional area moment of inertia of the nail.
. The friction coefficient between the bone and nail.
. The length of the nail.

Correct Answer & Explanation

. The cross-sectional area moment of inertia of the nail.

Explanation

Correct Answer: CThe bending stiffness of a structural element, like an IM nail, is primarily determined by its Young's modulus (material stiffness) and its area moment of inertia (I). The area moment of inertia is highly dependent on the nail's diameter and cross-sectional geometry. A larger diameter nail, even with the same material, will have a significantly higher area moment of inertia and thus greater bending stiffness (Stiffness is proportional to E*I). The number of interlocking screws contributes to rotational and translational stability but does not directly dictate intrinsic bending stiffness of the nail itself. Yield strength relates to plastic deformation, and length influences deflection but not intrinsic stiffness.

Question 1395

Topic: Biology, Genetics & Bone Healing

A 45-year-old male sustains a comminuted tibia shaft fracture. Which of the following phases of secondary fracture healing is characterized by the initial formation of a soft callus, comprising predominantly fibrous tissue and cartilage?

. Inflammatory phase
. Granulation phase
. Soft callus phase
. Hard callus phase
. Remodeling phase

Correct Answer & Explanation

. Soft callus phase

Explanation

Correct Answer: CThe soft callus phase, or reparative phase, is indeed characterized by the proliferation of fibroblasts and chondroblasts that produce a fibrous matrix and fibrocartilage, forming the soft callus. The inflammatory phase involves hematoma formation and inflammatory cell influx. The granulation phase is early angiogenesis and fibrous tissue formation but not yet the mature soft callus. The hard callus phase involves calcification of the soft callus, and the remodeling phase is the conversion of woven to lamellar bone.

Question 1396

Topic: Biology, Genetics & Bone Healing

Which growth factor is considered the most potent osteoinductive agent and plays a crucial role in initiating mesenchymal stem cell differentiation into osteoblasts during fracture healing?

. Platelet-Derived Growth Factor (PDGF)
. Transforming Growth Factor-beta (TGF-beta)
. Fibroblast Growth Factor (FGF)
. Insulin-like Growth Factor (IGF)
. Bone Morphogenetic Proteins (BMPs)

Correct Answer & Explanation

. Bone Morphogenetic Proteins (BMPs)

Explanation

Correct Answer: EBone Morphogenetic Proteins (BMPs), particularly BMP-2 and BMP-7, are well-known for their potent osteoinductive properties, capable of inducing mesenchymal stem cell differentiation into osteoblasts and initiating endochondral and intramembranous bone formation. TGF-beta is also involved but primarily regulates cell proliferation, differentiation, and extracellular matrix production. PDGF and FGF are mitogenic and angiogenic, while IGF promotes cell proliferation and matrix synthesis.

Question 1397

Topic: Biology, Genetics & Bone Healing

Primary (direct) bone healing, as seen with rigid internal fixation, typically occurs under conditions of minimal interfragmentary strain. What is the characteristic cellular event that allows direct bone remodeling across the fracture gap without significant callus formation?

. Enchondral ossification
. Intramembranous ossification with extensive callus
. Formation of a fibrocartilaginous bridge
. Direct osteon remodeling by cutting cones
. Increased vascularity leading to hematoma resolution

Correct Answer & Explanation

. Direct osteon remodeling by cutting cones

Explanation

Correct Answer: DPrimary bone healing, occurring with rigid fixation and minimal gap (<0.1 mm) and strain (<2%), involves direct remodeling of the fracture site by cutting cones (Haversian systems). These cutting cones cross the fracture line, laying down new lamellar bone directly without an intermediate cartilaginous callus, a process akin to physiological bone remodeling. Enchondral ossification is characteristic of secondary healing, and extensive callus is also secondary healing.

Question 1398

Topic: Biology, Genetics & Bone Healing

A 70-year-old patient with a history of chronic glucocorticoid use for rheumatoid arthritis sustains a distal radius fracture. What is the primary mechanism by which chronic glucocorticoid use impairs fracture healing?

. Increased osteoclast activity leading to bone resorption
. Enhanced inflammatory response at the fracture site
. Inhibition of osteoblast proliferation and differentiation
. Reduced vascularization of the fracture hematoma
. Accelerated bone turnover leading to premature callus maturation

Correct Answer & Explanation

. Inhibition of osteoblast proliferation and differentiation

Explanation

Correct Answer: CChronic glucocorticoid use significantly impairs fracture healing primarily by inhibiting osteoblast proliferation and differentiation, reducing collagen synthesis, and promoting osteoblast apoptosis. They also interfere with local growth factor production and angiogenesis. While they can affect bone metabolism, their direct impact on osteoblast function is key to impaired healing.

Question 1399

Topic: Biology, Genetics & Bone Healing

Secondary fracture healing predominantly involves which of the following processes?

. Direct Haversian remodeling
. Intramembranous ossification only
. Endochondral ossification
. Creeping substitution without callus
. Fibrous union followed by direct bone formation

Correct Answer & Explanation

. Endochondral ossification

Explanation

Correct Answer: CSecondary fracture healing, characterized by the formation of a callus, primarily involves endochondral ossification, where cartilage is formed first and then replaced by bone, similar to long bone development. Intramembranous ossification also contributes at the periosteal surface, but enchondral ossification is central to the soft and hard callus phases. Direct Haversian remodeling is primary healing. Creeping substitution is seen in bone graft incorporation. Fibrous union is often a step towards nonunion if not ossified.

Question 1400

Topic: Biology, Genetics & Bone Healing

Wolff's Law describes the principle by which bone remodels in response to mechanical stresses. In the context of fracture healing, during which phase is Wolff's Law most actively demonstrated?

. Inflammatory phase
. Soft callus phase
. Hard callus phase
. Remodeling phase
. Consolidation phase

Correct Answer & Explanation

. Remodeling phase

Explanation

Correct Answer: DWolff's Law is most evident during the remodeling phase. After the hard callus has bridged the fracture and been mineralized, the woven bone of the callus is gradually replaced by stronger, more organized lamellar bone, and the medullary cavity is re-established, all in response to the functional loads and stresses placed upon it. The consolidation phase is part of the hard callus to early remodeling phase, but remodeling is the specific phase where the bone's architecture is refined according to stress.

Test Yourself

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

On this Page