Comparison of Posterior Fixation Strategies for Thoracolumbar Burst Fracture: A Finite Element Study.

The management of thoracolumbar (TL) burst fractures remained challenging. Due to the complex nature of the fractured vertebrae and the lack of clinical and biomechanical evidence, currently, there was still no guideline to select the optimal posterior fixation strategy for TL burst fracture. We utilized a T10-L3 TL finite element model to simulate L1 burst fracture and four surgical constructs with one- or two-level suprajacent and infrajacent instrumentation (U1L1, U1L2, U2L1, and U2L2). This study was aimed to compare the biomechanical properties and find an optimal fixation strategy for TL burst fracture in order to minimize motion in the fractured level without exerting significant burden in the construct. Our result showed that two-level infrajacent fixation (U1L2 and U2L2) resulted in greater global motion reduction ranging from 66.0 to 87.3% compared to 32.0 to 47.3% in one-level infrajacent fixation (U1L1 and U2L1). Flexion produced the largest pathological motion in the fractured level but the differences between the constructs were small, all within 0.26 deg. Comparisons in implant stress showed that U2L1 and U2L2 had an average 25.3 and 24.8% less von Mises stress in the pedicle screws compared to U1L1 and U1L2, respectively. The construct of U2L1 had better preservation of the physiological spinal motion while providing sufficient range of motion reduction at the fractured level. We suggested that U2L1 is a good alternative to the standard long-segment fixation with better preservation of physiological motion and without an increased risk of implant failure.

Improving Image Correlation and Differentiation of 3D Endoluminal Lesions in the Air Spaces Using a Novel Target Gray Level Mapping Technique: A Preliminary Study of Its Application to Computed Tomographic Colonography and Comparison with Traditional Surface Rendering Method.

Purpose: To improve the three dimensional (3D) and two dimensional (2D) image correlation and differentiation of 3D endoluminal lesions in the traditional surface rendering (SR) computed tomographic endoscopy (CTE), a target gray level mapping (TGM) technique is developed and applied to computed tomographic colonography (CTC) in this study. Methods: A study of sixty-two various endoluminal lesions from thirty patients (13 males, 17 females; age range 31-90 years) was approved by our institutional review board and evaluated retrospectively. The endoluminal lesions were segmented using gray level threshold. The marching cubes algorithm was used to detect isosurfaces in the segmented volumetric data sets. TGM allows users to interactively apply grey level mapping (GM) to region of interest (ROI) in the 3D CTC. Radiologists conducted the clinical evaluation and the resulting data were analyzed. Results: TGM and GM are significantly superior to SR in terms of surface texture, 3D shape, the confidence of 3D to 2D, 2D to 3D image correlation, and clinical classification of endoluminal lesions (P < 0.01). The specificity and diagnostic accuracy of GM and TGM methods are significantly better than those of SR (P < 0.01). Moreover, TGM performs better than GM (specificity: 75.0-85.7% vs. 53.6-64.3%; accuracy: 88.7-93.5% vs. 77.4-83.9%). TGM is a preferable display mode for further localization and differentiation of a lesion in CTC navigation. Conclusions: Compared with only the spatial shape information in traditional SR of CTC images, the 3D shapes and gray level information of endoluminal lesions can be provided by TGM simultaneously. 3D to 2D image correlations are also increased and facilitated at the same time. TGM is less affected by adjacent colon surfaces than GM. TGM serves as a better way to improve the image correlation and differentiation of endoluminal lesions.

Adjacent disc and facet joint degeneration in young adults with low-grade spondylolytic spondylolisthesis: A magnetic resonance imaging study.

