Histologic and biochemical assessments on experimentally induced disk displacement of the craniomandibular joints.

兔颅下颌关节前盘移位。在椎间盘前移位7mm后，在椎间盘后组织的前外侧边缘放置一根缝线，固定在颧骨的眶下部分。于术后第2、第3、第5、第8和第24周评估术后变化。椎间盘移位在第2周和第3周引起髁突关节软骨肥大，第5周发生椎间盘穿孔。随后发现退行性关节炎改变。然后，我们在实验椎间盘移位手术后的第2周和第3周设计了二次椎间盘复位手术的周期。因此，在第2周进行二次椎间盘复位的动物显示软骨层肥大和关节炎改变的恢复。然而，第3周的二次手术没有恢复，但软骨出现进行性关节炎改变。其变化与动物髁相似，无需二次手术。这些结果表明椎间盘复位手术在治疗前椎间盘移位时有一定的局限性。本项目包括另一项与下颌髁骨折有关的动物实验。对青少年和成年家兔髁进行人工旋转脱位，观察骨折块愈合情况。青春期动物的骨折显示完全愈合，无论髁的脱位角度如何。另一方面，在成年髁旋转脱位的动物中，骨折碎片的愈合延迟和不完全。这些结果表明，对于成人患者的髁突骨折，开放复位是可取的。这一现象已被持续研究，并评估了断裂部位的酶活性。

Anterior disk displacement was induced in the craniomandibular joint of the rabbits. A sutured thread was placed at the antero-lateral margin of retrodiscal tissue and fixed to infra-orbital portion of zygoma after 7mm anterior displacement of the disk. Postoperative changes were assessed at the 2nd, 3rd, 5th, 8th, and 24th week. Disk displacement induced hypertrophy of articular cartilage of the condyle at the 2nd and 3rd week, then developed disk perforation at the 5th week. Subsequently, degenerative arthritic changes were noted. Then, we devised the period of the secondary disk repositioning surgery at the 2nd and 3rd week after experimental disk displacement procedure. Consequently, animals that underwent secondary disk repositioning at the 2nd week showed recovery from hypertrophy and arthritic changes in the cartilage layer. However, secondary operation at the 3rd week showed no recovery, but progressive arthritic changes were noted in the cartilage. Their changes resembled animal condyles without secondary operation. These results indicated a limitation period of the application of disk repositioning procedure for the condition of anterior disk displacement.This project includes another animal experiment relating to mandibular condyle fracture. An artificial rotational dislocation was performed on condyle of adolescent and adult rabbits, then healing process of the fractured fragments were observed. Fractures in the adolescent animals showed complete healing, regardless dislocation angle of the condyle. On the other hand, delayed and incomplete healing of the fractured fragments were noted among adult animals with rotational dislocation of the condyle. These results suggested that open reduction was advocated for condylar fracture in human adults patients. This phenomenon has been continuously investigated with the assessments for enzymatic activities at the fracture site.