A 38-year-old right-hand dominant carpenter sustained a Zone II flexor digitorum profundus (FDP) laceration to his left index finger 4 months ago, which was primarily repaired. He has diligently attended hand therapy, but his active range of motion (

Schedule flexor tendon tenolysis, emphasizing immediate post-operative mobilization.

A 55-year-old patient undergoes flexor tendon tenolysis for severe adhesions following a Zone II FDS and FDP repair. During the procedure, the surgeon meticulously dissects the tendons free from the surrounding synovial sheath and bone. The patient's

Extrinsic healing, involving fibroblasts from surrounding tissues laying down collagen fibers.

A 28-year-old musician presents 5 months after a Zone I FDP repair to his dominant ring finger. He complains of difficulty fully flexing his fingertip, significantly impacting his ability to play his instrument. On examination, his active DIP joint f

The significant difference between active and passive DIP joint flexion.

A surgeon is performing flexor tendon tenolysis on a patient with dense adhesions in Zone II. After incising the skin and subcutaneous tissue, the surgeon encounters significant scar tissue. Which of the following steps is MOST critical to perform ea

Systematically identify and meticulously dissect out the digital neurovascular bundles.

A 42-year-old patient undergoes flexor tendon tenolysis for a severely adherent FDP tendon in Zone II. During the procedure, after extensive adhesiolysis, the surgeon performs a dynamic assessment of gliding. Despite meticulous release, the tendon ap

Insert a silicone rod for a staged tendon reconstruction.

A 32-year-old patient undergoes flexor tendon tenolysis for severe adhesions in Zone II of the middle finger. The surgeon successfully releases all adhesions, ensuring full passive tendon gliding. Post-operatively, the patient is immediately started

Immediate, aggressive, and controlled active and passive motion to prevent re-adhesion.

A 68-year-old patient with a history of poorly controlled diabetes and active Complex Regional Pain Syndrome (CRPS) in her right hand presents with severe stiffness following a flexor tendon repair in Zone II. She is requesting flexor tendon tenolysi

Active Complex Regional Pain Syndrome (CRPS).

A 48-year-old patient undergoes flexor tendon tenolysis for persistent stiffness in Zone II of the ring finger. During the procedure, the surgeon encounters significant scarring, making identification of the FDS and FDP tendons challenging. After car

The A2 and A4 pulleys are crucial and must be preserved; any adhesions involving them should be carefully released from their surface.

A 60-year-old patient undergoes flexor tendon tenolysis for a long-standing flexion contracture of the PIP joint following a Zone II flexor tendon repair. Pre-operatively, the patient had a significant active flexion deficit, but also a 30-degree pas

An underlying fixed joint contracture of the PIP joint.

ABOS Part I Orthopaedic Board Review MCQs - Part 22163

Question 1

A 25-year-old male sustains a vertically oriented femoral neck fracture (Pauwels III) after a high-energy motor vehicle accident. Which of the following fixation constructs provides the most biomechanical stability against the vertical shear forces characteristic of this fracture pattern?

Explanation

Pauwels III fractures are highly unstable due to significant vertical shear forces. A fixed-angle device such as a sliding hip screw combined with a derotational screw provides superior biomechanical resistance to shear stress compared to multiple parallel cannulated screws.

Question 2

During endochondral ossification, the differentiation of mesenchymal stem cells into the osteoblast lineage is highly dependent on a specific master transcription factor. A mutation in the gene encoding this factor leads to cleidocranial dysplasia. Which of the following is the correct transcription factor?

Explanation

RUNX2 (also known as CBFA1) is the essential transcription factor for osteoblast differentiation. Genetic mutations or deficiency in RUNX2 result in cleidocranial dysplasia, characterized by absent or hypoplastic clavicles and delayed skull suture closure.

Question 3

A 12-year-old girl with a history of chronic renal failure and renal osteodystrophy presents with a unilateral slipped capital femoral epiphysis (SCFE). After successful in situ pinning of the symptomatic hip, what is the most appropriate management for the contralateral asymptomatic hip?

Explanation

Patients with underlying endocrine disorders or renal failure are at a significantly elevated risk for bilateral SCFE. Prophylactic pinning of the contralateral asymptomatic hip is strongly indicated in this population to prevent future displacement.

