Author's response to reviews

Author's response to reviews Title: Reduction of the domino effect in osteoporotic vertebral compression fractures through short-segment fixation with intravertebral expandable pillars compared to percutaneous kyphoplasty. A case control study. Authors: Jui-Yang Hsieh (ocean_x5@yahoo.com.tw) Chung-Ding Wu (ctwu@hotmail.com) Ting-Ming Wang (dtorth76@yahoo.com.tw) Hsuan-Yu Chen (hychen83@gmail.com) Chui-Jia Farn (cjfarn@gmail.com) Po-Quang Chen (pq_chen@yahoo.com.tw) Version: 8 Date: 24 November 2012 Author's response to reviews: see over

Dear Editor in Chief & Reviewers: Thank you for your comments. I am honored to be revised the manuscript by Jui-Yang Hsieh, Chung-Ding Wu, Ting-Ming Wang, Hsuan-Yu Chen, Chui-Jia Farn and Po-Quang Chen, titled " Reduction of the domino effect in osteoporotic vertebral compression fractures through short-segment fixation with intravertebral expandable pillars compared to percutaneous kyphoplasty. A case control study." The revised manuscript is totally modified with complete introduction and comprehensive discussion according to the reviewers' all comments. The "red words" highlight in revised manuscript was provided a detailed point-by-point response to the referee 1's concerns. The "underlined" highlight in revised manuscript was provided a detailed point-by-point response to the referee 2's concerns. The "yellow screentone" highlight in revised manuscript was provided a detailed point-by-point response to the referee 3's concerns. We believe the paper may be of particular interest to the readers of your journal. Correspondence and phone calls about the paper should be directed to Po-Quang Chen at the following address, phone and e-mail address: Corresponding author: Po-Quang Chen, MD, PhD Department of Orthopedics, College of Medicine, National Taiwan University & Hospital No.7, Chung-Shan South Road, Taipei, Taiwan Phone: 886-2-23123456-62137, 886-9-28899988 Fax: 886-2-2393-6577 Email address: pq_chen@yahoo.com.tw; pqchen@ntu.edu.tw Thanks very much for your attention to our paper. Sincerely yours, Po-Quang Chen Reviewer 1 report Title: Less Domino effects in Short-Segment Fixation with Intravertebral Expandable Pillars Compared to Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fractures Version: 2 Date: 27 August 2012

Reviewer: Toru Maruyama Reviewer's report: This is a study comparing short fusion using I-VEP and BKP for the treatment of osteoporotic vertebral fracture. There were no differences in the clinical results, but in some of the radiological parameters. Please organize some points, especially about the results. Major compulsory revisions 1 Were there any new fractures at the adjacent vertebrae 1 year after surgery? Patient 1 in Group I (an 85-year-old woman), who was treated with short-segment fixation with I-VEP due to VCF of L3, suffered a further collapse at T12 three months after the operation. The anterior vertebral height of T12 reduced from 27.5 mm before the operation to 8.6 mm at 3 months postoperatively; this value remained the same at the 1-year follow-up examination (Fig. 6). However, T12 was not defined as a caudal vertebral fracture is this case. It is also difficult to differentiate a novel instance of VCF from the natural process of aging or a complication related to short-segment fixation with I-VEP. [P. 8-9] Fig. 6 a The lateral view of Patient 1 in Group I shows an L3 vertebral compression fracture and an intact T12 before the operation. b T12 was further collapsed at the three-month follow-up. c The T12 VCF remains at the one-year follow-up. d Anteroposterior view, preoperative radiograph. e Anteroposterior view, three-month follow-up. f Anteroposterior view, one-year follow-up. [P. 23]

2 Local kyphosis index should include the disc spaces. Fig. 5 Schematic diagrams of the radiographic measurements. a The anterior vertebral body height (double arrow) is the actual height of the anterior cortex of the vertebral body as measured on the lateral radiograph. b Measuring on a lateral radiograph with modified Cobb method requires inferior endplates of the vertebral body for kyphotic angle measurement. [P. 22]

