Canal Cross-section Research Articles

Proximal Femoral Medullary Canal Diameters in Indians: Correlation between Anatomic, Radiographic, and Computed Tomographic Measurements

To compare anatomic, radiographic, and computed tomographic (CT) measurements of the proximal femur in an Indian population. 26 left and 24 right dried cadaveric femurs were obtained. Each femur was divided into segments at 10 cross-sectional levels from proximal to distal. At each level, anteroposterior (AP), lateral, 45-degree internal oblique, and 45-degree external oblique diameters of the medullary canal were measured using radiography and CT. To minimise magnification, the femur was placed over the film/board. The neck shaft angle, femoral head offset, neck length, and femoral head diameter were also measured. For anatomic measurements, the cross-sections of the medullary canal at levels 3 to 10 were measured using a calliper. Anatomic measurements were compared with radiographic and CT measurements, and the distortion calculated. Correlation between the 3 modalities was calculated using the Pearson correlation coefficient. Accuracy index of the 2 diagnostic modalities was measured, based on the differences between anatomic and radiographic/CT measurements. Lower accuracy indices indicated higher accuracy. On AP radiographs of all femurs, the mean femoral head diameter was 45 mm, the mean neck shaft angle was 132 degrees, the mean femoral head offset was 42 mm, and the mean neck length was 63 mm. With regard to medullary canal diameters, the radiographic and CT measurements were smaller than anatomic measurements at proximal levels, but similar at distal levels. Variations between femurs and between the 4 diameters at the same level were greater at proximal levels. Combined use of radiography and CT is recommended for preoperative assessment of implant size, particularly in uncemented arthroplasty where an optimal fit is essential for biological fixation.

The Self-adjusting File (SAF). Part 1: Respecting the Root Canal Anatomy—A New Concept of Endodontic Files and Its Implementation

AimTo introduce a new concept, the self-adjusting file (SAF), and discuss its unique features compared with current rotary nickel-titanium file systems. The New ConceptThe SAF file is hollow and designed as a thin cylindrical nickel-titanium lattice that adapts to the cross-section of the root canal. A single file is used throughout the procedure. It is inserted into a path initially prepared by a # 20 K-file and operated with a transline- (in-and-out) vibration. The resulting circumferential pressure allows the file's abrasive surface to gradually remove a thin uniform hard-tissue layer from the entire root canal surface, resulting in a canal with a similar cross-section but of larger dimensions. This holds also for canals with an oval or flat cross-section, which will be enlarged to a flat or oval cross-section of larger dimensions. The straightening of curved canals is also reduced because of the high pliability of the file and the absence of a rigid metal core. Thus, the original shape of the root canal is respected both longitudinally and in cross-section. The hollow SAF file is operated with a constant flow of irrigant that enters the full length of the canal and that is activated by the vibration and is replaced continuously throughout the procedure. This results in effective cleaning even at the cul de sac apical part of the canal. The SAF has high mechanical endurance; file separation does not occur; and mechanical failure, if it occurs, is limited to small tears in the latticework. ConclusionThe SAF represents a new step forward in endodontic file development that may overcome many of the shortcomings of current rotary nickel-titanium file systems.

Effects of Root Canal Preparation on Apical Geometry Assessed by Micro–Computed Tomography

Introduction Previous micro–computed tomography analyses of root canal preparation provided data that were usually averaged over canal length. The aim of this study was to compare preparation effects on apical root canal geometry. Methods Sixty extracted maxillary molars (180 canals) used in prior studies were reevaluated for analyses of the apical 4 mm. Teeth were scanned by using micro–computed tomography before and after canal shaping with FlexMaster, GT-Rotary, Lightspeed, ProFile, ProTaper, instruments or nickel-titanium K-files for hand instrumentation. Apical preparation was to a size #40 in mesiobuccal and distobuccal and #45 in palatal canals except for GT (#20) and ProTaper (#25 in mesiobuccal and distobuccal and #30 in palatal canals, respectively). Data for canal volume changes, the structure model index (quantifying canal cross sections), and untreated surface area were contrasted by using analysis of variance and Scheffé tests. Results Mean mesiobuccal, distobuccal, and palatal canal volumes increased after preparation ( P < .05), but differences were noted for preparation techniques. GT rendered the smallest (0.20 ± 0.14 mm 3); K-files and ProFile showed the largest volume increases (0.51 ± 0.20 mm 3 and 0.45 ± 021 mm 3, P < .05). All canals were slightly rounder in the apical 4 mm after preparation indicated by nonsignificant increases in structure model index. Untreated areas ranged from 4%–100% and were larger in mesiobuccal and palatal canals than in distobuccal ones. Preparation with GT left significantly larger untreated areas in all canal types ( P < .05); among root canal types, distobuccal canals had the least amounts of untreated surface areas. Conclusions Apical canal geometry was affected differently by 6 preparation techniques; preparations with GT instruments to an apical size #20 left more canal surface untouched, which might affect the ability to disinfect root canals in maxillary molars.

