Herford Alan S, Hoffman Robert, Demirdji Samuel, Boyne Philip J, Caruso Joseph M, Leggitt V Leroy, Vega Luis
Department of Oral and Maxillofacial Surgery, Loma Linda University, CA 92350, USA.
J Oral Maxillofac Surg. 2005 Jun;63(6):775-85. doi: 10.1016/j.joms.2005.02.013.
Mandibular advancement is a commonly performed surgical procedure for the treatment of mandibular hypoplasia. With the increased use of rigid fixation, there has been a decrease in the amount of relapse but an increase in the amount of force transmitted to the condyles. Gradual advancement of the mandible by distraction osteogenesis slowly overcomes the soft-tissue envelope and may decrease the amount of force exerted on the condyles. The purpose of this study was to develop an animal model to measure the magnitude of pressure associated with immediate versus gradual mandibular advancement.
A 2.0-mm pressure transducer was placed in the superior joint space in 2 miniature pigs. In the first animal, immediate advancement of the mandible with rigid fixation was performed. The synovial fluid hydrostatic pressures were measured prior to surgery and postoperatively. A second animal underwent gradual advancement with distraction osteogenesis. The synovial fluid hydrostatic pressures were measured prior to and after each activation of the distraction device. The condyles were examined radiographically and microscopically.
The superior joint space fluid pressures increased and remained elevated over a 5-week period after immediate advancement. In the gradually advanced mandible, the pressures were elevated but returned to near baseline prior to the activation the following day.
This animal model is useful to directly measure the pressure that is exerted on the condyle. This will allow further studies to compare methods for mandibular advancement. It is likely that gradual advancement of the mandible by distraction osteogenesis produces less force and causes less condylar resorption than large mandibular advancement stabilized with rigid fixation.
下颌前徙是治疗下颌发育不全常用的外科手术。随着坚固内固定的更多应用，复发量减少，但传递至髁突的力量增加。牵张成骨使下颌逐渐前徙可缓慢克服软组织包膜，并可能减少作用于髁突的力量。本研究的目的是建立一种动物模型，以测量与即刻和逐渐下颌前徙相关的压力大小。
在2只小型猪的上关节腔放置一个2.0毫米的压力传感器。第一只动物进行坚固内固定的下颌即刻前徙。在手术前和术后测量滑液静水压。第二只动物通过牵张成骨进行逐渐前徙。在每次激活牵张装置之前和之后测量滑液静水压。对髁突进行影像学和显微镜检查。
即刻前徙后，上关节腔液压力升高，并在5周内持续升高。在逐渐前徙的下颌中，压力升高，但在第二天激活之前恢复到接近基线水平。
这种动物模型有助于直接测量作用于髁突的压力。这将使进一步的研究能够比较下颌前徙的方法。与采用坚固内固定稳定的大下颌前徙相比，牵张成骨使下颌逐渐前徙可能产生的力量较小，导致的髁突吸收也较少。
