Computed tomographic morphometric analysis of cervical pedicles in a multi-ethnic Asian population and relevance to subaxial cervical pedicle screw fixation.

PURPOSE: Pedicle screw instrumentation provides optimal stabilization of the cervical spine complex, but is associated with risk of neurovascular injury. Sex and ethnic disparities may compromise safe and accurate screw placement. Therefore, a comprehensive analysis of pedicle dimensions derived from computed tomography scans is pertinent for our multi-ethnic population. METHODS: Cervical spine CT of 50 patients without significant cervical spine pathology was selected. Pedicle width (PW), pedicle height (PH) and pedicle transverse angle (PTA) from C3 to C7 were measured and subsequently analyzed for sex and ethnic differences. RESULTS: The smallest mean PW was at C4 in males and C3 in females. Mean PW for males was significantly greater than females at all levels (P < 0.05). 8 % of our population had at least one PW < 4.00 mm. At C5, C6 and C7 there is zero percent incidence of PW < 4.00 mm. The mean PH in males was significantly greater than females at all levels (P < 0.05), but no statistically significant sex differences in mean PTA values were found. There were significant ethnic differences in mean PW of males at C4, C5 and C7 (P < 0.05) and mean PH of females at C3, C4 and C7 (P < 0.05). CONCLUSIONS: Transpedicular screw fixation is generally feasible in our population except for 8 % with at least one PW < 4.00 mm. However, in view of significant sex and ethnic morphometric variability, pre-operative CT evaluation together with image-guided screw placement is highly advised to ensure safety and accuracy.

Metallosis with spinal implant loosening after spinal instrumentation: A case report.

BACKGROUND: Spinal metallosis is a rare complication following spinal instrumentation whereby an inflammatory response to the metal implants results in the development of granulomatous tissue. CASE SUMMARY: We describe the case of a 78-year-old woman who had recurrence of back pain 5 years after lumbar spine posterior decompression and instrumented fusion. Lumbar spine radiographs showed hardware loosening and magnetic resonance imaging showed adjacent segment disease. Revision surgery revealed evidence of metallosis intraoperatively. CONCLUSION: Spinal metallosis can present several years after instrumentation. Radiography and computed tomography may demonstrate hardware loosening secondary to metallosis. Blood metal concentrations associated with spinal metallosis have yet to be established. Hence, metallosis is still an intraoperative and histopathological diagnosis. The presence of metallosis after spinal instrumentation likely indicates a more complex underlying problem: Pseudarthrosis, failure to address sagittal balance, infection, and cross-threading of set screws. Hence, identifying metallosis is important, but initiating treatment promptly for symptomatic implant loosening is of greater paramount.

Characteristics and Postoperative Outcomes for High Cervical versus Subaxial Cervical Intradural Extramedullary Tumors: A Multicenter Study.

BACKGROUND: High cervical intradural extramedullary tumors are uncommon. Their relationship to surrounding neural structures and vertebral arteries makes surgical excision challenging. No previous studies have compared high cervical to subaxial cervical intradural extramedullary spinal tumors to elucidate their unique characteristics and surgical outcomes. METHODS: We performed a retrospective study in which patients who underwent excision of a cervical intradural extramedullary tumor were divided into a high cervical group and a subaxial cervical group. Variables included sex, age, Charlson Comorbidity Index, volume, laterality, preoperative weakness, use of neuromonitoring and drains, instrumented fusion, complications, length of stay, histology, discharge location, recurrence, and duration of follow-up. Variables were compared between the 2 groups. Limb power and Nurick classification were charted preoperatively, at discharge, and at 6 months to plot their recovery trajectory. RESULTS: Eighty-four patients with a total of 90 tumors were enrolled, including 40 patients in the high cervical group and 44 patients in the subaxial spine group. More patients with neurofibromas (P = 0.011) and bilateral tumors (P = 0.044) were in the high cervical group. A greater prevalence of neurofibromatosis type 1 was significant for bilateral high cervical tumors (P = 0.033). More patients in the subaxial group had instrumented fusion (P = 0.045). More patients in the high cervical group had improvement in limb power (P = 0.025) and Nurick classification (P = 0.0001) postoperatively before discharge. By 6 months, both groups had similar recovery. No mortality was attributable to surgery in either group. CONCLUSION: High cervical intradural extramedullary spine tumors have more bilateral tumors associated with neurofibromatosis type 1. Despite the challenging anatomy, surgical resection is safe with good outcomes in this group.

A prospective study on the use of intraoperative computed tomography (iCT) for image-guided placement of thoracic pedicle screws.