Evaluation of morphological changes produced by orifice opener systems using computerized tomography (CT)

To evaluate modifications in root canal morphology following instrumentation with orifice openers using Computerized Tomography (CT). Experimental in vitro study. A preoperative CT was performed on 49 molars to measure the root canal cross-sections. After preparing the canals with 6 different nickel-titanium (Ni-Ti) rotary system orifice opener type instruments and Gates Glidden burs, a further CT was made and compared with the preoperative one. Kruskal-Wallis and ANOVA statistical analysis were used. Gates Glidden burs were significantly more aggressive in the coronal portion of the canals, although all the instruments removed more dental tissue in the most coronal of the sections studied. Bucco-lingual diameters were modified more than the mesio-distal ones. The stainless steel instruments used lead to greater modifications being required in the canals than those made of nickel-titanium. The ProFile system instruments were observed to be those that caused the least amount of change. Stainless steel burs are more aggressive than new orifice openers without significant differences observed between Ni-Ti instruments.

Root Canal Systems in Mandibular First Premolars with C-shaped Root Configurations. Part I: Microcomputed Tomography Mapping of the Radicular Groove and Associated Root Canal Cross-sections

The purpose of this study was to investigate the morphology of the radicular grooves and root canal cross-sections in mandibular first premolars that exhibit a C-shaped root. Eighty-six mandibular first premolars with C-shaped roots were scanned from the coronal to anatomical apex using μCT80. The location, length, and depth of the radicular grooves were measured. The cross-sectional morphology of root canal systems was evaluated at 11 levels. Results were subject to the Kruskal-Wallis test. Of the 86 C-shaped roots, a total of 93 radicular grooves were noted. Most of the grooves (78.5%) were located on the mesiolingual surface of the root. The C-shaped canal could vary considerably in shape at different levels, and the incidence of two canals at the middle and apical was 21% and 80%, respectively. This study shows that radicular grooves may present relevant morphologic variations in the root canal system when the C-shaped root is present.

Comparative study of shaping efficiency in C-shaped canals of mandibular second molars

To investigate the shaping efficiency of three instrumentation techniques in the C-shaped canals. Sixty extracted mandibular second molars with C-shaped canals were selected and cross-sectioned at 2, 5, 8 mm from the apex by using a muffle system as described by Bramante. The teeth containing C-shaped canals were randomly divided into three groups, respectively instrumented using stainless steel K-files in step-back and step-down techniques, and ProTaper series in crown-down technique. The digital images of canal cross-sections pre- and post-instrumentation were photographed to evaluate the proportion and position of uninstrumented area Working length loss and perforation were recorded. Data were analyzed using ANOVA. Step-down technique gained smaller uninstrumented area in the coronal third of the canals, while step-beck technique gained the same results in the apical third (P < 0.05). Uninstrumented proportion in apical part was significantly higher than in the middle and the coronal (P < 0.05). Instrumenting type I canal as 2 or 3 separated canals was likely to reduce the miss. There were three perforations in manual stainless steel K-file groups. Early opening the coronal part of C-shaped canal, shaping C-shaped canal as two or three separated canals and instrumenting the apical part with step-back technique, seemed to be the effective methods to avoid miss.

