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Results for “Anatomic Landmarks”

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At least 37 records · Page 2Linked to original sources

PubMed2000

The accuracy of image registration for the brain and the nasopharynx using external anatomical landmarks.

We investigated the accuracy of 3D image registration using markers that are repeatedly applied to external anatomical landmarks on the head. The purpose of this study is to establish a lower limit of the errors that would occur in, for instance, MRI-SPECT matching, which in some situations can only be achieved using external landmarks. Marker matching was compared with (single-modality) volume matching for 20 MRI scans. The results were compared with a published expression for the target registration error (TRE) which gives the 3D distribution of the mismatch between both scans. It was found that the main error source is reapplying the external markers on the anatomical landmarks. The published expression describes the relative distribution of the TRE in space well, but tends to underestimate the actual registration error. This deviation is due to anisotropy in the error distribution of the marker position (errors in the direction perpendicular to the skin surface are in general much smaller than errors in other directions). A simulation of marker matching with anisotropy in the errors confirmed this finding. With four reapplied markers, the TRE is 6 mm or smaller in most regions of the head.

Brain↗

PubMed1998

Koch's triangle sized up: anatomical landmarks in perspective of catheter ablation procedures.

Koch's triangle contains the compact part of the atrioventricular node and is anatomically delineated by the Eustachian ridge, the membranous septum, and the insertion of the tricuspid valve. Inferiorly, Koch's triangle ends at the site of the os of the coronary sinus and, in part, is continuous with the sub-Eustachian pouch. Catheter ablation procedures for several types of reentrant tachycardias are based on identifying these anatomical landmarks. Variability in the dimensions of Koch's triangle thus may be clinically relevant. We examined 50 hearts. Anatomical landmarks measured were the Eustachian ridge, the tricuspid valve, the overall length between the membranous septum and the coronary sinus, the width of the coronary sinus, the Eustachian ridge in its roof and the distance to the tricuspid valve, and that of the sub-Eustachian pouch. Individual variations were marked. The mean values (+/- SD) were: Eustachian ridge 29.4 +/- 5.3 mm, tricuspid valve 28.9 +/- 4.5 mm, coronary sinus 10.8 +/- 2.2 mm, Eustachian ridge 3.7 +/- 2.3 mm, space underneath coronary sinus 8.6 +/- 3.4 mm, and sub-Eustachian pouch 26.8 +/- 3.3 mm. The overall length varied between 15 and 38 mm, with a mean of 26.3 +/- 4.5. In conclusion, Koch's triangle shows considerable individual variations in size. Given the fact that the absolute figures for the range in size of the compact atrioventricular node is much less than that of Koch's triangle, these variations have implications for catheter ablation procedures.

Adult↗

PubMed2000

Relationships between the epileptic focus and hand area in central epilepsy: combining dipole models and anatomical landmarks.

OBJECT: When considering resection of epileptic generators near the central sulcus, it is essential to define the spatial relationship between the epileptic generator and the primary sensorimotor hand area. In this study, the authors assessed the accuracy of dipole modeling of electroencephalographic spikes and median nerve somatosensory evoked potentials (SSEPs) in defining this relationship preoperatively and noninvasively. METHODS: Epileptic spikes and SSEPs in patients with focal central area epilepsy were represented by dipole models coregistered onto global magnetic resonance images. In patients who underwent surgery, spike dipoles were also compared with findings of electrocorticography (ECoG) and with the resection area. To improve the accuracy of the dipole models, anatomical landmarks of the hand area were used to assess the error in SSEP dipole location, and this error measure was used to correct the location of spike dipoles. Five patients with central epilepsy were studied, three of whom underwent ECoG-guided surgical resections. The location of SSEP dipoles correlated well with anatomical landmarks of the primary sensory hand area. The relative position of the spike and SSEP dipoles correlated well with the patients' ictal symptoms, ECoG findings, and the location of the epileptic focus (as defined by the resection cavity in patients who became seizure free postoperatively). Corrected spike dipoles were located even closer to the resection cavity. CONCLUSIONS: The calculation of the relative location of spike and SSEP dipoles is a simple noninvasive method of determining the relationship between the primary hand area and an epileptic focus in the central area. The spatial resolution of this technique can be further improved using easily identifiable anatomical landmarks.

