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1. General Principles & Basic Science MCQs

Practice Set 147 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2921

Topic: 1. General Principles & Basic Science

During evaluation of a post-traumatic lower extremity deformity, the mechanical axis deviation (MAD) is measured at 35 mm lateral to the center of the knee. The mLDFA is 87 degrees, and the MPTA is 98 degrees. What is the primary diagnosis?

. Femoral varus
. Femoral valgus
. Tibial valgus
. Tibial varus
. Intra-articular ligamentous laxity

Correct Answer & Explanation

. Tibial valgus

Explanation

A lateral MAD indicates an overall valgus alignment. The mLDFA is normal (~88 degrees), while the MPTA is abnormally high (normal ~87 degrees). An MPTA of 98 degrees signifies a severe proximal tibial valgus deformity.

Question 2922

Topic: Biology, Genetics & Bone Healing

Which phase of distraction osteogenesis allows for the initial resolution of the inflammatory response and the formation of a soft callus prior to the commencement of stretching?

. Distraction phase
. Consolidation phase
. Latency phase
. Remodeling phase
. Mineralization phase

Correct Answer & Explanation

. Latency phase

Explanation

The latency phase typically lasts 5 to 7 days post-osteotomy. It allows for initial hematoma formation, resolution of acute inflammation, and soft callus formation before the mechanical distraction process begins.

Question 2923

Topic: 1. General Principles & Basic Science

When planning an osteotomy to correct a diaphyseal angular deformity, identifying the bisector line of the angle formed by the proximal and distal anatomical axes is crucial. What is the clinical significance of this bisector line?

. It defines the plane of maximum deformity
. It contains all possible hinge points for angular correction without length change
. It contains all possible Centers of Rotation of Angulation (CORAs)
. It dictates the type of hardware used for fixation
. It represents the mechanical axis of the involved segment

Correct Answer & Explanation

. It contains all possible hinge points for angular correction without length change

Explanation

The transverse bisector line of the angle formed by the intersection of the proximal and distal axes contains all the geometric CORAs for that specific deformity. Placing the hinge along this line ensures pure angular correction.

Question 2924

Topic: 1. General Principles & Basic Science

A 40-year-old male requires a distal femoral osteotomy for a 12-degree valgus deformity. If a lateral opening wedge osteotomy is chosen over a medial closing wedge osteotomy, what is the expected effect on overall limb length?

. Limb shortening
. Limb lengthening
. No change in limb length
. Lengthening of the femur but shortening of the overall limb
. Unpredictable length changes

Correct Answer & Explanation

. Limb lengthening

Explanation

Opening wedge osteotomies add a wedge of bone (or graft), generally increasing the length of the bone segment. Therefore, a lateral opening wedge will increase the overall length of the femur and the limb.

Question 2925

Topic: Biomechanics & Biomaterials

When evaluating the Joint Line Convergence Angle (JLCA) on a weight-bearing long-leg radiograph, a value of 6 degrees opening laterally indicates which of the following?

. Normal knee kinematics
. Medial compartment ligamentous laxity
. Lateral compartment ligamentous laxity or significant cartilage wear
. A fixed bony deformity of the distal femur
. A fixed bony deformity of the proximal tibia

Correct Answer & Explanation

. Lateral compartment ligamentous laxity or significant cartilage wear

Explanation

The normal JLCA is 0 to 2 degrees. An increased angle opening laterally indicates an intra-articular source of alignment change, such as lateral joint space narrowing (cartilage loss) or medial collateral ligament tightness resulting in lateral opening.

Question 2926

Topic: 1. General Principles & Basic Science

A 45-year-old presents with a diaphyseal tibial varus deformity. Preoperative planning determines the Center of Rotation of Angulation (CORA). If the osteotomy and the angulation correction axis (ACA) are both placed exactly at the CORA, what is the expected geometric outcome?

. Complete alignment of mechanical axes without translation
. Collinear mechanical axes with paradoxical translation
. Parallel but translated mechanical axes
. Correction of angulation but creation of a secondary rotational deformity
. Lengthening of the segment without angular correction

Correct Answer & Explanation

. Complete alignment of mechanical axes without translation

Explanation

According to Osteotomy Rule 1, placing both the osteotomy and the angulation correction axis (ACA) exactly at the CORA results in collinear realignment of the mechanical axes without any translational displacement.

Question 2927

Topic: 1. General Principles & Basic Science

According to the principles of deformity correction defined by Paley, which of the following accurately describes the expected outcome of an osteotomy performed strictly following Osteotomy Rule 1?

