Background

Osteoporotic vertebral compression fractures (OVCFs) represent a globally significant medical and socioeconomic burden, with approximately 1.4 million new OVCFs occurring yearly.1 Long-term consequences of OVCFs include chronic back pain, decline in physical function, decreased quality of life (QOL), and depression.2–5 Furthermore, a single OVCF increases the risk for new vertebral fractures five-fold in the first year, and two or more fractures increase the risk up to 12-fold.6

Balloon kyphoplasty (BKP) is a newly-developed, minimally-invasive surgical treatment for OVCFs.7 This technique aims to address fracture-related pain and associated spinal deformities. The deformity is corrected by inserting an inflatable bone tamp (IBT) into the fractured vertebral body. The IBT is subsequently inflated, increasing the height of the vertebral body, and cement is deposited into the cavity.7–12 Good clinical outcomes have been reported after kyphoplasty in short-term investigations.8–12 Kanayama et al8 found that BKP contributed to immediate pain relief; however, BKP for OVCFs did not impact global spinal alignment and balance, and few clinical studies have investigated changes in global spinal alignment after BKP.9,10 Therefore, BKP is considered to contribute greatly to the maintenance and recovery of activities of daily living (ADL) in older patients after OVCFs.12,13 However, in our clinical experience, some patients have had low health-related QOL after BKP. No previous studies have focused on the impact of BKP on health-related QOL in the long term.

This study aimed to evaluate the effects of BKP on global sagittal balance and alignment by assessing spinopelvic parameters preoperatively, at 3 months after BKP, and at the final follow-up consultation more than 12 months later, and to determine the association between predictive factors before BKP and health-related QOL in the long term.

Materials and Methods Patients and Eligibility Criteria

Sixty-two patients with symptomatic OVCFs were enrolled in this prospective cohort study conducted from April 2018 to June 2021. The inclusion criteria were (1) age >65 years and (2) computed tomography (CT) diagnosis of a new OVCF with magnetic resonance imaging (MRI) confirmation. The exclusion criteria were (1) pathological fractures as a result of underlying malignancy, (2) a diagnosis of more than one new OVCF, (3) severe dementia, (4) high-energy injuries, and (5) the patient was unable to answer these questionnaires by themselves.

Diagnosis of a new OVCF was made based on abnormal intensity and signal change in the vertebral body on CT scan and MRI. After confirmation of an OVCF diagnosis, patients were immediately admitted to the hospital and placed in a lumbosacral corset. Demographic data and data for the time of back pain onset were collected retrospectively by questioning the patients and their families.

Radiographic Evaluation

To obtain lateral radiographs of the whole spine and pelvis, the patients were asked to stand upright in a relaxed and natural manner, avoiding a forced position, and to look forward with both feet placed together on a flat surface, maintaining a horizontal gaze.14,15 Radiographs were taken preoperatively, 3 months postoperatively, and at the final follow-up consultation. We analyzed the following spinopelvic parameters: (1) sagittal vertical axis (SVA), the horizontal distance between a plumb line, originating from the middle of the body of the C7 vertebrae, and the posterior superior endplate of S1; we divided the imbalanced spine group (SVA ≥5.0 cm) and balanced-spine group (SVA <5.0 cm) as per a previous report;8 (2) thoracic kyphosis (TK) based on angle between the upper endplate of T1 and the lower endplate of T12; (3) pelvic incidence (PI) based on the angle between a line perpendicular to the sacral plate at its midpoint and a line connecting the same point to the center of the bicoxofemoral axis; (4) lumbar lordosis (LL) based on the Cobb angle from the upper endplate of L1 to the upper endplate of S1. Moreover, PI-LL mismatch was divided by more than 20 degrees or not based on the demographic mean, based on the protocol of a previous report.16

Questionnaire

The severity of pain was assessed using a self-reported numerical rating scale (NRS) in which patients provided a score from 0 to 10, based on the severity of low back pain (LBP) experienced during activity. Self-reported NRS of LBP were obtained preoperatively, immediately postoperatively, at 3 months after BKP, and the final follow-up consultation.

