Midsagittal Line Research Articles

A Study of the Relationship of the Superior Vena Cava to the Bony Landmarks of the Sternum in the Supine Adult: Implications for Magnetic Guidance Systems

This study was a retrospective investigation of computed tomography (CT) images of an Australian adult hospital population. These images were used to evaluate the spatial relationships of the superior vena cava (SVC) to the midsagittal line, the sternal paracoronal plane, and commonly used landmarks of the sternum. Consistent relationships were found between the long axis of the SVC and both the midsagittal line and sternal paracoronal plane. When the sternal paracoronal plane was used as the plane of reference, the angle of Louis was found to approximate the SVC in 99.5% of cases, and the right 2nd intercostal space approximated the SVC in 94% of cases. Constraints on the use of landmarks are discussed with regard to magnetic guidance systems for catheter tracking.

Biomechanical analysis of differing pedicle screw insertion angles

Pedicle screw fixation to stabilize lumbar spinal fusion has become the gold standard for posterior stabilization. A significant percentage of surgical candidates are classified as obese or morbidly obese. For these patients, the depth of the incisions and soft tissue makes it extremely difficult to insert pedicle screws along the pedicle axis. As such, the pedicle screws can only be inserted in a much more sagittal axis. However, biomechanical stability of the angled screw insertion has been controversial. We hypothesized that the straight or parallel screw was a more stable construct compared to the angled or axially inserted screw when subjected to caudal cyclic loading. We obtained 12 fresh frozen lumbar vertebrae from L3 to L5 from five cadavers. Schantz screws (6.0 mm) were inserted into each pedicle, one angled and along the axis of the pedicle and the other parallel to the spinous process. Fluoroscopic imaging was used to guide insertion. Each screw was then subjected to caudal cyclic loads of 50 N for 2000 cycles at 2 Hz. Analysis of initial damage, initial rate of damage, and total damage during cyclic loading was undertaken. Average total fatigue damage for straight screws measured 0.398+/-0.38 mm, and 0.689+/-0.96 mm for angled screws. Statistical analysis for total fatigue damage ratio of angled to straight screws revealed that a significant stability was achieved in straight-screw construct (P<0.03). This study showed that straight screw insertion results in a more stable pedicle-screw construct. The angled screw insertion technique resulted in more scattered values of damage indicating that the outcome from the angled screw fixation is less predictable. This validates the use of this technique to implant pedicle screws across the axis of the pedicle (parallel to the mid sagittal line) rather than along the axis, and has broad implications in instrumented posterior lumbar spinal surgery.

The Morphometric Study for the Rolandic Fissure

Objective : The purpose of this study was to characterize the Rolandic fissure(Rf) and was to identify the Rf using the surface bony landmarks which can be usually exposed on craniotomy. Methods : After morphological evaluation of the Rfs using 21 Korean adult formalin fixed cadavers, craniometric measurement was carried out from the surface bony landmarks of nasion, glabella, bregma, and lambda. Results : The Rfs of both hemispheres did not show the mirror image. The Rfs ran forward and downward toward the sylvian fissure keeping the mean angle of 67°from mid-sagittal line as elongated S-shape in left and the elongated reverse S-shape in right hemisphere. Connections between the Rf and the longitudinal fissure and between the Rf and the sylvian fissure were found in 3 (7.1%) and 2 (4.8%) of 42 hemispheres, respectively. Most Rfs extended superiorly to 2-3mm lateral to the most superomedial surface of hemispheres and extended inferiorly to 3-5mm superior to the sylvian fissures. The mean distances from the nasion, glabella, bregma, and lambda to the most superomedial aspect of the Rf were 18.8±0.9cm, 16.6 ±0.8cm, 5.2±0.6cm, and 6.9±1.0cm, respectively. The mean distance measured between the Rf and the nasion using traditional method was 18.4±0.6cm. Conclusion : The distance between the Rf and the nasion roughly correspond within the range of mean 4 mm compared with that measured by the traditional measurement. These data may be more helpful to delineate the Rf after the placement of drapes for craniotomy.

