Presentations selected from submitted abstracts
Short-term lumbar plexus morbidity related to mini-open retroperitoneal transpsoas corpectomy
Lumbar plexus injury is a well-described complication of retroperitoneal transpsoas approach to the lumbar spine. The rate of lumbar plexopathy seems to be underestimated and underreported in literature.
However, there is no specific data available concerning plexopathies following retroperitoneal transpsoas corpectomies. Corpectomies demand a wide surgical corridor and significant retraction on the psoas fibers, and require surgical manipulation of lumbar plexus branches.
We reviewed the reports of 17 consecutive patients, who had undergone to a left sided mini-open retroperitoneal transpsoas corpectomy for traumatic and osteoporotic fractures between 2005 and 2012. We retrospectively analyzed the pre and postoperative neurological status, and followed the patient’s clinical condition at 6 months. Lumbar plexus integrity was assessed by a close clinical neurological examination. Sensory deficits were assessed and classified according to Ahmadian et al. (Sensory Dermal Zone - SDZ I: subcostal, iliohypogastric, ilioinguinal, genitofemoral nerves, II: lateral femoral cutaneous nerve, III: femoral and saphenous nerve, IV: obturator nerve).
Fourteen patients (82%) had a preoperative neurological deficit related to the fracture. Lumbar vertebrae involved were L2 (6 patients), L3 (8 patients), and L4 (3 patients). The fractures were either traumatic (14) or osteoporotic (3). At discharge, 8/17 patients (47%) had new sensory deficits attributable to nerve manipulation (SDZ I: 2, II: 3, III: 3, IV: 0). 2 patients presented psoas muscle weakness due to the surgical access. One patient could not be assessed due to preexisting motor and sensory deficits related to the fracture.
The 6 months follow-up showed the persistence of surgery-related sensory deficits in all the cases. N=1/2 patients recovered from psoas weakness. One patient, who was already presenting SDZ III disturbance after the first surgery, underwent a second surgery because of a cage displacement.
Our findings suggest that mini-open retroperitoneal transpsoas corpectomy involves a relatively high risk of lumbar plexopathy, mostly confined to sensory deficits. Sensory deficits tend to be unchanged at 6 months and motor deficits due to the surgical route are rare. More clinical trials with long-term follow up are necessary to assess lumbar plexus injuries, recovery rates and their impact on patients’ quality of life.
Navigated intra-operative 2-D ultrasound in High Grade Glioma surgery: impact on extent of resection and patient outcome
Aims: Maximizing extent of resection (EOR) and reducing residual tumor volume (RTV) while preserving neurological functions is the main goal in the surgical treatment of gliomas. Navigated Intra-operative ultrasound (N-ioUS) is a real-time imaging technique which, combining the advantages of ultrasound and conventional neuronavigation (NN), allows for overcoming the limitations of the latter, such as brain shift and brain deformation. In this study we evaluate the impact of real-time NN combining ioUS and pre-operative magnetic resonance imaging (MRI) on maximizing EOR in glioma surgery compared to standard NN.
Methods: We retrospectively reviewed a series of 60 cases: 9 World Health Organization Grade (WHO) III and 51 WHO IV operated on for supratentorial gliomas, 31 operated under the guidance of N-ioUS and 29 resected with standard NN. All cases were evaluated considering age, location of the tumor (30 eloquent and 40 non-eloquent), pre- and post-operative Karnofsky Performance Status (KPS), EOR and, if any, post-operative complications. Volumetric pre-operative and 48hours post-operative MRI was used to determine EOR.
Results: The rate of gross total resection (GTR: EOR=100%) in NN group was 44.8% and EOR≤90% 10.3%, whereas in N-ioUS group a 61.2% GTR rate was obtained with a 6.4% rate of EOR≤90%. The rate of RTV1cm3. In tumors located nearby eloquent areas N-ioUS was successfully combined with cortical and subcortical mapping techniques.
