Superior-inferior Planes Research Articles

Accuracy of Using the Antilingula as a Sole Determinant of Vertical Ramus Osteotomy Position

The antilingula is an important landmark in mandibular ramus surgery. Its relationship to the lingula provides useful clinical information as to the position of the mandibular foramen and inferior alveolar nerve. The purpose of this study was to determine the reliability of using the antilingula as a guide to osteotomy placement for intraoral vertical ramus osteotomies. Eighteen cadaver mandibles were harvested and the antilingula was identified on each hemimandible by palpating the most prominent bulge on the lateral aspect of the mandible. In addition, the lingula (the entrance of the mandibular neurovascular bundle into the medial aspect of the ascending ramus of the mandible) was identified. A 1 mm fissure bur was used to drill a hole perpendicular to bone, from the deepest aspect of the concavity at the center of the lingula. The drill perforated both the medial and lateral cortices of the mandible. The distance from the antilingula to lingula was measured and recorded in both the anterior-posterior and the superior-inferior planes. There was complete concordance of the position of the lingula and antilingula in the anterior-posterior dimension in 11.1% of the specimens. In 33% of the specimens, the lingula was found anterior to the antilingula and in 45.6% the lingula was found posterior to the antilingula. There was complete concordance of the lingula and antilingula in the superior-inferior dimension in 2.8% of specimens. The lingula was found superior to the antilingula in 47.2% of the specimens and inferior to the antilingula in 50% of samples. In most instances, the position of the lingula was posterior-inferior relative to the position of the antilingula. At a measurement of 5 mm posterior to the antilingula (at the level of the antilingula), there was no risk of damaging the neurovascular bundle in this cadaveric study.

Jaw Opening in Novice and Experienced Classically Trained Singers

This study examined the amount of jaw opening used by two groups of singers, those with less than 4 years of training (novice) and those with more than 8 years of training (experienced) in the Western tradition of opera and art song. Movement of the jaw in the superior-inferior plane was measured with the use of a lightweight head-mounted cephalostat with a strain gauge. The subjects spoke and then sung a carrier phrase "I say b(v)p," where (v) was each of three vowels, [a], [i], and [u]. The phrase was first spoken with a natural inflection and then sung on a repeated pitch at three notes from the low, medium, and high singing voice range. There was no statistically significant difference in jaw opening between the two groups of singers. Vowel was significant for jaw opening in both groups, with [a] being produced with more jaw opening than [i] or [u]. The voicing condition was also significant for jaw opening with greater jaw opening being used as pitch increased. In general the amount of jaw opening was smallest for the low singing voice condition and greatest for the high singing voice condition. The jaw opening most typically was less in the low voice condition than in the speech condition and then increased for both the medium and high voice tasks. All but two singers used more jaw opening on the [a] vowel than the other two vowels at all voicing conditions.

Development of an integral system test for image‐guided radiotherapy

An integral system test was developed to determine the precision and accuracy of an image-guided radiotherapy system involving an x-ray volumetric imaging device mounted onto the gantry of a medical linear accelerator. The test was designed to interrogate the system components as a whole without deconstructing the individual sources of error. The integral system test was based on the imaging of an unambiguous stationary object in the treatment position and so took no account of patient related errors. An array of micromosfets interspersed within slices of a tissue equivalent phantom was developed as an imaging test object. It has previously been demonstrated that micromosfets have a very small active volume, are clearly visible on CT images, and produce no significant artifacts. In addition, the active volume of the micromosfets can be accurately inferred radiographically via the use of x-ray volumetric imaging. X-ray volumetric imaging was performed with the object in the treatment position, then reconstructed and transferred to a treatment planning system. With the phantom remaining undisturbed in the treatment position a series of treatment fields were designed to produce a series of fields with the leaf edge sweeping across active volume of the micromosfets. The fields were delivered with a micro-MLC to dosimetrically verify the position of the mosfets and compare with dose values produced by the treatment planning system. It was demonstrated that the systematic gantry flex could be accounted for by the imaging and delivery systems. For the delivery system small changes in leaf positions of the micro-MLC were required to account for gantry flex. The position of the micromosfets determined by the 50% dose position was on average (0.15+/-0.13) mm away from the position determined radiographically for the x and y axes, and (1.0+/-0.14) mm for the z axis. This implies that a margin of approximately 0.2 mm in the axial plane and 1.0 mm in the superior-inferior plane would be required at the delineation stage to ensure coverage of a tumor volume to account purely for imprecision in the image-guided radiotherapy system. The integral system test demonstrated that the image-guided radiotherapy system is capable, in the absence of patient motion, of imaging an object in the treatment position and delivering dose to that object with submillimeter accuracy.

