Takahiro Iida

Effects of aging and spinal degeneration on mechanical properties of lumbar supraspinous and interspinous ligaments

BACKGROUND CONTEXT The effects of aging and spinal degeneration on the mechanical properties of spinal ligaments are still unknown, although there have been several studies demonstrating those of normal spinal ligaments. PURPOSE To investigate the mechanical properties of the human posterior spinal ligaments in human lumbar spine, and their relation to age and spinal degeneration parameters. STUDY DESIGN/SETTING Destructive uniaxial tensile tests were performed on the human supraspinous and interspinous ligaments at L4-5 level. Their mechanical properties were compared with age and spinal degeneration using several imaging modalities. PATIENT SAMPLE Twenty-four patients with lumbar degenerative diseases on whom posterior surgeries were performed, with the age ranging from 18 to 85 years. OUTCOME MEASURES The ultimate load and elastic stiffness as structural properties, the degree of disc degeneration, range of segmental motion, the disc height, disc space narrowing ratio and degree of facet degeneration as the parameters of spinal degeneration. METHODS Twenty-four supraspinous and interspinous ligaments at the L4-5 level were obtained from posterior surgeries of patients with lumbar degenerative disease. The mechanical tests of bone-ligament-bone complexes were performed in a uniaxial tensile fashion with a specially designed clamp device. The ultimate load and elastic stiffness were calculated as structural properties. The degree of disc degeneration, range of segmental motion, the disc height, disc space narrowing ratio and degree of facet degeneration were examined by using radiographs, computed tomography and magnetic resonance imaging. RESULTS The average and SD value of ultimate load, elastic stiffness, tensile strength and elastic modulus were 203+/-102.9 N, 60.6+/-36.7 N/mm, 1.2+/-0.6 Mpa and 3.3+/-2.1 Mpa, respectively. A significant negative correlation was found between age and tensile strength (p= 0.02). The specimens with facet degeneration showed lower values in tensile strength and elastic modulus than those without facet degeneration (p<0.04). However, no correlation was found between disc-related parameters and tensile strength. CONCLUSIONS The mechanical strength of human lumbar posterior spinal ligaments decreases with age and facet degeneration, particularly in the ligament substance.

A description of temporal and spatial variability in the Bering Sea spring phytoplankton blooms (1997-1999) using satelite multi-sensor remote sensing

Abstract The Bering Sea is well known as a highly productive marginal sea. The objectives of this study were to clarify the interannual variability of spring bloom dynamics of the Bering Sea and to describe the spatial variability of this highly productive area using satellite multi-sensor remote sensing. We used multi-sensor remote sensing data sets of ocean color (OCTS and SeaWiFS), sea surface temperature (AVHRR), sea ice (SSM/I) and sea wind (SSM/I) to understand the complexity of the Bering Sea ecosystem. Phytoplankton biomass depends on the timing of sea ice melting and tends to increase when the melting is delayed. Wind stress is one of the important factors controlling the timing of the spring bloom. In 1997 and 1998, the east–west distribution of phytoplankton biomass exhibited a seesaw pattern, either high in west and low in east or low in west and high in east. We hypothesize that this seesaw pattern results from changes in the position and intensity of the Aleutian Low during spring and its relation to the El Nino–La Nina phenomena. During the El Nino period of 1998, the Aleutian Low shifted to the east of its normal position, and weak wind stresses facilitated the development of stratification and enhancement of spring bloom in the west. Conversely, when the Aleutian Low moved over into the western region in spring 1997, the same situation occurred in the east. Thus, the movements of the Aleutian Low promote a west-east seesaw pattern of sea surface wind stress, and consequently a corresponding seesaw pattern in phytoplankton biomass resulting from the subsequent variations in the depth of the mixed layer.

