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Percutaneous balloon kyphoplasty for the treatment of very severe osteoporotic vertebral compression fractures: a case-control study
The Spine Journal 18 (2018) 962–969
Clinical Study
Percutaneous balloon kyphoplasty for the treatment of very severe osteoporotic vertebral compression fractures: a case-control study Jin Kyu Lee, MD, Hae-won Jeong, MD, Il-Han Joo, MD, Young-Il Ko, MD, Chang-Nam Kang, MD, PhD* Department of Orthopaedic Surgery, Hanyang University College of Medicine, 222-1 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea Received 8 June 2017; revised 5 September 2017; accepted 5 October 2017
Abstract
BACKGROUND CONTEXT: Controversy exists regarding percutaneous balloon kyphoplasty (PBK) in patients with a very severe osteoporotic vertebral compression fracture (vsOVCF). PURPOSE: The study was conducted to investigate the clinical and radiological outcomes of PBK for the treatment of vsOVCF compared with those of non-vsOVCF. STUDY DESIGN/SETTING: This is a retrospective, case-control study. PATIENT SAMPLE: A total of 167 consecutive patients (210 vertebral bodies) who underwent PBK for OVCF between March 2010 and January 2015 were assessed. OUTCOME MEASURES: Visual analog scale (VAS) scores for back pain, Korean Oswestry disability index (K-ODI) scores, vertebral body height variations, and kyphotic angles were evaluated preoperatively, postoperatively, and 1 year after treatment. MATERIALS AND METHODS: Patients in the non-vsOVCF group (anterior vertebral compression of more than two-thirds on plain radiograph) who had undergone PBK where compared with those in the non-vsOVCF group (compression between 30% and two-thirds). Clinical and radiological outcomes were compared. In addition, complications were evaluated. RESULTS: In total, 31 patients (33 vertebrae) in the vsOVCF group and 136 patients (177 vertebrae) in the non-vsOVCF group were treated with PBK. Both groups had significant postoperative improvements in the clinical and radiological outcomes (VAS score, K-ODI score, vertebral body height variation, and kyphotic angle). There was no difference regarding the VAS score and the K-ODI score between the two groups at the final follow-up (p>.05). The cement leakage occurred frequently in the vsOVCF group (26 vertebrae, 78.8%) than in the non-vsOVCF group (92 vertebrae, 52.0%), the difference was statistically significant (p<.05). But there was no case that showed neurologic complication or pulmonary embolism caused by cement leakage. The incidence of recollapse was significantly higher in the vsOVCF group (five vertebrae, 15.2%) than in the non-vsOVCF group (seven vertebrae, 4.0%) (p<.05). The incidence of an adjacent segment fracture (vsOVCF group, 6 vertebrae, 18.2%; non-vsOVCF group, 21 vertebrae, 11.9%) was not significantly different (p=.320). CONCLUSIONS: Percutaneous balloon kyphoplasty is a safe and effective procedure for the treatment of vsOVCF. © 2017 Elsevier Inc. All rights reserved.
Keywords:
Clinical outcome; Complications; Osteoporosis; Percutaneous balloon kyphoplasty; Radiological outcome; Vertebral compression fracture
FDA device/drug status: Approved (percutaneous balloon kyphoplasty). Author disclosures: JKL: Nothing to disclose. HJ: Nothing to disclose. IHJ: Nothing to disclose. YIK: Nothing to disclose. CNK: Nothing to disclose. The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com. There were no sources of funding and no conflicts of interest associated with this study. * Corresponding author. Department of Orthopedic surgery, Hanyang University Medical Center, 222-1 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea. Tel. 82 2 2290 8485. E-mail address: [email protected] (C.-N. Kang). https://doi.org/10.1016/j.spinee.2017.10.006 1529-9430/© 2017 Elsevier Inc. All rights reserved.
Introduction Osteoporotic vertebral compression fractures (OVCFs) are one of the most common complications of osteoporosis, causing severe pain, restricting activity, lowering the quality of life, and also increasing the incidence of systemic complications and mortality [1,2]. Percutaneous balloon kyphoplasty (PBK) is a minimally invasive operation that involves inserting and inflating a balloon inside the vertebral body that has been damaged by the OVCF
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and then injecting cement into the void of the vertebral body [3,4]. This technique has the advantage of reducing cement leakage during surgery and may eliminate pain and restore vertebral body height immediately after surgery [5]. However, there are a limited number of studies on PBK performed in patients with a very severe osteoporotic vertebral compression fracture (vsOVCF). [3,5–10] Very severe osteoporotic vertebral compression fractures are defined by a reduction of two-thirds or more in the expected vertebral body height [11]. In patients with a vsOVCF, PBK requires advanced surgical techniques because the compression rate of the vertebral body is so severe, and some authors have argued that a vsOVCF is a relative contraindication for PBK and instead recommend conservative treatment [12]. However, others recommend either corpectomy with anterior fusion or posterior arthrodesis for patients with a vsOVCF [13,14]. We previously reported height restoration after PBK in patients with OVCF with rheumatoid arthritis [8] and hypothesized that PBK in patients with vsOVCF would recover appropriate vertebral body height and kyphotic angle and then improve clinical outcomes. We therefore conducted a comparative analysis of the clinical and radiological outcomes of PBK performed in patients with vsOVCF and in patients without vsOVCF. Materials and methods The present study investigated the patient records of 167 consecutive patients (210 vertebral bodies) who underwent PBK for OVCF at Hanyang University Hospital between March 2010 and January 2015. All patients were followed up for a minimum of 12 months (range 12–48 months). OVCFs were diagnosed in patients who complained of back pain or lower back pain, had a history of low-energy trauma and tenderness in the thoracolumbar region according to the physical examination, and manifested compression of the vertebral body on plain radiograph. Patients with an OVCF were further examined by magnetic resonance imaging or bone scan to confirm an acute fracture, and bone mineral density (BMD) was then calculated using dual-energy x-ray absorptiometry (DXA) to confirm osteoporosis. Patients who experienced discomfort in everyday life because of pain even after undergoing conservative treatment for three weeks or longer, and with a confirmed vertebral body compression rate of 30% or higher on plain radiograph were selected for the PBK procedure. For patients aged 80 years or older, PBK was performed in patients with a vertebral body compression rate of 30% or higher without the requirement of a previous conservative treatment (Figs. 1 and 2). Korean National Health Insurance covers PBK when the compression rate is 30% or higher or patients are aged 80 years or order. So we set the previously mentioned indications of PBK. Patients with either a vertebral fracture caused by highenergy trauma or a pathologic fracture caused by infection or tumor were excluded, and patients who had a fracture 3 months before the diagnosis were also excluded.