Question 4

During the physical examination of a patient suspected of having cervical spondylotic myelopathy, the examiner firmly flicks the distal phalanx of the middle finger, observing a reflex flexion of the thumb and index finger. This specific physical examination finding is known as:

Explanation

The Hoffmann sign is elicited by flicking the distal phalanx of the middle finger, leading to reflex flexion of the thumb and index finger. It indicates upper motor neuron dysfunction common in cervical myelopathy.

Question 5

A 30-year-old rock climber suffers a forced extension of his flexed ring finger, rupturing his flexor digitorum profundus (FDP) tendon directly at its insertion on the distal phalanx base. According to the standard flexor tendon injury classification, this corresponds to:

Explanation

Zone I of the flexor tendon system extends from the insertion of the flexor digitorum superficialis (FDS) to the insertion of the FDP on the distal phalanx. Injuries here isolate the FDP tendon.

Question 6

Which of the following anatomic variants is a well-documented intrinsic anatomic risk factor for a non-contact anterior cruciate ligament (ACL) tear?

Explanation

A narrow intercondylar notch (decreased notch width index) limits the space for the ACL and is a significant intrinsic risk factor for non-contact ACL injuries. Increased (not decreased) posterior tibial slope is another recognized risk factor.

Question 7

A 45-year-old highly active male undergoes a primary total hip arthroplasty with a ceramic-on-ceramic bearing surface. One year postoperatively, he complains of a loud, audible squeaking sound from the hip during deep flexion. Which component position is most highly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is closely associated with edge loading of the components. This often occurs when the acetabular cup is placed in excessive abduction (e.g., 60 degrees) or inadequate anteversion.

Question 8

A 15-year-old boy presents with progressive, worsening knee pain. Radiographs reveal a mixed lytic and sclerotic lesion in the distal femoral metaphysis with a sunburst periosteal reaction. Biopsy confirms high-grade osteosarcoma. Which tumor suppressor gene mutation is most strongly associated with the Li-Fraumeni syndrome variant of this disease?

Explanation

Li-Fraumeni syndrome is an autosomal dominant condition caused by a germline mutation in the TP53 tumor suppressor gene. It predisposes patients to multiple early-onset malignancies, including osteosarcoma.

Question 9

The Lisfranc ligament is a critical stabilizing structure of the midfoot that prevents lateral displacement of the lesser metatarsals. Which two osseous structures does the primary intra-articular component of this ligament connect?

Explanation

The Lisfranc ligament connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. There is no direct ligamentous connection between the first and second metatarsal bases.

Question 10

Aseptic loosening is the most common cause of failure in total joint arthroplasty and is driven by the biologic response to particulate wear debris. Which cell type is primarily responsible for phagocytosing these particles and subsequently releasing osteolytic cytokines like TNF-alpha and IL-1?

Explanation

Macrophages phagocytose particulate wear debris (such as polyethylene particles) and become activated. They release pro-inflammatory cytokines that stimulate osteoclast-mediated bone resorption, leading to aseptic loosening.

Question 11

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents report the infant has stopped kicking the affected leg. Physical examination reveals absent active knee extension. Which harness adjustment error most likely caused this complication?

Explanation

Excessive hip flexion in a Pavlik harness can lead to compression of the femoral nerve against the inguinal ligament, causing transient femoral nerve palsy. Excessive hip abduction is classically associated with avascular necrosis (AVN) of the femoral head.

Question 12

A 45-year-old male sustains a high-energy Schatzker IV (medial plateau) tibial plateau fracture. What is the classic mechanism of injury, and what is the essential biomechanical principle of internal fixation for this pattern?

Explanation

Schatzker IV fractures involve the medial tibial plateau and are typically caused by a high-energy varus force combined with axial loading. They inherently tend toward varus collapse and require a medial buttress plate for stable fixation.

Question 13

A 65-year-old male presents with bilateral leg cramping and heaviness that worsens after walking two blocks. He notes the pain is completely relieved within a few minutes if he sits down or leans forward over a shopping cart. Examination is normal at rest with palpable pulses. What is the most likely diagnosis?

Explanation

The patient's symptoms are classic for neurogenic claudication caused by lumbar spinal stenosis. Relief with lumbar flexion (sitting, leaning over a cart) occurs because flexion increases the cross-sectional area of the spinal canal and neural foramina.

