Histomorphometric analysis of unilateral condylar hyperplasia in the temporomandibular joint: the value of the condylar layer and cartilage island

Unilateral "Inactive" Condylar Hyperplasia: New Histological Data

Background: Unilateral condylar hyperplasia (UCH) is characterized by slow progression and enlargement of the condyle, accompanied by elongation of the mandibular body, resulting in facial asymmetry, occlusal disharmony, and joint dysfunction. This condition can be defined as "active" or "inactive": the active form is characterized by continuous growth and dynamic histologic changes, whereas the inactive form indicates that the growth process has stabilized. Since there are few microscopic studies on the inactive form, this study aims to investigate the histological features and expression of key proteins and bone markers in patients diagnosed with inactive UCH. Methods: A total of 15 biopsies from patients aged 28 to 36 years were examined by light microscopy and immunofluorescence for collagen I and II, metalloproteinases 2 (MMP-2) and 9 (MMP-9), receptor activator of nuclear factor- kappa B (RANK), and osteocalcin. Results: Our findings indicate that during inactive UCH, the ongoing process is not entirely stopped, with moderate expression of collagen, metalloproteinases, RANK, and osteocalcin, although no cartilage islands are detectable. Conclusions: The present study shows that even if these features are moderate when compared to active UCH and without cartilage islands, inactive UCH could be characterized by borderline features that could represent an important trigger-point to possible reactivation, or they could represent a long slow progression that is not "self-limited".

Diagnosis and Treatment in Unilateral Condylar Hyperplasia

Unilateral condylar hyperplasia (UCH) is an uncommon disease involving progressive facial asymmetry. The aim of this research was to perform an analysis of the diagnosis and treatment of patients with UCH in a clinical series. An observational retrospective study was performed on subjects with progressive facial asymmetry in the lower third of the face; all the subjects were under treatment with condylectomy and orthodontics to improve occlusion and face balance. Variables such as age, sex, clinical type, SPECT (single photon emission computed tomography) intensity and a requirement for secondary surgery were included; the Shapiro Wilk test was performed to analyze the normality of the data and nonparametric analysis and the Kruskal-Wallis or Mann-Whitney tests were used to assess the association between the SPECT difference and the variables, where 2-tailed p values < 0.05 were considered to be statistically significant. Forty-nine patients between 10 and 45 y.o. (average age: 19.1 ± 7.4 y.o.) were included in the study. There were 41 female (83.6%) and 8 male (16.4%) subjects. The SPECT analysis comparing the right and left condyles with more than 10% in caption of the isotope was present in 46 subjects; the results obtained using SPECT were not statistically related to the age or sex of the sample (p = 0.277). The patients were classified into clinical types I, II and III, and no correlations could be confirmed between the clinical type and other variables. High condylectomy was conducted on all patients, among which 14 patients underwent a secondary surgery for orthognathic or cosmetic treatment, and was not related to the initial variables used in diagnosis (p = 0.98); interestingly, the second surgical treatment was more present in the clinical type I and in subjects under 16 years old with no statistical differences. Clinical analysis, medical records, 3D imaging and SPECT should be used as a complementary analysis in assessing the diagnosis of UCH and progressive facial asymmetry.

Bone characteristics in condylar hyperplasia of the temporomandibular joint: a microcomputed tomography, histology, and Raman microspectrometry study

Unilateral condylar hyperplasia (UCH) of the temporomandibular joint is a progressive deformation of the mandibular condyle of unknown origin. UCH is characterized by excessive growth of the condylar head and neck, leading to an increase in size and volume. The aim of this study was to investigate the characteristics of the bone in patients with UCH using microcomputed tomography (micro-CT), histology, and Raman microspectroscopy. The mandibular condyles of six patients with UCH were analysed using micro-CT, histology, and Raman microspectrometry and imaging, and the results were compared with those obtained for a normal control subject. Three-dimensional micro-CT models revealed focal abnormalities of the bone microarchitecture, with foci of osteosclerosis. Histological sections showed that these foci included islands of calcified cartilage matrix with live chondrocytes. Raman analysis revealed that the cartilage matrix was more heavily calcified than the bone matrix and that the cartilage could be identified by the phenylalanine (PHE) band of its matrix, as well as by its glycosaminoglycan (GAG) content. The persistence of foci of live and active chondrocytes within the bone matrix is intriguing and appears to be pathognomonic of UCH. These new findings on UCH could help to determine its pathophysiology and thus prevent this disease, which can lead to major facial deformity.

