Microscopic changes in the condyle and disc in response to distraction osteogenesis of the minipig mandible.

PURPOSE: Unilateral mandibular distraction osteogenesis (DO) has been shown to cause gross changes in the mandibular condyle and articular disc. The purpose of this study was to correlate histologic findings with these gross changes in a minipig distraction model. MATERIALS AND METHODS: Semiburied distractors were placed via submandibular incisions in 15 minipigs. Two unoperated animals served as controls. The protocol consisted of 0-day latency and rates of 1, 2, or 4 mm/day for a 12-mm gap. After the minipigs were killed (at 0, 24, or 90 days), ipsilateral and contralateral condyles and discs were harvested, decalcified, prepared for standard paraffin embedding, and evaluated to determine changes in 1) morphology and thickness of the articular cartilage and subchondral bone and 2) morphology of the disc. RESULTS: In control animals, there were no degenerative changes in the articular cartilage and underlying condylar bone; there were no significant differences in the mean articular cartilage thickness. The temporomandibular joint discs were normal. In experimental animals, distracted condyles showed increasing degenerative changes and mean articular cartilage thickness as the DO rate increased. The discs were thinner. These changes were present, but to a lesser degree, in the contralateral condyles. After 90 days, degenerative changes in the condyles and discs were reduced, after remodeling, except in the 4 mm/day DO group. CONCLUSIONS: Histologic changes in the condyles and temporomandibular joint discs in response to mandibular DO correlated with previously reported gross changes. These changes were greater at higher distraction rates and remodeling back to normal occurred in mandibular condyles distracted at 1 mm/day.     

Changes in the condyle and disc in response to distraction osteogenesis of the minipig mandible.

PURPOSE: Distraction osteogenesis (DO) is a commonly used technique for mandibular lengthening, but changes in the temporomandibular joint have not been well documented. The purpose of this study was to evaluate the effect of DO, at varying rates, on the mandibular condyle and articular disc. MATERIALS AND METHODS: Semiburied distractors were placed via submandibular incisions in 15 minipigs. Two unoperated animals served as controls. The protocol consisted of 0 day latency and rates of 1, 2, or 4 mm/d for a 12-mm gap. After the animals were killed (0, 24, or 90 days), ipsilateral and contralateral condyles and discs were harvested and evaluated to determine changes in 1) condylar form and size, 2) condylar surface, and 3) the articular disc. RESULTS: Articular surfaces of the condyles in control animals were smooth, with no irregularities or erosions. In animals undergoing distraction, ipsilateral condyles showed increasing changes in morphology and AP dimension, and surface contour irregularities as the DO rate increased. These changes were present, but to a lesser degree, in the contralateral condyles. Articular discs of both ipsilateral and contralateral sides showed variable thinning at the medial aspect at end DO. After 90 days, changes in the condyles and discs were reduced by remodeling except in the 4 mm/d DO groups. CONCLUSIONS: Results of this preliminary study indicate that gross changes occur in condyles and discs after unilateral mandibular DO. These changes are more severe at faster distraction rates (4 mm/d) and tend to resolve during neutral fixation when a rate of 1 mm/d is used.     

Histomorphometric analysis of cartilage and subchondral bone in mandibular condyles of young human adults at autopsy

After demineralization, sagittal sections were made from the lateral, the central and the medial parts of 33 mandibular condyles from people aged 20 to 36 years, and studied for undifferentiated mesenchymal (UM) cells, cartilage and subchondral bone, the thickness of which were measured. Two condyles showed a continuous layer of UM cells extending all over. In 13 condyles, UM cells were absent; 18 condyles showed variability in UM cell occurrence in one or more out of the nine standardized areas. In 14 condyles, non-hypertrophic cartilage was present, 10 condyles showed hypertrophic cartilage and in nine condyles hyperplastic cartilage. Hyperplastic cartilage was associated with minimal numbers of UM cells. In combination with hypertrophic cartilage the UM cell layer appeared less irregular. Of nine condyles with incongruence of the cartilage-bone interface and the articular surface, seven showed hyperplastic cartilage. Six out of these seven were free of bony changes. A negative correlation was found between the presence of UM cells and the condylar-cartilage thickness (p less than 0.05). These results suggest that condylar changes are initiated by alterations in the cartilage and that changes in the bone are secondary.     

