-Figures 55a and 55b are the radiograph and CT scan of a 61-year-old woman who has had neck pain after being involved in a high-speed motor vehicle collision.Examination reveals normal strength and sensation in both upper and lower extremities, norma

C1-C2 posterior cervical fusion

A 77-year-old man with a history of mild renal insufficiency and atrial fibrillation on warfarin therapy is scheduled to undergo a left total hip arthroplasty. He previously underwent a right total hip arthroplasty with development of significant het

800 centigrey of radiation given to the periprosthetic soft tissues preoperatively on the morning of surgery

The fracture seen in Figure 1 is most likely associated with injury to what ligamentous structure?

Acromioclavicular (AC) ligaments

Figures 1 and 2 display the radiographs obtained from a woman who had volar plating of the distal radius 8 months earlier. Two days ago, she noticed she could not actively extend her thumb. What is the most appropriate treatment that would restore ac

Removal of hardware with tendon transfer

Orthopedics Hyperguide Review Quiz | Dr Hutaif

Question 1

Bone morphogenetic protein-2 (BMP-2) acts primarily through which of the following intracellular signaling pathways to promote osteoblastic differentiation?

Explanation

BMPs are members of the TGF-beta superfamily. They bind to serine/threonine kinase receptors, leading to the phosphorylation of SMAD 1, 5, and 8, which then complex with SMAD 4 to enter the nucleus and regulate transcription of osteogenic genes like Runx2.

Question 2

A 32-year-old male presents with a closed tibial shaft fracture. He develops severe pain out of proportion to his injury. Which of the following pressure measurements is the most reliable threshold for diagnosing acute compartment syndrome and indicating fasciotomy?

Explanation

The Delta P (Diastolic blood pressure - compartment pressure) of less than 30 mmHg is the most reliable indicator for acute compartment syndrome, as it accounts for the perfusion pressure threshold of the microcirculation, minimizing unnecessary fasciotomies compared to absolute pressure.

Question 3

A 13-year-old obese male presents with a slipped capital femoral epiphysis (SCFE). If the slip is determined to be unstable, the patient is at highest risk for which of the following complications?

Explanation

An unstable SCFE is defined clinically as the inability to bear weight even with crutches. It carries a significantly higher risk of osteonecrosis (avascular necrosis) of the femoral head, reportedly as high as 47%, compared to stable slips.

Question 4

During an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BTB) autograft, the surgeon must be cautious. Which of the following is the most common donor site morbidity associated with this specific graft choice?

Explanation

Anterior knee pain, especially with kneeling, is the most common donor site complication following a bone-patellar tendon-bone (BTB) autograft for ACL reconstruction. Patellar fracture and patellar tendon rupture are severe but less common.

Question 5

Which of the following genetic alterations is most classically associated with the development of conventional osteosarcoma?

Explanation

Conventional osteosarcoma is highly associated with mutations in the retinoblastoma (Rb) and p53 tumor suppressor genes. Patients with Li-Fraumeni syndrome (p53) and hereditary retinoblastoma both have a significantly increased risk of developing osteosarcoma.

Question 6

In Total Hip Arthroplasty (THA), which of the following bearing surface combinations offers the lowest volumetric wear rate?

Explanation

Ceramic-on-ceramic bearing surfaces provide the lowest volumetric wear rate among all THA bearing couples. However, they carry specific risks, including squeaking and catastrophic ceramic fracture.

Question 7

A 65-year-old male presents with deteriorating hand dexterity and difficulty with balance. Examination reveals a positive Hoffmann sign and hyperreflexia. Which of the following physical exam findings is also highly specific for cervical spondylotic myelopathy?

Explanation

The inverted brachioradialis (supinator) reflex is a highly specific sign of cervical myelopathy at the C5-C6 level. Striking the brachioradialis tendon produces paradoxical finger flexion due to an absent C6 reflex arc paired with hyperactive lower cervical segments.

Question 8

A laceration of both the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) in Zone II of the hand is classically known as 'no man/'s land'. The primary blood supply to these tendons within the digital sheath is provided by the:

Explanation

Within the digital flexor sheath (Zone II), the tendons are largely avascular but receive their segmental blood supply dorsally through the vincula tendinum (longa and brevia), which are delicate folds of mesotenon carrying vessels from the proper digital arteries.