Long bone fracture reduction using a fluoroscopy-based navigation system: A feasibility and accuracy study

Objective: Long bone fracture reduction during intramedullary nailing can result in a small but significant rate of angular and rotational malalignment, which can in turn lead to long-term morbidity. Current techniques for intraoperative reduction rely heavily on fluoroscopy, and their reproducibility can be limited. We suggest that fluoroscopy-based navigation may improve the precision of long bone fracture reduction and reduce radiation exposure.Methods: A cadaveric tibia was stripped of soft tissues and fractured at its midline. The ends were then cemented to two mobile brackets within a fracture/deformity simulator. Optical trackers were drilled into each fragment. Radiographs were obtained including AP and lateral views of the proximal and distal ends of the bone as well as the fracture site. These radiographs were stored in the computer navigation system. Fracture reduction was performed using a fluoroscopy-based navigation system with virtual intraoperative planning software. The system used 4 sets of lines drawn by the surgeon on the fluoroscopic AP and lateral images. While navigating the reduction of the fracture these lines aligned together, providing graphic and numerical descriptions of the reduction. The lines included the anatomic axis of the bone, the matching of the fracture lines, the short segment anatomic axis (near the fracture site), and the AP mid-sagittal joint line (MSJL) of both the plateau and the plafond. Anatomic reduction was then performed and the computer assessment of the angulation and translation of the fragments was recorded. Each stage was repeated 25 times for each set of lines. For the control group the surface of the bone was tracked using an optical probe.Results: The accuracy of the system varied according to the planning method. The most accurate technique was matching of the fracture lines, which yielded 2.68 ± 1.18 mm of translation and 2.5 ± 1.27° of angulation. The next most accurate method was using the short segment anatomic axis, followed by using the anatomic axis method. The control group was the most accurate (1.78 ± 0.67 mm translation, 1.58 ± 0.97° angulation). The AP MSJL yielded errors greater than 10°.Conclusions: Fluoroscopy-based navigation is sufficiently accurate for long bone fracture reduction, potentially increasing angular and translational accuracy while reducing the amount of intraoperative fluoroscopy. Navigation may improve the outcome of treatment of a long bone fracture by better restoring the normal mechanical axis of the limb in a less-invasive closed manner.

Anterior retropharyngeal fixation C1-2 for stabilization of atlantoaxial instabilities: study of feasibility, technical description and preliminary results

Posterior transarticular screw fixation C1-2 with the Magerl technique is a challenging procedure for stabilization of atlantoaxial instabilities. Although its high primary stability favoured it to sublaminar wire-based techniques, the close merging of the vertebral artery (VA) and its violation during screw passage inside the axis emphasizes its potential risk. Also, posterior approach to the upper cervical spine produces extensive, as well as traumatic soft-tissue stripping. In comparison, anterior transarticular screw fixation C1-2 is an atraumatic technique, but has been neglected in the literature, even though promising results are published and lectured to date. In 2004, anterior screw fixation C1-2 was introduced in our department for the treatment of atlantoaxial instabilities. As it showed convincing results, its general anatomic feasibility was worked up. The distance between mid-sagittal line of C2 and medial border of the VA groove resembles the most important anatomic landmark in anterior transarticular screw fixation C1-2. Therefore, CT based measurements on 42 healthy specimens without pathology of the cervical spine were performed. Our data are compiled in an extended collection of anatomic landmarks relevant for anterior transarticular screw fixation C1-2. Based on anatomic findings, the technique and its feasibility in daily clinical work is depicted and discussed on our preliminary results in seven patients.

Effect of the Background on the Disparity-Induced Ramp Vergence Response in Humans

Purpose: Our purpose was to investigate the changes in the dynamic property of vergence eye movements caused by changes in the co-existing stationary background in the central visual field. Methods: Disparity-driven target movement was presented virtually by a head-mounted liquid-crystal display. Two targets were used: a bar-shaped target that moved between 2 and 0.5 m along the mid-sagittal line at a speed of 50 cm/s (vergence target) and a background image of a cross-shaped target that stayed at a distance of 2 m (background target). Eight normal subjects participated in the experiments. The subject was asked to follow the vergence target while the configuration of the background target was randomly changed among four conditions in each experiment: the length (experiment 1) or the width (experiment 2) of the horizontal and vertical lines composing the cross of the background target was each randomly changed among four conditions. A limbus tracker was used to measure eye movements. Results: In experiment 1, there was a negative correlation between the amplitude of the vergence eye movements and the lengths of the lines of the cross in each of five subjects (mean r = 0.018, n = 48 in each subject). Similarly, in experiment 2, there was a negative correlation between the amplitude of the vergence eye movements and the width of the lines of the cross in each of 8 subjects (mean r = –0.12, n = 48 in each subject). Conclusion: The vergence response to a target object significantly differs depending on the texture of background objects on the visual axis.

