Risk factors of neurological deficit and pulmonary cement embolism after percutaneous vertebroplasty.

BACKGROUND: The risk factors, incidence, and clinical management of pulmonary cement embolism and neurological deficit during percutaneous vertebroplasty (PVP) were evaluated. METHODS: Three thousand one hundred and seventy-five patients with symptomatic osteoporotic vertebral compression fractures (OVCFs) treated with PVP were retrospectively reviewed in a single institution. Clinical parameters such as age, gender, number of fractures, and time from fracture to vertebroplasty were recorded at the time of surgery. Image and surgical parameters including the amount of cement, the vertebral level, uni- or bipedicle surgical approach, and leakage pattern were recorded. RESULTS: Type-C leakage, including paraspinal (25%), intradiscal (26%), and posterior (0.7%) leakage, was more common than type-B (11.4%) and type-S leaks (4.9%). Cement leakage into the spinal canal (type-C posterior) occurred in 26 patients (0.7%), and four patients needed surgical decompression. Three in nine patients with leakage into thoracic spine needed decompressive surgery, but only one of 17 patients into lumbar spine needed surgery (p < 0.01). Age, gender, number of fractures, and time from fracture to vertebroplasty were not risk factors of pulmonary cement embolism or neurological deficit. The risk factor of pulmonary cement embolism was higher volume of PMMA injected (p < 0.001) and risk factor of neurological deficit was type-C posterior cement leakage into thoracic spine. The incidence of pulmonary cement embolism was significantly high in the volume of PMMA injected (PMMA injection < 3.5 cc: 0%; 3.5-7.0 cc: 0.11%; > 7.0 cc: 0.9%; p < 0.01) which needed postoperative oxygen support. CONCLUSIONS: Cement leakage is relatively common but mostly of no clinical significance. Percutaneous vertebroplasty in thoracic spine and high amount of PMMA injected should be treated with caution in clinical practice.

Compensating additional optical power in the central zone of a multifocal contact lens forminimization of the shrinkage error of the shell mold in the injection molding process.

This study aims to develop a compensating method to minimize the shrinkage error of the shell mold (SM) in the injection molding (IM) process to obtain uniform optical power in the central optical zone of soft axial symmetric multifocal contact lenses (CL). The Z-shrinkage error along the Z axis or axial axis of the anterior SM corresponding to the anterior surface of a dry contact lens in the IM process can be minimized by optimizing IM process parameters and then by compensating for additional (Add) powers in the central zone of the original lens design. First, the shrinkage error is minimized by optimizing three levels of four IM parameters, including mold temperature, injection velocity, packing pressure, and cooling time in 18 IM simulations based on an orthogonal array L18 (21×34). Then, based on the Z-shrinkage error from IM simulation, three new contact lens designs are obtained by increasing the Add power in the central zone of the original multifocal CL design to compensate for the optical power errors. Results obtained from IM process simulations and the optical simulations show that the new CL design with 0.1 D increasing in Add power has the closest shrinkage profile to the original anterior SM profile with percentage of reduction in absolute Z-shrinkage error of 55% and more uniform power in the central zone than in the other two cases. Moreover, actual experiments of IM of SM for casting soft multifocal CLs have been performed. The final product of wet CLs has been completed for the original design and the new design. Results of the optical performance have verified the improvement of the compensated design of CLs. The feasibility of this compensating method has been proven based on the measurement results of the produced soft multifocal CLs of the new design. Results of this study can be further applied to predict or compensate for the total optical power errors of the soft multifocal CLs.

Optical design of soft multifocal contact lens with uniform optical power in center-distance zone with optimized NURBS.

This study aims to develop a new optical design method of soft multifocal contact lens (CLs) to obtain uniform optical power in large center-distance zone with optimized Non-Uniform Rational B-spline (NURBS). For the anterior surface profiles of CLs, the NURBS design curves are optimized to match given optical power distributions. Then, the NURBS in the center-distance zones are fitted in the corresponding spherical/aspheric curves for both data points and their centers of curvature to achieve the uniform power. Four cases of soft CLs have been manufactured by casting in shell molds by injection molding and then measured to verify the design specifications. Results of power profiles of these CLs are concord with the given clinical requirements of uniform powers in larger center-distance zone. The developed optical design method has been verified for multifocal CLs design and can be further applied for production of soft multifocal CLs.

Is additional balloon Kyphoplasty safe and effective for acute thoracolumbar burst fracture?

BACKGROUND: Burst fracture is a common thoracolumbar injury that is treated using posterior pedicle instrumentation and fusion combined with transpedicular intracorporeal grafting after reduction. In this study, we compared the outcome of these two techniques by using radiologic imaging and functional outcome. METHODS: Sixty-one patients with acute thoracolumbar burst fracture were operated with kyphoplasty (n = 31) or vertebroplasty (n = 30) and retrospectively reviewed in our institution between 2011 and 2014. All 61 patients underwent surgery within 5 days after admission to the hospital and then followed-up for 12 to 24 months after surgery. RESULTS: Significant improvement was found in the anterior vertebral height (92 ± 8.9% in the kyphoplasty group, 85.6 ± 7.2% in the vertebroplasty group, p < 0.01) at 1 month post-operatively and (89 ± 7.9% in the kyphoplasty group, 78 ± 6.9% in the vertebroplasty group, p < 0.01) at the 24-month follow-up. Significant improvement was also observed in the kyphotic angle (1.2 ± 0.5° in the kyphoplasty group, 10.5 ± 1.2° in the vertebroplasty group, p < 0.01) at 1 month post-operatively and (5.4 ± 1.2° in the kyphoplasty group, 11.5 ± 8.5° in the vertebroplasty group, p < 0.01) at the 24-month follow-up. Both operations led to significant improvement of the patients' pain and the Oswestry disability index (p < 0.01). Cement leakage was noted in 29% of patients after kyphoplasty and 77% of patients after vertebroplasty (p < 0.01). Only one implant failure (3.3%), which required further surgical intervention, was reported in the vertebroplasty group. CONCLUSIONS: Reduction with additional balloon at the fractured site is better than indirect reduction only by posterior instrumentation. The better reduction of kyphotic angle and the lower cement leakage rate in the kyphoplasty group indicate that additional balloon kyphoplasty is safe and effective for acute thoracolumbar burst fracture.