3 Please add the mean and SD on the tables and text in the result section. The mean preoperative VAS pain score was 8.9 ± 0.7 in Group I and 7.96 ± 0.61 in Group II. The mean preoperative AH was 12.44 ± 6.22 mm in Group I and 15.54 ± 7.22 mm in Group II. The mean preoperative KA was 18.17 ± 8.16 in Group I and 21.58 ± 4.35 in Group II. The mean preoperative AH above the fracture was 25.86 ± 5.4 mm in Group I and 21.27 ± 5.88 mm in Group II. The mean preoperative AH below the fracture was 26.08 ± 6.18 mm in Group I and 28.33 ± 4.08 mm in Group II. The mean preoperative KA above the fracture was 4.76 ± 5.73 in Group I and 9.32 ± 6.71 in Group II. The mean preoperative KA below the fracture was 5.11 ± 6.65 in Group I and 4.68 ± 3.7 in Group II. The mean postoperative VAS pain score was 1.5 ± 1.3 in Group I and 2.08 ± 0.72 in Group II. The mean postoperative AH was 19.57 ± 3.89 mm in Group I and 21.36 ± 1.24 mm in Group II. The mean postoperative KA was 9.67 ± 5.18 in Group I and 2.75 ± 2.18 in Group II. The mean postoperative AH above the fracture was 25.67 ± 5.29 mm in Group I and 27.35 ± 4.37 mm in Group II. The mean postoperative AH below the fracture was 26.2 ± 6.2 mm in Group I and 27.35 ± 4.37 mm in Group II. The mean postoperative KA above the fracture was 4.84 ± 5.67 in Group I and 9.87 ± 6.36 in Group II. The mean postoperative KA below the fracture was 4.55 ± 6.61 in Group I and 4.84 ± 3.17 in Group II. [P. 7]

4 Please add unit on the tables. Table 1 Demographic and clinical characteristics of Group I patients treated with short-segment fixation with I-VEP. VAS = visual analogue scale; AH = anterior vertebral height; KA = kyphotic angle; AH above = anterior vertebral height above the fracture segment; AH below = anterior vertebral height below the fracture segment; SD = standard deviation [P. 26]

Table 2 Demographic and clinical characteristics of Group II patients treated with kyphoplasty. VAS = visual analogue scale; AH = anterior vertebral height; KA = kyphotic angle; AH above = anterior vertebral height above the fracture segment; AH below = anterior vertebral height below the fracture segment; SD = standard deviation [P. 27]

5 Is AH an absolute length of the vertebral height? The AH is an actual height of the anterior cortex of the vertebral body measured on the lateral radiograph (the double blue arrow). [P. 22] 6 Are there no differences between groups in all the KA and AH before surgery? Preoperatively, there was no significant difference between the groups in terms of the symptomatic level (p = 0.845), VAS score (p = 0.539), KA (p = 0.43) or AH above the injury (p = 0.196). On average, Group II patients (79.3 years) were older than Group I patients (73.6 years) (p = 0.008). Before the operation, the AH and AH below the fracture values were lower in Group I patients as compared to Group II patients (p = 0.004 and p < 0.001, respectively). Preoperative measurements of KA above the fracture were larger in Group II as compared to Group I (p = 0.009). KA below the fracture was higher in Group I than Group II patients (p < 0.001) before the operation. Notably, the data were adjusting for preexisting differences in terms of gender, fracture level, age, and preoperative clinical data using the analysis of covariance for two nonequivalent groups. [P. 8]