BACKGROUND/PURPOSE: Premature adjacent-level degeneration has been attributed to vertebral fusion, but spondylolisthesis has not been reported as a pathological factor responsible for the degeneration of adjacent disc and facet joint. We hypothesized that the degeneration of disc and facet joints in the adjacent levels is correlated with spondylolisthesis. METHODS: Magnetic resonance images of 35 symptomatic young adults (16-29 years old) with low-grade L5-S1 spondylolytic spondylolisthesis (Meyerding Grade 1 or 2) and 50 symptomatic young referents (20-29 years old) with L5-S1 disc herniation without spondylolisthesis were recruited to compare the differences between disc and facet-joint degenerations at the olisthetic and adjacent levels using the Mantel extension test. RESULTS: There were statistically significant degenerative changes of the discs and facet joints at the olisthetic and adjacent levels of patients with spondylolytic spondylolisthesis compared with the reference group. There is a trend that the disc and facet joints degenerate the most at the olisthetic level and become less affected at adjacent levels away from the lesion of pars defect. CONCLUSION: Low-grade spondylolytic spondylolisthesis was associated with significant degenerations of the disc and facet joints at olisthetic and adjacent levels in young adults.

Exploring the interior of 3D endoluminal lesions in the air spaces by a novel electronic biopsy technique: A preliminary study of endoluminal colon lesions.

To explore the interior of a lesion in a 3D endoluminal view, this study investigates the application of an 'electronic biopsy' (EB) technique to computed tomographic colonography (CTC) for further differentiation and 2D image correlation of endoluminal lesions in the air spaces. A retrospective study of sixty-two various endoluminal lesions from thirty patients (13 males, 17 females; age range, 31 to 90 years) was approved by our institutional review board and evaluated. The endoluminal lesions were segmented using gray-level threshold and reconstructed into isosurfaces using a marching cube algorithm. EB allows users to interactively erode and apply grey-level mapping (GM) to the surface of the region of interest (ROI) in 3D CTC. Radiologists conducted the clinical evaluation, and the resulting data were analyzed. EB significantly improves 3D gray-level presentation for evaluating the surface and inside of endoluminal lesions over that of SR, GM or target GM (TGM) (P < 0.01) with preservation of the 3D spatial effect. Moreover, 3D to 2D image correlation were achieved in any layer of the lesion using EB as did GM/TGM on the surface. The specificity and diagnostic accuracy of EB are significantly greater than those of SR (P < 0.01). These performance can be better further with GM/TGM and reach the best with EB (specificity, 89.3-92.9%; accuracy, 95.2-96.8%). EB can be used in CTC to improve the differentiation of endoluminal lesions. EB increases 3D to 2D image correlations of the lesions on or beneath the lesion surface.

Statistical validation of endophenotypes using a surrogate endpoint analytic analogue.

Endophenotypes, which involve the same biological pathways as diseases but presumably are closer to the relevant gene actions than diagnostic phenotypes, have emerged as an important concept in the genetic studies of complex diseases. In this report, we develop a formal statistical methodology for validating endophenotypes. The proposed method was motivated by the conditioning strategy used for surrogate endpoints commonly seen in clinical research. We define an endophenotype to be "a trait for which a test of null hypothesis of no genetic heritability implies the corresponding null hypothesis based on the phenotype of interest". An index, the proportion of heritability explained, is used as an operational criterion of validation. Statistical inferences on this index are also developed. Usefulness of the proposed method is demonstrated through computer simulations and a study of assessing the Continuous Performance Test as an endophenotype of the schizophrenia spectrum.

Incidental solitary knee mass as the first manifestation of hidden lung cancer.