Adolescent↗

PubMed2004

The extended SMAS facelift: identifying the lateral zygomaticus major muscle border using bony anatomic landmarks.

Extended superficial musculoaponeurotic system (SMAS) rhytidectomy has been advocated for improving nasolabial fold prominence. Extended subSMAS dissection requires release of the SMAS typically from the upper lateral border of the zygomaticus major muscle and continued dissection medial to this muscle. This maneuver releases the zygomatic retaining ligaments and achieves more effective mobilization and elevation of the ptotic malar soft tissues, resulting in more dramatic effacement of the nasolabial crease. Despite its presumed advantages, few reports have suggested greater risk of nerve injury with this technique compared with other limited sub-SMAS dissection techniques. Although the caudal extent of the zygomaticus muscle insertion to the modiolus of the mouth has been well delineated, the more cephalad origin has been vaguely defined. We attempted to define anatomic landmarks which could serve to more reliably identify the upper extent of the lateral zygomaticus major muscle border and more safely guide extended sub-SMAS dissections. Bilateral zygomaticus major muscles were identified in 13 cadaver heads with 4.0-power loupe magnification. Bony anatomic landmarks were identified that would predict the location of the lateral border of the zygomaticus major muscle. The upper extent of the lateral border of the zygomaticus major muscle was defined in relation to an oblique line extending from the mental protuberance to the notch defined at the most anterior-inferior aspect of the temporal fossa at the junction of the frontal process and temporal process of the zygomatic bone. The lateral border of the zygomaticus major muscle was observed 4.4 +/- 2.2 mm lateral and parallel to this line. More accurate prediction of the location of the upper extent of the lateral border of the zygomaticus major muscle using the above bony anatomic landmarks may limit nerve injury during SMAS dissections in extended SMAS rhytidectomy.

Cadaver↗

PubMed2005

An anatomic landmark to simplify subclavian vein cannulation: the "deltoid tuberosity".

The subclavian vein is frequently used to obtain central venous access. Several landmarks exist to determine the puncture site and angle, but they may require patient manipulation and anatomic measurements. We studied the feasibility of using the deltoid tuberosity, located on the lateral aspect of the clavicle, as an anatomic landmark. This would not necessitate these maneuvers and could therefore facilitate subclavian vein access. To systematically investigate this landmark, we conducted a study in four phases: 1) Two blindfolded examiners determined the distance between the tuberosity's medial border and the clavicle's lateral end in 100 dried clavicles and then 2) performed subclavian vein cannulation in 20 fresh human cadavers using the tuberosity and the suprasternal notch as landmarks. 3) Three-dimensional reconstructions of the subclavian artery and vein and surrounding structures were derived from computed tomography datasets of 10 patients. The length of the path of a virtual subclavian vein cannulation with the deltoid tuberosity landmark was measured bilaterally. 4) In a prospective, randomized trial, subclavian vein cannulation was performed in 60 patients with a standard approach or with the deltoid tuberosity as landmark. Interobserver difference between measurements in phase 1 was 3 +/- 1 mm (mean +/- sd); subclavian vein cannulation was achieved in 19 of 20 cases, whereas the subclavian artery was cannulated in one case (phase 2). In phase 3, there was no significant difference in skin-vein distance between the left (4.9 +/- 0.5 cm) and right (4.7 +/- 0.6 cm) sides. In phase 4, subclavian vein cannulation could be performed in all patients; moreover, subclavian vein cannulation was significantly (P < 0.01) faster in the deltoid tuberosity group versus the standard approach group (23 +/- 16 versus 34 +/- 14 s). We conclude that the clavicle's tuberosity may reflect an alternative anatomic landmark to simplify subclavian vein cannulation by minimizing patient manipulation and anatomic measurements.

Adult↗

PubMed2004

Anatomical landmarks for hemispherotomy and their clinical application.