Question 9

The Lisfranc ligament, critical for maintaining midfoot stability, primarily connects which two osseous structures?

Explanation

The Lisfranc ligament is an interosseous ligament that runs obliquely from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the strongest and most crucial ligament for the stability of the tarsometatarsal articulation.

Question 10

Articular cartilage is highly organized into distinct structural zones. Which zone is characterized by the highest concentration of collagen, the lowest concentration of proteoglycans, and chondrocytes arranged parallel to the joint surface?

Explanation

The superficial (tangential) zone of articular cartilage makes up 10-20% of the thickness. It features densely packed collagen fibers oriented parallel to the articular surface to resist shear forces, flattened chondrocytes, and the lowest proteoglycan content.

Question 11

To maximize mechanical advantage and effectively reduce pelvic volume in a hemodynamically unstable anterior-posterior compression (APC) pelvic ring injury, a pelvic binder should be centered precisely over which anatomical landmark?

Explanation

For optimal biomechanical reduction of a pelvic ring injury and to appropriately decrease intrapelvic volume to tamponade bleeding, a pelvic binder or sheet must be placed at the level of the greater trochanters. Placement higher over the iliac crests is less effective and may cause abdominal compression.

Question 12

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. Hyperflexion of the hips in the harness places the infant at highest risk for which of the following complications?

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to an iatrogenic femoral nerve palsy (manifesting as decreased active knee extension). Excessive abduction, on the other hand, increases the risk of avascular necrosis (AVN) of the femoral head.

Question 13

In a posterior-stabilized (PS) total knee arthroplasty, the interaction between the cam on the femoral component and the post on the tibial polyethylene insert is designed to substitute for the function of which native structure?

Explanation

In a posterior-stabilized (PS) TKA design, the posterior cruciate ligament (PCL) is sacrificed. The cam-and-post mechanism engages during knee flexion to enforce femoral rollback, effectively substituting for the function of the resected PCL.

Question 14

A 14-year-old male presents with a permeative lytic lesion in the diaphysis of the femur with an 'onion skin' periosteal reaction. Biopsy confirms Ewing sarcoma. Which of the following is the most common chromosomal translocation associated with this diagnosis?

Explanation

Ewing sarcoma is classically associated with the t(11;22)(q24;q12) translocation, resulting in the EWS-FLI1 fusion protein. t(X;18) is seen in synovial sarcoma; t(12;16) in myxoid liposarcoma; t(9;22) in CML (Philadelphia chromosome); t(2;13) in alveolar rhabdomyosarcoma.

Question 15

The healing potential of a meniscal tear is largely dependent on its blood supply. The perimeniscal capillary plexus, derived from the medial and lateral genicular arteries, supplies approximately what proportion of the adult meniscus?

Explanation

In adults, the blood supply to the meniscus is limited to the peripheral 10-30% (the 'red-red' zone). This makes peripheral tears much more amenable to repair and healing. The inner portions are avascular and receive nutrition via diffusion from synovial fluid.

Question 16

Neurogenic claudication secondary to lumbar spinal stenosis can often be differentiated from vascular claudication based on the patient's symptoms. Which of the following classically alleviates symptoms in neurogenic claudication but not vascular claudication?

Explanation

Neurogenic claudication is exacerbated by lumbar extension (standing, walking down an incline) and relieved by lumbar flexion (sitting, leaning over a shopping cart, or riding a stationary bicycle). Standing still relieves vascular claudication but typically aggravates neurogenic claudication due to sustained extension.

Question 17

A patient undergoing an open carpal tunnel release is at risk of iatrogenic injury to the recurrent motor branch of the median nerve. According to the Kaplan cardinal line, this branch typically arises from the median nerve at which of the following anatomical locations?

Explanation

The recurrent motor branch of the median nerve (the 'million dollar nerve') most commonly exhibits an extraligamentous, recurrent course, arising just distal to the transverse carpal ligament and curving back to innervate the thenar musculature.

Question 18

Acute Achilles tendon ruptures most frequently occur in a relatively hypovascular 'watershed' area. Where is this zone located relative to the calcaneal insertion?

