Balloon Kyphoplasty

Surgical Indications

Absolute Indications

• Painful vertebral compression fracture with mechanical axial pain correlating to the fractured level
• Subacute fracture (typically less than 3 months) demonstrating bone marrow oedema on MRI STIR or T2 fat-suppressed sequences
• Failure of conservative management including analgesia, bracing and physiotherapy for at least 4-6 weeks
• Pathological fractures due to myeloma, lymphoma or metastatic disease with mechanical pain and limited life expectancy where stabilisation improves quality of life

Relative Indications

• Progressive kyphosis with sagittal imbalance and secondary pain
• Multiple contiguous fractures where staged augmentation may prevent further collapse
• Patients with severe osteoporosis in whom prolonged bracing is poorly tolerated

Contraindications

Absolute:

• Active spinal infection or osteomyelitis at the target level
• Neurological deficit attributable to the fracture (cord or cauda equina compression requiring decompression)
• Burst fracture with significant retropulsion and canal compromise
• Coagulopathy that cannot be corrected

Relative:

• Chronic fracture without oedema on MRI (pain relief rates drop below 50 percent)
• Greater than 50 percent vertebral height loss with severe endplate fragmentation (technical difficulty)
• Allergy to PMMA cement components

Evidence Base

Balloon kyphoplasty and vertebroplasty both provide rapid pain relief in appropriately selected patients. The key distinction is that kyphoplasty creates a cavity with the inflatable bone tamp before cement injection. This permits use of higher-viscosity cement at lower pressure and aims for partial height restoration and kyphosis correction.

Landmark trials (FREE, VERTOS II, KAST) demonstrated significant pain and function improvement versus conservative care at 1 month, with benefits persisting to 12-24 months in many patients. Direct comparisons with vertebroplasty show similar pain scores but modestly greater height restoration and kyphosis correction with kyphoplasty, at the cost of slightly longer operative time. Cement leakage rates are lower with kyphoplasty (approximately 5-10 percent versus 20-30 percent in vertebroplasty) but are not eliminated. Adjacent-level fracture rates are comparable between the two techniques.

Key Evidence

Relevant Spinal Anatomy for Kyphoplasty

Vertebral Body and Pedicle Relationships

The vertebral body is a cylindrical structure with thick cortical walls and trabecular bone internally. The pedicles are short, stout projections arising from the posterolateral body. In the thoracic spine the pedicles are narrower and more medially directed; in the lumbar spine they are wider and more sagittally oriented. The transpedicular corridor is the safest route to the vertebral body because it avoids the exiting nerve root (which lies in the foramen inferior to the pedicle) and the thecal sac (medial to the pedicle).

Critical Bony Landmarks

• Pedicle: the starting point is the intersection of the transverse process and the superior articular facet (mamillary process in lumbar). The entry point lies at the 10 o'clock (left) or 2 o'clock (right) position on the pedicle shadow on AP fluoroscopy.
• Posterior wall: the posterior cortical margin is the critical depth limit. On lateral fluoroscopy the cannula tip must reach but not breach the posterior wall before entering the body.
• Anterior cortex: the anterior wall is the anterior limit for balloon placement and cement fill. Over-advancement risks anterior extravasation or vascular injury.

Vascular Anatomy and Leakage Pathways

The vertebral body is richly vascularised by the basivertebral veins (central posterior) and segmental veins that drain into the azygos/hemiazygos system (thoracic) or inferior vena cava (lumbar). Cement can travel along these veins to produce pulmonary embolism. The disc space above and below is another potential leakage route when endplates are fractured.

Neural Structures at Risk

• Spinal cord (T1-L1): lies immediately medial to the medial pedicle wall. Medial breach places the cord at direct risk.
• Thecal sac and cauda equina (below L1): similar medial risk.
• Exiting nerve root: lies in the foramen immediately inferior to the pedicle; inferior breach during trajectory planning risks root injury.

Sagittal Alignment Considerations

Each augmented level contributes to overall sagittal balance. A single-level kyphoplasty that restores 5 mm of anterior height can improve local kyphosis by 4-7 degrees. Multiple levels compound the effect on global sagittal vertical axis and should be planned with standing radiographs.

Positioning and Preparation

Patient position: Prone on a radiolucent table with chest and pelvic supports allowing free abdominal excursion. The spine is placed in slight extension to facilitate endplate elevation. Arms are abducted or tucked. General anaesthesia or conscious sedation with local infiltration is used according to patient tolerance and fracture acuity.

Imaging setup: High-quality biplanar fluoroscopy (or CT navigation when available) is mandatory. True AP and lateral projections must be obtained before skin preparation. The C-arm is positioned to allow unobstructed AP (tube under table) and lateral views without moving the patient.