Micro-computed tomography evaluation of bone architecture in various forms of unilateral condylar hyperplasia

Condylar hyperplasia is one of the causes of facial asymmetry and malocclusion, characterized by enlargement of the lower jaw due to excessive condyle growth activity. The aim of this study was to use micro-computed tomography (micro-CT) to evaluate the bone architecture of the condylar head and determine whether there are differences between patients with various forms of unilateral condylar hyperplasia (UCH): hemimandibular hyperplasia, elongation, and mixed form. The cohort consisted of 28 patients with a mean age of 21.9 years. All patients underwent surgical treatment (condylar shaving) for active pathological growth activity. The portion of the condylar head removed was imaged by micro-CT and subsequently evaluated. Micro-CT imaging and semiquantitative and quantitative evaluation of the bone structure (percentage bone volume, surface density, trabecular thickness, trabecular separation, degree of anisotropy, and porosity of the subchondral bone) did not reveal significant differences between the individual types of condylar hyperplasia (P > 0.05). There were no significant differences in bone structure between the anterior and posterior portions of the condylar head. No statistically significant differences between individual groups of UCH were found in the micro-CT evaluation of the condylar head bone architecture.

Patient Specific Implants to Solve Structural Facial Asymmetry After Orthognathic Surgery

ABSTRACT

Facial asymmetry is a challenge for surgeons. Some surgical strategies could be used involved soft or hard tissue of the face. The aim of this report is to show the use of patient specific implants (PSI) in a puzzle strategy based on computer aided design/computer aided manufacturer to solve a complex structural facial asymmetry after orthognathic surgery. Twenty-five-year-old male patient complain for facial asymmetry after orthognathic surgery; main deformity was related to the shape of mandibular bone in the ramus, angle, and body. After mirror image, was chose an augmentation in the right side using 2-pieces patient specific implants and the bone reduction in the vertical high of the mandibular body in the left side. Surgical technique was realized by intra oral approach installing the ramus segment at first approach and the body segment as second to obtain stability in the fitting implant-bone-implant; the left side was treated using a guide for osteotomy; after 1-year follow-up no infection or complication was observed and facial symmetry was obtained. It is possible to conclude that the puzzle technique using polyetheretherketone can be applied to obtain predictable results in a simple strategy to solve a complex problem.

A bilayered scaffold with segregated hydrophilicity-hydrophobicity enables reconstruction of goat hierarchical temporomandibular joint condyle cartilage

Temporomandibular joint (TMJ) supports chewing, talking or other daily oral activities. So far, it still remains a great challenge to treat the defected TMJ condyle cartilage through tissue engineering technology. Herein, a bilayered scaffold is designed to fully reconstruct the different cartilage matrices of TMJ condyle under same induction condition. The bilayered scaffold with segregated hydrophobicity-hydrophilicity in top and bottom layer is prepared from a low and high content of polyethylene glycol (PEG) crosslinked poly (L-glutamic acid)-g-polycaprolactone (PLGA-g-PCL). The hydrophobic aggregates in top layer support the adhesion and spread of bone mesenchymal stem cells (BMSCs), thus inducing the differentation towards fibrocartilage; while aggregates (spheroids) are formed on the hydrophlic bottom layer, showing a preferable hyaline differentiation pathway under same chondrogenic induction in vitro. After 14 d in vitro induction, the scaffold/BMSCs construct is implanted in goat TMJ condyle defects. The post-operative outcome after 2 months demonstrates that the defects are fully covered by neo-cartilage. And the regenerated hierarchical TMJ condyle cartilage perfectly consist of ordered fibrocartilage and hyaline cartilage, which is same as natural condyle cartilage. These results corroborate that this bilayered scaffold with segregated hydrophilicity-hydrophobicity carrying induced BMSCs is a promising for treatment of TMJ condyle cartilage defects.

