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4. ed

Pedicle Screw Cement Augmentation. a Mechanical Pullout Study on Different Cement Augmentation Techniques

Pedicle screws with polymethyl methacrylate (PMMA) cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques remains unknown. This study aimed to determine the difference in pullout strength between different cement augmentation techniques. Uniform synthetic bones simulating severe osteoporosis were used to provide a platform for each augmentation technique. In all cases a polyaxial screw and acrylic cement (PMMA) at medium viscosity were used. Five groups were analyzed: I) only screw without PMMA (control group); II) retrograde cement pre-filling of the tapped area; III) cannulated and fenestrate screw with cement injection through perforation; IV) injection using a standard trocar of PMMA (vertebroplasty) and retrograde pre-filling of the tapped area; V) injection through a fenestrated trocar and retrograde pre-filling of the tapped area. Standard X-rays were taken in order to visualize cement distribution in each group. Pedicle screws at full insertion were then tested for axial pullout failure using a mechanical testing machine. A total of 30 screws were tested. The results of pullout analysis revealed better results of all groups with respect to the control group. In particular the statistical analysis showed a difference of Group V (p = 0.001) with respect to all other groups. These results confirm that the cement augmentation grants better results in pullout axial forces. Moreover they suggest better load resistance to axial forces when the distribution of the PMMA is along all the screw combining fenestration and pre-filling augmentation technique

Vertebroplasty and kyphoplasty: complementary tecniques for the treatment of painful osteoporotic vertebral compression fractures

OBJECTIVE: in a prospective study, we aimed to evaluate the potential use of kyphoplasty (KP) and vertebroplasty (VP) as complementary techniques in the treatment of painful osteoporotic vertebral compression fractures (VCFs). METHODS: after one month of conservative treatment for VCFs, patients with intractable pain were offered treatment with KP or VP according to a treatment algorithm that considers time from fracture (Ät) and amount of Vertebral Body Collapse (VBC). Bone biopsy was obtained intraoperatively to exclude patients affected by malignancy or osteomalacia. RESULTS: hundred and sixty-four patients were included according to the above criteria. Mean age was 67.6 years. Mean followup was 33 months. Ten patients (6.1%) were lost to follow-up and 154 reached the minimum two years follow-up. 118 (69.5%) underwent VP and 36 (30.5%) underwent KP. Complications affected five patients treated with VP, whose one suffered a transient intercostal neuropathy and four a subsequent VCF (two at adjacent level). Results in terms of VAS and Oswestry scores were not different among treatment groups. CONCLUSION: in conclusion, at an average follow-up of almost 3 years from surgical treatment of osteoporotic VCFs, VP and KP show similar good clinical outcomes and appear to be complementary techniques with specific different indications

Degenerative lumbar spinal stenosis: analysis of results in a series of 374 patients treated with unilateral laminotomy for bilateral microdecompression

OBJECT: Surgical decompression is the recommended treatment in patients with moderate to severe degenerative lumbar spinal stenosis (DLSS) in whom symptoms do not respond to conservative therapy. Multilevel disease, poor patient health, and advanced age are generally considered predictors of a poor outcome after surgery, essentially because of a surgical technique that has always been considered invasive and prone to causing postoperative instability. The authors present a minimally invasive surgical technique performed using a unilateral approach for lumbar decompression. METHODS: A retrospective study was conducted of data obtained in a consecutive series of 473 patients treated with unilateral microdecompression for DLSS over a 5-year period (2000-2004). Clinical outcome was measured using the Prolo Economic and Functional Scale and the visual analog scale (VAS). Radiological follow-up included dynamic x-ray films of the lumbar spine and, in some cases, computed tomography scans. RESULTS: Follow-up was completed in 374 (79.1%) of 473 patients--183 men and 191 women. A total of 520 levels were decompressed: 285 patients (76.2%) presented with single-level stenosis, 86 (22.9%) with two-level stenosis, and three (0.9%) with three-level stenosis. Three hundred twenty-nine patients (87.9%) experienced a clinical benefit, which was defined as neurological improvement in VAS and Prolo Scale scores. Only three patients (0.8%) reported suffering segmental instability at a treated level, but none required surgical stabilization, and all were successfully treated conservatively. CONCLUSIONS: Evaluation of the results indicates that unilateral microdecompression of the lumbar spine offers a significant improvement for patients with DLSS, with a lower rate of complications

Economic study : a cost-effectiveness analysis of an intra-operative compared with a pre-operative image guided system in lumbar pedicle screw fixation in patients with degenerative spondylolisthesis