QOL assessments were completed for each participant using locally validated questionnaires with EuroQol 5 dimensions 5-level (EQ-5D-5L). The EQ-5D-5L is a self-administered questionnaire and descriptive system comprising five dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), each with five levels of severity (no problems, slight problems, moderate problems, severe problems, and extreme problems). The responses for the five dimensions can be combined into a 5-digit number describing the respondent’s health state (from “11111”, meaning no problems at all, to “55555”, meaning extreme problems in all five dimensions).17 We defined the cut-off value of the EQ-5D-5L index as <0.65 for low health-related QOL for the patients after BKP, based on the mean score in this study.

Indication of BKP

Preoperative assessment of the patients was conducted by examining plain radiography, CT, and MRI of the spine. Endplate deficit and posterior wall injury on a lateral view of the CT scan were indications for BKP, as these were associated with prolonged LBP.18 The patterns of signal changes within the fractured vertebral bodies on MRI were classified based on midsagittal T1-weighted images (T1WI) and T2-weighted images (T2WI). Diffuse low-intensity and confined high-intensity signals on T2WIs were also indications for BKP, as these are associated with an increased risk for non-union.19

Statistical Analyses

All statistical analyses were performed using JMP 16 (SAS Institute Japan, Tokyo, Japan). We examined the spinopelvic parameters, SVA, TK, PI- LL, and NRS of LBP preoperatively, at 3 months after BKP, and at the final follow-up consultation.

All patient data were examined for associations between the spinopelvic parameters and sex, age, average duration of the first consultation after the onset of LBP, average duration of BKP after onset of LBP, follow-up periods, preoperative bone mineral density (lumbar/femur young adult mean), presence and number of pre-existing OVCFs, and presence of subsequent fractures after BKP.

Preoperative demographic data and spinopelvic parameters of the low health-related QOL and high health-related QOL groups were compared using the two-sample t-test (for age, lumbar and femoral bone mineral density, average duration of the first consultation after onset of LBP, average duration of BKP after onset of LBP, number of pre-existing OVCFs, and preoperative SVA and PI-LL) and Fisher’s exact tests (for sex and presence of pre-existing OVCF).

Furthermore, the utility of unhealthy conditions after BKP as a predictive risk factor was examined using multivariate logistic regression logistic analysis after adjustment for age, sex, and average duration of BKP after onset of LBP. The following variables were included as independent variables: the presence of pre-ex vertebral fracture, imbalanced spine (SVA ≥5.0 cm), and PI-LL mismatch (PI-LL ≥20°). Results are presented as mean and standard deviation (SD); the threshold for statistical significance was set at P <0.05, and the corresponding 95% confidence intervals (CIs) were assessed.

Results

The study included 62 patients (13 male, 49 female) with a mean age of 78.9 years (range 63–94). On average, patients sought initial consultation 14.7 days after the onset of back pain, with BKP performed 23.8 days after the onset of back pain. The mean follow-up period was 20.7 months. Half of the cases presented with pre-existing OVCFs, and 19.7% experienced subsequent fractures after BKP. The majority of OVCFs were located in the thoracolumbar junction (T12-L2) (Table 1).

Table 1 Case Characteristics

When comparing patients with low and high health-related QOL after BKP, no significant differences were found in age, bone mineral density, or time to consultation and treatment. However, the low health-related QOL group demonstrated significantly higher SVA (9.6 vs 5.8, p<0.01) and PI-LL (31.8 vs 19.4, p<0.05) compared to the high health-related QOL group (Table 2).

Table 2 Preoperatvie Demographic Data and Spinopelvic Parameter Between Low Health-Related QOL Group and High Health-Related QOL Group After BKP

Table 3 shows that multivariate analysis, adjusted for age, sex, and average duration of BKP after onset of LBP, revealed that an imbalanced spine (SVA ≥ 5cm) was a significant risk factor for low health-related QOL (OR 4.76, 95% CI 1.32–17.2, p<0.05). Similarly, PI-LL mismatch (PI-LL ≥ 20°) was also identified as a significant risk factor (OR 3.78, 95% CI 1.18–12.1, p<0.05). Interestingly, the presence of pre-existing vertebral OVCFs was not found to be a significant predictor of low health-related QOL outcomes (OR 1.86, 95% CI 0.64–5.4, p=0.26).

