Surgical Induction of Temporomandibular Joint Ankylosis: An Animal Model

An Instrumented Hammer to Detect the Rupture of the Pterygoid Plates

PURPOSE

Craniofacial osteotomies involving pterygomaxillary disjunction are common procedures in maxillofacial surgery. Surgeons still rely on their proprioception to determine when to stop impacting the osteotome, which is important to avoid complications such as dental damage and bleeding. Our group has developed a technique consisting in using an instrumented hammer that can provide information on the mechanical properties of the tissue located around the osteotome tip. The aim of this study is to determine whether a mallet instrumented with a force sensor can be used to predict the crossing of the osteotome through the pterygoid plates.

METHODS

31 osteotomies were carried out in 16 lamb skulls. For each impact, the force signal obtained was analysed using a dedicated signal processing technique. A prediction algorithm based on an SVM classifier and a cost matrix was applied to the database.

RESULTS

We showed that the device could always detect the crossing of the osteotome, sometimes before its occurrence. The prediction accuracy of the device was 94.7%. The method seemed to be sensitive to the thickness of the plate and to crack apparition and propagation.

CONCLUSION

These results pave the way for the development of a per-operative decision support system in maxillofacial surgery.

Animal models of temporomandibular joint heterotopic ossification: a scoping review

There are few animal models for heterotopic ossification of the temporomandibular joint (TMJ-HO). This scoping review provides an overview of current knowledge on the induction methods and specific conditions required to produce TMJ-HO in various animal models. Two independent reviewers selected papers from the PubMed, Web of Science, and Cochrane Library databases. The inclusion criteria were articles in English, in vivo studies, and a TMJ-HO induction method. Observational, in vitro, human studies, reviews, and book chapters were excluded. Twenty-four publications were included. HO was surgically, genetically, or chemically induced through single or combined defects in the condyle, articular disc, and temporal bone in animal models (sheep=9 studies, mouse=5, rat=4, rabbit=2, pig=2, goat=1, dog=1, monkey=1) specific for traumatic TMJ-HO (n=4), ankylosis (n=9), osteoarthritis (n=8), experimental disc perforation (n=1), status post-TMJ replacement (n=1), and status post bilateral sagittal split osteotomy (n=1). TMJ-HO remains challenging to study due to its multifactorial etiology and largely unknown pathogenesis, which varies between species. There is a need for more accurate, reproducible animal models that can be extrapolated to human TMJ-HO and a consolidated clinical classification system to allow for meaningful future research.

Traumatic temporomandibular joint bony ankylosis in growing rats

BACKGROUND

The pathogenesis of traumatic temporomandibular joint (TMJ) bony ankylosis remains unknown. This study aimed to explore the pathogenesis of traumatic TMJ bony ankylosis in a rat model.

METHODS

Twenty-four 3-week-old male Sprague-Dawley rats were used in this study. Excision of the whole disc, the fibrocartilage damage of the condyle and glenoid fossa, and narrowed joint space were performed in the left TMJ of the operation group to induce TMJ bony ankylosis (experimental side). The right TMJ underwent a sham operation (sham side). The control group did not undergo any operations. At 1, 4, and 8 weeks postoperatively, rats of the operation group were sacrificed and TMJ complexes were evaluated by gross observation, Micro-CT, histological examinations, and immunofluorescence microscopy. Total RNA of TMJ complexes in the operation group were analyzed using RNA-seq.

RESULTS

Gross observations revealed TMJ bony ankylosis on the experimental side. Micro-CT analysis demonstrated that compared to the sham side, the experimental side showed a larger volume of growth, and a considerable calcified bone callus formation in the narrowed joint space and on the rougher articular surfaces. Histological examinations indicated that endochondral ossification was observed on the experimental side, but not on the sham side. RNA-seq analysis and immunofluorescence revealed that Matrix metallopeptidase 13 (MMP13) and Runt-related transcription factor 2 (RUNX2) genes of endochondral ossification were significantly more downregulated on the experimental side than on the sham side. The primary pathways related to endochondral ossification were Parathyroid hormone synthesis, secretion and action, Relaxin signaling pathway, and IL-17 signaling pathway.

