Topic Overview

Facts to Remember – Back

• Back consists of skin, fasciae, muscles, vertebral column, spinal cord with meninges, vessels, and nerves.

• C7 vertebra → most prominent spinous process (vertebra prominens).

• Spine of scapula → opposite T3 vertebra.

• Inferior angle of scapula → opposite T7 vertebra.

• Iliac crest highest point → level of L4 vertebra.

• PSIS dimple → corresponds to S2 vertebra.

• Sacral hiatus → landmark for caudal epidural anesthesia.

• Skin of back supplied by posterior (dorsal) rami of spinal nerves.

• Superficial fascia of back → thin, fatty, mobile.

• Deep fascia in lumbar region forms thoracolumbar fascia (posterior, middle, anterior layers).

• Extrinsic muscles of back (superficial & intermediate) → supplied by ventral rami (except trapezius by accessory nerve).

• Intrinsic muscles of back (deep) → supplied by dorsal rami of spinal nerves.

• Trapezius → accessory nerve; action = elevate, retract, depress scapula.

• Latissimus dorsi → thoracodorsal nerve; action = extend, adduct, medially rotate arm.

• Levator scapulae & Rhomboids → dorsal scapular nerve; action = elevate and retract scapula.

• Intermediate back muscles (serratus posterior superior & inferior) → accessory muscles of respiration.

• Deep back muscles divided into splenius, erector spinae, transversospinalis, and small segmental muscles.

• Erector spinae (iliocostalis, longissimus, spinalis) → main extensors of spine.

• Semispinalis, multifidus, rotatores → stabilize vertebrae, assist rotation.

• Interspinales & intertransversarii → fine-tuning of movements.

• Blood supply of back → posterior branches of intercostal, lumbar, and sacral arteries.

• Common causes of back pain → muscle strain, spasm, herniated discs, TB spine.

• Erb’s palsy and winged scapula highlight nerve supply importance of superficial back muscles.

• Trapezius test → shrugging shoulders against resistance.

• Latissimus dorsi test → resisted climbing or adduction/extension of arm.

Clinicoanatomical Problems – Back

1. Vertebra Prominens Palpation

• Case: A medical student palpates a prominent bony projection at the base of neck.

• Q: Which vertebra is this?
  → C7 spinous process.

2. Landmark for Lumbar Puncture

• Case: A clinician needs to perform lumbar puncture in an adult.

• Q: Which vertebral level is located by joining iliac crests?
  → L4 vertebra (intercristal line).

3. Caudal Epidural Anesthesia

• Case: An anesthetist introduces needle through sacral hiatus.

• Q: What is the surface landmark for sacral hiatus?
  → Depression below sacral cornua at lower end of sacrum.

4. Herpes Zoster (Shingles)

• Case: A 60-year-old develops painful vesicular eruptions along one strip of back skin.

• Q: Which structure is infected?
  → Dorsal root ganglion of spinal nerve.

5. Back Acne and Sebaceous Cysts

• Case: A young man has multiple pustules and nodules on upper back.

• Q: Why is skin of back prone to such lesions?
  → Rich in sebaceous glands.

6. Accessory Nerve Injury

• Case: After neck dissection, patient cannot shrug shoulders.

• Q: Which muscle is paralyzed?
  → Trapezius.

7. Thoracodorsal Nerve Injury

• Case: Following axillary surgery, patient has difficulty in climbing or rowing.

• Q: Which muscle is paralyzed?
  → Latissimus dorsi.

8. Dorsal Scapular Nerve Injury

• Case: A soldier develops lateral displacement of scapula after nerve injury.

• Q: Which muscles are weakened?
  → Rhomboids, levator scapulae.

9. Lumbago

• Case: A middle-aged man develops acute back pain after lifting heavy weight.

• Q: Which muscles are commonly strained?
  → Erector spinae group.

10. Herniated Lumbar Disc

• Case: A patient presents with radiating pain from back to lower limb.

• Q: What causes this?
  → Herniation of lumbar intervertebral disc compressing spinal nerve roots.

11. Tuberculosis of Spine (Pott’s Disease)

• Case: A child presents with kyphotic deformity of back.

• Q: What is the underlying pathology?
  → Tuberculosis of vertebrae with collapse.

12. Scoliosis

• Case: A teenage girl has lateral curvature of spine with rotation.

• Q: What is this deformity called?
  → Scoliosis.

13. Spinal Cord Injury Landmark

• Case: A stab wound at level of T7 vertebra damages spinal cord.

• Q: Which surface landmark corresponds to T7?
  → Inferior angle of scapula.

14. Muscle Flap Surgery

• Case: A breast cancer patient undergoes reconstructive surgery using a back muscle.

• Q: Which muscle is used?
  → Latissimus dorsi.

15. Reflex Spasm of Back Muscles

• Case: A patient with vertebral fracture develops rigid back muscles.

• Q: Why?
  → Reflex spasm of intrinsic muscles to stabilize spine.