Comparison of root canal preparation with two rotary NiTi instruments: ProFile .04 and GT Rotary

To compare root canal preparation using ProFile .04 and GT Rotary nickel-titanium instruments (both Dentsply Maillefer, Ballaigues, Switzerland). Fifty extracted mandibular molars with mesial root canal curvatures between 20 and 40 degrees were randomly divided into two groups and embedded in a muffle system. All root canals were prepared to size 45 using ProFile .04 or GT rotary instruments. The following parameters were evaluated: straightening of root canal curvature, postoperative root canal cross-section, cleaning ability, safety issues and working time. Both NiTi systems maintained curvature well; the mean degree of straightening was <1 degrees . The majority of the root canals prepared with ProFile .04 (80.8%) and GT (84.0%) postoperatively showed a round or oval cross-section. For debris, ProFile .04 and GT rotary achieved 67.1% and 71.6% scores of 1 and 2, respectively. Concerning the coronal region statistical analysis showed a better result for GT than for ProFile .04. For the middle and apical thirds of the root canals, results did not differ significantly. None of the two systems completely removed smear layer. Ten procedural incidents occurred with ProFile .04 compared with five with GT. Mean working time was shorter for ProFile .04 (131.8 s) than for GT (143.7 s); the difference was not significant. Both systems respected original root canal curvature well and were safe to use. Smear layer removal was not satisfactory with either systems.

Influence of X Stop on Neural Foramina and Spinal Canal Area in Spinal Stenosis

Measurements of cross sections of exit foramen and spinal canal were performed before and after placement of X Stop in physiologic postures using positional MR scanner at the stenosed level in patients with lumbar spinal stenosis. To quantify the effect of the implant in vivo on the lumbar spine at the instrumented levels in various postures. Dimensions of the spinal canal and neural foramen decrease from flexion to extension. Symptoms of spinal stenosis occur typically in standing or extension. The X Stop device is designed to distract the posterior elements of the stenotic segment and place it in flexion to treat neurogenic claudication. We think that the device will improve the dimension of the canal in standing and extension. Twenty-six patients with lumbar spine stenosis underwent a one- or two-level X Stop procedure. All had preoperative and postoperative positional MRI in standing, supine, and sitting flexion and extension. Measurements were carried out on the images acquired. Significant increase in the dimensions of the neural foramen and canal area were demonstrated after surgery. The X Stop device improves the degree of central and foraminal stenosis in vivo.

A comparative study of root canal preparation with NiTi‐TEE and K3 rotary Ni‐Ti instruments

To evaluate and compare several parameters of curved root canal preparation using two different Ni-Ti systems: NiTi-TEE (Sjöding Sendoline, Kista, Sweden) and K3 (Sybron Endo, Orange County, CA, USA). Fifty extracted mandibular molars with mesial root canal curvatures ranging from 20 to 40 degrees were divided into two groups. In one group, 50 root canals were instrumented using NiTi-TEE files to an apical size 30; 0.04 taper (the largest available size at the time of this study). In the other group, 50 root canals were prepared with K3 instruments to an apical size 45; 02 taper. Both systems were used in a crowndown manner, with copious NaOCl (3%) irrigation and a chelating agent (Calcinase Slide, lege artis, Dettenhausen, Germany), employing torque-controlled motors. For assessment of shaping ability, pre- and postinstrumentation radiographs and cross-sectional photographs of canals were taken and changes in canal curvature and root canal diameter documented. Cleaning ability was evaluated by investigating specimens of the apical, medial and coronal third of the root canal wall under a scanning electron microscope using 5-score indices for debris and smear layer. Procedural errors (instrument separations, perforations, apical blockages, loss of working length) and working time were recorded. Nonparametric anova was used to compare straightening of canal curvatures, canal cross-sections and canal wall cleanliness (P < 0.05), whereas working time was analysed using the parametric anova (P < 0.05). Both Ni-Ti systems maintained curvature well: the mean degree of straightening was 0.2 degrees for NiTi-TEE and 0.4 degrees for K3 with no statistical significance between the groups. Post-instrumentation cross-sections of the root canals revealed an acceptable contour (round or oval) in 50.6% of cases for the NiTi-TEE group and in 65.3% of cases for the K3 group. The difference was not significant. The SEM investigation of canal walls showed equally good debris removal for both systems: NiTi-TEE prepared canal walls in 74.7% of cases with scores I and II; K3 achieved these scores in 78.7% of cases. For smear layer, NiTi-TEE and K3 only received good scores (I and II) in 38.7% and 40% of canal wall specimens, respectively. For both parameters, no significant differences were found between groups. File fractures did not occur, but loss of working length was observed in one case following the preparation with NiTi-TEE and in three cases during K3 instrumentation. Mean working time was significantly shorter for NiTi-TEE (170 s) than for K3 (208 s). Both systems maintained original canal curvature well and were safe to use. Whilst debridement of canals was considered satisfactory, both systems failed to remove smear layer sufficiently.