OBJECT: The authors introduce the surgical concept of the central core of a hemisphere, from which anatomical structures are disconnected during most current hemispherotomy techniques. They also propose key anatomical landmarks for hemispherotomies that can be used to disconnect the hemisphere from its lateral surface around the insula, through the lateral ventricle toward the midline. METHODS: This anatomical study was performed in five adult cadaveric heads following perfusion of the cerebral arteries and veins with colored latex. Anatomical landmarks were used in five hemispheric deafferentations. The central core of a hemisphere consists of extreme, external, and internal capsules; claustrum; lentiform and caudate nuclei; and thalamus. Externally, this core is covered by the insula and surrounded by the fornix, choroid plexus, and lateral ventricle. During most hemispherotomies, the surgeon reaches the lateral ventricle through the frontoparietal opercula or temporal lobe; removes the mesial temporal structures; and disconnects the frontal lobe ahead, the parietal and occipital lobes behind, and the intraventricular fibers of the corpus callosum above the central core. After a temporal lobectomy, the landmarks include the choroid plexus and posterior/ascending portion of the tentorium to disconnect the parietal and occipital lobes, the callosal sulcus or distal anterior cerebral artery (ACA) to sever the intraventricular fibers of the corpus callosum, and the head of the caudate nucleus and ACA to detach the frontal lobe. CONCLUSIONS: These landmarks can be used in any hemispherotomy during which a cerebral hemisphere is disconnected from its lateral surface. Furthermore, they can be used to perform any resection around the central core of the hemisphere and the tentorial incisura.

Adult↗

PubMed2005

Intraobserver errors in obtaining visually selected anatomic landmarks during registration process in nonimage-based navigation-assisted total knee arthroplasty: a cadaveric experiment.

This study investigated the intraobserver errors in obtaining visually selected anatomic landmarks that were used in registration process in a nonimage-based computer-assisted total knee replacement (TKR) system. The landmarks studied were center of distal femur, medial and lateral femoral epicondyle, center of proximal tibia, medial malleolus, and lateral malleolus. Repeated registration in the above sequence was done for 100 times by a single surgeon. The maximum combined errors in the mechanical axis of the lower limb were only 1.32 degrees (varus/valgus) in the coronal plane and 4.17 degrees (flexion/extension) in the sagittal plane. The maximum error in transepicondylar axis was 8.2 degrees. The errors using the visual selection of anatomic landmarks for the registration technique of bony landmarks in nonimage-based navigated TKR did not introduce significant error in the mechanical axis of the lower limb in the coronal plane. However, the error in the transepicondylar axis was significant in the "worst-case scenario."

Arthroplasty, Replacement, Knee↗

PubMed1977

Arranging artificial teeth according to anatomic landmarks.

A system for arranging artificial teeth that satisfies three goals is desirable. These goals are accuracy, speed, and a facility for communication. Such a system, based upon certain anatomic landmarks that can be identified on an edentulous dental cast, has been described in detail. The dentist with the patient present records the anterior determinant of occlusion by placing the four central incisors according to phonetics and esthetics. All remaining teeth are placed at the laboratory according to anatomic landmarks. Then the dentist returns the trial dentures to the patient for verification, personalization, and perfection. It is the responsibility of the dentist to prescribe requirements of tooth placement in detail if he uses the services of a dental laboratory technician.

Bicuspid↗

PubMed2006

Percutaneous placement of central venous catheters: comparing the anatomical landmark method with the radiologically guided technique for central venous catheterization through the internal jugular vein in emergent hemodialysis patients.

PURPOSE: To compare the success and immediate complication rates of the anatomical landmark method (group 1) and the radiologically (combined real-time ultrasound and fluoroscopy) guided technique (group 2) in the placement of central venous catheters in emergent hemodialysis patients. MATERIAL AND METHODS: The study was performed prospectively in a randomized manner. The success and immediate complication rates of radiologically guided placement of central venous access catheters through the internal jugular vein (n=40) were compared with those of the anatomical landmark method (n=40). The success of placement, the complications, the number of passes required, and whether a single or double-wall puncture occurred were also noted and compared. RESULTS: The groups were comparable in age and sex. The indication for catheter placement was hemodialysis access in all patients. Catheter placement was successful in all patients in group 2 and unsuccessful in 1 (2.5%) patient in group 1. All catheters functioned adequately and immediately after the placement (0% initial failure rate) in group 2, but 3 catheters (7.5% initial failure rate) were non-functional just after placement in group 1. The total number of needle passes, double venous wall puncture, and complication rate were significantly lower in group 2. CONCLUSION: Percutaneous central venous catheterization via the internal jugular vein can be performed by interventional radiologists with better technical success rates and lower immediate complications. In conclusion, central venous catheterization for emergent dialysis should be performed under both real-time ultrasound and fluoroscopic guidance.