CONCLUSIONS

The present study provided an innovative and reliable rat model of TMJ bony ankylosis by compound trauma and narrowed joint space. Furthermore, we demonstrated the downregulation of MMP13 and RUNX2 in the process of endochondral ossification in TMJ bony ankylosis.

A systematic review on the outcome of distraction osteogenesis in TMJ ankylosis

Introduction

TMJ ankylosis (TMJa) management by arthroplasty alone fails to address the deformity and the compromised airway. Distraction osteogenesis (DO) can offer a pragmatic solution to TMJa. The aim of the study was to generate evidence towards the role of DO in TMJa, evaluate its efficiency and develop an algorithm for use of DO in TMJa.

Material and methods

The research question was formulated using the PICOS statement for reporting guidelines in systematic reviews, where the efficiency of DO was evaluated in terms of mouth opening, correction of facial deformity and asymmetry, airway correction, and its long term effects.

Results

1130 articles reported DO as a treatment modality for TMJ ankylosis, of which 32 prospective studies, 16 retrospective and 2 RCTs were included in the study. DO was used for mandibular distraction in 45 studies and for simultaneous maxillamandibular distraction in only five studies. An algorithm for use of DO in TMJa was developed.

Conclusion

Although DO has proven its application in TMJ ankylosis cases, its best use is for correction of obstructive sleep apnoea. Relapse causing loss of posterior ramal height is a concern after transport DO. Prearthroplastic DO appears to best correct mandibular deformity. A maxillomandibular deformity requires simultaneous maxillomandibular distraction. However, a metanalysis is still awaited for effectiveness of DO in TMJ ankylosis.

Induction, Treatment, and Prevention of Temporomandibular Joint Ankylosis-A Systematic Review of Comparative Animal Studies

PURPOSE

Several animal models of temporomandibular joint ankylosis (TMJA) have been described for more than the past 2 decades. The aim of this study was 2-fold: 1) to compile and summarize the evidence of animal studies that compare different forms to induce, treat (disease already established), or prevent (after trauma) TMJA; and 2) to address the following focused question: what is the quality of reporting in these studies?

MATERIALS AND METHODS

A systematic review was conducted. Animal studies conducted up to October 2019 comparing at least 2 procedures to induce, treat (disease already established), or prevent (after trauma) TMJA were considered. Compliance with the Animal Research Reporting In Vivo Experiments guidelines was checked for all studies. Studies evaluating treatment of TMJA or preventive measures also were evaluated using the SYstematic Review Center for Laboratory animal Experimentation's risk of bias tool for animal studies.

RESULTS

A total of 24 studies were included. The studies were evaluated for feasibility regarding data synthesis, and a meta-analysis was not suitable because of methodological differences, mainly regarding the animal model chosen and surgical procedures performed to induce TMJA. In 17 articles, authors aimed to investigate different procedures to induce TMJA (fibrous, fibro-osseous, or bony). In 7 articles, different treatment or preventive strategies were compared. The sheep was the most used animal in models of TMJA. Only 25% (6 of 24) of studies reported some step to minimize bias (ie, blinding of investigators, randomization procedures, or allocation concealment). Approximately 54% (13 of 24) of articles clearly commented on study limitations and potential sources of bias. Further animal studies on TMJA should consider improving their reporting standards to increase their validity and improve the reproducibility of animal experiments.

Which of the fibrous layer is more important in the genesis of traumatic temporomanibular joint ankylosis: The mandibular condyle or the glenoid fossa?

INTRODUCTION

The aim of this experimental study was to investigate, under the premise of discectomy, whether damage to either the fibrous layer of the condyle or that of the glenoid fossa, could induce temporomanibular joint (TMJ) ankylosis. And if not, which of the fibrous layer was more important in the genesis of TMJ ankylosis.

