A novel classification of cement distribution patterns based on plain radiographs associated with cement filling rate and relevance to the clinical results of unipedicle vertebroplasty.

INTRODUCTION: Cement distribution pattern following unipedicle percutaneous vertebroplasty (UVP) for osteoporotic vertebral compression fractures (OVCFs) has been reported in association with clinical results. The present retrospective study aimed to classify the bone cement distribution types following UVP and investigate the differences in clinical efficacy and related complications. MATERIALS AND METHODS: We retrospectively reviewed the medical records of the patients with single-segment OVCFs who underwent UVP. Cement distribution patterns were divided into the diffuse, block, double band, and single band types according to the plain radiographs and further by cement filling rate (CFR) based on a three-dimension reconstruction of post-operative CT. The cutoff values of CFR were > 34% for the diffuse, block between 34 and 20%, and each band of the double or single band < 20%. Clinical efficacy and related complications were compared among the four cement distribution types 24 h after the operation and the last follow-up. RESULTS: A total of 155 patients with an average follow-up time of 20.3 months were included. The diffuse type included 26 patients; block, 87; double band, 18; and single band, 24. The VAS and ODI after operation improved significantly in all four groups. The diffuse and block types had similar clinical results. The clinical outcomes in the single band group were the poorest at the last follow-up. The patients with single band type also had the highest rates of body re-collapse and revision surgery for the index level. CONCLUSION: Diffuse and block groups can better maintain the height of the vertebral body and reduce the risk of vertebral body recompression. The single band has the poorest results, and intraoperative immediate contralateral vertebroplasty was highly recommended.

Subpedicle decompression and vertebral reconstruction for thoracolumbar Magerl incomplete burst fractures via a minimally invasive method.

STUDY DESIGN: Retrospective. OBJECTIVE: To evaluate the clinical and radiographical results. SUMMARY OF BACKGROUND DATA: The evolution of posterior approach for burst fractures was from long-segment to short-segment and then to monosegmental fixation. Decompression of the spinal cord is performed by anterior or posterior approaches. The technique attempts to decompress the spinal cord by a paramedian subpedicle approach, and simultaneous vertebral reconstruction with pile-up titanium spacers (subpedicle decompression and body augmentation [SpBA]) was developed. METHODS: Eighty patients with symptomatic single thoracolumbar Magerl incomplete burst fractures were included. After manual reduction, transpedicle body augmentation and shortsegment fixation (TpBA group) were performed in 38 patients and SpBA in 42 cases. The mean follow-up was 52.6 ± 18.7 (TpBA) and 42.1 ± 7.8 (SpBA) months, and the age was 57.9 ± 7.2 and 59.1 ± 8.3 years. Clinical and radiographical outcomes were analyzed. RESULTS: The operation time was 66 ± 11 (TpBA) versus 34.5 ± 5.5 (SpBA) minutes. The initial anterior vertebral correction was 46.8 ± 12.2% (TpBA) versus 53.2 ± 15.0% (SpBA) (P = 0.03) and the final correction was 44.0 ± 10.8% versus 51.5 ± 15.3% (P = 0.01). Initial corrections of the lateral Cobb angle were 22.3° ± 2.6° versus 22.8° ± 2.7° and the final corrections were 19.1° ± 3.4° versus 20.5° ± 2.9°. The VAS score was 7.7 ± 1.2 versus 7.9 ± 1.2 preoperatively and 2.2 ± 0.7 versus 1.8 ± 0.6 (P = 0.02) at the final visit. Seventy-five patients maintained or recovered to Frankel grade E. Three patients in the TpBA group and 2 in the SpBA group improved from grade C to D. Technical complications included 1 root overstretch in the SpBA group and one incomplete decompression in the TpBA group. CONCLUSION: SpBA is a safe and fast technique to treat Magerl incomplete burst fractures and leads to good clinical results. LEVEL OF EVIDENCE: N/A.

Transpedicle body augmenter for vertebral augmentation in symptomatic multiple osteoporotic compression fractures.

