How Much Cement Is Enough in Kyphoplasty? Why “Rim to Rim” Isn’t the Goal.
- Posted on: Jun 4 2026
You’ve probably seen the fluoroscopy screenshots on social media: cement filling from one cortical wall to the other, with a caption reading something like “nice full fill.” I understand the impulse. It looks complete. It looks decisive. But the evidence does not support fill volume as the primary success metric in kyphoplasty, and in real practice, the factors governing how much cement can be safely placed are considerably more complex than the image suggests.
What the Literature Actually Says About Volume
The relationship between cement volume and clinical outcome has been studied repeatedly, and the findings are more nuanced than a simple “more is better” conclusion.
The SWISSspine nationwide registry, one of the largest real-world datasets on balloon kyphoplasty, identified cement volume as an important modifiable predictor of pain relief, with higher cement volumes associated with greater improvement on VAS pain scores.1 That finding matters. Cement volume is not irrelevant. But it should not be interpreted as permission to chase a fluoroscopic “full fill” at all costs.
Other studies complicate the story. In a 2020 retrospective series of 136 patients undergoing kyphoplasty, Self and colleagues found that patients improved significantly in pain, disability, and quality-of-life measures, but the total volume of injected cement was not associated with improvement in VAS, Roland-Morris Disability Index, or EQ-5D scores.2 In other words, patients improved after kyphoplasty, but larger cement volumes did not explain who improved more.
A more recent 2024 study of 368 patients and 802 treated vertebrae found that larger cement volumes during balloon-assisted kyphoplasty were associated with greater correction of local kyphosis and a higher rate of adjacent-level vertebral compression fractures in the thoracic spine. That relationship was not seen in the lumbar spine.3 This moves the discussion away from a single universal target volume and toward anatomic context: thoracic and lumbar vertebrae do not behave identically, and aggressive correction or larger cement volumes may carry different biomechanical consequences depending on level.
So the literature does not support a simplistic rule that more cement automatically produces a better kyphoplasty result. A more defensible reading is this: cement volume matters, but only as one part of a larger biomechanical and clinical picture. Vertebral level, fracture morphology, cement distribution, height restoration, leakage risk, and adjacent-level biomechanics all matter.
That is why the goal should not be rim-to-rim cement fill. The goal should be enough cement to stabilize the painful fracture safely, with distribution that supports the fractured trabecular architecture, without forcing cement into regions where the risk-benefit calculation turns unfavorable.
What Actually Limits Fill in the Real World
Three factors govern how much cement can be safely placed, and none of them tend to appear in the social media post.
Fracture Morphology
An acute fracture with preserved endplates and mobile fragments is a very different problem than a chronic compression fracture with a vacuum cleft, sclerotic margins, and established intravertebral pseudarthrosis. The cavity created by the balloon, and the cavity that existed before the procedure began, determines where cement can and cannot travel. The preoperative CT scan often tells you more about expected cement distribution than any target volume chosen beforehand.
Fracture severity also appears to interact with cement distribution and early pain response. In other words, the same cement volume may behave differently depending on whether the vertebra is mildly compressed, severely collapsed, sclerotic, mobile, or clefted. The vertebral body is not an empty box waiting to be filled. It is a fractured biological structure with its own architecture, constraints, and escape routes.
Cement Dynamics
Extravasation is not purely a volume phenomenon. It is also a viscosity-and-timing phenomenon. Cement injected during the appropriate working phase, under controlled pressure and continuous fluoroscopic monitoring, behaves very differently from cement pushed aggressively to achieve a cosmetic endpoint.
Posterior cortical wall integrity, venous anatomy, fracture configuration, and endplate condition all interact with cement viscosity at the moment of injection. A perfectly acceptable cement volume in one vertebra may be excessive in another. This is why the decision to continue injecting should be based on cement behavior, distribution, and safety, not a predetermined number alone.
The Open-Pack Decision
This rarely appears in the published literature, but every physician who performs a meaningful volume of kyphoplasty procedures encounters it regularly. Once the first cement pack is in place and approaching its setting phase, the decision to open a second pack is not trivial.
The cannula is embedded within bone surrounded by partially hardening cement. There is a real time constraint, an economic consideration, and most importantly a patient safety calculation involving procedural duration and anesthesia exposure. The operator who always achieves a predetermined target volume either has never encountered an early-setting batch of cement or is not fully describing the realities of day-to-day practice.
A Note on Approach and Its Honest Limitations
I perform the majority of my kyphoplasty procedures using a unipedicular approach with the Stryker system. The advantages are real: a single entry point, reduced soft tissue disruption, and shorter procedure times.