Fig. 1. Eighty-eight-year-old male patient who was admitted to our hospital after he slipped down. (A) Plain lateral radiograph shows the osteoporotic vertebral compression fracture of the L1 vertebra with 80% severe collapse and 33° local kyphosis. (B) T1 sagittal magnetic resonance imaging shows an acute recent fracture of the L1 vertebra. (C) Intraoperative fluoroscope shows a Jamshidi needle (guide pin) inserted in the L1 vertebra. (D) A percutaneous balloon tamp was inflated and reduced the collapse of the vertebral height. Immediate postoperation (E) and 1-year follow-up (F) lateral plain radiograph. The body height and the kyphotic angle improved and remained stable 1 year after the operation.
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Fig. 2. Eighty-three-year-old male patient who was admitted our hospital after he slipped down. (A) Plain lateral radiograph shows the osteoporotic vertebral compression fracture of the T12 vertebra with a 42% severe collapse and a 37° local kyphosis. (B) T1 sagittal magnetic resonance imaging shows an acute recent fracture of the T12 vertebra. (C) Intraoperative fluoroscope shows a Jamshidi needle inserted in the T12 vertebra. (D) A percutaneous balloon tamp was inflated and reduced the collapse of the vertebral height. Immediate postoperation (E) and 1-year follow-up (F) lateral plain radiograph. The body height and the kyphotic angle improved and remained stable 1 year after the operation. (G) A postoperative computed tomography scan with axial image shows no cement leakage into the spinal canal.
Among the patients who underwent PBK, those who had an anterior vertebral compression of more than two-thirds on plain radiograph were classified as the vsOVCF group, and patients with an anterior vertebral compression between 30% and two-thirds were classified as the non-vsOVCF group. The surgery was performed by a single surgeon at one institution. All patients were treated with local anesthesia and sedation followed by a conventional bilateral transpedicular approach in the prone position. Prophylactic antibiotics were administered 30 minutes before surgery, and blood pressure, pulse, and oxygen saturation were checked during the surgery. The bone cement injection and leakage were monitored using C-arm fluoroscopy during the surgery (Figs. 1 and 2). With any doubt of cement leakage into the spinal canal on the fluoroscopy, cement injection was stopped at the corresponding needle. The bone cement used was polymethyl methacrylate, and the injection time was measured from the time the polymethyl methacrylate was polymerized to the time the injection began. The cement volume is the total volume
of cement injected on both sides. Patients began to walk by themselves immediately after the operation. For the measurement of clinical outcomes, the visual analog scale for back pain (VAS-BP) and the Korean Oswestry disability index (K-ODI) scores were evaluated preoperatively, postoperatively, and 1 year after the operation. Radiological outcomes were evaluated by an orthopedic spine fellow and an orthopedic resident, who both underwent the same training twice at 2-week intervals. The anterior height of the fractured vertebral body and the difference in the kyphotic angle of the local segment were measured preoperatively, postoperatively, and 1 year after operation, as were cement leakage, recollapse of the cemented vertebral body, and any adjacent segment fracture. The vertebral body compression rate was calculated as a percentage of the average adjacent superior and inferior anterior vertebral body heights measured from a plain lateral radiograph taken in an erect posture. Recollapse was defined when the anterior vertebral body height decreased by 5% or more within 1 year of the operation, in
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comparison with the anterior vertebral body height recovered immediately following the operation. The kyphotic angle of the local segment was calculated from the Cobb angle formed by the superior end plate of the upper vertebral body of the fractured vertebra and the inferior end plate of the lower vertebral body. Cement leakage was examined using anteroposterior and lateral plain radiographs, and an additional computed tomography scan was performed when the spinal canal involvement was in doubt (Fig. 3). Cement leakage was defined as any evidence of leakage beyond the vertebral body. The age, gender, and BMD of each patient at the time of surgery were recorded in the electronic medical record. Statistical analyses SPSS version 20.0 (SAS Institute, Cary, NC, USA) was used for all statistical analyses. The paired t test was used to compare the vertebral body compression rate and the kyphotic angle preoperatively, postoperatively, and 1 year after surgery. The chi-square test was used to compare bone cement leakage, recollapse, and adjacent segment fracture between the groups. The independent t test was used for a comparative analysis of continuous data, and the Cohen kappa coefficient was used to analyze intra- and interobserver reliability. Statistical significance was set at p<.05. Results Interobserver and intraobserver reliabilities The kappa coefficients for intraobserver reliability for vertebral body height and kyphotic angle, as measured on preoperative and postoperative radiographs, were 0.85 (95% confidence interval 0.74–0.95) and 0.89 (95% confidence interval 0.79–0.99), respectively. The kappa coefficients for interobserver reliability were 0.74 (95% confidence interval 0.59–0.88) and 0.75 (95% confidence interval 0.64–0.87), respectively, indicating high conformity. Demographic data Thirty-one patients (33 vertebral bodies) had a vertebral compression rate of more than two-thirds and were therefore categorized in the vsOVCF group, and 136 patients (177 vertebral bodies) had a vertebral compression rate between 30% and two-thirds, and were therefore categorized in the non-vsOVCF group. The two groups were not significantly different in terms of age, gender, body mass index, or BMD (p=.615, p=.524, p=.663, and p=.214, respectively). There was no statistical difference between the two groups with regard to the location of the fracture (p=.161). The average time between the fracture and PBK was 23.6 days in the vsOVCF group and 19.0 days in the non-vsOVCF group (p=.019). Comorbidities included hypertension, diabetes, stroke, rheumatoid arthritis, and cardiovascular diseases, and there were no statistical differences between the vsOVCF and the
Fig. 3. Seventy-nine-year-old female patient who was admitted to our hospital after she slipped down. (A) Plain lateral radiograph shows the osteoporotic vertebral compression fracture of the L1 vertebra with a 68% severe collapse and an 11° local kyphosis. (B) T1 sagittal magnetic resonance imaging shows an acute recent fracture of the L1 vertebra. Immediate postoperation (C) and 1-year follow-up (D) lateral plain radiograph. The body height and the kyphotic angle improved and remained stable 1 year after the operation. Immediate postoperation computed tomography sagittal (E) and axial (F) images show a leakage of the cement (arrows) into the spinal canal.
non-vsOVCF groups (p=.273, p=.358, p=.512, p=.412, p=.344, respectively; Table 1). Comparison of radiographic and clinical outcomes In the vsOVCF group, the rates of the anterior height of the fractured vertebral bodies were 29.4%±4.0% preoperatively
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Table 1 Demographic data vsOVCF Age (y) Gender(n) Female Male BMI (kg/m2) BMD (g/cm2) BMD (T-score) No. of involved vertebra T9 T10 T11 T12 L1 L2 L3 L4 L5 Time to surgery (d) Comorbidity (n) Hypertension Diabetes Stroke RA Cardiovascular disease
Non-vsOVCF
p-Value
75.0±8.1
74.3±7.1
.615
23 8 22.9±3.1 0.48 −3.2±0.9
108 28 23.2±3.3 0.51 −3.2±0.9
.524 .663 .214 .813
2 1 2 11 11 3 1 2 0 23.6
1 2 15 37 59 32 13 13 5 19.0
.161
.019
20 11 2 1 1
73 37 14 12 11
.273 .358 .512 .412 .344
BMI, body mass index; BMD, bone mineral density; T, thoracic vertebra; L, lumbar vertebra; RA, rheumatoid arthritis; vsOVCF, very severe osteoporotic vertebral compression fracture. Values are given as mean±standard deviation.