Question 14

A 40-year-old female presents with aching volar forearm pain and paresthesias in the thumb, index, and middle fingers. The physician is trying to differentiate between carpal tunnel syndrome (CTS) and pronator syndrome. Which clinical finding strongly points toward pronator syndrome rather than CTS?

Explanation

The palmar cutaneous branch of the median nerve innervates the skin over the thenar eminence. It branches proximal to the carpal tunnel, so it is spared in CTS but affected in more proximal compressions like pronator syndrome.

Question 15

A 28-year-old professional volleyball player presents with insidious posterior shoulder pain and weakness. Physical exam reveals isolated weakness in external rotation with the arm at the side. The infraspinatus demonstrates profound atrophy, but the supraspinatus muscle bulk and strength are completely normal. Where is the most likely site of nerve compression?

Explanation

Compression of the suprascapular nerve at the spinoglenoid notch affects only the branch to the infraspinatus, causing isolated external rotation weakness. Compression at the suprascapular notch would affect both the supraspinatus and infraspinatus.

Question 16

During a primary total knee arthroplasty, a surgeon utilizes spacer blocks to evaluate the ligamentous gaps before making the final bony cuts. The knee is perfectly balanced and stable in 90 degrees of flexion, but it is too tight in full extension. Which of the following surgical steps is most appropriate to balance the gaps?

Explanation

Resecting more bone from the distal femur exclusively enlarges the extension gap without affecting the flexion gap. Resecting more proximal tibia would erroneously enlarge both the flexion and extension gaps equally.

Question 17

In a 35-year-old male with a displaced intracapsular femoral neck fracture, the primary blood supply to the adult femoral head is at risk. Which of the following arteries provides this primary supply?

Explanation

The medial femoral circumflex artery (MFCA) provides the primary blood supply to the adult femoral head via the lateral epiphyseal artery. Injury to this vessel significantly increases the risk of avascular necrosis following a femoral neck fracture.

Question 18

A 12-year-old obese boy presents with insidious onset of left knee pain and a limp. On physical exam, there is obligate external rotation of the left hip with passive hip flexion. What is the most likely diagnosis?

Explanation

Slipped capital femoral epiphysis (SCFE) classically presents in obese adolescents with hip or referred knee pain. Obligate external rotation during passive hip flexion is a hallmark physical exam finding due to the anterior and superior displacement of the metaphysis relative to the epiphysis.

Question 19

A patient with Li-Fraumeni syndrome develops an aggressive primary bone sarcoma. This syndrome is characterized by a germline mutation in which of the following genes?

Explanation

Li-Fraumeni syndrome is an autosomal dominant disorder caused by a germline mutation in the TP53 tumor suppressor gene. It places patients at high risk for multiple malignancies, most notably osteosarcoma, breast cancer, and soft tissue sarcomas.

Question 20

Which of the following is a recognized complication specifically associated with hard-on-hard ceramic-on-ceramic bearing surfaces in total hip arthroplasty?

Explanation

Squeaking is an auditory complication specific to ceramic-on-ceramic total hip arthroplasty, reported in up to 10-20% of cases. It may be related to component malposition, edge loading, or third-body wear.

Question 21

In an adult trauma patient, an atlantodens interval (ADI) greater than 3 mm on lateral cervical spine radiographs most specifically indicates incompetence of which stabilizing structure?

Explanation

The transverse ligament is the primary static stabilizer of the atlantoaxial joint. An ADI > 3 mm in an adult suggests transverse ligament rupture, while an ADI > 5 mm implies additional injury to the alar and apical ligaments.

Question 22

A Segond fracture observed on an AP radiograph of the knee is pathognomonic for an anterior cruciate ligament tear. This fracture represents a bony avulsion of the lateral capsule and which specific structure?

Explanation

A Segond fracture is a cortical avulsion off the proximal lateral tibia just distal to the joint line. It represents the avulsion of the anterolateral ligament (ALL) and the lateral capsule, strongly indicating an underlying ACL rupture.

Question 23

Which of the following physical examination maneuvers has the highest sensitivity for diagnosing carpal tunnel syndrome?

Explanation

The carpal compression test, or Durkan's test, involves applying direct manual pressure over the carpal tunnel for up to 30 seconds. It is widely considered the most sensitive provocative maneuver for diagnosing carpal tunnel syndrome.