颞下颌关节侧向咬合位与对刃位薄层塑化断面对照研究

目的:对比分析下颌对刃位、侧向咬合位颞下颌关节的运动解剖形态,为颞下颌关节病变提供解剖依据。方法:将8例新鲜尸头摆置成对刃位5例、下颌侧向咬合位3例,以颞下颌关节为中心,切割成8cm×8cm×10cm的标本块,利用生物塑化技术,制成斜矢状位、斜冠状位、轴位塑化断层标本共16套。下颌侧向咬合位工作侧、非工作侧关节形态改变与对刃位相对照。结果:下颌侧向咬合位工作侧,髁突在关节窝内向后、向上、向外移位,关节盘位置无变化,关节盘双板及后带受压;非工作侧,髁突向下、向前、向内侧移位,关节盘后带位置向下移位,无前移位,关节盘中带外侧位居上下关节面之间,明显受压变薄。结论:关节盘并非随髁突作同步同向运动。关节盘在髁突作滑动运动时发生移位;当转动运动、滑动运动复合出现时,关节盘发生移位;而在关节窝内发生的转动运动,关节盘不发生移位。     

TMJ development and growth require primary cilia function

Primary cilia regulate limb and axial skeletal formation and hedgehog signaling, but their roles in temporomandibular joint (TMJ) development are unknown. Thus, we created conditional mouse mutants deficient in ciliary transport protein Kif3a in cartilage. In post-natal wild-type mice, primary cilia were occasionally observed on the superior, inferior, or lateral side of condylar cells. Cilia were barely detectable in mutant chondrocytes but were evident in surrounding tissues, attesting to the specificity of chondrocyte Kif3a ablation. Mutant condyles from 3-month-old mice were narrow and flat along their antero-posterior and medio-lateral axes, were often fused with the articular disc, and displayed an irregular bony surface. The polymorphic layer in P15 mutants contained fewer Sox9-expressing chondroprogenitor cells because of reduced mitotic activity, and newly differentiated chondrocytes underwent precocious hypertrophic enlargement accompanied by early activation of Indian hedgehog (Ihh). Interestingly, there was excessive intramembranous ossification along the perichondrium, accompanied by local expression of the hedgehog receptor Patched-1 and up-regulation of Osterix and Collagen I. In summary, Kif3a and primary cilia are required for coordination of chondrocyte maturation, intramembranous bone formation, and chondrogenic condylar growth. Defects in these processes in Kif3a condylar cartilage are likely to reflect abnormal hedgehog signaling topography and dysfunction.     

生长期山羊囊内骨折复位术中保留髁突软骨的重要性及组织学研究

目的：通过组织学观察,探讨髁突囊内骨折内固定术中保留和切除髁突软骨对髁突生长发育的影响。方法：6个月龄山羊12只,随机分为实验组（n=8）和对照组（n=4）。实验组双侧髁突造成囊内骨折并同期行手术复位固定．一侧保留髁突软骨,另一侧切除髁突软骨。术后3个月、6个月处死动物,切取髁突标本行石蜡切片和硬组织切片观察骨折愈合和髁突生长情况。结果：实验组髁突骨折愈合良好,钛板被新生骨组织覆盖;HE染色显示．保留髁突软骨组,髁突软骨结构清晰,与正常对照髁突相同,软骨成骨活跃,髁突生长发育正常;切除髁突软骨组,髁突软骨层消失,表面为成熟的骨细胞覆盖,直接与关节盘的纤维组织相连,新生骨组织少见：硬组织切片显示,钛板与骨组织直接结合．未见组织渗出和排异反应。结论：手术复位髁突囊内骨折时保留髁突软骨,不会影响髁突的生长发育;损伤髁突软骨．会造成髁突与关节盘黏连．引起髁突生长发育障碍。     