So is the limitation. Ipsilateral peripedicular fill can sometimes be challenging, and the contralateral trabecular space, particularly in larger lumbar vertebrae, may not be addressed as completely as with a bipedicular approach. Published data suggest that insufficient or asymmetric cement distribution after unilateral kyphoplasty can matter clinically, and that a second injection to correct inadequate distribution may reduce subsequent vertebral re-collapse rates in selected cases.4
That is a tradeoff worth understanding, not something that should be hidden behind a carefully framed fluoroscopy image.
When Standard Kyphoplasty Is Not the Right Tool
Fracture morphology sometimes tells you before the procedure even begins that standard balloon kyphoplasty may struggle to achieve optimal cement distribution.
A vertebra plana pattern, characterized by near-complete vertebral body collapse with minimal remaining cavity, is one situation where I may favor vertebroplasty over kyphoplasty, prioritizing cement infiltration rather than attempting height restoration that is unlikely to be meaningfully recovered.
For fractures where restoration of vertebral height remains important and where a balloon-created cavity may partially collapse before cement curing, SpineJack offers a different biomechanical strategy. The titanium implant maintains reduction throughout cement delivery, a design concept that has been directly compared with balloon kyphoplasty in biomechanical studies.5
When cement viscosity control is the primary concern, particularly in fractures where leakage risk is elevated, RF-targeted vertebral augmentation may offer more direct control over cement viscosity during delivery than conventional passive mixing techniques. RF-targeted vertebral augmentation offers a different approach to cement delivery, emphasizing controlled cement viscosity and targeted distribution. Clinical studies have demonstrated favorable pain and functional outcomes when compared with traditional balloon kyphoplasty, although fracture morphology and operator technique remain major determinants of outcome.6
The point is not that one tool universally wins. The point is that fracture morphology should determine technique selection, not the other way around.
The Honest Standard
A common misconception is that the fluoroscopic image obtained at the end of the procedure represents the entirety of procedural success. In reality, fluoroscopy captures cement location. It does not fully capture fracture stability, load transfer characteristics, trabecular interdigitation, adjacent-level biomechanics, or the patient’s eventual clinical response. Those outcomes emerge over the days and weeks that follow.
The goal is not rim-to-rim fill. The goal is adequate structural stabilization, acceptable cement distribution, minimal or no extravasation, and a procedural risk profile appropriate for the patient sitting in front of you.
Sometimes that means stopping at 3 mL. Sometimes fracture morphology and cement behavior allow substantially more. The fluoroscopy image tells part of the story. The patient’s outcome two weeks later tells the rest.
References
1. Röder C, Boszczyk B, Perler G, Aghayev E, Külling F, Maestretti G. Cement volume is the most important modifiable predictor for pain relief in BKP: results from SWISSspine, a nationwide registry. Eur Spine J. 2013;22(10):2241-2248. doi:10.1007/s00586-013-2869-3.
2. Self M, Mooney J, Amburgy J, Agee B, Schoel L, Pritchard P, Chambers M. Analysis of injected cement volume and clinical outcomes following kyphoplasty for vertebral compression fractures. Surg Neurol Int. 2020;11:56. doi:10.25259/SNI_22_2020.
3. Adida S, Taori S, Wong VR, Tang A, Sefcik RK, Zhang X, et al. Analysis of injected cement volume and clinical outcomes following balloon-assisted kyphoplasty in a series of 368 patients. Clin Neurol Neurosurg. 2024;243:108367. doi:10.1016/j.clineuro.2024.108367.
4. Xue Y, Zhang J, Zhang Z, Dai W, Ma C. Clinical outcomes with second injection after insufficient bone cement distribution in unilateral kyphoplasty for osteoporotic vertebral compression fracture. J Orthop Surg Res. 2023;18:530. doi:10.1186/s13018-023-03968-2.
5. Rotter R, Schmitt L, Gierer P, Schmitz KP, Noriega D, Mittlmeier T, et al. Minimum cement volume required in vertebral body augmentation: a biomechanical study comparing the permanent SpineJack device and balloon kyphoplasty in traumatic fracture. Clin Biomech. 2015;30(7):720-725. doi:10.1016/j.clinbiomech.2015.04.012.
6. Bornemann R, Jansen TR, Kabir K, et al. Comparison of radiofrequency-targeted vertebral augmentation and balloon kyphoplasty in patients with vertebral compression fractures. Orthop Rev (Pavia). 2015;7(1):5588. PMID: 25694880.
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