Question 24

Current evidence suggests that managing acute Achilles tendon ruptures non-operatively with an early functional rehabilitation protocol, compared to surgical repair, results in:

Explanation

Recent high-quality studies show that early functional rehabilitation combined with non-operative management yields re-rupture rates similar to operative repair. However, surgical management carries a notably higher risk of wound healing complications and infections.

Question 25

Primary bone healing, characterized by Haversian remodeling and cutting cone formation without intermediate callus, requires which of the following mechanical environments?

Explanation

Primary bone healing requires a mechanical environment of absolute stability (strain < 2%) and virtually no gap between bone fragments. Under these conditions, healing occurs directly via osteoclastic cutting cones and osteoblastic bone formation without a cartilaginous intermediate.

Question 26

An open diaphyseal tibial fracture presents with a 12 cm laceration and extensive periosteal stripping. Following debridement, there is adequate local soft tissue to cover the bone. What is the appropriate Gustilo-Anderson classification?

Explanation

Gustilo-Anderson Type IIIA fractures involve extensive soft tissue damage, a wound > 10 cm, or high-energy mechanisms, but retain adequate local soft tissue coverage for the fractured bone. Type IIIB would require a rotational or free flap for coverage.

Question 27

When treating an infant for developmental dysplasia of the hip (DDH) using a Pavlik harness, prolonged hyperflexion of the hips places the patient at highest risk for which complication?

Explanation

Hyperflexion in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to transient femoral nerve palsy. In contrast, excessive abduction places the hip at higher risk for avascular necrosis of the femoral head.

Question 28

Flexor tendon injuries in the hand historically carry a poor prognosis when occurring in "Zone II" due to the tight confines of the fibro-osseous sheath. What is the proximal anatomical boundary of Zone II?

Explanation

Zone II, often called "no man's land," extends proximally from the proximal edge of the A1 pulley to the insertion of the flexor digitorum superficialis (FDS) at the middle phalanx. Both FDS and flexor digitorum profundus (FDP) tendons travel together within this tight sheath.

Question 29

During a primary total knee arthroplasty, placing the femoral component in excessive internal rotation relative to the epicondylar axis is most likely to result in which complication?

Explanation

Internal rotation of the femoral component relative to the transepicondylar axis shifts the trochlear groove medially. This increases the Q-angle dynamically and leads to lateral patellar maltracking and potential patellar instability.

Question 30

Which of the following intervertebral levels is the most common site for degenerative spondylolisthesis?

Explanation

Degenerative spondylolisthesis occurs most frequently at the L4-L5 level, largely due to the sagittal orientation of the facet joints at this level which provides less resistance to forward translation. Isthmic spondylolisthesis, conversely, is most common at L5-S1.

Question 31

Denosumab is highly effective in the medical management of surgically unsalvageable giant cell tumors of bone. What is the precise molecular target of this medication?

Explanation

Denosumab is a fully human monoclonal antibody that binds to RANKL. By inhibiting RANKL, it prevents the interaction with RANK receptors on osteoclast precursors, thereby halting osteoclastogenesis and giant cell tumor progression.

Question 32

The Remplissage procedure is utilized to manage significant engaging Hill-Sachs lesions following anterior shoulder dislocations. It involves capsulodesis and tenodesis of which muscle into the humeral head defect?

Explanation

The Remplissage procedure effectively converts an intra-articular engaging Hill-Sachs lesion into an extra-articular defect. It is performed by suturing the posterior capsule and the infraspinatus tendon into the bony defect of the posterolateral humeral head.

Question 33

Normal articular hyaline cartilage is composed primarily of water, proteoglycans, and a highly organized collagen framework. Which collagen type constitutes over 90% of this collagenous framework?

Explanation

Type II collagen forms 90-95% of the collagen network in healthy articular hyaline cartilage, providing tensile strength. Type I collagen is predominant in bone, tendon, and fibrocartilage (such as the meniscus).

Question 34

A "fleck sign" observed on an anteroposterior radiograph of a trauma patient's foot is highly suggestive of a Lisfranc injury. This osseous fragment typically represents an avulsion from which anatomical location?

Explanation

The "fleck sign" represents a bony avulsion of the Lisfranc ligament. While the ligament spans from the lateral aspect of the medial cuneiform to the medial base of the second metatarsal, the avulsion fracture almost universally occurs at the medial base of the second metatarsal.

Question 35

Due to its tenuous retrograde vascularity, the proximal pole of the scaphoid is highly susceptible to avascular necrosis after fracture. The primary blood supply to the proximal pole enters via vessels located at which anatomical landmark?