Histologic examination of the temporomandibular joint after mandibular advancement with and without rigid fixation: An experimental investigation in adult Macaca mulatta

This study evaluated the histologic response of the temporomandibular joint (TMJ) following mandibular advancement using rigid and nonrigid fixation in monkeys. Twelve adult female rhesus monkeys underwent sagittal ramus osteotomies with advancement. Six of them were placed into maxillomandibular fixation (MMF); six underwent bicortical bone-screw fixation without MMF. Changes in condylar position were quantified using lateral cephalograms with the aid of bone markers. The animals were killed at 6 weeks and the TMJs were prepared for histologic analysis. Three measures of condylar cartilage thickness were obtained for each animal and were correlated to changes in position of the condyle. Animals who underwent MMF showed a tendency for anterior movement of the condyles; animals who underwent rigid fixation showed a tendency for posterior condylar position. Thicker cartilage layers were found in the MMF animals. Animals who had posterior displacement of the condyles showed evidence of resorption of the posterior surface of the condyle and anterior surface of the postglenoid spine. There was a significant correlation between a change in the horizontal position of the condyle and the thickness of the posterior aspect of the condylar cartilage. The results of this study indicate that alterations in condylar position may induce remodeling changes within the TMJ.     

Histologic examination of the temporomandibular joint after mandibular advancement with and without rigid fixation: an experimental investigation in adult Macaca mulatta

This study evaluated the histologic response of the temporomandibular joint (TMJ) following mandibular advancement using rigid and nonrigid fixation in monkeys. Twelve adult female rhesus monkeys underwent sagittal ramus osteotomies with advancement. Six of them were placed into maxillomandibular fixation (MMF); six underwent bicortical bone-screw fixation without MMF. Changes in condylar position were quantified using lateral cephalograms with the aid of bone markers. The animals were killed at 6 weeks and the TMJs were prepared for histologic analysis. Three measures of condylar cartilage thickness were obtained for each animal and were correlated to changes in position of the condyle. Animals who underwent MMF showed a tendency for anterior movement of the condyles; animals who underwent rigid fixation showed a tendency for posterior condylar position. Thicker cartilage layers were found in the MMF animals. Animals who had posterior displacement of the condyles showed evidence of resorption of the posterior surface of the condyle and anterior surface of the postglenoid spine. There was a significant correlation between a change in the horizontal position of the condyle and the thickness of the posterior aspect of the condylar cartilage. The results of this study indicate that alterations in condylar position may induce remodeling changes within the TMJ.     

下颌前伸后大鼠颞下颌关节盘的组织学和组织化学研究

应用组织学和组织化学的方法，对幼年ＳＤ雄性大鼠功能矫形前伸下颌后颞下颌关节盘的变化进行研究。结果显示；功能矫形前伸下颌后，关节盘胶原纤维束排列致密，前后向排列明显，纤维束粗大，关节盘后分软骨细胞增多，糖胺多糖及强硫酸化氨基己糖含量增加；未发现关节盘有病理性改变。提示关节盘随的翼外肌张胃衣髁突压     

The mandibular condyle in juvenile chronic arthritis patients with mandibular hypoplasia: a clinical and histological study

In 12 JCA patients with severe mandibular hypoplasia, who all strongly demanded early treatment, 21 mandibular condyles were replaced by costochondral grafts. All of them had radiographic morphological changes in the mandibular condyles with varying degrees of destruction of the articular cartilages. Severe pathological changes in the lower joint compartments were consistently observed at surgery. Hence, the lower joint compartments were obstructed with granulomatous tissue, whereas the upper compartments were without macroscopic pathological changes. These findings indicated a polarized involvement of the temporomandibular joint (TMJ) in juvenile chronic arthritis (JCA). The extent of condylar articular surface destruction at histological examination varied from focal to total cartilage destruction. Inflammation of the subchondral bone marrow was a frequent finding. In spite of considerable arthritic destruction of the condyles, only one patient had TMJ pain, while a restricted mouth opening capacity was a more frequent finding. Thus, TMJ pain did not seem to constitute a reliable symptom of serious arthritic destruction of the mandibular condyle.     

