Application of different thresholds for instrumentation device testing in minimally invasive lumbosacral spine fixation.

The main aim of this study was evaluating the reliability of stimulus-evoked electromyography (using different thresholds for stimulation of the instrumentation devices) for minimally invasive pedicle screw placement in the lumbosacral spine. A threshold of 5 mA was applied for the pedicle access needle. 7 mA was applied for the tapscrew and pedicle screw stimulation. The existence of threshold differences between vertebral levels was also assessed. All patients underwent postoperative computed tomography (CT) to determine the accuracy of pedicle screw placement. A total of 172 percutaneous pedicle screws were placed in 52 patients. 94.1% of screws were placed at L4, L5 and S1 vertebral levels. No statistically significant differences existed in thresholds of the pedicle access needles, tapscrews and pedicle screws between vertebral levels. In four instances, the pedicle access needle stimulation had a threshold of 5 mA (no breaches were associated). In the rest of occasions, the pedicle access needles had stimulation thresholds above 5 mA. In all instances, tapscrew and pedicle screw thresholds were above 7 mA; the tapscrews and pedicle screws had significantly greater thresholds than the pedicle access needles. No statistically significant differences existed in thresholds between tapscrews and pedicle screws. Postoperative CT imaging revealed one lateral pedicle violation. Both breach rate and false negative rate were 0.5%. No false positive cases were observed. No patients experienced postoperative pedicle screw-related neurologic deficits. A threshold of 5 mA for the pedicle access needle stimulation seems to be safe. Greater than 7 mA should be used for the tapscrew and pedicle screw stimulation.

Minimally invasive lumbar pedicle screw fixation using cortical bone trajectory - Screw accuracy, complications, and learning curve in 100 screw placements.

Cortical bone trajectory (CBT) is a novel pedicle insertion technique with comparable or superior mechanical properties and reduced invasiveness compared to traditional methods. We describe the screw accuracy, complications, and learning curve associated with CBT use. A prospective cohort study was performed involving 22 patients who underwent lumbar fusion with CBT screw placement. A total of 100 cortical screws were placed. Post-operative CT scans were reviewed to assess the adequacy of screw placement and calculate the incidence of vertebral body and pedicle breaches from cortical screw placement. Technique-related complications were examined. The entire surgical cohort was divided into two groups: early experience (first 11 patients) and late experience (last 11 patients), to study the effect of learning curve on CBT screw placement. Medial pedicle breach was observed in 6/100 cases and lateral vertebral body breach was observed in 1/100 cases. The incidence of durotomy related to the technique was 4.5% (N = 1/22). Post-surgical wound infection was seen in 9.1% of patients (N = 2/22). 66.7% (N = 4/6) of medial pedicle breaches, 100% (N = 1/1) of lateral breaches, 100% (N = 1/1) of CBT technique-related CSF leaks, and 100% (N = 2/2) of wound infections occurred in the early experience phase of our study (p = 0.0945). A shift in surgical technique and greater efficiency over time decreased the incidence of overall complications in the late cohort. The difference, however, did not reach statistical significance. A lateralized starting point for the cortical screw on the pars interarticularis and use of smaller diameter screws resulted in fewer medial pedicle out-fractures and breaches.

Stimulus-Evoked Electromyographic Monitoring During Minimally Invasive Transpedicular Implantation of Screws in Lumbosacral Spine: Threshold Value, Methodology and Clinical Effectiveness.

BACKGROUND: Stimulus-evoked electromyography (EMG) has been developed to increase the safety of transpedicular placement of screws. There is more consensus about this monitoring method in open surgery. Alarm thresholds for minimally invasive surgery are based on referential value for open surgery. Nevertheless, there are no uniform alarm criteria on this modality for minimally invasive surgery. Using an analysis of alarm threshold, methodology and clinical effectiveness on stimulus-evoked EMG monitoring for minimally invasive transpedicular implantation of screws in the lumbosacral spine, this study aims to reflect and recommend for optimizing accuracy. METHODS: Using a selection of studies, an analysis of the pedicle breach rates and breach-related clinical complication rates was made between studies on minimally invasive surgery by applying different thresholds. A second analysis of the pedicle breach rates and breach-related clinical complication rates was made between studies on open and minimally invasive surgery by applying the same threshold. RESULTS: In minimally invasive surgery, stimulus-evoked EMG has an acceptable accuracy in the detection of clinical relevant pedicle breaches. Suction limitation may alter the stimulation threshold. No significant differences in clinical effectiveness were observed between studies by applying thresholds of 5 mA, 7 mA, and 12 mA. However, a low threshold of 5 mA seems inappropriate for the tap stimulation. CONCLUSION: In minimally invasive surgery, continuous stimulation of instrumentation devices is recommended. A minimum 5-mA threshold should be used for stimulation of the pedicle access needle. Use of higher-stimulation thresholds during tapping and incorporation of an adapted continuous suction system may optimize the accuracy of stimulus-evoked EMG.

Cerebellar TMS in treatment of a patient with cerebellar ataxia: evidence from clinical, biomechanics and neurophysiological assessments.

We describe a patient with a probable diagnosis of idiopathic late-onset cerebellar atrophy who shows improvement of limb coordination, speech, and gait following 21 days of transcranial magnetic stimulation (TMS) applied to scalp regions presumably corresponding to the cerebellum. This case study provides, for the first time, a quantitative assessment of gait improvement in response to TMS therapy in ataxia, as well as neurophysiological evidence in support of modification of cerebellar-cortical interaction that may underlie some of the improvements.