5.1 Cervical & Lumbar Spondylosis, Degenerative Disc Disease & Herniation

Cervical & Lumbar Spondylosis, Degenerative Disc Disease & Herniation

Clinical Core Concept: Degenerative spinal disorders represent a leading cause of chronic disability and surgical intervention in adult orthopaedics. The orthopaedic nurse must master the neuroanatomical mapping of cervical and lumbar nerve roots, differentiate Lower Motor Neuron (radiculopathy) from Upper Motor Neuron (myelopathy) compression patterns, and recognize provocative physical examination signs that guide conservative and operative pathways.

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1. Functional Anatomy & Degenerative Disc Cascade

The intervertebral disc is a specialized avascular, fibrocartilaginous structure comprising three distinct functional zones:

1. Nucleus Pulposus: Central gelatinous core composed predominantly of water ($70\text{--}85%$, declining with age), type II collagen fibrils, and hydrophilic proteoglycan aggregates (aggrecan). It distributes axial compressive loads isotropically.
2. Annulus Fibrosus: Peripheral concentric ring structure consisting of $15\text{--}25$ dense lamellae of type I collagen oriented at alternating $30^\circ$ angles to withstand torsional, shear, and tensile forces.
3. Cartilaginous Endplates: Thin ($0.5\text{--}1\text{ mm}$) layers of hyaline cartilage bonded to the superior and inferior vertebral body bone. They serve as the critical semipermeable vascular interface through which the avascular disc receives glucose, oxygen, and nutrients via passive diffusion.

                    INTERVERTEBRAL DISC ARCHITECTURE
  ┌─────────────────────────────────────────────────────────────────┐
  │               Vertebral Body (Cancellous Bone)                  │
  ├─────────────────────────────────────────────────────────────────┤
  │        Cartilaginous Hyaline Endplate (Nutrient Diffusion)      │
  │  ┌───────────────────────────────────────────────────────────┐  │
  │  │   Annulus Fibrosus (Type I Collagen Concentric Lamellae)  │  │
  │  │  ┌─────────────────────────────────────────────────────┐  │  │
  │  │  │                  Nucleus Pulposus                   │  │  │
  │  │  │     (Type II Collagen, Aggrecan, Water Matrix)     │  │  │
  │  │  └─────────────────────────────────────────────────────┘  │  │
  │  │   Annulus Fibrosus (Alternating 30° Ply Tensile Rings)    │  │
  │  └───────────────────────────────────────────────────────────┘  │
  │        Cartilaginous Hyaline Endplate (Nutrient Diffusion)      │
  ├─────────────────────────────────────────────────────────────────┤
  │               Vertebral Body (Cancellous Bone)                  │
  └─────────────────────────────────────────────────────────────────┘

The Kirkaldy-Willis Degenerative Cascade

Degeneration of the spinal motion segment (comprising two adjacent vertebrae, the intervening disc, and bilateral posterior facet joints) progresses through three chronological, overlapping phases:

• Phase 1: Dysfunction (Ages 20–40): Repetitive microtrauma and progressive chondrocyte senescence lead to proteoglycan breakdown, desiccation (loss of hydration), and circumferential tears in the outer annulus fibrosus. Concurrently, synovitis and capsular stretching develop in the posterior facet joints, producing localized axial back or neck pain without gross mechanical instability.
• Phase 2: Instability (Ages 35–60): Radial fissures coalesce across the full thickness of the annulus. Disc height decreases, causing laxity of the anterior and posterior longitudinal ligaments and facet joint capsules. Abnormal segmental translation, rotational hypermobility, and internal disc disruption occur, predisposing to acute disc herniation.
• Phase 3: Stabilization (Ages 60+): Progressive osteogenesis and periosteal reaction form marginal traction osteophytes and facet hypertrophic bone spurs. Fibrosis of the disc space and progressive spontaneous osteophytic ankylosis stiffen the motion segment. While mechanical instability decreases, osteophyte overgrowth and disc collapse severely narrow the central canal, lateral recesses, and neural foramina, leading to fixed spinal stenosis.

