Femoral metastatic pathological fractures, impending and actual fractures - A patient survival study.

INTRODUCTION: The skeleton is a common site for metastases. Prostate, breast, lung, renal and thyroid carcinomas account for 80 % of the original cancers, with the femur being the most affected long bone. With improved oncological treatments, prolonged patient survival leads to an increased prevalence of osseous metastases. This study examines the impact of preventive surgery for impending femoral pathological fracture (IFF), versus treatment of pathological femur fracture (PFF) on patient mortality and morbidity. METHODS: Retrospective cohort of 174 patients undergoing surgery due to femoral metastases (2004-2015). Eighty-two patients were with PFF, and 92 were with IFF based on the Mirels' score. The followed-up period was until 2016. Demographic data, oncological, pathological, radiation, surgical reports, outpatient clinical records, and imaging studies were examined. Exclusion criteria included primary tumours and Multiple Myeloma. RESULTS: The mean age was 64.8 ± 13.3 and 60.2 ± 11.9 years (p = 0.02) in the PFF and the IFF cohorts, with 62.1 % women and 57 % men. The breast was the most common source of femoral metastases. The average Mirels' score was 10 ± 1.2. There was an association between tumour origin and survival. Carcinoma of the lung had the worst survival, while the prostate had the most prolonged survival. Survival rates differed between IFF and PFF (p = 0.03). Postoperative complications occurred in 26 % of the patient, with no difference between IFF & PFF. CONCLUSION: Breast and lung are the most common tumours to metastasize the femur. Our study revalidates that pathological femoral fractures impede patient survival compared to impending fractures and should undergo preventive surgery. Postoperative complications do not differ between IFF and PFF but remain relatively high. Overall, patients with proximal femoral metastatic disease survive longer than previously published, probably due to improved treatment modalities.

Early surgery for thoracolumbar extension-type fractures in geriatric patients with ankylosing disorders reduces patient complications and mortality.

BACKGROUND CONTEXT: The management of trauma patients with ankylosing spinal disorders has become an issue of increasing interest. Geriatric patients frequently sustain unstable extension type vertebral fractures with ankylosed spines. In this population, studies have shown that early surgery for other injuries such as hip fractures may reduce patient complications and mortality. These studies have changed patient care protocols in many medical centers worldwide. PURPOSE: We aim to assess the relationship between the timing of surgery for unstable vertebral fractures in ankylosed spines in the geriatric population and patient outcomes. STUDY DESIGN/SETTING: Retrospective clinical study conducted in a tertiary hospital. PATIENT SAMPLE: Patients included were those diagnosed with isolated thoracolumbar extension type fractures and a spinal ankylosing disorder over 65 years old following minor trauma and with no additional injuries or neurological deficit. OUTCOME MEASURES: Primary outcome measures included postoperative medical complications and mortality at 1 and 6 months. Secondary outcome measures included rehospitalization rates, length of stay, and surgical site infections. METHODS: We searched our department's database for all that met our inclusion criteria who underwent surgery. The difference in patient outcomes that underwent early surgery defined as less than 72 hours from diagnosis as opposed to those that underwent later surgery was assessed. RESULTS: A total of 82 patients underwent surgery following a diagnosis of an extension type thoracolumbar fracture at our institution between 2015 and 2021. Of these, 50 met inclusion criteria. Nineteen patients underwent surgery less than 72 hours from diagnosis and 31 more than 72 hours from diagnosis. No difference was found in age, functional status, and Elixhauser comorbidity scores between the groups. A statistically significant difference in perioperative patient complications between the early and the late groups (p=.005) was found. Mortality at six-months was significantly different between the groups as well (p=.035). There was no statistically significant difference between the groups when comparing surgical site infections, length of hospital stay, rehospitalization within a month, and perioperative mortality. CONCLUSIONS: Time to surgery affects complication rates and six-month mortality in geriatric patients with spinal ankylosing disorders presenting with an isolated unstable hyperextension type thoracolumbar fracture. Early surgery of less than 72 hours from presentation in this patient population is recommended.