A Biodegradable Magnesium Stent for Aneurysm Healing in a Rat Sidewall Aneurysm Model
Background: Endovascular devices such as stents for assisted coiling and flow diverters expand the indication for endovascular treatment of complex cerebral aneurysms. After coil engraftment or aneurysm healing, the endovascular prosthesis is potentially no longer needed. Therefore, biodegradable stents could avoid drawbacks such as risks for in-stent thrombosis and need for lifelong antiplatelet therapy. In this study, the interaction of a biodegradable magnesium stent with a healing aneurysm and with the underlying parent artery was investigated in a rat sidewall aneurysm model. As inflammatory reactions are known to compromise aneurysm healing, a special emphasis was put on the impact of the degrading endovascular foreign body on perivascular inflammation. Further, the authors studied whether how this reaction can be modulated by administrating anti-platelet and anti phlogistic medication.
Methods: Side wall aneurysms were created in male Wistar rats and the animals randomly allocated to no treatment group (n=12), biodegradable magnesium stent alone treatment group (n=12) and biodegradable magnesium stent + acetylsalicylic acid (ASA) treatment group (n=12). After a follow-up of 7 days and 28 days animals underwent fluorescence angiography, before euthanasia and macroscopic evaluation of the aneurysm and parent vessel. Aneurysms were harvested, quick-frozen and homogenized for quantitative measurements of various inflammation markers (INF-γ, TNF-α, IL1-β, Il6, TIMP-1, VEGF, MMP-9 and MMP-2).
Results: Animals treated with stents showed better aneurysm healing and faster formation of integral neointima compared to those without stents. Stent placement, however, resulted in increased loco regional intraaneurysmal inflammation reaction (i.e. p = 0.0421 for Il6). In contrast, animals treated with magnesium stents + ASA showed good and fast aneurysm healing and inflammation markers on a level comparable to those without treatment or lower (i.e. p = 0.0114 for Il1-β).
Conclusion: The use of a biodegradable magnesium stent facilitated neointima formation and intraaneurysmal thrombus organization in the rat sidewall aneurysm model. Stent induced inflammation processes were controlled by contemporaneous administration of ASA. Our results indicate that bioresorbable magnesium stents offer a promising approach for the development of future endovascular devices in aneurysm therapy.
Neointima Formation and Thrombus Organization after Coil and Stent Treatment is Mediated by Cell Migration from the Adjacent Vital Vessel Wall in Rat Sidewall Aneurysms
The biological response of endovascular intracranial aneurysm treatment is to initiate intraluminal thrombus formation and to stimulate growth of a neointima which separates the aneurysm dome from the circulation. These processes are mediated by cells, as i.e. vascular smooth muscle cells (SMC). As of yet it remains unclear if these SMC are mainly recruited from the aneurysm wall, if they origin from progenitor cells or wether they migrate from the parent artery.
In this experimental study in n=20 male Sprague Dawley rats aneurysms were transplanted on the abdominal aorta and treated with intraaneurysmal coil placement. Of them, in n=10 cases decellularized wild-type aneurysm were sutured on a green-fluorescent positive (GFP+) rat and in n=10 cases GFP+ aneurysms were sutured on wild-type rats. Additionally, in n=20 male Lewis rats aneurysm were treated with a stent. In n=10 cases of them decellularized wild-type aneurysms were sutured on GFP+ animals and in n=10 cases GFP+ aneurysms were sutured on wild-type animals. On follow-up examinations after 3, 7, 14, 21 and 28 days aneurysms were evaluated on perfusion status and tissues macroscopically and histologically examined.
Sequential arrangement over time showed progressive neointima formation with increasing neointima thickness and gradually advancing thrombus formation. Qualitative assessment of histology revealed migration of aneurysm wall cells into the thrombus. In GFP+ animals, GFP+ cells were found along the neointima, in the aneurysm wall and inside the organizing thrombus.
Neointima formation and thrombus organization are concurrent processes in aneurysm healing after endovascular treatment. Distribution of GFP+ cells in coiled and in stent treated aneurysms suggests organizing cells to origin from the adjacent vessel. These cells migrate into the aneurysm wall, into the thrombus and form the neointima.
