Is balloon kyphoplasty better than percutaneous vertebroplasty for osteoporotic vertebral biconcave-shaped fractures?

Abstract

Background

Osteoporotic vertebral biconcave-shaped fractures are not commonly seen in clinical practice. Some articles have been published showing the outcome of vertebroplasty (PV) and balloon kyphoplasty (BKP), but few comparative studies have been performed.

Purpose

To compare the effect and safety of PV and BKP in treating osteoporotic vertebral biconcave-shaped fractures.

Material and Methods

In this retrospective comparative study, 38 patients with osteoporotic vertebral biconcave-shaped fractures were treated by PV, and 41 patients were treated by BKP from May 2005 to July 2011. The heights of the compromised vertebral body and the kyphotic angles were measured. Visual analogue scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate pain and functional activity, respectively. The occurrence of refracture and cement leakage were determined, and the costs were recorded.

Results

The mean VAS and ODI scores significantly improved for both procedures at postsurgical measurements (P < 0.05), and the improvement sustained at the final follow-up. In both groups, there were no significant differences in terms of restoration of the anterior vertebral height and correction of the kyphotic deformity. However, BKP was more effective in restoring the middle vertebral height than PV. Cement leakages were observed in nine (23.7%) treated vertebral bodies in PV group and in three (7.4%) treated vertebral bodies in BKP group, which was a statistically significant difference (P < 0.05). There were four new osteoporotic vertebral fractures in the PV group and two in the BKP group during the follow-up period. The mean cost in the BKP group (6200 ± 122.1 USD) was higher than the PV group (2100 ± 112.5 USD) (P < 0.05).

Conclusion

Both PV and BKP achieved similar improvements in pain and functional outcomes for the treatment of osteoporotic vertebral biconcave-shaped fractures. BKP had a significant advantage over PV in terms of the restoration of the middle vertebral height and fewer cement leakages than PV.

Keywords

Percutaneous vertebroplasty balloon kyphoplasty osteoporotic vertebral biconcave-shaped fractures osteoporosis

Introduction

The aging of the population has brought increased attention to osteoporosis and thereby to osteoporotic fractures. Approximately 700,000 of these osteoporotic fractures affect the vertebrae (1,2). Osteoporotic vertebral compression fractures (VCFs) are associated with increased mortality and morbidity, including chronic pain, pulmonary deterioration, progressive kyphotic deformity, weight loss, depression, and an overall compromised quality of life (3 –6). The standard treatment for painful VCFs has been conservative non-surgical management (NSM) consisting of bed rest, analgesics, and bracing. However, NSM makes little contribution to vertebral stability. Furthermore, chronic medication can produce undesirable side-effects, while excessive rest can exacerbate bone demineralization, increasing the risk of bone fractures.

The application of percutaneous vertebroplasty (PV) in osteoporotic VCFs was first published by Lapras et al. in 1989 (7). Developed from PV, balloon kyphoplasty (BKP) involves the initial inflation of a balloon within the vertebral body before the injection of polymethylmethacrylate (PMMA) (8,9). The main effect of both procedures is pain relief (10 –12).Several studies have shown that restoration of the vertebral height and the angle of kyphosis are better achieved by BKP in VCFs (8,12,13). Furthermore, BKP is potentially much safer than PV because of its lower cement-leakage rate (14,15). Genant (16) classified vertebral fractures into the following three deformities: wedge deformity; biconcave deformity; and crush deformity. Ledlie et al. (17) reported that BKP resulted in a significant normalization of vertebral shape in patients with symptomatic vertebral fractures of different deformity shapes (wedge, biconcave, and crush). To the best of our knowledge, no article has shown whether PV can restore the normal vertebral shape following an osteoporotic vertebral biconcave-shaped fracture, and few articles to date have shown the differences in terms of clinical efficacy, vertebral height restoration, correction of the kyphotic angle, complication rate, and cost of osteoporotic vertebral biconcave-shaped fracture treated with PV and BKP. Here, we report on a retrospective comparative study to assess the differences between the clinical and radiological outcomes of treating osteoporotic vertebral biconcave-shaped fractures with PV and BKP.

