title: The temporomandibular joint of California sea lions (Zalophus californianus): part 2-osteoarthritic changes.
abstract: OBJECTIVE
  Following comprehensive characterization of the temporomandibular joint (TMJ) of the California sea lion, as well demonstrating that TMJ-osteoarthritis (OA) occurs in this species, the objective of this part of the investigation was to describe the macroscopic osteologic findings associated with TMJ-OA in a large museum collection of skull specimens.
  
  
  METHODS
  Museum skull specimens (n=497) of California sea lions were examined macroscopically according to defined criteria for the presence, severity, location and characteristics of TMJ-OA. The specimens, acquired from strandings, varied in age from young adults to mature adults.
  
  
  RESULTS
  Overall 63.5% of the specimens had findings consistent with TMJ-OA. Of these, 56.2% were from females 43.8% were from males. Moreover, 71.2% specimens were from mature adults and 28.8% from young adults. However, there was no significant association between age and sex with the presence or severity of TMJ-OA. The most prominent TMJ-OA changes were the presence of subchondral bone defects and abnormal porosity. The majority of the OA present at the mandibular head affected the entire articular surface. In contrast, the OA present on the mandibular fossa of the temporal bone was located primarily on the medial aspect (P<0.001).
  
  
  CONCLUSIONS
  The incidence of TMJ-OA in California sea lions is high and varies in severity. Although the significance of the high incidence of this disease in the California sea lion remains elusive, the occurrence and severity of TMJ-OA detected in this study may play an important role in the species' morbidity and mortality.
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. Electronic address: barzi@ucdavis.edu.
authors.forename: B
authors.initials: B
authors.lastname: Arzi
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Leale
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: N L
authors.initials: NL
authors.lastname: Sinai
authors.affiliation: Department of Population Health and Reproduction, School of Veterinary Medicine University of California, Davis, CA 95616, USA.
authors.forename: P H
authors.initials: PH
authors.lastname: Kass
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lin
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: F J M
authors.initials: FJ
authors.lastname: Verstraete
mesh_terms: D000818:Animals; D005260:Female; D015994:Incidence; D008297:Male; D010003:Osteoarthritis / Q000473:pathology / Q000662:veterinary*; D046070:Sea Lions; D013704:Temporomandibular Joint / Q000473:pathology*; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000473:pathology / Q000662:veterinary*
keywords: California sea lion; Osteoarthritis; Temporomandibular joint; Zalophus californianus