The kiva system versus balloon kyphoplasty for vertebral compression fracture: a meta-analysis of randomized control trials

Abstract

Background

Vertebral compression fractures (VCFs) are the most common type of vertebral body fracture. The Kiva VCF Treatment System is a relatively novel technique to manage VCFs. The aim of this study was to compare the efficacy of Kiva versus standard Balloon Kyphoplasty (BK) through evaluation of published randomized controlled trials (RCTs).

Methods

This study was performed following the guidelines for PRISMA. We performed a systematic literature search using PubMed and MEDLINE in June 2023. The search keywords were “Kiva” and “Kyphoplasty” which yielded a total of 112 articles. Outcome measures included pain, measured through the Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI), and cement leakage rates.

Results

Three RCTs were included in this meta-analysis. A total of 468 patients (Kiva=232 patients and BK=236 patients) and 694 fractures (351 treated with Kiva and 343 treated with BK) were included after fulfilling the inclusion criteria. The VAS score in both the Kiva and BK group improved significantly. There was no difference in VAS improvement between the 2 groups (p-value=.84). Of the 694 fractures that were treated procedurally, the Kiva system had significantly less cement leakage than BK (95% CI [-0.89, -0.22], p-value=.00). However, and collectively out of those who had cement leakage, there was only 2 patients (2.1%) developed adverse events of acute paraplegia required reoperation.

Conclusions

This meta-analysis demonstrates that the Kiva system and balloon kyphoplasty are both strong treatment options for the purpose of reducing pain associated with VCFs, whether osteoporotic or metastatic in etiology. However, Kiva system was favorable over balloon kyphoplasty in terms of rates of cement leakage.

Introduction

Vertebral compression fractures (VCFs) commonly occur in patients with osteoporosis and can also arise due to trauma and metastasis. In the United States, out of the 1.5 million osteoporotic fractures yearly, almost half (700,000) are VCFs [1]. However, only around one-third of vertebral fractures are clinically diagnosed; 40%–50% are incidentally discovered during workup for other conditions [2,3].

VCFs can affect a patient’s life negatively in a variety of different ways, including causing severe pain, limitation in daily functions, and resulting in economic and social burden [4,5], and the estimated cost of hospitalization goes up to 20,000 US dollars per patient, adding to the cost of vertebroplasty or kyphoplasty up to 15,000 US dollars per procedure. Multiple VCFs can lead to kyphosis of the spine, which can lead to poor pulmonary function, decreased appetite and/or malnutrition [6]. This leads to increased morbidity and mortality in patients with VCFs, especially older patients.

Treatment methods for VCFs include conservative treatment and surgical treatment. Conservative treatment is generally attempted first and includes bed rest, bracing, and physical therapy and rehabilitation. Additionally, initial treatment is often directed at the underlying etiology of the VCF. For osteoporotic fractures, medical treatments to improve bone density, such as calcium and vitamin D supplementation and either antiresorptive or anabolic agents are frequently utilized. For pathologic VCFs, antineoplastic treatment, which can include systemic and/or radiation therapy is sometimes pursued. Alternatively, surgical treatments have become more frequent in recent years, especially when symptoms persist and worsen [6].

Two common surgical techniques to treat VCFs are vertebroplasty and balloon kyphoplasty. Vertebroplasty involves injection of polymethylmethacrylate (PMMA) into a vertebral body fracture to stabilize it and improve pain [7]. Balloon kyphoplasty (BK) is a procedure which involves inserting an inflatable bone tamp (balloon) into the collapsed vertebral body and then inflating it to restore vertebral body height (Fig. 1). Once the height of the vertebral body is back to normal, the balloon is removed, and that potential space is filled with bone cement [8,9].

Fig. 1.

Illustration of the balloon kyphoplasty (left) versus kiva system (right).

Another novel technique that has been used in recent years for the management of VCFs is the Kiva VCF Treatment System manufactured by IZI Medical (Owings Mills, MD, USA) (Fig. 1). Similar to the BK, it serves to restore the height of compressed vertebral bodies. Kiva utilizes a guidewire that is introduced into the vertebral body via transpedicular approach and is followed by a coiled PEEK implant. This implant can then deliver cement into the vertebral body in a controlled manner. This process reconstitutes vertebral height, prevents cement leakage, and eliminates focal kyphosis caused by the VCF [10,11].

The purpose of this study was to compare the efficacy of Kiva versus BK in the surgical treatment of VCFs through evaluation of existing randomized controlled trials (RCTs) published in the literature.

Methods

Eligibility criteria and information sources

This study was performed following the guidelines for Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We performed a systematic literature search using PubMed and MEDLINE, which was conducted in June 2023. The searching keywords used were “Kiva” and “Kyphoplasty” yielding a total of 112 articles from both databases.