7 KA was larger in the short fusion group despite AH was not different. Does this mean that posterior vertebral height of the BKP group was smaller at the fractured vertebra? KA of the cranial adjacent vertebra was smaller in the short fusion group despite AH was not different. Does this mean that posterior vertebral height of the short fusion group was smaller at the cranial adjacent vertebra? KA of the caudal adjacent vertebra was not different despite AH was larger in the short fusion group. Does this mean that posterior vertebral height of the BKP group was smaller at the caudal adjacent vertebra? Vertebral body height was only measured in the anterior cortex; a more complete analysis would have included measurements of the anterior, central and posterior cortices. The simplicity of our analysis, which considered only the VAS pain assessment and two radiological parameters (AH, KA), allowed for direct evaluation of the most relevant experimental parameters. Measurements of posterior vertebral height at the fractured vertebrae in the KP group would have obfuscated the central question of our research, because the short fusion group would have yielded similar AH values but larger KA values. Similarly, posterior vertebral height would be reduced at the cranial adjacent vertebra in the short fusion group due to the smaller KA values of these vertebrae, despite the similarity of the AH values. Along the same lines, posterior vertebral height at the caudal adjacent vertebra would have been reduced in the KP group due to KA values that were similar to those of the caudal adjacent vertebra, despite larger AH in the short-fusion group. The results of various surgical techniques should be further evaluated and analyzed with respect to posterior vertebral height. [P. 11]

Minor essential revisions Could the authors add the photo of the I-VEP? Fig. 2 Patient 5 in Group I is a 79-year-old man who was treated with short-segment fixation with I-VEP due to VCF of L2. a Lateral-view radiographs of Patient 5 in Group I show an L2 vertebral compression fracture before the operation. b Anteroposterior view of the preoperative radiograph. c Lateral-view radiographs at the one-year follow-up. d Anteroposterior view at the one-year follow-up. [P. 19] Fig. 3 Patient 20 in Group I (70 years old female) with an L3 concave H-shaped burst fracture underwent I-VEP insertion at L3 combined with additional short segment fixation (L2-L4). a Preoperative CT, sagittal view. b Preoperative CT, axial view. c Lateral-view radiograph taken postoperatively. d Anteroposterior-view radiograph, taken postoperatively. [P. 20]

Fig. 7 Illustration of I-VEP placement. a Detection of the pedicle tract, insertion of the probe to the collapse area and entrance into the center of the vertebra in the sagittal plane. b Convergent insertion of I-VEP into the vertebrae 2 mm away from the anterior cortex after dilatation of the tract and creation of void space. c Pack both inside and out with bone chips in the hollow I-VEP. [P. 24] Fig. 8 a The I-VEP is in resting status. b The I-VEP is in expanding status. [P. 25] Level of interest: An article whose findings are important to those with closely related research interests Quality of written English: Acceptable Statistical review: No, the manuscript does not need to be seen by a statistician. Declaration of competing interests: I declare that I have no competing interests. Toru Maruyama

Reviewer 2 report Title: Less Domino effects in Short-Segment Fixation with Intravertebral Expandable Pillars Compared to Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fractures Version: 2 Date: 16 September 2012 Reviewer: Tomasz Kotwicki Reviewer's report: Reviewer s comments This interesting paper compares results of two different techniques of surgical treatment of VCF in nearly comparable groups of patients. The study is retrospective however consecutive patients are considered. The evaluation is rather simple in methodology with VAS scale pain assessment and two radiological parameters (AH, KA). This simplicity of analysis can be considered advantageous. The number of patients in each group is small, minimal but sufficient for statistical analysis. The paper is logically constructed and easy to read.

Major revisions 1. The tables 1 and 2 should be completed by reporting minima, maxima, means and standard deviations when appropriate. Table 1 Demographic and clinical characteristics of Group I patients treated with short-segment fixation with I-VEP. VAS = visual analogue scale; AH = anterior vertebral height; KA = kyphotic angle; AH above = anterior vertebral height above the fracture segment; AH below = anterior vertebral height below the fracture segment; SD = standard deviation [P. 26]

Table 2 Demographic and clinical characteristics of Group II patients treated with kyphoplasty. VAS = visual analogue scale; AH = anterior vertebral height; KA = kyphotic angle; AH above = anterior vertebral height above the fracture segment; AH below = anterior vertebral height below the fracture segment; SD = standard deviation [P. 27]