MATERIALS AND METHODS

Bilateral TMJ surgery was performed in 6 growing Xiao-wei Han sheep. Disk and condylar fibrous layer removal (DCFLR) was performed on the left TMJ, and disk and glenoid fibrous layer removal (DGFLR) was performed on the right TMJ. All animals were sacrificed at 3 months postoperatively. The TMJ complexes were examined by histological evaluation.

RESULTS

Partial fibrous ankylosis was achieved on the DCFLR side in the 6 sheep at 3 months after surgery. On the DGFLR side, pathologic characteristics of TMJ osteoarthritis could be seen; however, no evidence of ankylosis was observed. The scores of TMJ ankylosis for the DGFLR side were significantly lower than those for the DCFLR side (P<0.05).

CONCLUSION

This study demonstrated that removal of the condylar fibrous layer, not the glenoid fibrous layer, combined with discectomy could lead to traumatic TMJ ankylosis.

Reducing macrophage numbers alleviates temporomandibular joint ankylosis

Temporomandibular joint (TMJ) ankylosis is a severe joint disease mainly caused by trauma that leads to a series of oral and maxillofacial function disorders and psychological problems. Our series of studies indicate that TMJ ankylosis development is similar to fracture healing and that severe trauma results in bony ankylosis instead of fibrous ankylosis. Macrophages are early infiltrating inflammatory cells in fracture and play a critical role in initiating fracture repair. We hypothesize that the large numbers of macrophages in the early phase of TMJ ankylosis trigger ankylosed bone mass formation and that the depletion of these macrophages in the early phase could inhibit the development of TMJ ankylosis. By analysing human TMJ ankylosis specimens, we found large numbers of infiltrated macrophages in the less-than-1-year ankylosis samples. A rabbit model of TMJ bony ankylosis was established and large numbers of infiltrated macrophages were found at 4 days post-operation. Local clodronate liposome (CLD-lip) injection, which depleted macrophages, alleviated the severity of ankylosis compared with local phosphate-buffered saline (PBS)-loaded liposome (PBS-lip) injection (macrophage number, PBS-lips vs. CLD-lips: 626.03 ± 164.53 vs. 341.4 ± 108.88 n/mm²; ankylosis calcification score, PBS-lips vs. CLD-lips: 2.11 ± 0.78 vs. 0.78 ± 0.66). Histological results showed that the cartilage area was reduced in the CLD-lip-treated side (PBS-lips vs. CLD-lips: 6.82 ± 4.42% vs. 2.71 ± 2.78%) and that the Wnt signalling regulating cartilage formation was disrupted (Wnt5a expression decreased 60% and Wnt4 expression decreased 73%). Thus, our study showed that large numbers of macrophages infiltrated during the early phase of ankylosis and that reducing macrophage numbers alleviated ankylosis development by reducing cartilage formation.

Differential regulation of blood vessel formation between traumatic temporomandibular joint fibrous ankylosis and bony ankylosis in a sheep model

OBJECTIVES

Clinical and experimental studies show that the etiology of traumatic temporomandibular joint (TMJ) fibrous ankylosis and bony ankylosis are associated with the severity of trauma. However, how the injury severity affects the tissue differentiation is not clear. We tested the hypothesis that angiogenesis affects the outcomes of TMJ trauma, and that enhanced neovascularization after severe TMJ trauma would promote the development of bony ankylosis.

METHODS

Bilateral condylar sagittal fracture and discectomy were performed for each sheep, with the glenoid fossa receiving either severe trauma to induce bony ankylosis or minor trauma to induce fibrous ankylosis. At days 7, 14, 28, and 56 after surgery, total RNA was extracted from the ankylosed callus. Temporal gene expressions of several molecules functionally important for blood vessel formation were studied by real-time PCR.