Explanation

The Achilles tendon has a relative watershed zone of decreased vascularity approximately 2 to 6 cm proximal to its insertion on the calcaneus. This anatomic vulnerability makes it the most common site for spontaneous rupture.

Question 19

According to Perren's strain theory of fracture healing, primary (direct) bone healing without callus formation requires absolute stability. What is the maximum percentage of interfragmentary strain that still permits lamellar bone to form directly across the fracture gap?

Explanation

Perren's strain theory dictates that lamellar bone can only form under conditions of < 2% strain (absolute stability). Strains between 2% and 10% allow for secondary healing (callus/woven bone), while strains > 10% result in fibrous tissue or nonunion.

Question 20

A 25-year-old farm worker sustains a severe open tibia fracture with extensive soft tissue damage and heavy soil contamination (Gustilo-Anderson Grade IIIb). In addition to aggressive surgical debridement and standard cephalosporin/aminoglycoside coverage, which of the following antibiotics should ideally be added?

Explanation

In severe open fractures heavily contaminated with soil, feces, or organic matter (such as farm injuries), there is a significant risk of clostridial infection (gas gangrene). High-dose Penicillin is traditionally added to specifically cover for Clostridium species.

Question 21

On a load-deformation curve for bone, the point at which the material transitions from elastic to plastic deformation is known as what?

Explanation

The yield point marks the transition from elastic (reversible) to plastic (irreversible) deformation. Loading past this point causes permanent structural change before ultimate failure occurs.

Question 22

In which zone of articular cartilage are the collagen fibers oriented perpendicular to the joint surface and contain the highest concentration of proteoglycans?

Explanation

The deep (radial) zone has collagen fibers oriented perpendicular to the subchondral bone to resist compressive forces. It also contains the highest concentration of proteoglycans and the lowest water content.

Question 23

A surgeon utilizes demineralized bone matrix (DBM) during a spinal fusion. Which of the following best describes the inherent bone grafting properties of this material?

Explanation

DBM provides a collagen scaffold (osteoconductive) and contains active growth factors like bone morphogenetic proteins (osteoinductive). It is completely devoid of living cells, so it is not osteogenic.

Question 24

A patient sustains a peripheral nerve injury characterized by disruption of the axon and endoneurium, but with an intact perineurium and epineurium. What Sunderland classification corresponds to this injury?

Explanation

A third-degree Sunderland nerve injury involves loss of the axon and endoneurium while the perineurium and epineurium remain intact. Recovery is variable and often requires surgical intervention due to internal scarring.

Question 25

In a hemodynamically unstable polytrauma patient, damage control orthopedics (DCO) is indicated. Which systemic inflammatory marker is most commonly used to assess the resolution of the "second hit" phenomenon before definitive fracture fixation?

Explanation

IL-6 is a reliable marker of the systemic inflammatory response in polytrauma patients. Its level peaks early, and a return to baseline helps indicate a safe physiological window for definitive surgery.

Question 26

A 30-year-old female presents with knee pain. Radiographs reveal an expansile, purely lytic lesion in the distal femur extending to the subchondral bone without a sclerotic rim. Biopsy shows multinucleated giant cells. Which targeted medication is indicated for unresectable cases?

Explanation

Denosumab is a monoclonal antibody against RANKL used for unresectable giant cell tumors of bone. It inhibits the RANKL-mediated differentiation and activation of the neoplastic multinucleated giant cells.

Question 27

A surgeon plans to revise a failed nonunion utilizing a stainless steel plate and titanium screws. Which of the following forms of corrosion is most likely to occur due to mixing these metals?

Explanation

Galvanic corrosion occurs when two dissimilar metals are in contact within an electrolytic environment, like body fluid. The less noble metal acts as an anode and corrodes faster, which is why mixing stainless steel and titanium is generally contraindicated.

Question 28

A 72-year-old female with severe osteoporosis is started on teriparatide. Which of the following best describes the mechanism of action of this medication?

Explanation

Teriparatide is a recombinant human parathyroid hormone (PTH 1-34) analog. When administered intermittently, it acts as an anabolic agent by directly stimulating osteoblast activity and bone formation.

