Biomechanical evaluation of immediate stability with rectangular versus cylindrical interbody cages in stabilization of the lumbar spine

BACKGROUND: Recent cadaver studies show stability against axial rotation with a cylindrical cage is marginally superior to a rectangular cage. The purpose of this biomechanical study in cadaver spine was to evaluate the stability of a new rectangular titanium cage design, which has teeth similar to the threads of cylindrical cages to engage the endplates. METHODS: Ten motion segments (five L2-3, five L4-5) were tested. From each cadaver spine, one motion segment was fixed with a pair of cylindrical cages (BAK, Sulzer Medica) and the other with paired rectangular cages (Rotafix, Corin Spinal). Each specimen was tested in an unconstrained state, after cage introduction and after additional posterior translaminar screw fixation. The range of motion (ROM) in flexion-extension, lateral bending, and rotation was tested in a materials testing machine, with +/- 5 Nm cyclical load over 10 sec per cycle; data from the third cycle was captured for analysis. RESULTS: ROM in all directions was significantly reduced (p < 0.05) with both types of cages. There was no significant difference in reduction of ROM in flexion-extension (p = 0.6) and rotation (p = 0.92) between the two cage groups, but stability in lateral bending was marginally superior with the rectangular cages (p = 0.11). Additional posterior fixation further reduced the ROM significantly (p < 0.05) in most directions in both cage groups, but did not show any difference between the cage groups. CONCLUSIONS: There was no significant difference in immediate stability in any direction between the threaded cylindrical cage and the new design of the rectangular cage with endplate teeth

Assessment of nerve involvement in the lumbar spine: agreement between magnetic resonance imaging, physical examination and pain drawing findings

<p>Abstract</p> <p>Background</p> <p>Detection of nerve involvement originating in the spine is a primary concern in the assessment of spine symptoms. Magnetic resonance imaging (MRI) has become the diagnostic method of choice for this detection. However, the agreement between MRI and other diagnostic methods for detecting nerve involvement has not been fully evaluated. The aim of this diagnostic study was to evaluate the agreement between nerve involvement visible in MRI and findings of nerve involvement detected in a structured physical examination and a simplified pain drawing.</p> <p>Methods</p> <p>Sixty-one consecutive patients referred for MRI of the lumbar spine were - without knowledge of MRI findings - assessed for nerve involvement with a simplified pain drawing and a structured physical examination. Agreement between findings was calculated as overall agreement, the p value for McNemar's exact test, specificity, sensitivity, and positive and negative predictive values.</p> <p>Results</p> <p>MRI-visible nerve involvement was significantly less common than, and showed weak agreement with, physical examination and pain drawing findings of nerve involvement in corresponding body segments. In spine segment L4-5, where most findings of nerve involvement were detected, the mean sensitivity of MRI-visible nerve involvement to a positive neurological test in the physical examination ranged from 16-37%. The mean specificity of MRI-visible nerve involvement in the same segment ranged from 61-77%. Positive and negative predictive values of MRI-visible nerve involvement in segment L4-5 ranged from 22-78% and 28-56% respectively.</p> <p>Conclusion</p> <p>In patients with long-standing nerve root symptoms referred for lumbar MRI, MRI-visible nerve involvement significantly underestimates the presence of nerve involvement detected by a physical examination and a pain drawing. A structured physical examination and a simplified pain drawing may reveal that many patients with "MRI-invisible" lumbar symptoms need treatment aimed at nerve involvement. Factors other than present MRI-visible nerve involvement may be responsible for findings of nerve involvement in the physical examination and the pain drawing.</p

Retrospective evaluation of the validity of the Thoracolumbar Injury Classification System in 458 consecutively treated patients

BACKGROUND CONTEXT: The Thoracolumbar Injury Classification System (TLICS) system has been developed to improve injury classification and guide surgical decision-making, yet validation of this new system remains sparse. PURPOSE: This study evaluates the use of the TLICS in a large, consecutive series of patients. STUDY DESIGN/SETTING: This is a retrospective case series. PATIENT SAMPLE: A total of 458 patients treated for thoracic or lumbar spine trauma between 2000 and 2010 at a single, tertiary medical center were included in this study. OUTCOME MEASURES: American Spinal Injury Association (ASIA) status and crossover from conservative to surgical treatment were measured. METHODS: Clinical and radiological data were evaluated, classifying the injuries by ASIA status, the Magerl/AO classification, and the TLICS system. RESULTS: A total of 310 patients (67.6%) was treated conservatively (group 1) and 148 patients (32.3%) were surgically (group 2) treated. All patients in group 1 were ASIA E, except one (ASIA C). In this group, 305 patients (98%) had an AO type A fracture. The TLICS score ranged from 1 to 7 (mean 1.53, median 1). A total of 307/310 (99%) patients matched TLICS treatment recommendation (TLICS <= 4), except three with distractive injuries (TLICS 7) initially misdiagnosed. Nine patients (2.9%) were converted to surgical management. In group 2, 105 (70.9%) were ASIA E, whereas 43 (29%) had neurological deficits (ASIA A-D). One hundred and three patients (69.5%) were classified as AO type A, 36 (24.3%) as type B, and 9 (6%) as type C. The TLICS score ranged from 2 to 10 (mean 4.29, median of 2). Sixty-nine patients (46.6%) matched the TLICS recommendation; all discordant patients (53.4%) were treated for stable burst fractures (TLICS=2). No neurological complications occurred in either group. CONCLUSIONS: The TLICS recommendation matched treatment in 307/310 patients (99%) in the conservative group. However, in the surgical group, 53.4% of patients did not match TLICS recommendations, all were burst fractures without neurological injury (TLICS=2). The TLICS system can be used to effectively classify thoracolumbar injuries and guide conservative treatment. Inconsistencies, however, remain in the treatment thoracolumbar burst fractures. (C) 2013 Elsevier Inc. All rights reserved.13121760176