Antibiotic prophylaxis: Single-dose cefazolin (or vancomycin if penicillin-allergic) at induction. Consider vancomycin powder in the wound in high-risk patients.

Consent: Discuss cement leakage (5-10 percent), neurological injury (less than 1 percent), adjacent fracture (10-20 percent), infection (less than 1 percent), and the possibility of incomplete pain relief.

Step-by-Step Operative Technique

Step 1: Level Localisation and Trajectory Planning

Obtain true AP and lateral fluoroscopic images. Identify the target vertebra by counting from a known landmark (usually L5 or S1) and confirm with preoperative MRI. Mark the skin entry points 1-2 cm lateral to the pedicle shadow on AP view, angled toward the pedicle axis.

Step 2: Bilateral Transpedicular Cannulation

Infiltrate skin and periosteum with local anaesthetic. Advance 11- or 13-gauge Jamshidi needles through the pedicles under continuous AP fluoroscopy. Once the needle tip reaches the medial pedicle wall on AP, switch to lateral view to confirm the tip has passed the posterior wall before advancing further into the body.

Advance to the posterior third of the vertebral body. Remove the trocar and insert a guidewire or working cannula. Repeat on the contralateral side. Confirm both cannulas lie within the body on AP and lateral views.

Step 3: Cavity Creation with Inflatable Bone Tamp

Insert the deflated balloon tamp through each working cannula and advance to the anterior third of the body. Inflate the tamp slowly in 0.5 mL increments while monitoring endplate position on lateral fluoroscopy. Typical inflation volumes are 2-4 mL per side depending on vertebral size. Stop when endplates are elevated or maximum pressure (usually 300-400 psi) is reached.

Deflate and remove the tamp, leaving a contained cavity.

Step 4: PMMA Cement Preparation and Injection

Mix high-viscosity PMMA cement according to manufacturer instructions. Allow it to reach a toothpaste-like consistency (typically 4-6 minutes after mixing) before injection. Load into the delivery system.

Under continuous lateral fluoroscopy, inject cement slowly through both cannulas simultaneously or sequentially. Fill the anterior two-thirds to three-quarters of the vertebral body. Watch for any posterior wall breach, venous filling or disc-space extravasation. Stop injection immediately if any of these occur.

Step 5: Verification and Closure

Obtain final AP and lateral images to confirm cement position and distribution. Remove cannulas while cement is still soft to avoid pulling cement tracks. Close skin with absorbable sutures or adhesive strips. No drain is required.

Implants and Fixation

The only implant is PMMA bone cement (typically 3-6 mL per level). No metallic implants are used. The cement interdigitates with trabecular bone and provides immediate stabilisation through mechanical interlock once cured.

Post-operative Protocol

Immediate Phase (Day 0-1)

• Mobilisation: Patients are mobilised as tolerated within 2-4 hours of the procedure. No bracing is required.
• Analgesia: Paracetamol, NSAIDs (if renal function allows) and short course of weak opioid if needed. Most patients report substantial reduction in pre-operative pain within 24 hours.
• Imaging: Standing radiographs at 4-6 weeks to assess alignment and adjacent levels.

Return to Function

• Light activities: Immediate
• Driving: When comfortable (usually 3-7 days)
• Heavy lifting: Avoid for 6 weeks
• Return to work: Sedentary work within 1 week; manual work 4-6 weeks

Osteoporosis Management

All patients require formal osteoporosis assessment and treatment initiation or optimisation. This includes:

• DEXA scan if not recent
• Calcium and vitamin D supplementation
• Antiresorptive or anabolic therapy according to guidelines and fracture risk
• Fall-prevention programme

Special Case: Pathological Fractures (Tumour)

Indications and Modifications

• Patients with limited life expectancy and mechanical pain from myeloma, lymphoma or solid tumour metastases are excellent candidates.
• Biopsy should be performed at the time of cannulation if the diagnosis is uncertain.
• Cement volume may be smaller; the goal is stabilisation and pain relief rather than maximal height restoration.
• Consider additional posterior stabilisation if there is significant instability or neurological compromise.

Outcomes

• Pain relief in 70-85 percent of patients
• Improved mobility and quality of life in the palliative setting
• Cement leakage rates similar to osteoporotic fractures but clinical consequences may be greater if tumour has eroded the posterior wall

Special Case: Multiple-Level Augmentation

Staged procedures (two levels per session) are preferred over single-session three-or-more-level augmentation to limit cement load and operative time. When multiple contiguous levels require treatment, plan the order from caudal to cranial and reassess alignment after each stage.