Question 29

A 65-year-old male on dabigatran for atrial fibrillation sustains a displaced femoral neck fracture. Which of the following agents is the specific reversal agent for this anticoagulant?

Explanation

Idarucizumab is a monoclonal antibody fragment that serves as the specific reversal agent for dabigatran, a direct thrombin inhibitor. Andexanet alfa is used to reverse direct Factor Xa inhibitors like rivaroxaban.

Question 30

Which of the following best describes the primary pathologic event in the initial phase of Paget disease of bone?

Explanation

Paget disease initially begins with an intense, localized osteoclastic (lytic) phase characterized by massive bone resorption. This is followed by a mixed phase and ultimately a sclerotic phase with disorganized woven bone.

Question 31

During a Smith-Petersen (anterior) approach to the hip, the superficial internervous plane is developed between the sartorius and the tensor fasciae latae. Which nerves supply these two muscles, respectively?

Explanation

The superficial plane of the anterior approach utilizes the internervous interval between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). This allows deep access to the hip joint without denervating the surrounding musculature.

Question 32

During the gait cycle, a patient demonstrates a 'steppage gait' with exaggerated hip and knee flexion during the swing phase. This abnormality is most classically associated with weakness of muscles innervated by which of the following nerves?

Explanation

A steppage gait compensates for foot drop, which results from weakness of the ankle dorsiflexors. These muscles, including the tibialis anterior, are innervated by the deep peroneal nerve.

Question 33

What is the correct sequence of the four histological transition zones at a direct tendon-to-bone insertion (enthesis)?

Explanation

A direct enthesis transitions through four distinct zones to gradually transfer mechanical stress. The sequence is tendon, uncalcified fibrocartilage, a basophilic tidemark, calcified fibrocartilage, and finally bone.

Question 34

A 4-year-old child presents with multiple fractures, blue sclerae, and dentinogenesis imperfecta. The underlying pathophysiology of this condition is primarily a defect in which of the following?

Explanation

Osteogenesis imperfecta is typically caused by mutations in the COL1A1 or COL1A2 genes, leading to defective Type I collagen. This widespread matrix defect results in brittle bones, blue sclerae, and hearing loss.

Question 35

An orthopedic study identifies patients with osteoarthritis and matched controls without the disease, then looks retrospectively at their lifetime history of high-impact sports participation. What type of study design is this?

Explanation

A case-control study starts by identifying patients with a disease (cases) and without a disease (controls), then looks backward at exposure histories. It is useful for identifying risk factors but cannot determine true incidence.

Question 36

During fluoroscopy, a surgeon steps back to a distance of 2 meters away from the radiation source instead of 1 meter. By what factor is the surgeon's radiation exposure reduced?

Explanation

According to the inverse square law, radiation exposure is inversely proportional to the square of the distance from the source. Doubling the distance (from 1m to 2m) reduces the exposure to one-fourth (1/2 squared) of the original dose.

Question 37

Which of the following phases of biofilm formation on an orthopedic implant is characterized by irreversible bacterial attachment and exopolysaccharide matrix production?

Explanation

Following initial reversible attachment, the aggregation phase involves bacteria firmly attaching and secreting an extracellular polymeric substance (EPS). This slime layer protects the bacteria from the host immune system and antibiotics.

Question 38

A 24-year-old sexually active male presents with an acute, atraumatic swollen knee. Arthrocentesis yields 65,000 WBCs/mcL with 90% polymorphonuclear cells. Pending culture results, what is the most appropriate empiric antibiotic therapy?

Explanation

In a young, sexually active patient with suspected septic arthritis, both Neisseria gonorrhoeae and Staphylococcus aureus must be covered. Empiric therapy with Vancomycin (for MRSA) and Ceftriaxone (for gonococcus) is the standard of care.

Question 39

In the pathogenesis of Rheumatoid Arthritis, which cell type is primarily responsible for the direct destruction of articular cartilage and bone within the pannus?

Explanation

While T-cells and macrophages drive the systemic inflammatory cascade, the fibroblast-like synoviocytes (FLS) in the pannus are primarily responsible for local joint destruction. They secrete matrix metalloproteinases (MMPs) and stimulate osteoclastogenesis via RANKL.

