• Journal of Trauma and Injury
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• 제25권1호
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• pp.7-16
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• 2012

Purpose: Cervical dislocations with locked facets account for more than 50% of all cervical injuries. Thus, investigating a suitable management of cervical locked facets is important. This study examined factors of close reduction failure in traumatically locked facets of the subaxial cervical spine patients to determine suitable surgical management. Methods: We retrospectively analyzed of the case histories of 28 patients with unilateral/bilateral cervical locked facets from Nov. 2004 to Dec. 2010. Based on MRI evaluation of disc status at the injury level, we found unilateral dislocations in 9 cases, and bilateral dislocations in 19 cases, The patients were investigated for neurologic recovery, closed reduction rate, factors of the close reduction barrier, fusion rate and period, spinal alignment, and complications. Results: The closed reduction failed in 23(82%) patients. Disc herniation was an obstacle to closed reduction (p=0.015) and was more frequent in cases involving a unilateral dislocation (p=0.041). The pedicle or facet fracture was another factor, although some patients showed aggravation of neurologic symptoms, most patients had improved by the last follow up. The kyphotic angle were statistically significant (p=0.043). Sixs patient underwent anterior decompression/fusion, and 15 patients underwent circumferential fusion, and 7 patients underwent posterior fusion. All patients were fused at 3 months after surgery. The complications were 1 case of CSF leakage and 1 case of esphageal fistula, 1 case of infection. Conclusion: We recommend closed reduction be performed as soon as possible after injury to maximize the potential for neurological recovery. Patients fot whom closed reduction of the cervical locked facets have a higher incidence of anatomic obstacles to reduction, including facet fractures and disc herniation. Immediate direct open anterior reduction or circumferential fixation/fusion of locked cervical facets is recommended as a treatment of choice for traumatic locked cervical facet patients after closed reduction failure.

• Journal of Korean Neurosurgical Society
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• 제41권5호
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• pp.295-300
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• 2007

Objective : Unilateral facet dislocation of the cervical spine occurs by flexion and rotation injuries and cannot be easily reduced by axial traction. We analyzed 14 consecutive patients with unilateral facet dislocation of the cervical spine to increase knowledge about anatomical reduction of locked facet and factors for successful reduction. Methods : Fourteen patients [10 men and 4 women] with unilateral facet dislocation of the cervical spine were retrospectively analyzed. Plain X-ray, computerized tomography scan, and magnetic resonance imaging were performed. All patients underwent manual reduction and surgery with anterior interbody fusion and plate fixation. The manual reduction was performed by neck flexion and rotation to the opposite side of dislocation, followed by rotation and flexion of the head toward the side of dislocation and extension with relaxation of traction. Mean follow-up period was 17 months. The level of spine, amount of subluxation, combined facet fracture, and time from injury to initial reduction were analyzed using the data obtained from medical records. Results : Thirteen [93%] patients were reduced successfully. Immediate reduction was achieved in 7 patients but failed in 7 patients. Seven patients underwent delayed closed reduction under general anesthesia, and successful reduction was achieved in 6 patients. Only one patient with bone chips between articular facets failed to achieve anatomical reduction. Conclusion : In order to reduce the locked facet more easily and safely, we recommend manipulative traction with anterior interbody fusion and plate fixation under general anesthesia after being aware of spinal cord injury with magnetic resonance imaging.

• Journal of Korean Neurosurgical Society
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• 제63권2호
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• pp.202-209
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• 2020

Objective : The purpose of this study was to evaluate the efficacy of the anterior approach following intraoperative reduction under general anesthesia in patients with cervical facet fracture and dislocation. Methods : Twenty-three patients with single level cervical facet fracture and dislocation who were subjected to the anterior approach alone following immediate intraoperative reduction under general anesthesia from March 2013 to December 2017 were enrolled in this study. Neurological status, clinical outcome, and radiological studies were evaluated preoperatively, postoperatively, and during the follow-up period. Results : The cohort comprised 15 men and eight women with a mean age of 57 years (from 24 to 81). All patients were operated on within the first 8 hours following the injury. After gentle manual reduction or closed reduction with Gardner-Wells traction, under general anesthesia monitored by somatosensory-evoked potentials, all operations were successfully completed using the anterior approach alone except in two patients, who had a risk of over-distraction. In them, a satisfactory gentle manual reduction or closed reduction was not possible, and required open posterior reduction of the locked facets followed by anterior cervical discectomy and fusion. In one patient, screw retropulsion was observed in 1 month after surgery. There were no reduction-related complications or neurological aggravations after surgery. All patients showed evidence of stability at the instrumented level at the final follow-up (mean follow-up, 12 months). Conclusion : Anterior approach following intraoperative reduction monitored by somatosensory-evoked potentials under general anesthesia for cervical dislocation and locked facets is a relatively safe and effective alternative when cervical alignment is achieved by intraoperative reduction.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.326-336
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• 2008

A WDM-PON has been considered as an ultimate solution for access networks. However, there were many technical and practical issues for commercial deployment. These issues were solved with wavelength locked F-P LD and the WDM-PONs employing this optical source were commercialized. These WDM-PON systems have been deployed in Korea, Europe, and US. We reviewed wavelength locking technology and WDM-PON achievements. When we inject spectrum sliced broadband light into an F-P LD, the multimode output is changed to a quasi single mode. Then, we can use the single mode light for WDM signal transmission. The broad spectral gain of the semiconductor gain medium enables a color-free operation of WDM-PON, i.e., an identical ONT can be used for each user. The wavelength locking properties depend on many parameters, especially alignment of injection wavelength to a lasing mode, passband profile of AWG and front facet reflectivity of F-P LD. However, these dependencies can be reduced by proper design of the laser and the injection bandwidth. Thus, WDM-PON systems have been achieved with color-free operation.

• 한국광학회지
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• 제21권2호
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• pp.74-81
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• 2010

WDM-PON 용 저가형 광원으로 유망한 주입 잠금 패브리-페롯 레이저 다이오드의 특성 해석을 위한 모델링 방법을 제시하였다. 해석 방법으로는 시영역 대신호 모델을 이용하였으며, 계산 결과는 기존의 실험 결과와 유사한 경향을 보임을 확인하였다. 이를 토대로 특정한 파라미터를 가지는 레이저 다이오드 구조에서의 단면 반사율에 따른 동작 특성과 디튜닝, 아이 다이어그램등을 모델링 하였다. 특히 단면 반사율의 값에 따른 부모드 억제율 특성 및 디튜닝의 영향을 살펴보았으며, 주입되는 단면의 반사율이 1% 미만으로 유지되어야 안정된 특성을 얻을 수 있음을 확인하였다. 아이 다이어그램의 경우 155 Mbps 급에서는 손쉽게 아이 열림을 얻을 수 있지만, 1.25 Gbps 급에서는 레이저 다이오드의 활성층 두께 등의 파라미터를 적정화해야 적정한 아이특성을 얻을 수 있음을 보였다.