Percent spinal canal compromise on MRI utilized for predicting the need for surgical treatment in single-level lumbar intervertebral disc herniation

Background context There is limited information describing the correlation between the initial quantitative measurements on magnetic resonance imaging (MRI) scans of disc herniation area, canal cross-section areas, percent canal compromise, and disc herniation location to the need for surgery. Purpose Our aim is to determine if the size of disc herniation area, canal cross-section area, percent canal compromise, and disc herniation location taken from MRI images of patients with symptomatic single-level lumbar herniated intervertebral discs upon initial presentation to a spine surgeon, were predictive of the need for surgical treatment. Study design/setting This is a retrospective case matched study of patient MRI images in the senior author's private practice. Patient sample From a pool of 332 patients with sciatica caused by lumbar intervertebral disc herniations at our institution, 65 patients had surgery, of which MRI images were available and analyzed on 44 patients. Forty-four additional patients were randomly selected from the remaining 267 original group as nonoperative controls. Methods The axial MRI image showing the largest canal compromise by the herniated disc was selected for measurements. Using T1- and T2-weighted images, the areas of interest were digitally scanned at high resolution. The canal area and disc herniation area measurement were calculated from the total number of pixels per cross-sectional area, multiplied by a scan correction factor, mm 2 /pixel. Disc herniation locations were classified into either central or paracentral. The percent canal compromise was obtained by disc herniation area divided by canal cross-section area and multiplied by 100. Results The surgical group's overall mean herniated disc area was 219.6 square millimeter (mm 2), 179.8 at L4-5, and 267.4 at L5-S1. The nonoperative group's overall mean herniated disc area was 178.4 mm 2, 135.1 at L2-3, 160.3 at L4-5, and 207.4 at L5-S1. The surgical group's overall mean canal cross-sectional area was 471.8 mm 2, 418.6 at L4-5, and 535.6 at L5-S1. The nonoperative group's overall mean canal cross-sectional area was 541.3 mm 2, 518.1 at L2-3, 446.8 at L4-5, and 669.9 at L5-S1. The overall percent canal compromise ratio in the surgery group was 46.7%, 44.1% at L4-5, and 49.8% at L5-S1. The overall percent canal compromise in the nonoperative group was 34.2%, 34.1% at L2-3, 36.1% at L4-5, and 31.8% at L5-S1. The percent canal compromise in central herniations at L4-5 level was 53.0% in the surgical group, and 32.8% in the nonoperative group; at the L5-S1 level surgical group percent canal compromise was 64.1% and in the nonoperative group canal compromise was 27%. L4-L5 level paracentral herniations canal compromise was 36.7% in the surgical group compared with 42.5% canal compromise in the nonoperative group. At the L5-S1 level the canal compromise was 45% in the surgical group and 34.8% in the nonoperative group. Conclusions Our findings show a trend for patients treated with surgery to have larger disc herniation areas and smaller canal cross-section areas, corresponding to larger percent canal compromise than the nonoperative group. Centrally located herniations followed this trend closely at all levels studied. However, the paracentral herniation at the L4-5 level does not follow this trend, possibly because paracentral disc herniation clinical course is determined more by herniation location rather than the overall herniation size.

