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Biomedical subjects

P Brinckmann

Publications and source records attributed to P Brinckmann.

At least 19 recordsLinked to original sources
PubMed2002

Sagittal plane segmental motion of the cervical spine. A new precision measurement protocol and normal motion data of healthy adults.

OBJECTIVE: (1) Precise documentation of sagittal plane segmental rotational and posteroanterior translational motion of segments C0/C1-C6/C7 of the human cervical spine from lateral radiographic views. (2) Compilation of a database describing normal motion. (3) Comparison of individual motion patterns with the normal database. DESIGN: Descriptive study based on computer-aided measurements from lateral radiographic views taken in flexion and extension. BACKGROUND: Previous studies concentrated on segmental rotational motion of the cervical spine. Normal data for translational motion were not available. Description of cervical spine motion patterns thus remained incomplete. METHODS: Based on computer-aided measurements from lateral radiographic views taken in flexion and extension, a new protocol determines rotational and translational motion for all segments (C0/C1-C6/C7) imaged on the radiographic views. Measured results are corrected for radiographic magnification and variation in stature; they are virtually uninfluenced by radiographic distortion and patient alignment errors. A database describing normal motion was compiled from 137 sets of lateral views of healthy adults taken in active flexion and extension. A specimen study as well as inter- and intra-observer studies quantify measurement errors. RESULTS: The error study demonstrated the error (SD) of a rotational motion measurement to amount to slightly less than 2 degrees. The error (SD) of a translational motion measurement amounts to less than 5% of vertebral depth; for a vertebra of 15 mm depth this corresponds to 0.7 mm. A normal database for rotational and translational motion was compiled. There was a linear relation between rotational and translational motion. This finding agrees qualitatively with results from previous studies; quantitative comparisons are not possible due to divergent definitions for translational motion. The relation between rotation and translation can be employed in individual cases to predict translational motion, in dependence on the rotation actually performed. A comparison of the rotational motion with the normal database and the difference between predicted and actual translational motion allow segmental hypo-, normal or hypermobility to be quantified. CONCLUSIONS: The new protocol measures segmental motion with high precision and corrects for radiographic distortion, variation in stature and alignment errors of patients. Thus, archive studies using existing radiographs are feasible. RELEVANCE: Flexion-extension radiographs of the cervical spine are performed to explore potential damage to the bony or ligamentous structure resulting in abnormal, segmental motion patterns. Determining rotational motion gives only an incomplete picture. The new protocol allows for precise quantification of translational motion and classification of segments as hypo- or hypermobile by comparison with normal motion data.

Adolescent↗
PubMed2002

Vertebral height, disc height, posteroanterior displacement and dens-atlas gap in the cervical spine: precision measurement protocol and normal data.

OBJECTIVE: (1) Precise measurement of vertebral height, disc height, posteroanterior displacement and dens-atlas gap from lateral radiographic views of the cervical spine. (2) Compilation of a normative database for these parameters, specifying dependence on gender and age. DESIGN: Descriptive study, based on measurements from lateral radiographic views of the cervical spine of healthy subjects. BACKGROUND: Normal data of vertebral height, disc height, posteroanterior displacement and size of the dens-atlas gap as well as their biological range of variation and potential dependence on gender and age are not available. METHODS: Based on computer-aided measurements from lateral radiographic views of the cervical spine, a new protocol determines these parameters. RESULTS: are compensated for radiographic magnification, variation in stature and the individually adopted posture of the cervical spine; they are virtually uninfluenced by radiographic distortion and patient alignment errors. A specimen study as well as inter- and intra-observer studies quantify measurement errors.Results. Employing the new protocol, vertebral height C3-C7 and disc height C2/C3-C6/C7 are measured with relative errors of 3.9% and 5.7% respectively. Posteroanterior displacement C1/C2 to C6/C7 is measured with an error of 2.8% of mean vertebral depth and the dens-atlas gap is measured with an error of <1.8% of the depth of C2. A normal database for the dimensions of cervical vertebrae and discs as well as of the sagittal plane alignment of the vertebrae within the cervical spine is compiled from 135 lateral views of healthy adults. CONCLUSIONS: Vertebral height, disc height, posteroanterior displacement and size of the dens-atlas gap are measured with high precision. Normal data are presented for the first time. RELEVANCE: The new protocol in conjunction with the normal database enables future studies detecting or monitoring morphological effects of, for example, trauma, long-term high mechanical loading, disc degeneration, rheumatoid arthritis, fusion or other surgical interventions.