and 61.4%±11.7% postoperatively, indicating that the vertebral height was restored with statistical significance (p<.001). In the non-vsOVCF group, the rates of the anterior height of the fractured vertebral bodies were 64.3%±16.0% preoperatively and 77.6%±13.5% postoperatively, also indicating that height was restored with statistical significance (p<.001). In the vsOVCF group, the local kyphotic angle was 19.6±11.7 preoperatively and 16.2±12.0 postoperatively, and in the nonvsOVCF group, the local kyphotic angle was 17.7±10.5
preoperatively and recovered to 15.3±10.1 postoperatively; both groups showed a statistically significant improvement in the kyphotic angle (p<.001, respectively). At the 1-year follow-up, the local kyphotic angle remained improved in both the vsOVCF and the non-vsOVCF groups (17.1±11.5 and 16.2±11.6, p=.011 and p=.008, respectively). In the vsOVCF group, the VAS-BP score recovered from 7.6±1.3 preoperatively and 3.9±1.5 postoperatively, and in the non-vsOVCF group, the VAS-BP score recovered from 7.3±1.9 preoperatively and 3.6±1.7 postoperatively; the improvement was statistically significant for both groups (p<.001, respectively). In the vsOVCF group, the K-ODI score recovered from 32.2±5.6 preoperatively and 19.7±5.2 postoperatively, in the non-vsOVCF group, the K-ODI score recovered from 31.4±7.3 preoperatively and 19.2±7.6 postoperatively; this improvement was statistically significant for both groups (p<.001, respectively; Table 2). The cement volume used during PBK was 6.8±1.8 cc in the vsOVCF group and 6.9±1.9 cc in the non-vsOVCF group; there was no significant difference between the two groups (p=.642). Cement injection time was 10.0±3.0 minutes in the vsOVCF group and 10.0±2.5 minutes in the non-vsOVCF group, with no significant differences between the two groups (p=.986). The height restoration of the anterior vertebral body was 32.0%±10.9% in the vsOVCF group and 13.4%±13.1% in the non-vsOVCF group, indicating a statistically significant improvement in the height restoration of vertebral body in the vsOVCF group (p<.001). When comparing the postoperative state with the preoperative state, there were no significant differences between the two groups in terms of the degree of improvement in the local kyphotic angle, the VAS-BP score, and the K-ODI score (p=.387, p=.968, p=.826, respectively). When comparing the preoperative state with the state at the 1-year follow-up, the height restoration of the anterior vertebral body was significantly high in the vsOVCF group (p<.001); however, the two groups did not show any significant differences in terms of the degree of improvement
Table 2 Comparison of radiographic and clinical outcomes
Height rate (%) vsOVCF Non-vsOVCF Kyphotic angle (°) vsOVCF Non-vsOVCF VAS-BP vsOVCF Non-vsOVCF K-ODI vsOVCF Non-vsOVCF
Preoperative
Postoperative
1-y Follow-up
p-Value
29.4±4.0 64.3±16.0
61.4±11.7 77.6±13.5
57.9±10.3 72.9±12.5
.000*/.000* .000*/.000*
19.6±11.7 17.7±10.5
16.2±12.0 15.3±10.1
17.1±11.5 16.2±11.6
.000*/.011 .000*/.008
7.6±1.3 7.3±1.9
3.9±1.5 3.6±1.7
2.3±1.0 2.0±1.1
.000*/.000* .000*/.000*
32.2±5.6 31.4±7.3
19.7±5.2 19.2±7.6
16.7±6.1 16.5±7.0
.000*/.000* .000*/.000*
VAS-BP, visual analog scale for back pain; K-ODI, Korean Oswestry disability index; vsOVCF, very severe osteoporotic vertebral compression fracture. Values are given as mean±standard deviation. p-Value: preoperative versus postoperative and preoperative versus 1-year follow-up. * p<.001.
J.K. Lee et al. / The Spine Journal 18 (2018) 962–969 Table 3 Comparison of vsOVCF and non-vsOVCF vsOVCF
Non-vsOVCF p-Value
Cement volume (cc) 6.8±1.8 6.9±1.9 Cementation time (min) 10.0±3.0 10.0±2.5 Height of fractured vertebra (mm) 7.9±1.4 17.2±4.6 Vertebral body collapse (%) 0.3±0.1 0.6±0.1 Postop-preop comparison Height restoration (%) 32.0±10.9 13.4±13.1 Local kyphosis variation (°) −3.4±4.8 −2.4±6.4 VAS variation −3.7±1.8 −3.7±2.0 K-ODI variation −12.4±4.1 −12.2±5.6 1-y Follow-up—preop comparison Height restoration (%) 28.5±10.1 8.6±13.3 Local kyphosis variation (°) −2.6±5.4 −1.5±7.3 VAS variation −5.3±1.7 −5.3±1.9 K-ODI variation −15.4±5.1 −14.9±5.4
.642 .986 .000* .000* .000* .387 .968 .826 .000* .415 .997 .635
VAS, visual analog scale; K-ODI, Korean Oswestry disability index; vsOVCF, very severe osteoporotic vertebral compression fracture. Values are given as mean±standard deviation. * p<.001.
Table 4 Postoperative complications
Cement leakage Recollapse Adjacent segment fracture
vsOVCF
Non-vsOVCF
p-Value
26 (78.8%) 5 (15.2%) 6 (18.2%)
92 (52.0%) 7 (4.0%) 21 (11.9%)
.004 .011 .320
vsOVCF, very severe osteoporotic vertebral compression fracture.
of the local kyphotic angle, the VAS-BP score, and the K-ODI score (p=.415, p=.997, and p=.635, respectively; Table 3). Bone cement leakage was found in 26 cases (78.8%, 25 cases at the extraspinal location and 1 case at the spinal canal) in the vsOVCF group, and in 92 cases (52.0%, 91 cases at the extraspinal location and 1 case at the spinal canal) in the non-vsOVCF group; the vsOVCF group had a significantly higher frequency of cement leakage (p=.004). Recollapse was identified in five cases (15.2%) in the vsOVCF group and in seven cases (4.0%) in the non-vsOVCF group; the vsOVCF group had a significantly higher frequency of recollapse (p=.011). Adjacent segment fracture was found in six cases (18.2%) in the vsOVCF group and in 21 cases (11.9%) in the non-vsOVCF group, although this was not statistically significant (p=.320, Table 4). Discussion PBK can be recommended for elderly patients with OVCFs and comorbidities, as it is performed under local anesthesia and sedation, and patients can walk immediately after the operation [15,16]. Kado et al. [17] reported that in female patients aged 65 years or older, OVCFs increases patient mortality by up to 34%. This finding indicates that the successful treatment of OVCFs is closely related to the improved prognosis of the patient.
