OITE & ABOS Orthopedic Exam Prep: Knee & Spine Part 22

Question 1

Which zone of articular cartilage has the highest concentration of proteoglycans, features collagen fibrils arranged perpendicular to the joint surface, and is primarily responsible for resisting compressive forces?

Explanation

The deep (radial) zone of articular cartilage is characterized by the highest concentration of proteoglycans and the lowest water content. Its collagen fibrils (primarily Type II) are arranged perpendicular to the articular surface, making this zone critical for resisting compressive loads.

Question 2

In a patient presenting with L4-L5 degenerative spondylolisthesis, which facet joint orientation is most strongly associated with the pathogenesis of this condition?

Explanation

Degenerative spondylolisthesis is most commonly associated with a sagittal orientation of the facet joints (facet tropism). Sagittally oriented facets are less capable of resisting anterior shear forces, leading to progressive slip over time.

Question 3

A 22-year-old sustains a longitudinal tear in the red-white zone of the medial meniscus. Which vessel provides the primary vascular supply to the peripheral capillary plexus of the medial meniscus?

Explanation

The menisci receive their primary blood supply from the medial and lateral genicular arteries. Specifically, the inferior and superior medial genicular arteries form the perimeniscal capillary plexus supplying the peripheral 10-30% (red zone) of the medial meniscus. The middle genicular artery supplies the cruciate ligaments (ACL/PCL).

Question 4

Which type of collagen acts as the primary cross-linking molecule between Type II collagen fibrils in articular cartilage, effectively linking the fibrils to the extracellular matrix and providing structural stability?

Explanation

Type IX collagen is a non-fibrillar collagen that covalently binds to the surface of Type II collagen fibrils. It acts as an essential cross-linking molecule that connects the fibril network to the surrounding proteoglycan extracellular matrix.

Question 5

A 65-year-old Asian male presents with progressive cervical myelopathy secondary to Ossification of the Posterior Longitudinal Ligament (OPLL). Which of the following radiographic parameters is most strongly associated with a poor clinical outcome if he is treated with a posterior cervical laminoplasty?

Explanation

The K-line is defined as a line connecting the midpoints of the spinal canal at C2 and C7 on a neutral lateral radiograph. A 'K-line negative' cervical spine means the OPLL mass crosses the K-line (often due to kyphosis or massive OPLL thickness). In K-line negative patients, the spinal cord fails to shift posteriorly after laminoplasty, leading to poor myelopathic recovery. These patients generally require an anterior approach or posterior decompression with instrumented fusion.

Question 6

During a posterior cruciate ligament (PCL) reconstruction, the surgeon aims to anatomically reconstruct the anterolateral (AL) bundle. What is the primary biomechanical function of the AL bundle?

Explanation

The PCL consists of the larger anterolateral (AL) bundle and the smaller posteromedial (PM) bundle. The AL bundle is tightest in flexion and is the primary restraint to posterior tibial translation. The PM bundle is tightest in extension.

Question 7

In the Lenke classification for adolescent idiopathic scoliosis (AIS), a structural proximal thoracic (PT) curve is defined by either a regional kyphosis (T2-T5) of at least +20 degrees, OR a side-bending Cobb angle of at least what magnitude?

Explanation

According to the Lenke classification system for AIS, a curve is considered structural if the Cobb angle fails to correct to less than 25 degrees on side-bending radiographs, OR if there is a regional kyphosis of at least +20 degrees.

Question 8

Which of the following correctly describes the cellular mechanism and biological environment of Matrix-induced Autologous Chondrocyte Implantation (MACI) compared to traditional first-generation ACI?

Explanation

MACI is a third-generation cartilage repair technique where autologous cultured chondrocytes are seeded onto a porcine-derived Type I/III collagen membrane. This eliminates the need for harvesting a periosteal flap (as used in 1st-generation ACI), thereby significantly reducing the risk of graft hypertrophy and allowing for less invasive or arthroscopic application.

Question 9

A patient demonstrates increased external rotation on the dial test at 30 degrees of knee flexion, but symmetrical external rotation at 90 degrees compared to the contralateral normal knee. Which structures are most likely injured?

Explanation

The dial test evaluates for posterolateral corner (PLC) and PCL injuries. Increased external rotation (>10 degrees compared to the normal side) only at 30 degrees of flexion indicates an isolated PLC injury (specifically the popliteus complex and fibular collateral ligament). If increased external rotation is present at both 30 and 90 degrees, it indicates a combined PLC and PCL injury.

Question 10

A 45-year-old male presents with acute urinary retention, saddle anesthesia, and bilateral lower extremity weakness secondary to a massive L4-L5 disc herniation. Regarding the surgical management of Cauda Equina Syndrome (CES), which clinical factor has the strongest correlation with the long-term recovery of bladder function?

Explanation

While time to decompression (ideally < 24-48 hours) is critical, numerous studies have shown that the pre-operative continence status (CES-Incomplete vs. CES-Retention) is the single most important prognostic indicator for urologic recovery. Patients who present with incomplete CES (intact sphincter tone/some voluntary control) have a significantly higher rate of full recovery compared to those presenting in painless urinary retention (CES-R).

Question 11

On MRI, which finding has the highest specificity for indicating instability of an osteochondritis dissecans (OCD) lesion in a skeletally mature patient?

Explanation

A high T2-weighted signal line surrounding the OCD fragment indicates that synovial fluid has tracked behind the fragment into the subchondral bone, which strongly indicates lesion instability and a breach of the overlying articular cartilage. This is an indication for surgical stabilization in a skeletally mature patient.

Question 12

A 25-year-old male sustains a high-energy knee dislocation (KD-IV). Following closed reduction, his dorsalis pedis and posterior tibial pulses are palpable but asymmetric compared to the uninjured side. The Ankle-Brachial Index (ABI) is 0.85. What is the most appropriate next step in management?

