Biomedical subjects

K Abumi

Publications and source records attributed to K Abumi.

53 records · Page 3Linked to original sources

PubMed1996

A mathematical expression of three-dimensional configuration of the scoliotic spine.

Three-dimensional configuration of the scoliotic spine was mathematically expressed by a spatial curve passing through each vertebral centroid ("vertebral body line"). Three-dimensional location of the vertebral centroid was determined from digitization on the frontal and sagittal roentgenograms. Cobb angle, which is clinically used for measuring scoliosis curvature, was calculated in space to evaluate scoliosis deformity three-dimensionally. In forty-five scoliotic spines, regardless of curvature and curve patterns, the spinal configurations were excellently approximated by vertebral body lines. Vertebral body lines swerved from the sagittal plane at the end vertebrae, but aligned on a certain plane within the scoliosis region. Three-dimensional Cobb angle, which was larger than that in the frontal plane, can be utilized to evaluate the scoliosis deformity.

Adolescent↗

PubMed1995

A cineradiographic study on the lumbar disc deformation during flexion and extension of the trunk.

To reveal deformation behaviour of normal lumbar discs (L((3/4)), L((4/5)) andL(5)/S(1), the lumbar spines of eight asymptomatic volunteers were examined cineradiographically during flexion and extension of the trunk. Disc deformation could be evaluated by displacement of the superior corners of the disc, which were measured with respect to the upper surface of the adjacent lower vertebra. Furthermore the in-vivo strain distribution of each lumbar disc was analysed by the finite element method and in-vivo measurement of the disc deformation. During flexion, deformation of the lumbar disc increased rapidly after a certain delay from the start of trunk motion and reached maximum value before the finish of trunk motion. It was also confirmed that time lags were present between the onsets of disc deformation. Namely, each disc deformed not simultaneously but stepwise from the upper to the lower level with time lags during flexion. When the lower disc deformation started, the strain at the adjacent upper discs had already reached more than half of the value at full flexion. RELEVANCE: The present study revealed one of the phenomena of lumbar spinal kinematics, which will provide helpful information to clinical problems such as evaluation of spinal instability.

Journal Article↗

PubMed1994

Biomechanical analysis of cervical stabilization systems. An assessment of transpedicular screw fixation in the cervical spine.

STUDY DESIGN: The biomechanical stability of seven cervical reconstruction methods including the transpedicular screw fixation was evaluated under four instability patterns. These four modalities, based on the range and grade of instability, allowed a reproducible biomechanical assessment to establish the in vitro role of internal fixation in the cervical spine. OBJECTIVES: This study biomechanically investigated the stability of seven reconstruction methods in the cervical spine as influenced by four instability patterns and assessed whether three-column fixation for the cervical spine using transpedicular screw fixation would provide increased stability over that of conventional cervical fixation systems. METHODS: A total of 24 calf cervical spine specimens were divided into four experimental groups. The spinal constructs including seven reconstruction techniques--the posterior AO titanium reconstruction plate, Bohlman's posterior triple-wiring, transpedicular screw fixation, anterior iliac bone graft, anterior AcroMed plate, anterior AO titanium locking plate, and combined fixation with the AO anterior plate and posterior triple-wiring--were tested under four loading modes. RESULTS: Anterior plating methods provided less stability than that of posterior constructs under axial, torsional, and flexural loading conditions. Exclusive posterior procedures provided increased stability compared with the intact spine in one level fixation, however, did not sustain the torsional stability when the anterior and middle column was eliminated in two-level fixation. The stabilizing capabilities of both the combined fixation and transpedicular screw fixation were clearly demonstrated in all loading modes, however, those of the latter were superior in multilevel fixation. CONCLUSION: Front and back approaches, employing the anterior plate and posterior triple-wiring, and transpedicular screw fixation demonstrated clear biomechanical advantages when the extent of instability increased to three-column or multilevel. Three-column fixation for the cervical spine using transpedicular screw fixation offers increased stability over that of conventional cervical fixation systems, particularly in multiple level constructs.

Animals↗

PubMed1994

Reconstruction of an iliac crest defect with a bioactive ceramic prosthesis.