A vocal-tract model of American English /l/.

The production of the lateral sounds involves airflow paths around the tongue produced by the laterally inward movement of the tongue toward the midsagittal plane. If contact is made with the palate, a closure is formed in the flow path along the midsagittal line. The effects of the lateral channels on the sound spectrum are not clear. In this study, a vocal-tract model with parallel lateral channels and a supralingual cavity was developed. Analysis shows that the lateral channels with dimensions derived from magnetic resonance images of an American English /l/ are able to produce a pole-zero pair in the frequency range of 2-5 kHz. This pole-zero pair, together with an additional pole-zero pair due to the supralingual cavity, results in a low-amplitude and relatively flat spectral shape in the F3-F5 frequency region of the /l/ sound spectrum.

Finite element analysis of airflow in the vocal tract with lateral channels

Lateral channels are airflow paths around the tongue produced by the laterally inward movement of the tongue toward the midsagittal plane during American English /l/ sound production. If contact is made with the palate, a closure is formed in the flow path along the midsagittal line. The closure is normally formed in the anterior part of the oral cavity and is about 1–1.5 cm long. However, it is speculated that the flow may split at a location posterior to the closure, thereby giving a longer length of the lateral channels up to 3–4 cm. Lateral channels of length around 3 cm have been shown to have significant effects on the resulting sound spectrum. To investigate the flow and acoustic field involved, finite element analysis was performed on a simplified model of the vocal tract during lateral sound production. The tongue was modeled as a rectangular constriction with a tapering slope on the upstream side and two flow channels on its two sides. The results show that the rising up of the tongue causes the flow to split into three regions of different flow amplitude and phase: one main region above the tongue surface and two regions around the tongue. This flow splitting occurs at the point where the tongue first begins rising up, well before the actual constriction location. The effective length of the lateral channels is therefore much longer than the length of the lingual constriction.

MR atlas of the baboon brain for functional neuroimaging

Mathematical co-registration of functional image data (e.g., positron emission tomography, PET) to anatomical magnetic resonance (MR) imaging data allows for objective associations between function and anatomy. Baboons are often used as non-human primate models for functional neuroimaging studies. In this work, a digital MR-based high-resolution atlas of the baboon brain was generated and evaluated for PET. The atlas was generated from six SPGR-MR datasets (centered at mid-sagittal line, AC-PC orientation) that were transformed into the space of one representative MR, averaged and resampled into PET space. The atlas was evaluated by comparing blood flow and dopamine receptor and serotonin transporter binding measures determined using regions-of-interest (ROIs) generated on each individual co-registered MR (ROI i) and the atlas-defined ROI template (ROI ATLAS). Common ROIs applied to all data included frontal cortex, temporal cortex, thalamus, caudate, putamen and cerebellum. High correlations ( r 2>0.87) were found between the ROI i and ROI ATLAS data for all radiotracers (linear regression across ROIs for each baboon). The average regression slope values ranged from 0.95 to 1.02 across radiotracers. Lastly, use of the atlas for statistical parametric mapping (SPM) of [ 15 O ]water data yielded good agreement with previous ROI i results. Overall, the digital MR-based atlas allowed for automatic co-registration, proved useful across a range of PET Studies, and is accessible electronically via the Internet.

環軸関節固定術の３Ｄ‐ＣＴによる術後評価 Ｔｒａｎｓａｒｔｉｃｕｌａｒ ｓｃｒｅｗの安全性に関する検討

In recent years, atlanto-axial transarticular screw fixation performed as described by Magerl for atlanto-axial subluxation has been popular because of its excellent biomechanical stability. However, there is a risk of vertebral artery injury with placement of transarticular screws.Twelve patients (age range: 18 to 72 years, mean: 60 years) underwent surgery as described by Magerl & Brooks for reducible atlanto-axial subluxation. Four were men and eight were women. Computed tomography (CT) was performed after surgery. We evaluated the position of the transarticular screw by means of sagittal reconstruction CT images. There was no screw that deviated from the C2 isthmus and had been placed incorrectly in the spinal canal. One screw (4.2%) passed through the C2 isthmus and bordered on the foramen of the transverse process. The screw angle measured between a line through the axis of the screw and the mid-sagittal line was -3-13 degrees. The screw length projected out of the C1 lateral mass was -3.6-10.8mm. There was no complication such as vertebral artery injury during screw insertion.Because of translational or rotational atlanto-axial subluxation, presurgical computed tomographic scans with sagittal reconstruction may provide information necessary to perform transarticular screw fixation safely.