Comparison of an analytic horn equation approach and a boundary element method for the calculation of sound fields in the human ear canal

The sound field inside a model human ear canal has been computed, to show both longitudinal variations along the canal length and transverse variations through cross-sectional slices. Two methods of computation were used. A modified horn equation approach parametrizes the sound field with a single coordinate, the position along a curved center axis-this approach can accommodate the curvature and varying cross-sectional area of the ear canal but cannot compute transverse variations of the sound field. A boundary element method (BEM) was also implemented to compute the full three-dimensional sound field. Over 2000 triangular mesh elements were used to represent the ear canal geometry. For a plane piston source at the entrance plane, the pressure along the curved center axis predicted by the two methods is in good agreement, for frequencies up to 15 kHz, for four different ear canals. The BEM approach, though, reveals spatial variations of sound pressure within each canal cross section. These variations are small below 4 kHz, but increase with frequency, reaching 1.5 dB at 8 kHz and 4.5 dB at 15 kHz. For source configurations that are more realistic than a simple piston, large transverse variations in sound pressure are anticipated in the vicinity of the source.

4:11 28. An RCT of Orthotrac vest unloading vs. EZ brace—one-year outcomes

BACKGROUND CONTEXT: Patients with discopathy have leg pain due to compression or chemical neuritis. Axial load causes reduction in canal cross-section. A load of 25–50% body weight longer than 5 min reduces area to <100 mm2. A method that reduces axial load while weight bearing may provide symptomatic relief.

The spatial distribution of sound pressure within the human ear canal

The sound field inside a human ear canal has been computed using 2 approaches. A simple model, a modified Webster horn equation approach, can accommodate the curvature and varying cross section of the ear canal. Calculations using the horn equation demonstrate the formation of standing waves within the canal. The pressure may be interpreted as either the pressure along the center axis of the canal or the average pressure within a cross-sectional slab. To investigate possible spatial variation through a cross section, the sound field has also been computed using the boundary element method (BEM). Over 2000 triangular mesh elements, 1 mm or less in size, were used to represent the canal geometry. For a plane piston source at the canal entrance and both a rigid and a resistive impedance condition at the eardrum position, the computed sound pressures along the center axis of the ear canal are in good agreement with the horn equation calculations, up to 15 kHz. The BEM approach, though, reveals spatial variations of sound pressure through each canal cross section, increasingly significant as frequency increases. Further, for source configurations that are more realistic than a simple piston, large transverse variations in sound pressure are anticipated.

Comparison of root canal preparation using RaCe and ProTaper rotary Ni‐Ti instruments

To compare various parameters of root canal preparation using RaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland) and ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) nickel-titanium (Ni-Ti) instruments. Fifty extracted mandibular molars with mesial root canal curvatures between 20 degrees and 40 degrees were embedded in a muffle system. All root canals were prepared to size 30 using RaCe or ProTaper rotary instruments in low-torque motors with torque control and constant speed of 300 r.p.m. (ProTaper with ATR Tecnika, Advanced Technology Research, Pistoia, Italy; RaCe with EndoStepper, S.E.T., Olching, Germany). In both groups irrigation was performed with 2 mL NaOCl (3%) after each instrument size. Calcinase-Slide (lege artis, Dettenhausen, Germany) was used as a chelating agent with each instrument. The following parameters were evaluated: straightening of curved root canals, postoperative root canal cross-sections, safety issues and working time. Cleanliness of the root canal walls was investigated under the SEM using 5-score indices for debris and smear layer. Statistical analysis was performed using the following tests: Wilcoxon's test for straightening and working time was used (P < 0.05); Fisher's exact test for comparison of cross-sections and root canal cleanliness (P < 0.05). Both Ni-Ti systems maintained curvature well; the mean degree of straightening was less than 1 degrees for both systems. Following preparation with RaCe, 49% of the root canals had a round or oval diameter and 50% an irregular diameter, ProTaper preparations resulted in a round or oval diameter in 50% of the cases. For debris, RaCe and ProTaper achieved 47 and 49% scores of 1 and 2, respectively; there was no significant difference. For smear layer, RaCe and ProTaper achieved 51 and 33% scores 1 and 2, respectively; no statistically significant differences were apparent for the coronal and middle sections of the root canals, but RaCe performed significantly better in the apical region (Fisher's exact test, P = 0.0392). Two roots lost working length with RaCe instruments, whilst ProTaper preparation resulted in two roots loosing working length and one fractured instrument. Mean working time was shorter for ProTaper (90.9 s) than for RaCe (137.6 s); the difference was significant (Wilcoxon's test, P = 0.011). Both systems respected original root canal curvature well and were safe to use. Cleanliness was not satisfactory for both systems.

