Elsevier

Journal of Voice

Volume 30, Issue 5, September 2016, Pages 538-548
Journal of Voice

Cricothyroid Articulation in Elderly Japanese With Special Reference to Morphology of the Synovial and Capsular Tissues

https://doi.org/10.1016/j.jvoice.2015.07.011Get rights and content

Summary

Objective

The present study aimed to clarify individual variations in the cricothyroid joint (CT joint).

Methods

Using 30 specimens of the CT joint obtained from elderly donated cadavers, we examined the composite fibers of the capsular ligament as well as the morphology of the synovial tissue.

Results

The capsular ligament consistently contained abundant thick elastic fiber bundles on the anterior side of the joint (anterior band) and an elastic fiber-made mesh on the posterior side (posterior mesh). The synovial membrane, lined by synovial macrophages, was usually restricted to the recesses in the medial or inferior end of the joint cavity. Without the synovial lining, elastic fibers of the capsular ligament were subsequently detached, dispersed, and exposed to the joint cavity. We also observed a folded and thickened synovial membrane and a hypertrophic protrusion of the capsular ligament. In six specimens, the joint cavity was obliterated by debris of synovial folds and elastic fiber–rich tissues continuous with the usual capsular ligament. Notably, with the exception of two specimens, we did not find lymphocyte infiltration in the degenerative synovial tissue.

Discussion

We considered the CT joint degeneration to be a specific, silent form of osteoarthritis from the absence of lymphocyte infiltration. For high-pitched phonation, the elderly CT joint seemed to maintain its anterior gliding and rotation with the aid of elastic fiber–rich tissues compensating for the loss of congruity between the joint cartilage surfaces. Conversely, however, high-pitched phonation may accelerate obliteration of the joint.

Introduction

The cricothyroid joint (CT joint) has been one of the major focuses of anatomic studies of phonation, and in elderly persons, individual variation is well known. “The CT joint performs rotation and gliding movement and regulates the extension and flaccidity of vocal fold responsible for the pitch of voice.” Although the classifications differ slightly between research groups, there seem to be three types of joint morphology: (1) a well-defined facet with a tight capsule permitting rotation but limited gliding movement; (2) no definable facet permitting a relatively large degree of gliding movement; (3) a pair of adjacent flat cartilages with a thin capsule permitting the greatest gliding movement.1, 2, 3 Notably, one type of macroscopic classification, “no definable facet” (ie, without a joint cavity), has never been reported in usual joints of the musculoskeletal system, except in the final stage of osteoarthritis. Ligaments supporting the CT joint capsule were previously called the “anterior, posterior, lateral, and medial ceratocricoid ligaments.”4, 5 However, in the present study, we tentatively coined the term “capsular ligaments” because it is unlikely that the joint capsule can be separated or discriminated from the ligaments on the basis of limited histological description.6

Previous excellent anatomic studies (see the paragraph mentioned previously) invariably focused on movement of the CT joint as well as the joint cartilage morphology. For this purpose, researchers needed soft specimens that would permit such movement. However, this made the specimens unsuitable for histology because of cell membrane autolysis and loosening of extracellular fibers under specific embalming solutions, such as the use of Thiel's or Jores' solution, containing little or no formalin or glutaraldehyde. Therefore, there has been little information about the histology of the CT joint including (1) the composite fibers of the capsular ligament (collagen and/or elastic fibers) and (2) morphology of the synovial tissue including its degeneration and pathology. Similarly, immunohistochemistry is unlikely to be applicable to soft specimens. In the musculoskeletal system, the normal synovial membrane contains macrophages with a linear arrangement.7, 8, 9 Existing information on CT joint histology has been derived from a few studies using specimens fixed with formalin-based solutions: (1) Using transmission electron microscopy, Vilkman et al4 found elastic fibers intermingled with collagen fibrils in the capsular ligament; (2) Using three specimens, Chen et al6 described the anterior and posterior recesses (a pouch lined by synovial tissue) of the CT joint cavity.

The congruity of a joint (adaptation between the two joint surfaces) is determined not only by the shape of the joint cartilage but the associated soft tissues such as the joint disk or synovial fold. In small joints similar to the CT joint, the disk and/or synovial tissue often plays a great role in creating congruity: typical examples are seen in the sternoclavicular joint, where the two cartilage surfaces do not fit (convex/flat), and even during fetal development, a thin disk creates the congruity.10 In addition to joint congruity, another requirement for the CT joint seems to be resistance to vibration. Kawase et al11 considered that, in the articulations between the ear ossicles, a very rich content of elastic fibers in the capsular ligaments absorbs the vibration to avoid loosening of the collagen fiber bundles. Consequently, to obtain a better understanding of CT joint function in the elderly, the aim of the present study was to clarify individual variations in (1) the composite fibers of the capsular ligaments and (2) the synovial tissues. It was anticipated that our findings might shed some light on individual modes of age-related degeneration.

Section snippets

Materials and methods

The study was performed in accordance with the provisions of the Declaration of Helsinki 1995 (as revised in Edinburgh 2000). We examined 30 donated cadavers (18 men and 12 women) ranging in age from 67 to 97 years, with a mean age of 82 years. The cause of death had been ischemic heart failure or intracranial bleeding. These cadavers had been donated to Akita University (20 cadavers) or Tokyo Dental College (10 cadavers) for research and education on human anatomy, and their use for research

Results

The inferior cornu of the thyroid cartilage was consistently ossified, but the cricoid cartilage facing the inferior cornu was still cartilagenous in 6 of 30 specimens. The joint cartilage often displays slight degeneration such as roughness and thinning (Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Table 1), but cartilage defects were not found. A supportive ligament of the CT joint was consistently contained abundant elastic fibers: they were elastin-positive in

Discussion

The present study clearly demonstrated the rich elastic fiber content of the capsular ligament of the CT joint, especially in the anterior band. Elastic fiber-mediated support of the joint seemed to be a result of adaptation to vibration, as seen in the articulations between the ear ossicles.11 Elastic fiber insertion into the noncalcified cartilage zone of the inferior cornu was very similar to that in the middle ear articulations. We tentatively coined the term “capsular ligaments,” and in

Acknowledgments

The authors are grateful to the individuals who donated their bodies after death to Akita University or Tokyo Dental College for research and education on human anatomy without any economic benefit. The authors also thank their families for agreeing to the donation as well as their patience in waiting for the return of their remains after study.

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