Spine Series: Red Flags You Cannot Miss

In the world of spinal surgery, the stakes are incredibly high. While a missed ankle fracture is a nuisance, a missed spinal emergency is a catastrophe. It can result in permanent paraplegia, loss of bladder/bowel control, and a lifetime of disability for the patient (and litigation for the surgeon).

This guide focuses on the "Big Three" spinal emergencies that every orthopaedic surgeon—regardless of subspecialty—must be able to recognize and act upon instantly: Cauda Equina Syndrome, Metastatic Spinal Cord Compression, and Spinal Infection.

Visual Element: An infographic of the "Spinal Red Flags" checklist, categorized by Pathology.

1. Cauda Equina Syndrome (CES)

Anatomy Review

The spinal cord in adults typically terminates at the L1-L2 level (the conus medullaris). Below this, the spinal canal is filled with the nerve roots of L2-S5, resembling a horse's tail (cauda equina). These roots supply the lower limbs, the bladder (detrusor), the anal sphincter, and perineal sensation.

Classification: The Window of Opportunity

• CES-Incomplete (CESI): The patient has urinary difficulty (altered sensation, poor flow, need to strain) but retains voluntary control. They do not have painless retention/overflow.
  • Action: Operate immediately. This is the golden window to save bladder function.
• CES-Retention (CESR): The patient has painless urinary retention and overflow incontinence. The bladder is paralyzed.
  • Prognosis: Significantly worse. Even with surgery, bladder recovery is unpredictable.

Cardinal Features (The "5 Ps" of CES)

1. Pain: Severe back pain and bilateral leg pain (sciatica).
2. Perineal Anaesthesia: Numbness in the saddle area (S2-S5). Ask: "Does it feel different when you wipe?"
3. Pee (Bladder Dysfunction): Retention or incontinence.
4. Poop (Bowel Dysfunction): Incontinence or loss of anal tone.
5. Power/Paralysis: Bilateral lower limb weakness (LMN signs).

Management

• Imaging: Urgent MRI (Whole spine is ideal, but Lumbar mandatory). Do not wait for "morning lists."
• Surgery: Wide posterior decompression (laminectomy) and discectomy.
• Timing: The literature (Todd et al.) suggests surgery within 24-48 hours of onset of symptoms offers the best chance of recovery. However, "the sooner the better" is the safest medicolegal stance.

Clinical Pearl: Post-Void Residual. If in doubt, scan the bladder. A residual volume >500ml is highly suggestive of CESR.

2. Metastatic Spinal Cord Compression (MSCC)

The spine is the most common site for skeletal metastases. 5-10% of all cancer patients will develop spinal mets.

Pathophysiology

Tumour deposits in the vertebral body expand posteriorly into the canal, compressing the thecal sac.

• Venous Congestion: The first stage. Edema causing cord ischemia. Reversible.
• Arterial Occlusion: The late stage. Cord infarction. Irreversible.

The "Sins" of the Spine (Origins)

• Breast
• Lung
• Thyroid
• Kidney (Renal)
• Prostate
• (And Myeloma/Lymphoma)

Clinical Features

• Pain: The earliest symptom (95%). Constant, progressive, and worse at night.
• Weakness: Upper Motor Neuron (UMN) signs below the level (Hyperreflexia, Clonus, Babinski +ve).
• Sensory Level: A distinct band where sensation changes.

The Emergency Protocol

1. Steroids: Dexamethasone 16mg IV stat, then 8mg BD. This reduces vasogenic edema and can temporarily reverse neurological deficit.
2. MRI: Whole spine MRI (30% of patients have non-contiguous lesions).
3. The Patchell Trial: The landmark study (2005) proved that Surgery + Radiotherapy is superior to Radiotherapy alone for patients with a single area of compression who are ambulatory (or recently non-ambulatory).

Visual Element: Flowchart of the NIMS (Neurological, Oncological, Mechanical, Systemic) framework for decision making.

3. Spinal Infection (Discitis/Osteomyelitis)

A subtle killer. Often missed because the neurology comes late.

Risk Factors

• Diabetes.
• Immunosuppression.
• IV Drug Use.
• Recent invasive procedure (even a dental checkup).

Presentation

• Back Pain: Severe, unrelenting, mechanical.
• Fever: Present in only 50% of cases! Do not rule it out because the patient is afebrile.
• Neurology: Late sign (Epidural abscess compressing the cord).

Workup

• Labs: CRP and ESR are almost always elevated. WCC can be normal.
• MRI: Gold standard. Shows T2 hyperintensity in the disc and endplates.
• Biopsy: CT-guided biopsy is mandatory before starting antibiotics (unless the patient is septic/unstable) to identify the organism.

4. The Systematic Approach to Red Flags

When taking a history for "Back Pain," you are effectively a detective hunting for red flags.

History Red Flags

Examination Red Flags

• Neurology: Any motor grade <5/5.
• Tone: Increased tone/clonus (Cord compression).
• PR Exam: Loss of tone or sensation (CES).
• Percussion Tenderness: Highly specific for infection or fracture.

5. Viva Scenarios: What to Say

Scenario: "A 65-year-old male with known prostate cancer presents with back pain and leg weakness."

The Pass Answer:

"This is a spinal emergency—Metastatic Cord Compression—until proven otherwise.

1. I would perform a focused neurological exam to identify a sensory level and UMN signs.
2. I would administer Dexamethasone 16mg immediately.
3. I would order an urgent Whole Spine MRI.
4. I would consult the Spine and Oncology teams.
5. If he has a single level of compression and is fit, surgery is indicated (Patchell Trial)."

Scenario: "A 30-year-old IV drug user has back pain and fever."

The Pass Answer:

"I suspect Vertebral Osteomyelitis or Epidural Abscess.

1. I would check inflammatory markers (CRP/ESR) and Blood Cultures.
2. I would order an MRI with Contrast.
3. Crucially, I would withhold antibiotics until deep tissue samples (biopsy) are obtained, unless he is septic, to ensure we treat the specific organism."

Conclusion

Red flags are called "red" for a reason—they demand a full stop. Do not pass Go, do not prescribe physio.

• Suspect the worst.
• Image immediately (MRI).
• Escalate early.

In the spine, time is function.