BACKGROUND: Multiple osteoporotic vertebral compression fractures (VCFs) have been treated with polymethylmethacrylate augmentation; however, there are cement complications and long-term fracture healing that are unknown. Transpedicle body augmenter (a porous titanium spacer) has been reported as an internal support to reconstruct the vertebral body combining short-segment fixation in burst fracture and Kümmell's disease with cord compression. Transpedicle body augmenter for vertebral augmentation (TpBA) also has been reported successfully in treating single painful VCF and vertebral metastasis lesions including pending fractures and pathologic compression fractures. To test the hypothesis that TpBA can effectively and safely treat the symptomatic multiple VCFs, this retrospective study was done by analyzing the radiographic and clinical results. MATERIALS AND METHODS: We retrospectively reviewed clinical and radiographic results of TpBA for symptomatic multiple (more than two levels) VCFs in 62 patients with a total of 236 levels, i.e. 3.8 VCFs per patient. Manual reduction and TpBA via paramedian incisions with blunt dissection were done. One incision was made for two continuous levels and alternative side was selected for next incision. Mean age was 74.3 years (range, 62-87 years), and female-male ratio was 5.2:1. Anterior vertebral height and wedge angle by radiographic findings were measured at preoperative, initial follow-up and final follow-up. Clinical results were assessed by questionnaires and clinical observations. By July 2008, 58 patients returned to answer the questionnaire including quantification of pain on the visual analog scale, the response to operations (better, same, or worse after operation), returned to their pre-fracture function (yes/no) and satisfaction (a scale of 0 = completely dissatisfied to 10 = completely satisfied). RESULTS: The mean symptom duration was 7 months, and follow-up, 48 months. The average operation time was 21 min per level, blood loss was 74 cc per level and hospitalization was 4.4 days. No patient had neurological deterioration. There was no dislodgement of implant in the final visit. Forty-eight patients (77.4%) could walk within 6-8 h after operation and the others, within 24 h. The anterior vertebral restoration was 7.3 mm initially and 6.2 mm at final follow-up. Wedge angle correction was 10.4 degrees initially and was 9.3 degrees at final follow-up. Pain, by the visual analog scale, was 8.5 preoperatively, 2.7 at day 7 follow-up and 2.9 at final follow-up. By the questionnaire, 52 of 58 respondents reported a decrease in discomfort after TpBA and 48 of 58 patients reported a return to normal activity after operation. The final satisfaction rate was 89.7%. DISCUSSION: The symptoms of multiple osteoporotic compression fracture may be due to unstable fracture, radiculopathy, and global traumatic kyphosis with posture changes, which can be corrected by multiple TpBA. The transpedicle body augmenter was initially stabilized by the sinking and locking mechanism and finally by bone ingrowth. CONCLUSIONS: TpBA via a minimally invasive method led to early and medium-term clinical improvements and anatomic restoration of multiple symptomatic VCFs.

Long-term results of transpedicle body augmenter in treating burst fractures.

