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Kazuhiro Hasegawa, Ko Kitahara, Haruka Shimoda and Toshiaki Hara

S egmental instability of the lumbar spine is a widely accepted biomechanical concept. 25 The definition of instability in the clinical setting, however, is controversial. The decision to perform a spinal fusion requires evidence of segmental instability. Although radiographic evaluation of degenerative lumbar spines is extensively performed, 7–9 , 15–17 , 20 its usefulness for the diagnosis of segmental instability remains controversial because of the large range of normal motion and the significant overlap of underlying pathological conditions. 8 , 14

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Kazuhiro Hasegawa, Ko Kitahara, Toshiaki Hara, Ko Takano, Haruka Shimoda and Takao Homma

L umbar segmental instability is difficult to define. Although radiographic evaluation of degenerative lumbar spines is extensively performed, 3 , 4 , 7 , 13 , 20 , 21 , 23 , 34 its usefulness in the diagnosis of lumbar segmental instability remains controversial. Previous studies reported that flexion–extension x-ray films show a large range of normal motion with a significant overlap of underlying pathological conditions. 4 , 12 Biplanar, cineradiographic, or fluoroscopic measurements provide some additional information on the disordered motion

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Hans-Ekkehart Vitzthum, Alexander König and Volker Seifert

S tabilization following decompressive surgery of the lumbar spine is indicated only in selected cases of patients with degenerative disorders of the lumbar spine. Therefore, preoperatively, it is important to identify clearly those patients with signs of segmental instability of the lumbar spine. Open MR imaging technology allows investigators to examine the spinal column in patients during flexion—extension and rotation. Of special importance is the assessment of the relationship among soft-tissue structures, nerves, and skeletal structures, because

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Bronek M. Boszczyk, Alexandra A. Boszczyk, Andreas Korge, Andreas Grillhösl, Wolf-Dietrich Boos, Reinhard Putz, Stefan Milz and Michael Benjamin

test this hypothesis by analyzing the immunohistochemical labeling pattern of the posterior joint capsule from the zygapophysial joints studied in patients undergoing spinal fusion for L4–5 motion segment instability. Understanding the molecular load—related history in the context of our previous study on normal joints 6 should provide further insight into the biomechanical process of zygapophysial joint remodeling in degenerative spondylolisthesis. Clinical Material and Methods Surgical Specimens The posterior zygapophysial articular complex was obtained

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Peter J. Lennarson, Darin W. Smith, Paul D. Sawin, Michael M. Todd, Yutaka Sato and Vincent C. Traynelis

Object. The purpose of this study was to characterize and compare segmental cervical motion during orotracheal intubation in cadavers with and without a complete subaxial injury, as well as to examine the efficacy of commonly used stabilization techniques in limiting that motion.

Methods. Intubation procedures were performed in 10 fresh human cadavers in which cervical spines were intact and following the creation of a complete C4–5 ligamentous injury. Movement of the cervical spine during direct laryngoscopy and intubation was recorded using video fluoroscopy and examined under the following conditions: 1) without stabilization; 2) with manual in-line cervical immobilization; and 3) with Gardner—Wells traction. Subsequently, segmental angular rotation, subluxation, and distraction at the injured C4–5 level were measured from digitized frames of the recorded video fluoroscopy.

Conclusions: After complete C4–5 destabilization, the effects of attempted stabilization on distraction, angulation, and subluxation were analyzed. Immobilization effectively eliminated distraction, and diminished angulation, but increased subluxation. Traction significantly increased distraction, but decreased angular rotation and effectively eliminated subluxation. Orotracheal intubation without stabilization had intermediate results, causing less distraction than traction, less subluxation than immobilization, but increased angulation compared with either intervention.

These results are discussed in terms of both statistical and clinical significance and recommendations are made.

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Ralph Rahme, Ronald Moussa, Rabih Bou-Nassif, Joseph Maarrawi, Tony Rizk, Georges Nohra, Elie Samaha and Nabil Okais

underwent a detailed clinical evaluation at the time of follow-up, including: 1) presence of symptoms (sciatica, low-back pain, segmental instability); 2) disability level (ODI); 11 , 12 3) satisfaction (Patient Satisfaction Index); 3 , 4 , 9 and 4) work status. 13 Sciatica was defined as either persistent radicular pain or residual paresthesias causing discomfort in the affected dermatome. The presence of segmental instability was determined clinically according to the criteria of Kotilainen et al. 19 , 20 , 35 ( Table 1 ). Given the lack of consensus on a

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Jason Moore, Narayan Yoganandan, Frank A. Pintar, Jason Lifshutz and Dennis J. Maiman

the anterior longitudinal ligament, we did not expect improvements in extension. This has been borne out in the literature. Based on in vitro ALIF cage studies published in the literature, the findings range from the observation of no change to significant decreases in extension stability. 39 , 44 , 49 , 54 , 56 Patwardhan, et al., 44 have shown that segmental instability in extension significantly diminishes in the presence of compressive preload. The results of studies delineating the role of preload on the stiffness response with anterior cage instrumentation

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Nedal Hejazi

M inimally invasive techniques for lumbar disc surgery are being developed to minimize perioperative morbidity and secondary segmental instability. 1, 3, 4, 9 In cases with far-cranial or -caudal retrovertebral extruded disc herniations without an apparent superior or inferior disc level origin, partial or complete facetectomy with or without hemilaminectomy is necessary, although the risk of postoperative spinal instability is increased. 5, 7, 8 In this paper, a microsurgical infrapedicular paramedian approach is described, and clinical and long

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Kenzo Uchida, Hideaki Nakajima, Ryuichiro Sato, Takafumi Yayama, Erisa S. Mwaka, Shigeru Kobayashi and Hisatoshi Baba

With the progression of kyphosis, the mechanical stress applied to the anterior aspect of the spinal cord eventually increases. 27 In addition, dynamic forces caused by segmental instability, which is often seen at the level of kyphosis particularly in cervical flexion movement, contribute to compromised cord function. 6 , 7 , 11 , 15 , 25 , 35 , 38 Although cervical myelopathy could develop as a result of spinal cord compression with or without deformity, the effects of sagittal kyphotic deformities or mechanical stress on the development of CSM, or the reduction

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Anton V. Zaryanov, Daniel K. Park, Jad G. Khalil, Kevin C. Baker and Jeffrey S. Fischgrund

T raumatic burst fractures account for approximately 15% of all spinal injuries. 21 These fractures occur due to axial compression and varying degrees of flexion. 45 The compressive forces result in anterior and posterior cortical disruption and frequently lead to segmental instability. Multiple classification systems of thoracolumbar injuries exist; some are descriptive, while others attempt to correlate fracture pattern and treatment strategy. Nevertheless, there is still no absolute consensus on which fractures should be treated operatively and what