Adult↗
PubMed2002

[Sagittal plane rotational and translational motion of lumbar segments with decreascd intervertebral disc height].

PURPOSE: Employing a precise measurement protocol, it was investigated whether decreased height of lumbar discs is related to an increase of sagittal plane segmental motion or to a displacement of the cranial vertebra into a retrolisthesis position. METHODS: The height of the intervertebral discs, the dorsoventral displacement of the cranial vertebra and the range of sagittal plane rotational and transitional motion were measured for all segments of the lumbar spine from flexion-extension views of 30 patients. In each patient, at least one lumbar disc exhibited a significant height decrease. The measurement was performed using a new protocol compensating for distortion in central projection, off-centre position, axial rotation and lateral tilt of the spine. Measured data on retrolisthesis position, rotational and translational motion were compared with previously compiled age- and gender-appropriate normal data. RESULTS: In the cohort investigated there was no statistically significant relation between a decrease of disc height and segmental hypermobility with respect to sagittal plane rotation or translation. There was no relation between a decrease of disc height and a displacement of the adjacent cranial vertebra into a retrolisthesis position. CONCLUSIONS: The results challenge the often postulated relation between low disc height and segmental hypermobility ("instability") and retrolisthesis position of the cranially adjacent vertebra.

Adolescent↗
PubMed2001

Height of lumbar discs measured from radiographs compared with degeneration and height classified from MR images.

The relation between height of lumbar discs (measured from lateral radiographic views) and disc degeneration (classified from MR images) deserves attention in view of the wide, often parallel or interchanged use of both methods. The time sequence of degenerative signs and decrease of disc height is controversial. To clarify the issue, this cross-sectional study documents the relation between disc degeneration and disc height in a selected cohort. Forty-three subjects were selected at random from a cohort examined for potential disc-related disease caused by long-term lifting and carrying. From each subject a lateral radiographic view of the lumbar spine as well as findings from an MR investigation of (in most cases) levels T12/L1 to L5/S1 were available; thus, n = 237 lumbar discs were available for measurement and classification. Disc height was measured from the radiographic views with a new protocol compensating for image distortion and permitting comparison with normal, age- and gender-appropriate disc height. Degeneration as well as disc height were classified twice from MR images by independent observers in a blinded fashion. Disc degeneration classified from MR images is not related to a measurable disc height loss in the first stage of degeneration, whereas progressive degeneration goes along with progressive loss of disc height, though with considerable interindividual variation. Loss of disc height classified from MR images is on average compatible with loss of disc height measured from radiographs. In individual discs, however, classification of height loss from MR images is imprecise. The first sign of disc degeneration (a moderate loss of nucleus signal) precedes disc height decrease. As degeneration progresses, disc height decreases. Disc height decrease and progress of degeneration, however, appear to be only loosely correlated.

Adult↗
PubMed1999

Do human lumbar discs reconstitute after chemonucleolysis? A 7-year follow-up study.