Scoliosis in RETT Syndrome: A National Referral Centre Experience.

STUDY DESIGN: This was a retrospective case series. OBJECTIVE: The objective of this study was to discuss the treatment challenges in scoliosis patients with Rett syndrome (RTT) in a national referral centre for RTT. We describe structural characteristics of curves, age of onset, genetic mutation, ambulation status, and treatment through RTT progression. Based on this unique experience, we aimed to suggest guidelines for scoliosis treatment in RTT patients. SUMMARY OF BACKGROUND DATA: RTT is a neurodevelopmental disorder associated with a mutation in the methyl-CpG binding protein 2 (MECP2) gene, primarily in females with significant features of growth failure, gastrointestinal and pulmonary dysfunction, ataxia, seizures, and intellectual disability. Scoliosis is the most common orthopedic manifestation of RTT and is present in 64%-75% of patients. No clear guidelines for scoliosis treatment in RTT are available, and typically patients are treated according to guidelines of another neuromuscular scoliosis. METHODS: Clinical and radiographic data were gathered, including MECP2 mutation type, scoliosis characteristics, preoperative treatment, surgical treatment, functional status, and postoperative follow-up. RESULTS: Our cohort included 102 patients with RTT. They were 36 who presented with scoliosis; 18 were treated surgically. C-curve was found in 17 patients and S-type in 19. Scoliosis treatment onset was 8.76 years in the C-type group and 13.88 years in the S-type group. The average curve at the time of surgery was 52.42 degrees. The average time until surgery was 2.44 years. Seventeen patients underwent posterior spinal fusion, and 1 patient underwent posterior spinal fusion+anterior spinal fusion with an average correction of 40 degrees. The most common mutation was R255X nucleotide (30% of cases). The most severe curves had mutations R168X and R270X nucleotides. CONCLUSIONS: We advise early monitoring for patients with RTT and scoliosis due to early and rapid progression. Common mutations found were R255X, R168X, R270X, and T158M. We recommend surgical treatment in every curve above 45 degrees, independently of age.

Limitations of Plain Film Radiography in Identification of Hyperextension Fractures in Patients With Ankylosing Spinal Disorders.

STUDY DESIGN: Efficacy study. OBJECTIVES: To elucidate the limitations of radiography in patients with spinal ankylosing disorders (SAD) with an emphasis on thoracolumbar injuries, which have been less focused upon. METHODS: We searched our hospital's emergency room database for patients who underwent a total spine computed tomography (CT) following a diagnosis of SAD on radiographs following a minor fall. A high-quality presentation containing 50 randomly situated anteroposterior + lateral radiographs was created. Of these, 24 contained a hyperextension type fracture diagnosed by CT. Twelve physicians-4 spine surgeons, 4 senior orthopedic residents and 4 junior orthopedic residents were requested to identify the pathologic radiographs and note the fracture level. RESULTS: Fracture diagnosis stood at 65% for the best reader. When examining the different subgroups, the mean rate of diagnosis for spine surgeons was 55% and for orthopedic residents 32%. Mean diagnosis of thoracic fractures was 26%, of lumbar fractures was 55%, and for the entire thoracolumbar spine was 40%. The interobserver agreement (kappa coefficient) was found to be 0.37 for the entire group and 0.39 for spine surgeons. This finding was statistically significant. CONCLUSIONS: The simple radiograph is an inefficient modality for diagnosis of hyperextension type thoracolumbar fractures in patients with SAD. The poor interobserver agreement rate further amplifies this finding. Advanced imaging is recommended in these patients.

Potential neurotoxicity of titanium implants: Prospective, in-vivo and in-vitro study.