BACKGROUND: Short-segment fixation alone to treat thoracolumbar burst fractures is common but it has a 20-50% incidence of implant failure and rekyphosis. A transpedicle body augmenter (TpBA) to reinforce the vertebral body via posterior approach has been reported to prevent implant failure and increase the clinical success rate in treating burst fracture. This article is to evaluate the longterm results of short-segment fixation with TpBA for treatment of thoracolumbar burst fractures. MATERIALS AND METHODS: Patients included in the study had a single-level burst fracture involving T11-L2 and no distraction or rotation element with limited neurological deficit. Patients in the control group (n = 42) were treated with short-segment posterior instrumentation alone, whereas patients in the augmented group (n = 90) were treated with a titanium spacer designed for transpedicle body reconstruction. The followup was 48-101 months. The radiographic and clinical results were evaluated and compared by Student's t test and Fisher's exact test. RESULTS: The blood loss, operation time and hospitalization were similar in both the groups. The immediate postoperative anterior vertebral restoration rate of the augmented group was similar to that of the control group (97.6% ± 2.4% vs. 96.6% ± 3.2%). The final anterior vertebral restoration was greater in the augmented group than in the control group (93.3% ± 3.4% vs. 62.5% ± 11.2%). Immediate postoperative kyphotic angles were not significantly different between the groups (3.0° ± 1.8° vs. 5.1° ± 2.3°). The final kyphotic angles were less in the augmented group than the control group (7.3° ± 3.5° vs. 20.1° ± 5.4°). The augmented group had less (P < 0.001) implant failure [0% (n=0) vs. 23.8% (n=10)] for the control group) and more patients (P < 0.001) with no pain or minimal or occasional pain (Grade P1 or P2) than the control group [90.0% (n=81) vs. 66.7% (n=28)]. All patients in the augmented group and 39 (92.8%) patients in the control group experienced neurological recovery to Frankel Grade E. Three patients in the control group had improvement to Frankel Grade D from Frankel Grade C, but later had deterioration to Frankel Grade C because of loosening and dislodgement of the implant. CONCLUSION: Posterior body reconstruction with TpBA can maintain kyphosis correction and vertebral restoration, prevent implant failure and lead to better clinical results.

Transpedicle body augmenter in painful osteoporotic compression fractures.

Osteoporotic compression fractures (VCFs) can result in progressive kyphosis and chronic pain. Polymethylmethacrylate has been used for augmentation of VCFs; however, there are cement complications, and long-term fracture healing is unknown. The transpedicle body augmenter (TpBA), a porous titanium spacer, has been reported as an internal support to reconstruct the vertebral body combining short segment fixation in burst fracture. We retrospectively reviewed radiographic and clinical results of TpBA vertebroplasty for single symptomatic VCF in 80 patients. Manual reduction and TpBA vertebroplasty via a paramedian incision with blunt dissection was done. Mean age was 72.3 years (range 51-87 years), and female-male ratio was 66:14. The mean symptom duration was 5 months, and follow-up 44 months. Peri-operative variables and radiographic and clinical results were evaluated. The average operation time was 26.1 min, blood loss 92 cc, and hospitalization 2.3 days. No patient had neurological deterioration. TpBA was found sinking into vertebral body initially, then locked by residual cortex, and finally stabilized within the vertebra. There was no dislodgement of TpBA in the final visit. Sixty-two patients (77.5%) could walk within 3-6 h after operation and the others within 24 h. The anterior vertebral restoration was 8.0 mm initially and 6.1 mm at final follow-up. Wedge angle correction was 11.5 degrees initially and 9.4 degrees at final follow-up. Pain, by the visual analog scale, was 8.6 pre-operatively, 2.5 at day 7 follow-up, and 2.9 at final follow-up. By the questionnaire, 72 of 76 respondents reported a decrease in discomfort after TpBA vertebroplasty, and 63 of 76 patients reported a return to normal activity after operation. The final satisfaction rate was 93.4%. TpBA vertebroplasty led to early and medium-term clinical improvement and anatomic restoration of painful VCFs.

Another option to treat Kümmell's disease with cord compression.

The efficiency of short-segment fixation with transpedicle body augmenter (a titanium spacer with bone-ingrowth porous surface, TpBA) to treat Kümmell's disease with cord compression (stage III) was retrospectively evaluated. No laminectomy or instrumentation reduction was done. Inclusion criteria included Frankel CDE, single-level within T10-L2. FU rate was 88%, i.e. 21 cases were included. Frankel function classification was 6E9D6C. Mean age was 72+/-8 years. F:M was 16:5. FU period was 48 M (range, 30-76 M). The hospitalization was 4.5+/-2.2 days; operation time, 70.4+/-17.2 min; blood loss, 150+/-72 cc. Final Frankel class was 20E1D. Complications included two superficial infection and one pneumonia. Body height and kyphosis were all corrected significantly and well preserved at the final visit. No TpBA dislodgement or implant failure was noted; however, three cases developed new compression fractures. The clinical outcome showed 81% with P1 or P2 by Denis pain scale. This method can decompress spinal canal, maintain kyphosis correction and vertebral restoration, prevent implant failure, and attain good clinical results.