Explanation

In the setting of a knee dislocation with an abnormal ABI (< 0.9) or asymmetric pulses, advanced imaging with CT angiography (CTA) is mandated to rule out a vascular intimal tear or occlusion. Hard signs of arterial injury (absent pulses, expanding hematoma, active pulsatile bleeding) would necessitate immediate open exploration, but an ABI of 0.85 with palpable pulses requires CTA first.

Question 13

In the Thoracolumbar Injury Classification and Severity (TLICS) score, how many points are assigned to a frank disruption of the posterior ligamentous complex (PLC), and what is the surgical implication if a patient's total score is 5?

Explanation

In the TLICS system, PLC disruption is assigned 3 points (suspected/indeterminate is 2 points, intact is 0). A total TLICS score of 4 can be treated operatively or nonoperatively (surgeon's preference), while a total score of >= 5 is an indication for surgical stabilization.

Question 14

In the early pathogenesis of osteoarthritis, which biochemical change occurs first in the articular cartilage extracellular matrix?

Explanation

The earliest biochemical change in osteoarthritis is the damage to the Type II collagen meshwork, which allows the hydrophilic proteoglycans to swell. This leads to an overall increase in water content and a relative decrease in proteoglycan concentration, resulting in decreased stiffness of the cartilage.

Question 15

A 14-year-old gymnast presents with 3 months of activity-related low back pain. Radiographs are normal. MRI of the lumbar spine reveals hyperintensity on STIR imaging in the L5 pars interarticularis bilaterally, without a visible fracture line on T1-weighted images. What is the most appropriate initial management?

Explanation

The patient has an acute stress reaction of the pars interarticularis (early spondylolysis) identified by edema on STIR MRI without a complete fracture. The initial management consists of cessation of offending activities (hyperextension) and bracing (TLSO) to allow the stress reaction to heal and prevent progression to a complete nonunion.

Question 16

During reconstruction of the Medial Patellofemoral Ligament (MPFL) for recurrent patellar instability, non-anatomic femoral tunnel placement is a common cause of failure. If the femoral tunnel is placed too proximal to the anatomic footprint (Schöttle's point), what biomechanical consequence will occur during knee range of motion?

Explanation

If the MPFL femoral tunnel is placed too proximally, the distance between the patellar attachment and the femoral attachment increases as the knee flexes. This results in an anisometry where the graft is excessively tight in flexion (causing increased medial patellofemoral contact pressures and loss of flexion) and loose in extension (failing to prevent lateral dislocation).

Question 17

Following a microfracture procedure for a 1.5 cm^2 symptomatic full-thickness chondral defect on the medial femoral condyle, what type of cartilage primarily fills the defect, and what is its major collagen component?

Explanation

Marrow stimulation techniques, such as microfracture, result in the formation of a 'super clot' that organizes into fibrocartilage. Fibrocartilage is primarily composed of Type I collagen, which is biomechanically inferior to the Type II collagen found in native hyaline cartilage.

Question 18

A 68-year-old man presents with bilateral leg pain when walking. Which of the following findings in his history or physical examination most strongly points to neurogenic claudication secondary to lumbar spinal stenosis rather than vascular claudication?

Explanation

Neurogenic claudication is classically exacerbated by lumbar extension (which decreases the central canal area) and relieved by lumbar flexion (sitting, leaning over a shopping cart), which increases the central canal and foraminal volume. Vascular claudication is consistently related to muscle work (a fixed walking distance) and is relieved by simply stopping and standing upright.

Question 19

Six months following a bone-patellar tendon-bone anterior cruciate ligament (ACL) reconstruction, a patient complains of a palpable clunk and pain at the anterior knee, along with a 15-degree lack of full terminal extension. MRI reveals a nodular mass in the intercondylar notch anterior to the ACL graft. What is the most likely diagnosis?

Explanation

A Cyclops lesion is a form of localized anterior arthrofibrosis consisting of a fibrovascular nodule that forms anterior to the ACL graft in the intercondylar notch. It acts as a mechanical block, classically causing an anterior clunk, pain, and loss of terminal extension.

Question 20

A 55-year-old male with a history of intravenous drug use presents with severe back pain, fever, and elevated ESR and CRP. MRI with gadolinium shows T1 hypointensity, T2 hyperintensity, and enhancement of the L3-L4 intervertebral disc and adjacent vertebral body endplates. Blood cultures are negative. What is the most appropriate next step to establish a microbiologic diagnosis before initiating long-term antibiotic therapy?

Explanation

In cases of suspected pyogenic vertebral osteomyelitis/discitis where blood cultures are negative and the patient is neurologically stable, a CT-guided percutaneous needle biopsy is the gold standard next step to identify the causative organism. Empirical antibiotics should be withheld until tissue cultures are obtained to ensure directed therapy, unless the patient is septic or neurologically compromised.

Question 21

During a posterior-stabilized (PS) total knee arthroplasty, trial reduction reveals the knee is symmetric and balanced in extension, but symmetrically tight in deep flexion. Which of the following is the most appropriate surgical adjustment to achieve a balanced knee?

Explanation

Symmetrical tightness in flexion with a balanced extension gap implies that the flexion gap is too small. Decreasing the anteroposterior (AP) dimension of the femoral component (downsizing the femur using anterior referencing) reduces the posterior condylar offset, thereby opening up the flexion gap without altering the extension gap. Recutting the distal femur or releasing the posterior capsule would primarily affect the extension gap, while downsizing the polyethylene insert would increase both the flexion and extension gaps.

Question 22

To achieve optimal postoperative sagittal balance in a patient undergoing surgical correction for adult lumbar degenerative scoliosis, the lumbar lordosis (LL) should be matched to the patient's pelvic incidence (PI). According to the Schwab criteria, what is the widely accepted target formula for this relationship?

Explanation

The SRS-Schwab adult spinal deformity classification identifies key radiographic sagittal parameters associated with health-related quality of life. The ideal target is a mismatch of less than 10 degrees between Pelvic Incidence (PI) and Lumbar Lordosis (LL), expressed as PI - LL < 10 degrees (or LL = PI ± 10 degrees). This restores harmonic sagittal alignment and minimizes the risk of adjacent segment disease and hardware failure.