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Traditionally, OVCFs that failed by conservative treatment may have been treated by either corpectomy with anterior fusion or posterior arthrodesis, in the cases with a compression rate of 50% or more [13,18]. The risk of postoperative morbidity and mortality cannot be ignored when using this technique, as patients with OVCF are usually elderly and have comorbidities [19–21]. In particular, the implant failure might happen in patients with osteoporosis because of poor bone quality even after anterior fusion [22,23]. We performed PBK, rather than the traditional either corpectomy with anterior fusion or posterior arthrodesis, in elderly patients with a vsOVCF with the aim of reducing pain and enabling patients to walk as soon as possible after the procedure. In our study, when patients with an OVCF underwent PBK, the vertebral body height and the kyphotic angle were restored regardless of the initial compression rate and the visual analog scale and K-ODI scores improved immediately after the operation. Álvarez et al. [12] reported that patients with an OVCF who had an initial compression rate of the anterior vertebral body of less than 70% showed significantly better results than patients with an initial compression rate of more than 70%. However, in our study, patients had good results regardless of the initial compression rate, and we reported favorable results from PBK for patients with an initial compression rate of more than two-thirds. Lee et al. [6] compared the results of patients undergoing PBK by initial compression rate (30%–50%, 50%–70%, and 70% or higher) and reported that both radiological and clinical outcomes improved in all three groups. Therefore, our study supports the findings of Lee et al. Ren et al. [24] studied the factors that influence the restoration of vertebral body height following PBK in 43 patients with an OVCF and reported that the restoration of vertebral body height decreases when the compression rate of the fractured vertebral body is high. Unlike the findings of Ren et al., however, the current study found that the restoration rate of vertebral body height was significantly higher in the vsOVCF group than in the non-vsOVCF group, and therefore confirmed that PBK resulted in improved radiological results for patients with vsOVCF, consistent with our previous study [8]. In the current study, the kyphotic angle of the fractured vertebral body improved with statistical significance in both the vsOVCF and the non-vsOVCF groups immediately following PBK. This improvement was maintained at 1 year of follow-up and was statistically significant in comparison to the preoperative state. Lee et al. [6] reported an improved kyphotic angle immediately after PBK in three groups and the kyphotic angle worsened at 1 year of follow-up, and Zhang et al. [10] also reported that the kyphotic angle improved immediately after PBK and has been maintained at 1 year of follow-up. The cement leakage from the vertebral body during the injection of the cement is the most common complication [25,26]. There is the possibility that the cement might leak through either the damaged wall of the fractured vertebral body or the disk space or into a vein. The cement leakage from
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the vertebral body can compress the spinal cord and has the potential to cause a pulmonary embolism when it circulates through the vein [25,27]. In the current study, cement leakage was found in 92 cases (52.0%) in the non-vsOVCF group and in 26 cases (78.8%) in the vsOVCF group (p=.004), and this increased as the damage to the wall of the vertebral body worsened because of the increasing compression rate on the vertebral body. A high incidence of cement leakage found in this study could be explained by the strict application of leakage definition, which included any evidence of leakage beyond the vertebral body. Furthermore, as a larger degree of reduction is required in patients with vsOVCF to reach the similar reduction status as in patients with non-vsOVCF, leakage through the postreduction crack of the vertebral wall may be almost inevitable in patients with vsOVCF. However, no neurologic complications or clinically found pulmonary thromboembolisms were reported in either the non-vsOVCF or the vsOVCF group. Recollapse was found in seven cases (4.0%) in the non-vsOVCF group and in five cases (15.2%) in the vsOVCF group, and this difference was statistically significant. The risk of adjacent segment fracture following PBK is reported to be up to 25% [9,28,29]. Therefore, the cause of adjacent segment fracture is still in dispute. Lin et al. [30] reported that the cement leakage into the disk increases the risk of adjacent segment fracture during PBK, and Kim et al. [31] reported that the frequency of adjacent segment fracture increases when the fracture is located in the thoracolumbar junction and the height restoration from vertebral body is high. In the current study, 21 cases (11.9%) in the non-vsOVCF group and 6 cases (18.2%) in the vsOVCF group experienced adjacent segment fractures, although this difference was not statistically significant. The advantages of the current study include the consistency of the operative technique, as all procedures were performed by a single experienced orthopedic spine surgeon in one institution. However, the current study also has limitations, including the fact that it is a retrospective study and there is no comparison with a group of patients who underwent conservative treatment. The difference in time to PBK between the vsOVCF group and the non-vsOVCF group (which was statistically significant) is another weakness of the current study, and this is attributable to the fact that the non-vsOVCF group included more patients over 80 years old who were not treated conservatively but rather underwent PBK immediately. Third, the type of antiosteoporosis medication, which could impact the outcome of PBK, was not accounted for, and this issue should be addressed in the future study. Finally, a postoperative computed tomography scan was not routinely performed in the study, and this could lead to the underestimation of the leakage into the spinal canal. PBK for patients with an OVCF presenting with a vertebral compression rate of more than two-thirds resulted in favorable clinical outcomes comparable to those observed in patients presenting with a vertebral compression rate of less than two-thirds. However, the rates of cement leakage and
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compression fracture in the elderly patients with the spinal instrumentation. J Med Assoc Thai 2009;92:S109–15. Deyo R, Cherkin D, Loeser J, Bigos S, Ciol MA. Morbidity and mortality in association with operations on the lumbar spine. The influence of age, diagnosis, and procedure. J Bone Joint Surg Am 1992;74:536–43. Raffo CS, Lauerman WC. Predicting morbidity and mortality of lumbar spine arthrodesis in patients in their ninth decade. Spine 2006;31:99– 103. Faciszewski T, Winter RB, Lonstein JE, Denis F, Johnson L. The surgical and medical perioperative complications of anterior spinal fusion surgery in the thoracic and lumbar spine in adults: a review of 1223 procedures. Spine 1995;20:1592–9. Halvorson TL, Kelley LA, Thomas KA, Whitecloud IIITS, Cook SD. Effects of bone mineral density on pedicle screw fixation. Spine 1994;19:2415–20. Okuyama K, Abe E, Suzuki T, Tamura Y, Chiba M, Sato K. Influence of bone mineral density on pedicle screw fixation: a study of pedicle screw fixation augmenting posterior lumbar interbody fusion in elderly patients. Spine J 2001;1:402–7. Ren H, Shen Y, Zhang Y. Analysis of related factors on the vertebral height restoration of percutaneous kyphoplasty. Chinese J Spine Spinal Cord 2010;1:15.