Titanium dioxide (TiO2) is a frequently used biomaterial, particularly in orthopedic and dental implants, and it is considered an inert and benign compound. This has resulted in toxicological scrutiny for TiO2 in the past decade, with numerus studies showing potential pathologic downstream effects. Herein we describe case report of a 77-year-old male with subacute CNS dysfunction, secondary to breakdown of a titanium-based carotid stent and leading to blood levels 1000 times higher (3 ppm) than the reported normal. We prospectively collected tissues adjacent to orthopedic implants and found a positive correlation between titanium concentration and time of implant in the body (r = 0.67, p < 0.02). Rats bearing titanium implants or intravascularly treated with TiO2 nanoparticles (TiNP) exhibited memory impairments. A human blood-brain barrier (BBB) in-vitro model exposed to TiNP showed paracellular leakiness, which was corroborated in-vivo with the decrease of key BBB transcripts in isolated blood vessels from hippocampi harvested from TiNP-treated mice. Titanium particles rapidly internalized into brain-like endothelial cells via caveolae-mediated endocytosis and macropinocytosis and induced pro-inflammatory reaction with increased expression of pro-inflammatory genes and proteins. Immune reaction was mediated partially by IL-1R and IL-6. In summary, we show that high levels of titanium accumulate in humans adjacent to orthopedic implants, and our in-vivo and in-vitro studies suggest it may be neurotoxic.

Cost-Benefit Analysis of Routine Bone Biopsy During Augmentation of Osteoporotic Vertebral Compression Fractures.

STUDY DESIGN: Multi-center prospective study. OBJECTIVE: To analyze the cost of routine biopsy during augmentation of osteoporotic vertebral compression fractures (VCF) and the affect it has on further treatment. SUMMARY OF BACKGROUND DATA: Vertebroplasty (VP) and Balloon Kyphoplasty (BKP) are accepted treatments for VCF. Bone biopsy is routinely performed during every VCF surgery in many centers around the world to exclude an incidental finding of malignancy as the cause of the pathological VCF. The incidence been reported as 0.7% to 7.3%, however the published cohorts are small and do not discuss cost-benefit aspects. METHODS: From 2008 to 2016 we performed 122 vertebral biopsies routinely on 116 patients in three hospitals. Twenty-three patients had history of malignancy (26 biopsies) and four were suspected of having malignancy based on imaging findings. The remaining 86 patients (99 biopsies) were presumed osteoporotic VCF. RESULTS: Out of 99 biopsies in the VCF cohort group only one yielded an unsuspected malignancy (1.16%), positive for multiple myeloma (MM). The ability of clinical assessment and imaging alone to diagnose malignancy was found to be 91.7% sensitive and 84.2% specific in our cohort. CONCLUSION: Routine bone biopsy during vertebral augmentation procedure is a safe option for evaluating the cause of the VCF but has significant cost to the health system. The cost of one diagnosed case of unsuspected malignancy was $31,000 in our study. The most common pathology was MM, which has not been proven to benefit from early diagnosis. When comparing clinical diagnosis with imaging, a previous history of malignancy was found in only 40.7% of VCF patients, while imaging was 100% accurate in predicting presence of malignancy on biopsy. This study reassures spine surgeons in their ability to diagnose malignant VCFs and does not support the significant cost of routine bone biopsies. LEVEL OF EVIDENCE: 3.

Whole Spine CT Scan for the Detection of Acute Spinal Fractures in Diffuse Idiopathic Skeletal Hyperostosis Patients Who Sustained Low-energy Trauma.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The aim of this study was to evaluate the role and value of whole-spine computerized tomography (WSCT) versus radiographs and targeted CT to tender spinal regions in patients with diffuse idiopathic skeletal hyperostosis (DISH) after low-energy trauma. SUMMARY OF BACKGROUND DATA: Subjects with DISH are prone to spinal fractures even after low-impact trauma due to a rigid spinal structure. METHODS: One-hundred forty-seven subjects (average age: 83 years, M:F 64/83) with verified DISH (Resnick and Niwayama radiographic criteria) on WSCT who were admitted to the emergency room (ER) after low-energy trauma and for whom there were radiographs of at least the thoracic and lumbar spine were evaluated for the presence of acute spinal fractures on both radiographs and WSCT. Agreement between fracture location and spinal tenderness location (cervical, thoracic, or lumbar) as reported in the medical record was evaluated. RESULTS: Significantly more acute fractures were detected on WSCT compared to radiographs (55 and 32, P < 0.00001, respectively). The site of tenderness was not indicative of the fractured spinal segment in 57% of all acute fractures (seven cervical, 15 thoracic, and 16 lumbar). No fracture was detected on WSCT in 10 subjects with an unspecified pain location. Multilevel distant fractures were detected in two patients with a specified pain location to only one of the fractures. CONCLUSION: WSCT in DISH subjects after low-impact trauma is mandatory due to the high prevalence of acute fractures and the low specificity for fracture detection on radiographs. A targeted CT approach to the tender spinal segment proved to be inadequate and would have missed 57% of the acute single fractures with incompatible spinal tenderness location. These results support the significant role of WSCT in the ER setting for detecting and pinpointing the spinal fracture site of DISH subjects who present with low-impact trauma. LEVEL OF EVIDENCE: 3.