Table 3 Predictive Risk Factor of Low Health-Related QOL After Balloon Kyphoplasty After Adjustment of Age, Sex and Duration from Onset Back Pain to BKP

Figure 1A shows the change in self-reported NRS score of LBP afrom preoperative assessment, to post-operation, to 3 months after BKP, and to final follow-up (p<0.05). Figure 1B shows the change in global spinopelvic parameters from preoperative assessment, to 3 months after BKP, and at final follow-up. There was no significant difference between the parameters at each consultation.

Figure 1 (A) Change in self-reported numerical rating scales of low back pain from preoperative assessment to postoperative, three months after BKP, and final follow-up consultation.(B) Changes in sagittal vertical axis, thoracic kyphosis, and pelvic incidense minus lumbar lordosis from preoperative assessment to three months after BKP and final follow-up consultation.

Discussion

In this study, we observed that BKP improved self-reported LBP severity during the follow-up period until the final consultation. However, spinopelvic parameters were not influenced by BKP in the longitudinal study for longer than 12 months. Further, imbalanced spine and PI-LL mismatch before BKP were associated with low health-related QOL at the final follow-up consultation. Excellent early relief of pain after BKP has been previously reported, suggesting that BKP can contribute to improved post-OVCF recovery and ADL in older patients.11,13,20,21 A previous study suggested that BKP should be indicated only in patients with painful OVCFs in the acute phase identified by CT.18 Few reports have focused on the impact of timing on surgical outcomes for OVCFs.20–22 Minamide et al20 reported that early BKP results in better long-term alignment and lower subsequent OVCFs rates than a delayed procedure. Kaufmann et al22 suggested that vertebroplasty for OVCFs is highly effective for pain relief and improvement of patient mobility, regardless of fracture age. Lieberman et al11 reviewed the outcomes of BKP procedures in 30 patients with painful OVCFs and found that BKP restores 35% of the lost vertebral height. Phillips et al12 conducted a prospective cohort study of 29 patients who underwent BKP for OVCFs, revealing an immediate correction of local spinal kyphosis of 8.8° on average, and significant pain reduction within the first postoperative week. Thus, the efficacy of BKP in providing pain relief and local vertebral alignment has been well established; however, there a limited number of articles have highlighted the effects of BKP on global spinal balance and alignment. In our prospective cohort study, spinopelvic balance and alignment were not significantly different after long-term follow-up. Kanayama et al8 retrospectively reviewed 56 patients who had undergone BKP for symptomatic OVCF with a mean follow-up period of 32 months. They concluded that BKP could not restore global sagittal alignment, which is consistent with our results. Since Dubousset et al23 proposed the concept of the “cone of economy”; the SVA and other spinopelvic parameters have been recognized as important for assessing the outcomes of LBP-related disability and health-related QOL.14,15 Teraguchi et al14 reported that LBP-related disability is influenced by an imbalanced spine and reciprocal change due to compensatory mechanisms in the lower extremity. Therefore, our clinical hypothesis was that the patients with an imbalanced spine might have low health-related QOL after BKP, despite relief from the pain of OVCFs. The results of our study revealed a significant association between imbalanced spine and PI-LL mismatch and low health-related QOL after BKP. For the SVA, we used a threshold of ≥5.0 cm to define an imbalanced spine. This decision aligns with previous research, including the work of Kanayama et al,8 which has shown that an SVA of 5.0 cm or greater is associated with poorer clinical outcomes and reduced QOL in patients with spinal deformities. While our study focuses specifically on OVCFs, we believe this threshold remains relevant due to the impact of OVCFs on overall spinal alignment. Further, the PI-LL mismatch threshold of ≥20° was based on our demographic mean and supported by the protocol used in Sakuma et al.16 In the context of OVCFs, this mismatch can indicate a substantial alteration in spinal sagittal balance, potentially affecting patient outcomes. For the EQ-5D-5L, we defined a score of <0.65 as indicating low health-related QOL. This cut-off was determined based on the mean score in our study population. While this approach might raise questions about generalizability, it allows for a more context-specific interpretation of QOL in our OVCF patients undergoing BKP. The significant associations we found between preoperative spinopelvic parameters and post-BKP QOL have important clinical implications. The present study highlights the need for comprehensive preoperative assessment and potentially more aggressive management strategies for patients with severe sagittal imbalance.