Question 40

A patient undergoes a Bier block using intravenous lidocaine for a distal radius fracture reduction. She suddenly develops tinnitus, perioral numbness, and a metallic taste. What is the most appropriate initial medical antidote for this severe toxicity?

Explanation

The patient is exhibiting signs of Local Anesthetic Systemic Toxicity (LAST). The primary specific treatment includes airway management and prompt administration of 20% intravenous lipid emulsion to sequester the lipophilic anesthetic molecules.

Question 41

Which zone of articular cartilage is primarily responsible for resisting shear stress and contains chondrocytes flattened parallel to the joint surface?

Explanation

The superficial zone contains tightly packed collagen fibers oriented parallel to the joint surface, providing primary resistance to shear forces. It also has the highest concentration of water and the lowest concentration of proteoglycans.

Question 42

According to Perren's strain theory, what is the maximum interfragmentary strain that permits primary bone healing (cutting cone remodeling) without intermediate callus formation?

Explanation

Primary bone healing occurs via cutting cones and requires absolute stability. Interfragmentary strain must be kept below 2%, as higher strain levels will stimulate secondary healing with callus formation or lead to nonunion.

Question 43

A 45-year-old farmer sustains a highly contaminated Grade IIIB open tibial shaft fracture after being trapped under a tractor. Which of the following intravenous antibiotic regimens is most appropriate upon presentation?

Explanation

Farm injuries with heavy soil contamination carry a high risk of Clostridium perfringens infection. The addition of high-dose Penicillin to a first-generation cephalosporin and an aminoglycoside is strongly recommended to cover this anaerobic threat.

Question 44

During an ilioinguinal approach for an acetabular fracture, severe hemorrhage occurs over the superior pubic ramus. This bleeding is most likely originating from an anastomosis between the obturator vessels and which of the following?

Explanation

The 'corona mortis' is a vascular anastomosis between the obturator and external iliac (or inferior epigastric) systems. It crosses the superior pubic ramus and is highly susceptible to iatrogenic injury during anterior pelvic approaches.

Question 45

In the management of Legg-Calve-Perthes disease, the Herring lateral pillar classification relies on radiographs taken during which stage of the disease?

Explanation

The Herring lateral pillar classification is assessed on an AP radiograph during the fragmentation stage of Legg-Calve-Perthes disease. It evaluates the height of the lateral pillar of the femoral head to determine prognosis and the need for intervention.

Question 46

A 60-year-old male presents with a destructive diaphyseal lesion in his humerus. Biopsy reveals sheets of plasma cells with eccentric nuclei and 'clock-face' chromatin. Which of the following lab findings is most consistently associated with his primary diagnosis?

Explanation

This patient has multiple myeloma, the most common primary bone malignancy in adults. Diagnosis relies on identifying a monoclonal gammopathy (M-spike) on SPEP or UPEP, along with a bone marrow biopsy confirming clonal plasma cells.

Question 47

Aseptic loosening following total hip arthroplasty is primarily mediated by a biologic cascade initiated by particulate wear debris. Which size range of polyethylene particles is most biologically active in stimulating macrophage-induced osteolysis?

Explanation

Polyethylene particles in the 0.1 to 1.0 micrometer range are easily phagocytosed by macrophages. This phagocytosis triggers the release of pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6) that activate osteoclasts and lead to periprosthetic osteolysis.

Question 48

Which of the following chromosomal translocations is most characteristic of Ewing sarcoma?

Explanation

Ewing sarcoma is classically associated with the t(11;22) translocation, resulting in the EWS-FLI1 fusion protein. This mutation acts as an aberrant transcription factor promoting oncogenesis.

Question 49

In the Ponseti method for correcting congenital talipes equinovarus (clubfoot), what is the first deformity that must be addressed during serial casting?

Explanation

The sequence of correction in the Ponseti method follows the acronym CAVE: Cavus, Adductus, Varus, then Equinus. Cavus is corrected first by supinating the forefoot to align it with the hindfoot.

Question 50

Increasing the radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) used in total joint arthroplasty has which of the following biomechanical effects?

