VCFs cause debilitating back pain, and as a result of population aging, the incidence of these fractures increases . Conservative treatment for compression fractures has not been suggested, as it fails to restore the vertebral body to its origin height. Additionally, pain and spinal deformity are not improved or corrected, and the domino effect follows rapidly after the first VCF . This effect is a direct consequence of the mechanical variations that affect the spine when physiological curves are modified . Treatment of VCFs with VP or KP maintains the integrity of adjacent structures and reduces the likelihood of a domino effect ; thus, the role of surgical treatment has increased.
Currently, percutaneous cement augmentation procedures are gaining popularity . VP or KP can provide immediate effective pain relief for patients with VCFs . To date, there have been several papers regarding minimally invasive cement augmentation procedures published. Nevertheless, no study has compared the efficacy and safety of these procedures; therefore, we compared VP, balloon KP, KP with an IVEP, KP with a vessel, and KP with SpineJack, performed via a bipedicular transpedicular approach by the same surgeon in five similar groups of patients.
The VAS is the most common pain measurement method. Several studies have found a significant improvement in pain after VP or KP [14,15]. These results are in line with those of our studies; we found that both VP and KP were effective at reducing pain, as measured by the VAS pain scale 12 months postoperatively. The VAS score was not significantly different between the KP and VP groups at 12 months postoperatively. The results showed that once polymethylmethacrylate (PMMA) was injected into the vertebral body to stabilize the fracture, the pain relief was significantly increased, regardless of the type of surgical intervention.
KP with SpineJack provides the best performance for AVBH restoration 1 year postoperatively. SpineJack is a permeant titanium implant designed to restore vertebral height through an endplate distraction device by expanding like a small jack; it is equipped with a mechanical opening, ensuring a gradual and controlled vertebral fracture reduction. This technique allows good reconstruction of the anterior column and restores vertebral height .
The KA evaluates the reduction in kyphosis. In our study, VP was unfavorable for kyphotic reduction due to the lack of effective strength acting on the upper and lower endplates. VP requires cement injection at higher pressures and hence incurs a higher risk of cement extravasation than KP and merely eliminates the deformity, without reduction of kyphosis [14,17].
Berlemann et al. reported a mean kyphotic reduction of approximately 8° in a group of 27 patients after KP , whereas Theodorou et al. revealed an average KA correction of 9° . Weisskopf et al. showed that the reduction in kyphotic deformity was only achieved in four cases (average, 8.5°) in a 22-patient trial . In contrast, the corrections of KAs in our study were 14.2°, 16.0°, 15.8°, and 14.2° in balloon, IVEP, vessel, and SpineJack KP, respectively, 1 year after surgical treatment; our kyphotic correction was substantially higher than those reported in previous studies. We were unable to discriminate between the acute VCFs from old VCFs using only conventional two-plane X-ray in an erect position instead of MRI. In the acute or subacute phase of VCF, edema was noted during replacement of the normal vertebral body bone marrow in a benign compression fracture, resulting in hypointensity on T1-weighted images and hyperintensity on T2-weighted images. The nonunion VCF presented a confined high intensity or a diffuse low-intensity area on T2-weighted MRI, found to be of significant importance [20,21]. The more recent the fracture, the better the kyphotic reduction after KP . In contrast to previous studies, patients with a diagnosis of acute, subacute, or nonunion VCFs underwent surgical treatment in our study. Therefore, we gained better satisfaction from patients and better postoperative correction of the kyphotic deformity.
Of the five groups, adjacent VCF episodes occurred most commonly in the VP group. KP requires a larger injection pressure, creating a cancellous fill effect with PMMA, finally leading to better spinal biomechanical stability; as a result, the risk of secondary vertebral fractures decreases .
To date, it is not clear how new vertebral fractures occur in adjacent vertebrae. Some studies have shown that the pressure on adjacent vertebrae was increased as a result of injected cement . Both VP and KP reduced swelling of the vertebral endplate and vertebral joint mobility, causing swelling of the adjacent vertebrae and increasing the risk of adjacent vertebral fracture . In this study, we found that the highest rate (17%) of adjacent VCFs occurred in the VP group.
