What are vertebral plastics?

What Are Vertebral Plastics (Vertebral Augmentation Procedures)

Vertebral plastics—more accurately termed vertebral augmentation procedures—are minimally invasive, image-guided techniques that involve percutaneous injection of bone cement (typically polymethylmethacrylate or PMMA) into fractured vertebral bodies to provide pain relief and stabilization. 1

Two Main Types of Vertebral Augmentation

Vertebroplasty

• Direct injection of bone cement into the vertebral body without prior cavity creation 1
• The cement is injected percutaneously under image guidance to stabilize the fractured vertebra 2
• Generally performed on an outpatient or short-stay basis 3

Kyphoplasty

• Involves inflation of a percutaneously delivered balloon (bone tamp) in the vertebral body, followed by cement injection into the cavity created by the balloon 1
• Often referred to as "balloon-assisted vertebroplasty" 1
• The balloon theoretically restores vertebral body height while creating a low-pressure cavity for cement placement 1
• The FDA-approved balloon device (KyphX Inflatable Bone Tamp) is indicated for fracture reduction and void creation in cancellous bone 1

Primary Clinical Indications

Both procedures are most commonly used to treat painful vertebral compression fractures (VCFs) that have failed conservative medical therapy, including: 1, 3

• Osteoporotic compression fractures (most common indication) 2, 4
• Malignant/neoplastic fractures from metastatic disease 1, 5
• Painful vertebral hemangiomas 3
• Potentially traumatic VCFs (emerging indication) 3

Mechanism of Action and Clinical Benefits

Pain Relief and Functional Improvement

• The exact mechanism is unknown, but stabilization of the fracture is postulated to lead to analgesia 3
• Both procedures provide substantial pain relief and improved mobility in the great majority of patients 1
• Vertebroplasty has been shown to decrease pain, improve mobility, and positively affect quality of life across all five domains of validated quality-of-life questionnaires 1
• Kyphoplasty demonstrates similar quality-of-life improvements 1

Mortality and Morbidity Benefits

• These procedures reduce complications associated with prolonged bed rest and narcotic analgesia, which is particularly important given that early immobilization complications may result in adverse outcomes from which patients may not recover 1
• For cancer patients, vertebral augmentation provides immediate pain relief, avoids delays in chemoradiation, and may have potential antitumor effects from the bone cement 5

Comparative Effectiveness: Vertebroplasty vs. Kyphoplasty

Clinical Outcomes

• No head-to-head prospective randomized studies have directly compared kyphoplasty with vertebroplasty 1, 6
• Both procedures show equivalent benefit in patient pain relief and mobility at similar complication rates 1
• The consensus position is that kyphoplasty should be considered an alternative procedure to vertebroplasty, with choice based on operator experience or preference 1

Cost Considerations

• Kyphoplasty is approximately 2.5 times more expensive than vertebroplasty due to additional equipment, anesthesia, and hospital costs 1, 6
• A substantial clinical benefit over vertebroplasty would need to be proven to justify this added expense 1

Cement Leakage Rates

• Vertebroplasty has significantly higher rates of cement leakage (40-72%) compared to kyphoplasty (8-27%), though most leaks are asymptomatic 1, 4
• In vertebroplasty, approximately 3% of cement leaks are symptomatic 4
• Kyphoplasty's balloon inflation theoretically creates a low-resistance cavity allowing more viscous cement placement at lower pressure, reducing leakage risk 1

Safety Profile and Complications

Overall Complication Rates

• Major complications occur in less than 1% of patients treated for osteoporotic compression fractures and in less than 5% of patients with neoplastic involvement 1
• The mortality rate ranges from 0% to 7%, with an overall rate of 0.5% attributable deaths (including pulmonary cement embolus, post-anesthesia chest infections, and sepsis) 1
• Severe complications occur in approximately 2% of patients (symptomatic pulmonary emboli, hemothorax, emergency decompression for hematoma or neuropathy) 1

Specific Risks

• Cement extravasation is the most important source of complications, occurring through venous channels that communicate with epidural space, neural foramina, and paraspinal tissue 1
• Serious but rare complications include spinal cord compression, nerve root compression, venous embolism, pulmonary embolism, and cardiovascular collapse 3
• Asymptomatic cement pulmonary emboli detected by CT occur in up to 26% of patients 1

Adjacent Fracture Risk

• The risk of secondary fractures in adjacent vertebrae is NOT significantly increased by vertebral augmentation compared to conservative treatment 1
• Analysis of 612 patients showed 18.8% developed secondary fractures with conservative treatment versus 19.4% with vertebroplasty (not statistically significant) 1

Materials Used

The primary filling material is polymethylmethacrylate (PMMA) bone cement, though other materials are being developed: 3, 7, 8

• Injectable PMMA (standard)
• Composite bone cements
• Biodegradable bone cements
• Calcium phosphate cements (CPC)
• Calcium sulfates

Common Pitfalls and Important Caveats

• Practice guidelines suggest threshold all-complication rates of 2% for osteoporotic fractures and 10% for neoplastic fractures—rates above these should prompt review of local practice 1
• Patient selection is critical: procedures are indicated when conservative therapy has failed, not as first-line treatment 1, 2
• The presence of severe pain alone is sufficient indication for these procedures in appropriately selected patients, even without documented height loss 5
• For cancer patients, early intervention is warranted as the natural history of vertebral compression fractures is worse due to continued bone loss from tumor invasion 5