髁突矢状骨折继发颞下颌关节强直31例临床分析

目的:探讨髁突矢状骨折继发创伤性颞下颌关节强直的临床特点。方法:回顾性分析2001～2010年武汉大学口腔医院口腔颌面外科收治的31例、48侧继发于髁突矢状骨折的颞下颌关节强直患者的相关临床资料。结果:31例颞下颌关节强直患者平均外伤年龄15.6岁,其中23例(74.2%)外伤年龄小于16岁。病程3月~20年,平均病程6.5年。42侧强直关节的关节盘发生移位,6侧强直关节的关节盘完全破坏。强直关节标本镜下观察:内侧髁突骨折块发生废用萎缩性改变,外侧骨球区见软骨细胞呈灶性增生成骨,关节盘纤维结构紊乱、玻璃样变性。结论:青少年髁突矢状骨折易发生颞下颌关节强直,关节盘的移位损伤是颞下颌关节强直发生的重要条件。创伤性颞下颌关节强直首先发生在关节外侧,融合骨赘的组织病理学表现为软骨化生、成骨。     

状突冷冻再植后颞下颌关节改变的实验研究

目的 :为颞下颌关节肿瘤的治疗及关节重建提供一定的理论依据。材料和方法 :对 16只未成年日本大耳白兔的右侧髁状突施行了冷冻再植术。术后所有动物正常存活 ,第 2、4、8、12周分别处死 4只动物。采用常规组织学、扫描电镜及微血管显像等对髁状突和关节盘进行观察。结果 :组织学检查发现随着血供逐渐恢复 ,失去活力的骨被新骨“爬行替代” ,而髁状突软骨的结构未完全恢复 ;扫描电镜检查证明了关节盘下腔面的表面结构基本正常 ,实验后期髁状突的表面较光滑 ,但无明显胶冻样物 ;微血管显像显示冷冻再植髁状突逐渐再血管化。 16只动物中有 3只的手术侧颞下颌关节发生轻度粘连。结论这些结果证明 :髁状突冷冻再植在颞下颌关节重建时有应用的可行性。     

Effects of estrogen on the condylar cartilage of the rat mandible in organ culture.

PURPOSE: The effects of estrogen on bone have been well documented. However, very little is known about the regulatory role of estrogen on cartilage and, in particular, the secondary cartilage of the mandibular condyle. The aims of this study were to determine whether estrogen receptors are present in the condylar cartilage of the rat mandible and to assess the effect of varying 17beta-estradiol (E2) concentrations on the proteoglycan content of this tissue. MATERIALS AND METHODS: Mandibular condyles of 16 female Sprague-Dawley rats were resected. Eighteen of these condyles were divided into three groups and the condylar cartilage was removed and placed in organ culture for 4 days with media containing different concentrations of estrogen: 10(-11) mol/L, 10(-8) mol/L, and 10(-6) mol/L. The cartilage then was analyzed for proteoglycan content along with six specimens not passed through the organ culture. Six intact mandibular condyles also were resected and placed in organ culture with the same varying E2 concentrations, and the condylar cartilage was analyzed for estrogen receptors along with two condyles not passed through the culture system. RESULTS: Estrogen receptors were evenly distributed within the chondroblastic and hypertrophic zones in the control group and the group with 10(-11) mol/L E2. With E2 concentrations of 10(-8) mol/L and 10(-6) mol/L, there was a qualitative decrease in hypertrophic chondroblasts, thickness of the condylar cartilage, and a significant decrease in proteoglycan content. CONCLUSIONS: This study shows the presence of estrogen receptors in the secondary cartilage of the rat mandibular condyle. Estrogen has the potential to cause a decrease in extracellular matrix and thickness of this cartilage.     