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[25] Moreland DB, Landi MK, Grand W. Vertebroplasty: techniques to avoid complications. Spine J 2001;1:66–71. [26] Padovani B, Kasriel O, Brunner P, Peretti-Viton P. Pulmonary embolism caused by acrylic cement: a rare complication of percutaneous vertebroplasty. AJNR Am J Neuroradiol 1999;20:375–7. [27] Jensen ME, Evans AJ, Mathis JM, Kallmes DF, Cloft HJ, Dion JE. Percutaneous polymethylmethacrylate vertebroplasty in the treatment of osteoporotic vertebral body compression fractures: technical aspects. AJNR Am J Neuroradiol 1997;18:1897–904. [28] Frankel BM, Monroe T, Wang C. Percutaneous vertebral augmentation: an elevation in adjacent-level fracture risk in kyphoplasty as compared with vertebroplasty. Spine J 2007;7:575–82. [29] Movrin I, Vengust R, Komadina R. Adjacent vertebral fractures after percutaneous vertebral augmentation of osteoporotic vertebral compression fracture: a comparison of balloon kyphoplasty and vertebroplasty. Arch Orthop Trauma Surg 2010;130:1157–66. [30] Lin EP, Ekholm S, Hiwatashi A, Westesson P-L. Vertebroplasty: cement leakage into the disc increases the risk of new fracture of adjacent vertebral body. AJNR Am J Neuroradiol 2004;25:175– 80. [31] Kim S, Kang H, Choi JA, Ahn J. Risk factors of new compression fractures in adjacent vertebrae after percutaneous vertebroplasty. Acta Radiol 2004;45:440–5.
Clinical Study
Percutaneous balloon kyphoplasty for the treatment of very severe osteoporotic vertebral compression fractures: a case-control study Jin Kyu Lee, MD, Hae-won Jeong, MD, Il-Han Joo, MD, Young-Il Ko, MD, Chang-Nam Kang, MD, PhD* Department of Orthopaedic Surgery, Hanyang University College of Medicine, 222-1 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea Received 8 June 2017; revised 5 September 2017; accepted 5 October 2017
Abstract
BACKGROUND CONTEXT: Controversy exists regarding percutaneous balloon kyphoplasty (PBK) in patients with a very severe osteoporotic vertebral compression fracture (vsOVCF). PURPOSE: The study was conducted to investigate the clinical and radiological outcomes of PBK for the treatment of vsOVCF compared with those of non-vsOVCF. STUDY DESIGN/SETTING: This is a retrospective, case-control study. PATIENT SAMPLE: A total of 167 consecutive patients (210 vertebral bodies) who underwent PBK for OVCF between March 2010 and January 2015 were assessed. OUTCOME MEASURES: Visual analog scale (VAS) scores for back pain, Korean Oswestry disability index (K-ODI) scores, vertebral body height variations, and kyphotic angles were evaluated preoperatively, postoperatively, and 1 year after treatment. MATERIALS AND METHODS: Patients in the non-vsOVCF group (anterior vertebral compression of more than two-thirds on plain radiograph) who had undergone PBK where compared with those in the non-vsOVCF group (compression between 30% and two-thirds). Clinical and radiological outcomes were compared. In addition, complications were evaluated. RESULTS: In total, 31 patients (33 vertebrae) in the vsOVCF group and 136 patients (177 vertebrae) in the non-vsOVCF group were treated with PBK. Both groups had significant postoperative improvements in the clinical and radiological outcomes (VAS score, K-ODI score, vertebral body height variation, and kyphotic angle). There was no difference regarding the VAS score and the K-ODI score between the two groups at the final follow-up (p>.05). The cement leakage occurred frequently in the vsOVCF group (26 vertebrae, 78.8%) than in the non-vsOVCF group (92 vertebrae, 52.0%), the difference was statistically significant (p<.05). But there was no case that showed neurologic complication or pulmonary embolism caused by cement leakage. The incidence of recollapse was significantly higher in the vsOVCF group (five vertebrae, 15.2%) than in the non-vsOVCF group (seven vertebrae, 4.0%) (p<.05). The incidence of an adjacent segment fracture (vsOVCF group, 6 vertebrae, 18.2%; non-vsOVCF group, 21 vertebrae, 11.9%) was not significantly different (p=.320). CONCLUSIONS: Percutaneous balloon kyphoplasty is a safe and effective procedure for the treatment of vsOVCF. © 2017 Elsevier Inc. All rights reserved.
Keywords:
Clinical outcome; Complications; Osteoporosis; Percutaneous balloon kyphoplasty; Radiological outcome; Vertebral compression fracture
FDA device/drug status: Approved (percutaneous balloon kyphoplasty). Author disclosures: JKL: Nothing to disclose. HJ: Nothing to disclose. IHJ: Nothing to disclose. YIK: Nothing to disclose. CNK: Nothing to disclose. The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com. There were no sources of funding and no conflicts of interest associated with this study. * Corresponding author. Department of Orthopedic surgery, Hanyang University Medical Center, 222-1 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea. Tel. 82 2 2290 8485. E-mail address: [email protected] (C.-N. Kang). https://doi.org/10.1016/j.spinee.2017.10.006 1529-9430/© 2017 Elsevier Inc. All rights reserved.
Introduction Osteoporotic vertebral compression fractures (OVCFs) are one of the most common complications of osteoporosis, causing severe pain, restricting activity, lowering the quality of life, and also increasing the incidence of systemic complications and mortality [1,2]. Percutaneous balloon kyphoplasty (PBK) is a minimally invasive operation that involves inserting and inflating a balloon inside the vertebral body that has been damaged by the OVCF
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and then injecting cement into the void of the vertebral body [3,4]. This technique has the advantage of reducing cement leakage during surgery and may eliminate pain and restore vertebral body height immediately after surgery [5]. However, there are a limited number of studies on PBK performed in patients with a very severe osteoporotic vertebral compression fracture (vsOVCF). [3,5–10] Very severe osteoporotic vertebral compression fractures are defined by a reduction of two-thirds or more in the expected vertebral body height [11]. In patients with a vsOVCF, PBK requires advanced surgical techniques because the compression rate of the vertebral body is so severe, and some authors have argued that a vsOVCF is a relative contraindication for PBK and instead recommend conservative treatment [12]. However, others recommend either corpectomy with anterior fusion or posterior arthrodesis for patients with a vsOVCF [13,14]. We previously reported height restoration after PBK in patients with OVCF with rheumatoid arthritis [8] and hypothesized that PBK in patients with vsOVCF would recover appropriate vertebral body height and kyphotic angle and then improve clinical outcomes. We therefore conducted a comparative analysis of the clinical and radiological outcomes of PBK performed in patients with vsOVCF and in patients without vsOVCF. Materials and methods The present study investigated the patient records of 167 consecutive patients (210 vertebral bodies) who underwent PBK for OVCF at Hanyang University Hospital between March 2010 and January 2015. All patients were followed up for a minimum of 12 months (range 12–48 months). OVCFs were diagnosed in patients who complained of back pain or lower back pain, had a history of low-energy trauma and tenderness in the thoracolumbar region according to the physical examination, and manifested compression of the vertebral body on plain radiograph. Patients with an OVCF were further examined by magnetic resonance imaging or bone scan to confirm an acute fracture, and bone mineral density (BMD) was then calculated using dual-energy x-ray absorptiometry (DXA) to confirm osteoporosis. Patients who experienced discomfort in everyday life because of pain even after undergoing conservative treatment for three weeks or longer, and with a confirmed vertebral body compression rate of 30% or higher on plain radiograph were selected for the PBK procedure. For patients aged 80 years or older, PBK was performed in patients with a vertebral body compression rate of 30% or higher without the requirement of a previous conservative treatment (Figs. 1 and 2). Korean National Health Insurance covers PBK when the compression rate is 30% or higher or patients are aged 80 years or order. So we set the previously mentioned indications of PBK. Patients with either a vertebral fracture caused by highenergy trauma or a pathologic fracture caused by infection or tumor were excluded, and patients who had a fracture 3 months before the diagnosis were also excluded.
