Plastination: a new approach to morphological research and instruction with excised larynges

Development of an ultrathin sheet plastination technique in rat humeral joints with osteoarthritis induced by monosodium iodoacetate for neovascularization study

Injection with monosodium iodoacetate (MIA) is widely used to produce osteoarthritis (OA). Ultrathin sheet plastination has been used to study the morphology of structures, with strong application in anatomical education and research. Our aim was to carry out, for the first time, ultrathin sheet plastination of rat humeral joints to observe the neovascularization provoked by OA. We injected 0.1 mL of MIA into the left humeral joints of ten Sprague-Dawley rats. The right shoulders of the same rats were used as control. Sixteen weeks after the injection, the animals were euthanized and were given an immediate red epoxy resin injection through the thoracic aorta. The samples were fixed in 10% formalin, prior to the plastination process, without decalcification. Samples were dehydrated with acetone (100%) at - 25 °C, for 10 days. Later, for degreasing, samples were immersed in methylene chloride at room temperature during 1 week. Forced impregnation was performed inside a stove within a vacuum chamber. The plastinated blocks obtained were cut with a slow velocity diamond blade saw. Slices were placed in curing chambers to achieve curing and final tissue transparentation. 230 μm thickness slices were obtained. The slices were analyzed under magnifying glass and microscope, achieving visualization of OA neovascularization. The cartilage affected by OA loses its ability to remain avascular, and blood vessels invade it from the subchondral bone to the calcified and uncalcified cartilage. Ultra-thin sheet plastination is useful to observe articular cartilage neovascularization, caused by OA induced with MIA in humeral rat joint.

Evaluation of Yanagihara facial nerve grading system based on a muscle fiber analysis of human facial muscles

Purpose

We morphometrically analyzed human facial muscles, and evaluated the Yanagihara facial nerve grading system using our data.

Methods

We used 15 types of human facial muscle, 2 types of masticatory muscle and 2 types of skeletal muscle. The materials were obtained from 11 Japanese male cadavers aged 43–86 years. We counted the muscle fibers and measured the transverse area of the muscle fibers (TAMF), and then calculated the number of muscle fibers (NMF) per mm² and the average TAMF.

Results

We found a significant correlation between average TAMF and NMF (r = − 0.70; p < 0.01). We classified facial muscles into three types based on the correlational results. Type A had a low average TAMF and high NMF. Type C had a high average TAMF and low NMF. Masticatory and skeletal muscles were characterized as Type C. Type B was intermediate between Types A and C.

Conclusions

Pathological changes in the facial muscles in facial nerve palsy seem to vary according to the type of facial muscle, because each facial muscle has a unique fiber-type composition. As the nine discrete facial expressive states evaluated in the Yanagihara system involve all three facial muscle types of our classification, the Yanagihara system is an outstanding system for grading facial nerve palsy in terms of the facial muscle morphology.

Sex differences in morphometric aspects of the peripheral nerves and related diseases

BACKGROUND

The elucidation of the relationship between the morphology of the peripheral nerves and the diseases would be valuable in developing new medical treatments on the assumption that characteristics of the peripheral nerves in females are different from those in males.

METHODS

We used 13 kinds of the peripheral nerve. The materials were obtained from 10 Japanese female and male cadavers. We performed a morphometric analysis of nerve fibers. We estimated the total number of myelinated axons, and calculated the average transverse area and average circularity ratio of myelinated axons in the peripheral nerves.

RESULTS

There was no statistically significant difference in the total number, average transverse area, or average circularity ratio of myelinated axons between the female and male specimens except for the total number of myelinated axons in the vestibular nerve and the average circularity ratio of myelinated axons in the vagus nerve.

CONCLUSIONS

The lower number of myelinated axons in the female vestibular nerve may be one of the reasons why vestibular disorders have a female preponderance. Moreover, the higher average circularity ratio of myelinated axons in the male vagus nerve may be one reason why vagus nerve activity to modulate pain has a male preponderance.

