Skull-fixated fiducial markers improve accuracy in staged frameless stereotactic epilepsy surgery in children.
ABSTRACT Surgery to monitor and resect epileptogenic foci may be undertaken in 2 stages, providing an opportunity to use skull-fixated fiducials implanted during the first stage to improve the accuracy of cortical resection during the second stage. This study compared the intrinsic accuracy of skin-based and skull-fixated fiducial markers in registering frameless stereotaxy during pediatric epilepsy surgery. To the authors' knowledge, these modalities of registration have not previously been directly compared in this population.
The authors undertook a retrospective review of pediatric patients who underwent resection of epileptogenic foci in 2 stages with frameless stereotactic assistance, performed by a single surgeon at Oregon Health & Science University. For the first stage (subdural grid implantation), 9 skin fiducial markers were used to register anatomical data in a frameless stereotactic station. Intraoperatively, four 3-mm screws were placed circumferentially around the craniotomy. Postoperatively, thin-slice brain MR and CT images were obtained and fused. For the second stage, the 4 screws were used as fiducial markers to register the stereotactic anatomical data. For both stages, accuracy (difference in millimeters from zero of the manual fiducial registration compared with the computer model) was determined using navigation software. The intrinsic accuracy of these 2 methods of fiducial registration was compared using a paired Student t-test.
Between 2004 and 2009, 40 pediatric patients with epilepsy underwent frameless stereotactic surgical procedures. Fourteen patients who had 2-stage procedures using skin-based and skull-fixated registration with complete accuracy data were included in this retrospective review. Mean registration error was significantly lower using skull-fixated fiducials (1.35 mm, 95% CI 1.09-1.60 mm) than using skin-based fiducials (1.85 mm, 95% CI 1.56-2.13 mm; p = 0.0016).
A significantly higher degree of accuracy was achieved using 4 skull-fixated fiducials compared with using 9 skin-based fiducials. This simple and accurate method for registering frameless stereotactic anatomical data does not involve the potential time, expense, discomfort, and morbidity of extraoperative skull-fixated fiducial placement. The method described in this paper could also be extrapolated to other planned 2-stage cranial surgical procedures such as combined skull base approaches.
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ABSTRACT: Object Pelvic fixation is a crucial adjunct to many lumbar fusions to avoid L5-S1 pseudarthrosis. It is useful for treatment of kyphoscoliosis, high-grade spondylolisthesis, L5-S1 pseudarthrosis, sacral tumors, lumbosacral dislocations, and osteomyelitis. The most popular method, iliac fixation, has drawbacks including hardware prominence, extensive muscle dissection, and the need for connection devices. S-2 alar iliac fixation provides a useful primary or salvage alternative. The authors describe their techniques for using stereotactic navigation for screw placement. Methods The O-arm Surgical Imaging System allowed for CT-quality multiplanar reconstructions of the pelvis, and registration to a StealthStation Treon provided intraoperative guidance. The authors describe their technique for performing computer-assisted S-2 alar iliac fixation for various indications in 18 patients during an 18-month period. Results All patients underwent successful bilateral placement of screws 80-100 mm in length. All placements were confirmed with a second multiplanar reconstruction. One screw was moved because of apparent anterior breach of the ilium. There were no immediate neurological or vascular complications due to screw placement. The screw length required additional instruments including a longer pedicle finder and tap. Conclusions Stereotactic guidance to navigate the placement of distal pelvic fixation with bilateral S-2 alar iliac fixation can be safely performed in patients with a variety of pathological conditions. Crossing the sacroiliac joint, choosing trajectory, and ensuring adequate screw length can all be enhanced with 3D image guidance. Long-term outcome studies are underway, specifically evaluating the sacroiliac joint.Journal of neurosurgery. Spine 03/2013; · 1.61 Impact Factor
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ABSTRACT: BACKGROUND:: Neuronavigation has become an intrinsic part of preoperative surgical planning and surgical procedures. However, many surgeons have the impression that accuracy decreases during surgery. OBJECTIVE:: To quantify the decrease of neuronavigation accuracy and identify possible origins, we performed a retrospective quality-control study. METHODS:: Between April and July 2011, a neuronavigation system was used in conjunction with a specially prepared headholder in 55 consecutive patients. Two different neuronavigation systems were investigated separately. Co-registration was performed with laser-surface matching, paired-point matching using skin fiducials, anatomical landmarks, or bone-screws. The initial target registration error (TRE1) was measured using the nasion as the anatomical landmark. Then, after draping and during surgery, the accuracy was checked at predefined procedural landmark steps (MMP=Mayfield measurement point and BMP=bone measurement point), and deviations were recorded. RESULTS:: After initial co-registration, the mean TRE1 was 2.9mm (standard deviation [SD] 3.3). TRE1 was significantly dependent on patient positioning, lesion localization, type of neuroimaging, and co-registration method. The following procedures decreased neuronavigation accuracy: attachment of surgical drapes (□TRE2=2.7mm, SD 1.7), skin-retractor attachment (□TRE3=1.2mm, SD 1.0), craniotomy (□TRE3=1.0mm, SD 1.4), and Halo-ring installation (□TRE3=0.5mm, SD 0.5). Surgery duration was a significant factor too: overall □TRE was 1.3mm (SD 1.5) after 30 minutes and increased up to 4.4mm (SD 1.8) after 5.5 hours of surgery. CONCLUSION:: After registration there is an ongoing loss of neuronavigation accuracy. Major factors were draping, attachment of skin-retractors, and duration of surgery. Surgeons should be aware of this silent loss of accuracy when using neuronavigation.Neurosurgery 01/2013; · 2.53 Impact Factor
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ABSTRACT: Brain biopsies (BB) and depth electrode placements (DEP) are increasingly performed using frameless stereotactic targeting devices. This paper is intended to provide a comprehensive review of the technical features, targeting errors and clinical results. A PubMed literature search from 1995-2010 was performed. (A) Modified stereotactic arcs, (B) arm-based devices with and without aiming facilities, and (C) skull affixed devices were found. Guidance technologies were navigation systems (all groups), prospective stereotaxy and custom designed platforms (group C). Mean total errors ranged between 4.4 and 5.4 mm for BB and 2.0 and 3.2 mm for DEP. Diagnostic yield of BB was 89-100%. The clinical success rate for DEP was 96-100%. Frameless stereotactic targeting devices may reach targeting errors and clinical results comparable with standard frame-based stereotaxy. Advantages and disadvantages of different devices should be acknowledged to ensure optimal technical performance.International Journal of Medical Robotics and Computer Assisted Surgery 11/2011; 8(1):1-16. · 1.49 Impact Factor