title: Influence of distraction rates on the temporomandibular joint position and cartilage morphology in a rabbit model of mandibular lengthening.
abstract: OBJECTIVE
  Although various aspects of bone formation during distraction osteogenesis have been studied extensively, there are only limited experimental data concerning the influence of mandibular distraction rates on structural alterations in the temporomandibular joint (TMJ). In this study, a rabbit model of unilateral mandibular distraction was used to test the effects of various strain schedules on the position and morphology of the TMJ.
  
  
  METHODS
  Fifty-two immature white female rabbits were used. The distraction procedure was performed using physiologic (2,000 microstrains, 1 per day) and elevated strain magnitudes (20,000 microstrains, 1 per day), as well as high strain magnitudes (200,000 and 300,000 microstrains, 1 per day). The investigation of the TMJ included clinical, radiologic, and histologic aspects.
  
  
  RESULTS
  Clinical and radiologic examinations at the end of the distraction period showed no evidence of joint luxation even at maximal distraction rates. Histologic and ultrastructural analyses revealed a positive correlation between the degree of mechanical loading and the development of degenerative alterations in the cartilage. In samples distracted at hyperphysiologic strain magnitudes, all cartilaginous layers were reduced in the regions of the TMJ that had been exposed to the higher pressure forces. The fibrous layer became nearly completely destroyed.
  
  
  CONCLUSIONS
  These experimental data show that distraction schedules with single but hyperphysiologic loads may lead to degenerative or even early arthrotic changes in the condyle. These data support the principle that distraction protocols should be performed without extensive mechanical loading on the TMJ.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University of Münster, Münster, Germany. losler@uni-muenster.de
authors.forename: B
authors.initials: B
authors.lastname: Kruse-Lösler
authors.forename: U
authors.initials: U
authors.lastname: Meyer
authors.forename: C
authors.initials: C
authors.lastname: Flören
authors.forename: U
authors.initials: U
authors.lastname: Joos
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology*; D003799:Dental Stress Analysis; D005260:Female; D008334:Mandible / Q000601:surgery*; D008335:Mandibular Condyle / Q000473:pathology / Q000648:ultrastructure; D023421:Models, Animal; D019647:Oral Surgical Procedures / Q000009:adverse effects*; D019857:Osteogenesis, Distraction / Q000009:adverse effects*; D011817:Rabbits; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000209:etiology*