Surface Anatomy of the Back — MCQs

10 questions

Which of the following movements is least permitted in the lumbar region of the vertebral column?

After a 26-year-old man's car was sideswiped by a large truck, he is brought to the emergency department with multiple fractures of the transverse processes of the cervical and upper thoracic vertebrae. Which of the following muscles might be affected?

All of the following form the boundary of MacEwen's triangle except:

Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?

A patient presents with pneumothorax on chest x-ray. Which of the following is NOT a boundary of the triangle of safety for intercostal chest drain (ICD) insertion?

Which bone connects the sternum to the scapula?

Highest point of iliac crest is seen at?

Name the muscles being used in climbing a tree as shown in the figure.

In a diving accident that severed the spinal cord below the sixth cervical vertebra, which of the following muscles would be affected?

Q10

Which of the following muscles is not attached to the medial border of the scapula?

Surface Anatomy of the Back Indian Medical PG Practice Questions and MCQs

Question 1: Which of the following movements is least permitted in the lumbar region of the vertebral column?

A. Flexion
B. Extension
C. Lateral flexion
D. Rotation (Correct Answer)

Explanation: ***Rotation*** - The **lumbar spine permits the LEAST rotation** of all movements (~5° total rotation), making this the correct answer. - The PRIMARY limiting factor is the **sagittal (near-vertical) orientation of the lumbar facet joints**, which are oriented in the coronal plane and face medially/laterally. - This facet orientation creates a **mechanical block to rotational movement**, acting like interlocking barriers. - The thick **intervertebral discs** in the lumbar region also resist torsional forces, further limiting rotation. *Flexion* - The lumbar region permits **excellent flexion** (forward bending), with approximately 50-60° of range. - The **large, wedge-shaped intervertebral discs** allow substantial anterior compression and movement. - This is one of the primary movements of the lumbar spine. *Extension* - **Extension** (backward bending) is moderately permitted in the lumbar spine, with approximately 15-20° of range. - Eventually limited by contact between **spinous processes** and the posterior ligamentous structures. - Still considerably more movement than rotation. *Lateral flexion* - **Lateral flexion** (sideways bending) is well permitted, with approximately 20° of movement to each side. - The structure of the vertebral bodies and **compressible intervertebral discs** allows good range of motion in the coronal plane. - Significantly more mobile than rotation.

Question 2: After a 26-year-old man's car was sideswiped by a large truck, he is brought to the emergency department with multiple fractures of the transverse processes of the cervical and upper thoracic vertebrae. Which of the following muscles might be affected?

A. Serratus Posterior Superior
B. Rhomboid major
C. Trapezius
D. Levator scapulae (Correct Answer)

Explanation: ***Levator scapulae*** - The **levator scapulae** muscle originates from the posterior tubercles of the transverse processes of cervical vertebrae C1-C4. - Fractures to these **transverse processes** could directly impact the attachment and function of the levator scapulae. *Serratus Posterior Superior* - The **serratus posterior superior** originates from the nuchal ligament and spinous processes of C7-T3, inserting onto ribs 2-5 - Its origin is primarily from the **spinous processes**, not the transverse processes, of the cervical and upper thoracic vertebrae. *Rhomboid major* - The **rhomboid major** muscle originates from the spinous processes of T2-T5, inserting into the medial border of the scapula. - Its origins are from the **spinous processes** of the upper thoracic vertebrae, not the transverse processes. *Trapezius* - The **trapezius** is a large muscle with a broad origin from the external occipital protuberance, nuchal ligament, and spinous processes of C7-T12. - While it covers a large area, its attachments are primarily to the **occiput** and **spinous processes**, not the transverse processes of the cervical and upper thoracic vertebrae.

Question 3: All of the following form the boundary of MacEwen's triangle except:

A. Temporal line
B. Posterosuperior segment of bony external auditory canal
C. Promontory (Correct Answer)
D. Tangent drawn to the external auditory meatus

Explanation: ***Promontory*** - The **promontory** is a bony projection on the medial wall of the **middle ear cavity**, formed by the basal turn of the cochlea. - It is located deep to the tympanic membrane and is **not a boundary of MacEwen's triangle**, which is a superficial external bony landmark on the lateral surface of the temporal bone. - MacEwen's triangle is used surgically to locate the mastoid antrum, while the promontory is an internal middle ear structure. *Temporal line* - The **temporal line** (supramastoid crest, continuation of the posterior root of the zygoma) forms the **superior boundary** of MacEwen's triangle. - This is a key anatomical reference point for mastoid surgery. *Posterosuperior segment of bony external auditory canal* - The **posterosuperior margin of the external auditory meatus** forms the **anterior boundary** of MacEwen's triangle. - This boundary guides surgical dissection during mastoidectomy. *Tangent drawn to the external auditory meatus* - A **tangent drawn to the posterior margin of the external auditory meatus** forms the **posterior boundary** of MacEwen's triangle. - This is one of the three boundaries that define this important surgical landmark, also known as the **suprameatal triangle**.