2. In such type of comparative analysis the complications of treatment in each group should be carefully listed even if the main goal of the study is oriented towards analyzing radiological parameters. The complications are not reported even if mentioned in Discussion section. No case of I-VEP fatigue, anterior or posterior loss of I-VEP, pulmonary embolism, cement extravasation, or infection was reported. However, one patient experienced operation-related complications. One patient (patient 8 in Group I) experienced right-leg weakness soon after the operation. The patient had recovered completely by the 6-week follow-up. Patient 1 in Group I (an 85-year-old woman), who was treated with short-segment fixation with I-VEP due to VCF of L3, suffered a further collapse at T12 three months after the operation. The anterior vertebral height of T12 reduced from 27.5 mm before the operation to 8.6 mm at 3 months postoperatively; this value remained the same at the 1-year follow-up examination (Fig. 6). However, T12 was not defined as a caudal vertebral fracture is this case. It is also difficult to differentiate a novel instance of VCF from the natural process of aging or a complication related to short-segment fixation with I-VEP. [P. 8-9]

Fig. 6 a The lateral view of Patient 1 in Group I shows an L3 vertebral compression fracture and an intact T12 before the operation. b T12 was further collapsed at the three-month follow-up. c The T12 VCF remains at the one-year follow-up. d Anteroposterior view, preoperative radiograph. e Anteroposterior view, three-month follow-up. f Anteroposterior view, one-year follow-up. [P. 23]

3. The Conclusions section should be rewritten in order to limit it to what was really proven in this study. The first sentence of Conclusions Elderly patients with VCF have a tendency to receive KP is not directly proved by this study and represents just observation of a tendency coming from analysis of two very short series. In general, the limited methodology (pain and two radiological parameters KA and AH) should encourage the authors to propose limited conclusions. The percutaneous injection of PMMA is recommended for the relief of pain among extremely senile patients with complicated comorbid diseases. The results presented here show that, after adjustment for gender, fracture level and age, kyphoplasty was superior to other surgical techniques in restoring the kyphotic deformity of collapsed vertebral bodies in VCF patients. The use of short-segment fixation with I-VEP to preserve AH below and KA above the level of the fracture kept the adjacent segments intact, which may offer an alternative treatment for patients with VCF. This approach offers a comparable level of pain relief, maintains the integrity of adjacent structures, and reduces the likelihood of a domino effect up to one year postoperatively. [P. 12]

Minor revisions 1. Results section, second chapter, first sentence: replace clinical outcome with parameters measured. Clinical outcome is much more than what have been measured in this study. Also, parallel remark concerns abstract write simply what you measured. 2. The term of adjustment for gender, fracture level and age is introduced in Abstract, Results and in Conclusions, however there is no information what this adjustment consisted of. Preoperatively, there was no significant difference between the groups in terms of the symptomatic level (p = 0.845), VAS score (p = 0.539), KA (p = 0.43) or AH above the injury (p = 0.196). On average, Group II patients (79.3 years) were older than Group I patients (73.6 years) (p = 0.008). Before the operation, the AH and AH below the fracture values were lower in Group I patients as compared to Group II patients (p = 0.004 and p < 0.001, respectively). Preoperative measurements of KA above the fracture were larger in Group II as compared to Group I (p = 0.009). KA below the fracture was higher in Group I than Group II patients (p < 0.001) before the operation. Notably, the data were adjusting for preexisting differences in terms of gender, fracture level, age, and preoperative clinical data using the analysis of covariance for two nonequivalent groups. The postoperative measurements were also compared between groups. There was no significant difference between the groups in terms of VAS score (p = 0.198), AH (p = 0.775), AH above the fracture (p = 0.64) or KA below the fracture (p = 0.266). However, KA and AH below the fracture were significantly higher in Group I than in Group II (p < 0.001 and p = 0.029, respectively). KA above the fracture was significantly larger in Group II than in Group I (p = 0.008). [P. 8]

