A quantitative accuracy assessment of the use of a rigid robotic arm in navigated placement of 726 pedicle screws.

BACKGROUND: Traditional minimally invasive fluoroscopy-based techniques for pedicle screw placement utilize guidance, which may require fluoroscopic shots. Computerized tomography (CT) navigation results in more accurate screw placement. Robotic surgery seeks to establish access and trajectory with greater accuracy. OBJECTIVE: This study evaluated the screw placement accuracy of a robotic platform. METHODS: Demographic data, preoperative/postoperative CT scans, and complication rates of 127 patients who underwent lumbosacral pedicle screw placement with minimally invasive navigated robotic guidance using preoperative CT were analyzed. RESULTS: On the GRS scale, 97.9% (711/726) of screws were graded A or B, 1.7% (12/726) of screws graded C, 0.4% (3/726) of screws graded D, and 0% graded E. Average offset from preoperative plan to final screw placement was 1.9 ± 1.5 mm from tip, 2.2 ± 1.4 mm from tail and 2.9 ± 2.3° of angulation. CONCLUSIONS: Robotic-assisted surgery utilizing preoperative CT workflow with intraoperative fluoroscopy-based registration improves pedicle screw placement accuracy within a patient's pedicles.

Navigated robotic assistance results in improved screw accuracy and positive clinical outcomes: an evaluation of the first 54 cases.

Computer-aided navigation and robotic guidance systems have become widespread in their utilization for spine surgery. A recent innovation combines these two advances, which theoretically provides accuracy in spinal screw placement. This study describes the cortical and pedicle screw accuracy for the first 54 cases where navigated robotic assistance was used in a surgical setting. This is a retrospective chart review of the initial 54 patients undergoing spine surgery with pedicle and cortical screws using robotic guidance with navigation. A computed tomography (CT)-based Gertzbein and Robbins System (GRS) was used to classify pedicle screw accuracy. Screw tip, tail, and angulation offsets were measured using image overlay analysis. Screw malposition, reposition, and return to operating room rates were collected. 1 of the first 54 cases was a revision surgery and was excluded from the study. Ten screws were placed without the robot due to surgeon discretion and were excluded for the data analysis of 292 screws. Only 0.68% (2/292) of the robot-assisted screws was repositioned based on surgeon discretion. Based on the GRS CT-based grading, 98.3% (287/292) were graded A or B, 1.0% (3/292) screws were graded C, and only 0.7% (2/292) screws was graded D. The average offset from preoperative plan to actual final placement was 1.9 mm from the tip, 2.3 mm from the tail, and 2.8° of angulation. In the first 53 cases, 292 screws placed with navigated robotic assistance resulted in a high level of accuracy (98.3%), adequate screw offsets from planned trajectory, and zero complications.

Focal hole versus screw stimulation to prevent false negative results in detecting pedicle breaches during spinal instrumentation.

OBJECTIVE: We describe a stimulus-evoked EMG approach to minimize false negative results in detecting pedicle breaches during lumbosacral spinal instrumentation. METHODS: In 36 patients receiving 176 lumbosacral pedicle screws, EMG threshold to nerve root activation was determined using a focal probe inserted into the pilot hole at a depth, customized to the individual patients, suitable to position the stimulating tip at the point closest to the tested nerve root. Threshold to screw stimulation was also determined. RESULTS: Mean EMG thresholds in 161 correctly fashioned pedicle instrumentations were 7.5 mA ±â€¯2.46 after focal hole stimulation and 21.8 mA ±â€¯6.8 after screw stimulation. Direct comparison between both thresholds in individual pedicles showed that screw stimulation was always biased by an unpredictable leakage of the stimulating current ranging from 10 to 90%. False negative results were never observed with hole stimulation but this was not true with screw stimulation. CONCLUSIONS: Focal hole stimulation, unlike screw stimulation, approaches absolute EMG threshold as shown by the lower normal limit (2.6 mA; p < 0.05) that borders the upper limit of threshold to direct activation of the exposed root. SIGNIFICANCE: The technique provides an early warning of a possible pedicle breakthrough before insertion of the more harmful, larger and threaded screw.

Non-invasive high voltage electrical stimulation as a monitoring tool of nerve root function in lumbosacral surgery.