Between June 1987 and December 1990, an iliac crest prosthesis made of bioactive apatite- and wollastonite-containing glass ceramic (A-W.GC) was used in 60 patients for the reconstruction of the iliac crest defect after harvesting autogenous tricortical iliac bone graft. The clinical results of this prosthesis were satisfactory. No patients felt spontaneous pain in the reconstructed area, and 93% of the patients had no tenderness there. In the radiological evaluation at the final follow-up, no apparent "radiolucent clear zone" was detected at the prosthesis-iliac bone junction in 98% of the patients. Excellent new bone formation between the prosthesis and the iliac crest was also noticed in 96% of the patients. The A-W.GC iliac crest prosthesis was beneficial for reconstruction of the iliac crest defect.

Adolescent↗

PubMed1994

Monitoring the evolution of intramedullary lesions in cervical spinal cord injury. Qualitative and quantitative analysis with sequential MR imaging.

The evolution of intramedullary lesions following an acute spinal cord injury was monitored with sequential magnetic resonance (MR) imaging. Seven patients who had sustained cervical spinal cord injuries were followed up from the acute to the chronic phase of the cord injury. MR images were evaluated not only qualitatively but also quantitatively. All intramedullary lesions were quantitatively analysed by T2 values. In the qualitative analysis, the regions with hyperintensity on T2-weighted images and isointensity on T1-weighted images were consistent with the region of simple oedema or gliosis. The former gradually disappeared after the acute phase, whereas the latter remained until the chronic phase. The regions with hyperintensity on T2-weighted images and hypointensity on T1-weighted images may represent cysts filled with necrotic tissue or clear fluid, or necrosis. The evolution of these lesions was also able to be monitored quantitatively by T2 values.

Adult↗

PubMed1994

Transpedicular screw fixation for traumatic lesions of the middle and lower cervical spine: description of the techniques and preliminary report.

Thirteen patients with fractures and/or dislocations of the middle and lower cervical spine were treated by transpedicular screw fixation using the Steffee variable screw placement system. Postoperative immobilization was either not used or simplified to short-term use of a soft neck collar. Recovery of nerve function and correction of kyphotic and/or translational deformities were satisfactory. All patients had solid fusion without loss of correction at the latest follow-up. There were no neurovascular complications. It was concluded that transpedicular screw fixation is as strong a fixation procedure for the cervical spine as it is for the thoracic and lumbar spine. This surgical procedure is associated with some risks of major neurovascular injuries; however, safety is adequate if the procedure is performed by experienced surgeons using meticulous surgical techniques.

Adolescent↗

PubMed1994

Significance of Gd-DTPA-enhanced magnetic resonance imaging for lumbar disc herniation: the relationship between nerve root enhancement and clinical manifestations.

Gd-DTPA-enhanced magnetic resonance (MR) imaging can depict not only the morphology but also the pathological changes of a nerve root compressed by herniated disc. Enhanced MR imaging was performed on 115 patients treated surgically for lumbar disc herniation. Nerve root enhancement was seen in 39.1% of the patients preoperatively and in 58.7% postoperatively. Preoperative root enhancement reflects the radicular pain intensity rather than the degree of neurological deficits, whereas postoperative enhancement did not correlate with the radicular symptoms. Nerve root enhancement represents an intraneural edema in the affected nerve root. Enhanced MR imaging is a potential method for the identification of an affected nerve root in patients with a discrepancy between the level of disc herniation and neurological manifestations.

Adolescent↗

PubMed1992

Scoliosis associated with syringomyelia presenting in children.

The clinical presentations and radiological features of scoliosis accompanying syringomyelia were analyzed in 14 cases of syringomyelia associated with a in 14 cases of syringomyelia associated with a Chiari malformation in children. Scoliosis was the initial symptom in 11 out of 16 patients (64%) with syringomyelia and present in 14 (88%) at the initial examination. The scoliosis associated with syringomyelia was characterized by a higher incidence of a single curve (6 cases, 43%) and convexity to the left (7 cases, 50%) than seen in idiopathic scoliosis. The syrinx was shifted to the convex side of scoliosis on the axial section at the middle or lower thoracic level in patients with a single curve, and at the cervical or upper thoracic level in patients with a double curve. The authors think that the scoliosis develops in children as a result of damage done to the anterior horn, which innervates the muscles of the trunk, by an asymmetrically expanded syrinx.

Arnold-Chiari Malformation↗

PubMed1990

Biomechanical evaluation of lumbar spinal stability after graded facetectomies.