Towards an Intelligent Robotic Pedicle Screw Placement - Evaluation of a Force-Based Controlled Drilling System
Malposition of pedicle screws – the central element of lumbothoracic spine fusion procedures – still pose a relevant risk in spine surgery. Existing robotic systems retain precisely the trajectory for screw placement, not more. So far, they comprise the same potential risk of malpositioning associated with navigated image guidance. However, robots can potentially be smart tools if equipped with sensors that provide information far beyond the haptic feedback of the surgeons.
The aim of this work was to evaluate a concept of intelligent pedicle drilling with force-based measurement to predict a screw misplacement based on information from high-resolution CT data.
We hypothesized that a sensory robotic drill bit could be located with a maximum inaccuracy of 1mm and less within the cortical borders of the lumbar spine. A robotic drilling arm equipped with a force-torque sensor was utilized. The system was able to detect the resistance while traversing the cortical and spongious bone with a drill. Subsequently, n=20 trajectories were drilled various segments of a human lumbar spine specimen. Pre- and post-experimental high-resolution CT scans of the drilled trajectories were acquired. Per each drilled trajectory, the axial force applied to the drill bit was extracted and correlated with n=1000 candidate trajectory in a 3 × 3 mm search space (resolution: 0.3 mm, angle variation: ± 2.5°, Δ0.5°).
Seventeen datasets were available for accuracy analysis. Intentionally, in 4 of 17 trajectories a medial breach was created and 7/17 trajectories a lateral breach. The remaining 6/17 trajectories were fully passed through the pedicle. The pose of the drill trajectory could be identified as accurate as 0.25±0.11 mm (n= 17), with available accuracies during lateral and medial breach to be 0.27±0.06 mm (n = 7) and 0.34±0.11 mm (n = 4) respectively. Available accuracy in the pedicle was 0.15±0.08 mm (n = 6).
The maximum inaccuracy was < 0.5 mm. This technique indicates a potentially very powerful approach that operates independently of an image-guidance model (including inherent problems of image co-registration, optical tracking, instrument calibration etc.). The highly accurate detection of a cortical bone breach represents a novel and clinically relevant safety feature. By adding sensor technologies, robots can become “smart” and lead the way to the next level of robot-assisted spine surgery.
3D high-resolution post-contrast imaging at 3T for the delineation of enhancing brain tumours: a comparison of MPRAGE with SPACE and VIBE techniques
Aims: To prospectively investigate differences between the Magnetization-Prepared-Rapid-Gradient-Echo (MPRAGE) 3D-post-contrast T1-weighted technique (1) recommended by the modified RANO criteria (2), and two other available techniques [Sampling-Perfection-with-Application-optimized-Contrasts-using-different-flip-angle-Evolutions (SPACE) (3) and Volumetric-Interpolated-Brain-Examination (VIBE) (4)], in the assessment of contrast-to-noise-ratio (CNR), total volume (TV) and margins extent delineation (MED) of brain primitive tumors (pT) and metastases, potentially amenable to surgical and/or conformal radiotherapy treatment.
Methods: Fifty-four contrast-enhancing lesions (38 pT and 16 metastases) were detected in 37 patients using 3T MRI with 1-mm MPRAGE, VIBE and SPACE sequences acquired 5 minutes after 0.1ml/kg administration of gadobutrol, in random order. Lesions CNR and TV segmentation were performed by an experienced neuroradiologist using a validated semi-automated tool (SmartBrush, Brainlab) followed by manual refinement. For each combination of sequence pairs, MED mismatch was quantified using subtraction volumetric maps of the segmented lesions. Friedman repeated measures and paired-samples Wilcoxon non-parametric tests were used to investigate between-sequences discrepancies in CNR, TV and MED subtraction volumes.
Results: In either pT and metastases, CNR was significantly higher in both SPACE and VIBE compared to MPRAGE (p<0.001 and p=0.001, respectively). Larger TVs were obtained with SPACE compared to MPRAGE in both pT (p=0.007) and metastases (p=0.003). Discrepancy in MED was also found, with SPACE significantly exceeding MPRAGE in both pT and metastases margins extent (p=0.008 and 0.01, respectively).
Conclusion: We found technique-related differences in crucial parameters for brain enhancing pT and metastases delineation, when comparing MPRAGE to SPACE (CNR, TV and MED) and to VIBE (CNR only). These findings may be relevant for treatment planning and response assessment.