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Ali Kiapour, Ashutosh Khandha, Elie Massaad, Ian D. Connolly, Muhamed Hadzipasic, Ganesh M. Shankar, Vijay Goel, and John H. Shin

optimal rod diameter during posterior cervical fusion surgery, as this may have implications for adjacent-segment degeneration and deformity prevention. This study, using an ex vivo experiment, evaluates the effect of rod diameter on stability and kinematics of the cervical spine. We hypothesize that increasing the rod diameter confers greater stability across the instrumented levels but increases stressors at the adjacent levels. Methods Specimen Selection and Preparation Thirteen cervical specimens (C2–7) were prepared from fresh-frozen cadavers (mean

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Kazuhiro Hasegawa, Ko Kitahara, Haruka Shimoda, and Toshiaki Hara

( Fig. 5C ). Discussion Decompression is aimed at relieving pressure in the spinal canal, including the lateral recesses, to free the compressed nerve roots. The merit of minimally invasive lumbar decompression is that the nerves can be decompressed while preserving the facet joints and back muscles. Boden et al. 2 reported changes in segmental motion following excision of the capsule and cartilage of the facet in an ex vivo experiment using human cadavers. Decompression resulted in a slight increase in the sagittal and axial ranges of motion. Subsequent

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David D. Limbrick Jr., Stephen Lake, Michael Talcott, Benjamin Alexander, Samuel Wight, Jon T. Willie, William D. Richard, Guy M. Genin, and Eric C. Leuthardt

readings may be affected to some degree by temperature-dependent material expansion, as was observed in ex vivo experiments. While our preliminary results suggest that the effect of temperature on baric probe readings is minimal, this factor will be explored further in future experiments. While not considered in this proof-of-concept report, an issue of central importance is the accuracy, reproducibility, and reliability of baric probe measurements. This basic issue is inherently related to the readability of the indicator. In its current configuration and with cursory

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Tomohiro Kawaguchi, Atsuhiro Nakagawa, Toshiki Endo, Miki Fujimura, Yukihiko Sonoda, and Teiji Tominaga

OBJECT

Neuroendoscopic surgery allows minimally invasive surgery, but lacks effective methods to control bleeding. Water jet dissection with continuous flow has been used in liver and kidney surgery since the 1980s, and is effective for tissue manipulation with vascular preservation, but involves some potential risks, such as elevation of intracranial pressure during application in the ventricles. The authors previously reported the efficacy of the actuator-driven pulsed water jet device (ADPJ) to dissect soft tissue with vascular preservation in microscopic neurosurgery. This feasibility study investigated the use of the ADPJ to reduce the amount of water usage, leading to more safety with sustained efficacy.

METHODS

A small-diameter pulsed water jet device was developed for use with the flexible neuroendoscope. To identify the optimal conditions for the water jet, the flow rate, water pressure, and distance between the nozzle and target were analyzed in an in vitro study by using a gelatin brain phantom. A ventricle model was used to monitor the internal pressure and temperature. For ex vivo experiments the porcine brain was harvested and ventricle walls were exposed, and subsequently immersed into physiological saline. For in vivo experiments the cortex was microsurgically resected to make the small cortico-ventricle window, and then the endoscope was introduced to dissect ventricle walls.

RESULTS

In the in vitro experiments, water pressure was approximately 6.5 bar at 0.5 mm from the ADPJ nozzle and was maintained at 1 mm, but dropped rapidly toward 50% at 2 mm, and became 10% at 3.5 mm. The ADPJ required less water to achieve the same dissection depth compared with the continuous-flow water jet. With the ventricle model, the internal pressure and temperature were well controlled at the baseline, with open water drainage. These results indicated that the ADPJ can be safely applied within the ventricles. The ADPJ was introduced into a flexible endoscope and the ventricle walls were dissected in both the ex vivo and in vivo conditions. The ventricle wall was dissected without obscuring the view, and the vascular structures were anatomically preserved under direct application. Histological examination revealed that both the vessels on the ventricle wall and the fine vessels in the parenchyma were preserved.

CONCLUSIONS

The ADPJ can safely and effectively dissect the ventricle wall, with vascular preservation in immersed conditions. To achieve the optimal result of tissue dissection with minimal surgical risk, the ADPJ is a potential device for neuroendoscopic surgery of the ventricles.

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Manabu Kinoshita, Mai Taniguchi, Masatoshi Takagaki, Nobuhisa Seike, Naoya Hashimoto, and Toshiki Yoshimine

protective function and to reduce neuronal tissue damage when removing patties from the surgical field. In this study, a thick neurological patty was developed to meet the above-mentioned demands while preserving radiographic detectability. In vitro and ex vivo experiments were performed to objectively assess the improved functionality of and the initial clinical experience with this patty during neurosurgical operations. Methods Neurosurgical Patties Two types of neurosurgical patties were assessed in this study. The control patty was the conventional, 0.5-mm

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Robin Hartman, Salavat Aglyamov, Douglas J. Fox Jr., , and Stanislav Emelianov

at a depth of 18 mm (the geometric focus of the 15-MHz transducer), and maximum imaging depth was set to 22 mm. The images were 17 mm wide in the lateral direction with 16 A-lines per millimeter. Five independent image sets were acquired for each of the 5 programmed flow rates. In the ex vivo experiment, a 21-MHz linear array transducer was used with transmit power set to 5%. Images were collected at 25 frames per second, with the center of the catheter positioned at a depth of 15 mm (the geometric focus of the 21-MHz transducer) and maximum imaging depth set to 30

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Damon DePaoli, Laurent Goetz, Dave Gagnon, Gabriel Maranon, Michel Prud’homme, Léo Cantin, Martin Parent, and Daniel C. Côté

used in other research protocols wherein the head and neuroanatomy of the specimen were unaltered; the surgery was performed on these heads within 24 hours of euthanasia. For both the in vivo and ex vivo experiments, the heads were placed in a custom-designed stereotactic apparatus that allowed for pre-, intra, and postoperative radiography. After craniotomy, a radiopaque solution (2 × 0.4 mL of a 65% iohexol solution, Omnipaque, GE Healthcare) was injected through a microsyringe into the right lateral ventricle for ventriculography. Lateral and frontal radiographs

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Thomas L. Ellis, Paulo A. Garcia, John H. Rossmeisl Jr., Natalia Henao-Guerrero, John Robertson, and Rafael V. Davalos

configuration between the energized and grounded electrodes. Values for each dog are given in Table 1 . The voltage and pulse parameters were determined from the literature and from ex vivo experiments on canine brain. 1 , 15 , 29 , 39 Using these parameters, the charge delivered during this study was typical of that used in humans during electroconvulsive therapy. 26 Dogs 1, 2, and 3 were treated with 1600, 1000, and 500 V, respectively, to assess whether lower voltages could still produce neuronal ablation. TABLE 1: Pulse parameters used in NTIRE brain treatment

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Patrick C. Reid, Simon Morr, and Michael G. Kaiser

, 83 Interbody Device Materials Interbody device materials vary. Metals include titanium, stainless steel, and cobalt chromium. Plastics include polyetheretherketone (PEEK) and carbon fiber, and carbon fiber–reinforced PEEK (CFRP). All solid metal implants have an elastic modulus that is more than 13 times as strong as cancellous bone. PEEK is closest to cancellous bone, and CFRP is closest to cortical bone. 102 Microscopic titanium surface roughness increases osteogenic cell differentiation factors in ex vivo experiments. Nanometric roughening of the titanium