RESULTS

Histological examination revealed a prolonged hematoma phase and a lack of cartilage formation in fibrous ankylosis. mRNA expression levels of HIF-1α, VEGF, VEGFR2, SDF1, Ang1, Tie2, vWF, CYR61, FGF2, TIMP1, MMP2, and MMP9 were distinctly lower in fibrous ankylosis compared with bony ankylosis at several time points.

CONCLUSIONS

Our study indicates that inhibition of angiogenesis after TMJ trauma might be a promising strategy for preventing bony ankylosis in the future.

The role of lateral pterygoid muscle in the traumatic temporomandibular joint ankylosis: A gene chip based analysis

Traumatic temporomandibular joint ankylosis (TMJA) is a common disease and disorder of the temporomandibular joint (TMJ); however, its pathogenesis has yet to be completely elucidated. In the authors' previous studies, the lateral pterygoid muscle (LPM) was confirmed to exert a function in distraction osteogenesis (DO) during the healing of a condylar fracture, which resulted in the formation of excess bone. The aim of the present study was to investigate alterations in the expression of any associated genes via an Affymetrix GeneChip method. The traumatic TMJA model was fabricated by a condylar fracture in the TMJ area of sheep with either a dissected LPM (LPD) or normal (LPN). The untreated sheep served as a control. At 4- and 12 weeks post-surgery, the condylar zone was isolated to perform the gene chip analysis, which was performed according to a standard Affymetrix protocol. The validated genes were further evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The gene chip analysis indicated that the LPN gene expression pattern was similar compared with the DO process, while LPD was similar to that of normal bone fracture healing. The validated genes were collagen type II α1 chain, C-type lectin domain family 3 member A, interleukin 1A, cartilage oligomeric matrix protein, chondromodulin (LECT1), calcitonin receptor (CALCR), transforming growth factor (TGF)-β1, Fos proto-oncogene (FOS), bone γ-carboxyglutamate protein and bone morphogenic protein (BMP)7, among which, BMP7, LECT1, CALCR and FOS were confirmed by RT-qPCR. In conclusion, the present study demonstrated that LPM exerts a DO effect during the pathogenesis of traumatic TMJA, which may provide a novel target for preventing TMJA.

Tissue Engineering for the Temporomandibular Joint

Tissue engineering potentially offers new treatments for disorders of the temporomandibular joint which frequently afflict patients. Damage or disease in this area adversely affects masticatory function and speaking, reducing patients' quality of life. Effective treatment options for patients suffering from severe temporomandibular joint disorders are in high demand because surgical options are restricted to removal of damaged tissue or complete replacement of the joint with prosthetics. Tissue engineering approaches for the temporomandibular joint are a promising alternative to the limited clinical treatment options. However, tissue engineering is still a developing field and only in its formative years for the temporomandibular joint. This review outlines the anatomical and physiological characteristics of the temporomandibular joint, clinical management of temporomandibular joint disorder, and current perspectives in the tissue engineering approach for the temporomandibular joint disorder. The tissue engineering perspectives have been categorized according to the primary structures of the temporomandibular joint: the disc, the mandibular condyle, and the glenoid fossa. In each section, contemporary approaches in cellularization, growth factor selection, and scaffold fabrication strategies are reviewed in detail along with their achievements and challenges.

Removal of the articular fibrous layers with discectomy leads to temporomandibular joint ankylosis

OBJECTIVE

The aim of this study was to investigate whether direct damage of the articular fibrous layers without condylar fracture, combined with discectomy, was enough to induce temporomandibular joint (TMJ) ankylosis.

STUDY DESIGN

Bilateral TMJ surgery was performed in 8 growing sheep. Disk removal (DR) was performed in the lateral two-thirds on the control side, and disk and articular fibrous layers removal (DFLR) was performed in the lateral two-thirds on the experimental side. Four animals were sacrificed for each side at 1 and 3 months postoperatively.