The relationship between Bell's palsy and morphometric aspects of the facial nerve

Epidemiological data of Bell's palsy (BP) have been reported. For example, the annual incidence of BP is 15-30 per 100,000 persons, with equal numbers of men and women affected, and there is no predilection for either side of the face. However, details of the relationship between BP and morphometric aspects of the facial nerve have not been available in textbooks. We performed a morphometric analysis of human facial nerve fibers and estimated the total number of myelinated axons (TN) and average transverse area of myelinated axons (ATA). The facial nerve showed a significant decrease of TN with increasing age (r = -0.77; p < 0.01), but showed no significant changes of ATA with age (r = -0.01; p = 0.96). We supposed that the TN decrease with age was a factor in the delayed recovery from BP seen in the elderly. Moreover, the TN and ATA showed no significant differences between female and male specimens (p < 0.05), or between the right and left side specimens (p < 0.05). Our present results seem to explain the absence of significant sex and affected side differences in BP.

Mapping of Ki-67 protein distribution on whole organ serial sections of the larynx

CONCLUSIONS

Immunostaining of whole organ serial sections of the larynx is feasible and will allow analysis of cellular alterations in the undisturbed anatomical context of whole organ serial sections of the larynx.

OBJECTIVES

Whole organ serial sections of the larynx have to date been used for conventional macroscopic evaluation of laryngeal tissues. The aim of this study was to establish a protocol for immunohistochemistry of whole organ sections of the larynx.

MATERIALS AND METHODS

Five laryngectomy specimens were obtained during surgery for advanced laryngeal carcinoma. Using a novel method for paraffin embedding, we chose the proliferation marker Ki-67 antigen as a model target for immunoreactivity on serial sections.

RESULTS

We were able to produce whole organ serial sections that could then be immunostained for Ki-67. A complete mapping of proliferating cells throughout the tumour, at the tumour front and in skip lesions was subsequently obtained.

Immunohistochemistry of whole-organ sections of advanced human laryngeal cancer

Whole-mount sections have been in the interest of laryngologists for long time. The aim of this study was to demonstrate the technical aspects of processing horizontal whole-mount sections of advanced laryngeal cancer specimens after total laryngectomy. Those sections may provide new insights in the biology of laryngeal cancer. Six excised human larynges were block-embedded in paraffine. Serial sections were obtained as thin as 9 mum. Sections were stained by Giemsa and standard immunohistochemistry protocols with commercial antibodies against Cytokeratine5/6, Ki-67, Topoisomerase IIalpha, and p53. Four high-power fields were selected randomly in each section of a surface grid and the percentage of positive tumor cells was noted for each antibody in the respective field. Morphometric surface maps of protein expression were generated for each parameter. The tissues remained intact without major artifacts. Specific characteristics of the tumors were identified after evaluation of the whole-mount sections. Staining of cytokeratine was homogenous, whereas nuclear markers showed a distinct heterogeneity in the respective staining patterns. By analyzation of color-coded fusion images the spatial expression of the respective antibodies could be visualized.

Thyroid alar cartilage graft in laryngoplasty: anatomical study in premature and newborn babies

The aim of this prospective anatomical study was to determine the place of the thyroid alar cartilage graft (TAC) in the laryngotracheoplasty in a population of premature and newborn babies. Ninety-eight fresh larynges, collected from autopsies, were included in the study. After measurement of cartilage dimensions and thickness, the potential dimensions of TAC and its widening capacity were calculated for each specimen. The results showed that TAC thickness was similar to the anterior cricoid arch but was significantly less than the posterior cricoid arch. The maximal degree of stenosis which could be normalized by TAC ranged between 47.8 and 74.3%. The height of the TAC allowed a widening, from the level of the glottis to the inferior part of the second tracheal ring in 100% of cases and to the inferior part of the third tracheal ring in more than 70% of cases. In conclusion, the TAC could be used for anterior grafting in laryngotracheoplasty. Its indications should be limited to grade II and a few grade III of the Myer subglottic stenosis classification without glottic or tracheal extension. Moreover, variability of TAC dimensions leads to peroperatively reassess its indication.

Morphology of the human larynx during the first five years of life studied on whole organ serial sections

The morphologic development of the human larynx during the first years of life is poorly understood to date. This study used plastinated whole organ serial sections to determine the growth and structure of the infant larynx. The larynges of 43 children 1 to 60 months old were plastinated. Whole organ serial sections were obtained by cutting the resulting specimen with a diamond band saw. The slices were then submitted to computer-assisted morphometric investigation. We found that the subglottic airway rapidly increases in size during the first 2 years of life. Further growth follows a linear mode. The relative proportion of the mucosal lining decreases likewise. In contrast to that in adults, and comparable to that in most mammals, the cartilaginous glottis accounts for 60% to 75% of the vocal folds' length at <2 years. No sexual dimorphism of the larynx exists during childhood. This study supplies detailed morphometric data on the growth and structure of the human larynx during the first years of life. It is the first to use plastinated whole organ serial sections for morphology of the pediatric larynx. Therefore, this study provides quantitative anatomic data of clinical interest that have not been available to date.