3. Try to limit the use of abbreviations in the Abstract. Abstract Background Osteoporotic vertebral compression fracture is the leading cause of disability and morbidity in elderly people. Treatment of this condition remains a challenge. Osteoporotic vertebral compression fractures can be managed with various approaches, but each has limitations. In this study, we compared the clinical outcomes obtained using short-segment fixation with intravertebral expandable pillars (I-VEP) to those obtained with percutaneous kyphoplasty in patients who had suffered vertebral compression fractures. Methods The study included 46 patients with single-level osteoporotic thoracolumbar fractures. Twenty-two patients in Group I underwent short-segment fixation with I-VEP and 24 patients in Group II underwent kyphoplasty. All patients were evaluated pre- and postoperatively using a visual analogue scale, anterior vertebral height, and the kyphotic angle of the lesion site. The latter 2 radiological parameters were measured at the adjacent segments as well. Results There was no significant difference between the groups in terms of gender or fracture level, but the mean age was greater in Group II patients (p = 0.008). At the 1-year follow-up, there were no significant differences in the visual analogue scale scores, anterior vertebral height, or the value representing anterior vertebral height above and kyphotic angle below the fracture segment, after adjusting for the patients gender, fracture level, and age. When considered separately, the kyphotic angle and anterior

vertebral height below the fracture segment were both higher in Group I than in Group II (p < 0.001 and p = 0.029, respectively). The kyphotic angle above the fracture segment was significantly larger in Group II than in Group I (p = 0.008).] Conclusions In older individuals with vertebral compression fractures, kyphoplasty restored and maintained the collapsed vertebral body with less kyphotic deformity than that induced by short-segment fixation with I-VEP. Short-segment fixation with I-VEP was more effective in maintaining the integrity of adjacent segments, which prevented the domino effect often observed in patients with osteoporotic kyphotic spines. [P. 2-3]

Discretionary revisions 1. The conclusion regarding advantages of I-VEP would be stronger if the immediate and early results in pain relief were reported. The immediate pain relief is crucial for the patients to regain normal activity. The I-VEP method seems more invasive so the recovery might be not so rapid as after KP? The use of short-segment fixation with I-VEP to preserve AH below and KA above the level of the fracture kept the adjacent segments intact, which may offer an alternative treatment for patients with VCF. This approach offers a comparable level of pain relief, maintains the integrity of adjacent structures, and reduces the likelihood of a domino effect up to one year postoperatively. However, the immediate and early pain relief achieved with kyphoplasty may be more meaningful than the long-term prevention of a domino effect in extremely senile patients with comorbidities. Further research about the biomechanical stability of the spine in this context and more long-term clinical data will be needed to definitively evaluate the role of the two techniques in the treatment of patients with VCF. [P. 12]

2. In Group I, it is not clear from the text if one level above and one level below signifies the levels receiving the pedicle screws. All patients assessed their pain before and 1 year after surgery using a 10-cm visual analogue scale (VAS). Imaging using a compression ratio of height of the anterior vertebra (AH) and local kyphotic deformity angle (KA) was performed prior to the procedure and 12 months postoperatively (Fig. 5). Measurements of AH and KA in adjacent cephalic and caudal segments were radiographically documented just above or below the fracture level despite the presence of pedicle screws. [P. 6] Level of interest: An article whose findings are important to those with closely related research interests Quality of written English: Acceptable Statistical review: No, the manuscript does not need to be seen by a statistician. Declaration of competing interests: I declare that I have no competing interests.

Reviewer 3 report Title: Less Domino effects in Short-Segment Fixation with Intravertebral Expandable Pillars Compared to Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fractures Version: 2 Date: 16 September 2012 Reviewer: Theodoros B Grivas Reviewer's report: Less Domino effects in Short-Segment Fixation with Intravertebral Expandable Pillars Compared to Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fractures Major limitations As it appears from the text, the follow up is only one year. If it is different please specify. The appearance of complications in short or long fusions appears in increasing percentages years after the operation, depending on the FU period. The results based on only one year follow up is quite insufficient. Is there any case infected in their series? Did they also have other complications? The authors must also mention the difficulties of metal removal, in case of infection. This is a rather titanic endeavor, and the surgeon may have to approach the expandable pillar using an anterior approach, which makes the situation much more complicated. All these limitations must be highlighted in the discussion section of the submission. No case of I-VEP fatigue, anterior or posterior loss of I-VEP, pulmonary embolism, cement extravasation, or infection was reported. However, one patient experienced operation-related complications. One patient (patient 8 in Group I) experienced right-leg weakness soon after the operation. The patient had recovered