Neural Cell Adhesion Molecule (NCAM) a Serum Biomarker Indicative for the Severity of Cervical Spondylotic Myelopathy.

STUDY DESIGN: Peripheral blood samples were obtained from 25 patients with cervical spondylotic myelopathy (CSM) and 13 healthy volunteers. OBJECTIVES: Our aim was to investigate the significance of neurodegenerative biomarkers in patients with CSM and correlate their expression with CSM severity. SUMMARY OF BACKGROUND DATA: CSM is a common disorder involving chronic progressive compression of the cervical spinal resulting in progressive neurological impairment that ranges from mild tingling in the upper limbs to complete quadriplegia. However, the immunological background related to the neurodegenerative damage and its significance in CSM is still unclear. METHODS: Protein expression profiles of 14 neurodegenerative biomarkers were measured by multiplex Luminex bead assay and further analyzed by group comparison statistics, correlation studies, and receiver-operating characteristic analysis. RESULTS: Eleven of 14 biomarkers were significantly elevated in CSM patients as compared with healthy subjects (P<0.05). Specifically, the clinical severity of CSM on the scales of Nurick and modified Japanese Orthopedics Association scale (mJOA) was inversely related to neural cell adhesion molecule (NCAM) levels (r=-0.529, P=0.007; r=-0.519, P=0.001, respectively). CONCLUSIONS: Serum level of neural cell adhesion molecule may serve as a diagnostic biomarker correlating with the severity of CSM.

Preventing Biofilm Formation by Dairy-Associated Bacteria Using Peptide-Coated Surfaces.

Biofilm-forming bacteria, which colonize the surfaces of equipment in the dairy industry, may adversely affect the safety and quality of the milk and its products. Despite numerous efforts to combat biofilm formation, there is still no effective technological means to thoroughly solve the biofilm problem in the dairy industry. Here, we introduced peptide-based coating in order to modify the physical properties of the stainless steel surface by affecting its availability for bacterial adhesion. We found that the coated surface displays a notable decrease in the ability of bacterial cells to attach and to subsequently form biofilm by Gram-positive Bacillus licheniformis and Gram-negative Pseudomonas aeruginosa. Furthermore, the coated surface retained its anti-biofilm ability following its exposure to raw milk. Importantly, the modified surface did not affect the milk coagulation process or its nutritious properties and quality. Overall, this anti-biofilm approach may serve as an attractive solution for the dairy industry in its struggle against bacterial contamination.

Cervical MRI Rating Scale: Innovative Approach to Differentiate between Demyelinating and Disc Lesions.

PURPOSE: The difficult differentiation between multiple sclerosis (MS) lesions and cervical spondylotic myelopathy (CSM) in the cervical spine is well known. The magnetic resonance imaging (MRI) appearance of both lesions is similar, and clinical parameters are usually used for diagnosis. The objective was to establish a reliable radiologic paradigm for diagnosis of demyelinating lesions in the cervical spine. METHODS: The MRI studies of 33 patients with MS (42 lesions) and 55 patients with CSM (60 lesions) were obtained. Lesions were evaluated for vertebral level, lesion location and size in the sagittal and axial planes, cord thickness, well-defined or ill-defined borders, presence of edema and enhancement with gadolinium. Significant differences were used to create a paradigm, which was used for the evaluation of a different group of 32 MRIs with 42 concomitant MS and CSM lesions. RESULTS: Significant differences were seen in the level, location within the cord in both planes, lesion size, cord thickness and lesion border. The MS lesions were well-defined lesions found in C1-3, posterior in the sagittal plane, central in the axial plane, with a normal or increased cord thickness. Good agreement was seen in the validation stage. CONCLUSION: The new CSM-MS lesion score allows accurate diagnosis of demyelinating lesions in the cervical spine vs. CSM lesions.