Search strategy and process

RCTs that compared Kiva versus balloon kyphoplasty in the surgical treatment of VCFs were included. Studies were excluded if they were not RCTs, included patients <16 years of age, were commentary or editorial pieces, or did not compare clinical variables. Initially, abstracts and manuscript titles were screened. This was followed by analysis of the full text if a study met inclusion criteria. The full text articles were reviewed by H.F. (Fig. 2).

Fig. 2.

Flow chart illustrating the article screening process.

Data collection process

For data extraction, patients were grouped by procedure type: Kiva or BK. Information that was extracted includes publication year, authors, patient characteristics, procedure type, and outcome measures. Patient characteristics included age, sex, and number of fractures.

Data items and risk of bias assessment

Outcome measures included pain, measured through the Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI), and cement leakage rates. Risk of bias was assessed according to the Cochrane Handbook for Systematic Reviews of Interventions. Data was analyzed using IBM SPSS Statistics Version 28.0.

Results

Study characteristic and quality

Three RCTs were included in this meta-analysis with a total of 517 patients present at the start of the studies. However, 468 patients (Kiva=232 patients and BK=236 patients) and 694 fractures (351 treated with Kiva and 343 treated with BK) were included in the final analysis after fulfilling the inclusion criteria. The mean age of the patients was 73.5 years. The patient cohort consisted of 356 women (68.9%).

The sample sizes of the individual trials ranged from 23 patients to 144 patients (Table 1). The patients from each of the 3 trials were from the authors’ affiliated hospitals and all met specific inclusion and exclusion criteria as defined by each separate RCT. Common exclusion criteria across the 3 studies included spinal deformity, previous spinal operation, or spinal infection. Patients were then randomly chosen to receive either percutaneous BK or Kiva. In all 3 trials, there was only 1 follow-up where outcomes variables were measured.

Table 1.

Overview of patient and study characteristics

Study	Groups	Sample size of patients (N)	N of patients remaining at end of study	Sample size of fractures (N)	Age (Median)	Sex (Female) N%
Tutton et al.	KIVA VCF System	144	127	177	76.97	72.90%
	Balloon Kyphoplasty	141	126	178	75.03	75.20%
Korovessis et al.	KIVA VCF System		23	41	71	56.50%
	Balloon Kyphoplasty		24	43	70	54.20%
Korovessis et al.	KIVA VCF System	92	82	133	69.9	68.30%
	Balloon Kyphoplasty	93	86	122	72.3	71.60%

The revised Cochrane risk-of-bias tool indicated that all of the studies were of high quality and free of bias (Fig. 3). In addition, the funnel plot demonstrated that the 3 publications are almost evenly distributed on both sides in regard to publication bias (Fig. 4).

Fig. 3.

Summary of risk of bias based on Cochrane risk-of-bias tool.

Fig. 4.

Publication bias according as shown in this Funnel Plot.

Pain levels

At follow-up, the VAS score in both the Kiva and BK groups improved significantly. However, there was no difference in VAS improvement between the 2 groups (95% CI [−.19, .23], p-value=.84) (Fig. 5). Individually, all 3 studies demonstrated similar results. Minimal heterogeneity was indicated through the I² value (0.18) and H² value (1.22).

Fig. 5.

VAS scores postoperatively comparing Kiva vs. BK presented as an odds ratio with a 95% confidence interval.

As a secondary outcome measure, VAS score reduction was compared between patients who were receiving treatment for osteoporotic VCFs and VCFs caused by osteolytic metastases. In this subgroup analysis, there was no significant difference in the VAS improvement between the 2 groups (95% CI [−.17, .22], p-value=.78) (Fig. 6). Moderate heterogeneity was indicated through the I² value (0.36) and H² value (1.55).

Fig. 6.

VAS scores postoperatively comparing Kiva vs. BK in different fracture etiology presented as an odds ratio with a 95% confidence interval.

Cement leak / Extravasation

Of the 694 fractures that were treated procedurally, the Kiva system had significantly less cement leakage than BK (95% CI [−0.89, −0.22], p-value=.00) (Fig. 7). Individually, all 3 studies demonstrated Kiva superiority over BK in regard to cement leakage rate/extravasation. Considerable heterogeneity was indicated through the I² value (0.76) and H² value (4.12). Despite the cement leakage was reported in 96 vertebrae among all fractures at both groups, only 2 patients (2.1%) developed severe adverse events of acute paraplegia that required immediate decompressions.

Fig. 7.

Cement leakage rate/extravasation comparing Kiva vs. BK presented as an odds ratio with a 95% confidence interval.

Discussion

Vertebral compression fractures (VCFs) are the most common type of vertebral body fracture. The most common etiology of these fractures is osteoporosis, but another factor that may predispose patients to VCFs is metastatic disease. VCFs occur in every 10.7 per 1,000 women and 5.7 per 1,000 men, and these numbers are predicted to grow as the incidence of osteoporosis increases [12]. Additionally, the vertebral column is the third most common site for metastasis to the bone and almost one-third of these patients have associated metastasis-related VCFs [13].