STUDY DESIGN: A retrospective, longitudinal study of 51 patients, covering a mean follow-up period of 81 months. OBJECTIVE: To observe the long-term temporal course of the height of human lumbar discs after chemonucleolysis. To document whether human lumbar discs reconstitute, thus characterizing the healing potential of central disc tissue. SUMMARY OF BACKGROUND DATA: Although reconstitution of disc height within some months of chemonucleolysis has been observed in animal experiments, human lumbar discs have shown no tendency to regain their initial height within 1 year of treatment. To date, there has been no report on longer follow-up periods. The different reactions of animal and human discs may be dose-related or related to differences in tissue properties, physiologic environment or in vivo loading conditions. METHODS: Using a new protocol, the heights of lumbar discs were measured from sets of lateral radiographic views of 51 patients subject to chemonucleolysis by treatment with chymopapain (doses of 4000 or 3000 picokatals [pkat]). The sets comprised a view taken before treatment, a view taken (on average) 4 months after treatment, and a view taken (on average) 81 months after treatment. In the majority of patients, untreated discs adjacent to discs treated with chemonucleolysis served as control discs. RESULTS: Shortly after injection of chymopapain, all treated discs decreased in height. The height decrease of treated discs amounted to 15.8% on average. In the subcohort treated with 4000 pkat, the loss did not reverse during the entire follow-up period; in the subcohort treated with 3000 pkat a small fraction of the lost height was regained. Untreated neighboring control discs showed a minor (3.4%) decrease in height. CONCLUSIONS: Human lumbar discs do not reconstitute after chemonucleolysis. Because the long-term temporal course of disc height in patients is in disagreement with observations from animal experiments, caution is suggested when generalizing results from animal studies to humans.

Chymopapain↗
PubMed1998

Assessment of sagittal plane segmental motion in the lumbar spine. A comparison between distortion-compensated and stereophotogrammetric roentgen analysis.

STUDY DESIGN: Sagittal plane translatory and rotatory motion was measured in 15 lumbar motion segments of 8 patients by distortion-compensated and stereophotogrammetric Roentgen analysis. OBJECTIVE: To compare measurement precision of the new distortion-compensated Roentgen analysis protocol with that of the established Roentgen stereophotogrammetric technique under realistic clinical conditions. SUMMARY OF BACKGROUND DATA: Roentgen stereophotogrammetric analysis constitutes the most precise method available to assess segmental motion. Because of the invasive nature of the procedure, however, there is interest in alternative, noninvasive protocols suitable for studying larger patient cohorts. METHODS: In 8 patients, segmental motion of 15 lumbar segments that had undergone previous spinal surgery was assessed from stereo views by using Roentgen stereophotogrammetric analysis. Sagittal plane segmental motion was assessed by distortion-compensated Roentgen analysis. Sagittal plane translatory and rotatory motion data obtained by both methods were compared. RESULTS: With respect to Roentgen stereophotogrammetric analysis, sagittal plane rotation was determined by distortion-compensated Roentgen analysis with an error (standard deviation) of 1.4 degrees and a mean difference of less than 0.05 degree. Sagittal plane translation was determined by distortion-compensated Roentgen analysis, with an error of 1.25 mm and a mean difference 0.5 mm. CONCLUSION: Measurement precision of distortion-compensated Roentgen analysis is slightly inferior to that of Roentgen stereophotogrammetric analysis but substantially higher than that of conventional protocols assessing lumbar segmental motion. If measurement precision is considered adequate and if a noninvasive technique is indicated, distortion-compensated Roentgen analysis can be used to provide reliable motion data required for epidemiologic and clinical studies.

Adult↗
PubMed1997

[The physiological pattern of lumbar intervertebral disk height].

UNLABELLED: Purpose of this study is to present a new method of quantifying objectively the height of all discs in lateral radiographs of the lumbar spine and of analysing the normal craniocaudal sequence pattern of lumbar disc heights. METHODS: The new parameter is the ventrally measured disc height corrected for the dependence on the angle of lordosis by normalisation to mean angles observed in the erect posture of healthy persons. To eliminate radiographic magnification, the corrected ventral height is related to the mean depth of the cranially adjoining vertebra. In this manner lumbar disc heights were objectively measured in young, mature and healthy persons (146 males and 65 females). The craniocaudal sequence pattern was analysed by mean values from all persons and by height differences of adjoining discs in each individual lumbar spine. RESULTS: Mean normative values demonstrated an increase in disc height between L1/L2 and L4/L5 and a constant or decreasing disc height between L4/L5 and L5/S1. However, this "physiological sequence of disc height in the statistical mean" was observed in only 36% of normal males and 55% of normal females. CONCLUSION: The radiological pattern of the "physiological sequence of lumbar disc height" leads to a relevant portion of false positive pathological results especially at L4/L5. An increase of disc height from L4/L5 to L5/S1 may be normal. The recognition of decreased disc height should be based on an abrupt change in the heights of adjoining discs and not on a deviation from a craniocaudal sequence pattern.