Eliminating the Need for Biocidal Agents in Anti-Biofouling Polymers by Applying Grafted Nanosilica Instead.

A nondestructive one-step approach was applied for grafting biocide-free monodispersed silica nanoparticles (SNPs) with a diameter of 30 ± 10 nm on polystyrene, polyethylene, and polyvinyl chloride surfaces. The prepared surfaces were comprehensively characterized using spectroscopic (Fourier transform infrared attenuated total reflection, ultraviolet-visible, and X-ray photoelectron spectroscopy) and microscopic (high-resolution scanning electron microscopy and atomic force microscopy) methods. The modified polymers were found to maintain their original mechanical and physical properties, while their nanoroughness on the other hand had risen by 1.6-2.7 times because of SNP grafting. The SNP-grafted surfaces displayed anti-biofouling properties, resulting in a significant reduction in the attached Gram-positive Bacillus licheniformis or Gram-negative Pseudomonas aeruginosa bacteria compared to their nongrafted counterparts. Confocal laser scanning microscopy and scanning electron microscopy studies have confirmed that bacterial cells could not successfully adhere onto the SNP-grafted polymer films regardless of the polymer type, and their biofilm formation was therefore damaged. The presented facile and straightforward protocol allows eliminating the need for biocidal agents and resorts to grafted nanosilica instead. This strategy may serve as a feasible and safe platform for the development of sustainable anti-biofouling surfaces in biomedical devices; food, water, and air treatment systems; and industrial equipment.

Association between body mass index, body height, and the prevalence of spinal deformities.

BACKGROUND CONTEXT: The most common spinal deformities among adolescents are adolescent idiopathic scoliosis (AIS; 2%-3% prevalence) and Scheuermann kyphosis (SK; 1%-8% prevalence). Both are believed to have a genetic influence in their etiology. The association between body mass index (BMI) and body stature and their possible association to spinal deformities is uncertain. STUDY DESIGN: A cross-sectional prevalence study. PURPOSE: To examine the prevalence of all adolescent spinal deformities according to the extent of their severity as well as their possible association to BMI and body height. OUTCOME MEASURES: Subjects diagnosed as having spinal deformities were classified into one of three severity groups; "Mild," "Intermediate," or "Severe," according to their curve scoliosis or kyphosis measurement with a standing X-ray. METHODS: The data for this study were derived from a medical database containing records of 17-year-old male and female patients before their recruitment into mandatory military service. Information on the disability codes associated with spinal deformities according to the Regulations of Medical Fitness Determination was retrieved. Logistic regression models were used to assess the association between the BMI and body height to various degrees of spinal deformities by severity. RESULTS: The study cohort included 829,791 consecutive subjects, of whom 103,249 were diagnosed with spinal deformities (76% were mild in degree). The prevalence of spinal deformities was significantly greater among the underweight male and female patients (p<.001). Increased BMI had a protective effect for developing spinal deformities. The odds ratios for severe spinal deformities were greater compared with mild spinal deformities in the underweight groups. The risk for developing spinal deformities increased significantly with height for both genders (p<.001). CONCLUSIONS: An association between height and the risk for spinal deformities by severity was found for all height groups. Below normal BMI is associated with severity of spinal deformities, whereas above-normal BMI apparently has a protective effect. Body height is also positively associated with the severity of spinal deformities.

Associations of body mass index and body height with low back pain in 829,791 adolescents.