A clinical investigation on disc displacement in sagittal fracture of the mandibular condyle and its association with TMJ ankylosis development

This retrospective study evaluated the potential influence of the sagittal fracture pattern and articular disc displacement on the development of temporomandibular joint (TMJ) ankylosis. 33 sagittal fractures of mandibular condyles (SFMCs) in 19 patients were treated conservatively and were divided into non-ankylosis and ankylosis groups based on their prognosis. Using computed tomography (CT) images, the SFMCs were classified into types I, II and III, and the displacement of the articular disc was investigated using magnetic resonance imaging (MRI). There were 19 (58%) SFMCs in the non-ankylosis group: 5 were type I SFMCs, which did not show any disc displacement; the other 14 were type II SFMCs, which included 5 cases without disc displacement and 9 cases with disc displacement. In the non-ankylosis group, the lateral poles were completely or incompletely covered by the discs. There were 14 (42%) SFMCs in the ankylosis group, all of which were type III SFMCs showing disc displacement, and the lateral poles in these cases were not covered by the discs. This investigation confirmed that the disc position was highly associated with the position of the fractured fragment and that some SFMC patterns, especially type III SFMCs, indicated a high risk of TMJ ankylosis.     

Study of the tidemark in human mandibular condylar cartilage

Objectives

The tidemark is the junction of mature calcified and uncalcified articular cartilage. Metabolic activity in the tidemark area makes this structure important in articular remodelling and osteoarthrosis. However, detailed study of the tidemark on the mandibular condyle has been limited. This study investigated the functional significance of the tidemark in the mandibular condyle with respect to load-bearing.

Design

The study sample included 87 healthy human mandibular condyles from subjects aged 14–76 years. The morphology, number, and thickness of tidemarks were observed and measured in the anterior, superior, and posterior regions. Five additional mandibular condyles were evaluated by scanning electron microscopy.

Results

The tidemark appeared in 80 specimens as a dense wavy line at the interface between the calcified and hypertrophic layers of the condylar cartilage. Scanning electron microscopy showed a highly wavy tidemark surface in the load-bearing areas and a relatively flat and smooth surface in the non-load-bearing areas. The thickness of the tidemark in the load-bearing areas was significantly higher than that in the non-load-bearing areas (P = 0.003).

Conclusion

The results of this study demonstrated that the thickness of the tidemark was related to load-bearing on the articular surface.     

High condylar shave of the temporomandibular joint with preservation of the articular soft tissue cover: an experimental study on rabbits

The high condylar shave has the disadvantage of removing the articular soft tissue cover together with the underlying condylar bone. In an attempt to overcome this disadvantage, we elevated the articular soft tissue cover, shaved the condylar head, and replaced the articular soft tissue cover in its original position in nine adult rabbit temporomandibular joints. On the contralateral joints, the same amount of bone was shaved together with the articular soft tissue cover. The rabbits were killed after 3 months, and the condyles were macroscopically and histologically evaluated. All condyles were covered with an articular soft tissue layer in the area operated on. This surface was smoother when the articular soft tissue cover was preserved. Histologically, the subarticular layer of cartilage cells was continuous in the joints with preservation of the articular soft tissue cover but was frequently interrupted in the joints where this cover was removed. The incision made in the posterior part of the articular surface for elevating the articular soft tissue cover frequently caused a deformity of the condyle and an interruption of the subarticular layer of cartilage. The results suggest that preservation of the articular soft tissue cover on the mandibular condyle might be one way to improve the postoperative morphology after high condylar shave. The technique in its present state has obvious drawbacks and should be further refined before it is considered for clinical application.     

Histological evaluation of condylar hyperplasia model of rabbit following distraction osteogenesis of the condylar neck