Fig. 1. Eighty-eight-year-old male patient who was admitted to our hospital after he slipped down. (A) Plain lateral radiograph shows the osteoporotic vertebral compression fracture of the L1 vertebra with 80% severe collapse and 33° local kyphosis. (B) T1 sagittal magnetic resonance imaging shows an acute recent fracture of the L1 vertebra. (C) Intraoperative fluoroscope shows a Jamshidi needle (guide pin) inserted in the L1 vertebra. (D) A percutaneous balloon tamp was inflated and reduced the collapse of the vertebral height. Immediate postoperation (E) and 1-year follow-up (F) lateral plain radiograph. The body height and the kyphotic angle improved and remained stable 1 year after the operation.
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Fig. 2. Eighty-three-year-old male patient who was admitted our hospital after he slipped down. (A) Plain lateral radiograph shows the osteoporotic vertebral compression fracture of the T12 vertebra with a 42% severe collapse and a 37° local kyphosis. (B) T1 sagittal magnetic resonance imaging shows an acute recent fracture of the T12 vertebra. (C) Intraoperative fluoroscope shows a Jamshidi needle inserted in the T12 vertebra. (D) A percutaneous balloon tamp was inflated and reduced the collapse of the vertebral height. Immediate postoperation (E) and 1-year follow-up (F) lateral plain radiograph. The body height and the kyphotic angle improved and remained stable 1 year after the operation. (G) A postoperative computed tomography scan with axial image shows no cement leakage into the spinal canal.
Among the patients who underwent PBK, those who had an anterior vertebral compression of more than two-thirds on plain radiograph were classified as the vsOVCF group, and patients with an anterior vertebral compression between 30% and two-thirds were classified as the non-vsOVCF group. The surgery was performed by a single surgeon at one institution. All patients were treated with local anesthesia and sedation followed by a conventional bilateral transpedicular approach in the prone position. Prophylactic antibiotics were administered 30 minutes before surgery, and blood pressure, pulse, and oxygen saturation were checked during the surgery. The bone cement injection and leakage were monitored using C-arm fluoroscopy during the surgery (Figs. 1 and 2). With any doubt of cement leakage into the spinal canal on the fluoroscopy, cement injection was stopped at the corresponding needle. The bone cement used was polymethyl methacrylate, and the injection time was measured from the time the polymethyl methacrylate was polymerized to the time the injection began. The cement volume is the total volume
of cement injected on both sides. Patients began to walk by themselves immediately after the operation. For the measurement of clinical outcomes, the visual analog scale for back pain (VAS-BP) and the Korean Oswestry disability index (K-ODI) scores were evaluated preoperatively, postoperatively, and 1 year after the operation. Radiological outcomes were evaluated by an orthopedic spine fellow and an orthopedic resident, who both underwent the same training twice at 2-week intervals. The anterior height of the fractured vertebral body and the difference in the kyphotic angle of the local segment were measured preoperatively, postoperatively, and 1 year after operation, as were cement leakage, recollapse of the cemented vertebral body, and any adjacent segment fracture. The vertebral body compression rate was calculated as a percentage of the average adjacent superior and inferior anterior vertebral body heights measured from a plain lateral radiograph taken in an erect posture. Recollapse was defined when the anterior vertebral body height decreased by 5% or more within 1 year of the operation, in
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comparison with the anterior vertebral body height recovered immediately following the operation. The kyphotic angle of the local segment was calculated from the Cobb angle formed by the superior end plate of the upper vertebral body of the fractured vertebra and the inferior end plate of the lower vertebral body. Cement leakage was examined using anteroposterior and lateral plain radiographs, and an additional computed tomography scan was performed when the spinal canal involvement was in doubt (Fig. 3). Cement leakage was defined as any evidence of leakage beyond the vertebral body. The age, gender, and BMD of each patient at the time of surgery were recorded in the electronic medical record. Statistical analyses SPSS version 20.0 (SAS Institute, Cary, NC, USA) was used for all statistical analyses. The paired t test was used to compare the vertebral body compression rate and the kyphotic angle preoperatively, postoperatively, and 1 year after surgery. The chi-square test was used to compare bone cement leakage, recollapse, and adjacent segment fracture between the groups. The independent t test was used for a comparative analysis of continuous data, and the Cohen kappa coefficient was used to analyze intra- and interobserver reliability. Statistical significance was set at p<.05. Results Interobserver and intraobserver reliabilities The kappa coefficients for intraobserver reliability for vertebral body height and kyphotic angle, as measured on preoperative and postoperative radiographs, were 0.85 (95% confidence interval 0.74–0.95) and 0.89 (95% confidence interval 0.79–0.99), respectively. The kappa coefficients for interobserver reliability were 0.74 (95% confidence interval 0.59–0.88) and 0.75 (95% confidence interval 0.64–0.87), respectively, indicating high conformity. Demographic data Thirty-one patients (33 vertebral bodies) had a vertebral compression rate of more than two-thirds and were therefore categorized in the vsOVCF group, and 136 patients (177 vertebral bodies) had a vertebral compression rate between 30% and two-thirds, and were therefore categorized in the non-vsOVCF group. The two groups were not significantly different in terms of age, gender, body mass index, or BMD (p=.615, p=.524, p=.663, and p=.214, respectively). There was no statistical difference between the two groups with regard to the location of the fracture (p=.161). The average time between the fracture and PBK was 23.6 days in the vsOVCF group and 19.0 days in the non-vsOVCF group (p=.019). Comorbidities included hypertension, diabetes, stroke, rheumatoid arthritis, and cardiovascular diseases, and there were no statistical differences between the vsOVCF and the
Fig. 3. Seventy-nine-year-old female patient who was admitted to our hospital after she slipped down. (A) Plain lateral radiograph shows the osteoporotic vertebral compression fracture of the L1 vertebra with a 68% severe collapse and an 11° local kyphosis. (B) T1 sagittal magnetic resonance imaging shows an acute recent fracture of the L1 vertebra. Immediate postoperation (C) and 1-year follow-up (D) lateral plain radiograph. The body height and the kyphotic angle improved and remained stable 1 year after the operation. Immediate postoperation computed tomography sagittal (E) and axial (F) images show a leakage of the cement (arrows) into the spinal canal.