Reduction and fixation of sacroiliac joint dislocation by the combined use of S1 pedicle screws and the Galveston technique

Study Design. This retrospective study was designed to analyze the results of the treatment with S1 pedicle screws and the Galveston technique of seven patients with sacroiliac dislocation. Objectives. To evaluate the effectiveness of the combined use of S1 pedicle screws and the Galveston technique for the treatment of sacroiliac dislocation. Summary of Background Data. Although several procedures for internal fixation of sacroiliac dislocation have been reported, there have been no reports discussing surgical treatment of sacroiliac dislocation by the combined use of S1 pedicle screws and the Galveston technique. Methods. Seven patients with sacroiliac dislocation were treated with pedicle screws of S1 and iliac rod according to the Galveston technique. In the seven patients, the dislocation was associated with vertical displacement of the sacroiliac joint and rotational deformity of the pelvic ring. They were classified into Type-C pelvic disruption according to the Tile’s classification. Three patients with disruption of the symphysis pubis underwent additional fixation of the symphysis using a dynamic compression plate. The remaining four patients were treated by the posterior procedure alone. Results. The vertical displacement was completely reduced in five patients, and the rotational deformity was completely corrected in four patients. The reduction was maintained at the time of the final follow-up evaluation. There were no perioperative complications with the exception of late infection in one patient. Conclusions. The combined use of S1 pedicle screws and the Galveston technique provided immediate stability and sufficient reduction for sacroiliac dislocation in seven patients in this study. This hybrid internal fixation procedure is useful for reduction and fixation of sacroiliac dislocation associated with the vertical and rotational instability of the pelvic ring.

Temporal and spatial variability of coccolithophore blooms in the eastern Bering Sea, 1998-2001

Abstract In the late summer of 1997, aquamarine waters, resulting from a massive bloom of coccolithophore algae, covered most of the continental shelf of the eastern Bering Sea. This was the first such event recorded in the area, but since then, coccolithophore blooms have been common. The objectives of this study were first to determine the threshold value of the Sea Wide Field-of-view Sensor (SeaWiFS) coccolithophore algorithm using a comparison of satellite and ship-based optical observations, and second to analyze temporal and spatial variability using SeaWiFS images of the coccolithophore blooms in the Bering Sea from 1998 to 2001. In late July 1998 and 2000, we made bio-optical measurements of the coccolithophore blooms, which were composed of Emiliania huxleyi. In situ measurements of water leaving radiance (nLw) at characteristic wavelengths yielded values that differed from the standard NASA coccolithophore values. We therefore defined new threshold values for the mask and applied it to a time series of SeaWiFS images from the Bering Sea. Generally, the coccolithophore bloom began in February each year, as melting began along the edge of the sea ice, and then expanded northward. The bloom reached its peak in April, and then from May through August the area covered by the bloom dwindled in size. However, its area increased again in September. Throughout the study period, the blooms were located at depths of 20 to 100 m. There was annual and seasonal variability in the area affected by the coccolithophore bloom. There were large blooms in 1998 and 2000, whereas in 1999 and 2001 the area affected was smaller. These differences might be related to sea surface temperature (SST), since the largest blooms occurred in the warmest years.

Minimum 20 Years Long-term Clinical Outcome After Spinal Fusion and Instrumentation for Scoliosis: Comparison of the SRS-22 Patient Questionnaire With That in Nonscoliosis Group.