Body mass index (BMI) (calculated as weight (kg)/height (m)²) and height are linked to the pathogenesis of low back pain, but evidence-based confirmation is lacking. We examined the prevalence of low back pain in adolescents and its association with BMI and height. Disability clauses (official military limitations related to a person's health status) indicating low back pain severity were divided according to symptoms of low back pain alone and symptoms of low back pain with objective corroborating findings. All 829,791 males and females undergoing mandatory premilitary recruitment examinations since 1998 were included. Logistic regression models assessed the relationships of BMI and height with low back pain. Prevalence of low back pain was 0.2% for both males and females with objective findings and 5.2% for males and 2.7% for females without objective findings. Higher BMI was significantly associated with low back pain in males (for overweight, odds ratio = 1.097, P < 0.001; for obese, odds ratio = 1.163, P < 0.001) and in females (for overweight, odds ratio = 1.174, P < 0.001; for obese, odds ratio = 1.211, P < 0.001). Height was associated with increased risk of low back pain in both genders. Odds ratios for low back pain in the tallest group compared with the shortest group were 1.438 (P < 0.001) for males and 1.224 (P < 0.001) for females. Low back pain with or without objective findings was associated with overweight and obesity as well as with height.

Percutaneous Posterolateral Transforaminal Endoscopic Discectomy: Clinical Outcome, Complications, and Learning Curve Evaluation.

Ongoing technological development combined with better understanding of endoscopic anatomy has made posterolateral endoscopic discectomy an appealing surgical option for the management of herniated lumbar disc. We evaluated clinical outcomes, complication rates, and surgical learning curve with the percutaneous posterolateral transforaminal endoscopic discectomy technique (PPTED). PPTED was performed on 150 patients from 2004 to 2008. And 124 patients were available for follow-up. Data regarding pain, postoperative complications, neurological status, operation time, and subjective patient satisfaction were recorded. A satisfactory clinical outcome as reflected in the VAS (mean 3.6) and ODI improvement (mean 21%) scores was reported; 20.9% of the patients required additional surgery. Learning curve assessment showed a significant difference (p = 0.043) for fewer revision surgeries as surgeons became more experienced. Patients who had endoscopic discectomy as a primary surgery achieved significantly lower VAS (p = 0.04) and ODI improvement (p = 0.004) scores compared with patients having transforaminal endoscopic discectomy as revision surgery. The complication rate was 1.6%, including one case of post-surgery hypoesthesia and one deep wound infection. The percutaneous posterolateral transforaminal endoscopic discectomy technique has a satisfactory clinical outcome with a low complication rate. Results for endoscopic surgery for revision or recurrent disc herniation are comparable to those of open revision surgery; the steep learning curve can be overcome with training and suitable patient selection.

Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: retrospective study.

STUDY DESIGN: Retrospective, multicenter study of robotically-guided spinal implant insertions. Clinical acceptance of the implants was assessed by intraoperative radiograph, and when available, postoperative computed tomography (CT) scans were used to determine placement accuracy. OBJECTIVE: To verify the clinical acceptance and accuracy of robotically-guided spinal implants and compare to those of unguided free-hand procedures. SUMMARY OF BACKGROUND DATA: SpineAssist surgical robot has been used to guide implants and guide-wires to predefined locations in the spine. SpineAssist which, to the best of the authors' knowledge, is currently the sole robot providing surgical assistance in positioning tools in the spine, guided over 840 cases in 14 hospitals, between June 2005 and June 2009. METHODS: Clinical acceptance of 3271 pedicle screws and guide-wires inserted in 635 reported cases was assessed by intraoperative fluoroscopy, where placement accuracy of 646 pedicle screws inserted in 139 patients was measured using postoperative CT scans. RESULTS: Screw placements were found to be clinically acceptable in 98% of the cases when intraoperatively assessed by fluoroscopic images. Measurements derived from postoperative CT scans demonstrated that 98.3% of the screws fell within the safe zone, where 89.3% were completely within the pedicle and 9% breached the pedicle by up to 2 mm. The remaining 1.4% of the screws breached between 2 and 4 mm, while only 2 screws (0.3%) deviated by more than 4 mm from the pedicle wall. Neurologic deficits were observed in 4 cases yet, following revisions, no permanent nerve damage was encountered, in contrast to the 0.6% to 5% of neurologic damage reported in the literature. CONCLUSION: SpineAssist offers enhanced performance in spinal surgery when compared to free-hand surgeries, by increasing placement accuracy and reducing neurologic risks. In addition, 49% of the cases reported herein used a percutaneous approach, highlighting the contribution of SpineAssist in procedures without anatomic landmarks.