Bone density measurements of the paranasal sinuses on plastinated whole-organ sections: anatomic data to prevent complications in endoscopic sinus surgery

OBJECTIVE/HYPOTHESIS

Although anatomic data regarding the gross anatomy of the paranasal sinuses are available, severe complications of endonasal sinus surgery (ESS) are frequently reported. To understand and to avoid these complications, density of bony walls of the paranasal sinuses were studied in this report. Special attention was given to the analysis of the bone density in regions where minor and major complications occur in ESS.

METHODS

Thirty cadaver heads were embedded in epoxy resin. The plastic blocks were sectioned with a diamond-coated wire saw into 1.0-mm thick, parallel slices in axial, coronal, and sagittal planes for 10 specimens each. The slices were x-rayed and scanned with a computerized image analyzing system. For each specimen the bone density in 12 regions of interest was measured.

RESULTS

Besides the macroscopic examination of the plastinated specimens, a bone density analysis based on x-ray films is presented. Lowest bone density was found at the lateral wall of the sphenoid sinus (3.31 +/- 0.99 mm aluminum [Al]); highest density was measured at the roof of the sphenoid sinus (12.91 +/- 1.75 mm Al). Overall bone density in female specimens was 0.41 mm Al (mean) lower than in male specimens.

CONCLUSIONS

This study is the first to use plastinated whole-organ serial sections and bone density images for the analysis of potential complications in ESS. The illustration of regions with minor and major bone density of the paranasal sinuses and the ethmoid floor as presented in this study may help the novice sinus surgeon to minimize the risks of ESS and to avoid severe complications.

Three-dimensional computational reconstruction of mixed anatomical tissues following histological preparation

The creation of geometrically accurate computer models of anatomical structures with complex shape and mixed tissue types can be difficult. A method for shape reconstruction based on digital images of polymer embedded, serially sectioned specimens is presented. The distortion of bone and soft tissue specimens during all stages of histological preparation was measured. Serial sections of one specimen were stained with common histological stains to enhance the contrast between different tissue types. High-resolution digital images of these sections were then processed into a three-dimensional solid model using commercial software. Preparations containing bone and cartilaginous tissues were dimensionally stable following fixation, dehydration and embedding (shrinkage/expansion less than 2%). Staining was necessary to identify anatomical features that otherwise could not be differentiated from their surroundings. Although time consuming, this method provides cross-section images of a higher resolution than those obtained from CT or MRI scanning, and with better soft tissue visualisation.

Carpal tunnel topography during endoscopic decompression

The safety of the endoscopic technique for carpal tunnel release remains a major concern. Serious complications such as division nerves, tendons or vessels may occur. In this study the topography of the carpal tunnel was studied in fresh cadaver hands after the introduction of the blade assembly of a one portal system. By using a plastination method, it was possible to study the in situ relationships in detail by serial cross sections. Furthermore a modified Spalteholz method allowed the position of the blade to be viewed in whole specimens.

Plastination of the larynx for whole-organ sectioning

Whole-organ sectioning is an important technique for the assessment of laryngeal pathology. Since currently established methods require prior decalcification which causes morphological changes, the critical border area between cartilage and surrounding soft tissue cannot be investigated in the same specimen and morphometric studies are not possible. Plastination is a laboratory technique that has previously demonstrated its capacity to overcome these shortcomings. In so doing water and lipids are replaced by curable polymer within the laryngeal cells making decalcification unnecessary. In the present study, more than 50 human larynges were processed using block plastination (BP) and sheet plastination (SP). For BP the complete organ was plastinated as a whole and then cut into thin serial sections. For SP the fresh organ was sliced first and plastinated in a second step. Findings demonstrated that SP allowed for the production of whole-organ sections within a period of 1 week only. Section thicknesses were as thin as 15 mm using a diamond wire saw and an ultramilling device. Sectioning was possible in both coronary and horizontal planes. Following BP, specimens were cut in an industrial cutting machine to thicknesses of about 0.6 mm. Shrinkage of tissue was less than 10% for both methods. In all, SP was technically superior to routine paraffin histology, although cutting equipment is very expensive and delicate in handling. At present the technique of BP is the method of choice for macromorphometrical investigations on serial sections of the human larynx.