Explanation

The dorsal carpal branch of the radial artery provides the dominant blood supply to the scaphoid, accounting for 70-80% of its perfusion. These vessels enter at the dorsal ridge and supply the bone in a retrograde fashion toward the proximal pole.

Question 36

In an awake patient, what is clinically recognized as the earliest and most sensitive physical exam finding indicative of evolving acute compartment syndrome?

Explanation

Pain out of proportion to the injury, specifically exacerbated by passive stretch of the muscles traversing the affected compartment, is the earliest and most sensitive sign of acute compartment syndrome. Pulselessness and paralysis are late, ominous findings indicating irreversible damage.

Question 37

A 28-year-old male sustains a displaced basicervical femoral neck fracture. He undergoes closed reduction and internal fixation with three cancellous screws. Which of the following factors is most predictive of osteonecrosis of the femoral head in this patient?

Explanation

The initial degree of fracture displacement is the most significant prognostic factor for the development of osteonecrosis in young patients with femoral neck fractures. While anatomic reduction is critical to minimize nonunion risk, the initial vascular insult dictated by displacement primarily drives osteonecrosis.

Question 38

A 12-year-old obese male presents with a 3-week history of left knee pain and a limp. Examination reveals obligate external rotation of the hip during flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). During in situ pinning with a single screw, what is the ideal screw placement?

Explanation

The ideal screw position for a SCFE is in the center-center of the epiphysis on both AP and lateral radiographs, stopping roughly 5 mm short of the subchondral bone. This placement maximizes stability while minimizing the risk of joint penetration and subsequent chondrolysis.

Question 39

A 65-year-old female presents with progressive clumsiness in her hands and difficulty walking. Examination shows a positive Hoffmann sign bilaterally and hyperreflexia. MRI shows severe cervical stenosis at C4-C5 and C5-C6 with T2 signal change in the cord. Which physical exam finding is most specific for cervical myelopathy?

Explanation

The finger escape sign, or Wartenberg sign of the ulnar digits, alongside Hoffmann sign and inverted radial reflex, are upper motor neuron signs highly indicative of cervical myelopathy. The Spurling test evaluates cervical radiculopathy, not myelopathy.

Question 40

A 68-year-old female experiences recurrent posterior dislocations of her total hip arthroplasty. Revision surgery is planned. Radiographs and intraoperative evaluation reveal the acetabular component is well-fixed but retroverted. What is the most appropriate surgical management?

Explanation

In the setting of recurrent posterior instability driven by a malpositioned (retroverted) acetabular component, the definitive treatment is revision of the cup to correct the version. Using a constrained liner in a severely malpositioned cup leads to early failure and mechanical impingement.

Question 41

A 22-year-old female undergoes ACL reconstruction with a bone-patellar tendon-bone autograft. Six months postoperatively, she complains of anterior knee pain and difficulty ascending stairs. Exam shows a 10-degree extension deficit. What is the most likely cause of her extension deficit?

Explanation

A tibial tunnel placed too anteriorly can cause graft impingement against the intercondylar roof during extension, leading to an extension deficit and anterior knee pain. Conversely, a femoral tunnel placed too anteriorly typically results in increased graft tension during flexion, causing a flexion deficit.

Question 42

Following a Zone II flexor digitorum profundus (FDP) repair, what biomechanical property is most enhanced by adding an epitendinous suture to the core suture?

Explanation

The addition of a peripheral epitendinous suture significantly increases the ultimate breaking strength of the tendon repair and reduces gap formation. While it helps to smooth the repair site and minimally decreases gliding resistance, its primary mechanical advantage is a major increase in construct strength.

Question 43

A 35-year-old female presents with progressive knee pain. Radiographs reveal an eccentric, lytic lesion in the distal femoral epiphysis extending to the subchondral bone, with no sclerotic margin. Biopsy shows multinucleated giant cells and mononuclear stromal cells. What is the standard initial surgical treatment?

Explanation

Giant cell tumor of bone is typically treated with extended intralesional curettage using high-speed burrs and adjuvants (like phenol or argon beam) followed by packing with PMMA. Wide resection is generally reserved for massive joint destruction or recurrent, aggressive lesions.