Bone-mounted miniature robotic guidance for pedicle screw and translaminar facet screw placement: part 2--Evaluation of system accuracy.

OBJECTIVE: To evaluate the accuracy of a novel bone-mounted miniature robotic system for percutaneous placement of pedicle and translaminar facet screws. METHODS: Thirty-five spinal levels in 10 cadavers were instrumented. Each cadaver's entire torso was scanned before the procedure. Surgeons planned optimal entry points and trajectories for screws on reconstructed three-dimensional virtual x-rays of each vertebra. Either a clamp or a minimally invasive external frame was attached to the bony anatomy. Anteroposterior and lateral fluoroscopic images using targeting devices were obtained and automatically registered with the virtual x-rays of each vertebra generated from the computed tomographic scan obtained before the procedure. A miniature robot was mounted onto the clamp and external frame and the system controlled the robot's motions to align the cannulated drill guide along the planned trajectory. A drill bit was introduced through the cannulated guide and a hole was drilled through the cortex. Then, K-wires were introduced and advanced through the same cannulated guide and left inside the cadaver. The cadavers were scanned with computed tomography after the procedure and the system's accuracy was evaluated in three planes, comparing K-wire positions with the preoperative plan. A total of fifty-five procedures were evaluated. RESULTS: Twenty-nine of 32 K-wires and all four screws were placed with less than 1.5 mm of deviation; average deviation was 0.87 +/- 0.63 mm (range, 0-1.7 mm) from the preoperative plan in this group. Sixteen of 19 K-wires were placed with less than 1.5 mm of deviation. There was one broken and one bent K-wire. Another K-wire was misplaced because of collision with the previously placed wire on the contralateral side of the same vertebra because of a mistake in planning, resulting in a 6.5-mm deviation. When this case was excluded, average deviation was 0.82 +/- 0.65 mm (range, 0-1.5 mm). CONCLUSION: These results verify the system's accuracy and support its use for minimally invasive spine surgery in selected patients.

Bone-mounted miniature robotic guidance for pedicle screw and translaminar facet screw placement: Part I--Technical development and a test case result.

OBJECTIVE: To introduce a new miniature robot (SpineAssist; MAZOR Surgical Technologies, Caesarea, Israel) that has been developed and tested as a surgical assistant for accurate percutaneous placement of pedicle screws and translaminar facet screws. METHODS: Virtual projections in three planes-axial, lateral, and anteroposterior-are reconstructed for each vertebra from a preoperative computed tomographic (CT) scan. On a specially designed graphic user interface with proprietary software, the surgeon plans the trajectory of the screws. Intraoperative fluoroscopic x-rays with targeting devices are then matched with the CT-based virtual images, as well as the surgeon's plan. A clamp is attached to the spinous process or a minimally invasive frame (Hover-T frame; MAZOR Surgical Technologies) is mounted to the iliac crest and one spinous process. The miniature robot is then attached to the clamp and/or frame. On the basis of combined CT scan and fluoroscopic data, the robot aligns itself to the desired entry point and trajectory, as dictated by the surgeon's preoperative plan. RESULTS: A test case in a cadaver lumbar spine was performed in which four screws and two rods were inserted, using a minimally invasive technique, combining the SpineAssist system and Hover-T frame in conjunction with the PathFinder system (Spinal Concept Inc., Austin, TX). The discrepancy between the planned and actual screw trajectories was measured by means of postprocedural CT scan. Overall, the four screws were implanted with an average deviation of 1.02 +/- 0.56 mm (range, 0-1.5 mm) from the surgeon's plan. CONCLUSION: These preliminary results confirm the system's accuracy and support its use in minimally invasive spine surgery applications.