. The osteotomy is placed at the CORA and the hinge is placed outside the CORA, resulting in translation.
. The osteotomy and the hinge are both placed at the CORA, resulting in pure angular correction without translation.
. The osteotomy is placed proximal to the CORA, resulting in angular correction with necessary translation.
. The osteotomy is placed distal to the CORA, resulting in pure translation without angulation.
. The hinge is placed at the convex cortex away from the CORA, resulting in an opening wedge without translation.

Correct Answer & Explanation

. The osteotomy and the hinge are both placed at the CORA, resulting in pure angular correction without translation.

Explanation

Paley's Osteotomy Rule 1 states that when both the osteotomy and the axis of rotation (hinge) are located at the Center of Rotation of Angulation (CORA), pure angular correction is achieved without any translation of the bone fragments.

Question 2928

Topic: 1. General Principles & Basic Science

A 45-year-old male undergoes a medial opening wedge high tibial osteotomy (HTO) for isolated medial compartment knee osteoarthritis. Intraoperatively, the surgeon opens the osteotomy gap equally at the anterior and posterior cortices. Which of the following unintended geometric changes to the proximal tibia is most likely to occur?

. Decreased posterior tibial slope
. Increased posterior tibial slope
. Increased patellar height (patella alta)
. External rotation of the distal fragment
. Varus malalignment of the mechanical axis

Correct Answer & Explanation

. Increased posterior tibial slope

Explanation

Because the proximal tibia is triangular in cross-section (narrower anteriorly), opening the gap equally at the anterior and posterior margins will inadvertently increase the posterior tibial slope. To maintain the native slope, the anterior opening should typically be roughly half the size of the posterior opening.

Question 2929

Topic: 1. General Principles & Basic Science

A 24-year-old male requires correction of a post-traumatic tibial angular deformity. Preoperative planning identifies the Center of Rotation of Angulation (CORA). According to Paley's First Osteotomy Rule, if the osteotomy and the axis of correction of angulation (ACA) both pass directly through the CORA, what is the expected geometric outcome of the correction?

. Pure angulation without translation
. Angulation with a new translation deformity
. Angulation with intended co-axial translation
. Pure translation without angulation
. Rotational realignment with paradoxical shortening

Correct Answer & Explanation

. Pure angulation without translation

Explanation

Paley's Rule 1 states that when the osteotomy and the ACA both pass through the CORA, the deformity corrects by pure angulation without any translation. This maintains the collinearity of the proximal and distal anatomical/mechanical axes.

Question 2930

Topic: 1. General Principles & Basic Science

A surgeon is planning a proximal tibial osteotomy for a varus deformity. To avoid the tibial tubercle, the osteotomy is made distal to the identified CORA. However, the axis of correction of angulation (ACA) is maintained exactly at the CORA. According to Paley's Second Osteotomy Rule, what will occur at the osteotomy site?

. Pure translation
. Pure angulation
. Angulation and translation
. Rotational subluxation
. Distraction and lengthening only

Correct Answer & Explanation

. Angulation and translation

Explanation

Paley's Rule 2 dictates that if the ACA is at the CORA but the osteotomy is at a different level, the axes will correctly realign, but angulation and translation will occur at the osteotomy site. The translation is necessary to achieve collinearity of the axes.

Question 2931

Topic: Biology, Genetics & Bone Healing

A 19-year-old patient undergoes an osteotomy and application of a circular external fixator for a 5 cm tibial lengthening. What is the standard recommended latency period after corticotomy before initiating distraction?

. 0 to 1 days
. 3 to 4 days
. 7 to 10 days
. 14 to 18 days
. 21 to 28 days

Correct Answer & Explanation

. 7 to 10 days

Explanation

The latency period allows for the initial inflammatory and soft callus phases of bone healing to begin. For metaphyseal corticotomies in distraction osteogenesis, 7 to 10 days is the standard latency period.

Question 2932

Topic: 1. General Principles & Basic Science

A 35-year-old male with a symptomatic distal femoral valgus deformity is undergoing a medial closing wedge osteotomy. Compared to a lateral opening wedge osteotomy, what is a primary biomechanical or biological advantage of the medial closing wedge technique?

. It inherently lengthens the limb
. It completely avoids the medial collateral ligament
. It provides higher intrinsic stability and eliminates the need for bone grafting
. It protects the common peroneal nerve from traction injury
. It corrects sagittal plane deformity automatically

Correct Answer & Explanation

. It provides higher intrinsic stability and eliminates the need for bone grafting

Explanation

A medial closing wedge osteotomy is inherently stable due to broad cancellous bone contact, allowing high union rates without the need for structural bone graft. However, it does cause a slight shortening of the limb.