Explanation

Highly cross-linked polyethylene significantly decreases volumetric wear but at the cost of decreasing fracture toughness, ductility, and fatigue resistance. This makes it more susceptible to rim fractures under certain loading conditions.

Question 51

A 25-year-old male sustains a zone 2 injury to Guyon's canal. Which of the following clinical deficits is most likely to be observed?

Explanation

Guyon's canal is divided into three zones. Zone 2 involves the deep motor branch of the ulnar nerve, so an injury here causes an isolated motor deficit of the intrinsic hand muscles without sensory loss.

Question 52

Which of the following is the primary mechanism of action of Teriparatide in the treatment of osteoporosis?

Explanation

Teriparatide is a recombinant human parathyroid hormone (PTH 1-34) analog. When administered intermittently, it exerts an anabolic effect by directly stimulating osteoblast activity and new bone formation.

Question 53

During a Latarjet procedure for recurrent anterior shoulder instability with 30% glenoid bone loss, the coracoid process is transferred to the anterior glenoid. Which structure attached to the transferred coracoid provides a dynamic "sling" effect?

Explanation

The Latarjet procedure transfers the coracoid process with the attached conjoined tendon (short head of the biceps and coracobrachialis). This tendon acts as a dynamic sling across the inferior subscapularis and anterior-inferior capsule when the arm is abducted and externally rotated.

Question 54

In treating developmental dysplasia of the hip (DDH) with a Pavlik harness, hyperflexion of the hips beyond 120 degrees places the infant at highest risk for which of the following complications?

Explanation

Hyperflexion of the hips in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to transient femoral nerve palsy. Conversely, excessive abduction is the primary risk factor for avascular necrosis.

Question 55

A 30-year-old male presents with an acute lateral compression type II (LC-II) pelvic ring injury. Which of the following ligaments is considered the strongest posterior stabilizer of the pelvic ring?

Explanation

The interosseous sacroiliac ligament is the strongest ligament in the body and serves as the primary stabilizer of the posterior pelvic ring. It effectively resists anteroposterior translation and extreme rotational forces.

Question 56

In articular cartilage, which layer is characterized by the highest concentration of collagen fibers arranged parallel to the joint surface to resist shear stress?

Explanation

The superficial (tangential) zone of articular cartilage has densely packed collagen fibrils oriented parallel to the articular surface. This unique arrangement primarily functions to resist high shear stresses during joint motion.

Question 57

A 45-year-old female presents with severe wrist pain after a fall. Radiographs show a displaced scaphoid waist fracture. The proximal pole is at highest risk for avascular necrosis due to a retrograde blood supply entering primarily through which surface?

Explanation

The scaphoid receives 70-80% of its blood supply from branches of the radial artery that enter distally at the dorsal ridge and course retrogradely. This places proximal pole fractures at a distinctively high risk for avascular necrosis.

Question 58

A 12-year-old boy presents with a pathologic fracture through a central, purely lytic lesion in the proximal humerus. Radiographs reveal the "fallen leaf" sign. What is the most likely composition of the fluid inside this lesion prior to the fracture?

Explanation

The clinical presentation and "fallen leaf" sign on radiographs are pathognomonic for a Unicameral Bone Cyst (UBC). Prior to a fracture, these benign cysts are typically filled with a clear or straw-colored serous fluid.

Question 59

When comparing titanium alloy (Ti-6Al-4V) to stainless steel (316L) for orthopedic implants, which biomechanical property of titanium provides a more favorable stress transfer to surrounding bone?

Explanation

Titanium alloy has a significantly lower modulus of elasticity compared to stainless steel, making it much closer to the modulus of cortical bone. This reduces stress shielding and promotes better load sharing with the surrounding bone.

Question 60

A patient undergoes a posterior-approach total hip arthroplasty. Postoperatively, the patient experiences recurrent posterior dislocations. Which of the following component malpositions is most likely responsible?

Explanation

Excessive retroversion of the acetabular component in a THA is a primary cause of posterior instability and dislocation. Proper anteversion (usually 15-20 degrees) and inclination (40-45 degrees) are crucial for dynamic stability.

Question 61

What is the primary function of the A2 and A4 pulleys in the flexor tendon system of the hand?