completely by the 6-week follow-up. Patient 1 in Group I (an 85-year-old woman), who was treated with short-segment fixation with I-VEP due to VCF of L3, suffered a further collapse at T12 three months after the operation. The anterior vertebral height of T12 reduced from 27.5 mm before the operation to 8.6 mm at 3 months postoperatively; this value remained the same at the 1-year follow-up examination (Fig. 6). However, T12 was not defined as a caudal vertebral fracture is this case. It is also difficult to differentiate a novel instance of VCF from the natural process of aging or a complication related to short-segment fixation with I-VEP. [P. 8-9] Fig. 6 a The lateral view of Patient 1 in Group I shows an L3 vertebral compression fracture and an intact T12 before the operation. b T12 was further collapsed at the three-month follow-up. c The T12 VCF remains at the one-year follow-up. d Anteroposterior view, preoperative radiograph. e Anteroposterior view, three-month follow-up. f Anteroposterior view, one-year follow-up. [P. 23]

The hollow I-VEP, which is packed both inside and out with bone chips for biological augmentation, is used to reconstruct the vertebra through internal mechanical support and also by encouraging bony fusion (Fig. 7). In addition to being enveloped by bone chips, the I-VEP is made of titanium alloy, which is known for its excellent biocompatibility. Just like the anterior expandable strut cage replacement or the expandable cage, the I-VEP can be filled up with bone chips, which expand after settling [19]. However, the I-VEP was implanted through the posterior approach and without corporectomy. Omitting corporectomy could diminish the surgical risk of neurovascular damage and blood loss. Furthermore, preservation of the end plates prevents subsidence of the I-VEP into the adjacent segments. The AH measurements for the adjacent segments were similar in the preoperative evaluation and at the final follow-up. A higher AH below the fracture and smaller KA above the fracture were noted in Group I after operation, which shows that adjacent collapse was less frequent among the patients who underwent short-segment fixation with I-VEP as compared to those treated with KP. [P. 9-10]

One very interesting parameter is the cost-effectiveness issue of the usage of these rather expensive materials. In the 2012 Chicago SRS Pre-Meeting Course it was noted that Third party payors for healthcare may focus on a timeframe that is longer that a single admission, and may include factors in the value equation such as readmission within 90 days, or cost of outpatient care. However patients, physicians, and society consider value over a lifetime. The cost of a single episode of care will be significantly discounted by the duration of the benefit. Patient preference for different health states over time offer the most useful measure of value of healthcare interventions. (See Sigurd Berven. Has the Incorporation of Evidence Based Medicine Over the Past Decade Changed How We Treat Spinal Disease and Deformity? 2012, Pre-Meeting Course, SRS meeting Abstract Book, pages 238-240.) The National Health Insurance program has been implemented in Taiwan since 1995, and covers all medical benefit claims of ambulatory care, offers complete freedom of choice among healthcare providers and covers approximately 98% of the total population of Taiwan. Like all third party payers for healthcare facing the change of the payment system, the Bureau of National Health Insurance is pushing the measures of cost sharing, global budgets, self-management and diagnosis related group system to solve the moral hazard. The main objective is to control health care costs growth, narrow the gap between the income and expenditure, and request the hospitals not to rely on increasing the amount of the patients to maintain their regular operation any more. The data were retrospectively collected at National Taiwan University Hospital and Min-Sheng General Hospital between May 2006 and November 2010. Each patient included was indicated for surgical intervention in the thoracic or lumbar spine region. The indications reported for the patients in this study were intractable back pain due to acute or chronic VCF, pain refractory to nonsurgical treatment for more

than 6 months, or bony cleft formation in the vertebral body. The contraindications were primary or metastatic lesions with vertebral fractures, an infectious origin or poor general condition with a high risk requirement of general anesthesia. [P. 5]