Question 2933

Topic: 1. General Principles & Basic Science

According to Paley's Third Osteotomy Rule, if both the osteotomy and the axis of correction of angulation (ACA) are located at a level separate from the true CORA, what is the resulting geometric effect?

. Pure angulation
. Pure translation
. Angulation combined with intended translation
. Angulation combined with a new, unintended translation deformity
. Rotational correction only

Correct Answer & Explanation

. Angulation combined with a new, unintended translation deformity

Explanation

Paley's Rule 3 states that if both the ACA and the osteotomy are outside the CORA, the mechanical axes will remain parallel but not collinear, creating a new translational deformity (malalignment) at the end of the correction.

Question 2934

Topic: 1. General Principles & Basic Science

Following plain radiographs, an MRI of the left knee was performed. The image below is a representative sequence from this MRI study.

Which of the following MRI findings, clearly depicted in the case description and often visible on sequences like the one shown, is considered pathognomonic for Pigmented Villonodular Synovitis (PVNS)?

. Extensive bone marrow edema adjacent to erosions
. Multiple intra-articular calcified loose bodies
. Diffuse synovial thickening with low signal intensity on T1- and T2-weighted sequences and prominent blooming on GRE
. Complete absence of joint effusion
. High signal intensity on T1-weighted images within the synovium

Correct Answer & Explanation

. Diffuse synovial thickening with low signal intensity on T1- and T2-weighted sequences and prominent blooming on GRE

Explanation

Correct Answer: C - Diffuse synovial thickening with low signal intensity on T1- and T2-weighted sequences and prominent blooming on GREThe case explicitly states that the "most critical and pathognomonic finding was the presence of extensive areas of low signal intensity on both T1- and T2-weighted sequences within the hypertrophic synovial masses. On the Gradient-Recalled Echo (GRE) sequences, these areas demonstrated a prominent 'blooming artifact.' This magnetic susceptibility artifact is caused by the paramagnetic properties of extensive hemosiderin deposition within the synovial tissue, a hallmark of Pigmented Villonodular Synovitis (PVNS)." The provided image, while not explicitly labeled as GRE, shows diffuse, dark (low signal) synovial tissue, consistent with hemosiderin deposition.A. Extensive bone marrow edema adjacent to erosions:The case specifically notes, "there was no significant surrounding bone marrow edema adjacent to these erosions," which helps differentiate chronic PVNS erosions from acute inflammatory or infectious erosions.B. Multiple intra-articular calcified loose bodies:This is characteristic of synovial chondromatosis, not PVNS. The MRI description for PVNS focuses on synovial proliferation and hemosiderin, not calcified bodies.D. Complete absence of joint effusion:The patient presented with a persistent, palpable joint effusion, and the MRI confirmed a "moderate to large joint effusion." An absence of effusion would contradict the clinical and imaging findings.E. High signal intensity on T1-weighted images within the synovium:While some hemorrhagic conditions can show high signal on T1 due to methemoglobin, the classic and pathognomonic finding for PVNS is low signal on both T1 and T2 due to chronic hemosiderin deposition, which has a paramagnetic effect.

Question 2935

Topic: Infection, Pharmacology & VTE

During a repeat diagnostic arthrocentesis, 45 cc of dark, opaque, reddish-brown fluid was aspirated from the patient's knee. The fluid was negative for crystals, and cultures were negative. Which classic description is often used to characterize the appearance of synovial fluid in Pigmented Villonodular Synovitis (PVNS)?

. Clear, straw-colored
. Turbid, purulent
. Resembling 'crankcase oil' or liquid chocolate
. Highly viscous, mucinous
. Cloudy, yellow with urate crystals

Correct Answer & Explanation

. Resembling 'crankcase oil' or liquid chocolate

Explanation

Correct Answer: C - Resembling 'crankcase oil' or liquid chocolateThe case explicitly states that the aspirated fluid was "dark, opaque, reddish-brown fluid, often classically described as resembling 'crankcase oil' or liquid chocolate." This distinctive appearance is due to the chronic presence of blood and hemosiderin within the joint, a hallmark of PVNS.A. Clear, straw-colored:This describes normal synovial fluid or a non-inflammatory effusion, which is not consistent with the patient's presentation.B. Turbid, purulent:This is characteristic of septic arthritis, which was ruled out by negative cultures and Gram stain.D. Highly viscous, mucinous:This can be seen in conditions like synovial chondromatosis or early osteoarthritis, but not the dark, bloody fluid of PVNS.E. Cloudy, yellow with urate crystals:This is characteristic of gout, which was ruled out by crystal analysis.