Study Design. A retrospective minimum 20-year follow-up study using 4 standard self-administered questionnaires, one of which, the SRS-22 was also administered to control groups. Objective. To evaluate long-term postoperative pain and other clinical outcomes of scoliosis correction and fusion surgery with Harrington instrumentation using Moe square-ended rods for better preservation of sagittal alignment. Summary of Background Data. Only a few long-term outcome studies have used standardized and validated self-administered tools, and no studies have established SRS-22 control data within their own population. There is no previous minimum 20-year follow-up evaluation after correction surgery preserving thoracic kyphosis and lumbar lordosis. Methods. Of 86 consecutive patients who underwent instrumentation surgery for scoliosis by a single surgeon, 61 patients participated using Japanese Orthopaedic Association, Roland-Morris Disability Questionnaire, Oswestry Disability Index, and Scoliosis Research Society (SRS-22) questionnaires and 51 patients were included in this study. Results were analyzed for pain and other clinical outcomes. A total of 771 hospital employees were sent SRS-22 questionnaires. A total of 763 responded, resulting in 2 control groups composed of nonscoliosis and untreated mild scoliosis controls of the same culture and language as the long-term follow-up group. Results. The prevalence of continuous low back pain was about 15%. Average Japanese Orthopaedic Association, Oswestry Disability Index, and Roland-Morris Disability Questionnaire scores at follow-up were 25 points, 7.3%, and 1.6, respectively. The average SRS-22 scores were 4.2 (function), 4.3 (pain), 3.7 (self-image), and 3.9 (mental health) for the postoperative follow-up group compared with 4.5 (function), 4.3 (pain), 3.5 (self-image), and 3.5 (mental health) for the nonscoliosis controls. Conclusion. Improved preservation of normal sagittal alignment resulted in a prevalence of low back pain comparable with the age-matched general population. Moreover, SRS-22 results for self-image and mental health were positive compared with the controls, possibly reflecting the surgeons emphases on mental health and management of patient expectations. Level of Evidence: 4

Long-Term Trends of Nutrients and Apparent Oxygen Utilization South of the Polar Front in Southern Ocean Intermediate Water from 1965 to 2008

The variation of nutrients over decadal timescales south of the polar front in the Southern Ocean is poorly known because of a lack of continuous observational data in this area. We examined data from long-term continuous hydrographic monitoring of 43 years (1965–2008) in the Indian sector of the Southern Ocean, via the resupply of Antarctic stations under the Japanese Antarctic Research Expedition and Australian Antarctic Research Expedition. We found significant increasing trends in phosphate and nitrate, and a decreasing trend in apparent oxygen utilization (AOU) in intermediate water (neutral density = 27.8–28.1 kgm−3) south of the polar front. The rates of phosphate and nitrate increase are 0.004 µmol yr−1 and 0.02 µmol yr−1, respectively. The rate of decline of AOU was 0.32 µmol yr−1. One reason for this phosphate and nitrate increase and AOU decline is reduced horizontal advection of North Atlantic Deep Water, which is characterized by low nutrients and high AOU. The relationship between climate change and nutrient variability remains obscure, emphasizing the importance of long-term monitoring.

Clinical outcomes of combined anterior and posterior spinal fusion for dystrophic thoracolumbar spinal deformities of neurofibromatosis-1: fate of nonvascularized anterior fibular strut grafts.

Study Design. Retrospective study. Objective. To analyze the clinical outcomes of anterior and posterior spinal fusion (APSF) using a fibular strut autograft (FSAG) and to investigate the morphological changes in the reconstructed spinal column of dystrophic deformities in neurofibromatosis (NF)-1. Summary of Background Data. APSF is desirable for dystrophic deformities in NF-1 with more than 50° of dystrophic kyphosis. There are few reports regarding the clinical outcomes of APSF in which the morphological changes over time of the anterior strut graft have been investigated. Methods. The clinical and radiographic outcomes of APSF with FSAG were investigated in 10 consecutive patients with dystrophic deformity in NF-1. For qualitative and quantitative analyses, the chronological changes in the FSAG configuration, length, and diameter were evaluated. Results. The mean follow-up period was 9 years, 9 months (range, 1–30 years). Graft bone erosion and postoperative curve progression were not observed in any patient. In quantitative analyses of the anterior strut, the mean ratio of the latest and immediately postoperative FSAG lengths was 0.98 (0.93–1.09). The mean central/peripheral ratios of the FSAG diameter (central portion/[upper end + lower end]/2) were 1.02 (0.92–1.10) immediately after surgery, and 1.01 (0.92–1.07) at the latest follow-up, with no significant change between these 2 time points (P = 0.937). The mean preoperative cross-sectional area of the apical vertebral body and its mean virtual cross-sectional area at the final follow-up were 3.80 (1.83–5.43) and 4.87 (2.46–7.00) cm2, respectively, with a significant difference between these 2 parameters (P = 0.0078). The mean final/preoperative ratio was 1.31 (1.10–1.43). Conclusion. APSF with FSAG for dystrophic deformity in NF-1 successfully reconstructed a reliable spinal column with a rich bone stock. The FSAG and surrounding vertebral bodies were free from postoperative erosion due to dystrophic changes and maintained their stability for a long time.