It is therefore better to adjust the results of this study on longer term outcomes; at least after 5 years. (see reference). Then this study will be based on a more permanent and not changing clinical picture. This rush to present the superiority of the combination of short segment fusion with I-VEP vs KP alone based on these short term outcome will offer suboptimal serviced to the issue. Referenced for Adjacent Segment Complications Kim YJ, Bridwell KH, Lenke LG, Glattes CR, Rhim S, Cheh G: Proximal junctional kyphosis in adult spinal deformity after segmental posterior spinal instrumentation and fusion: minimum five-year follow-up. Spine (Phila Pa 1976). 2008 Sep 15;33(20):2179-84. Yagi M, King AB, Boachie-Adjei O: Incidence, Risk Factors and Natural Course of Proximal Junctional Kyphosis: Surgical Outcomes Review of Adult Idiopathic Scoliosis. Minimum 5 years Follow-Up. Spine (Phila Pa 1976). 2012 Feb 21. There were some limitations in our series. First, this study was retrospective and different surgeons performed the two procedures. The current findings, therefore, need to be further validated with larger samples in a multicenter comparative study. Second, our results may not bear comparison with those reported previously. The results of this study were based on a minimum of one year s follow-up. Previous studies have examined patients after at least five years of follow-up. Those studies examined a younger patient population (average age, 45.2 and 48.8 years, respectively) [29, 30] than investigated in this report. Five-year follow-up would have been extremely challenging in our study population. Another point of departure lies in the fact that previous studies examined long segmental fusion in young adult patients with scoliosis, whereas this investigation focused explored short segmental fixation for osteoporotic vertebral fracture in elderly patients. [P. 11-12]

Fig. This was ever an study Intra-Vertebral Expandable Pillar : A Novel Augmenter in the Treatment of Osteoporotic Vertebral Fracture. Jui-Yang Hsieh, Po-Quang Chen presented at the 2011 AAOS Annual Meeting February 15-19th in San Diego, CA. (a presenting poster P365 --- Intra-Vertebral Expandable Pillar for Augmenter in Patients with Osteoporotic Vertebral Fracture ) Abstract: Osteoporotic Vertebral Fracture (OVF) can be managed by various options which have their limitations or biomechanical issues. Intra-Vertebral Expandable Pillar (I-VEP) is a new device to provide long-lasting relief of pain and to reduce kyphosis. Methods: In total 21 patients were enrolled in our study due to single-level osteoporotic thoracolumbar fractures. All patients were divided into two groups according to treatment modalities. The patients in Group I (Fig. 1) underwent additional implantation of pedicle screws and fusion. The patients in Group II underwent I-VEP insertion alone. All patients were evaluated by pre- and postoperative scores for visual analog scale (VAS), anterior vertebral body height (AVBH), and the kyphotic angle (KA) of the lesion site. The AVBH of the adjacent segments were also measured. Results: Totally 40 I-VEPs were inserted with the mean follow-up period of 27.8 months. There was neither neurologic eterioration nor symptomatic implant failure after surgery. In both two groups, the mean VAS pain score was significantly diminished from 8.6 to 1.6 (p<0.001). The mean AVBH was increased from 11.6 mm to 19.4mm (p<0.001). The mean KA was corrected from 19.4 to 6.8 (p<0.001). In contrast, there was no significant difference of the AVBH of the adjacent segments. Conclusions: The collapsed VB could be restored by expanded I-VEP and maintained by effective bony fusion inside and outside of the I-VEP. Also, the preservation of the end plate diminished the risk of subsidence of the I-VEP into the adjacent segments. I-VEP seems reliable and safe in the treatment of patients with symptomatic OVF.

Minor problems The text needs copyediting by an English speaking expert. It is not advisable to be published in the present form. The text has been well copyedited. The Authors contributions must be cited at the proper place at the end of the text Level of interest: An article of limited interest Quality of written English: Needs some language corrections before being published Statistical review: No, the manuscript does not need to be seen by a statistician. Declaration of competing interests: 'I declare that I have no competing interests'