Summary Condylar hyperplasia is the excessive unilateral growth of mandibular leading to facial asymmetry, occlusal disturbance, joint pain and dysfunction. The aim of this study is to evaluate the histological presence of temporomandibular joint in model of condylar hyperplasia by lengthening unilateral condylar neck of distraction osteogenesis. An extra oral distractor was employed to achieve unilateral condylar neck distraction (1·0 mm daily for 7 days). The experimental condylar necks were elongated by 7 mm compared to the contralateral. Eleven adult white rabbits were used. Eight rabbits were, respectively, sacrificed after the post‐distraction period (4 or 8 weeks). All animals were evaluated clinically and histomorphometrically. The condyles radiologically showed remodelling, flattening and sclerosis. In 4‐week group, thinning of the cartilage was evident, and the trabeculae were long, not multiply connected. A thin, dense fibrous layer covered all over the surface of cartilage. In 8‐week group, the cartilaginous layer was similar to thickness of the normal cartilage, but still thinner than control. However, the fibrous layers covering condyle manifested slight degenerative changes, and even depressions and erosions were seen in the cartilage and subchondral bone. The trabeculae showed denser and multiply connected. In 8‐week group, the cartilaginous thickness of surgical condyles was significantly thinner than the contralateral. This study indicates that unilateral distraction of condylar neck loads the condyles asymmetrically. Asymmetrical loads affect more on the surgical condyles than the contralateral, and after 8 weeks of the post‐distraction, condyle could recover from asymmetrical loads in some degree.     

Histochemistry of the foetal human temporomandibular joint articular disc

The human temporomandibular joint (TMJ) develops from mesenchymal cells that form condensations appearing as condylar and temporal blastema which give rise to the respective anterior and posterior regions of the TMJ articular disc. Previous reports have shown the foetal disc to be avascular, with a high content of organized collagen fibres and a lesser content of elastic fibres. In this study, the articular discs from TMJs of a human foetus at age 22 weeks were evaluated. At this stage of intrauterine (i.u.) development, the disc was found to be a highly cellular, biconcave structure with a dense arrangement of collagen fibres. Cell density was not uniform, with increased density in the intermediate band relative to the anterior and posterior bands. In contrast to earlier reports, capillaries containing red blood cells were observed along the inferior surface of the disc. Immunohistochemical staining for proteoglycans and glycosaminoglycans (GAGS) revealed abundant chondroitin sulphate proteoglycan (CSPG) and hyaluronic acid in the disc while relatively little amounts of dermatan sulphate proteoglycan II (DSPGII) were found. No keratin sulphate proteoglycan (KSPG) was detectable. Foetal human TMJ articular discs at this age were found to have morphology and regional characteristics similar to adult discs.     

Regeneration of the mandibular condyle after unilateral condylectomy and myotomy of the masseter in lambs

We investigated the degree of regeneration of the mandibular condyle after unilateral condylectomy and myotomy of the masseter in growing lambs. Four 10-week-old lambs had unilateral condylectomy and myotomy of the superficial layer of the masseter on the right side, and were killed 3 months later. The joints were examined radiologically and histologically. All joints showed poor regeneration of the condylar head. In the medial plane there was partial condylar and articular cartilage reformation, but in the lateral plane there was neither condylar nor cartilaginous reformation. The articular cartilage of the temporal bone was thicker in the medial plane and the disc was thicker in the central plane, than in unoperated joints. We conclude that unilateral condylectomy and myotomy of the masseter in the growing period results in poor regeneration of the condyle.     

颞下颌关节骨关节病髁突组织细胞凋亡的研究

目的研究颞下颌关节骨关节病骸突组织中软骨细胞凋亡发生的特点,探讨细胞凋亡在颞下颌关节骨关节病发病机制中的作用。方法通过手术切除部分关节盘的方法建立颞下颌关节骨关节病动物模型,15 d-6个月内采用TUNEL法标记裸突各相应时段的凋亡细胞,结合相应组织学变化,观察、分析颞下颌关节骨关节病裸突组织中细胞凋亡发生的特点。结果关节盘损伤后软骨产生明显应激性修复增殖反应时,凋亡细胞主要集中于关节表面的纤维层中;随着关节软骨和骨组织不断改建,软骨组织中逐渐出现大量的细胞凋亡现象,主要发生于表面纤维层与增殖层,尤其集中在软骨细胞簇中;在软骨组织消耗严重时,浅表区域内的细胞凋亡现象逐渐减少,肥大钙化层中出现了较多的凋亡细胞。结论颞下颌关节骨关节病骸突软骨组织中存在过量凋亡的现象,软骨细胞异常增殖与过度凋亡导致软骨基质自身调节机制的破坏可能是骨关节病发生的重要原因之一。