BACKGROUND: Placement of thoracic pedicle screws is a technically demanding procedure. The risk of thoracic pedicle breaches range from 6.5 to 41%. Current image guidance systems consist of computer based systems utilizing preoperative CT scans or 2D/3D intraoperative fluoroscopy. OBJECTIVE: The aim of this prospective study was to evaluate the clinical feasibility and accuracy of a new intraoperative CT (iCT) based image guidance system for thoracic pedicle screw instrumentation. METHODS: We prospectively studied the use of iCT for the first 43 consecutive cases for which thoracic pedicle screws were inserted as part of the instrumentation for spinal fusion between April 2008 and July 2011. In every case, a post-instrumentation intraoperative check CT was done before wound closure to assess accuracy of implant placement. Outcomes were analysed with regards to the incidence of pedicle wall violations detected on intraoperative check CT imaging, and the rate of immediate intraoperative revision of misplaced screws. Pedicle violations were graded according to an established classification system. RESULTS: A total of 261 thoracic pedicle screws (T1-T12) were inserted in 43 patients (age range 13-83). Mean follow-up was 12 months. There were 7 (2.7%) pedicle violations detected on the intraoperative check CT. Out of the seven, three were grade I (< 2 mm), two were grade II (2-4 mm) and rest two were grade III (> 4 mm) violations. Only four of the screws (1.5%) that breached the pedicle wall by more than 2 mm were immediately revised before wound closure. CONCLUSION: The iCT based spinal neuronavigation system allowed for highly safe and accurate placement (97.3%) of thoracic pedicle screws in our institution with no neurovascular injury reported.

Utility of a high-definition 3D digital exoscope for spinal surgery during the COVID-19 pandemic.

The COVID-19 pandemic creates unique challenges in the practice of spinal surgery. We aim to show how the use of a high-definition 3D digital exoscope can help streamline workflows, and protect both patients and healthcare staff.

The feasibility of producing patient-specific acrylic cranioplasty implants with a low-cost 3D printer.

OBJECT Commercially available, preformed patient-specific cranioplasty implants are anatomically accurate but costly. Acrylic bone cement is a commonly used alternative. However, the manual shaping of the bone cement is difficult and may not lead to a satisfactory implant in some cases. The object of this study was to determine the feasibility of fabricating molds using a commercial low-cost 3D printer for the purpose of producing patient-specific acrylic cranioplasty implants. METHODS Using data from a high-resolution brain CT scan of a patient with a calvarial defect posthemicraniectomy, a skull phantom and a mold were generated with computer software and fabricated with the 3D printer using the fused deposition modeling method. The mold was used as a template to shape the acrylic implant, which was formed via a polymerization reaction. The resulting implant was fitted to the skull phantom and the cranial index of symmetry was determined. RESULTS The skull phantom and mold were successfully fabricated with the 3D printer. The application of acrylic bone cement to the mold was simple and straightforward. The resulting implant did not require further adjustment or drilling prior to being fitted to the skull phantom. The cranial index of symmetry was 96.2% (the cranial index of symmetry is 100% for a perfectly symmetrical skull). CONCLUSIONS This study showed that it is feasible to produce patient-specific acrylic cranioplasty implants with a low-cost 3D printer. Further studies are required to determine applicability in the clinical setting. This promising technique has the potential to bring personalized medicine to more patients around the world.

Neuromonitoring in Cervical Spine Surgery: When Is a Signal Drop Clinically Significant?

Methods@#Clinical and neuromonitoring data of 207 consecutive adult patients who underwent cervical spine surgeries at multiple surgical centers using bimodal IONM were analyzed. Signal changes were divided into three groups. Group 0 had transient signal changes in either MEPs or SSEPs, group 1 had sustained unimodal changes, and group 2 had sustained changes in both MEPs and SSEPs. The incidences of true neurological deficits in each group were recorded. @*Results@#A total of 25% (52/207) had IONM signal alerts. Out of these signal drops, 96% (50/52) were considered to be false positives. Groups 0 and 1 had no incidence of neurological deficits, while group 2 had a 29% (2/7) rate of true neurological deficits. The sensitivities of both MEP and SSEP were 100%. SSEP had a specificity of 96.6%, while MEP had a lower specificity at 76.6%. C5 palsy rate was 6%, and there was no correlation with IONM signal alerts (p=0.73). @*Conclusions@#This study shows that we can better predict its clinical significance by dividing IONM signal drops into three groups. A sustained, bimodal (MEP and SSEP) signal drop had the highest risk of true neurological deficits and warrants a high level of caution. There were no clear risk factors for false-positive alerts but there was a trend toward patients with cervical myelopathy.

Neuromonitoring in Cervical Spine Surgery: When Is a Signal Drop Clinically Significant?

Methods@#Clinical and neuromonitoring data of 207 consecutive adult patients who underwent cervical spine surgeries at multiple surgical centers using bimodal IONM were analyzed. Signal changes were divided into three groups. Group 0 had transient signal changes in either MEPs or SSEPs, group 1 had sustained unimodal changes, and group 2 had sustained changes in both MEPs and SSEPs. The incidences of true neurological deficits in each group were recorded. @*Results@#A total of 25% (52/207) had IONM signal alerts. Out of these signal drops, 96% (50/52) were considered to be false positives. Groups 0 and 1 had no incidence of neurological deficits, while group 2 had a 29% (2/7) rate of true neurological deficits. The sensitivities of both MEP and SSEP were 100%. SSEP had a specificity of 96.6%, while MEP had a lower specificity at 76.6%. C5 palsy rate was 6%, and there was no correlation with IONM signal alerts (p=0.73). @*Conclusions@#This study shows that we can better predict its clinical significance by dividing IONM signal drops into three groups. A sustained, bimodal (MEP and SSEP) signal drop had the highest risk of true neurological deficits and warrants a high level of caution. There were no clear risk factors for false-positive alerts but there was a trend toward patients with cervical myelopathy.