Question 44

A 24-year-old sustains a Lisfranc fracture-dislocation with lateral displacement of the 2nd through 5th metatarsals. Which structure is the primary stabilizing ligament of the normal Lisfranc joint complex?

Explanation

The Lisfranc ligament is the strongest and primary stabilizer of the midfoot, traveling from the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. There is no direct transverse ligamentous connection between the bases of the first and second metatarsals.

Question 45

Which type of bone healing occurs primarily under conditions of absolute stability, such as following open reduction and internal fixation with a compression plate?

Explanation

Absolute stability with a strain of less than 2%, typically achieved with compression plating, allows for primary bone healing. This occurs via direct Haversian remodeling across the fracture site without the formation of an intermediate fracture callus.

Question 46

A 72-year-old male presents 4 weeks after a total knee arthroplasty with acute onset of severe knee pain, erythema, and swelling. Aspiration yields a synovial fluid white blood cell count of 45,000 cells/mcL with 92% neutrophils. What is the most appropriate management?

Explanation

For an acute periprosthetic joint infection occurring within 4 weeks of the index procedure, open debridement, antibiotics, and implant retention (DAIR) with a modular polyethylene exchange is the standard of care. Two-stage revision is indicated for chronic infections.

Question 47

A 4-month-old female infant is diagnosed with developmental dysplasia of the hip (DDH). Ultrasound confirms a dislocated left hip that is reducible. What is the most appropriate initial treatment?

Explanation

The Pavlik harness is the gold standard initial treatment for reducible DDH in infants up to 6 months of age. It dynamically maintains the hip in flexion and mild abduction, promoting spontaneous deepening of the acetabulum.

Question 48

A 45-year-old male sustains a Schatzker VI tibial plateau fracture. Which of the following complications is most specifically associated with this fracture pattern due to its high-energy mechanism?

Explanation

Schatzker VI tibial plateau fractures involve metaphyseal-diaphyseal dissociation and are caused by high-energy crush mechanisms, placing patients at an exceptionally high risk for acute compartment syndrome. Careful and repeated assessment of the compartments is mandatory.

Question 49

A 70-year-old male with neurogenic claudication secondary to lumbar spinal stenosis is scheduled for decompression. Which ligament hypertrophies and contributes significantly to the dorsal compression of the thecal sac in this condition?

Explanation

The ligamentum flavum typically hypertrophies and buckles into the spinal canal, especially in extension, contributing significantly to the dorsal compression of the thecal sac and nerve roots in degenerative lumbar stenosis.

Question 50

A 55-year-old male undergoes arthroscopic evaluation of a massive rotator cuff tear involving the supraspinatus and infraspinatus. Preoperatively, he exhibited a positive 'horn blower's' sign. Which muscle is primarily deficient?

Explanation

The horn blower's sign indicates weakness of external rotation with the arm abducted to 90 degrees and specifically evaluates the integrity of the teres minor. A positive sign suggests teres minor deficiency or profound fatty infiltration.

Question 51

When evaluating the mechanical properties of an orthopedic implant material, the 'yield point' on a stress-strain curve represents what phenomenon?

Explanation

The yield point on a stress-strain curve marks the end of the elastic region and the beginning of the plastic region. Beyond this point, the material will no longer return to its original shape when the load is removed, representing permanent deformation.

Question 52

A 30-year-old male sustains a closed tibia fracture and develops suspected acute compartment syndrome. His blood pressure is 120/80 mmHg. Intracompartmental pressure testing is performed. At what pressure threshold is a four-compartment fasciotomy clearly indicated?

Explanation

The most reliable indicator for fasciotomy is the Delta P (diastolic blood pressure minus intracompartmental pressure). A Delta P of less than 30 mmHg represents inadequate tissue perfusion and is the accepted threshold indicating the need for emergent fasciotomy.

Question 53

In the Ponseti method for correcting idiopathic clubfoot, what is the correct sequence of deformity correction?

Explanation

The Ponseti method dictates sequential correction following the acronym CAVE: Cavus (by elevating the first ray), Adductus, Varus, and finally Equinus. Attempting to correct equinus before the other components often requires an Achilles tenotomy and risks causing a rocker-bottom deformity.

Question 54

A 45-year-old pregnant female at 32 weeks gestation presents with severe, bilateral carpal tunnel syndrome that is unresponsive to nighttime splinting and causes significant sleep deprivation. What is the most appropriate next step in management?