A comparison of the minimum canal wall thickness remaining following preparation using two nickel–titanium rotary systems

To examine in vitro whether Profile or Hero 642 nickel-titanium rotary instrument systems substantially reduce the minimum canal wall thickness present following root-canal preparation. The canal anatomy of 26 mesial roots from mandibular molars with separate buccal and lingual canals was evaluated before and after instrumentation using the Endodontic Cube. Following access, working lengths were determined and then samples invested within the cube using acrylic resin. Canal cross-sections were subsequently prepared. Samples were then instrumented within the cube and pre- and post-instrumentation images of the sections were compared to determine the minimum canal wall thickness remaining after preparation. Buccal and lingual canals within the sections from each level (coronal to apical) showed a reduction in minimum canal wall thickness after instrumentation. No statistically significant differences in canal wall thickness were found between the two systems at any level of the root. Instrumentation with either of the two systems under investigation did not compromise canal wall thickness. Pre-operative canal wall thickness was found to be the most significant factor determining the minimum canal wall thickness after preparation.

Changes in Root Canal Geometry after Preparation Assessed by High-Resolution Computed Tomography

Root canal morphology changes during canal preparation, and these changes may vary depending on the technique used. Such changes have been studied in vitro by measuring cross-sections of canals before and after preparation. This current study used nondestructive high-resolution scanning tomography to assess changes in the canals' paths after preparation. A microcomputed tomography scanner (cubic resolution 34 microm) was used to analyze 18 canals in 6 extracted maxillary molars. Canals were scanned before and after preparation using either K-Files, Lightspeed, or ProFile .04 rotary instruments. A special mounting device enabled precise repositioning and scanning of the specimens after preparation. Differences in surface area (deltaA in mm2) and volume (deltaV in mm3) of each canal before and after preparation were calculated using custom-made software. deltaV ranged from 0.64 to 2.86, with a mean of 1.61 +/- 0.7, whereas deltaA varied from 0.72 to 9.66, with a mean of 4.16 +/- 2.63. Mean deltaV and deltaA for the K-File, ProFile, and Lightspeed groups were 1.28 +/- 0.57 and 2.58 +/- 1.83; 1.79 +/- 0.66 and 4.86 +/- 2.53; and 1.81 +/- 0.57 and 5.31 +/- 2.98, respectively. Canal anatomy and the effects of preparation were further analyzed using the Structure Model Index and the Transportation of Centers of Mass. Under the conditions of this study variations in canal geometry before preparation had more influence on the changes during preparation than the techniques themselves. Consequently studies comparing the effects of root canal instruments on canal anatomy should also consider details of the preoperative canal geometry.

Deposition of fine sediments in irrigation canals

Sediment control structures constructed at the heads of run-of-river irrigation schemes have little effect on the very fine sands and silts that settle in the smaller distribution canals. One means of minimising the effects of fine sediment deposition in small canals is to design canals so that deposition occurs at selected locations, rather than throughout the canal network. Standard sediment transport predictors cannot be used to predict the effects of changing canal slopes and cross sections when sediment sizes are very small, and thus cannot be used to determine dimensions and slopes of small canal “settling basins”.

Percutaneous laser discectomy: MR findings within the first 24 hours after treatment and their relationship to clinical outcome

