Jingang An

Surgical induction of TMJ bony ankylosis in growing sheep and the role of injury severity of the glenoid fossa on the development of bony ankylosis.

OBJECTIVE The purpose of this paper is to summarize our experiences in creating an animal model of TMJ bony ankylosis based on 2 sequential experiments. METHODS Two sequential experiments were performed with the aim of creating a model of TMJ bony ankylosis. Seven growing sheep were used in the first experiment, in which 1 was served as a control animal. Condylar fracture with disc preservation was performed on the control side. On the contralateral side, condylar fracture, excision of the lateral 2/3 disc and injury to the glenoid fossa were performed to induce bony ankylosis. Three animals were sacrificed respectively at 3 and 6 months after surgery. In the second experiment, 7 growing sheep were used. The only difference of modeling between the 2 experiments was that more serious injury to the glenoid fossa was made in the ankylosis-induced side in experiment 2. Three, 2, and 2 animals were sacrificed respectively at 1, 3, and 6 months postoperatively. The TMJ complexes were examined by computed tomography (CT) and histological evaluation. RESULTS In experiment 1, only fibrous ankylosis was observed in the ankylosis-induced side both at 3 and 6 months postoperatively. In experiment 2, CT and histological evaluation showed that the outcomes of the ankylosis-induced side were fibrous-bony ankylosis, fibrous-bony ankylosis, and bony ankylosis respectively at 1, 3, and 6 months after surgery. CONCLUSION Through summarizing the differences of the modeling and the different outcomes in the 2 experiments, we concluded that severe damage to the glenoid fossa played an important role in the development of TMJ bony ankylosis.

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.

The relationship between mouth opening and computerized tomographic features of posttraumatic bony ankylosis of the temporomandibular joint

OBJECTIVE The purpose of this paper was to investigate the relationship between mouth opening and computerized tomography (CT) features in patients with bony ankylosis of the temporomandibular joint. STUDY DESIGN A series of morphologic parameters-the diameters of bony mass (D1), the width of bony fusion area (D2), the ratio of D2/D1, and the degree of calcification in bony fusion area (D3)-were measured by Mimics 10.0 software. Correlation analysis and stepwise multiple linear regression analysis were the statistical methods used. RESULTS Nine patients (23.68%) with bony fusion area fully calcified were completely unable to open their mouth, whereas 29 patients (76.32%) with bony fusion area calcified incompletely had a slight degree of mouth opening. No correlation was found between mouth opening and D1. A negative correlation was observed between mouth opening and D2 (r = -0.670; P < .01), between mouth opening and D2/D1 (r = -0.697; P < .01), and between mouth opening and D3 (r = -0.744; P < .01). Multiple stepwise regression analysis identified D2 and D3 as predictive factors of residual mouth opening. CONCLUSIONS D2 and D3 were independent factors affecting the mouth opening. The insufficient calcification of bony fusion area, which cannot fully limit the motion of ankylosed joint, may be an important cause of residual mouth opening in patients with complete bony ankylosis.

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.

Long-term evaluation of the stability of reconstructed condyles by transport distraction osteogenesis

This retrospective longitudinal study evaluated the long-term stability of reconstructed condyles by transport distraction osteogenesis of the mandibular ramus in patients with unilateral temporomandibular joint (TMJ) ankylosis. 7 patients were followed up for 16-92 months (mean 39.4 months). The mean age of the patients at the time of distraction was 22.9 years (range 7-44 years). Maximal mouth opening and panoramic radiographs were recorded preoperatively, at the time of device removal and several years after removal of distraction device. At follow-up, cone beam CT images of the TMJ were obtained to confirm the changes of the reconstructed condyle. Absolute height (Co-Inc) and relative height (Co-Inc/Co-Go) of the reconstructed condyle and the asymmetric difference ratio (AR) were examined to assess the changes of condylar height and mandibular symmetry. The mean maximal mouth opening was stable during the period of follow-up. The mean absolute height and relative height of the reconstructed condyle decreased significantly (P<0.05). Although no significant difference was found, the mandibular asymmetry difference ratio increased by 16.7%. These results suggested that the heights of reconstructed condyles were not stable in the long-term, and the mandible tended to be asymmetrical.

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.