RESULTS

Fibrous ankylosis was achieved on the DFLR side in 2 of 4 sheep and fibro-osseous ankylosis in the other 2 sheep at 1 month after surgery. Fibro-osseous ankylosis developed on the DFLR side in 4 sheep at 3 months postoperatively. On the DR side, pathologic characteristics of TMJ osteoarthritis could be seen; however, no evidence of ankylosis was observed. The scores of TMJ ankylosis for the DR side were significantly lower than those for the DFLR side at different time points (P < .05).

CONCLUSIONS

This study demonstrated that removal of articular fibrous layers combined with discectomy can lead to traumatic TMJ ankylosis.

Preserving the Fibrous Layer of the Mandibular Condyle Reduces the Risk of Ankylosis in a Sheep Model of Intracapsular Condylar Fracture

PURPOSE

The aim of this experimental study was to investigate the role of the fibrous layer of the condylar head in the formation of temporomandibular joint (TMJ) ankylosis in a sheep model of intracapsular condylar fracture.

MATERIALS AND METHODS

Six growing Xiao-wei Han sheep were used in the study, and bilateral TMJ surgery was performed in each sheep. In the left TMJ, sagittal fracture of the condyle, removal of the fibrous layer of the condylar head, excision of two thirds of the disc, and removal of the fibrous zone of the glenoid fossa were performed. In the right TMJ, the same surgical management was performed, except that in each sheep, the fibrous layer of the condylar head was preserved. Three sheep were killed humanely at 1 month postoperatively, and the other 3 sheep were killed humanely at 3 months postoperatively. The TMJ complexes were examined by histologic evaluation.

RESULTS

Fibrous ankylosis was observed on the left side in 3 sheep at 1 month postoperatively and in 2 of 3 sheep at 3 months postoperatively. Fibro-osseous ankylosis was achieved on the left side in 1 sheep at 3 months postoperatively. In the right TMJ, the main postoperative histologic findings included condylar fracture healing, topical rupture or exfoliation of the fibrous layer of the condyle, and fissure between the fibrous layer and the proliferative zone of the condyle. However, no evidence of ankylosis was observed. The TMJ ankylosis scores on the right side were significantly lower than those on the left side at different time points (P < .05).

CONCLUSIONS

This study showed that the presence of the fibrous layer of the condylar head prevented the development of TMJ ankylosis in a sheep model of intracapsular condylar fracture.

Current concepts in the pathogenesis of traumatic temporomandibular joint ankylosis

Traumatic temporomandibular joint (TMJ) ankylosis can be classified into fibrous, fibro-osseous and bony ankylosis. It is still a huge challenge for oral and maxillofacial surgeons due to the technical difficulty and high incidence of recurrence. The poor outcome of disease may be partially attributed to the limited understanding of its pathogenesis. The purpose of this article was to comprehensively review the literature and summarise results from both human and animal studies related to the genesis of TMJ ankylosis.

Imaging and histologic features of traumatic temporomandibular joint ankylosis

OBJECTIVE

We aimed to study the pathology underlying traumatic temporomandibular joint ankylosis (TMJA).

STUDY DESIGN

Specimens from 10 patients with traumatic TMJA were categorized using the Sawhney classification and were decalcified and stained with hematoxylin-eosin, alcian blue/periodic acid-Schiff, alizarin red, and Masson stains. Immunostaining with anti-CD34 antibody was performed. Computed tomography and pathologic findings were compared.

RESULTS

Ankylosed areas consisted of fibrocartilaginous tissues. Bone formation occurred by osteophyte extension from the osteochondral surface toward the mass center. Endochondral ossification and osteophyte proliferation, alone or simultaneously, participated in bony ankylosis. Sequestra in the cartilaginous ankylosis preferentially formed bony bridges. Newly formed capillaries participated in ossification from the bony surface of the bone-cartilage junction; bone formed around the capillaries. Osteoclasts were present at the capillary tips.