Question 23

Which of the following characteristics best describes the deep (radial) zone of articular cartilage compared to the superficial zone?

Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its collagen fibers (primarily Type II) are arranged perpendicular to the articular surface to maximize resistance to compressive loads. In contrast, the superficial zone has the highest water content, lowest proteoglycan content, and collagen fibers parallel to the joint surface to resist shear forces.

Question 24

Biomechanical studies have demonstrated that an unrepaired complete radial tear of the posterior medial meniscus root alters knee joint contact pressures to a state most similar to which of the following conditions?

Explanation

A complete radial tear or avulsion of the posterior medial meniscus root completely disrupts the circumferential hoop stresses of the meniscus. Biomechanically, this renders the meniscus functionally incompetent, causing extrusion and increasing peak tibiofemoral contact pressures to levels equivalent to those seen after a total meniscectomy. This strongly predisposes the joint to rapid articular cartilage degeneration.

Question 25

In the Lenke classification system for adolescent idiopathic scoliosis (AIS), a minor curve is considered 'structural' and generally must be included in the fusion construct if it meets which of the following radiographic criteria?

Explanation

According to the Lenke classification for AIS, a minor curve is considered structural if it fails to correct to less than 25 degrees on a coronal side-bending radiograph (i.e., Cobb angle remains ≥ 25 degrees). A regional sagittal kyphosis of ≥ +20 degrees also defines a minor curve as structural.

Question 26

During the early pathogenesis of osteoarthritis, the degradation of the extracellular matrix is a critical event. Which of the following enzymes is considered the primary aggrecanase responsible for the initial cleavage of the aggrecan core protein?

Explanation

ADAMTS-4 and ADAMTS-5 (A Disintegrin and Metalloproteinase with Thrombospondin motifs) are the primary aggrecanases responsible for the early degradation of aggrecan in osteoarthritis. MMP-13 (Matrix Metalloproteinase 13) is the primary collagenase responsible for the degradation of Type II collagen, a process that typically follows aggrecan loss.

Question 27

A 24-year-old athlete sustains a direct blow to the anteromedial tibia. Physical examination reveals an abnormal Dial test with 15 degrees of increased external tibial rotation at 30 degrees of knee flexion, but symmetric rotation at 90 degrees compared to the uninjured side. This finding is highly specific for an isolated injury to which of the following structures?

Explanation

The Dial test evaluates for external rotation asymmetry. The posterolateral corner (PLC) is the primary restraint to external rotation at 30 degrees of flexion. At 90 degrees of flexion, the posterior cruciate ligament (PCL) becomes the primary restraint. Therefore, an increase of >10 degrees of external rotation at 30 degrees but not at 90 degrees indicates an isolated PLC injury. If rotation is increased at both 30 and 90 degrees, it indicates a combined PCL and PLC injury.

Question 28

A 35-year-old male sustains an L1 burst fracture. He is neurologically intact. MRI demonstrates an intact posterior ligamentous complex (PLC). According to the Thoracolumbar Injury Classification and Severity Score (TLICS), what is his total score and the generally recommended management?

Explanation

The TLICS system scores injuries based on morphology, neurologic status, and posterior ligamentous complex (PLC) integrity. A burst fracture morphology scores 2 points. Intact neurology scores 0 points. An intact PLC scores 0 points. The total score is 2. A TLICS score of ≤ 3 indicates nonoperative management, a score of 4 is surgeon discretion, and a score ≥ 5 indicates operative management.

Question 29

Matrix-induced Autologous Chondrocyte Implantation (MACI) has largely replaced first-generation ACI in many centers. Which of the following describes the primary procedural advantage of MACI over first-generation ACI?

Explanation

First-generation ACI required the harvesting and suturing of a periosteal patch over the defect to contain the liquid chondrocyte suspension, which was associated with prolonged operative time and a high rate of patch hypertrophy. MACI uses a porcine-derived collagen membrane seeded with cultured autologous chondrocytes, eliminating the need for a periosteal patch. It remains a two-stage procedure requiring in-vitro expansion.

Question 30

When drilling the femoral tunnel during a medial patellofemoral ligament (MPFL) reconstruction, identifying Schöttle's point is critical to ensure near-isometric graft behavior. On a strict lateral radiograph, where is this point located?

Explanation

Schöttle's point marks the radiographic femoral origin of the MPFL. It is located 1 mm anterior to a line extending the posterior femoral cortex, 2.5 mm distal to the posterior origin of the medial femoral condyle, and distinctly proximal to the level of the posterior aspect of Blumensaat's line. Placing the graft here avoids anisometry and abnormal patellofemoral tracking.

Question 31

Sorensen's criteria for the formal radiographic diagnosis of classic Scheuermann's kyphosis requires the presence of which of the following findings on a lateral spine radiograph?

Explanation

Classic Scheuermann's disease is characterized by rigid thoracic kyphosis. Sorensen's strict radiographic criteria for diagnosis require anterior wedging of ≥ 5 degrees in at least three consecutive vertebrae. Associated findings often include Schmorl's nodes and endplate irregularities, but the wedging parameter is the defining diagnostic criterion.

Question 32

Histological evaluation of the repair tissue one year following marrow stimulation (microfracture) for a full-thickness chondral defect of the medial femoral condyle will demonstrate a matrix composed predominantly of which type of collagen?

Explanation

Marrow stimulation techniques like microfracture rely on releasing marrow elements to form a 'superclot' over the cartilage defect. The resulting repair tissue differentiates into fibrocartilage, which is predominantly composed of Type I collagen. This tissue is mechanically inferior and less durable than native hyaline cartilage, which is predominantly Type II collagen.

Question 33

The anterior cruciate ligament (ACL) is composed of distinct anteromedial (AM) and posterolateral (PL) bundles. Which of the following statements regarding their biomechanical behavior is most accurate?

Explanation

The anteromedial (AM) bundle of the ACL is tight in flexion and is the primary restraint to anterior tibial translation at 90 degrees of knee flexion. Conversely, the posterolateral (PL) bundle is tight in extension and is primarily responsible for providing rotatory stability to the knee.