non-vsOVCF groups (p=.273, p=.358, p=.512, p=.412, p=.344, respectively; Table 1). Comparison of radiographic and clinical outcomes In the vsOVCF group, the rates of the anterior height of the fractured vertebral bodies were 29.4%±4.0% preoperatively
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Table 1 Demographic data vsOVCF Age (y) Gender(n) Female Male BMI (kg/m2) BMD (g/cm2) BMD (T-score) No. of involved vertebra T9 T10 T11 T12 L1 L2 L3 L4 L5 Time to surgery (d) Comorbidity (n) Hypertension Diabetes Stroke RA Cardiovascular disease
Non-vsOVCF
p-Value
75.0±8.1
74.3±7.1
.615
23 8 22.9±3.1 0.48 −3.2±0.9
108 28 23.2±3.3 0.51 −3.2±0.9
.524 .663 .214 .813
2 1 2 11 11 3 1 2 0 23.6
1 2 15 37 59 32 13 13 5 19.0
.161
.019
20 11 2 1 1
73 37 14 12 11
.273 .358 .512 .412 .344
BMI, body mass index; BMD, bone mineral density; T, thoracic vertebra; L, lumbar vertebra; RA, rheumatoid arthritis; vsOVCF, very severe osteoporotic vertebral compression fracture. Values are given as mean±standard deviation.
and 61.4%±11.7% postoperatively, indicating that the vertebral height was restored with statistical significance (p<.001). In the non-vsOVCF group, the rates of the anterior height of the fractured vertebral bodies were 64.3%±16.0% preoperatively and 77.6%±13.5% postoperatively, also indicating that height was restored with statistical significance (p<.001). In the vsOVCF group, the local kyphotic angle was 19.6±11.7 preoperatively and 16.2±12.0 postoperatively, and in the nonvsOVCF group, the local kyphotic angle was 17.7±10.5
preoperatively and recovered to 15.3±10.1 postoperatively; both groups showed a statistically significant improvement in the kyphotic angle (p<.001, respectively). At the 1-year follow-up, the local kyphotic angle remained improved in both the vsOVCF and the non-vsOVCF groups (17.1±11.5 and 16.2±11.6, p=.011 and p=.008, respectively). In the vsOVCF group, the VAS-BP score recovered from 7.6±1.3 preoperatively and 3.9±1.5 postoperatively, and in the non-vsOVCF group, the VAS-BP score recovered from 7.3±1.9 preoperatively and 3.6±1.7 postoperatively; the improvement was statistically significant for both groups (p<.001, respectively). In the vsOVCF group, the K-ODI score recovered from 32.2±5.6 preoperatively and 19.7±5.2 postoperatively, in the non-vsOVCF group, the K-ODI score recovered from 31.4±7.3 preoperatively and 19.2±7.6 postoperatively; this improvement was statistically significant for both groups (p<.001, respectively; Table 2). The cement volume used during PBK was 6.8±1.8 cc in the vsOVCF group and 6.9±1.9 cc in the non-vsOVCF group; there was no significant difference between the two groups (p=.642). Cement injection time was 10.0±3.0 minutes in the vsOVCF group and 10.0±2.5 minutes in the non-vsOVCF group, with no significant differences between the two groups (p=.986). The height restoration of the anterior vertebral body was 32.0%±10.9% in the vsOVCF group and 13.4%±13.1% in the non-vsOVCF group, indicating a statistically significant improvement in the height restoration of vertebral body in the vsOVCF group (p<.001). When comparing the postoperative state with the preoperative state, there were no significant differences between the two groups in terms of the degree of improvement in the local kyphotic angle, the VAS-BP score, and the K-ODI score (p=.387, p=.968, p=.826, respectively). When comparing the preoperative state with the state at the 1-year follow-up, the height restoration of the anterior vertebral body was significantly high in the vsOVCF group (p<.001); however, the two groups did not show any significant differences in terms of the degree of improvement
Table 2 Comparison of radiographic and clinical outcomes
Height rate (%) vsOVCF Non-vsOVCF Kyphotic angle (°) vsOVCF Non-vsOVCF VAS-BP vsOVCF Non-vsOVCF K-ODI vsOVCF Non-vsOVCF
Preoperative
Postoperative
1-y Follow-up
p-Value
29.4±4.0 64.3±16.0
61.4±11.7 77.6±13.5
57.9±10.3 72.9±12.5
.000*/.000* .000*/.000*
19.6±11.7 17.7±10.5
16.2±12.0 15.3±10.1
17.1±11.5 16.2±11.6
.000*/.011 .000*/.008
7.6±1.3 7.3±1.9
3.9±1.5 3.6±1.7
2.3±1.0 2.0±1.1
.000*/.000* .000*/.000*
32.2±5.6 31.4±7.3
19.7±5.2 19.2±7.6
16.7±6.1 16.5±7.0
.000*/.000* .000*/.000*
VAS-BP, visual analog scale for back pain; K-ODI, Korean Oswestry disability index; vsOVCF, very severe osteoporotic vertebral compression fracture. Values are given as mean±standard deviation. p-Value: preoperative versus postoperative and preoperative versus 1-year follow-up. * p<.001.
J.K. Lee et al. / The Spine Journal 18 (2018) 962–969 Table 3 Comparison of vsOVCF and non-vsOVCF vsOVCF
Non-vsOVCF p-Value
Cement volume (cc) 6.8±1.8 6.9±1.9 Cementation time (min) 10.0±3.0 10.0±2.5 Height of fractured vertebra (mm) 7.9±1.4 17.2±4.6 Vertebral body collapse (%) 0.3±0.1 0.6±0.1 Postop-preop comparison Height restoration (%) 32.0±10.9 13.4±13.1 Local kyphosis variation (°) −3.4±4.8 −2.4±6.4 VAS variation −3.7±1.8 −3.7±2.0 K-ODI variation −12.4±4.1 −12.2±5.6 1-y Follow-up—preop comparison Height restoration (%) 28.5±10.1 8.6±13.3 Local kyphosis variation (°) −2.6±5.4 −1.5±7.3 VAS variation −5.3±1.7 −5.3±1.9 K-ODI variation −15.4±5.1 −14.9±5.4
.642 .986 .000* .000* .000* .387 .968 .826 .000* .415 .997 .635
VAS, visual analog scale; K-ODI, Korean Oswestry disability index; vsOVCF, very severe osteoporotic vertebral compression fracture. Values are given as mean±standard deviation. * p<.001.