Additional vertebral augmentation with posterior instrumentation for unstable thoracolumbar burst fractures.

BACKGROUND: To investigate the role of vertebral augmentation in kyphosis reduction, vertebral fracture union, and correction loss after surgical management of thoracolumbar burst fracture. DESIGN: Retrospective chart and radiographic review. SETTING: Level 1 trauma center. METHODS: The analysis included patients treated between April 2007 and June 2015, who received pedicle-screw-rod distraction and reduction within two days following acute traumatic thoracolumbar burst fracture with a load sharing score >6. Medical records were retrospectively reviewed for data regarding operative details, imaging and laboratory findings, neurological function, and functional outcomes. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Sagittal index, pain score, loss of correction, and implant failure rate. RESULTS: Nineteen patients were enrolled in this study (mean age, 37.2±13years; age range, 17-62 years; female/male ratio: 10/9). Of the five patients who received only reduction (no augmentation), one underwent revision surgery because of implant failure and pedicle screw backing out. Compared to patients who received only reduction, those who received both reduction and augmentation showed better sagittal alignment after the operation, with better sagittal index immediately postoperatively and during the follow-up (p<0.05). CONCLUSIONS: Transpedicular vertebral augmentation with calcium sulfate/phosphate-based bone cement may reinforce thoracolumbar burst fracture stability, partially restore vertebral body height, and reduce pedicle screw bending and movement, thereby preventing early implant failure and late loss of correction, especially in patients with excellent fracture reduction. LEVEL OF EVIDENCE: Therapeutic level III, retrospective chart review.

Percutaneous balloon kyphoplasty for the treatment of vertebral compression fractures.

BACKGROUND: Vertebral compression fractures (VCFs) constitute a major health care problem, not only because of their high incidence but also because of their direct and indirect negative impacts on both patients' health-related quality of life and costs to the health care system. Two minimally invasive surgical approaches were developed for the management of symptomatic VCFs: balloon kyphoplasty and vertebroplasty. The purpose of this study was to evaluate the effectiveness and safety of balloon kyphoplasty in the treatment of symptomatic VCFs. METHODS: Between July 2011 and June 2012, one hundred and eighty-seven patients with two hundred and fifty-one vertebras received balloon kyphoplasty in our hospital. There were sixty-five male and one hundred and twenty-two female patients with an average age of 74.5 (range, 61 to 95 years). The pain symptoms and quality of life, were measured before operation and at one day, three months, six months and one year following kyphoplasty. Radiographic data including restoration of kyphotic angle, anterior vertebral height, and any leakage of cement were defined. RESULTS: The mean visual analog pain scale decreased from a preoperative value of 7.7 to 2.2 at one day (p < .05) following operation and the Oswestry Disability Index improved from 56.8 to 18.3 (p < .05). The kyphotic angle improved from a mean of 14.4° before surgery to 6.7° at one day after surgery (p < .05). The mean anterior vertebral height increased significantly from 52% before surgery to 74.5% at one day after surgery (p < .05) and 70.2% at one year follow-up. Minor cement extravasations were observed in twenty-nine out of two hundred and fifty-one procedures, including six leakage via basivertebral vein, three leakage via segmental vein and twenty leakage through a cortical defect. None of the leakages were associated with any clinical consequences. CONCLUSIONS: Balloon kyphoplasty not only rapidly reduced pain and disability but also restored sagittal alignment in our patients at one-year follow-up. The treatment of osteoporotic vertebral compression fractures with balloon kyphoplasty is a safe, effective, and minimally invasive procedure that provides satisfactory clinical results.

Aseptic nonunion of a femoral shaft treated using exchange nailing.

BACKGROUND: There are many methods for treating femoral shaft aseptic nonunions of which exchange nailing is the simplest technique. However, the reported success rate varies. Therefore, a prospective study was conducted to further clarify the role of exchange nailing. METHODS: From October 1994 through December 1999, 40 femoral shaft aseptic nonunions in 39 patients were treated using exchange nailing. The indications for this technique included a femoral shaft aseptic nonunion with a previously inserted intramedullary nail, less than 1 cm shortening, a radiolucent line of the nonunion, and no segmental bony defects. The surgical technique consisted of close removal of the previously inserted intramedullary nail, reaming the intramedullary canal as widely as possible (1 or 2 mm oversized), and re-insertion of a stable unlocked or locked intramedullary nail. RESULTS: Thirty-six femoral shaft aseptic nonunions in 35 patients were followed-up for at least 1 year (median, 2.9 years; range, 1.1-6.0 years) and 33 nonunions healed. The union rate was 91.7% (33/36) and the union period was median 4 months (range, 3-8 months). No major surgical complications were noted. The other three patients with persistent nonunions were continuously followed-up due to their reluctance for further operations. CONCLUSION: Although exchange nailing is a relatively simple surgical technique, it can still achieve a high union rate with a low complication rate. Despite that factors to induce a persistent nonunion are still unclear, clinically, exchange nailing should be used as the first choice in the treatment of an indicated femoral shaft aseptic nonunion.