Adolescent↗

PubMed2001

Upper blepharoplasty with bony anatomical landmarks to avoid injury to trochlea and superior oblique muscle tendon with fat resection.

The trochlea and superior oblique muscle tendon separate the medial and central fat compartments in the upper lid. The purpose of this study was to determine anatomical landmarks to predict the location of and avoid injuring the trochlea and superior oblique muscle tendon with orbital fat resection during upper blepharoplasty. The trochlea and superior oblique muscle tendon were identified in 14 cadaver heads. Bony anatomical landmarks were identified to predict the oblique vector along which the trochlea and superior oblique tendon lie. The trochlea was measured in millimeters from the palpable superior orbital foramen. The oblique course of the superior oblique muscle tendon was measured from its medial location in the lateral direction in millimeters from the frontozygomatic suture. These measurements were obtained with 4.0-power loupe magnification. The trochlea was identified 10.0 +/- 0.9 mm inferior to the palpable superior orbital foramen. The superior oblique muscle tendon coursed laterally along an oblique vector to within 1 mm of the frontozygomatic suture for all 14 dissections. The vertical vector of the superior orbital foramen was measured 15.9 +/- 1.1 mm lateral to the medial canthus. The width of the bony orbit measured 42.2 +/- 1.6 mm. In two dissections, the superior orbital foramen could not be palpated, and the latter measurements were used to predict the superior orbital foramen. This anatomical study showed that when performing orbital fat resection with upper blepharoplasty, the trochlea and superior oblique muscle tendon can be identified and avoided with the above-described bony landmarks.

Adipose Tissue↗

PubMed2004

Localization of the arcuate line from surface anatomic landmarks: a cadaveric study.

The arcuate line is a relevant structure when reconstructing the abdominal wall after rectus abdominis musculocutaneous flap harvest. Its location is classically taught to be half the distance from the pubic symphysis to the umbilicus, but recent anatomic literature provides evidence to the contrary. Better understanding of the relationship between the arcuate line and surface anatomic landmarks could facilitate better preoperative planning when harvesting a rectus abdominis musculocutaneous flap. A total of 32 arcuate lines were dissected in 18 cadavers, and the location was correlated to various surface anatomic landmarks. The arcuate line was found to lie at 74.6% of the distance from the pubic symphysis to the umbilicus, and 32.7% of the distance from the pubic symphysis to the xiphoid. This location was 1.8 +/- 1.7 cm superior to the level of the anterior superior iliac spines (ASIS). This study provides further support for the finding in the anatomic literature that the arcuate line is substantially more superior than classically described. This knowledge may prove useful in preoperative planning of rectus abdominis musculocutaneous flap harvest.

Abdomen↗

PubMedDate not supplied

[Radiographic study of the applicability of three anatomical landmarks in transcranial radiography of the temporomandibular joint].

The variability of the angles formed between the long axis of the right and left condyles and the midsagittal plane, as well as the applicability of three anatomic landmarks--zigoma, gonion and base of the mandible, for transcranian radiographs of the TMJ were studied. The radiographic method used in this study was the HIRTZ axial projection. The results of the measurements showed a great variation in the angle formed by the long axis of the condyles and the midsagittal plane, from 48 degrees-79 degrees (x = 63.73 degrees) for the right side, from 50 degrees-80 degrees (x = 67.43 degrees) for the left side. It was also observed that the use of the three anatomic landmarks must not be generalized, being more precisely indicated for tapering head and face.