Question 34

According to the Wiltse classification of spondylolisthesis, a Type II (isthmic) slip is further subdivided based on the mechanism of pars interarticularis failure. Which of the following describes the pathophysiology defining a Type IIA slip?

Explanation

The Wiltse classification defines Type II as Isthmic spondylolisthesis. It is subdivided into Type IIA (fatigue/stress fracture of the pars), Type IIB (elongated but intact pars, resulting from repeated microfracture and healing), and Type IIC (acute traumatic fracture of the pars). Type I is dysplastic, and Type III is degenerative.

Question 35

Under low-speed, high-load conditions such as prolonged static standing, which of the following molecular components is primarily responsible for the boundary lubrication of articular cartilage?

Explanation

Joint lubrication is complex. Boundary lubrication dominates during high contact pressures and low sliding speeds (e.g., standing). This mechanism relies on surface-active molecules bound to the articular surface to prevent direct cartilage-on-cartilage wear. Lubricin (proteoglycan 4 or PRG4) is the primary glycoprotein responsible for boundary lubrication. Fluid-film lubrication dominates at high sliding speeds.

Question 36

A 24-year-old male presents after a high-speed motorcycle accident with a posterior knee dislocation. After urgent closed reduction, the patient has symmetric, palpable dorsalis pedis and posterior tibial pulses. However, the Ankle-Brachial Index (ABI) is measured at 0.85. What is the most appropriate next step in management?

Explanation

In the setting of a knee dislocation, vascular injury (particularly to the popliteal artery) is a major concern. An ABI of < 0.9, even in the presence of palpable pulses, raises strong suspicion for an occult intimal tear or flow-limiting vascular lesion. A CT angiogram (or duplex ultrasound depending on institutional protocol) is strictly indicated to evaluate the vascular integrity before proceeding with further management.

Question 37

A 52-year-old male presents with severe right-sided neck pain radiating down his arm. Physical examination reveals notable weakness in right elbow extension, an absent triceps reflex, and sensory loss over the volar aspect of his right middle finger. A paracentral cervical disc herniation is most likely impinging which cervical nerve root?

Explanation

The clinical presentation is classic for a C7 radiculopathy. The C7 nerve root supplies motor innervation to the triceps (elbow extension) and wrist flexors. It mediates the triceps reflex. Sensory distribution involves the middle finger. A C6 radiculopathy would affect the brachioradialis/biceps reflex, wrist extension, and sensation over the thumb and index finger.

Question 38

A 10-year-old skeletally immature male presents with lateral knee pain. Radiographs show a 15 mm osteochondritis dissecans (OCD) lesion on the lateral aspect of the medial femoral condyle. The physes are widely open. MRI reveals intact overlying cartilage with no high T2 signal fluid behind the lesion. What is the most appropriate initial management?

Explanation

Juvenile Osteochondritis Dissecans (JOCD) in a patient with widely open physes and a stable lesion (no fluid behind the lesion on T2 MRI, intact cartilage) has a very high rate of spontaneous healing. The standard initial treatment is conservative management, which consists of activity modification, protected weight-bearing, and potential immobilization. Surgery is reserved for unstable lesions or failure of prolonged conservative treatment.

Question 39

During the 'screw-home' mechanism of the knee, which muscle is uniquely responsible for 'unlocking' the knee from terminal extension to initiate flexion by internally rotating the tibia relative to the femur?

Explanation

The popliteus muscle acts to unlock the fully extended knee joint. In an open kinetic chain, it internally rotates the tibia relative to the femur. In a closed kinetic chain, it externally rotates the femur relative to the fixed tibia. It is innervated by the tibial nerve.

Question 40

A patient sustains a severe cervical spine injury resulting in tetraparesis. Neurological examination confirms that motor function is preserved below the neurological level of injury. Furthermore, out of the key muscle functions below the neurological level, 60% have a muscle grade of 3 or greater out of 5. Sacral sensation is intact. According to the ASIA Impairment Scale (AIS), how is this injury classified?

Explanation

The American Spinal Injury Association (ASIA) Impairment Scale classifies spinal cord injuries. ASIA D is defined as incomplete motor function preserved below the neurological level, with at least half (≥ 50%) of key muscle functions below the NLI having a muscle grade of 3 or greater. ASIA C requires more than half of key muscles below the NLI to have a grade of less than 3.

Question 41

Which zone of articular cartilage contains the highest concentration of proteoglycans, the lowest water content, and chondrocytes that are arranged in columnar networks perpendicular to the joint surface?

Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans, lowest water content, and chondrocytes arranged in vertical columns perpendicular to the joint surface. The collagen fibers are also oriented perpendicular to the articular surface to resist compressive forces.

Question 42

A 24-year-old male presents with an acute knee dislocation (KD III-M) with complete tears of the ACL, PCL, and MCL. Vascular status is intact. When considering reconstruction versus repair of the MCL in this multi-ligament setting, what does the current evidence suggest regarding surgical management?

Explanation

In multiligament knee injuries, recent literature (e.g., Stannard et al.) demonstrates that MCL reconstruction has significantly lower failure rates and provides superior stability compared to direct primary repair, especially for severe grade III tears in the setting of a multi-ligament injured knee.

Question 43

A 14-year-old female presents with adolescent idiopathic scoliosis. Radiographs demonstrate a main thoracic curve of 55 degrees, a proximal thoracic curve of 20 degrees that bends out to 15 degrees, and a thoracolumbar/lumbar curve of 35 degrees that bends out to 15 degrees. The T5-T12 kyphosis is +25 degrees. According to the Lenke classification system, what is her curve type?

Explanation

Lenke 1 is a Main Thoracic curve. The minor curves (proximal thoracic and thoracolumbar/lumbar) bend out to < 25 degrees, meaning they are non-structural. The sagittal modifier is Normal (N) because T5-T12 kyphosis is between +10 and +40 degrees. Therefore, she is a Lenke 1.