Hypertrophic pulmonary osteoarthropathy (HPOA), also known as secondary hypertrophic osteoarthropathy, is a clinical syndrome characterized by proliferative periostitis of the long bones especially in the distal and periarticular aspects, proliferation of the synovial membranes, causing painful and swollen joints, and often with finger clubbing. It is associated with various underlying causes, including pulmonary, pleural, cardiac, abdominal and miscellaneous conditions. Its pulmonary causes include bronchogenic carcinoma, tuberculosis, pulmonary abscess, bronchiectasis, emphysema, etc. Its radiographic presentation involves periostitis in the lower extremities. We report one case that had an incidental finding of HPOA with initial complaint about an incidental solitary knee mass with painful swelling of right knee, leading to early diagnosis of occult bronchogenic carcinoma. The radiographs and magnetic resonance imaging (MRI) revealed periosteal reactions without definite intraosseous lesion. Chest radiography and CT scan disclosed an infiltrating right upper lobe lesion suspicious malignancy. Patient received right S2 segmentectomy of lung with pathological confirmation of adenocarcinoma of lung cancer. It is important for the clinician to be aware of the radiographic findings of periostitis of HPOA, which may be the clues leading to early detection of lung cancer without significant pulmonary symptoms and to avoid possible tumor progression and distant metastases.

Application of gray level mapping in computed tomographic colonography: a pilot study to compare with traditional surface rendering method for identification and differentiation of endoluminal lesions.

OBJECTIVE: In traditional surface rendering (SR) computed tomographic endoscopy, only the shape of endoluminal lesion is depicted without gray-level information unless the volume rendering technique is used. However, volume rendering technique is relatively slow and complex in terms of computation time and parameter setting. We use computed tomographic colonography (CTC) images as examples and report a new visualization technique by three-dimensional gray level mapping (GM) to better identify and differentiate endoluminal lesions. METHODS: There are 33 various endoluminal cases from 30 patients evaluated in this clinical study. These cases were segmented using gray-level threshold. The marching cube algorithm was used to detect isosurfaces in volumetric data sets. GM is applied using the surface gray level of CTC. Radiologists conducted the clinical evaluation of the SR and GM images. The Wilcoxon signed-rank test was used for data analysis. RESULTS: Clinical evaluation confirms GM is significantly superior to SR in terms of gray-level pattern and spatial shape presentation of endoluminal cases (p < 0.01) and improves the confidence of identification and clinical classification of endoluminal lesions significantly (p < 0.01). The specificity and diagnostic accuracy of GM is significantly better than those of SR in diagnostic performance evaluation (p < 0.01). CONCLUSION: GM can reduce confusion in three-dimensional CTC and well correlate CTC with sectional images by the location as well as gray-level value. Hence, GM increases identification and differentiation of endoluminal lesions, and facilitates diagnostic process. Advances in knowledge: GM significantly improves the traditional SR method by providing reliable gray-level information for the surface points and is helpful in identification and differentiation of endoluminal lesions according to their shape and density.

A three-object model for the similarity searches of chest CT images.

We propose in this paper a three-object model specifically for the archiving and retrieval of chest CT images. To calculate parameters for the model, each chest CT image needs to be processed to segment the three main objects and then the features be extracted to describe the objects' properties and relationships. In the image segmentation part, we applied the knowledge of the modality on chest CT images and modified the traditional watershed image segmentation algorithm including a four-step merging algorithm specifically for chest CT images. After segmentation, the mediastinum and two lung lobes are identified. The mediastinum object is mainly described by shape-related features while the two lung lobes are described mainly by texture features. A three-object model was exploited to describe the object features and the spatial relationship among objects. To test the capability of the three-object model to the similarity searches of chest CT images, we developed a CBIR system in which three distinct query modes were provided. They are 'searching by ARGs', 'searching by shape features of mediastinum', and 'searching by texture features of lung lobes'. The experimental results show that the three-object model demonstrates impressive power in the similarity searching of chest CT images. Among the three searching modes, the 'searching by shape features of mediastinum' and 'searching by texture features of lung lobes' modes provide user choices to search for images with high similarities in specific objects rather than in the whole images. The precision rate of either query mode is high, with an average of around 80% out of the first 30 result images are justified as similar, which is impressive in a fully automatic image query system using content features. Nevertheless, the two query modes that concentrate on distinct object features show slightly better capability in searching for similar images than the 'searching by ARGs' mode.