OBJECTIVE: To verify the safety and clinical use of non-invasive high-voltage electrical stimulation (HVES) in patients with compressive radiculopathy. To test the feasibility of HVES to survey nerve root function during lumbosacral surgery. METHODS: In 20 patients undergoing lumbosacral surgery for degenerative spinal diseases, compound muscle action potentials (CMAPs) evoked by maximal HVES were bilaterally recorded throughout surgery from L3 to S2 radicular territories. A preliminary study was performed in awake patients to rule out detrimental effects caused by HVES. RESULTS: Preoperative study confirmed the safety of HVES. Unexpectedly, a transient but significant remission of pain was observed after root stimulation. Intraoperative monitoring (IOM) was accomplished in all patients. HVES never hindered surgical procedures and never caused mechanical damage within the operatory field. In 4 patients acute, highly focal and reversible conduction failure was promptly detected by HVES in radicular territories congruent with the root manipulated at that moment. CONCLUSIONS: HVES is a safe and sensitive tool to monitor nerve root function in lumbosacral surgery. SIGNIFICANCE: The method is based on the assumption that any acute conduction failure occurring during surgery can be immediately and unambiguously detected by HVES if root stimulation is supramaximal and delivered rostral to the surgical level.

Systemic cancer metastasis in a meningioma: report of two cases and review of the literature.

"Tumour-to-tumour" phenomenon is a rare event; meningioma has been reported as the most common primary intracranial tumour to harbour metastases, the majority of which arise from breast and lung carcinomas. Several hypotheses have been previously proposed to explain this occurrence, but the exact mechanisms responsible for the development of metastases in meningiomas are not known. Magnetic resonance imaging (MRI) and spectroscopy could be useful to hypothesize this uncommon event, but its preoperative diagnosis remains highly difficult. Two patients are reported, with breast and renal carcinoma metastases in an intracranial meningioma. Pathogenetic mechanisms and neuroimaging features are discussed. A brief review of the literature is presented.

Vasospasm after SAH due to aneurysm rupture of the anterior circle of Willis: value of TCD monitoring.

OBJECTIVE: The aim of this study was to verify the presence of angiographic vasospasm in patients with transcranial Doppler (TCD) of high velocities after subarachnoid hemorrhage (SAH). METHODS: Seven hundred and eighty-six cases admitted within 48 hours after SAH due to the rupture of anterior circulation aneurysm, were prospectively studied with TCD. In cases of TCD velocities higher than 120 cm/s (TCD vasospasm), the patient underwent a control angiography. Hunt-Hess and Fisher's grade on admission CT and location of the aneurysm were related to occurrence of TCD vasospasm. The increase in TCD velocities within 24 hours was calculated and related to the presence of cerebral ischemia on discharge CT, considering three groups of patients: Group A with an increase in velocities higher than 60%, Group B with an increase in velocities between 30 and 60%, and Group C with an increase in velocities lower than 30%. RESULTS: TCD vasospasm was observed in 216 patients (27%). In 97% of patients with TCD vasospasm on middle cerebral artery (MCA) and in 71% with TCD vasospasm on anterior cerebral artery (ACA), control angiography confirmed the vasospasm, with a significant lower diagnostic TCD predictivity of ACA spasm (chi2=28.204, p=0.000). The overall positive predictive value of TCD was 89%. There was no significant correlation of TCD vasospasm with clinical status on admission and location of the aneurysm, but a significant correlation between occurrence of TCD vasospasm and Fisher's grade (chi2=15.470, p=0.002) and between the increase rate in TCD velocities and cerebral ischemia (chi2=56.564, p=0.000). CONCLUSION: Our study shows a good correlation between TCD and angiography to detect vasospasm on MCA, but the correlation is low for ACA. TCD alone cannot discriminate different hemodynamic pathways after SAH.

Cystic versus solid vestibular schwannomas: a series of 80 grade III-IV patients.

Cystic acoustic neuromas are less frequent than solid ones and present different clinical and radiological features. Cystic schwannomas are larger, show a shorter clinical history and a different risk of postoperative complications. This study was designed to compare surgical results and complications of solid and cystic vestibular schwannomas of matching size operated upon via either a retrosygmoid or a translabyrinthine approach. The study included 80 patients presenting with grade III and IV acoustic vestibular schwannomas referred to the Neurosurgical and ENT team in the Department of Neuroscience of Torino, Italy. Twenty-six were cystic and 54 were solid tumours. Clinical history, surgical results and complications were compared between the two groups. In cystic tumors, rapid clinical worsening is common, due to sudden expansion of cystic elements. Tighter adherences are found between cystic tumours and nervous elements (particularly brainstem and possibly facial nerve), once compared to solid ones. Operative morbidity appears to be higher in cystic tumours. A wait and see policy should not to be applied to patients with cystic tumours. Careful technique, possibly sharp dissection, to divide the tumour adherences from the nervous tissue must be employed, in order to avoid lesions on brainstem veins and traction on a thin facial nerve. Severe complications may be caused by the excessive efforts to dissect brainstem adherences.