Question 44

In fresh osteochondral allograft (OCA) transplantation for large full-thickness cartilage defects of the femoral condyle, what is the maximum recommended storage time at 4 degrees Celsius to maintain acceptable chondrocyte viability before implantation?

Explanation

Prolonged storage of fresh osteochondral allografts at 4 degrees Celsius results in decreased chondrocyte viability. Current tissue bank protocols using specialized media typically allow storage up to 28 days, balancing disease testing requirements with chondrocyte viability, which drops significantly after 28 days.

Question 45

A 30-year-old male presents after a motor vehicle accident with bilateral jumped facets at C5-C6. He has an incomplete spinal cord injury. MRI reveals a large, extruded disc herniation posterior to the C5-C6 disc space compressing the spinal cord. What is the most appropriate next step in management?

Explanation

In the presence of an extruded disc herniation with an incomplete neurologic deficit, closed reduction is contraindicated due to the high risk of retropulsing the disc further into the canal and worsening the neurologic deficit. The appropriate management is anterior decompression (ACDF) prior to or concurrent with reduction.

Question 46

During clinical examination of a knee, the dial test is performed at both 30 degrees and 90 degrees of flexion. An increase in external rotation of 15 degrees at 30 degrees of flexion, but NO increase in external rotation at 90 degrees of flexion, indicates injury to which of the following structures?

Explanation

The dial test measures external rotation. Asymmetry of >10-15 degrees compared to the contralateral side is considered positive. A positive test at 30 degrees but normal at 90 degrees indicates an isolated posterolateral corner (PLC) injury. If the test is positive at both 30 and 90 degrees, it indicates a combined PCL and PLC injury.

Question 47

Lubricin (PRG4) is a highly glycosylated protein that provides boundary lubrication in synovial joints. Which zone of articular cartilage is primarily responsible for the synthesis of lubricin?

Explanation

Lubricin (PRG4) is synthesized primarily by the chondrocytes in the superficial zone of articular cartilage (as well as by synovial fibroblasts in the synovium). It plays a crucial role in boundary lubrication, reducing friction at the articular surface.

Question 48

A 65-year-old female presents with neurogenic claudication and an L4-L5 degenerative spondylolisthesis. She has failed conservative management. Which preoperative MRI finding is the strongest predictor of progressive postoperative instability if a decompression-only procedure (laminectomy without fusion) is performed?

Explanation

Bilateral facet fluid > 1.5 mm on T2 MRI is a strong indicator of micro-instability at that spinal segment. Performing a laminectomy alone in these patients carries a high risk of progressive slip (instability) and the subsequent need for revision fusion surgery.

Question 49

The Medial Patellofemoral Ligament (MPFL) is the primary restraint to lateral patellar translation. At what degree of knee flexion does the MPFL provide the greatest relative contribution to preventing lateral patellar displacement?

Explanation

The MPFL is the primary soft tissue restraint to lateral patellar displacement, contributing 50-60% of the restraining force at 0-30 degrees of knee flexion. As the knee flexes past 30 degrees, the patella engages the trochlear groove, and bony architecture becomes the primary stabilizer.

Question 50

A 78-year-old male sustains a Type II odontoid fracture after a ground-level fall. The fracture is displaced posteriorly by 4 mm. He is neurologically intact, but his medical history is significant for severe COPD and osteoporosis. Which of the following is the most appropriate initial management?

Explanation

In elderly patients with a Type II odontoid fracture, halo vest immobilization is poorly tolerated and associated with high morbidity and mortality (especially with pulmonary issues like COPD). Anterior odontoid screw fixation has high failure rates in osteoporotic bone. A rigid cervical collar is the preferred initial treatment for many elderly patients, prioritizing life and minimizing morbidity, even if it progresses to an asymptomatic fibrous nonunion.

Question 51

Matrix-induced autologous chondrocyte implantation (MACI) involves harvesting chondrocytes, expanding them in vitro, and seeding them onto a membrane prior to implantation. Which type of collagen primarily constitutes the membrane used in current FDA-approved MACI implants?

Explanation

The MACI implant utilizes a resorbable, porcine-derived type I and III collagen membrane. Autologous human chondrocytes are cultured and seeded onto this membrane before it is implanted into the cartilage defect.

Question 52

When drilling the femoral tunnel during Anterior Cruciate Ligament (ACL) reconstruction, positioning the tunnel too vertically (at the 12 o'clock position in the intercondylar notch) rather than lower (at the 10 o'clock or 2 o'clock position) results in which of the following biomechanical outcomes?

Explanation

A vertical femoral tunnel (e.g., 12 o'clock position) poorly controls rotational instability. While it acts strictly in the sagittal plane and may correct the Lachman test (AP stability), it fails to control the pivot shift (rotational stability). A more anatomic, lower position on the lateral notch wall is necessary to restore both.

Question 53

A 55-year-old male presents with chronic sacral pain and mild bowel/bladder dysfunction. Imaging reveals a large, midline, destructive lytic lesion in the sacrum. Biopsy demonstrates physaliferous cells with large cytoplasmic vacuoles. Which of the following is the most appropriate definitive management?

Explanation

The clinical picture and histologic finding of physaliferous cells confirm a chordoma. Chordomas are locally aggressive and largely resistant to conventional chemotherapy and radiation. The standard of care for definitive management is en bloc wide surgical excision with negative margins to prevent recurrence.

Question 54

A 50-year-old female experiences a 'pop' in the back of her knee while squatting. An MRI demonstrates a complete radial tear of the posterior horn of the medial meniscus exactly at its root attachment. Biomechanically, an un-repaired medial meniscus posterior root tear is equivalent to which of the following?

Explanation

A posterior root tear of the medial meniscus completely disrupts the hoop stresses of the meniscus, causing it to extrude. Biomechanical studies have shown that an un-repaired root tear leads to peak contact pressures and contact areas that are biomechanically equivalent to a total meniscectomy, rapidly accelerating the development of osteoarthritis.

Question 55

A 42-year-old male presents to the ED with severe low back pain, bilateral lower extremity radicular pain, saddle anesthesia, and urinary retention with overflow incontinence. He undergoes an emergent lumbar MRI confirming a massive central disc herniation. According to the literature, emergent surgical decompression within what timeframe from the onset of symptoms is associated with the best chances of full functional recovery?