Cross-talk between synovial fibroblasts and chondrocytes in condylar hyperplasia: an in vitro pilot study

OBJECTIVE

Increasing evidence indicates an interaction between the synovium and the cartilage in the temporomandibular joint (TMJ) and other joints. We recently demonstrated that the expression of proangiogenic factors was enhanced and that of factors promoting matrix degradation was decreased in synovial fibroblasts in condylar hyperplasia (CH). The aim of this study was to explore whether CH chondrocytes can affect the expression of these factors of synovial fibroblasts in a co-culture system.

STUDY DESIGN

The expressions of vascular endothelial growth factor (VEGF), cluster of differentiation 34 (CD34), fibroblast growth factor 2 (FGF-2), and tissue inhibitor of metalloproteinase 1 (TIMP1) from CH condylar tissues were observed by using immunohistochemical methods. Synovial fibroblasts of control tissues were co-cultured with the chondrocytes of CH, and protein expressions of VEGF, FGF-2, thrombospondin 1 (TSP1), matrix metalloproteinase 3 (MMP3), and TIMP1 were examined by using Western blotting.

RESULTS

Positive staining for VEGF, CD34, FGF-2, and TIMP1 was found in the hypertrophic cartilage layer of CH condylar tissues. Protein expressions of VEGF, FGF-2, and TIMP1 were significantly increased in co-cultured synovial fibroblasts, but TSP1 and MMP3 expressions were decreased.

CONCLUSIONS

The angiogenic factors and matrix degradation-related factors in synovial fibroblasts co-cultured with CH chondrocytes showed the same trends as those in synovial fibroblasts from CH tissue, suggesting potential cross-talk between synovial fibroblasts and chondrocytes during CH progression.

Histologic findings and related diagnostic methods in condylar hyperactivity

Condylar hyperactivity (CH) is a rare condition that entails a progressive deviation and deformation of the mandible. There is no consensus regarding characteristic histopathological features or a standardized diagnostic process; thus, histopathological analysis of the condyle cannot confirm or exclude an active CH after condylectomy is performed. An electronic search was performed in Medline, Embase, Web of Science, LILACS and grey literature up to December 2019. Additionally, a manual search was performed. Risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale and the Institute of Health Economics Quality Appraisal. All analyses were performed independently and in duplicate. Seventeen articles from 660 were included. Six articles were cross-sectional studies and 11 were case series. Almost all the articles (14) described an augmented thickness of the cartilage layer associated with cartilage islands within the subchondral bone in patients affected by CH. Histological findings seem to be mostly related to the age of the sample rather than a characteristic description of CH. No clear association was found between SPECT/scintigram uptake and a specific histological finding. Hence, there is a necessity for the development of specific tools for evaluating and reporting studies where histology is needed for diagnosis confirmation.

The Biomechanical Effect of the Sagittal Split Ramus Osteotomy on the Temporomandibular Joint: Current Perspectives on the Remodeling Spectrum

The sagittal split ramus osteotomy is a key approach for treating dentofacial deformities. Although it delivers excellent results, the sagittal split ramus osteotomy is believed to induce stress to the temporomandibular joint. Potential stress inducers could be classified as intra- and postoperative factors resulting in an inflammatory response and molecular cascades, which initiate physiological remodeling. Occasionally, this process exceeds its capacity and causes pathological remodeling, through either degenerative joint disease or condylar resorption. Hard evidence on how orthognathic surgery causes inflammation and how this inflammation is linked to the spectrum of remodeling remains scarce. Current concepts on this matter are mainly based on clinical observations and molecular mechanisms are extrapolated from fundamental research in other body parts or joints. This perspective study provides an overview of current knowledge on molecular pathways and biomechanical effects in temporomandibular joint remodeling. It provides research directions that could lead to acquiring fundamental evidence of the relation of orthognathic surgery and inflammation and its role in remodeling. Performing osteotomies in animal models and identifying inflammatory mediators as well as their effect on the joint seem promising. Patients affected by pathological remodeling can also provide samples for histological as well as molecular analysis. Individual susceptibility analysis by linking certain suspect phenotypes to genetic variation could identify the cause and molecular pathway responsible for degenerative joint disease and condylar resorption, ultimately leading to clinically applicable treatment and prevention strategies.