CONCLUSIONS

Types II and III were cartilaginous-bony ankylosis, with similar components. Bony traumatic TMJA was formed by osteophyte proliferation and endochondral ossification.

A pilot trial on the molecular pathophysiology of traumatic temporomandibular joint bony ankylosis in a sheep model. Part I: Expression of Wnt signaling

OBJECTIVE

To preliminarily investigate the temporal patterns of the endogenous mRNA expression for members of the Wnt signaling and a series of genes regulating bone formation during the development of traumatic temporomandibular joint (TMJ) bony ankylosis in a sheep model.

METHODS

Six sheep were used for the induction of bony ankylosis of TMJ. We performed a condylar fracture, excision of the lateral 2/3 disc and serious injury to the glenoid fossa to induce bony ankylosis on the right TMJ. An isolated condylar fracture was performed on the left side. Two sheep were sacrificed at 1 month, 3 months, and 6 months after surgery, respectively. The specimens from the ankylosed joint and the condylar fracture were harvested for RNA extraction respectively. In this report (Part I), only the bony ankylosed samples were used for analysis of gene expressions. The specimens 1 month postoperatively were taken as the control, and the changes of expression of target genes over time were examined by real-time PCR.

RESULTS

mRNA expression of Wnt1, Wnt2b, Wnt3a, β-catenin, Sfrp1, Lrp6, Lef1, CyclinD1, and Runx2 was up-regulated at 3 and 6 months compared with 1 month. The expression of Wnt5a, Sox9, and Osterix was up-regulated with a peak at 3 months, and then fell back to the basal levels at 6 months. The expression of Ocn began to up-regulate until 6 month postoperatively.

CONCLUSION

Our findings suggested that Wnt signaling was involved in the formation of traumatic TMJ bony ankylosis and thus may be a potential therapeutic target for the treatment of the disease in the future.

Decreased Osteogenesis in Stromal Cells from Radiolucent Zone of Human TMJ Ankylosis

We previously hypothesized that the development of traumatic temporomandibular joint (TMJ) ankylosis was similar to that of hypertrophic non-union. Besides similarities in etiology, hypertrophic bone stumps, and long-term development, the radiolucent zone, frequently located in the ankylosed bone, is another common feature. In this study, we demonstrated that the radiolucent zone also contained multilineage potential cells (RZs, radiolucent-zone-related cells) as the non-union tissues. RZs were characterized and compared with mandibular bone marrow stem cells (BMSCs) by analysis of MSC-related markers, colony-forming-unit assays, multipotential differentiation assays, alkaline phosphatase (ALP) activity assays, and cell transplantation in vivo. Both cell types were positive for CD105, CD166, and Stro-1 expression, negative for CD34 and CD45 expression, and exhibited osteogenic, adipogenic, and chondrogenic differentiation potentials. However, compared with mandibular BMSCs, RZs showed lower colony-forming-unit abilities and proliferation rates. The mineralization and bone-forming ability of RZs was weaker than that of mandibular BMSCs, with Runx2 and ALP mRNA expression and ALP activity significantly lower in RZs. All these results suggest that RZs possess the properties of MSCs but lower proliferation and osteogenic differentiation capacity similar to that of stromal cells in hypertrophic non-union tissues.

Distraction osteogenesis combined with tissue-engineered cartilage in the reconstruction of condylar osteochondral defect

PURPOSE

Surgical rehabilitation of condylar osteochondral defect remains a challenge for surgeons. The aim of this study was to explore the feasibility of combining distraction osteogenesis with tissue-engineered cartilage in the reconstruction of condylar osteochondral defect.

MATERIALS AND METHODS

A condylar defect model was established in 18 goats that were randomly divided into 2 groups: the experimental group and the control group. Mandibular ramus osteotomies were performed and distractors were implanted in all animals. The mixture of chondrocytes and Pluronic F-127 (Sigma-Aldrich, St Louis, MO) was injected on the notched surface of a transport disc in the experimental group, whereas a scaffold without cells was transplanted into the control group. After a 5-day latency period, distraction was activated at a rate of 0.5 mm twice per day for 15 days. The goats were killed at the end of the fourth, eighth, or twelfth week in the consolidation period. Specimens were harvested and macroscopic evaluation, as well as Masson trichrome and immunohistochemical staining, were performed to compare the results between the 2 groups.