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2. Morphology & Classification of Disc Herniation

Disc herniation occurs when mechanical degradation of the annulus fibrosus permits displacement of nucleus pulposus tissue beyond the physiologic margins of the intervertebral disc space. The North American Spine Society (NASS) and American Academy of Orthopaedic Surgeons (AAOS) standardize herniation nomenclature:

                     DISC HERNIATION MORPHOLOGY
   1. BULGE               2. PROTRUSION          3. EXTRUSION           4. SEQUESTRATION
  ┌──────────────┐       ┌──────────────┐       ┌──────────────┐       ┌──────────────┐
  │  (=========) │       │  (====(==)   │       │  (====( ==)  │       │  (====)  *   │
  │  Circumfer.  │       │ Base > Dome  │       │ Dome > Base  │       │ Free Detached│
  │  Extension   │       │ Contained    │       │ Transannular │       │ Fragment     │
  └──────────────┘       └──────────────┘       └──────────────┘       └──────────────┘

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3. Cervical Radiculopathy: Anatomic Mapping & Physical Examination

Cervical radiculopathy arises from compression and chemical irritation (mediated by phospholipase A2, TNF-alpha, and IL-6) of a cervical spinal nerve root. In younger individuals ($<40$), posterolateral disc herniation is the predominant etiology; in older patients ($>50$), foraminal stenosis from uncovertebral (Luschka) and facet joint osteophytes predominates.

Cervical Exit Rule

In the cervical spine, spinal nerves C1 through C7 exit above their corresponding pedicle (e.g., C6 nerve root exits through the C5–C6 neural foramen). The C8 nerve root exits between the C7 and T1 vertebrae. From T1 downward, spinal nerve roots exit below their matching vertebral pedicle.

Provocative Physical Examination Tests for Cervical Radiculopathy

• Spurling Test (Neck Compression Test): The patient extends the neck and laterally flexes/rotates the head toward the symptomatic extremity while the examiner applies gentle downward axial pressure to the top of the skull. Reproduction of sharp, electric radicular pain radiating down the ipsilateral arm constitutes a positive test (high specificity $\approx 92\text{--}100%$, moderate sensitivity $\approx 30\text{--}50%$) caused by acute narrowing of the neural foramen.
• Shoulder Abduction (Bakody) Sign: The patient actively abducts the symptomatic arm and rests the hand on top of the head. Relief or marked reduction of radicular arm pain indicates a positive sign. This position reduces tension across the lower cervical nerve roots (particularly C5–C6) and decreases venous engorgement in the neural foramen.
• Cervical Distraction Test: With the patient supine, the examiner applies a controlled axial upward traction force ($10\text{--}15\text{ lbs}$) under the occiput and chin. Relief of radicular pain confirms nerve root impingement by temporarily widening the neural foramina.
• Upper Limb Tension Test of Elvey (ULTT): Sequential abduction, external rotation, forearm supination, wrist extension, and contralateral cervical side-bending tension the brachial plexus; reproduction of arm paresthesia confirms peripheral root irritation.

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4. Lumbar Radiculopathy: Localization & Provocative Testing

In the lumbar spine, paracentral (posterolateral) disc herniations compress the traversing nerve root crossing through the lateral recess to exit at the level below. For example, a posterolateral herniation at L4–L5 compresses the traversing L5 nerve root. In contrast, a far lateral (foraminal/extraforaminal) herniation at L4–L5 compresses the exiting L4 nerve root within the foramen.

                  LUMBAR NERVE ROOT COMPRESSION MECHANICS
                        (L4-L5 Disc Herniation Example)
  ┌────────────────────────────────────────────────────────────────────────┐
  │  Pedicle L4 ───────────────────────────── [ Exiting L4 Root ]          │
  │                                                   │ (Compressed ONLY   │
  │                                                   │  by Far Lateral    │
  │                                                   │  Herniation)       │
  │  L4-L5 Intervertebral Disc Space                 ▼                     │
  │  ┌──────────────────────────────────────────────────────────────────┐  │
  │  │ [Posterolateral Disc Herniation] ──> Compresses Traversing L5   │  │
  │  │                                      Root in Lateral Recess      │  │
  │  └──────────────────────────────────────────────────────────────────┘  │
  │  Pedicle L5 ───────────────────────────── [ Traversing L5 Root Exits]  │
  └────────────────────────────────────────────────────────────────────────┘