In an in vitro experiment using fresh human lumbar functional spinal units, the effects of the division of the posterior ligaments (consisting of the supraspinous/interspinous ligaments) and graded facetectomies were investigated. The graded facetectomies consisted of unilateral and bilateral medial facetectomies, and unilateral and bilateral total facetectomies. Six kinds of moments were applied and ranges of motion (ROM) and neutral zones (NZ) were determined three-dimensionally by stereophotogrammetric methods. Range of motion was not affected by the division of the supraspinous/interspinous ligaments for all load modes. In flexion, ROM increased slightly after unilateral medial facetectomy. In right axial rotation, ROM increased after left unilateral total facetectomy. Range of motion was not affected, even by bilateral total facetectomies, in extension and lateral bendings. This study suggested that medial facetectomy does not affect lumbar spinal stability, and conversely, total facetectomy, even created unilaterally, makes the lumbar spine unstable.

Biomechanical Phenomena↗

PubMed1990

Clinical study on stability of combined distraction and compression rod instrumentation with posterolateral fusion for unstable degenerative spondylolisthesis.

The authors examined the stability of combined distraction and compression rod instrumentation with posterolateral fusion in 40 consecutive patients with unstable degenerative spondylolisthesis. All operations were performed by floating fusion of L3-4 or L4-5 after decompression procedures. Mobility at the fused level was checked every 4 weeks after operation by the disc space angle on the functional radiographic films without brace. The average period of postoperative follow-up was 26 months. In 30 patients, no mobility was found at any time. In six patients, any mobility disappeared within 24 weeks, and in three patients, within 1 year. Pseudoarthrosis was found in one patient. The solid fusion rate was 97.5%. The values of percent slippage and slip angle were slightly improved. Lumbar lordosis was in the normal range at follow-up.

Female↗

PubMed1989

Spinal stability and intersegmental muscle forces. A biomechanical model.

The human spinal column, devoid of musculature, is incapable of carrying normal physiologic loads. In an in vitro experiment, the effect of simulated intersegmental muscle forces on spinal instability was investigated. Intact and sequentially injured fresh lumbar functional spinal units were subjected to three-dimensional biomechanical tests with increasing muscle forces. With the application of muscle forces, range of motion (ROM) increased and neutral zone (NZ) decreased in flexion loading, while both ROM and NZ decreased in extension loading. In lateral bending, ROM and NZ were unaffected by the application of the muscle forces. In axial rotation, ROM decreased significantly, while NZ decrease was statistically insignificant. It was concluded that the action of the intersegmental muscle forces is to maintain or decrease intervertebral motions after injury, with the exception of the flexion ROM, which increased with the application of muscle forces. In addition, the study suggested that Neutral Zone is a better indicator of spinal instability than Range of Motion.

Biomechanical Phenomena↗

PubMed1989

Biomechanical evaluation of spinal fixation devices. Part III. Stability provided by six spinal fixation devices and interbody bone graft.

The three-dimentional stability provided by six spinal fixation devices with or without interbody bone graft has been studied in an in vitro biomechanical model using five-vertebral (T11-L3) fresh cadaveric thoracolumbar specimens. An injury was created at T12-L1 by complete transection of the posterior elements and posterior half of the intervertebral disc, leaving the anterior half of the intervertebral disc and anterior longitudinal ligament intact. The three-dimensional rotations and translations, measures of biomechanical instabilities, were determined under physiologic loads for the intact spine and the spinal constructs, ie, injured spine plus instrumentation. The tested devices were: Harrington reverse ratchet rods (HR); Luque rectangle rod (LR); Kaneda device without transverse fixator (KD); Kaneda device with transverse fixators (KT); transpedicular external fixator (EF). In addition, stability tests were performed for KT, EF, and Harrington compression rods with interbody bone graft following a corpectomy (KTB, EFB, and HCB). The constructs were more stable than the intact spine under the four loads in the following order: flexion: EFB, HCB, EF, HR, LR, KTB, and KT; extension: EFB, LR, EF, KTB, HR, and KT; lateral bending: KTB, KT, EFB, KD, EF, HCB, and HR; and axial rotation: EFB.

Biomechanical Phenomena↗

PubMed1988

Biomechanical evaluation of spinal fixation devices: II. Stability provided by eight internal fixation devices.