Adolescent↗
PubMed1996

Precision measurement of segmental motion from flexion-extension radiographs of the lumbar spine.

OBJECTIVE: To measure sagittal plane motion of lumbar vertebrae from lateral radiographic views. Previously identified factors of imprecision such as distortion in central projection, off-centre position, axial rotation, and lateral tilt of the spine were compensated. STUDY DESIGN: This study presents a new protocol to measure sagittal plane rotational and translational motion from lateral flexion-extension radiographs of the lumbar spine. BACKGROUND: Conventional methods to determine sagittal plane rotation and translation are prone to error from the distortional effects of the divergence of the radiographic beam and the measurement error inherent in constructing tangents to the contours of the vertebral body. High precision is attained by roentgen-stereophotogrammetric methods, but because of their invasive nature they can be applied only in exceptional cases. Agreement has been reached only in that measurement of sagittal plane motion from lumbar spine flexion-extension radiographs is inaccurate. Normal patterns of sagittal plane motion and the definition of what is an abnormal flexion-extension radiograph have not been settled. METHOD: Starting from an analysis of vertebral contours in the lateral view, geometric measures are identified which are virtually independent of distortion, axial rotation or lateral tilt. Applying a new protocol based on those geometric measures, the pattern of translational and rotational motion was determined from flexion-extension radiographs of 61 symptom-free, adult subjects. Measurement errors were quantified in a specimen experiment; a reproducibility study quantified inter- and intraobserver errors. RESULTS: Magnitude and sign of 'translation per degree of rotation' determined from a cohort of 61 adult subjects were very uniform for all levels of the lumbar spine. An auxiliary study evaluating a cohort of 10 healthy subjects where flexion-extension radiographs had been taken standing and side-lying showed no dependence of the rotation/translation pattern on posture. The error study demonstrated errors in angle ranging between 0.7 and 1.6 degrees and errors in displacement ranging between 1.2% and 2.4% of vertebral depth (the largest errors occurring at the L(5)/S(1) segment). Intra- and interobserver tests showed no or only negligibly small bias and an SD virtually equal to the measurement error multiplied by radical2. The relation of displacement to angle observed in the normal cohort can be used in individual cases to predict translational motion depending on the rotation actually performed. A comparison of the predicted translation (determined from normal controls) and the value actually measured allows translational hypo-, normal, or hypermobility to be quantified. Examples illustrate application of the new method in cases of normal, hypo-, and hypermobility and in the case of an instrumented spine. CONCLUSIONS: The results of this study show that precision of the measurement of rotational and translational motion can be considerably enhanced by making allowance for radiographic distortional effects and by minimizing subjective influence in the measurement procedure.

Journal Article↗
PubMed1995

Interlaminar shear stresses and laminae separation in a disc. Finite element analysis of the L3-L4 motion segment subjected to axial compressive loads.