Delayed Occurrence of Escherichia coli Subdural Empyema Following Head Injury in an Elderly Patient: A Case Report and Literature Review.

Subdural empyema is a rare but serious intracranial infection that warrants prompt management to reduce morbidity and avoid mortality. However, clinical and radiologic features may be subtle or ambivalent. Thus a diagnosis of subdural empyema should not be discounted, especially in a patient with a history of head trauma. Treatment consists of surgery to establish bacteriologic identification and subsequently guide antibiotic therapy. Here we present a case of delayed Escherichia coli subdural empyema following a head injury in an elderly patient without significant risk factors. Computed tomography imaging was equivocal for subdural empyema. The patient underwent surgery and was treated with intravenous antibiotic therapy. Although initial improvement in the patient's clinical condition was observed, he eventually succumbed to nosocomial pneumonia. In this article, we discuss the presentation, diagnostic tools, and treatment options for subdural empyema with an emphasis on the challenges. The management conundrum that follows prompted us subsequently to review the literature.

Soft tissue chondroma mimicking "dumbbell" neurogenic tumour: a rare cause of lumbar radiculopathy.

Soft tissue chondromas are rare, benign extra-skeletal tumours of cartilaginous origin, which may rarely occur within the spinal canal. We report a patient who presented with left lumbar radiculopathy, and a peripherally-enhancing dumbbell shaped soft tissue mass involving both the intraspinal and extraspinal compartments on MRI. This was misdiagnosed as a neurogenic tumour and the patient underwent surgical removal. Histological examination revealed cartilaginous tissue. Although rare, soft tissue chondromas should be considered in the differential diagnosis of spinal dumbbell shaped tumours, especially if MRI shows peripheral contrast enhancement.

Routine spinal navigation for thoraco-lumbar pedicle screw insertion using the O-arm three-dimensional imaging system improves placement accuracy.

Modern image-guided spinal navigation employs high-quality intra-operative three dimensional (3D) images to improve the accuracy of spinal surgery. This study aimed to assess the accuracy of thoraco-lumbar pedicle screw insertion using the O-arm (Breakaway Imaging, LLC, Littleton, MA, USA) 3D imaging system. Ninety-two patients underwent insertion of thoraco-lumbar pedicle screws guided by O-arm navigation over a 27 month period. Intra-operative scans were retrospectively reviewed for pedicle breach. The operative time of patients where O-arm navigation was used was compared to a matched control group where fluoroscopy was used. A total of 467 pedicle screws were inserted. Four hundred and forty-five screws (95.3%) were placed within the pedicle without any breach (Gertzbein classification grade 0). Sixteen screws (3.4%) had a pedicle breach of less than 2mm (Gertzbein classification grade 1), and six screws (1.3%) had a pedicle breach between 2mm and 4mm (Gertzbein classification grade 2). The grade 2 screws were revised intra-operatively. There was no incidence of neurovascular injury in this series of patients. The mean operative time for O-arm patients was 5.25 hours. In a matched control group of fluoroscopy patients, the mean operative time was 4.75 hours. The difference in the mean operative time between the two groups was not statistically significant (p=0.15, paired t-test). Stereotactic navigation based on intra-operative O-arm 3D imaging resulted in high accuracy in thoraco-lumbar pedicle screw insertion.

Intraoperative computed tomographic angiography in cerebral aneurysm surgery: a pilot feasibility study.

OBJECTIVE: To assess the feasibility and potential utility of intraoperative computed tomographic angiography (iCTA) in identifying unexpected residual aneurysms and major cerebral artery occlusion after cerebral aneurysm surgery. METHODS: We prospectively studied 6 consecutive patients with ruptured anterior circulation aneurysms who underwent craniotomy and clipping. iCTA was performed in all cases after the surgeon was satisfied that the aneurysm was completely obliterated and the clip did not occlude a major artery. We analyzed the iCTA images with regard to residual aneurysm and major arterial occlusion and compared them with the postoperatively acquired angiographic images, which served as a control. Patient age and sex, aneurysm location and size, clinical presentation after rupture, and postoperative course, as well as postoperative modified Rankin Scale scores, were also recorded. RESULTS: One of the 6 patients had a residual aneurysm detected on the iCTA images, and it was confirmed on the immediate postoperative digital subtraction angiography. There were no cases of major arterial occlusion on iCTA imaging or postoperatively acquired angiographic imaging. CONCLUSION: iCTA is both feasible and potentially useful in identifying unexpected residual aneurysms and major arterial occlusion after surgical clipping of aneurysms.