Menu

1. General Principles & Basic Science MCQs

Practice Set 212 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 4221

Topic: Surgical Anatomy & Approaches

An orthopedic surgeon is performing a direct anterior approach (DAA) to the hip. This approach utilizes the Smith-Petersen internervous plane. During the superficial dissection, which nerve is at greatest risk of iatrogenic injury, and between which two muscles is the interval developed?

. Femoral nerve; between Sartorius and Rectus Femoris
. Lateral femoral cutaneous nerve; between Tensor Fasciae Latae (TFL) and Sartorius
. Sciatic nerve; between Gluteus Maximus and Gluteus Medius
. Obturator nerve; between Pectineus and Adductor Longus
. Superior gluteal nerve; between Tensor Fasciae Latae (TFL) and Gluteus Medius

Correct Answer & Explanation

. Lateral femoral cutaneous nerve; between Tensor Fasciae Latae (TFL) and Sartorius

Explanation

The direct anterior approach (Smith-Petersen) utilizes an internervous plane between the Tensor Fasciae Latae (superior gluteal nerve) and the Sartorius (femoral nerve). The lateral femoral cutaneous nerve (LFCN) crosses over the sartorius and is highly vulnerable to traction or transection during the superficial exposure.

Question 4222

Topic: Surgical Anatomy & Approaches

A 38-year-old male is involved in a high-speed motor vehicle collision and sustains a Pipkin IV fracture-dislocation. Which of the following surgical approaches is most appropriate to adequately address both components of this specific injury pattern?

. Anterior (Smith-Petersen) approach
. Anterolateral (Watson-Jones) approach
. Posterior (Kocher-Langenbeck) approach
. Medial (Ludloff) approach
. Direct lateral (Hardinge) approach

Correct Answer & Explanation

. Posterior (Kocher-Langenbeck) approach

Explanation

A Pipkin IV injury consists of a femoral head fracture combined with an associated acetabular fracture, most commonly the posterior wall. The posterior (Kocher-Langenbeck) approach allows for visualization and fixation of both the posterior wall and the femoral head.

Question 4223

Topic: Biology, Genetics & Bone Healing

A 68-year-old female who has been taking alendronate for 12 years presents with an atraumatic subtrochanteric fracture characterized by lateral cortical thickening and a transverse fracture pattern. Which of the following best describes the pathophysiology underlying this atypical femoral fracture?

. Increased osteoblastic activity creating brittle woven bone
. Suppressed osteoclast activity leading to the accumulation of targeted microcracks
. Severe vitamin D deficiency causing inadequate mineralization of osteoid
. Hyperparathyroidism inducing rapid cortical tunneling
. Malignant infiltration of the endosteal cavity disrupting normal bone architecture

Correct Answer & Explanation

. Suppressed osteoclast activity leading to the accumulation of targeted microcracks

Explanation

Prolonged bisphosphonate use heavily suppresses osteoclast-mediated bone remodeling. This prevents the normal repair of daily microdamage, leading to the accumulation of microcracks and eventually culminating in a tension-sided stress fracture on the lateral cortex.

Question 4224

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach for an anterior column acetabulum fracture, massive bleeding is encountered near the superior pubic ramus. What vascular structure is most likely injured?

. Internal pudendal artery
. Inferior epigastric artery
. Corona mortis
. Superior gluteal artery
. Obturator artery main trunk

Correct Answer & Explanation

. Corona mortis

Explanation

The corona mortis is a vascular anastomosis between the external iliac (or inferior epigastric) and obturator vessels. It crosses the superior pubic ramus, typically located 4-6 cm from the pubic symphysis, making it highly susceptible to iatrogenic injury during anterior approaches to the acetabulum or pelvis.

Question 4225

Topic: Biology, Genetics & Bone Healing

A 65-year-old female presents with a low-energy subtrochanteric femur fracture with a transverse configuration, lateral cortical thickening, and a medial spike. She has been on alendronate for 8 years. What is the most appropriate management regarding her bone health medications?

. Discontinue alendronate and start high-dose calcium/vitamin D only
. Discontinue alendronate and start teriparatide
. Continue alendronate and add denosumab
. Discontinue alendronate and start zoledronic acid
. Switch alendronate to risedronate

Correct Answer & Explanation

. Discontinue alendronate and start teriparatide

Explanation

This presentation is pathognomonic for an atypical femur fracture (AFF) associated with long-term bisphosphonate use, which suppresses normal osteoclastic bone remodeling. Standard medical management includes discontinuing the bisphosphonate and initiating teriparatide, a recombinant parathyroid hormone that acts as an anabolic agent to stimulate bone formation and improve healing rates in AFFs.