In the KP group, although the null hypothesis was not rejected, the difference may be related to the small amount of data. It appeared that the prevalence of adjacent VCFs within 1 year was lowest in the KP with IVEP group. Generally, KP with balloon, vessel, or SpineJack, as well as VP, are completed by filling the vertebral body with PMMA; only KP with an IVEP is associated with bone healing. The healed vertebrae following IVEP treatment have similar bone mineral densities to the adjacent vertebrae. The fractured vertebrae filled with PMMA was stiffer than the adjacent level vertebrae, explaining the lower adjacent VCF rate in the KP with IVEP group.
Complications of percutaneous VP or KP are fairly common, and in most cases, they are asymptomatic [25,26]. The most common complications are cement leakage due to the fact that osteoporosis increases the vulnerability of the vertebral bone structure; extraction of the endplate when performing KP may further displace the fractured fragment [27,28], which can migrate into veins, paravertebral soft tissue, intervertebral discs, or the spinal canal, affecting the foraminal area or epidural space. In the VP and balloon KP groups, there was a higher percentage of cement leakage, 24 cases (16 asymptomatic, and 8 symptomatic) and 30 cases (23 asymptomatic, 7 symptomatic), respectively. Cement leakage or implant migration occurred less frequently in the KP with IVEP, vessel, and SpineJack groups.
With VP, the cement was injected into the vertebral body while the PMMA flowed to fill the gaps between fracture fragments. During this step, the less viscous the cement, the more easily it filled defects in the cortex. Additionally, the impaction of the trabecular bone against the surrounding cortical bone reduced the risk of cement penetrating the cortex. Another factor related to the leakage of cement in both VP and KP is the fracture pattern. When the endplates and anterior or posterior wall are not intact, cement leakage occurs more often . Although the number of cement leakages was small and the results inconclusive, the rate of cement leakage was lowest in the KP with SpineJack group. After expanding the implants, we stabilized the fractured vertebra via injection of PMMA bone cement (Cohesion®, Vexim), characterized by its high viscosity; this prevented the occurrence of cement leakage.
It was previously thought that vesselplasty was a safe surgical treatment due to the absence of potentially fatal cement leakage out of the vertebral body and into the spinal canal ; however, one of our patients who underwent vesselplasty experienced cement leakage. In a 2015 study, a certain amount of cement leakage occurred during cement injection. This major complication of KP with a vessel resulted in symptomatic, irreversible sequelae, paraplegia due to thermal damage, and spinal nerve compression by the cement, even though an emergent laminectomy was immediately performed .
Some data reported rare complications of VP or KP including infections, epidural hemorrhage, fat embolism, cardiac damage, and arterial or renal embolism [31-35]. Fortunately, we did not observe these during the clinical course of our patients.
Although we present promising results, this study had limitations owing to the rapid pace of innovations regarding spinal implants for VCFs. There are some published studies on innovative spinal implants, including the Vertebral Body Stent®, KIVA® Vertebral Compression Fractures Treatment System, and Osseofix®. While these implants are useful and are reported to be effective for body height restoration , these products have not yet been introduced to our hospital. Therefore, we could not bring these data into our study.
Some researchers might question our choice of implants; however, the patients’ economic conditions were considered as well. The treatments used in this study, listed from the most to least expensive, were KP with SpineJack, KP with an IVEP, vesselplasty, balloon KP, and VP. In clinical practice, we emphasized self-decision-making. Thus, we allowed patients to choose between these treatment methods. In addition, SpineJack implants had not been introduced to our hospital until 5 years prior to this report; therefore, all SpineJack data were collected within 5 years. Moreover, we experienced a tragic episode from cement leakage during vesselplasty; since then, we have not had the confidence to perform this procedure again . For this reason, there was no bias of treatment choice based on disease severity; this was a fully randomized retrospective study.
Despite enrolling 354 patients in our study, which is a relatively large patient sample size in a single-doctor series study, our sample size was insufficient to demonstrate the safety of each group. We restricted the study to a single surgeon to minimize the interoperator variability. The safety and effectiveness of surgery depends on the surgeon’s technique; nevertheless, though we collected the data from a single surgeon over 10 years, the sample size remained insufficient. Thus, given the small sample size, the result for the least amount of cement leakage remains inconclusive. In further studies, we will enroll more patients to evaluate cement leakage rates in KP more accurately with SpineJack, vesselplasty, and IVEP.