Cephalometry↗

PubMedDate not supplied

Determining the insertion site for retrograde intramedullary nail fixation of tibiotalocalcaneal arthrodesis: a radiographic and intraoperative anatomical landmark analysis.

Literature regarding the optimal entry point at the plantar aspect of the heel for performing tibiotalocalcaneal arthrodesis with a locked retrograde intramedullary nail is plentiful, but fails to provide meaningful guidance beyond broad generalizations. Because of the complex nature of the procedure, which requires precise alignment of multiple joints, difficulties in guide-wire placement frequently arise. Furthermore, proper guide-wire placement is usually performed under image intensification, placing the patient, surgeon, and operating room personnel at risk of ionizing radiation. This study evaluates weight-bearing lateral radiographic and anatomical landmarks to determine the optimal guide-wire entry point at the plantar heel fat pad, as well as a prospective intraoperative evaluation of the efficacy of using these landmarks to properly seat the guide wire. Radiographic and anatomical landmark portions of the study revealed that the calcaneocuboid joint was located 18.5+/-3.4 mm anterior to the tibia mid-diaphyseal line, and that the lower leg soft tissue outline approximated the calcaneocuboid joint to within 0.3+/-1.2 mm. The intraoperative portion of the study revealed that by first aligning the guide wire with the lower leg soft tissue outline, which approximated the location of the calcaneocuboid joint, and then translating the wire approximately 2.0 cm posteriorly, the increase in the efficacy of properly seating the guide wire was statistically significant (P<or=.0001). The author proposes that this technique improves the accuracy of guide-wire placement and decreases dependency on intraoperative image intensification.

Arthrodesis↗

PubMed2005

Visibility of normal thoracic anatomic landmarks on storage phosphor digital radiography versus conventional radiography.

BACKGROUND: Chest radiography is still the most frequently performed radiologic imaging study. Digital radiography is gradually replacing the conventional systems. OBJECTIVES: To compare the subjective visibility of normal anatomic landmarks in the chest on storage phosphor-based digital radiographs versus conventional screen-film radiographs. METHODS: Digital phosphor-based and screen-film posteroanterior chest radiographs were obtained during 1 year in 140 asymptomatic patients without any known pulmonary disease (119 men, 21 women; mean age 52.1 years, range 23-86). Both sets of films were independently compared by two experienced radiologists in different sessions. The visibility of each of the following anatomic landmarks was graded from 1 to 3: pulmonary fissures, carina, bronchi to left upper lobe, right upper lobe and left lower lobe, bronchus intermedius, anterior and posterior junctional lines, and vessels behind the heart and diaphragm. Additionally, subjective general quality impression of each radiograph was graded similarly. Statistical analyses were performed using the chi-square test. A P value less than 0.05 was considered significant. RESULTS: Visibility with the digital images was statistically significantly higher for the carina, left lower lobe bronchus, bronchus intermedius, and vessels behind the heart and diaphragm. Subjective general quality impression of digital radiographs was also higher (P < 0.001). No significant visibility differences were found for pulmonary fissures or junctional lines. CONCLUSION: Subjective visibility of anatomic structures behind the heart and diaphragm and at the hilae is significantly improved with phosphor-based digital radiography compared with conventional screen-film radiography. This suggests that pathologic processes such as pulmonary nodules, masses or consolidations projected over those structures may be more easily and reliably depicted on digital than on conventional chest X-rays.

Adult↗

PubMed2003

[Anatomical landmarks and surgical limits in the suboccipital transmeatal approach to the acoustic neuroma].