Preliminary report of transpedicle body augmenter vertebroplasty in painful vertebral tumors.

STUDY DESIGN: Transpedicle body augmenter vertebroplasty of painful vertebral tumor was retrospectively evaluated. OBJECTIVE: Transpedicle body augmenter vertebroplasty was designed to treat spinal tumor with intractable pain refractory to conservative management, deformity, biomechanical impairment, and neural deficits. SUMMARY OF BACKGROUND DATA: Chemotherapy, hormonal therapy, and radiation therapy cannot restore spinal stability. Complication rates of major surgery are high. Percutaneous vertebroplasty has a high leakage rate, and tumor tissue may be displaced into the canal. Transpedicle body augmenter vertebroplasty was designed to treat spinal tumor for pain control and stability. METHODS: There were 9 women and 9 men with a mean age of 62.7 +/- 12.6 years included. All patients had vertebral pain. Walking was impossible for 12 patients, and 15 had neurologic deficits. Treatments included manual reduction and transpedicle body augmenter vertebroplasty. RESULTS: Mean follow-up time was 18 months. Mean hospitalization was 7.1 +/- 4.2 days, operating time was 46 +/- 25 minutes, and blood loss was 263 +/- 157 cc. Neither neurologic deterioration nor root irritation was found after transpedicle body augmenter vertebroplasty. No dislodgement of the transpedicle body augmenter was found at the final visit. According to the visual analog scale, pain was 9.3 before surgery, 3.2 at 2-week follow-up, and 2.2 at 3-month follow-up. There were 11 patients (92%) who recovered walking ability. Neurologic status improved in 14 patients (93%). The satisfaction rate was 89%. CONCLUSION: Transpedicle body augmenter vertebroplasty proved to be safe and effective in reducing pain and improving functional status of patients with spinal tumor.

Biomechanical analysis of unilateral fixation with interbody cages.

STUDY DESIGN: An in vitro biomechanical study of the stabilizing effects of a different combination of cages and transpedicular instrumentation on experimental degenerative disc disease. OBJECTIVES: To evaluate the biomechanical efficacy of the interbody fusion cage and unilateral posterior instrumentation on the stability of the spine-device construct. SUMMARY OF BACKGROUND DATA: Posterior lumbar interbody fusion (PLIF) has become a clinically established and increasingly popular procedure since its introduction and subsequent modification. Recently, unilateral fixation was reported to have comparable efficacy to bilateral fixation in two- to three-segment posterior instrumentation. This study has been designed to compare biomechanical properties among various spinal fixations, including bilateral versus unilateral fixation with PLIF and cages. METHODS: Thirty porcine L3-L6 spines were separated into six groups. The utilization of one or two cages and unilateral or bilateral instrumentations were reciprocally combined to stabilize the spine with the L4-L5 discectomy, simulating degenerative disc disease. A serial of biomechanical tests, including flexion (5 N-m), extension (5 N-m), compression (250 N), lateral bending (5 N-m), and axial rotation (5 N-m, 25 mm/min), were conducted at the displacement rate of 25 mm/min in five cycles. Stiffness values were derived from loading curves for comparison of spinal stability. RESULTS.: In axial compression, the stiffness of bilateral fixation (BF) and unilateral fixation with two-cage (UF2C) groups were almost identical and only less than that of the bilateral fixation with two cages (BF2C) group. In the flexion, the BF, UF2C, and unilateral fixation with one cage (UF1C) group incurred comparable stiffness to that of the Intact group. In extension, the UF2C group had a comparable stiffness to the BF2C group. In lateral bending, the BF2C group and the UF2C group were the constructs incurring most stiffness. In torsion, the BF group and the UF2C group were less stiff than the BF2C group, but that was statistically insignificant CONCLUSIONS: In the group of unilateral fixation combining PLIF with two cages, the anterior support of cages enabled unilateral instrumentation to restore torsional stiffness and other spinal stability indexes. Considering the initial stability and the load-sharing effect, this study showed that the unilateral fixation combining PLIF and two cages might be a good alternative to spinal fixation.