Question 4226

Topic: Infection, Pharmacology & VTE

During an open reduction and internal fixation of a posteromedial tibial plateau fracture, the surgeon utilizes a posteromedial approach. Which structure represents the lateral interval boundary when accessing the posteromedial tibia?

. Medial collateral ligament
. Pes anserinus
. Medial head of the gastrocnemius
. Popliteal artery
. Semimembranosus tendon

Correct Answer & Explanation

. Medial head of the gastrocnemius

Explanation

The posteromedial approach to the proximal tibia utilizes the interval between the medial head of the gastrocnemius laterally and the pes anserinus medially. Retracting the medial head of the gastrocnemius laterally is critical as it acts as a soft-tissue shield to protect the popliteal neurovascular bundle.

Question 4227

Topic: Surgical Anatomy & Approaches

A surgeon is performing an open reduction and internal fixation of a proximal humerus fracture via a deltopectoral approach. To facilitate plate placement, the deltoid insertion is partially released. Which nerve is most at risk of injury when dissecting on the deep surface of the deltoid muscle, 5-7 cm distal to the lateral acromial edge?

. Musculocutaneous nerve
. Suprascapular nerve
. Axillary nerve
. Radial nerve
. Thoracodorsal nerve

Correct Answer & Explanation

. Axillary nerve

Explanation

The axillary nerve travels from posterior to anterior along the deep surface of the deltoid muscle, typically traversing 5 to 7 cm distal to the lateral edge of the acromion. It is highly vulnerable to traction or direct transection during extended lateral approaches to the proximal humerus or aggressive dissection beneath the deltoid belly.

Question 4228

Topic: 1. General Principles & Basic Science

A 28-year-old weightlifter felt a pop in his anterior chest while performing a heavy bench press. Examination reveals loss of the anterior axillary fold. MRI confirms an isolated rupture of the sternal head of the pectoralis major. Where does the sternal head normally insert relative to the clavicular head on the humerus?

. Proximal and deep
. Distal and deep
. Proximal and superficial
. Distal and superficial
. Directly anterior and parallel

Correct Answer & Explanation

. Proximal and deep

Explanation

The pectoralis major tendon twists 90 degrees before inserting on the lateral lip of the bicipital groove. This twist causes the sternal head to insert proximal and deep to the clavicular head.

Question 4229

Topic: Surgical Anatomy & Approaches

A 29-year-old unrestrained driver is involved in a motor vehicle collision. Radiographs demonstrate a posterior hip dislocation. Post-reduction, he exhibits a foot drop and inability to extend his great toe, with decreased sensation over the dorsum of the foot. Which specific neural structure is most likely injured?

. Tibial division of the sciatic nerve
. Peroneal division of the sciatic nerve
. Femoral nerve
. Superior gluteal nerve
. Deep peroneal nerve at the fibular neck

Correct Answer & Explanation

. Peroneal division of the sciatic nerve

Explanation

Posterior hip dislocations most commonly injure the sciatic nerve. The peroneal division is lateral, firmly tethered, and has less supportive connective tissue, making it significantly more susceptible to stretch injury than the tibial division.

Question 4230

Topic: 1. General Principles & Basic Science

A 45-year-old female sustains a posterior root tear of the medial meniscus. From a biomechanical perspective, what is the consequence of leaving this tear untreated?

. It is functionally equivalent to a total meniscectomy with loss of hoop stresses
. It causes a predominantly valgus thrust during ambulation
. It shifts the contact pressures entirely to the lateral compartment
. It isolatedly increases anterior tibial translation
. It leads to rapid isolated patellofemoral osteoarthritis

Correct Answer & Explanation

. It is functionally equivalent to a total meniscectomy with loss of hoop stresses

Explanation

A complete posterior root tear disrupts the circumferential continuity of the meniscus. This eliminates the meniscus's ability to convert axial loads into hoop stresses, rendering it biomechanically equivalent to a total meniscectomy.

Question 4231

Topic: 1. General Principles & Basic Science

In a two-stage flexor tendon reconstruction utilizing a silicone tendon implant (Hunter rod) for a chronic Zone 2 flexor digitorum profundus (FDP) laceration, what is the primary biological objective of the first stage of the procedure?

. To stimulate intrinsic tendon healing of the remaining tendon stumps
. To prevent contracture of the lumbrical muscles
. To form a vascularized pseudosheath capable of nourishing the future graft
. To provide immediate active flexion of the distal interphalangeal joint
. To permanently replace the FDP with a synthetic load-bearing conduit

Correct Answer & Explanation

. To form a vascularized pseudosheath capable of nourishing the future graft

Explanation

The primary purpose of the first stage of a two-stage flexor tendon reconstruction is the placement of a silicone spacer (Hunter rod) to induce the formation of a biological, highly vascularized pseudosheath. This pseudosheath provides a smooth, low-friction gliding surface and a rich vascular supply for the autologous tendon graft that will be inserted during the second stage (typically 3-4 months later).