In spinal surgery, newly developed technology seems to play a key role, especially with the use of computer assisted image-guided navigation, giving excellent results. However, these tools are expensive and may not be affordable for many facilities. PURPOSE: To compare the cost-effectiveness of pre-operative versus intra-operative CT guidance in spinal surgery. STUDY DESIGN: A retrospective economic study. METHODS: A cost-effectiveness study was performed analyzing the overall costs of a population of patients operated on for lumbar degenerative spondylolisthesis, using an image-guided system (IGS) based on a CT scan. The population was divided into two groups, according to the type of CT data set acquisition adopted: Group I (IGS based on a pre-operative spiral CT scan), Group II (IGS based on an intra-operative CT scan - O-ArmTM system). The costs associated with each procedure were assessed through a process analysis: where clinical procedures were broken down into single phases and the related costs from each phase were evaluated. No benefits in any form have been received or will be received from commercial parties directly or indirectly related to the subject of this article. RESULTS: 499 patients met the criteria for this study. In total, 2,542 screws were inserted with IGS. Baseline data were similar for the two groups, as were hospitalization and complications. The surgical time was 119 \ub1 43 minutes in Group I and 92 \ub1 31 minutes in Group II. The full cost of the two procedures were analyzed: the mean cost, using the O-ArmTM system (Group II), was found to be \u20ac 255.83 (3.80%) less than the cost of Group I. Moreover, the O-ArmTM system was also used in other surgical procedures as an intra-operative control, thus reducing the final costs of radiological examinations (a reduction of around 550 CT scans/year). CONCLUSIONS: In conclusion, the authors of the study are of the opinion that the surgical procedure of pedicle screw fixation, using a CT-based computer-guidance system with support of the O-ArmTM system, allows a shortening of procedure time that might improve the clinical result. However, the present study failed to determine a clear cost-effectiveness with respect to other CT-based IGS

Management of C1-2 traumatic fractures using an intraoperative 3D imaging-based navigation system

OBJECT: Fractures of C-1 and C-2 are complex and surgical management may be difficult and challenging due to the anatomical relationship between the vertebrae and neurovascular structures. The aim of this study was to evaluate the role, reliability, and accuracy of cervical fixation using the O-arm intraoperative 3D image-based navigation system. METHODS: The authors evaluated patients who underwent a navigation system-based surgery for stabilization of a fracture of C-1 and/or C-2 from August 2011 to August 2013. All of the fixation screws were intraoperatively checked and their position was graded. RESULTS: The patient population comprised 17 patients whose median age was 47.6 years. The surgical procedures were as follows: anterior dens screw fixation in 2 cases, transarticular fixation of C-1 and C-2 in 1 case, fixation using the Harms technique in 12 cases, and occipitocervical fixation in 2 cases. A total of 67 screws were placed. The control intraoperative CT scan revealed 62 screws (92.6%) correctly placed, 4 (5.9%) with a minor cortical violation (< 2 mm), and only 1 screw (1.5%) that was judged to be incorrectly placed and that was immediately corrected. No vascular injury of the vertebral artery was observed either during exposition or during screw placement. No implant failure was observed. CONCLUSIONS: The use of a navigation system based on an intraoperative CT allows a real-time visualization of the vertebrae, reducing the risks of screw misplacement and consequent complications

Preoperative Magnetic Resonance and Intraoperative Computed Tomography Fusion for Real-Time Neuronavigation in Intramedullary Lesion Surgery

BACKGROUND: Image-guided surgery techniques in spinal surgery are usually based upon fluoroscopy or computed tomography (CT) scan, which allow for a real-time navigation of bony structures, though not of neural structures and soft tissue remains. OBJECTIVE: To verify the effectiveness and efficacy of a novel technique of imaging merging between preoperative magnetic resonance imaging (MRI) and intraoperative CT scan during removal of intramedullary lesions. METHODS: Ten consecutive patients were treated for intramedullary lesions using a navigation system aid. Preoperative contrast-enhanced MRI was merged in the navigation software, with an intraoperative CT acquisition, performed using the O-arm TM system (Medtronic Sofamor Danek, Minneapolis, Minnesota). Dosimetric and timing data were also acquired for each patient. RESULTS: The fusion process was achieved in all cases and was uneventful. The merged imaging information was useful in all cases for defining the exact area of laminectomy, dural opening, and the eventual extension of cordotomy, without requiring exposition corrections. The radiation dose for the patients was 0.78 mSv. Using the authors' protocol, it was possible to merge a preoperative MRI with navigation based on intraoperative CT scanning in all cases. Information gained with this technique was useful during the different surgical steps. However, there were some drawbacks, such as the merging process, which still remains partially manual. CONCLUSION: In this initial experience, MRI and CT merging and its feasibility were tested, and we appreciated its safety, precision, and ease