A New Landmark Using the Clavicular Head of the Sternocleidomastoid Muscle for Infraclavicular Subclavian Vein Catheterization

hemodynamic monitoring and for administration of hypertonic fluids, drugs, and parenteral nutrition. Common access sites are the internal jugular veins, subclavian veins, and femoral veins. Yoffa's percutaneous supraclavicular subclavian vein catheterization technique has some disadvantages and difficulties which include dislodgement of the puncture needle and difficult enhancement of the guide wire. To overcome these problems, we modified Yoffa's technique as a symmetrical puncture against the clavicle. Methods: A patient was placed supine with his/her head turned to the opposite side with the arm at the side. The needle was inserted through the skin at a point around 1 cm below the clavicle, toward the imaginary midline of the clavicular head of the sternocleidomastoid muscle (SCM). The guide wire was inserted with a J-wire. Measurements were made to determine the length from the puncture site to the lower border of the clavicle, the depth and angles from the needle to mid sagittal line, the coronary line and skin (Fig. 2). We also evaluated the No. of punctures, wire insertions, and complications. Results: Our success rate was 95.1% and 6 cases with complications (5.9%) occurred in 102 attempts. The most serious complication was a delayed tension pneumothorax 6 h postoperatively. Conclusions: These results suggest that the new landmark for infraclavicular subclavian vein catheterization is an easy and safe procedure for an experienced physician. We also recommend close observation postoperatively for at least 24 h for complications.

A description of midsagittal tongue movement in terms of secant line kinematics

Tongue shape is a major determiner of the shape of the air channel in the vocal tract, and, hence, the acoustic signal during speech production. Flesh-point movement is a way that midsagittal tongue motion in speech production is examined, such as with the EMMA system and the x-ray microbeam system. We propose to transform the Cartesian coordinates of the flesh-points into one that specifies the position of the centers of the secant lines between each neighboring pair of flesh points, as well as the length and orientation of each secant line in this coordinate system, motion is considered in terms of translational, rotational, and stretching motions of the secant lines, with the former specifying gross motion and the latter two specifying local motion. Utterances from the X-Ray Microbeam Speech Production Database involving consonants with alveolar place of articulation are examined for kinematic differences resulting from differences in manner, vowel context, and syllable position. A further refinement of the secant line coordinates will be offered in terms of midsagittal secant line position and orientation relative to the palate and pharynx. This coordinate system should be helpful for interpreting flesh-point kinematics with regard to acoustic output.

Position des lignes temporales sur le cranium de «Mrs » Ples (A. africanus) : une attribution sexuelle est-elle possible ?

The cranium and associated matrix of Sts 5, a cranium of Australopithecus africanus is re-examined in the context of an unfused sagittal suture and the position of the temporal lines. These lines are not developed as a sagittal crest although they are close to the mid-sagittal line. A comparative study of the presence of sagittal crests in male, female, juvenile and adult specimens of extant great apes ( Gorilla , Pan , Pongo ) suggests that the existence of a sagittal crest is influenced to a greater extent by anatomical age rather than by the sex of the individuals. Le réexamen du cranium de Sterkfontein, Sts 5 ( Australopithecus africanus ), et du fragment de brèche associé, montre l'existence d'une suture sagittale non fusionnée et d'une position haute des lignes temporales supérieures. Ces lignes, bien que proches de la suture sagittale, ne forment pas de crête. Une étude comparative des fréquences de la présence de crête sagittale en fonction du stade de maturation et de la détermination sexuelle a été menée chez les populations de grands singes actuels ( Gorilla , Pan , Pongo ). La présence de crête sagittale n'est pas liée à l'attribution sexuelle mais au stade de développement post-natal de l'individu.