Question 4232

Topic: 1. General Principles & Basic Science
During autologous nerve grafting for a 4 cm post-traumatic peripheral nerve gap, what is the primary cellular/structural contribution of the interposed donor nerve graft?
. It provides viable axons that directly bridge the gap.
. It secretes neurotoxins to prevent neuroma formation.
. It provides empty endoneurial tubes and viable Schwann cells to guide host axon regeneration.
. It acts purely as a mechanical scaffold with no live cellular contribution.
. It prevents Wallerian degeneration in the distal stump of the recipient nerve.

Correct Answer & Explanation

. It provides empty endoneurial tubes and viable Schwann cells to guide host axon regeneration.

Explanation

In an autologous nerve graft, the axons within the donor graft undergo Wallerian degeneration. However, the graft's basal lamina (endoneurial tubes) and viable Schwann cells remain intact. The Schwann cells multiply, clear debris, and form bands of Bรผngner, which produce neurotrophic factors. This provides both the biological environment and the physical pathways to guide the regenerating axons from the host's proximal stump into the distal stump.

Question 4233

Topic: Biology, Genetics & Bone Healing

When harvesting an autologous corticocancellous bone graft from the anterior iliac crest for the treatment of a structural atrophic nonunion, what is the primary biological property provided by the cancellous portion of the graft?

. Osteoconduction only
. Rigid mechanical stabilization
. Osteogenesis and osteoinduction
. Prevention of local infection
. Inhibition of osteoclast activity

Correct Answer & Explanation

. Osteogenesis and osteoinduction

Explanation

A corticocancellous bone graft provides multiple properties. The cortical portion primarily provides structural mechanical support and acts as an osteoconductive scaffold. The cancellous portion is rich in mesenchymal stem cells, osteoprogenitor cells, and osteoinductive proteins (like BMPs). Therefore, the cancellous bone primarily provides osteogenesis (living cells that form bone) and osteoinduction (factors that induce host cells to form bone).

Question 4234

Topic: 1. General Principles & Basic Science
In the Masquelet technique for reconstructing a 3 cm segmental bone defect of a metacarpal, a PMMA cement spacer is temporarily placed. During the second stage (typically 6-8 weeks later), a thick membrane surrounds the spacer. What is the primary biological characteristic of this induced membrane?
. It is an avascular sheath composed purely of dense type I collagen.
. It is rich in osteoclasts that resorb the PMMA cement.
. It is a highly vascularized pseudosynovial membrane rich in VEGF, TGF-beta1, and BMP-2.
. It functions primarily as an immune barrier to prevent graft rejection.
. It contains mature osteoblasts that immediately deposit woven bone without a graft.

Correct Answer & Explanation

. It is a highly vascularized pseudosynovial membrane rich in VEGF, TGF-beta1, and BMP-2.

Explanation

The induced membrane technique (Masquelet) relies on the foreign body reaction to the PMMA cement spacer. This reaction forms a highly vascularized, pseudosynovial membrane. Biologically, this membrane secretes high levels of crucial growth factors, including Vascular Endothelial Growth Factor (VEGF), Transforming Growth Factor-beta 1 (TGF-ฮฒ1), and Bone Morphogenetic Protein-2 (BMP-2), which provide a fertile, osteoinductive, and osteogenic environment for the subsequently placed cancellous bone graft.

Question 4235

Topic: Biology, Genetics & Bone Healing

Recombinant human bone morphogenetic proteins (rhBMPs) are utilized in orthopedics to promote bone healing. At the cellular level, through which type of cell surface receptor do BMPs primarily initiate their intracellular signaling cascade?

. G-protein coupled receptor
. Tyrosine kinase receptor
. Serine/threonine kinase receptor
. Ligand-gated ion channel
. Intracellular nuclear receptor

Correct Answer & Explanation

. Serine/threonine kinase receptor

Explanation

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-beta (TGF-beta) superfamily. They bind to specific type I and type II transmembrane receptors on the surface of mesenchymal stem cells. These receptors possess intrinsic serine/threonine kinase activity. Upon BMP binding, the type II receptor phosphorylates the type I receptor, which subsequently phosphorylates intracellular Smad proteins (Smad 1, 5, and 8), ultimately translocating to the nucleus to regulate transcription of osteogenic genes.

Question 4236

Topic: 1. General Principles & Basic Science

When utilizing structural cortical allografts for reconstructive procedures, how does the biological incorporation process critically differ from that of cortical autografts?