Material and Methods

Patient selection

A total of 79 patients who suffered from osteoporotic vertebral biconcave-shaped fractures underwent either PV or BKP from May 2005 to July 2011. In our study, 38 patients were treated by PV, while the other patients were treated by BKP. These patients suffered from severe back pain refractory to non-operative treatment. Symptomatic levels were identified by correlating the clinical data with magnetic resonance imaging findings of marrow signal changes that were consistent with osteoporotic vertebral biconcave-shaped fractures. Further, all of the patients had only a single symptomatic vertebral fracture, and all of the patients had osteoporosis that had been identified by dual-energy X-ray absorptiometry before undergoing PV and BKP. The levels treated by PV and BKP were located in the thoracic and lumbar spine. The patients’ demographic data are shown in Table 1. The demographic data of the patients in the PV and BKP groups were similar; hence, the two groups were comparable.

Table 1.

The patient demographic data of PV and BKP.

PV	BKP
n	38	41
Age (years)	67.1 ± 2.32.3	69.1 ± 3.2*
Follow-up (months)	41.4 ± 3.6	43.5 ± 4.1*
Gender (F:M)	29:9	32:9*
BMD (T-score)	−(3.6 ± 1.1)	−(3.9 ± 1.2)*
VAS (preop)	8.2 ± 1.6	8.3 ± 2.1*
ODI (preop, %)	72.2 ± 6.9	71.3 ± 7.1*
Ha (preop, mm)	28.6 ± 1.3	28.5 ± 1.4*
Hm (preop, mm)	19.4 ± 1.6	19.9 ± 1.2*
Cobb’s angle (preop, °)	6.2 ± 1.1	5.9 ± 1.2*

PV compared with BKP, P > 0.05.

BMD, bone mineral density; Ha, anterior vertebral height; Hm, middle vertebral height; mm, minimeter; ODI, Oswestry Disability Index; preop, preoperation; VAS, visual analogue scale.

Surgical technique and postoperative therapy

The operations were performed under local or general anesthesia with fluoroscopic guidance. PV and BKP were carried out according to the standard published techniques (7 –9). Kyphon® (Sunnyvale, CA, USA) instruments and PMMA cement were used for BKP. All of the patients were referred for treatment with calcium and vitamin D supplements and antiresorptive or anabolic agents after PV or BKP.

Clinical assessment

Back pain was assessed using a visual analogue scale (VAS) with values in the range of 0–10 prior to PV and BKP, 1 day after surgery, and at the final follow-up assessment. Furthermore, Oswestry Disability Index (ODI) scores, which are used to assess functional capacity, were also documented.

Radiographic assessment

Plain digital radiographs were taken prior to PV and BKP, 1 day postoperatively and at the final follow-up assessment. The vertical heights (anterior and middle) of all of the compromised vertebrae were measured preoperatively, postoperatively, and at the final follow-up assessment using lateral radiographs of the spine. Vertebral body height measurements (anterior and midline) were obtained from standing lateral radiographs for compromised and adjacent uncompromised control vertebrae. For each patient and radiograph, the normal height of the compromised vertebrae was estimated from the mean of the measurements from the closest uncompromised vertebral cephalad and caudad to the treated level. The kyphotic angle was calculated from the standing lateral radiographs using Cobb’s method. The measurements were taken from the superior endplate of the vertebra one level above the treated vertebra to the inferior endplate of the vertebra one level below the treated vertebra.

Complications and cost

The rates of refracture and cement leakage outside the vertebral body were determined postoperatively using radiographs and CT scans. The costs of the two procedures were recorded.

Statistical analysis

Mean changes in efficacy outcomes (anterior and middle vertebral body height ratios, kyphotic angles, costs, and VAS and ODI scores) were analyzed using SPSS, version 13.0 (SPSS, Inc., Chicago, IL, USA). Comparisons were made before and at each follow-up appointment after PV or BKP. The data were all normally distributed. Paired-samples t-tests were performed to compare the costs, amounts of cement applied during PV and BKP, anterior and middle vertebral body height (Ha and Hm, respectively), kyphotic angles, and VAS and ODI scores. Chi-squared tests were performed to compare the rates of cement leakage and refracture following PV and BKP, and P values < 0.05 were considered to be statistically significant.