Explanation

Cauda equina syndrome is a surgical emergency. The classic literature (including Ahn et al. and subsequent meta-analyses) suggests that surgical decompression performed within 48 hours of symptom onset provides a significant advantage in recovering both motor/sensory function and bowel/bladder control compared to delayed decompression.

Question 56

The microfracture technique for cartilage restoration works by penetrating the subchondral bone plate to release marrow elements. The resulting repair tissue is predominantly characterized by which of the following?

Explanation

Microfracture stimulates marrow elements to form a 'super clot', leading to the formation of fibrocartilage repair tissue. Fibrocartilage is mechanically inferior to normal hyaline articular cartilage and is composed primarily of Type I collagen, unlike native articular cartilage which is primarily Type II collagen.

Question 57

A 45-year-old active male presents with medial compartment osteoarthritis and varus malalignment. He is planned for a medial opening-wedge high tibial osteotomy (HTO). To maintain the native posterior tibial slope during the procedure, how should the anterior osteotomy gap compare to the posterior gap?

Explanation

In an opening-wedge HTO, the triangular cross-sectional shape of the proximal tibia dictates that to maintain the normal posterior slope, the anterior opening gap must be approximately half the size of the posterior gap. Opening the anterior and posterior gaps equally will inadvertently increase the posterior tibial slope.

Question 58

A 60-year-old male with a long-standing history of ankylosing spondylitis presents to the emergency department after a low-speed motor vehicle collision. He complains of neck pain but has a normal neurological examination. Plain radiographs of the cervical spine show a 'bamboo spine' but no obvious fracture. What is the mandatory next step in the workup?

Explanation

Patients with ankylosing spondylitis have highly rigid, osteopenic spines that fracture easily, often through the disc spaces or vertebral bodies (acting biomechanically like long-bone fractures). Because plain radiographs are extremely insensitive for detecting these fractures due to altered and overlapping anatomy, a CT scan of the entire cervical spine is mandatory in evaluating AS patients with neck pain following even minor trauma.

Question 59

In a skeletally immature patient with an osteochondritis dissecans (OCD) lesion of the knee, which location is most common, and which MRI finding best indicates instability of the lesion that may require surgical fixation?

Explanation

The classic and most common location for an OCD lesion of the knee is the lateral aspect of the medial femoral condyle (LAME acronym). In MRI evaluation, a high T2 signal rim (fluid) completely interposing behind the lesion and separating it from the underlying bone is the most reliable sign of instability, often necessitating surgical intervention.

Question 60

A 35-year-old female falls from a height. Imaging reveals an L1 burst fracture. She is neurologically intact. MRI demonstrates an intact posterior ligamentous complex (PLC). According to the Thoracolumbar Injury Classification and Severity Score (TLICS), what is her total score, and what is the recommended management?

Explanation

The TLICS system assigns points for morphology, neurologic status, and PLC integrity. Burst fracture = 2 points. Neurologically intact = 0 points. PLC intact = 0 points. Total score = 2. A score of <= 3 recommends nonoperative management. A score of 4 is surgeon's choice. A score >= 5 strongly recommends operative management.

Question 61

A 65-year-old male with progressive gait imbalance and fine motor clumsiness of the hands is found to have a positive Hoffmann sign on physical examination. This reflex finding is an indicator of compression or dysfunction affecting which specific neural pathway?

Explanation

The Hoffmann sign indicates an upper motor neuron lesion, specifically resulting from dysfunction of the corticospinal tract. It is a key examination finding in cervical spondylotic myelopathy.

Question 62

Duplication of the tidemark is a hallmark histological finding in early osteoarthritis. In normal articular cartilage microanatomy, the tidemark separates the deep (uncalcified) zone from which of the following layers?

Explanation

The tidemark is a distinct histological line that separates the deep zone of uncalcified articular cartilage from the calcified cartilage zone. Its duplication signifies the advancement of calcification into the uncalcified cartilage, typical of osteoarthritis.

Question 63

A 25-year-old male sustains a twisting knee injury. Examination reveals increased external tibial rotation at 30 degrees of knee flexion compared to the contralateral side. However, external rotation is symmetric at 90 degrees of knee flexion. Which structure is most likely injured?

Explanation

The dial test measures external tibial rotation. Increased rotation at 30 degrees but not at 90 degrees indicates an isolated injury to the posterolateral corner. If rotation is increased at both 30 and 90 degrees, a combined PLC and PCL injury is present.

Question 64

Which of the following historical findings most reliably differentiates neurogenic claudication from vascular claudication in a patient presenting with bilateral leg pain during ambulation?

Explanation

Walking uphill places the lumbar spine in relative flexion, increasing the cross-sectional area of the spinal canal and relieving symptoms of neurogenic claudication. Vascular claudication is exacerbated by exertion regardless of spinal posture and is relieved by standing stationary.

Question 65

A 30-year-old undergoes a microfracture procedure for a 1.5 cm2 full-thickness chondral defect on the medial femoral condyle. What is the primary histological composition of the repair tissue generated by this marrow stimulation technique?

Explanation

Marrow stimulation techniques, such as microfracture, result in a fibrocartilage repair response. Fibrocartilage is primarily composed of Type I collagen, which has inferior mechanical durability compared to the Type II collagen found in normal hyaline cartilage.

Question 66

A 9-year-old Tanner stage 1 patient requires surgical reconstruction for a completely torn anterior cruciate ligament (ACL). Which of the following graft choices is strictly contraindicated due to the highest risk of premature physeal closure and angular deformity?

Explanation

Bone-patellar tendon-bone grafts involve placing a rigid bone block across the open physis, drastically increasing the risk of premature physeal arrest. Physeal-sparing techniques or soft-tissue grafts with careful tunnel placement are indicated in skeletally immature patients.

Question 67

A 45-year-old presents with severe acute low back pain and bilateral sciatica. Which of the following objective findings is the most sensitive early indicator for evaluating suspected cauda equina syndrome?