. Allografts incorporate rapidly via primary endochondral ossification
. Allografts rely on osteogenesis provided by live donor osteocytes
. Allografts exhibit creeping substitution that is typically limited to the outer 2 to 3 mm
. Allografts do not require osteoclastic resorption prior to new bone deposition
. Allografts are completely replaced by host bone within 12 months

Correct Answer & Explanation

. Allografts exhibit creeping substitution that is typically limited to the outer 2 to 3 mm

Explanation

Cortical bone autografts incorporate through a process of creeping substitution (osteoclast-mediated cutting cones followed by osteoblast bone deposition) that gradually replaces the graft. In contrast, structural cortical allografts elicit an immune response and lack live cells, leading to delayed and limited host revascularization. Creeping substitution in massive structural allografts is often incomplete and typically limited to the superficial peripheral margins (outer 2-3 mm) and the junctional interfaces. The bulk of the allograft remains necrotic indefinitely, which predisposes it to late fracture.

Question 4237

Topic: Biology, Genetics & Bone Healing

When evaluating the regenerative properties of various bone grafting materials, the term 'osteoinduction' refers specifically to which of the following processes?

. The provision of a physical three-dimensional scaffold for new bone growth
. The stimulation of undifferentiated mesenchymal stem cells to differentiate into osteoblasts
. The direct supply of living osteoprogenitor cells and osteoblasts to the graft site
. The promotion of neovascularization through the release of vascular endothelial growth factor (VEGF)
. The mechanical stabilization of a fracture site via osteoclastic cutting cones

Correct Answer & Explanation

. The stimulation of undifferentiated mesenchymal stem cells to differentiate into osteoblasts

Explanation

Bone grafting relies on three primary mechanisms. Osteoconduction provides a passive structural scaffold for cell migration and new bone formation. Osteoinduction is the active chemical process by which growth factors (such as Bone Morphogenetic Proteins - BMPs) stimulate host primitive mesenchymal stem cells to recruit, proliferate, and differentiate into mature bone-forming osteoblasts. Osteogenesis refers to the direct provision of live, viable osteoblasts and osteoprogenitor cells transferred within the graft material itself (e.g., fresh autograft).

Question 4238

Topic: Biology, Genetics & Bone Healing

Cancellous bone autograft is considered the 'gold standard' for filling cavitary bone defects due to its rapid incorporation and optimal biological properties. Compared to cortical autograft, what is the primary histological mechanism that accounts for the faster revascularization and incorporation of cancellous bone graft?

. Rapid osteoclastic tunneling and formation of cutting cones
. Direct angiogenesis and immediate osteoblast lining of the exposed trabecular surfaces
. Primary endochondral ossification mediated by chondrocytes
. Stimulation of an inflammatory foreign-body reaction
. Spontaneous dissolution of the mineral matrix

Correct Answer & Explanation

. Direct angiogenesis and immediate osteoblast lining of the exposed trabecular surfaces

Explanation

Cancellous autografts possess an open, porous trabecular architecture with large marrow spaces. This structure allows for rapid ingrowth of host capillaries (angiogenesis) directly into the graft. Once vascularized, host osteoblasts can immediately begin depositing new woven bone on the surfaces of the dead trabeculae (a process called appositional bone formation). In contrast, dense cortical autograft lacks these large open spaces and requires a much slower process of osteoclastic resorption (cutting cones) to create channels before osteoblasts can deposit new bone, making its incorporation significantly slower.

Question 4239

Topic: Biology, Genetics & Bone Healing

Following peripheral nerve injury and subsequent grafting, what is the primary role of Schwann cells during the process of Wallerian degeneration?

. Phagocytosis of myelin debris and formation of Bands of Bungner
. Producing collagen type I to recreate the epineurial sheath
. Suppressing macrophage infiltration at the injury site
. Generating action potentials directly across the non-vascularized graft
. Preventing random axonal sprouting and neuroma formation

Correct Answer & Explanation

. Phagocytosis of myelin debris and formation of Bands of Bungner

Explanation

During Wallerian degeneration, Schwann cells proliferate, assist in clearing myelin debris, and form longitudinal columns (Bands of Bungner) that guide regenerating axonal sprouts across the graft.

Question 4240

Topic: Biology, Genetics & Bone Healing

Demineralized bone matrix (DBM) is widely used in hand and upper extremity osseous reconstruction. Which of the following best describes the biologic properties of DBM?

. Osteogenic and osteoconductive
. Osteoinductive and osteoconductive
. Purely osteogenic
. Purely osteoconductive
. Osteogenic, osteoinductive, and osteoconductive

Correct Answer & Explanation

. Osteoinductive and osteoconductive

Explanation

DBM lacks viable cells, so it is not osteogenic. However, it contains bone morphogenetic proteins (BMPs) providing osteoinductive properties, and its collagenous matrix provides an osteoconductive scaffold.

Test Yourself

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

On this Page