Vertebral compression fractures (VCFs) occur when a spinal bone collapses, often causing severe back pain. Causes include osteoporosis, significant trauma, or metastatic disease. Kyphoplasty is a minimally invasive treatment designed to stabilize the fractured vertebra and alleviate pain. The procedure involves inserting a balloon to create a cavity and restore some height before injecting specialized bone cement (PMMA) to act as an internal cast. This technique offers rapid stabilization and pain relief.
The Time Factor: Acute Versus Chronic Fractures
Kyphoplasty suitability is often framed by the fracture’s age, distinguishing between acute and chronic injuries. An acute VCF is less than six to ten weeks old, characterized by instability and biological activity. During this early phase, the vertebral body is relatively soft due to internal edema (fluid from the bone trauma). This flexibility allows the kyphoplasty balloon to more effectively lift the collapsed endplates and restore vertebral height.
A chronic, or “old,” fracture is typically three months or older, a point where the bone has largely settled and begun to consolidate. In this chronic phase, fragments have stabilized in their collapsed position, and internal edema has been replaced by fibrous tissue or partially healed bone. While this makes mechanical height restoration significantly more challenging, it does not automatically disqualify the fracture from treatment. The primary goal shifts from correcting spinal alignment to stabilizing residual micro-motion within the fracture site for pain relief.
Evaluating Chronic Fractures for Kyphoplasty Suitability
Determining if an old fracture remains the source of pain requires advanced diagnostic evaluation focused on biological activity. Magnetic Resonance Imaging (MRI) is the most sensitive tool, using T2-weighted and short TI inversion recovery (STIR) sequences. These sequences detect residual bone marrow edema (BME), which presents as a bright signal within the fractured bone. Edema presence, even months after injury, strongly indicates the fracture is still biologically active and a likely source of ongoing mechanical pain.
If the MRI shows no significant BME, a Computed Tomography (CT) scan provides detailed information on the bone’s structural integrity. CT scans assess the degree of bone hardening (callus formation) and identify a vacuum phenomenon (gas or fluid within the fracture cleft). A visible vacuum cleft suggests non-union or persistent instability, indicating the fracture is still moving and may be amenable to stabilization. The decision to proceed rests on confirming the chronic fracture remains biologically or mechanically active, making it a treatable pain generator.
Expected Outcomes and Limitations for Older Fractures
When kyphoplasty is performed on older fractures, clinical outcomes differ from acute cases, particularly concerning structural correction. Pain relief remains the most reliable outcome; studies show symptomatic chronic fractures experience significant pain reduction comparable to acute fractures. This relief is achieved through the mechanical stabilization provided by the cement, which immediately fixes the painful micro-motion within the vertebral body.
The primary limitation for chronic VCFs is the minimal potential for restoring vertebral height and correcting spinal curvature. Since the bone has consolidated and healed in its collapsed position, the balloon inflation step is often less effective. Chronic fractures typically achieve much less height restoration than acute fractures. Furthermore, the denser nature of an older fracture may necessitate higher pressure during cement injection. If pain originates primarily from secondary issues, such as muscle strain or adjacent joint arthritis, kyphoplasty may provide less benefit, underscoring the importance of accurate pre-operative diagnosis.