Question 4: Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?

A. Astrocytoma
B. Neurofibromatosis
C. Ependymoma
D. Aortic aneurysm (Correct Answer)

Explanation: ***Aortic aneurysm*** - An **aortic aneurysm** is located **anterior to the vertebral column** and primarily affects the anterior aspect of the vertebral bodies, causing **anterior scalloping** due to chronic pulsatile erosion, not posterior scalloping. - Posterior scalloping requires intraspinal pathology that expands the spinal canal from within; an aortic aneurysm is extraspinal and anterior, making it the **least likely** cause of posterior scalloping. *Neurofibromatosis* - **Neurofibromatosis** commonly causes posterior vertebral scalloping due to **dural ectasia** (widening of the dural sac) and pressure erosion from expanding neurofibromas within the spinal canal. - This condition is also associated with paraspinal masses, posterior vertebral body erosion, and scoliosis. *Astrocytoma* - An **intramedullary astrocytoma** within the spinal cord can lead to expansion of the cord that causes chronic pressure on the posterior vertebral bodies from within the spinal canal. - This slow-growing intraspinal tumor gradually remodels the bone, causing posterior scalloping. *Ependymoma* - Similar to astrocytoma, an **intramedullary ependymoma** (the most common primary intramedullary tumor in adults) can enlarge the spinal cord, leading to pressure erosion on the posterior vertebral bodies. - This is a characteristic feature of slowly growing intraspinal masses, which cause remodeling of the bony spinal canal.

Question 5: A patient presents with pneumothorax on chest x-ray. Which of the following is NOT a boundary of the triangle of safety for intercostal chest drain (ICD) insertion?

A. Base of axilla
B. Mid - clavicular line (Correct Answer)
C. Lateral border of latissimus dorsi
D. Lateral edge of pectoralis major

Explanation: ***Mid-clavicular line*** - The **mid-clavicular line** is **NOT** a boundary of the triangle of safety; it is a vertical reference line located centrally on the thorax. - The triangle of safety is located in the **mid-axillary region**, not at the mid-clavicular line. - The mid-clavicular line is used for other procedures but is **anterior to the safe zone** for ICD insertion. *Base of axilla* - The **base of the axilla** forms the **superior boundary** of the triangle of safety. - This boundary is typically at the level of the **5th intercostal space** (nipple level in males). - It helps guide ICD insertion away from the **brachial plexus** and axillary vessels. *Lateral border of latissimus dorsi* - The **lateral border of the latissimus dorsi muscle** forms the **posterior boundary** of the triangle of safety. - This landmark ensures the insertion is anterior to major back muscles and avoids injury to the long thoracic nerve. *Lateral edge of pectoralis major* - The **lateral edge of the pectoralis major muscle** forms the **anterior boundary** of the triangle of safety. - This ensures the ICD is inserted lateral to the pectoral muscle, avoiding breast tissue and superficial vessels.

Question 6: Which bone connects the sternum to the scapula?

A. Clavicle (Correct Answer)
B. First rib
C. Manubrium
D. Second rib

Explanation: ***Clavicle*** - The **clavicle**, or collarbone, is the only bone that directly connects the **axial skeleton** (via the sternum) to the **appendicular skeleton** (via the scapula). - It articulates medially with the **manubrium** of the sternum at the sternoclavicular joint and laterally with the **acromion** of the scapula at the acromioclavicular joint. *First rib* - The **first rib** articulates with the **manubrium** of the sternum but does not connect directly to the scapula. - Its primary role is to form part of the **thoracic cage**, protecting internal organs. *Manubrium* - The **manubrium** is the superior part of the **sternum** and articulates with the clavicles and the first two ribs. - It does not directly connect to the **scapula**; rather, the clavicle mediates this connection. *Second rib* - The **second rib** articulates with both the **manubrium** and the body of the sternum at the **sternal angle**. - Like the first rib, it is part of the **thoracic cage** and does not directly connect to the scapula.

Question 7: Highest point of iliac crest is seen at?

A. L3
B. L4 (Correct Answer)
C. S2
D. S1

Explanation: ***L4*** - The **highest point of the iliac crest** typically corresponds to the level of the **L4 vertebral body**. - This anatomical landmark is crucial for procedures like **lumbar punctures** and determining the location for **epidural anesthesia**. *L3* - The L3 vertebral level is generally located slightly **above the highest point of the iliac crest**. - While close, it is not the most consistent anatomical correlation for the highest point. *S2* - The **S2 vertebral level** is significantly **below the iliac crests**, marking the approximate midpoint of the sacroiliac joint. - This level is used as a landmark for the **dermatome of the posterior thigh**. *S1* - The **S1 vertebral level** is also located **below the iliac crests**, forming the most superior segment of the sacrum. - It is used as a landmark for the **dermatome of the lateral foot and posterior leg**, and corresponds to the ankle jerk reflex.