STUDY DESIGN: This study analyzed interlaminar shear stresses across the laminae of a ligamentous L3-L4 motion segment. A three-dimensional finite element model of the motion segment was developed and its response in axial compression mode was predicted. OBJECTIVES: The contributions of "mechanical" factors in producing laminae separation in a disc are not well understood, especially when the nucleus is still gel-like in appearance (stage 1 of disc degeneration). All types of stresses are likely to contribute to laminae separation. The authors believe it is partially due to the interlaminar shear stresses at the laminae interfaces in specific regions of an intact disc because the disc is a composite structure. The effects of anular tears on the interlaminar shear stresses were also investigated. These tears can be circumferential or radial in nature, and commonly occur in the aged, degenerated disc. SUMMARY OF BACKGROUND DATA: A large number of biomechanical studies dealing with the role of the disc vis-a-vis other spinal components have been reported in the literature. The role of mechanical factors, however, in producing laminae separation, especially when the nucleus is still gel-like in appearance (stage 1 of disc degeneration), is not entirely clear. METHODS: A three-dimensional nonlinear finite element model of an intact L3-L4 lumbar motion segment, based on the use of a special type of element for the disc anulus, was created to investigate the interlaminar shear stresses in the anulus. The effects of radial "out-in," radial "in-out," and "circumferential" injuries were analyzed. Injury was modeled as element removal in the posterolateral portion of the disc. Models subjected to axial compressive loads, ranging from 200 N to 2000 N, were analyzed. In addition to the interlaminar shear stresses, disc bulge, and displacements including coupled motions were predicted. RESULTS: The theoretical disc bulge predictions for the radial in-out injury case were in agreement with the disc bulge data obtained experimentally. Displacements, disc bulge, and coupled motions increased with injury, as expected. The interlaminar shear stresses were highest in the posterolateral portions of the intact disc model. Interlaminar shear stresses, in general, increased with injury. Also, a slight increase in circumferential injury was sufficient to see a substantial increase in interlaminar shear stresses. CONCLUSIONS: The interlaminar shear stresses being higher in the posterolateral regions of the intact disc reinforces that, from clinical studies, tears originate in the posterolateral portion of the disc. The large interlaminar shear stresses, caused by asymmetry in the disc structure due to injury, along with chemical and structural changes in the disc with age, may be an important cause of further degeneration through laminae separation. This is the case for traditional composite laminates. This study points out the importance of interlaminar shear stresses to gain further understanding of the role of mechanical factors in producing disc degeneration, especially delamination of the anulus. Clinical relevance of the findings and possible relationship to the aging process are explored.

Adolescent↗
PubMed1994

A laboratory model of lumbar disc protrusion. Fissure and fragment.

Discs of 20 human lumbar motion segments from donors between 20 and 52 years of age were subjected to a procedure that effected a radial fissure of the anulus, sparing a peripheral layer of approximately 1 mm in thickness. In addition, fragmented tissue pieces that resembled those retrieved at surgery for prolapse were created in the center of the disc. The disc contour was measured under pure axial load as well as in flexion and extension. In the intact specimen, the disc contour shifts in ventral direction in flexion and in dorsal direction in extension. In the 'fissure and fragment' discs a broad-based protrusion develops dorsolaterally at the location of the fissure. The magnitude of the protrusion is independent of flexion or extension angles in the range of +/- 5 degrees. The 'fissure and fragment' discs exhibit disc prolapse at loads between 0.9 and 6.1 kN and flexion angles below 10 degrees, i.e., under loading conditions well in the physiologic range. The findings of this experiment support the hypothesis that disc prolapse--aside from the hyperflexion trauma described in the literature--has to be preceded by generation of radial fissures and tissue fragmentation within the disc. Thus, prolapse appears to be a late event during the course of a long-term degenerative process.

Adult↗
PubMed1992

An improved method of stature measurement for quantitative determination of spinal loading. Application to sitting postures and whole body vibration.

A refined procedure for measuring stature is described; this provides a reproducibility error of 0.4 mm. The procedure accommodates the natural diurnal change in stature and permits estimation of the net stature change caused by a change in spinal loading. A series of measurements done with a cohort of 20 young and middle-aged persons showed that stature decrease was related linearly to the quasi-static load on the spine. The coefficient of proportionality between load and height loss was inversely proportional to the cross-sectional area of the lumbar discs. This method was used to investigate sitting postures and whole-body vibration to demonstrate the applicability of the procedure to quantify spinal strain (and, therefore, estimate comparative loading) in applied ergonomics. Sitting invariably led to an increase in stature, regardless of the type of chair used or the posture maintained. Whole-body vibration did not induce any loss of stature. Thus, this novel approach was able to enhance understanding of spinal behavior under different loading conditions.