Question 2936

Topic: Surgical Anatomy & Approaches

A 25-year-old male undergoes an open Latarjet procedure for recurrent anterior shoulder instability with 25% glenoid bone loss. Postoperatively, he complains of numbness over the lateral aspect of his forearm, but motor function of the biceps is intact. Which nerve is most likely injured, and what is its typical distance from the coracoid tip where it enters the conjoint tendon?

. Axillary nerve; 2 cm distal
. Musculocutaneous nerve; 5 cm distal
. Musculocutaneous nerve; 1 cm distal
. Radial nerve; spiral groove
. Median nerve; 3 cm distal

Correct Answer & Explanation

. Musculocutaneous nerve; 5 cm distal

Explanation

The musculocutaneous nerve typically enters the coracobrachialis approximately 5 cm (range 3-8 cm) distal to the coracoid tip. Injury can result in lateral forearm numbness (lateral antebrachial cutaneous nerve) and biceps weakness, though partial injuries may spare motor function.

Question 2937

Topic: Infection, Pharmacology & VTE

A 28-year-old female presents with a chronic, mildly painful, swollen knee without any history of preceding trauma. Aspiration of the joint yields a thick, dark brown, "chocolate-like" fluid that does not clear with sequential aspiration. Which of the following is the most likely diagnosis?

. Gouty arthritis
. Synovial osteochondromatosis
. Pigmented villonodular synovitis (PVNS)
. Septic arthritis
. Hemochromatosis arthropathy

Correct Answer & Explanation

. Pigmented villonodular synovitis (PVNS)

Explanation

Aspiration of dark brown or "chocolate" colored fluid from a non-traumatized, chronically swollen knee is classic for PVNS. The color is due to heavy hemosiderin deposition from repeated microscopic bleeding of the hyperplastic synovium.

Question 2938

Topic: Surgical Anatomy & Approaches

When comparing the localized and diffuse forms of Pigmented Villonodular Synovitis (PVNS) regarding surgical outcomes, which of the following statements is most accurate?

. Recurrence is extremely rare following excision in both forms
. Diffuse PVNS has a significantly higher recurrence rate than localized PVNS after surgical excision
. Localized PVNS has a higher recurrence rate than diffuse PVNS due to incomplete margins
. Adjuvant external beam radiotherapy is required for localized PVNS to prevent recurrence
. Recurrence rates are identical and strictly dependent on surgical approach (open vs arthroscopic)

Correct Answer & Explanation

. Diffuse PVNS has a significantly higher recurrence rate than localized PVNS after surgical excision

Explanation

Diffuse PVNS involves the entire synovial lining of the joint and has a notoriously high recurrence rate (ranging from 14% to 55%) even after extensive total synovectomy. Localized PVNS is much more amenable to complete excision and has a low recurrence rate.

Question 2939

Topic: Surgical Anatomy & Approaches

A 22-year-old rugby player undergoes an open Latarjet procedure for recurrent anterior instability with 25% glenoid bone loss. Postoperatively, he exhibits weakness in elbow flexion and decreased sensation over the lateral aspect of his forearm. Which nerve was most likely injured during the procedure?

. Axillary nerve
. Radial nerve
. Musculocutaneous nerve
. Median nerve
. Suprascapular nerve

Correct Answer & Explanation

. Musculocutaneous nerve

Explanation

The musculocutaneous nerve enters the coracobrachialis approximately 3-8 cm distal to the coracoid process. It is at significant risk during retraction and coracoid mobilization in the Latarjet procedure, leading to biceps weakness and lateral forearm sensory deficits if injured.

Question 2940

Topic: 1. General Principles & Basic Science

Following an arthroscopic synovectomy for diffuse Pigmented Villonodular Synovitis (PVNS) of the knee, a 40-year-old patient asks about the likelihood of disease recurrence. What is the approximate expected recurrence rate for the diffuse form of PVNS treated with synovectomy alone?

. Less than 5%
. 10-15%
. 30-50%
. 75-85%
. Approaching 100%

Correct Answer & Explanation

. 30-50%

Explanation

Diffuse PVNS (TGCT) is highly aggressive and difficult to completely resect microscopically. This leads to recurrence rates estimated between 30% and 50% after surgical synovectomy alone, often requiring adjuvant treatments.

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