Treatment of traumatic dislocation of the mandibular condyle into the cranial fossa: development of a probable treatment algorithm

This study summarizes our experience of treating three rare cases of traumatic superior dislocation of the mandibular condyle into the cranial fossa and provides a potential treatment algorithm. Between the years 2002 and 2012, three patients with traumatic superior dislocation of the mandibular condyle into the cranial fossa were admitted to our department. After evaluating the interval from injury to treatment, the associated facial injuries including neurological complications, and the computed tomography imaging findings, an individualized treatment plan was developed for each patient. One patient underwent closed reduction under general anaesthesia. Two patients underwent open reduction with craniotomy and glenoid fossa reconstruction. All three patients were followed up for 1 year. Mouth opening and occlusal function recovered well, but all patients had mandibular deviation during mouth opening. Closed reduction under general anaesthesia, open surgical reduction with craniotomy, and mandibular condylotomy are the three main treatment methods for traumatic superior dislocation of the mandibular condyle into the cranial fossa. The treatment method should be selected on the basis of the interval from injury to treatment, associated facial injuries including neurological complications, and computed tomography imaging findings.

Ankylosing spondylitis associated with bilateral ankylosis of the temporomandibular joint.

OBJECTIVE The objective of this study was to analyze the clinical and laboratory features, treatments, and prognosis of ankylosing spondylitis (AS) associated with bilateral temporomandibular joint ankylosis (TMJA). METHODS A PubMed search was conducted from 1966 to date, and the references of published studies were also checked to identify additional cases. Information from these reports and our report were compared and analyzed. RESULTS Published literature in the past 36 years, which included 8 cases, were reviewed. The mean (SD) age at diagnosis of AS and bilateral TMJA was 21.00 (6.35) and 32.50 (13.43) years, respectively. Ankylosis of cervical vertebra was described in all patients. Total alloplastic joints and artificial condyle replacements were also reported in recent years. The slices of ankylotic mass showed the marrow was infiltrated by eosinophilic granulocytes. CONCLUSION Evaluating temporomandibular joint (TMJ) function is strongly recommended in patients who have a long history of AS, particularly in cases involving cervical vertebrae disease.

Role of Bone Marrow Stromal Cells in Impaired Bone Repair from BRONJ Osseous Lesions.

Treatment of bisphosphonate-related osteonecrosis of the jaw (BRONJ) has posed significant challenges to maxillofacial surgeons because of the poor repair of BRONJ bone defects. Moreover, the pathological mechanisms remain unclear. Bone marrow stromal cells (BMSCs) play key roles during bone repair and bone regeneration. However, the activities of BMSCs derived from BRONJ lesions and the BRONJ lesion boundary, as well as the roles of BMSCs in BRONJ defect repair, are poorly defined. In this study, we found that BMSCs from the central area of the osteonecrotic BRONJ region (center-BRONJ BMSCs) and the peripheral area at the recommended debridement boundary (peri-BRONJ BMSCs) had decreased proliferative ability, self-renewal capacity, and multidifferentiation capacities compared with control BMSCs. Osteoclast-inducing ability was also impaired in BRONJ BMSCs. All of these results suggested that the decreased activities of BRONJ BMSCs, even the BMSCs derived from the BRONJ lesion boundary, might be an important factor leading to insufficient bone repair of BRONJ lesions. This study offers early stage evidence for the use of marrow stromal cells in the treatment of BRONJ.

Application of a computer-assisted surgical navigation system in temporomandibular joint ankylosis surgery: a retrospective study

This retrospective study evaluated the effect of surgical computer-assisted navigation in temporomandibular joint (TMJ) ankylosis gap arthroplasty. Eighteen patients (25 sides) with bony ankylosis who underwent surgical treatment under computer-assisted navigation (navigation group) from May 2011 to April 2013 were assessed, along with 19 such patients (25 sides) treated without computer-assisted navigation (non-navigation group) from March 2009 to April 2011. The navigation group patients underwent surgery with the preservation of ≥3mm bone thickness in the skull base and anterior wall of the external auditory canal. Postoperatively, computed tomography (CT) was used to measure the residual bone thickness in the skull base and anterior wall of the external auditory canal. Maximum mouth opening (MMO) changes were evaluated at >1 year of follow-up. Postoperative CT measurements showed that the lowest skull base thickness in the navigation group was significantly lower than that in the non-navigation group (3.86±1.95mm vs. 6.01±3.07mm, P=0.009). The lowest thicknesses of the anterior wall of the external auditory canal were similar in the two groups. Postoperative follow-up showed similar average MMO in the two groups. Therefore, with the navigation system, TMJ ankylosis gap arthroplasty can achieve more extensive removal of the ankylosed bone, at least towards the skull base, under the premise of ensuring a safety distance of 3mm.