Articular contact patterns of the normal glenohumeral joint

The purpose of this study was to determine the articular contact patterns of the normal glenohumeral joint, and to correlate these findings with cartilage and subchondral bone architecture. We studied 10 normal shoulders of cadavers. We removed all soft tissue except the joint capsule and rotator cuff and then placed the shoulders on a testing apparatus that allowed freedom of translation in three planes. After the humerus was placed in a neutral position of rotation, articular contact patterns were measured with specially prepared prescale Fuji film so that it could be inserted between the joint surfaces. Articular contact was analyzed with 222 and 444 N of joint compressive load, and the humerus was positioned in scapular plane abduction of 0°, 45°, and 90°. The contact patterns were then digitized to determine percentage contact of the humeral head on the glenoid. We studied 12 additional cadaver shoulders with fine microradiographs and histologic techniques after we sectioned the glenoids in the anterior-posterior and superior-inferior planes. We then analyzed articular and subchondral architecture. We found that when the shoulder was adducted the contact area of the humeral head on the glenoid was limited to the anatomic region of the central glenoid known as the “bare area.” This was histologically and radiographically an area of cartilage thinning and increased subchondral bone density. As the shoulder was abducted the articular congruity and percentage contact area increased. We concluded that there was a slight articular mismatch with the shoulder adducted in the normal shoulder. Histologic and radiographic studies suggested that the central bare area region of the glenoid was a region of increased compressive loading. As the shoulder was abducted the joint became more congruent and thus the contact area of the humeral head on the glenoid increased.

Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint.

The purpose of this study was to determine the contributions of specific capsuloligamentous structures to restraining superior-inferior translation of the glenohumeral joint. Eleven cadaveric shoulders were tested using a four degrees-of-freedom test apparatus. The humerus was free to translate in three planes and free to flex and extend when a superior and inferior force of 50 N was applied. Testing was performed in three positions of abduction (0 degree, 45 degrees, and 90 degrees) and three positions of rotation (neutral, maximum internal, and external). Shoulders were tested intact, vented, and after division of specific capsuloligamentous structures. The primary restraint to inferior translation of the adducted shoulder was the superior glenohumeral ligament. The coracohumeral ligament appeared to have no significant suspensory role. With progressive abduction, the anterior and posterior portions of the glenohumeral ligament become the main static stabilizers resisting inferior translation: the anterior portion was the primary capsular restraint at 45 degrees of abduction, while the posterior portion was the primary restraint at 90 degrees of abduction, neutral rotation. Our results indicate that clinical assessment of glenohumeral translation in the superior-inferior plane should be performed in multiple positions of abduction and rotation.

Detection of sinus venosus atrial septal defect by two-dimensional echocardiography.

In a 4-year period, 10 patients (mean age, 3.6 years) with a superior type sinus venosus atrial septal defect were investigated by two-dimensional echocardiography. The defects were easily visualized in all patients using a long axis vena cava superior-inferior plane with a subcostal approach, while the atrial septum seemed to be intact in the coronal plane conventionally used for atrial septal defects of the primum or secundum type. Additional colour flow mapping, performed in two patients, demonstrated shunting across the depicted defect. In our experience, the modified plane is of great diagnostic value in cases with a sinus venosus defect.