Explanation

The annular pulleys, specifically the critical A2 (proximal phalanx) and A4 (middle phalanx) pulleys, act as biomechanical fulcrums to keep the flexor tendons closely apposed to the bone. This prevents bowstringing and preserves mechanical efficiency.

Question 62

During a standard anterior (Smith-Petersen) approach to the hip, the internervous plane lies between muscles innervated by which of the following pairs of nerves?

Explanation

The Smith-Petersen approach utilizes the true internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve) superficially, and the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve) deep.

Question 63

In a polytrauma patient, which of the following parameters is considered an absolute indication for Damage Control Orthopedics (DCO) rather than Early Total Care (ETC)?

Explanation

Damage control orthopedics is indicated in physiologically unstable patients. Established parameters for instability include an arterial pH < 7.24, temperature < 34 C, and serum lactate > 2.5 mmol/L.

Question 64

In total hip arthroplasty, the biologic response to ultra-high molecular weight polyethylene (UHMWPE) wear debris is primarily mediated by the activation of which cell type?

Explanation

Polyethylene wear particles are phagocytosed by macrophages, which subsequently release pro-inflammatory cytokines such as TNF-alpha and IL-1. This cascade leads to osteoclast activation and periprosthetic osteolysis.

Question 65

A 65-year-old female sustains a subtrochanteric femur fracture after a minor fall. She has a 10-year history of alendronate use. What is the primary mechanism of action of this medication?

Explanation

Nitrogen-containing bisphosphonates like alendronate inhibit farnesyl pyrophosphate synthase within the mevalonate pathway. This disruption causes osteoclast apoptosis and prevents bone resorption.

Question 66

According to Perren's strain theory, what is the maximum amount of interfragmentary strain compatible with the formation of woven bone during secondary fracture healing?

Explanation

Perren's strain theory dictates that lamellar bone forms at <2% strain, and woven bone forms at 2-10% strain. Granulation tissue is required to tolerate high strains (up to 100%) before it differentiates into stiffer tissues.

Question 67

When utilizing a fluoroscopic C-arm during fracture fixation, which configuration minimizes radiation exposure to the surgeon's eyes and thyroid?

Explanation

Placing the X-ray source below the operating table and the image intensifier close to the patient above the table minimizes scatter radiation. Scatter radiation is most intense on the side of the X-ray tube.

Question 68

A 25-year-old male sustains a Gustilo-Anderson Type IIIB open tibia fracture. According to recent evidence-based guidelines, what is the most critical factor in reducing his risk of deep infection?

Explanation

The most critical factor in preventing infection in open fractures is the early administration of systemic antibiotics, ideally within 60 minutes. The strict "6-hour rule" for surgical debridement is no longer supported as an independent predictor of infection.

Question 69

A 60-year-old male presents with a pathologic proximal humerus fracture secondary to metastatic renal cell carcinoma. Preoperative planning for open reduction and internal fixation should strongly include which of the following?

Explanation

Metastases from renal cell carcinoma and thyroid carcinoma are highly vascular. Preoperative selective arterial embolization 24 to 48 hours prior to surgery significantly reduces massive intraoperative blood loss.

Question 70

A 70-year-old patient scheduled for elective total knee arthroplasty takes rivaroxaban for atrial fibrillation. What is the precise mechanism of action of this medication?

Explanation

Rivaroxaban and apixaban are direct Factor Xa inhibitors, which block the convergence point of the intrinsic and extrinsic coagulation pathways. Dabigatran, in contrast, is a direct thrombin (Factor IIa) inhibitor.

Question 71

A 68-year-old female taking denosumab for osteoporosis is planned for an elective lumbar fusion. What is the mechanism of action of her osteoporosis medication?

Explanation

Denosumab is a monoclonal antibody that binds directly to RANKL. This prevents RANKL from binding to the RANK receptor on osteoclasts, profoundly inhibiting osteoclast formation and bone resorption.

Question 72

During a drop jump exercise, the quadriceps muscle actively resists gravity to decelerate the body. What type of muscle contraction is occurring in the quadriceps?