Explanation

Urinary retention is the most consistent and sensitive early finding in cauda equina syndrome. A post-void residual (PVR) volume of less than 100 mL reliably rules out urinary retention in the context of this syndrome.

Question 68

In normal articular cartilage, which structural molecule is primarily responsible for generating the internal swelling pressure that resists compressive loads via the Donnan osmotic effect?

Explanation

Aggrecan, a large proteoglycan, contains numerous glycosaminoglycans (chondroitin and keratan sulfate) with highly negative charge densities. This attracts cations and water, creating a swelling pressure that allows cartilage to resist compression.

Question 69

A 68-year-old female presents with a painful catching and popping sensation during active knee extension from 45 to 30 degrees of flexion, one year after a posterior-stabilized total knee arthroplasty. What is the most likely pathophysiologic cause?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized total knee arthroplasties. A fibrosynovial nodule develops at the superior pole of the patella and catches in the femoral intercondylar box during extension.

Question 70

A 32-year-old male dives into shallow water and presents with quadriplegia. Lateral cervical radiographs reveal greater than 50% anterior subluxation of C5 on C6. What is the primary mechanism of this injury, and what is the associated soft tissue risk prior to reduction?

Explanation

Bilateral facet dislocation results from severe hyperflexion and is characterized radiographically by >50% anterior translation of the vertebral body. An MRI is often required prior to closed or open reduction due to the high risk of a pre-existing cervical disc herniation that could cause further cord compression during reduction.

Question 71

Under conditions of high loading and low speed in a synovial joint, boundary lubrication is the dominant mechanism protecting the cartilage surfaces. Which specific glycoprotein is primarily responsible for boundary lubrication?

Explanation

Lubricin (proteoglycan 4 or PRG4) is synthesized by superficial zone chondrocytes and synoviocytes. It is the primary molecule responsible for boundary lubrication, which reduces friction under high-load and low-speed conditions.

Question 72

A 55-year-old female experiences a sudden "pop" in the back of her knee while squatting. MRI reveals a complete radial tear adjacent to the posterior root attachment of the medial meniscus. Biomechanically, this injury is most equivalent to which of the following?

Explanation

A posterior root tear completely disrupts the circumferential hoop stresses of the meniscus. Biomechanical studies have shown that this renders the meniscus entirely non-functional, resulting in contact pressures equivalent to a total meniscectomy.

Question 73

According to the Wiltse classification of spondylolisthesis, a vertebral slip occurring secondary to a fatigue fracture of the pars interarticularis is classified as which type?

Explanation

Type II (Isthmic) spondylolisthesis is caused by a defect in the pars interarticularis, typically due to a stress/fatigue fracture. Type I is dysplastic, Type III is degenerative, Type IV is traumatic (fracture other than pars), and Type V is pathologic.

Question 74

A 14-year-old male presents with vague, activity-related knee pain. Radiographs demonstrate a classic osteochondritis dissecans (OCD) lesion. What is the most common anatomic location for an OCD lesion in the knee?

Explanation

The lateral aspect of the medial femoral condyle is the classic and most frequent location for osteochondritis dissecans of the knee, accounting for approximately 70-80% of all cases.

Question 75

A 48-year-old male presents with severe radicular pain radiating down the anterior aspect of his left thigh. Motor testing reveals profound weakness in knee extension, but ankle dorsiflexion is normal. An MRI shows a far lateral (extraforaminal) disc herniation at the L4-L5 level. Which nerve root is most likely compressed?

Explanation

In the lumbar spine, a far lateral (extraforaminal) disc herniation typically compresses the exiting nerve root at the same level. Therefore, an L4-L5 far lateral herniation compresses the L4 nerve root, causing weakness in quadriceps (knee extension) and anterior thigh pain.

Question 76

The pathogenesis of osteoarthritis is heavily mediated by an imbalance between anabolic and catabolic factors in the joint environment. Which of the following cytokine pairs are considered the primary catabolic drivers of cartilage degradation?

Explanation

Interleukin-1 beta (IL-1β) and Tumor Necrosis Factor-alpha (TNF-α) are the principal pro-inflammatory, catabolic cytokines in osteoarthritis. They upregulate matrix metalloproteinases (MMPs) and aggressively promote the breakdown of the extracellular matrix.

Question 77

A 30-year-old male sustains a high-energy traumatic knee dislocation. Following closed reduction, distal pulses are palpable but slightly asymmetric. At what resting Ankle-Brachial Index (ABI) threshold is a CT angiogram or vascular surgery consultation absolutely indicated?

Explanation

An Ankle-Brachial Index (ABI) of less than 0.9 in the setting of a knee dislocation is highly suggestive of a major arterial injury (e.g., popliteal artery). This finding mandates advanced vascular imaging (CT angiogram) or immediate vascular surgery consultation.

Question 78

The superficial zone of articular cartilage is uniquely adapted to resist shear stress. Which of the following best describes the histologic and biochemical composition characteristic of this specific zone?

Explanation

The superficial zone contains collagen fibers parallel to the joint surface, providing significant shear resistance. It also has the highest water content and the lowest proteoglycan concentration of all cartilage zones.

Question 79

A 65-year-old male presents with deteriorating hand dexterity and a broad-based gait. Tapping the volar surface of the distal phalanx of the middle finger elicits reflex flexion of the thumb and index finger. What spinal tract is primarily implicated in the disinhibition causing this clinical sign?

Explanation

The Hoffmann sign indicates upper motor neuron dysfunction, primarily implicating the descending corticospinal tract in cervical spondylotic myelopathy. It signifies reflex disinhibition due to spinal cord compression.

Question 80

A 55-year-old female sustains a complete radial tear of the medial meniscus posterior root. Biomechanically, the loss of hoop stress in this specific injury creates tibiofemoral contact pressures equivalent to which of the following?

Explanation

Complete posterior root tears of the medial meniscus disrupt circumferential hoop stresses, rendering the meniscus completely biomechanically incompetent. This results in elevated peak contact pressures and decreased contact areas equivalent to a total meniscectomy.