Adult↗
PubMed1991

Change of disc height, radial disc bulge, and intradiscal pressure from discectomy. An in vitro investigation on human lumbar discs.

Partial discectomy was done in vitro on 15 human lumbar discs from donors 20-40 years of age. The change of disc height, radial disc bulge, and intradiscal pressure was measured in relation to the mass of central disc tissue excised. Disc height decreases and radial disc bulge increases approximately in proportion with the mass of the tissue excised. At the same time, intradiscal pressure decreases. On average, removal of 1 g of disc tissue results in a height decrease of 0.8 mm and a radial bulge increase of 0.2 mm. Removal of 3 g of central disc tissue lowers the intradiscal pressure to approximately 40% of its initial value. A mechanical model is presented which explains the observed relation between the volume of material removed and the subsequent change of height, bulge, and pressure. The experimental results and the model provide insight into the rationale of disc pressurization. A high intradiscal pressure is a prerequisite for the mechanical function of the disc under physiologic conditions.

Adult↗
PubMed1989

[Experimental research on the quantitative computed tomographic prediction of the compressive strength of the thoracolumbar vertebrae].

Testing 98 motion segments we investigated the possibility of a prediction of the compressive strength of thoracolumbar vertebrae by QCT. The ultimate compressive strength can be predicted from the density of the trabecular bone and from the size of the endplates--both determined by QCT--with an error of 1 kN. The increase of compressive strength in craniocaudal direction is calculated at approximately 0.3 kN per anatomical level. This variation is due to the increase of the endplate areas.

Adult↗
PubMed1989

Prediction of the compressive strength of human lumbar vertebrae.

The compressive strength of 98 specimens of motion segments of human thoracolumbar spines was measured. In addition, the density of the trabecular bone in the midplane of the vertebrae was assessed by quantitative computed tomography (QCT); the size of the vertebral endplates was measured by CT as well. The results show that the compressive strength of thoracolumbar vertebrae can be predicted from the product of density and end-plate area, with an error of estimate of 1 kN. The data of the experiment allow for an in vivo prediction of the strength of vertebrae to quantify the risk of fracture in physically very demanding tasks, to support expert opinion in trauma cases, or to assist in therapeutic decisions in cases of severe osteoporosis.

Humans↗
PubMed1988

Prediction of the compressive strength of vertebral bodies of the lumbar spine by quantitative computed tomography.

The ultimate compressive strength of 36 thoracolumbar vertebrae was determined experimentally. In addition, the trabecular bone mineral content was measured by single energy quantitative computed tomography. The areas of fractured endplates were also determined by computed tomography. The results show that a linear relationship exists between the compressive strength and the product of bone density and endplate area. These data allow an in vivo prediction of vertebral body strength using a noninvasive method with a standard error of estimate amounting to less than 0.95 kN.

Adult↗
PubMed1986

Injury of the annulus fibrosus and disc protrusions. An in vitro investigation on human lumbar discs.

Discs of 25 specimens of human lumbar motion segments were subjected to an internal division of the annulus fibrosus, sparing only a peripheral layer 1 mm thick. Thus an attempt was made to simulate an internal disruption of the annulus caused by a traumatic episode or a degenerative process. The disc bulge that developed at the site of the injury was observed under axial loads in the physiologic load range, after axial compression fracture and after intradiscal injection. Under 1,000-N load, the bulge amounted to less than 0.5 mm; typically it increased to less than 1.0 mm after fracture. An extrusion of disc material at the site of the annulus injury was never observed. The results suggest that a radial division of the annulus is not sufficient to produce a clinically relevant disc herniation; further prerequisites are a fragmentation of the disc material and a separation from the endplates.

Adolescent↗