Objective: The purpose of this study was to evaluate the early MR appearances of the intervertebral disc obtained within 24h after percutaneous laser discectomy and to determine if a correlation exists between the MR images and the clinical outcome. Subjects and Methods: Twenty-nine discs in 26 patients with contained lumbar disc herniation treated by laser were included. Laser intervention was performed using Ho:YAG laser system. The results were quantitatively analysed by measuring areal changes of the herniated mass on axial T1-weighted images and signal changes within the disc on sagittal T2-weighted images. Clinical outcomes were evaluated according to Japanese Orthopaedic Association score (JOA score), and recovery rates based on JOA score immediately and 1 year after treatment were calculated. Results: The recovery rate immediately after treatment was 53.1%, and increasing to 64.6% 1 year later. The size of the disc herniation ranged from 7% to 55% of the axial cross-section of the spinal canal pre-operatively and no significant changes were noted postoperatively. Also no correlation was found between the pre-operative herniation size and the recovery rate. The signal changes within the disc increased significantly after treatment, but no correlation was present between the signal changes and the recovery rate. In five patients, soft-tissue changes along the laser tract were well demonstrated on MR imaging. Conclusion: Although immediate postoperative MR imaging shows early tissue changes induced by laser, our study has not proven that immediate postoperative MR imaging could predict the clinical outcome after percutaneous laser discectomy.

Further studies into proximal interphalangeal joint dimensions for the design of a surface replacement prosthesis: medullary cavities and transverse plane shapes.

The proximal and middle phalanges from 83 proximal interphalangeal joints (PIPJs) were set in clear plastic and sectioned in the transverse plane leaving the heads whole. The sections were cleaned, shadowgraphed and measured. The medullary canals were marked on sagittal and frontal plane shadowgraphs of the intact bones and analysed. The information was then used in the design of a surface replacement prosthesis for the PIPJs. The main dorsal surface of the proximal phalanx (PP) was found to be angled to the longitudinal baseline of the bone by a mean of 5.19 degrees. This angle increased just proximal to the phalangeal head to a mean of 11.84 degrees. The mean ratio between these angles was 2.71. The phalangeal shaft bone was thicker laterally than dorsally and palmarly, and thicker dorsally than palmarly for the proximal and middle phalanges throughout the length of the bone. The shape and size of the transverse cross-section of the medullary canal changed throughout the length of the shaft. The centreline of the PP medullary canal coincided with the midline of the bone in the frontal plane and was approximately a straight line along the length of the canal. In the sagittal plane the centreline was slightly palmar to the midline and the angle between it and the longitudinal baseline of the bone changed along the length of the canal. In the region of the shaft just proximal to the PP head (where the stem of a surface replacement prosthesis would fit) the mean angle was 10.63 degrees. The centreline was offset dorsally from the centre of rotation of the PIPJ by a mean of 0.83 mm, 0.83 mm, 0.80 mm and 0.57 mm for the index, middle, ring and little fingers respectively, with an overall mean of 0.76 mm. The mean PP head heights (transverse plane) were 9.17 mm, 9.33 mm, 8.73 mm and 7.40 mm and the mean PP widths (transverse plane) were 12.86 mm, 13.25 mm, 12.75 mm and 10.54 mm for the index, middle, ring and little fingers respectively. The mean angle between the lateral sides of the condyles to the transverse baseline was 78.35 degrees and the mean distance from the centreline of the PP head (transverse plane) to the bases of the two condyles was 4.69 mm. The mean maximum depth of the PP head intercondylar sulcus in the frontal plane was 0.72 mm and in the transverse plane, the mean maximum depth of the intercondylar sulcus on the anterior face was 0.82 mm.

Method of manufacturing an in-the-ear hearing aid, auxiliary tool for use in the method, and ear mould and hearing aid manufactured in accordance with the method

In a method of manufacturing an in-the-ear hearing aid an auxiliary element (19) whose cross-section is larger than that of an auditory canal (7) is introduced into the auditory canal. As a result of this, the auditory canal (7) is expanded. Subsequently, a hollow vent tube (25) is inserted into the auditory canal, after which the auditory canal (7) is filled with a viscous material (29). After the viscous material has solidified the mould is removed from the auditory canal, the vent tube (25) ensuring that air is admitted to a space behind the mould. The mould thus formed has a cross-section larger than the cross-section of the auditory canal. Subsequently, a housing for the hearing aid is made, the mould being used as a template. Consequently, the hearing aid will fit tightly in the auditory canal, which improves the wearing convenience. The auxiliary element (19) used in this method has a cylindrical wall formed with a plurality of apertures to allow the passage of the viscous material to spaces between the auxiliary element and the wall of the auditory canal. The auxiliary element (19) further comprises a sleeve for guiding the vent hose (25).