While nonoperative treatment is commonly used as an initial treatment method, surgical techniques for the treatment of VCFs have become less invasive with fewer side effects. A benefit of surgical intervention is the restoration of vertebral body height, which if untreated, can lead to chronic back pain with associated deformity [14]. Treatment of vertebral fractures is paramount due to their effects on quality of life. The mortality rate in Medicare patients with a VCF is doubled compared to those without a vertebral fracture [15]. Furthermore, there is an increased economic burden associated with these fractures due to the number of office visits, hospital admissions, and nursing home admissions that they generate [16].

This meta-analysis, which focused on 3 RCTs from 2013 to 2015, compared pain reduction and cement leakage as primary outcomes in patients undergoing BK or Kiva treatment for VCFs. A secondary outcome examined pain reduction in VCFs caused by osteoporosis versus bone metastasis. Our meta-analysis demonstrated that both Kiva and BK were associated with significant improvement in pain, as assessed by VAS. However, when measuring rates of cement leakage, Kiva showed superiority over the BK system. Lastly, when comparing VAS improvement in fractures either from osteoporosis or metastasis, there was no significant difference in pain reduction using Kiva versus BK, however, such finding based on only 1 RCT and we recommended further trials to support our result.

Balloon kyphoplasty has been shown across many studies to reduce pain significantly in the treatment of VCFs [8,9,[16], [17]]. The Kiva system has also been shown to reduce pain on both the VAS and ODI scales across various trials [[18], [19], [20]]. This meta-analysis showed no changes from previous literature; both Kiva and BK significantly reduce pain in patients receiving operative treatment for VCFs. However, it is important to consider the multifactorial nature of pain outcomes. None of the 3 studies included in the meta-analysis reported on the use of pain medications, physical therapy, or supportive devices, all of which are methods used to reduce pain. While numerous RCTs have demonstrated pain relief on both the VAS and ODI scale following BK and VCF, these other factors can play a role in the amount of pain relief that patients receive following these surgical procedures and should be considered. Reductions in pain levels were not statistically different based on etiology of the fracture. However, since there was only 1 study which examined Kiva in the use of fractures due to metastasis, this should be further explored in future studies.

Regarding cement leakage, the Kiva system showed significantly better results than BK. Cement leakage associated with treatment of VCFs is an important adverse effect which can lead to additional fractures in adjacent vertebral bodies and pulmonary or remote organ embolism [21,22]. Other sequelae of cement leakage in kyphoplasty or vertebroplasty include paraplegia and nerve root compression [22]. Therefore, reducing the amount of cement leakage is of utmost importance when performing any procedural treatment for VCFs. In previous studies examining balloon kyphoplasty, cement leakage rates have ranged from 7% to 17% [9,[23], [24], [25]]. In this meta-analysis, all 3 studies showed that Kiva had improved cement leakage rates versus balloon kyphoplasty. In a previous study by Olivarez et al. [18], the cement leakage rate for Kiva was reported to be 8%. However, in the 3 studies used in this meta-analysis, cement leakage rates for the Kiva system were between 0% and 0.3%, and asymptomatic in nature. With the severity of possible side effects that cement leakage can cause, this significantly decreased rate in the Kiva system suggests a potential benefit relative to balloon kyphoplasty.

This meta-analysis has limitations. Firstly, we were only able to include a limited number of RCTs. Another limitation was that some outcomes measurements were not standardized across the studies. For example, some of the studies did not include the ODI or vertebral height restoration, and therefore we could not use them for comparison between the 2 devices. Along with that, VAS as an outcome has a tendency for bias due to its nonlinear nature [26]. Many studies have examined vertebroplasty versus kyphoplasty/Kiva as a surgical technique, but with more RCTs comparing Kiva vs BK, the meta-analysis would have stronger results.

The strengths of this meta-analysis lie in the quality of the RCTs included. The included studies demonstrated a lack of publication bias, and the funnel plot was mostly evenly distributed around a Cohen’s d value of 0. With the symmetrical nature of the funnel plot, the risk of publication bias is not likely.

Conclusion

Overall, this meta-analysis demonstrates that the Kiva system and balloon kyphoplasty are both strong surgical options for the purpose of reducing pain associated with VCFs, whether osteoporotic or metastatic in etiology. However, the meta-analysis also demonstrated that the Kiva system is favorable over balloon kyphoplasty in terms of cement leakage. Our study suggests that this reduced rate of cement leakage may provide a benefit to utilizing the Kiva system for the treatment of VCFs. Further studies might be required to compare Kiva system with other current devices available for usage.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.