Previous studies investigating the relationship between spinopelvic parameters and patients’ QOL have shown that restoring normal sagittal alignment is a critical objective in achieving favorable outcomes and preventing mechanical complications in patients with adult spinal deformity.6,7 Lindsay et al6 commented that the incident OVCF increases the risk of future OVCFs, which appears to be highest during the first year after fracture (4% with 0 OVCFs vs 24% with ≥2 OVCFs). Hu et al24 reported a negative correlation between the number and severity of OVCFs and global sagittal alignment parameters. Global sagittal alignment had a better discriminative value in identifying patients with OVCF. However, the present study did not show a significant association between pre-existing OVCFs and QOL because the number of pre-existing OVCFs might have been small in each group.

Limitations

The limitations of our study should be considered. First, the sample size of 62 patients was relatively small. Further evaluations with larger and more diverse groups of patients are necessary. The average post-procedural follow-up in this study exceeded 1 year, and this should be a sufficient follow-up period to ensure the optimal potential for clinical and radiographic improvement. Nonetheless, we plan to continue following-up the patients in this cohort to further explore clinical and radiographic outcomes over longer periods. Finally, the quality of preoperative questionnaires, such as EQ-5D-5L, is questionable due to the extreme pain experienced by patients after acute vertebral compression fractures. This made health-related QOL during the pre-fracture period was difficult to measure.

Conclusions

The results of this study demonstrated that BKP relieved the LBP caused by OVCFs; however, the spinopelvic parameters were not improved by BKP after long-term follow-up. Imbalanced spine and PI-LL mismatch before BKP were associated with low health-related QOL at the final follow-up consultation after BKP. Therefore, we highlight the importance of preventing an imbalanced spine in a middle-aged population.

Ethical Approval

This study was approved by the institutional review board of Wakayama Medical University (approval number: 2898). This study complies with the Declaration of Helsinki.

Informed Consent

Informed consent was obtained from all individual participants included in the study.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding

This study was funded by the Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research (KAKENHI) Research C (20K09509).

Disclosure

The authors have no competing interests to declare that are relevant to the content of this article.

References

1. Johnell O, Kanis JA. An estimate of the worldwide prevalence and disability associated with osteoporotic fractures. Osteoporos Int. 2006;17:1726–1733. doi:10.1007/s00198-006-0172-4

2. Cooper C, Atkinson EJ, O’Fallon WM, Melton LJ. Incidence of clinically diagnosed vertebral fractures: a population-based study in Rochester, Minnesota, 1985–1989. J Bone Miner Res. 1992;7:221–227. doi:10.1002/jbmr.5650070214

3. Cook DJ, Guyatt GH, Adachi JD, et al. Quality of life issues in women with vertebral fractures due to osteoporosis. Arthritis Rheum. 1993;36:750–756. doi:10.1002/art.1780360603

4. Suzuki N, Ogikubo O, Hansson T. The prognosis for pain, disability, activities of daily living and quality of life after an acute osteoporotic vertebral body fracture: its relation to fracture level, type of fracture and grade of fracture deformation. Eur Spine J. 2009;18:77–88. doi:10.1007/s00586-008-0847-y

5. Rao RD, Singrakhia MD. Painful osteoporotic vertebral fracture. Pathogenesis, evaluation, and roles of vertebroplasty and kyphoplasty in its management. J Bone Joint Surg Am. 2003;85:2010–2022. doi:10.2106/00004623-200310000-00024

6. Lindsay R, Silverman SL, Cooper C, et al. Risk of new vertebral fracture in the year following a fracture. JAMA. 2001;285:320–323. doi:10.1001/jama.285.3.320

7. Garfin SR, Buckley RA, Ledlie J, Balloon Kyphoplasty Outcomes Group. Balloon kyphoplasty for symptomatic vertebral body compression fractures results in rapid, significant, and sustained improvements in back pain, function, and quality of life for elderly patients. Spine. 2006;31:2213–2220. doi:10.1097/01.brs.0000232803.71640.ba

8. Kanayama M, Oha F, Iwata A, Hashimoto T. Does balloon kyphoplasty improve the global spinal alignment in osteoporotic vertebral fracture? Int Orthop. 2015;39:1137–1143. doi:10.1007/s00264-015-2737-3

9. Pradhan BB, Bae HW, Kropf MA, Patel VV, Delamarter RB. Kyphoplasty reduction of osteoporotic vertebral compression fractures: correction of local kyphosis versus overall sagittal alignment. Spine. 2006;31:435–441. doi:10.1097/01.brs.0000200036.08679.1e