Question 8: Name the muscles being used in climbing a tree as shown in the figure.

A. Latissimus dorsi and pectoralis major (Correct Answer)
B. Teres major and pectoralis major
C. Teres minor and pectoralis minor
D. External oblique and pectoralis major

Explanation: ***Latissimus dorsi and pectoralis major*** - The **latissimus dorsi** is a large, powerful muscle responsible for adduction, extension, and internal rotation of the arm, all crucial for pulling the body upward during climbing. - The **pectoralis major** is a large, fan-shaped muscle that helps with adduction, flexion, and internal rotation of the humerus, also vital for pulling oneself up against gravity. *Teres major and pectoralis major* - While the **pectoralis major** is involved, the **teres major** is a smaller muscle that primarily assists the latissimus dorsi in extension, adduction, and internal rotation of the humerus, but is not as dominant in the main pulling action as the latissimus dorsi. - The primary pulling force comes from larger muscles, making the teres major a less significant contributor to the overall climbing action. *Teres minor and pectoralis minor* - The **teres minor** is part of the rotator cuff and primarily functions in external rotation of the humerus, which is not a primary movement for pulling oneself up. - The **pectoralis minor** is a small, thin muscle that stabilizes the scapula and depresses the shoulder; it does not directly contribute to the powerful pulling action needed for climbing. *External oblique and pectoralis major* - The **external oblique** is an abdominal muscle involved in trunk rotation and flexion, providing core stability but not directly contributing to the primary upper body pulling motion for climbing. - While the **pectoralis major** is correctly identified, the external oblique is not a primary muscle used for the upward pulling motion in climbing.

Question 9: In a diving accident that severed the spinal cord below the sixth cervical vertebra, which of the following muscles would be affected?

A. Deltoid
B. Infraspinatus
C. Levator Scapulae
D. Latissimus Dorsi (Correct Answer)

Explanation: ***Latissimus Dorsi*** - The **latissimus dorsi muscle** is primarily innervated by the **thoracodorsal nerve**, which arises from the **C6, C7, and C8** nerve roots (with C7 and C8 being the predominant contributors) [1]. - A spinal cord injury below the sixth cervical vertebra would affect the C7 and C8 segments, thereby disrupting the nerve supply to the latissimus dorsi, leading to weakness or paralysis. - This muscle is responsible for adduction, extension, and internal rotation of the shoulder. *Deltoid* - The **deltoid muscle** is innervated by the **axillary nerve**, which arises predominantly from the **C5 and C6** nerve roots. - Since the injury is below the C6 vertebra, the upper cervical segments (C5 and C6) would remain intact above the level of injury. - Therefore, deltoid function would be preserved. *Infraspinatus* - The **infraspinatus muscle** is innervated by the **suprascapular nerve**, which arises from the **C5 and C6** nerve roots. - Similar to the deltoid, its innervation originates above the level of the spinal cord injury and would be spared. *Levator Scapulae* - The **levator scapulae muscle** receives innervation from the **C3, C4, and C5** spinal nerves, as well as contributions from the dorsal scapular nerve (predominantly C5). - All of these nerve roots originate well above the level of injury, so this muscle would not be affected.

Question 10: Which of the following muscles is not attached to the medial border of the scapula?

A. Serratus anterior
B. Levator scapulae
C. Teres major (Correct Answer)
D. Rhomboid major

Explanation: ***Teres major*** - The **teres major** muscle originates from the **inferior angle and lower part of the lateral border** of the scapula, NOT the medial border. - It inserts into the medial lip of the intertubercular groove of the humerus. - This is the correct answer as it does not attach to the medial border of the scapula. *Serratus anterior* - The **serratus anterior** muscle originates from the outer surfaces of the upper 8-9 ribs and inserts along the **entire medial border** of the scapula on its anterior (costal) surface. - It plays a crucial role in protraction and upward rotation of the scapula, keeping it applied to the thoracic wall. *Levator scapulae* - The **levator scapulae** muscle originates from the transverse processes of the C1-C4 vertebrae and inserts into the **superior angle and upper part of the medial border** of the scapula. - Its primary actions are to elevate the scapula and assist in downward rotation. *Rhomboid major* - The **rhomboid major** muscle originates from the spinous processes of T2-T5 vertebrae and attaches to the **medial border** of the scapula between the spine and inferior angle. - It acts to retract, elevate, and rotate the scapula downward.

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