H.L. Verwoerd-Verhoef

Histologic study of the growth of the subglottis after interruption of the circular structure of the cricoid

In a previous study in growing rabbits it was demonstrated that after resection of a ventral part of the cricoid the lumen of the subglottic airway developed normal size during further growth up to the adult stage. Histologic investigations of these cases suggest that a subepithelial network of elastic fibres, ventrally suspended to the thyroid and the tracheal rings, ensures the airway lumen and prevents the development of a subglottic stenosis. Resection of a ventral part of the cricoid including the adjacent soft tissue lining of the airway causes an irreversible loss of the supporting elastic layer and the formation of scar tissue resulting in a stenosis. It was concluded that the larynx and trachea can be considered as an inner, elastic tube (= conus elasticus) lined with epithelium, suspended to an outer, segmented cartilaginous tube. At the level of the subglottis an intact conus elasticus is of more importance for the normal development of the airway lumen in young rabbits than an intact ventral half of the cricoid ring.

Wound Healing of Autologous Implants in the Nasal Septal Cartilage

The cartilaginous nasal septum of the child is often involved in trauma or congenital deformation. In perspective of its role in postnatal growth of the midface, the wound healing of septal cartilage in reaction to various surgical procedures was studied in young rabbits. It was concluded that (1) elevation of mucoperichondrium does not induce significant histologic reactions in the septal cartilage and (2) the wound reaction of cut edges includes only a +/- 0.8-mm-deep zone and lasts no longer than 2 weeks, resulting in a stump, encapsulated by fibrous tissue. Reconnection of separated parts occurs 2 weeks after surgery, mostly by merging of the perichondrial layers. Reimplantation of resected cartilage does not lead to normalisation of septal growth. This is not caused by extensive necrosis, loss of morphological organisation or decreased growth potential of the reimplanted cartilage. The essential factor seems to be dislocation (duplication, angulation) of the implant versus the non-mobilised parts of the septum preventing the growth of the implant to contribute fully to the lengthening of the total septum.

Differential effects of endolaryngeal trauma upon the growth of the subglottis.

In young rabbits (4-week-old) the growth of the subglottis was studied after an endolaryngeal soft tissue trauma. The injury induced the formation of a subglottic stenosis. In contrast to earlier observations on endolaryngeal trauma extending into the cricoid cartilage, the cricoid developed normally to the adult size and shape at 24 weeks. Similar to the earlier findings, the subepithelial layer showed considerable thickening as the result of formation of scar tissue, ectopic cartilage and fatty tissue with interruption of the elastic tunica (= conus elasticus). It was concluded that after endolaryngeal trauma in rabbits two types of subglottic stenosis can develop, determined by the depth of the injury.

Cartilage transformation in a composite graft of demineralized bovine bone matrix and ear perichondrium used in a child for the reconstruction of the nasal septum.

For the first time it was observed in a boy that a xenogenic implant of demineralized bovine bone matrix, enfolded in a pedicled flap of autogenic ear perichondrium, was transformed into autogenic cartilage. This new cartilage could be adequately used as a graft to bridge the cartilaginous defect of a nasal septum perforation. The defect was successfully closed by a technique employing four bipedicled mucosal advancement flaps of the septum and the nasal floor. The result of this pilot study, which is based on experiments in growing rabbits, appears to open the possibility to create de novo young and growing autogenic cartilage of substantial quantity in children, without the loss of the cartilage present.

Reconstruction of the growing cricoid with a composite graft of demineralized bovine bone and autogenous perichondrium; a comparative study in rabbits

In growing rabbits, the feasibility of a new type of composite graft for the reconstruction of defects in the cricoid ring is studied. This graft consists of Demineralized Bovine Bone matrix (DBBM) enfolded in a perichondrial flap. The cartilage formed in the DBBM by cells, derived from the perichondrium, is demonstrated to provide a valuable substitute for resected parts of the cricoid. A specific feature of this reconstruction is that it allows further growth and does not result in a secondary stenosis during later development.

Histologic Evaluation of Crushed Cartilage Grafts in the Growing Nasal Septum of Young Rabbits

The evolution of crushed cartilage grafts in a growing nasal septum of young rabbits was histologically investigated. Crushing leads to necrosis of the greater part of the graft. The characteristic distribution of surviving cells in isolated areas at the surface of the graft reflects different mechanical properties of the centrally and peripherally located cartilage. The necrotic parts are eliminated and replaced by new cartilage formed by surviving chondrocytes or perichondrium. The result is a complex structure composed of two types of cartilage and of fibrous tissue without any distinct organization, but nevertheless capable of growth. However, it lacks strength to transform growth into adequate lengthening of the septum. Subsequently, this will lead to the development of multiple deviations. It is concluded that crushed cartilage is no suitable implant for the reconstruction of parts of the septum which are essential in supporting the outgrowth of the nose.

Normal and Abnormal Nasal Growth After Partial Submucous Resection of the Cartilaginous Septum

Using the nose of growing rabbits as an experimental model, the effects on nasal growth of various Killian-type partial resections of the cartilaginous septum were studied. Larger resections in young animals caused decreased height and length of the nose in the adult stage. Partial resection of the basal rim of the cartilaginous nasal septum demonstrated no effects on the postnatal growth of the nasal dorsum. This is in agreement with the hypothesis that the growth of the nasal dorsum is mainly the result of expansion of an area of thick cartilage within the nasal septum extending from the sphenoid to the nasal dorsum.

Injury- and age-linked differences in wound healing and stenosis formation in the subglottis.

We studied the effects of superficial and deep endolaryngeal trauma of the subglottic airway in young and adult rabbits. In both age groups a soft stenosis was formed as long as the cartilaginous cricoid ring is not involved. This stenosis comprised a thickened subepithelial zone of scar tissue, separated from the cricoid cartilage by a layer of fatty tissue. Injury of the internal side of the cricoid cartilage induced a compact mass of scar tissue with local differentiation into fibrocartilage. In young animals only, injury of the cartilage led to remodelling of the cricoid ring (indentation or collapse of the traumatized sectors). On the basis of the differentiating effects of age and depth of the lesion, three histopathological types of subglottic stenosis were distinguished. The experimental results provide an explanation for the variability in the histopathological features of the wall of the stenotic subglottic airway, as observed in biopsies and postmortem specimens.

Wound Healing of the Nasal Septal Perichondrium in Young Rabbits

The effects of elevation of the perichondrium of the nasal septum, whether or not followed by resection of the cartilage, was histologically studied in young rabbits. The perichondrium has proved to be a highly reactive tissue. The degree of reaction varied from a transient oedema to the production of large quantities of cells, differentiating into new cartilage. The type of reaction appeared to depend on the conditions at the inner surface of the elevated perichondrium. The new cartilage differs from the original septal cartilage in morphology and growth potential. The data described above can contribute to the interpretation of previous observations in children.

Reconstruction of the Anterior Laryngeal Wall with a Composite Graft of Demineralized Bovine Bone Matrix and Autogenous Perichondrium

In this study the feasibility to reconstruct the anterior laryngeal wall in adult rabbits with a composite graft of demineralized bovine bone matrix and autogenous perichondrium was investigated. It is demonstrated that demineralized bovine bone, which is a porous biomaterial, is completely transformed into autologous cartilage, once it is implanted in a vascularized perichondrial pocket. It appeared to be possible to reconstruct the anterior laryngeal wall in adult rabbits with this newly formed cartilage. As the biomaterial has been transformed into autologous tissue it is entirely incorporated at the recipient site giving rise to solid connections (cartilaginous and/or fibrous) with the surrounding tissues.