Question 81

A 14-year-old gymnast presents with persistent lower back pain. Radiographs reveal a Grade II isthmic spondylolisthesis at L5-S1. If radiculopathy is present, what is the most common neurological examination finding associated with this condition?

Explanation

In pediatric isthmic spondylolisthesis at L5-S1, the fibrocartilaginous pars defect mass typically compresses the exiting L5 nerve root in the neural foramen. This contrasts with degenerative spondylolisthesis, where the traversing root is usually affected.

Question 82

A 12-year-old boy presents with a 1.5 cm osteochondritis dissecans (OCD) lesion on the lateral aspect of the medial femoral condyle. His physes are wide open. After 6 months of non-operative management, MRI shows no healing but the lesion remains perfectly stable with intact overlying cartilage. What is the most appropriate next step?

Explanation

For a stable OCD lesion with intact articular cartilage that fails non-operative management in a skeletally immature patient, retrograde drilling is indicated. This stimulates vascular ingrowth and healing from the subchondral bone without violating the articular surface.

Question 83

The native anterior cruciate ligament (ACL) consists of two distinct functional bundles. Which of the following best describes the primary biomechanical function of the posterolateral (PL) bundle?

Explanation

The posterolateral (PL) bundle of the ACL is tightest in extension and provides primary resistance to rotatory loads, directly resisting the pivot shift phenomenon. The anteromedial (AM) bundle is tightest in flexion and primarily resists anterior tibial translation.

Question 84

A 70-year-old male presents with bilateral leg pain when walking. Which of the following history or physical examination findings most strongly differentiates neurogenic claudication from vascular claudication?

Explanation

Neurogenic claudication is typically relieved by lumbar flexion (e.g., pushing a shopping cart, riding a bike, sitting) because flexion increases the cross-sectional area of the stenotic spinal canal. Vascular claudication is strictly related to muscle exertion and is relieved simply by standing still.

Question 85

In reconstructing the posterolateral corner (PLC) of the knee, understanding native anatomy is critical to restoring stability. The popliteofibular ligament originates from the popliteus musculotendinous junction and inserts onto which specific anatomic landmark?

Explanation

The popliteofibular ligament is a crucial static stabilizer of the PLC, originating from the popliteus complex and inserting on the posteromedial down-slope of the fibular styloid. It acts as a primary restraint against excessive external tibial rotation.

Question 86

The compressive resilience of articular cartilage is primarily provided by aggrecan. Aggrecan monomers achieve this massive structural and biomechanical property through non-covalent binding with which of the following substances?

Explanation

Aggrecan monomers use link proteins to non-covalently bind to long hyaluronic acid backbones, forming massive proteoglycan aggregates. The highly negatively charged glycosaminoglycan side chains of these aggregates attract water, providing compressive stiffness via swelling pressure.

Question 87

A 25-year-old male sustains a C1 burst (Jefferson) fracture after an axial loading injury. An AP open-mouth odontoid radiograph demonstrates lateral mass displacement. The transverse alar ligament is considered ruptured if the combined lateral mass overhang exceeds what specific measurement?

Explanation

The Rule of Spence dictates that a combined lateral mass displacement of C1 on C2 greater than 6.9 mm on an AP open-mouth radiograph implies rupture of the transverse ligament. This indicates an unstable C1 ring injury requiring rigid immobilization or surgical stabilization.

Question 88

The medial patellofemoral ligament (MPFL) is a critical stabilizer of the extensor mechanism. At which degree of knee flexion does the MPFL provide the greatest percentage of restraint to lateral patellar translation?

Explanation

The MPFL acts as the primary soft-tissue restraint (providing up to 60% of restraining force) to lateral patellar translation in early flexion (0 to 30 degrees). Beyond 30 degrees of flexion, the patella typically engages the bony trochlear groove, which then becomes the primary stabilizer.

Question 89

In preoperative planning for adult spinal deformity surgery, the surgeon calculates the patient's pelvic incidence (PI). Which of the following statements best describes this vital radiographic parameter?

Explanation

Pelvic incidence (PI) is a fixed anatomical parameter unique to each individual's pelvis and does not change with posture or age. It is defined mathematically as the sum of Pelvic Tilt (PT) and Sacral Slope (SS) (i.e., PI = PT + SS).

Question 90

Boundary lubrication is essential for minimizing friction at the immediate surface of articulating joint cartilage. Which specific molecule is primarily responsible for this boundary lubrication mechanism?

Explanation

Lubricin (Proteoglycan 4 or PRG4) is a highly glycosylated protein secreted by superficial zone chondrocytes and synoviocytes. It specifically coats the articular surface to provide boundary lubrication, drastically reducing friction between opposing cartilage layers under load.

Question 91

A 45-year-old male with end-stage renal disease suffers a spontaneous patellar tendon rupture. During surgical repair, the surgeon decides to augment the repair with heavy non-absorbable suture passed through the tibial tubercle and the patella. What is the primary purpose of this augmentation?

Explanation

Augmentation of a patellar tendon repair with heavy suture or wire protects the primary repair site by mechanically offloading tension. This facilitates early, protected range of motion, which is crucial for preventing arthrofibrosis and restoring functional kinematics.

Question 92

A 50-year-old intravenous drug user presents with acute back pain, fever, and progressive lower extremity weakness. MRI confirms a large lumbar spinal epidural abscess. Which location within the spinal canal is most commonly affected in this condition?

Explanation

Spinal epidural abscesses are most frequently located in the posterior epidural space. This posterior compartment is larger, contains epidural fat, and houses a rich venous plexus (Batson's plexus) that is highly susceptible to hematogenous bacterial seeding.

Orthopedic Surgery Board Review MCQs: Arthroplasty, Trauma & Spine Part 255

OITE & ABOS Orthopedic Exam Prep: Knee, Spine & Cartilage MCQs | Part 22

Key Takeaway

OITE & ABOS Orthopedic Exam Prep: Knee, Spine & Cartilage MCQs | Part 22

Chapter Index