Influence of Sea Ice Crack Formation on the Spatial Distribution of Nutrients and Microalgae in Flooded Antarctic Multiyear Ice

Cracks are common and natural features of sea ice formed in the polar oceans. In this study, a sea ice crack in flooded, multiyear, land-fast Antarctic sea ice was examined to assess its influence on biological productivity and the transport of nutrients and microalgae into the upper layers of neighboring sea ice. The water inside the crack and the surrounding host ice were characterized by a strong discoloration (brown color), an indicator of a massive algal bloom. Salinity and oxygen isotopic ratio measurements indicated that 64–84% of the crack water consisted of snow meltwater supplied during the melt season. Measurements of nutrient and chlorophyll a concentrations within the slush layer pool (the flooded layer at the snow-ice interface) revealed the intrusion of water from the crack, likely forced by mixing with underlying seawater during the tidal cycle. Our results suggest that sea ice crack formation provides conditions favorable for algal blooms by directly exposing the crack water to sunlight and supplying nutrients from the under-ice water. Subsequently, constituents of the crack water modified by biological activity were transported into the upper layer of the flooded sea ice. They were then preserved in the multiyear ice column formed by upward growth of sea ice caused by snow ice formation in areas of significant snow accumulation. Plain Language Summary Formation of cracks in sea ice affects the environment associated with biological production and biogeochemical cycling in the surface ocean of sea ice systems. Because cracks are likely to form frequently within the sea ice during the season of ice melting and ice breaking, the contributions of cracks to biological production and biogeochemical cycling may be significant in ice-covered oceans. In the future, the melting of sea ice in polar oceans will strongly affect the output of biogeochemical parameters trapped within sea ice and their use in primary and secondary production within surface oceans. In the case of multiyear, land-fast ice, biogeochemical parameters that accumulate within the ice would be discharged abruptly to ocean surface waters when the multiyear ice breaks up.

Phytoplankton distribution as observed from bio-optical drifters and SeaWiFS images in the Bering Sea green belt

Bering Sea green belt is characterized by high productive region, with interactions of cyclonic and anti-cyclonic eddies. To study temporal and spatial variability of phytoplankton, we deployed two bio-optical drifters in a clockwise eddy in 2001 and 2002. The drifters were equipped with a spectroradiometer to measure upwelling radiance as same as Sea Wide Field-of-view Sensor (SeaWiFS) wavelength. SeaWiFS images were employed to monitor the spatial pattern of chlorophyll-a (chl-a). The drifter also measured sea surface temperature (SST). We compared SST with TOPEX/POSEIDON sea surface anomaly data and analyzed time and scale correlation of SST and phytoplankton distribution in some eddies. In 2001, a clockwise eddy trapped the drifter for 10 days. It represented relatively high chl-a concentration (about 1.0 mg m-3) and low SST (about 8.5°C). After that it drifted to the Bering Sea slope current region along the shelf edge, and observed among 20 days. In 2002 we deployed a drifter in center of clockwise eddy, it was staying in this eddy for 14 days. There represented relatively low chl-a concentration (about 0.4 mg m-3) and high SST (about 9.5°C). After that it drifted along Bering slope current similarly. The phytoplankton distribution was deferent from two years in spite of same kind of anti-cyclonic eddy. These deferent might be depending on deference of eddys life stage.