Explanation

An eccentric contraction occurs when a muscle generates force while actively lengthening to decelerate a joint. Eccentric contractions generate the highest peak forces and are heavily implicated in muscle strain injuries.

Question 73

A patient with a closed humeral shaft fracture develops a radial nerve palsy. An EMG at 3 weeks shows fibrillation potentials in the brachioradialis but no voluntary motor unit action potentials. This indicates at least what degree of nerve injury according to Sunderland's classification?

Explanation

Fibrillation potentials indicate denervation resulting from Wallerian degeneration. This implies at least a second-degree injury (axonotmesis), differentiating it from a first-degree injury (neurapraxia) which involves only focal demyelination without axonal loss.

Question 74

Which of the following phases of creeping substitution occurs first following the placement of a cancellous bone autograft?

Explanation

The stages of creeping substitution for a cancellous graft occur in a specific order: inflammation, revascularization, osteoinduction/osteoconduction, and remodeling. Inflammation is the immediate first response driven by surgical trauma and hematoma formation.

Question 75

In normal adult articular cartilage, which zone is characterized by the highest concentration of water and the lowest concentration of proteoglycans?

Explanation

The superficial zone contains the highest water content (up to 80%) and collagen fibrils aligned parallel to the joint surface to resist shear stress. It also has the lowest concentration of proteoglycans compared to deeper zones.

Question 76

Bacterial biofilms make the eradication of prosthetic joint infections highly challenging. Which initial phase of biofilm development involves the reversible attachment of planktonic bacteria to the implant surface?

Explanation

Biofilm formation begins with adhesion, a reversible attachment of planktonic bacteria to a surface via van der Waals forces. This is followed by irreversible attachment, microcolony formation, maturation, and eventual dispersion.

Question 77

A surgeon incorrectly uses a stainless steel screw to secure a titanium alloy plate during fracture fixation. Which type of corrosion is most likely to occur at the screw-plate interface?

Explanation

Galvanic corrosion occurs when two electrochemically dissimilar metals are placed in direct contact within an electrolytic medium like bodily fluids. The less noble metal acts as an anode and undergoes accelerated corrosion.

Question 78

Tranexamic acid (TXA) is widely utilized in orthopedic surgery to reduce perioperative blood loss. What is its specific molecular mechanism of action?

Explanation

TXA is a synthetic analog of the amino acid lysine. It reversibly binds to the lysine-binding sites on plasminogen, preventing its activation to plasmin and effectively inhibiting fibrinolysis.

Question 79

A patient undergoing a minor orthopedic procedure under local anesthesia with bupivacaine acutely develops perioral numbness, tinnitus, and subsequent seizures. What is the most appropriate initial specific antidote?

Explanation

The patient is exhibiting signs of Local Anesthetic Systemic Toxicity (LAST). The specific and life-saving antidote is 20% intravenous lipid emulsion, which acts as a "lipid sink" to bind the highly lipophilic bupivacaine molecules.

Question 80

Which of the following vitamins is absolutely essential for the gamma-carboxylation of osteocalcin, allowing it to bind properly to calcium in the bone matrix?

Explanation

Vitamin K acts as an essential cofactor for the gamma-carboxylation of glutamic acid residues on osteocalcin. This post-translational modification is required for osteocalcin to effectively bind to calcium and hydroxyapatite.

Question 81

Ewing sarcoma is a highly aggressive bone tumor classically associated with which of the following chromosomal translocations?

Explanation

Ewing sarcoma is characterized by the t(11;22)(q24;q12) translocation in over 85% of cases, leading to the formation of the EWS-FLI1 fusion protein. Synovial sarcoma is associated with t(X;18).

Question 82

Demineralized bone matrix (DBM) products are commonly used in orthopedic bone grafting. Which of the following best describes the biologic properties of pure DBM?

Explanation

DBM provides a type I collagen scaffold (osteoconductive) and retains growth factors like BMPs (osteoinductive). Because the processing removes living cells, DBM possesses no osteogenic properties.

Self Assessment Examination Adult S Review | Dr Hutaif - ...

Orthopedics Hyperguide Review | Dr Hutaif General Ortho -...

Key Takeaway

Orthopedics Hyperguide Review | Dr Hutaif General Ortho -...

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