Facet tropism in lumbar motion segments and its significance in disc herniation

Objective and Design: To define facet tropism (FT) for each motion segment of the lower lumbar spine for subjects without disc herniation, and to evaluate the significance of facet tropism in disc herniation. Methods: Sixty subjects were evaluated by measuring the facet angle (FA) of three lower lumbar motion segments with the use of computed tomography (CT) and a computer program. The subjects were divided into two groups: 33 without disc herniation and 27 with disc herniation at one or more levels of lower lumbar motion segments. The FA was defined as the angle of the facet and midsagittal lines. The difference between the right and left FAs at each motion segment was calculated. FT was defined as an angle difference larger than the mean and one standard deviation of the angle differences between the right and left FAs at each motion segment in the group without disc herniation. Outcome Measurements: Statistical significance of the bilateral angle difference of each lower lumbar motion segment between the two groups was analyzed by the two-sample t test. Using the defined angle difference for FT, the incidence of FT in the two groups at each motion segment was analyzed by the Fisher's exact test. Results: FT was defined for the 33 subjects without disc herniation on CT scans as an angle difference larger than 12° at L3–L4, 15° at L4–L5, and 12° at L5-S1, approximately. There was no statistical significance in the bilateral FA difference ( p > .05) and incidence of FT ( p > .05) at each segment between the two groups. Conclusion: This study did not show that facet joint tropism plays a significant role in disc herniation in the lower lumbar spine.

Radiographic interproximal angulations: Implications for rotational panoramic radiography

Axial radiographs were taken on 160 subjects at the screening clinic of the Dental School, University of Texas Health Science Center at San Antonio. Intermeatal and midsagittal lines, together with coordinate axes and polynomical curves that represent the average dental arch form, were overlaid on each radiograph. Coordinate references for interproximal tangents at 3154 contacts along the average dental arch form were digitized and angulations between the arch form and midsagittal plane calculated. Interproximal angulations at the average arch form were found to vary greatly but the average fluctuated around 90 degrees over the length of the arch. Optimal beam angulations were shown to be considerably different from central ray angulations of current panoramic machines, and although most machines demonstrated favorable interproximal beam angulation in the anterior region, discrepancy in the premolar region ranged from 15 degrees to over 40 degrees. Overall the OrthOralix SD (Gendex Dental Systems, S.r.l., Monza, Italy) orthogonal projection and PM 2002 CC (Planmeca Inc. Helsinki, Finland) deviate least from optimal interproximal angulation over most of the dental arch. However, the Planmeca gives a better angulation in the canine/premolar region, whereas the OP5 10 (Palomex Instrumentarium Corp., Helsinki, Finland) is comparable with the OrthOralix SD in the molar region.

“Probing” the nature of the CNV

A widespread depolarization in the dendritic trees of cortical pyramidal neurons generates surface-negative potentials. In turn, such potentials may indicate facilitatory processes while positive-going waves may result from a lowering in cortical excitability. Accordingly, we may expect the processing of “probe” stimuli presented during surface-positive waves, i.e., during phases of lesser excitability, to be inhibited and probes presented during surface-negative waves to be facilitated. This hypothesis was tested by presenting acoustic probe stimuli at various points in time during a forewarned reaction time task. The warming stimulus (WS) elicited a late positive complex followed by a negative slow potential shift (CNV). In 75% of the total of 120 trials a probe could be presented 1.5 sec prior to the WS interval, 0.5, 1, 1.5 or 2 sec after the onset of the 3 sec visual WS, and 3 sec following the imperative signal (WS offset, requiring a fast button press response), while 25% of the trials were without any probe. Only one probe occurred during a trial. The EEG was recorded along the midsagittal line; responses to the probes were evaluated by reaction time (RT) and probe-evoked potentials. RT to probes presented late in the anticipatory interval were speeded up and probe-evoked potentials were enhanced during this interval, in parallel to the development of the slow potential and the CNV in particular. Results suggest that probe stimuli presented during the development of the CNV were processed more intensely, thereby supporting the hypothesis that slow cortical potentials indicate the timing of excitability in cortical neuronal networks. Such a tuning mechanism may serve as a basis for attentional regulation.