Functional gliding spaces of the dorsal side of the human finger

Although the clinical and functional importance of gliding and connective tissue spaces has been repeatedly emphasized (e.g. their role in the spreading of suppurative phlegmonic inflammation) only few literary findings can be presented dealing with the connective tissue spaces in the finger in the metacarpo-phalangeal transition region. Three separate gliding spaces of the finger above the dorsal aponeurosis and their various regional connections can be displayed by means of a plastic injection technique followed by plastination and production of sectional series. These gliding spaces were also examined on fixed and unfixed hands using plastic injection and subsequent dissection. A space was depicted between the proximal interphalangeal joint and the insertion of the dorsal aponeurosis on the distal phalanx of the finger, as well as a further bursa-like space over the proximal interphalangeal joint. A third space was also depicted between the metacarpophalangeal joint and the proximal interphalangeal joint, which displays a variable connection to the gliding canal of the respective extensor tendons. Methodical, functional and clinical aspects will be discussed.

The cricoarytenoid ligament: its morphology and possible implications for vocal cord movements

The cricoarytenoid ligament was studied in sections of ten plastinated adult human larynges. The collagenous fibres forming the ligament originate from a small area at the upper rim of the cricoid lamina and from the adjacent dorsal cricoid perichondrium. The fibres strengthen the dorsal and medial part of the capsule of the cricoarytenoid joint. They are arranged in several layers separated by adipose tissue. The most medial layer of the collagenous fibres is attached to the medial aspect of the vocal process, whereas the vocal cord is anchored more laterally. Contrary to the descriptions in the literature, no fibres of the cricoarytenoid ligament join the vocal cord. Especially, the medial part of the ligament is important for controlling abduction and abduction of the vocal cords. Voice disturbance may result from structural asymmetry of the cricoarytenoid ligament.

Normal topography of the conus elasticus. Anatomical bases for the spread of laryngeal cancer

The topographic relations of the conus elasticus were studied with special regard to the local spread of laryngeal cancer. Sections of twelve plastinated adult human larynges were investigated. Lateral from the median cricothyroid ligament, the conus elasticus reveals two broad gaps containing adipose tissue and blood vessels. Along these routes, tumors of the larynx may easily extend into the ventral extralaryngeal tissues by continuous growth. Fibres of the conus elasticus cover the entire cranial surface of the vocalis muscle near the muscle's insertion at the thyroid cartilage. This part of the conus elasticus has been termed "thyroglottic ligament" in the fetus [22]. In the adult, this ligament prevents early cancer of the anterior vocal cords from invading adjacent structures. Other collagenous fibres continuous with the conus elasticus provide only an incomplete layer separating the lateral cricoarytenoid and the thyroarytenoid muscle. These fibres do not constitute an effective barrier against cancer growth.

Anatomical aspects of postintubational subglottic stenosis

The subglottic regions of 54 human adult male and female larynges were studied with regard to anatomical aspects of postintubational stenosis. Fourteen specimens were impregnated with curable polymers and cut into 600-800 microns sections along different planes. Forty formalin-fixed hemilarynges were dissected. Measurements of the upper cricoid lamina and the thickness of the endocricoid soft tissues were taken for statistical analysis. Immediately beneath the glottis, the upper part of the cricoid lamina consists of two lateral plates with an average angle of 110 degrees. Distally, the cricoid adopts a more and more rounded lumen. At the level of the cricothyroid joint, the definite airway lumen is always laterally narrowed by a prominent thickening of the endocricoid soft tissue. Large amounts of loose connective tissue facilitate the development of edema in case of injury in this region. Dorsally, the submucous stratum is smaller and consists mainly of dense connective tissue. The blood vessels are fixed to the cricoid perichondrium by collagenous fibers. Any pressure applied from the airway lumen will force the vessels against the nonresilient cartilage, resulting in occlusion and ischemia. These pathophysiologic mechanisms are important for the development of early laryngeal damage during endotracheal intubation, possibly resulting in posterior stenosis due to scarring later on.