INTRODUCTION: To completely remove the intracanalicular portion of the acoustic neuroma through the retrosigmoid approach, we must open the posterior wall of the internal auditory canal (IAC). Therefore, drilling the IAC is one of the key steps we need to take in the transmeatal surgical approach. Nevertheless, there are no clear anatomical landmarks to identify structures such as the semicircular canals, the jugular bulb or air cells. The individual anatomical variations and those caused by the tumour itself make preoperative evaluation essential if we wish to avoid complications such as deafness, cerebrospinal fluid leakage, bleeding and air embolism. OBJECTIVE: We describe here the personal experience of the senior author (EU) in drilling the posterior wall of the IAC, with special reference to the anatomical landmarks and surgical limits in the suboccipital approach to the intracanalicular portion of the acoustic neuromas. MATERIAL AND METHODS: This work is based on anatomical data obtained from drilling human temporal bones obtained from cadavers, along with our experience with 20 patients who were operated on for acoustic neuroma using Samii's technique. RESULTS: We did not operate on any purely intracanalicular neurinomas using this approach. Two tumors were grade II (up to 20mm in diameter), 12 were grade III and 6 were grade IV. We did not drill far enough in any of these cases to be able to see the fundus of the IAC, which was confirmed by postoperative CT. Despite this, the tumor was considered to be completely removed in 17 cases. There was no mortality and we has no major complications as a result of drilling the IAC such as cerebrospinal fluid leakage or air embolism. we cannot guarantee that hearing loss of postoperative deafness, which were the norm except in one case of grade II, were caused by nervous, ischemic or labyrinthine lesions. CONCLUSION: In our material it was not possible to completely expose the IAC fundus using a retrosigmoid approach without injury to labyrinth. The areas in which the risk of secondary complications is greatest when drilling are the inferior wall and the IAC fundus. The medial extension of the suboccipital craniotomy makes drilling the intrameatal tumor exposure easier. There are no intraoperative landmarks to locate the petrous structures while drilling the IAC except for those provided by the surgeon's own experience.

Culture Techniques↗

PubMed2004

Identification of essential anatomic landmarks in performing arthroscopic single- and double-interval slides.

Contracted and immobile massive rotator cuff tears, which represent a small percentage of all massive tears, are believed by many to be irreparable. The development of arthroscopic single- and double-interval slides has allowed for the successful anatomic and tension-free repair of the majority of contracted and immobile massive rotator cuff tears. However, the safe and effective performance of interval slides requires clear and precise identification of certain anatomic landmarks, specifically the scapular spine and the base of the coracoid. This report describes how to arthroscopically identify and expose these anatomic landmarks.

Arthroscopy↗

PubMed2001

Thecaloscopy part II: anatomical landmarks.

Endoscopic anatomy differs from microsurgical anatomy. Topographical orientation as well as the proportion of objects, is different as they depend on the lens/object distance. Orientation under endoscopic conditions requires structures with defined positions or recognisable structures previously identified radiolologically. Structures are anatomical landmarks if the topographical relation to their surroundings is constant and they are easy and reliable to recognise. The contents of the dural sack are nerve roots with their supplying vessels, arachnoid trabeculars, filum terminale, and CSF. Safe navigation of a thecaloscope in relation to the bony structures is only possible with the simultaneous use of intraoperative fluoroscopy. To facilitate the navigation of scopes and instruments in the subarachnoid space we attempted to identify and describe reliable, and therefore constant recognisable anatomical landmarks.

Endoscopy↗

PubMed2004

Pelvic emergency clamps: anatomic landmarks for a safe primary application.

The application of the pelvic clamp as a tool for emergency stabilization of unstable pelvic ring fractures has proved to be a life-saving procedure. Using correct technique, the pelvic clamp can be applied within a few minutes after the patient's admission. To avoid severe complications (eg, pin perforation into the pelvis) during the application, anatomic landmarks for the correct pin placement have to be defined. The surface landmarks that are presently recommended for the correct pin placement are not always reliably found due to deformation of the body surface caused by swelling and hematoma. Our experience with 43 emergency applications of the pelvic C-clamp showed that reliable anatomic landmarks on the bony surface of the innominate bone could be identified to ensure correct pin placement. The ideal insertion point of the pins is an anatomic region on the lateral cortex of the ileum, where an easily palpable "groove" is formed by angulations of the lateral cortex of the iliac wing. Being increasingly used as an entry point for percutaneous transiliosacral screw fixations of sacroiliac joint injuries and sacral fractures, this region, which is close to the sacroiliac joint, represents an ideal point for maximum compression of the posterior pelvic ring. With the described technique, this "groove" can be identified easily even in emergency situations by blunt palpation with an instrument, avoiding the time-consuming use of a fluoroscope in most cases.

Emergency Medical Services↗