Table 4 Postoperative complications
Cement leakage Recollapse Adjacent segment fracture
vsOVCF
Non-vsOVCF
p-Value
26 (78.8%) 5 (15.2%) 6 (18.2%)
92 (52.0%) 7 (4.0%) 21 (11.9%)
.004 .011 .320
vsOVCF, very severe osteoporotic vertebral compression fracture.
of the local kyphotic angle, the VAS-BP score, and the K-ODI score (p=.415, p=.997, and p=.635, respectively; Table 3). Bone cement leakage was found in 26 cases (78.8%, 25 cases at the extraspinal location and 1 case at the spinal canal) in the vsOVCF group, and in 92 cases (52.0%, 91 cases at the extraspinal location and 1 case at the spinal canal) in the non-vsOVCF group; the vsOVCF group had a significantly higher frequency of cement leakage (p=.004). Recollapse was identified in five cases (15.2%) in the vsOVCF group and in seven cases (4.0%) in the non-vsOVCF group; the vsOVCF group had a significantly higher frequency of recollapse (p=.011). Adjacent segment fracture was found in six cases (18.2%) in the vsOVCF group and in 21 cases (11.9%) in the non-vsOVCF group, although this was not statistically significant (p=.320, Table 4). Discussion PBK can be recommended for elderly patients with OVCFs and comorbidities, as it is performed under local anesthesia and sedation, and patients can walk immediately after the operation [15,16]. Kado et al. [17] reported that in female patients aged 65 years or older, OVCFs increases patient mortality by up to 34%. This finding indicates that the successful treatment of OVCFs is closely related to the improved prognosis of the patient.
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Traditionally, OVCFs that failed by conservative treatment may have been treated by either corpectomy with anterior fusion or posterior arthrodesis, in the cases with a compression rate of 50% or more [13,18]. The risk of postoperative morbidity and mortality cannot be ignored when using this technique, as patients with OVCF are usually elderly and have comorbidities [19–21]. In particular, the implant failure might happen in patients with osteoporosis because of poor bone quality even after anterior fusion [22,23]. We performed PBK, rather than the traditional either corpectomy with anterior fusion or posterior arthrodesis, in elderly patients with a vsOVCF with the aim of reducing pain and enabling patients to walk as soon as possible after the procedure. In our study, when patients with an OVCF underwent PBK, the vertebral body height and the kyphotic angle were restored regardless of the initial compression rate and the visual analog scale and K-ODI scores improved immediately after the operation. Álvarez et al. [12] reported that patients with an OVCF who had an initial compression rate of the anterior vertebral body of less than 70% showed significantly better results than patients with an initial compression rate of more than 70%. However, in our study, patients had good results regardless of the initial compression rate, and we reported favorable results from PBK for patients with an initial compression rate of more than two-thirds. Lee et al. [6] compared the results of patients undergoing PBK by initial compression rate (30%–50%, 50%–70%, and 70% or higher) and reported that both radiological and clinical outcomes improved in all three groups. Therefore, our study supports the findings of Lee et al. Ren et al. [24] studied the factors that influence the restoration of vertebral body height following PBK in 43 patients with an OVCF and reported that the restoration of vertebral body height decreases when the compression rate of the fractured vertebral body is high. Unlike the findings of Ren et al., however, the current study found that the restoration rate of vertebral body height was significantly higher in the vsOVCF group than in the non-vsOVCF group, and therefore confirmed that PBK resulted in improved radiological results for patients with vsOVCF, consistent with our previous study [8]. In the current study, the kyphotic angle of the fractured vertebral body improved with statistical significance in both the vsOVCF and the non-vsOVCF groups immediately following PBK. This improvement was maintained at 1 year of follow-up and was statistically significant in comparison to the preoperative state. Lee et al. [6] reported an improved kyphotic angle immediately after PBK in three groups and the kyphotic angle worsened at 1 year of follow-up, and Zhang et al. [10] also reported that the kyphotic angle improved immediately after PBK and has been maintained at 1 year of follow-up. The cement leakage from the vertebral body during the injection of the cement is the most common complication [25,26]. There is the possibility that the cement might leak through either the damaged wall of the fractured vertebral body or the disk space or into a vein. The cement leakage from
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the vertebral body can compress the spinal cord and has the potential to cause a pulmonary embolism when it circulates through the vein [25,27]. In the current study, cement leakage was found in 92 cases (52.0%) in the non-vsOVCF group and in 26 cases (78.8%) in the vsOVCF group (p=.004), and this increased as the damage to the wall of the vertebral body worsened because of the increasing compression rate on the vertebral body. A high incidence of cement leakage found in this study could be explained by the strict application of leakage definition, which included any evidence of leakage beyond the vertebral body. Furthermore, as a larger degree of reduction is required in patients with vsOVCF to reach the similar reduction status as in patients with non-vsOVCF, leakage through the postreduction crack of the vertebral wall may be almost inevitable in patients with vsOVCF. However, no neurologic complications or clinically found pulmonary thromboembolisms were reported in either the non-vsOVCF or the vsOVCF group. Recollapse was found in seven cases (4.0%) in the non-vsOVCF group and in five cases (15.2%) in the vsOVCF group, and this difference was statistically significant. The risk of adjacent segment fracture following PBK is reported to be up to 25% [9,28,29]. Therefore, the cause of adjacent segment fracture is still in dispute. Lin et al. [30] reported that the cement leakage into the disk increases the risk of adjacent segment fracture during PBK, and Kim et al. [31] reported that the frequency of adjacent segment fracture increases when the fracture is located in the thoracolumbar junction and the height restoration from vertebral body is high. In the current study, 21 cases (11.9%) in the non-vsOVCF group and 6 cases (18.2%) in the vsOVCF group experienced adjacent segment fractures, although this difference was not statistically significant. The advantages of the current study include the consistency of the operative technique, as all procedures were performed by a single experienced orthopedic spine surgeon in one institution. However, the current study also has limitations, including the fact that it is a retrospective study and there is no comparison with a group of patients who underwent conservative treatment. The difference in time to PBK between the vsOVCF group and the non-vsOVCF group (which was statistically significant) is another weakness of the current study, and this is attributable to the fact that the non-vsOVCF group included more patients over 80 years old who were not treated conservatively but rather underwent PBK immediately. Third, the type of antiosteoporosis medication, which could impact the outcome of PBK, was not accounted for, and this issue should be addressed in the future study. Finally, a postoperative computed tomography scan was not routinely performed in the study, and this could lead to the underestimation of the leakage into the spinal canal. PBK for patients with an OVCF presenting with a vertebral compression rate of more than two-thirds resulted in favorable clinical outcomes comparable to those observed in patients presenting with a vertebral compression rate of less than two-thirds. However, the rates of cement leakage and
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