Modulation of Slow Cortical Potentials by Instrumentally Learned Blood Pressure Responses

We assessed whether instrumentally-learned pressor responses inhibit electrocortical activity, as predicted by learning theories of idiopathic hypertension. Subjects received beat-by-beat feedback for increases and decreases in mean arterial pressure measured from the finger (Peñáz method). Slow potentials were recorded from the midsagittal line during the final training session. Also recorded at this time were heart rate, eye movements, respiration, and post-session verbal reports of the subject's control strategies. Thirteen of 14 subjects differentiated blood pressure increases and decreases at p less than .05 or better during the final session (within-subject discriminative operant procedure). Slow potentials were less negative on blood pressure increase compared to decrease trials at all midsagittal sites (p less than .02), indicating relative cortical inhibition by pressor responses. This effect occurred even though subjects reported tensing of muscles on increase trials (p less than .01), a behavioral activity previously associated with augmented rather than diminished cortical negativity. On increase trials slow potentials shifted toward positivity just prior to heart rate deceleration (the latter effect confirming activation of the baroreceptors).

A distance-sensing device for tracking tongue configuration

An artificial palate implanted with a photoelectronic distance-sensing unit has been devised for tracking the continuous movement of the tongue surface during speech activities. A pair of narrow angle light source and photo sensor, imbedded in a 13.0x7.5x3.3 mm plastic base, has been studied experimentally in detecting the distance of a moving object by sensing the reflected light; this method has proved to be particularly effective when the object reflects with a nonsmooth surface. By arranging from four to seven units of this device along the midsagittal line of the hard palate, a real time displacement of the tongue surface can be reconstructed and displayed on the CRT. A preliminary device has been used to study the coarticulation between various consonants /p, t, k, l, n/ and vowels /i, e, a, o, u/. We have checked our data against earlier reports on coarticulation based on x-ray studies (Perkell). While the two types of results are comparable, the new device is simple in construction and allows the experiments to be free from the hazards of x-ray exposure. [Work supported by NSF, grant no. SOC-05798A01.]

The Roentgenographic Appearance of Temporomandibular Hydrarthrosis

The roentgenographic diagnosis of effusion into the temporomandibular joint has only rarely been reported. A comprehensive review of the literature revealed a single case record with accompanying illustration (2). The temporomandibular joint is a ginglymo-arthrodial (hinge-sliding) articulation between the mandibular condyle and the mandibular fossa of the temporal bone (9, 15). A fibrous disk divides the joint space into two separate compartments. The capsule of the joint is loose and baggy in front, permitting comparatively wide anterior excursion of the condyle when the mouth is opened. More detailed study reveals that the actual articulation is mainly between the anterosuperior part of the condyle and the postero-inferior surface of the articular eminence together with the adjacent anterior half of the mandibular fossa (8, 12, 19). The posterior portion of the fossa is occupied by connective tissue and, often, a small lobule of the parotid gland (4, 12). With the appearance of an effusion, the joint space becomes wider and the increased intra-articular pressure displaces the condyle in the direction of least resistance, i.e., downward and anteriorly where the capsule is loose. The roentgenographic demonstration of the temporomandibular articulation has offered considerable difficulty. For this reason, numerous reports have appeared on positioning and radiographic technic for the adequate visualization of this joint. Of these technics, the four most commonly employed are as follows: (a) routine lateral view (2, 7, 16, 17); (b) near-distance lateral view (1, 13, 18), in which the target of the tube is placed practically in contact with the skin of the opposite side in order to obliterate the shadow of the opposite condyle by gross magnification, thus improving visualization of the suspected joint; (c) an anteroposterior view of both joints simultaneously (12), obtained with the subject's head placed in the anteroposterior position on a 35° inclined plane; (d) tomographic studies (3, 11, 14). We have found the first and third of these methods most practical for general routine roentgenography. Reduplication of results is obtainable with satisfactory accuracy. For the routine lateral view, the patient's head is placed in a lateral position on a 20–23° inclined plane, the mid-sagittal line of the face lying parallel with the plane. The ear is not bent forward. The central ray is directed perpendicular to the horizontal. It passes through a point about 2 inches above and an inch and a half in front of the external meatus of the opposite side, and emerges through the suspected articulation. The target-film distance varies between 30 and 36 inches. In the roentgenograms of the normal joint (2, 7, 8, 18) the mandibular fossa is shallow and the articular eminence appears broad, round, and moderately prominent.