Results

All of the patients tolerated both procedures well. The mean follow-up period and the mean amount of cement applied during each procedure are shown in Tables 1 and 2, and no significant differences were found (P > 0.05) between the two groups in terms of the preoperative conditions. Cement leakages were observed in nine out of the 38 treated vertebral bodies in the PV group, while cement leakages were observed in three out of the 41 treated vertebral bodies in the BKP group (Table 3). This difference was statistically significant (P < 0.05). There were four new osteoporotic vertebral fractures in the PV group and two new osteoporotic vertebral fractures in the BKP group during the follow-up period (Table 3); this difference was not statistically significant (P > 0.05). The mean cost in the PV group was 2100 ± 112.5 USD; however, the mean cost in the BKP group was much higher (P < 0.05) at a total of 6200 ± 122.1 USD (Table 2).

Table 2.

The costs and amounts of cement applied during PV and BKP.

PV	BKP
Cost (USD)	2100 ± 112.5	6200 ± 122.1*
Cement application (mL)	4.5 ± 1.1	4.6 ± 0.9^†

PV compared with BKP, P < 0.05.

†

PV compared with BKP, P > 0.05.

Table 3.

The cement leakage, refracture rates, and type of cement leakage following PV and BKP.

PV	BKP
Cement leakage	9/38(23.7%)	3/41(7.3%)*
Refracture	4/38(10.5%)	2/41(4.9%)^†
Disc leakage	7	2
Paravertebral tissue leakage	2	1

PV compared with BKP, P < 0.05.

†

PV compared with BKP, P > 0.05.

Clinical assessment

The two groups both experienced excellent pain relief and functional capacity improvements. There were significant improvements in both groups (P < 0.05) in the mean VAS scores at the immediate postoperative follow-up assessment (PV group, 2.8 ± 0.8; BKP group, 2.7 ± 1.0) and at the final follow-up assessment (PV group, 2.9 ± 1.1; BKP group, 2.8 ± 0.9) compared with the baseline values (PV group, 8.2 ± 1.6; BKP group, 8.3 ± 2.1) (Table 4). With respect to the functional capacity status, significant improvements (P < 0.05) were observed in comparing the mean ODI scores in the PV group (36.1 ± 3.1 at the immediate postoperative follow-up assessment and 37.3 ± 3.2 at the final follow-up assessment) and in the BKP group (35.2 ± 2.9 at the immediate postoperative follow-up assessment and 36.5 ± 3.1 at the final follow-up assessment). It remained significantly improved when compared to the final follow-up assessment (PV group, 37.3 ± 3.2; BKP group, 36.5 ± 3.1) (P < 0.05). However, no differences were found between the two groups with respect to the mean VAS and ODI scores (P > 0.05).

Table 4.

Mean improvements in VAS and ODI scores before and after treatment with PV and BKP.

	Preoperative		Postoperative		At the final follow-up
	PV	BKP	PV	BKP	PV	BKP
VAS	8.2 ± 1.6	8.3 ± 2.1	2.8 ± 0.8*	2.7 ± 1.0*^†	2.9 ± 1.1^‡	2.8 ± 0.9^‡
ODI	72.2 ± 6.9	71.3 ± 7.1	36.1 ± 3.1*	35.2 ± 2.9*^†	37.3 ± 3.2^‡	36.5 ± 3.1^‡

Postoperative compared with preoperative, P < 0.05.

†

PV compared with BKP, P > 0.05.

‡

The final follow-up assessment compared with preoperative, P < 0.05.

ODI, Oswestry Disability Index; VAS, visual analogue scale.

Radiographic assessment

Postoperatively, in the PV group, the midline and anterior vertebral body heights were corrected slightly (P > 0.05), and this correction was maintained at the final follow-up assessment. A similar pattern of correction was observed in the kyphotic angles (Table 5). In the BKP group, there were no significant differences in terms of the anterior vertebral body heights and the kyphotic angles postoperatively and at the final follow-up assessment (P > 0.05). However, the midline vertebral body height was significantly corrected postoperatively as illustrated in Fig 1. This correction was maintained at the final follow-up assessment (P < 0.05) (Table 5). There were no differences in terms of the anterior vertebral body heights and the kyphotic angles postoperatively and at the final follow-up assessment between the PV and BKP groups. However, compared with the PV group, the midline vertebral body height was significantly more corrected by BKP (Table 5).