RESULTS

Osteogenesis was found in all animals with no evidence of infection. Condyle-like structures were formed at the upper end of the transport segment in all animals. The neocondylar surface was covered with a layer of smooth lustrous fibrocartilage in the experimental group. Collagen was shown in the reparative tissue by Masson trichrome staining. Immunohistochemistry staining indicated that type II collagen was positive, whereas type I collagen was negative on the neocondylar surface in the experimental group. No cartilage-like tissue was seen, but fibrous tissue was identified at the bony surface in the control group. In the experimental group, immunofluorescent semiquantitative analysis showed that the positive rate of type II collagen was 1.62% ± 0.53% after the fourth week of consolidation, and it increased to 12.39% ± 3.27% after the twelfth week. There was a significant difference in the expression of type II collagen between the goats examined after the fourth week, and those examined after the twelfth week.

CONCLUSION

The combination of distraction osteogenesis with tissue-engineered cartilage is an ideal alternative in the reconstruction of condylar osteochondral defect. By use of this method, the simultaneous rehabilitation and regeneration of condylar bone and cartilage were achieved.

An experimental study on reconstruction of the condyle of the temporomandibular joint using free autogenous costal perichondrial grafts in rabbits

OBJECTIVE

The purpose of this study was to develop a new method to regenerate articular cartilage of the temporomandibular joint (TMJ) by transplantation of free autogenous costal perichondrium (PC).

STUDY DESIGN

In the study, 50 adult rabbits received the operation. For the surgery in the test group, the rabbits were randomly matched in pairs within the group and underwent the surgery of cross transplantation of costal PC after trimming the articular surface of the condyle. Operations were carried out in the same way in the experimental group except for PC transplantation. Instead, the suture was stitched in stratified order in the control group. Examination methods included observation of sections under the microscope, observation of specimens under the electron microscope, proliferating cell nuclear antigen (PCNA) staining, and biochemical analysis of glucuronic acid (GA) content and collagen content. The results of different groups were compared with ANOVA.

RESULTS

The transplanted homologous PC escaped observable immune repulsion so that it could survive to form new joint cartilage with approximately normal tissue structure and biochemical constitution. The reproduction process was similar to the normal one, but was prolonged a little. At the later stage, the degeneration and calcification in the basal layer increased. However, because of its limited scope, no apparent effect on cartilage growth and function was observed.

CONCLUSIONS

Homologous xenografting of free costal PC will not result in an apparent immunorejection of the host. Instead, the grafts can maintain their existence by obtaining nutrition from surrounding tissues and regenerate cartilage tissue.

Morphological evaluation of temporomandibular joint after open and closed treatment of type B diacapsular condylar fractures in sheep

The incidence of diacapsular fracture of the mandibular condyle (DFMC) has increased in recent years. However, the specific modality of treatment which would provide maximum benefit and good results for adult patients of DFMC has been controversial. To evaluate and compare morphological changes of temporomandibular joint (TMJ) after open and closed treatments for DFMC, a sheep model of a type B DFMC was created by osteotomy. Eight sheep models of type B DFMC were randomly divided into 2 groups to receive closed treatment (Group 1) and open reduction and internal fixation (ORIF, Group 2), respectively, and morphological changes of TMJ were scored according to the radiological and anatomical criteria of scoring and compared between the 2 groups. Compared with Group 1 animals treated by the closed method, Group 2 animals treated with ORIF received significantly lower scores for morphological changes 12 weeks after treatment. We conclude that ORIF is more efficient than the closed functional treatment in restoring morphology of TMJ to treat type B DFMC.