Provocative Tests for Lumbar Radiculopathy

• Straight Leg Raise (SLR / Lasègue Test): With the patient supine and pelvis stable, the examiner passively elevates the symptomatic leg with the knee fully extended. A positive test reproduces sharp, radiating radicular pain below the knee between $30^\circ$ and $70^\circ$ of hip flexion (stretching the L5 and S1 nerve roots over the herniated disc). Pain at $<30^\circ$ suggests malingering or acute sacroiliac pathology; pain at $>70^\circ$ reflects hamstring tightness.
  • Bragard Sign: Lowering the leg $5^\circ$ below the painful threshold and performing passive ankle dorsiflexion reproduces the radicular pain, confirming dural tension.
• Crossed Straight Leg Raise (Well-Leg Raising / Fajersztajn Test): Passively elevating the asymptomatic (unaffected) leg reproduces radiating radicular pain down the contralateral (symptomatic) limb. This sign is highly specific ($>90%$) for a large paracentral or extruded disc herniation.
• Femoral Nerve Stretch Test (Reverse SLR / Ely Test): With the patient prone, the examiner flexes the knee to $90^\circ$ and extends the hip. Reproduction of pain in the anterior thigh indicates upper lumbar nerve root ($L2, L3, L4$) irritation or high lumbar disc herniation.

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5. Cervical Spondylotic Myelopathy (CSM)

Cervical Spondylotic Myelopathy (CSM) is the most common cause of spinal cord dysfunction in adults over 55 years of age. Unlike radiculopathy (a Lower Motor Neuron disorder of the peripheral nerve root), myelopathy is an Upper Motor Neuron (UMN) disorder resulting from direct mechanical compression and ischemic microvascular disruption of the spinal cord within a stenotic cervical canal ($<10\text{--}12\text{ mm}$ sagittal diameter).

                  RADICULOPATHY VS. MYELOPATHY SPECTRUM
  ┌──────────────────────────────┬───────────────────────────────────────────┐
  │ Feature                      │ Cervical Radiculopathy (LMN)              │
  ├──────────────────────────────┼───────────────────────────────────────────┤
  │ Pathology Location           │ Single spinal nerve root in foramen       │
  │ Reflex Status                │ Hyporeflexia / Diminished DTRs at level   │
  │ Motor Presentation           │ Weakness isolated to specific myotome     │
  │ Pathologic Reflexes          │ Negative (absent Babinski / Hoffmann)     │
  │ Gait Assessment              │ Normal gait mechanics                     │
  ├──────────────────────────────┼───────────────────────────────────────────┤
  │ Feature                      │ Cervical Spondylotic Myelopathy (UMN)     │
  ├──────────────────────────────┼───────────────────────────────────────────┤
  │ Pathology Location           │ Cervical spinal cord within central canal │
  │ Reflex Status                │ Hyperreflexia (3+/4+) below compression   │
  │ Motor Presentation           │ Global bilateral clumsiness, spasticity   │
  │ Pathologic Reflexes          │ Positive Hoffmann, Babinski, Clonus       │
  │ Gait Assessment              │ Spastic, broad-based, ataxic gait         │
  └──────────────────────────────┴───────────────────────────────────────────┘

Clinical Presentation & Cardinal Physical Signs

1. Loss of Manual Fine-Motor Dexterity: Patients report dropping eating utensils, inability to fasten shirt buttons, progressive deterioration of handwriting, and clumsy fingers.
2. Spastic Ataxic Gait: Patients describe a stiff, uncoordinated gait feeling as if they are "walking on cotton" or "walking on pillows." The stance is wide-based with impaired tandem walking.
3. Hoffmann Sign: With the patient's hand relaxed, the examiner stabilizes the proximal interphalangeal joint of the middle finger and sharply flicks the dorsal aspect of the distal phalanx. A positive response is involuntary reflex flexion and adduction of the thumb and index finger (UMN hyperreflexia).
4. Babinski Reflex: Firm stroking of the lateral plantar surface of the foot from heel to base of the toes elicits extensor dorsiflexion of the great toe and fanning of the lesser digits.
5. Finger Escape Sign: The patient is instructed to hold both arms outstretched with palms facing down and fingers tightly adducted for 30 seconds. In positive myelopathy, the small and ring fingers spontaneously abduct and flex within 30 seconds due to intrinsic hand muscle weakness.
6. Sustained Ankle Clonus: Rapid passive dorsiflexion of the ankle produces $>3\text{--}5$ involuntary rhythmic contractions.
7. Inverted Radial Reflex: Tapping the distal brachioradialis tendon produces paradoxical finger flexion with minimal or absent elbow flexion.