Explanation

In a pregnant patient with carpal tunnel syndrome failing conservative management like splinting, a local corticosteroid injection is the most appropriate and safe next step. Surgical release is generally deferred as symptoms typically resolve rapidly after delivery.

Question 55

A 6-year-old boy presents with a completely displaced, extension-type Gartland III supracondylar humerus fracture. Which of the following neurologic deficits is most commonly associated with this specific injury pattern?

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. It is typically assessed by asking the patient to make an "OK" sign to test the flexor pollicis longus and flexor digitorum profundus to the index finger.

Question 56

A 25-year-old man sustains a Pauwels type III femoral neck fracture. Biomechanically, what is the primary force that fixation constructs must overcome to prevent failure in this specific fracture pattern?

Explanation

Pauwels type III femoral neck fractures have a fracture angle greater than 50 degrees from the horizontal. This vertical orientation subjects the fracture site primarily to high shear forces, which increases the risk of varus collapse and nonunion.

Question 57

A 14-year-old boy is diagnosed with a destructive diaphyseal bone lesion with an "onion skin" periosteal reaction. Cytogenetic analysis reveals a t(11;22) chromosomal translocation. Which fusion protein is characteristic of this tumor?

Explanation

The clinical picture describes Ewing sarcoma, characterized by the t(11;22) translocation. This specific genetic aberration results in the EWS-FLI1 fusion protein, which acts as an aberrant transcription factor.

Question 58

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip. The mother reports the infant has stopped kicking the left knee. What is the most likely cause of this complication?

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness when the hips are placed in excessive flexion. The treatment is to temporarily loosen the anterior straps or remove the harness until nerve function recovers.

Question 59

A 32-year-old man is admitted with a closed tibia fracture. Which of the following objective measurements is most indicative of acute compartment syndrome?

Explanation

Acute compartment syndrome is defined by a delta P (diastolic blood pressure minus intra-compartmental pressure) of less than or equal to 30 mmHg. This objective measurement is more reliable than absolute compartment pressures alone.

Question 60

In flexor tendon repair of the hand, which anatomical landmarks define the proximal and distal borders of "Zone II"?

Explanation

Zone II (historically called "No Man's Land") extends from the distal palmar crease proximally to the insertion of the flexor digitorum superficialis distally. It is notorious for poor clinical outcomes due to both FDS and FDP tendons gliding within the same tight fibro-osseous sheath.

Question 61

A 22-year-old football player sustains a midfoot injury. Radiographs show a "fleck sign" in the first intermetatarsal space. The disrupted ligament primarily connects which two anatomical structures?

Explanation

The Lisfranc ligament is an interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. The "fleck sign" represents a bony avulsion of this ligament.

Question 62

A 35-year-old woman with recurrent Giant Cell Tumor of the distal radius is treated with Denosumab. What is the precise mechanism of action of this medication?

Explanation

Denosumab is a monoclonal antibody that specifically binds to and inhibits RANKL. This prevents the interaction between RANKL and RANK on osteoclast precursors, thereby inhibiting osteoclast-mediated bone destruction characteristic of giant cell tumors.

Question 63

An obese 12-year-old boy presents with left groin pain and a limp. On physical examination, as the affected hip is passively flexed, it demonstrates an obligatory motion. Which obligatory motion is classic for this condition?

Explanation

The patient has a Slipped Capital Femoral Epiphysis (SCFE). The classic physical exam finding is obligatory external rotation of the thigh as the hip is passively flexed.

Question 64

A 24-year-old man sustains a proximal pole scaphoid fracture. The risk of avascular necrosis is high due to the retrograde blood supply of the scaphoid. Which artery is the primary source of this blood supply?

Explanation

The scaphoid receives its primary blood supply from the dorsal carpal branch of the radial artery, which enters distally and flows proximally (retrograde). This anatomical quirk explains the high rate of nonunion and avascular necrosis in proximal pole fractures.

Question 65

A trauma patient presents with an anteroposterior compression (APC) type III pelvic ring injury. A circumferential pelvic binder is applied. For maximum mechanical efficacy, the binder should be centered over which anatomic landmark?

Explanation

To optimally reduce pelvic volume and control hemorrhage in open-book pelvic fractures, a pelvic binder or sheet must be centered directly over the greater trochanters. Placement higher over the iliac crests is less effective and may paradoxically widen the pelvis.