10. Korovessis P, Zacharatos S, Repantis T, Michael A, Karachalios D. Evolution of bone mineral density after percutaneous kyphoplasty in fresh osteoporotic vertebral body fractures and adjacent vertebrae along with sagittal spine alignment. J Spinal Disord Tech. 2008;21:293–298. doi:10.1097/BSD.0b013e31812e6295

11. Lieberman IH, Dudeney S, Reinhardt MK, Bell G. Initial outcome and efficacy of ”kyphoplasty” in the treatment of painful osteoporotic vertebral compression fractures. Spine. 2001;26:1631–1638. doi:10.1097/00007632-200107150-00026

12. Phillips FM, Ho E, Campbell-Hupp M, McNally T, Wetzel FT, Gupta P. Early radiographic and clinical results of balloon kyphoplasty for the treatment of osteoporotic vertebral compression fractures. Spine. 2003;28:2260–2265. doi:10.1097/01.BRS.0000085092.84097.7B

13. Wardlaw D, Cummings SR, Van Meirhaeghe J, et al. Efficacy and safety of balloon kyphoplasty compared with non-surgical care for vertebral compression fracture (Free): a randomised controlled trial. Lancet. 2009;373:1016–1024. doi:10.1016/S0140-6736(09)60010-6

14. Teraguchi M, Kawakami M, Ishimoto Y, et al. Sagittal imbalance of the spine-pelvis-lower extremity axis associated with back-related disability. J Orthop Sci. 2021;26:986–991. doi:10.1016/j.jos.2020.10.014

15. Schwab F, Lafage V, Boyce R, Skalli W, Farcy JP. Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position. Spine. 2006;31:E959–67. doi:10.1097/01.brs.0000248126.96737.0f

16. Sakuma T, Kotani T, Akazawa T, et al. Efficacy of lateral lumbar interbody fusion combined with posterior spinal fusion compared with three-column osteotomy for adult spinal deformity with severe lumbar sagittal deformity. Eur J Orthop Surg Traumatol. 2022;32:973–979. doi:10.1007/s00590-021-03068-z

17. Tanaka S, Ando K, Kobayashi K, et al. Association between locomotive syndrome and the Japanese version of the EQ-5D-5L in middle-aged and elderly people in Japan. Nagoya J Med Sci. 2020;82:5–14. doi:10.18999/nagjms.82.1.5

18. Teraguchi M, Kawakami M, Enyo Y, et al. Endplate deficits and posterior wall injury are predictive of prolonged back pain after osteoporotic vertebral body fracture. Spine Surg Relat Res. 2022;6:145–150. doi:10.22603/ssrr.2021-0101

19. Takahashi S, Hoshino M, Takayama K, et al. Predicting delayed union in osteoporotic vertebral fractures with consecutive magnetic resonance imaging in the acute phase: a multicenter cohort study. Osteoporos Int. 2016;27:3567–3575. doi:10.1007/s00198-016-3687-3

20. Minamide A, Maeda T, Yamada H, et al. Early versus delayed kyphoplasty for thoracolumbar osteoporotic vertebral fractures: the effect of timing on clinical and radiographic outcomes and subsequent compression fractures. Clin Neurol Neurosurg. 2018;173:176–181. doi:10.1016/j.clineuro.2018.07.019

21. Nieuwenhuijse MJ, van Erkel AR, Dijkstra PD. Percutaneous vertebroplasty for subacute and chronic painful osteoporotic vertebral compression fractures can safely be undertaken in the first year after the onset of symptoms. J Bone Joint Surg Br. 2012;94:815–820. doi:10.1302/0301-620X.94B6.28368

22. Kaufmann TJ, Jensen ME, Schweickert PA, Marx WF, Kallmes DF. Age of fracture and clinical outcomes of percutaneous vertebroplasty. AJNR Am J Neuroradiol. 2001;22:1860–1863.

23. Dubousset J. The Pediatric Spine: Principles and Practice. New York: Raven Press; 1994:479–496.

24. Hu Z, Man GCW, Kwok AKL, et al. Global sagittal alignment in elderly patients with osteoporosis and its relationship with severity of vertebral fracture and quality of life. Arch Osteoporos. 2018;13:95. doi:10.1007/s11657-018-0512-y