The three-dimensional stability provided by eight spinal fixation devices has been studied in an in vitro biomechanical model using seven-vertebrae (T9-L3) fresh cadaveric thoracolumbar specimens. An injury was created at T12-L1 by complete transection of the posterior elements and posterior half of the intervertebral disc, leaving the anterior half of the intervertebral disc and anterior longitudinal ligament intact. The three-dimensional rotational and translational motions, measures of biomechanical instabilities, were determined under physiologic loads for the intact specimen after injury and instrumentation with each of the eight fixation devices. The tested devices were: Dunn's anterior device (DD); Harrington distraction (HD); Harrington compression (HC); Harrington distraction-compression combination (HDC); Harrington distraction with sleeves (HDS); Luque rods (LQ); Luque rectangle (LR); and Luque short rectangle (LSR). The following devices were stable under the four loads: Flexion: HC, HD, HDC, HDS, LQ, and LR; Extension: HD, HDC, HDS, LQ, and LR; Lateral Bending: LQ and LR; and Axial Rotation: none.

Biomechanical Phenomena↗

PubMed1988

Relationship between traumatic spinal canal stenosis and neurologic deficits in thoracolumbar burst fractures.

Using CT scans of 112 consecutive patients with thoracolumbar burst fractures, we investigated the relationship between traumatic spinal canal stenosis and neurologic deficits. We calculated the stenotic ratios of the area occupied by the retropulsed bony fragments to the estimated area of the original spinal canal. We also examined the shape of the narrowed canal and the disruption of spinal elements. Burst fractures having the following ratios are at significant risk of neurologic involvement: at T11 to T12 with 35% more, at L1 with 45% or more, and at L2 and below with 55% or more.

Adolescent↗

PubMed1988

[A biomechanical study on the stability of the injured thoraco-lumbar spine fixed with spinal instrumentation].

The purpose of this study was to evaluate the stabilizing effect of various types of spinal instrumentation now used for reconstruction of injured spine. Six types of moments were applied on fixed human thoracolumbar cadaveric spines with posterior and middle column injury. Stereophotogrammetry was used to evaluate the spinal movements three-dimensionally. Achievement of stabilization against axial rotation was most difficult in all kinds of instrumentations, though transpedicular external fixator and the Kaneda device with transverse fixators provided relatively good stability for this load mode. These two devices were also stable enough for other load modes. From the view point that sufficient stability should be obtained by short instrumentation area, these two forms of spinal instrumentation are optimal among those tested in this study. Regarding transpedicular external fixator and the Kaneda device with transverse fixators, the stability was reinforced with interbody bone grafting and application of compressive force on it.

Adult↗

PubMedDate not supplied

MRI of wallerian degeneration of the injured spinal cord.

OBJECTIVE: We assessed the MR appearance of wallerian degeneration following spinal cord injury. MATERIALS AND METHODS: We retrospectively reviewed the MR examinations of 13 patients with spinal cord injury. Thirty-one MR examinations were performed at various time intervals (1 day to 4 years) following injury. RESULTS: High signal intensity was observed in six patients (11 examinations) at the level of the posterior columns cephalad to the primary injury site on T2-weighted and proton density-weighted imaging at 10 week to 12 month intervals postinjury. In these six patients the posterior column was involved at the primary injury site. CONCLUSION: The abnormal intensity cephalad to the injury site is thought to represent wallerian degeneration, which should be considered in the differential diagnoses of spinal intramedullary lesions.

Adult↗

PubMedDate not supplied

Burst fractures with neurologic deficits of the thoracolumbar-lumbar spine. Results of anterior decompression and stabilization with anterior instrumentation.

Twenty-seven burst fractures with neurologic deficits of the thoracolumbar-lumbar spine were treated with an one-stage anterior operation consisting of anterior decompression through vertebrectomy, realignment and stabilization with Zielke instrumentation (12 patients), and our new anterior instrumentation (15 patients). Only two disc spaces directly related to the injury were fused. No patient showed neurologic deterioration after surgery. All 26 patients with incomplete lesions improved postoperatively, with 19 of them entering the next Frankel subgroup. The newly designed anterior instrumentation afforded enough stability to enable early ambulation with alignment and solid fusion.

Adult↗