Question 66

A 65-year-old woman develops catching and popping in her knee 1 year after a Total Knee Arthroplasty (TKA). She undergoes arthroscopy which reveals a fibrosynovial nodule. This complication is most uniquely associated with which TKA design?

Explanation

Patellar clunk syndrome is classically associated with posterior-stabilized (PS) TKA designs. It is caused by a fibrosynovial nodule forming at the superior pole of the patella, which catches in the intercondylar box of the femoral component during knee extension.

Question 67

A 55-year-old diabetic patient presents with a swollen, erythematous, but painless foot. Radiographs show extensive bone fragmentation, joint subluxation, and debris. According to the Eichenholtz classification for Charcot arthropathy, which stage does this represent?

Explanation

Eichenholtz Stage 1 (Developmental/Fragmentation) of Charcot arthropathy is characterized clinically by a hot, swollen foot and radiographically by bone fragmentation, joint subluxation, and debris. Stage 2 is coalescence, and Stage 3 is consolidation.

Question 68

Articular cartilage is composed of multiple zones. Which zone contains the highest concentration of proteoglycans and the lowest concentration of water?

Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its collagen fibers are oriented perpendicularly to the articular surface to resist compressive forces.

Question 69

What process is most commonly used to eliminate free radicals in highly cross-linked polyethylene components used in total joint arthroplasty?

Explanation

After cross-linking via irradiation, free radicals are eliminated by either melting or annealing the polyethylene. This critical step prevents long-term oxidation and subsequent abrasive wear in vivo.

Question 70

In a 25-year-old patient with a Pauwels type III femoral neck fracture, which fixation construct provides the greatest biomechanical stability against vertical shear forces?

Explanation

Pauwels III fractures have a high vertical shear angle, leading to a high rate of fixation failure. Fixed-angle devices like a sliding hip screw combined with a derotational screw offer superior resistance to these shear forces compared to multiple cannulated screws.

Question 71

Which of the following is the strongest clinical predictor for the development of avascular necrosis (AVN) following a slipped capital femoral epiphysis (SCFE)?

Explanation

Clinical instability, defined as the inability to bear weight even with crutches, is the strongest predictor of AVN in SCFE. Unstable slips have an AVN rate approaching 20 to 50 percent, whereas stable slips have an AVN rate of nearly zero.

Question 72

Which of the following radiographic anatomical features is most strongly associated with an increased risk of primary anterior cruciate ligament (ACL) rupture in female athletes?

Explanation

An increased posterior tibial slope increases anterior tibial translation under axial load. This anatomical variant is a recognized independent risk factor for both primary and revision non-contact ACL injuries.

Question 73

A 32-year-old manual laborer presents with dorsal wrist pain. Radiographs reveal sclerosis and fragmentation of the lunate with carpal height collapse and a fixed scaphoid rotation (Lichtman Stage IIIB). What is the most appropriate surgical treatment?

Explanation

Lichtman Stage IIIB Kienbock disease is characterized by lunate collapse and fixed scaphoid rotation leading to carpal collapse. Joint leveling is contraindicated at this stage; salvage procedures like proximal row carpectomy or scaphocapitate fusion are indicated.

Question 74

During the evaluation of a 65-year-old male with cervical spondylotic myelopathy, the examiner flicks the distal phalanx of the middle finger, resulting in reflex flexion of the thumb and index finger. This physical examination finding indicates compression of which tract?

Explanation

The described test is Hoffmann sign, which indicates an upper motor neuron lesion. Cervical myelopathy primarily affects the descending corticospinal tracts, resulting in upper motor neuron signs such as hyperreflexia and a positive Hoffmann sign.

Question 75

A 72-year-old patient presents with a first-time posterior dislocation of a total hip arthroplasty performed 12 years ago. The patient had no prior instability. What is the most likely underlying cause of this late dislocation?

Explanation

Late dislocations (greater than 5 years post-op) in previously stable total hips are most commonly due to polyethylene wear. This wear causes loss of femoral offset and decreased soft-tissue tension, predisposing the hip to instability.

Orthopaedic Surgery Board Exam Review: ABOS Part I & AAOS OITE Prep Questions | Part 22210

ABOS Part I Orthopaedic Surgery Board Review & MCQ Practice | Part 22163

Key Takeaway

ABOS Part I Orthopaedic Surgery Board Review & MCQ Practice | Part 22163

Chapter Index