Transpedicle body augmenter: a further step in treating burst fractures.

UNLABELLED: The efficiency of short-segment fixation with a transpedicle body augmenter for treatment of thoracolumbar burst fractures was retrospectively evaluated. Patients included in the study had limited neurologic function, a single-level burst fracture involving T11-L2, and no distraction or rotation trauma. Patients in the control group (n = 45) were treated with short-segment posterior instrumentation alone, whereas patients in the augmented group (n = 75) were treated with a titanium block designed for transpedicle body reconstruction. The followup was 24-70 months. The operation time and blood loss were similar in both groups. The immediate postoperative anterior vertebral restoration rate of the augmented group was similar to that of the control group (96.8% +/- 2.1% versus 96.7% +/- 3.0%). The final anterior vertebral restoration was greater in the augmented group than in the control group (93.7% +/- 3.0% versus 66.3% +/- 10.5%). Immediate postoperative kyphotic angles were not significantly different between the groups (3.2 degrees +/- 1.5 degrees versus 5.5 degrees +/- 2.0 degrees). The final kyphotic angles were less in the augmented group than the control group (6.7 degrees +/- 3.0 degrees versus 19.6 degrees +/- 5.1 degrees). The control group had more implant failures than the augmented group. The augmented group had better results according to the Denis pain scale. Posterior body reconstruction with a transpedicle body augmenter can maintain kyphosis correction and vertebral restoration, prevent implant failure, and lead to better clinical results. LEVEL OF EVIDENCE: Therapeutic study, Level III-2 (retrospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

Biomechanical effects of the body augmenter for reconstruction of the vertebral body.

STUDY DESIGN: An in vitro biomechanical study of the stabilizing effects of the body augmenter and posterior instrumentation on experimental thoracolumbar fractures with vertebral defects. OBJECTIVE: To evaluate the effects of the body augmenter and instrumentation on the stability of the spine-device construct. SUMMARY OF BACKGROUND DATA: Posterior instrumentations alone are widely used to accomplish spinal reduction and provide stability for an injured spine; however, implant failure rates have been reported to be approximately 20%. Transpedicular discectomy and bone graft has reported only 33% fusion rates. Combined anterior bony strut and posterior instrumentation was a challenge to geriatric patients with vulnerable medical conditions and possible vascular and pulmonary complications. Therefore, a new design, the body augmenter, tries to reconstruct the vertebral body through internal mechanical support and also encourage bony fusion. This study is to evaluate its initial mechanical effects. METHODS: Twenty fresh porcine T11-L3 vertebrae were harvested. The L1 vertebra with one third or one half corpectomy was performed to simulate a fracture injury with vertebral defects. Posterior instrumentation alone (PI group), posterior instrumentation with body augmenters (BA group), and anterior instrumentation with tricortical bony strut and DCP 1 level above and 1 level below the fracture site (DCP group) were applied as treatment strategies. Load-displacement and torque-angle plots were generated and used to calculate axial stiffness and torsional rigidity for these constructs with vertebral fracture at the L1 vertebrae. Axial compression, extension, and flexion tests were performed at intact and spine-device constructs to document spinal stability. RESULTS: The construct stability had a complex association to the device applied. In the one third corpectomy group, the BA group had significantly higher compression stiffness than the PI group. In the one half corpectomy group, the flexion and compression stiffness of the BA group became significantly greater than the PI group, and the extension stiffness is significantly higher than the DCP group. CONCLUSIONS: The body augmenters combined with posterior instrumentation increased the spinal construct stability during compression, flexion, and extension. According to results in this study, the body augmenter could provide a better initial stability of construct and prevent the implant failure of posterior instrumentation and may be a feasible substitute for the anterior role in the future.