Table 5.

Mean of anterior and middle vertebral height ratios and kyphotic angles (degrees) before and after treatment with PV and BKP.

	Preoperative		Postoperative		At the final follow-up
	PV	BKP	PV	BKP	PV	BKP
Ha (mm)	28.6 ± 1.3	28.5 ± 1.4	28.7 ± 2.1*	28.6 ± 1.5*^†	28.5 ± 1.5^‡	28.4 ± 1.1^‡
Hm (mm)	19.4 ± 1.6	19.9 ± 1.2	19.9 ± 1.8*	24.2 ± 2.1^§**	19.6 ± 1.8^‡	24.0 ± 1.6^††
Cobb’s angle	6.2 ± 1.1	5.9 ± 1.2	6.0 ± 1.4*	5.7 ± 1.3*^†	6.1 ± 0.9^‡	5.8 ± 1.1^‡

Postoperative compared with preoperative, P > 0.05.

†

PV compared with BKP, P > 0.05.

‡

The final follow-up assessment compared with preoperative, P > 0.05.

PV compared with BKP, P < 0.05.

Postoperative compared with preoperative, P < 0.05.

††

The final follow-up assessment compared with preoperative, P < 0.05.

Ha, anterior vertebral height; Hm, middle vertebral height.

Discussion

Vertebral fractures in osteoporosis are common in the elderly population, with an estimated 1.4 million new fractures occurring every year worldwide (18). However, the classification of vertebral fractures is controversial (16,19,20). Genant (16) classified vertebral fractures as the following three deformities: wedge deformity; biconcave deformity; and crush deformity. This classification system is now used extensively. In practice, osteoporotic vertebral wedge-shaped fractures are the most common fractures; however, osteoporotic vertebral biconcave-shaped fractures are not rare. Biomechanical studies have indicated that a biconcavity deformity is a true vertebral fracture resulting from the pressure of the intervertebral disc on a vertebral endplate weakened by the thinning of the cortex and the loss of central trabeculae (21). A meta-analysis has shown that both PV and BKP provided significant improvements in VAS pain scores (22). Santiago et al. (23) compared 30 patients treated by PV for non-neoplastic vertebral fractures with 30 patients treated by BKP under the same conditions. The authors concluded that PV and BKP achieved similar improvements in pain and functional outcomes in their patients. A prospective 1-year follow-up analysis demonstrated that the median pain scores (VAS) and the Oswestry scores had decreased significantly for both BKP and PV from the pre- to the post-treatment assessments (P < 0.05), and no significant differences were found between the groups with respect to the median pain scores (VAS) and the Oswestry scores (12). In accordance with those previous studies, our study confirmed the analgesic efficacy and improvements in functional outcomes of PV and BKP in the treatment of the osteoporotic vertebral biconcave-shaped fractures. Furthermore, our study showed that BKP was more efficacious in middle vertebral height restoration than PV, while there was no difference in pain reduction between the two procedures. Therefore, we concluded that the postoperative pain level of the patients was independent of height reconstruction.

Several studies (8,9,11) have shown that BKP has the potential to correct kyphotic deformities and restore vertebral height. In contrast, PV simply stabilizes the fracture and avoids further height loss but does not provide the opportunity for height restoration and deformity correction in the fractured vertebral body. Li et al. (24) demonstrated that BKP offered a higher degree of spinal deformity correction than PV. Schofer et al. (25) performed a study to compare BKP and PV in the treatment of fresh vertebral compression fractures, and they concluded that BKP led to an ongoing reduction in the number of freshly fractured vertebrae.