MR grading system of osteochondritis dissecans lesions: comparison with arthroscopy.

OBJECTIVE: To assess the diagnostic performance of combined three-dimensional (3D) gradient-echo (GRE) T1-weighted and routine MR imaging protocol for the evaluation of osteochondritis dissecans (OCD). MATERIALS AND METHODS: This prospective study was approved by our institutional review board and all patients gave informed consent. Three-dimensional GRE MR sequence was added to the routine protocol performed on 40 consecutive patients (35 men, 5 women; age range, 12-57 years; mean age, 20 years) with 17 juvenile and 24 adult OCD lesions (27 in knees; 14 in elbows) which were confirmed by arthroscopy. Two independent musculoskeletal radiologists reviewed all MR images. The OCD lesions were classified into five stages by assessing the signal intensity of fragment-bone interface and the integrity of articular cartilage on MR images. Stage-IV and -V lesions were considered as unstable. The sensitivity, specificity, accuracy, and interobserver agreement (κ statistics) were calculated. RESULTS: The sensitivity, specificity, and accuracy for detection of OCD instability were 100% (11 of 11), 100% (6 of 6), and 100% (17 of 17) in juvenile lesions; and 93% (14 of 15), 100% (9 of 9), and 96% (23 of 24) in adult lesions. The overall accuracy of MR findings in determining the staging was 90% (37 of 41) for reader 1 and 83% (34 of 41) for reader 2. Agreement between readers was substantial with a κ value of 0.75 for MR staging of OCD lesions. CONCLUSIONS: Three-dimensional GRE T1-weighted MR imaging combined with the routine sequences demonstrates excellent diagnostic capabilities in detecting unstable OCD lesions.

The in vivo biological effects of intradiscal recombinant human bone morphogenetic protein-2 on the injured intervertebral disc: an animal experiment.

STUDY DESIGN: Prospective analysis. OBJECTIVE: To investigate biologic influences of recombinant human bone morphogenetic protein (rhBMP)-2 on intervertebral discs after anular tears. SUMMARY OF BACKGROUND DATA: Treatments for intervertebral disc injury or degeneration are unsatisfactory. rhBMP-2, a high-potency osteoinductive and chondroinductive substance, is approved for use in anterior lumbar interbody fusions. rhBMP-2 stimulates the proliferation of rat disc cells and the secretion of extracellular matrix in vitro. In vivo responses in the intervertebral disc after anular tears are rarely studied. METHODS: Twenty New Zealand white rabbits received full-thickness anular tears and intradiscal injections of saline (control) and rhBMP-2 0.1 mg with and without coral grafts at L2-L3, L3-L4, and L4-L5, respectively. Three died or had infection. Therefore, 17 underwent radiography and sacrifice at 12 weeks. Spinal sections were stained with hematoxylin and eosin to examine responses to rhBMP-2. RESULTS: Radiographs revealed degenerative changes, such as disc space narrowing and irregularity, subchondral sclerosis, osteophyte formation, and hypertrophy of vertebral endplates in all groups. Degeneration was more frequent and severe with rhBMP-2 with (P < 0.01) and without (P < 0.05) coral than with saline. Two rabbits receiving rhBMP-2 and coral achieved solid interbody bony fusion. New bone formation was noted in 2 controls, in 3 animals treated with rhBMP-2, and in 4 treated with rhBMP-2 and coral. Vascularity and fibroblast proliferation increased with rhBMP-2 (n = 14) and rhBMP-2 with coral (n = 9) compared with control (n = 3; P < 0.01 and P = 0.03, respectively). Inflammatory infiltrates increased with rhBMP-2 (n = 8) compared with control (n = 2; P = 0.03). CONCLUSIONS: Degenerative changes were more frequent and severe in the groups treated with rhBMP-2 with or without coral in radiographic findings. In histopathologic findings, rhBMP-2 promoted hypervascularity and fibroblast proliferation of the intervertebral disc after an anular tear.