A prospective 1-year follow-up analysis confirmed that BKP significantly restored vertebral body heights in fresh fractures compared with PV (12). Although many studies have shown that BKP is better than PV in the restoration of vertebral heights and the correction of kyphosis, fracture shape has always been neglected. In accordance with Ledlie’s study (11) that BKP resulted in significant normalization of osteoporotic vertebral biconcave-shaped fractures, our study demonstrated that BKP could normalize the shape of osteoporotic vertebral biconcave-shaped fractures, while PV could not because it could not restore the middle vertebral body height. Our study showed that both BKP and PV produced poor radiographic responses for kyphosis correction following osteoporotic vertebral biconcave-shaped fractures. This might be the normal outcome for anterior and posterior body heights following osteoporotic vertebral biconcave-shaped fractures.

The most important complication of PV and BKP remains leakage of the cement. In our study, disc leakage was recorded in nine patients following the PV procedure and in two patients following the BKP procedure. Paravertebral tissue leakage was observed in two patients in the PV group and in one patient in the BKP group. In our study, BKP resulted in fewer cement leakages than PV, which was similar to the results of several previous studies (8,12,24,25). It may be that the inflation of the balloon creates a void within the vertebral body into which the cement could be injected under relatively low pressure. Moreover, the expansion of the balloon tamp compacting cancellous bone in the intravertebral cavity may also reduce the rate of cement leakage. Osteoporotic vertebral biconcave-shaped fractures result from the pressure of the intervertebral disc on a vertebral end plate weakened by the thinning of the cortex and the loss of central trabeculae. Thus, the superior endplates of osteoporotic vertebral biconcave-shaped fractures are always damaged, and the PMMA extends from the body through the cleft into the superior disc space. This phenomenon may explain why disc space leakage was the most commonly observed leakage type in our study. However, it should be noted that this leakage type was clinically silent in all of the cases in our study. However, the consequences of disc-space leakage are still unknown. Lazáry et al. (26) investigated the influences of PV filler materials (polymethylmethacrylate-, calcium phosphate-, and calcium sulfate-based bone cements) on isolated nucleus pulposus cells. The authors suggested that PV filler materials could accelerate the degeneration of nucleus pulposus cells, resulting in a less flexible disc in cases of intradiscal cement leakage. They concluded that this process may increase the risk of a subsequent new vertebral fracture. Lin et al. (27) analyzed the incidence of new fractures in adjacent vertebral bodies in relation to cement leakage into the disc that had occurred during the initial PV. The authors concluded that leakage of cement into the disk during PV increases the risk of new fractures of adjacent vertebral bodies. Disc extravasation was observed in 81 patients at a total of 85 vertebral levels among the 308 patients in a study performed by Syed et al. (28), and the authors could not conclude whether there was a significant difference in the location of the fracture and the occurrence of disk extravasation for patients who had a new fracture. In our study, there was no difference between the PV and BKP groups with respect to the refracture rate. Therefore, we conclude that the relationship between the refracture rate and disc-space leakage is open to debate, and long-term follow-up and prospective randomized control studies are needed.

In our study, the mean cost in the PV group was 2100 ± 112.5 USD. In contrast, the mean cost in the BKP group was 6200 ± 122.1 USD. It seems that PV has an advantage over BKP for the treatment of osteoporotic vertebral biconcave-shaped fractures, considering the higher cost of BKP. However, this was just the procedure-related cost. The total costs for each patient, including the procedure-related cost, the cost of postoperative medication, and post-hospital care should also been taken into account. Svedbom et al. (29) estimated the cost-effectiveness of BKP compared to NSM and PV for the treatment of hospitalized osteoporotic vertebral compression fractures in the UK. That study showed that BKP might be a cost-effective strategy for the treatment of patients hospitalized with acute osteoporotic VCFs in the UK compared to NSM and PV. Hence, the cost-effectiveness of BKP versus PV for osteoporotic vertebral biconcave-shaped fractures should be further investigated.

Our study was limited by the retrospective study type and the short follow-up time, so a prospective study should be undertaken and a long-term follow-up is in need.

In conclusion, both PV and BKP were followed by significant pain relief, and the quality of life was similar regardless of the procedure used for osteoporotic vertebral biconcave-shaped fractures. However, BKP led to a significant normalization of the fractured vertebrae and was complicated at a lower rate by cement leakage.

Footnotes

Funding

This work was supported by National Science Foundation of Jiangsu, China (81071451, 81171689, 81301559, BK2011264).

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