EFFECTS OF AGE AND LOCATION ON THE BIOMECHANICAL AND BIOCHEMICAL-PROPERTIES OF CANINE TRACHEAL RING CARTILAGE IN DOGS

Objective-To evaluate effects of age (immature vs adult) and location along the trachea on the biomechanical properties (via a tensile stres s relaxation rest) and biochemical properties (water content and total proteoglycan content) of canine tracheal ring cartilage. Sample popul ation-Entire trachea from 8 immature and 8 adult dogs. Procedure-A sec tion of each tracheal ring from 8 immature dogs (6 months old) and 8 a dult dogs (2 to 3 years old) was tested biomechanically (maximal stres s, equilibrium stress, equilibrium modulus, and percentage of relaxati on) and processed for biochemical analysis (water content and total pr oteoglycan content). Two rings from each trachea were prepared for his tologic analysis (H&E or safranin-O staining). Results-Biomechanical a nd biochemical parameters were not different between cervical and thor acic rings of either age group. Mean maximal stress, equilibrium stres s, and equilibrium modulus were significantly higher for adult, compar ed with immature, dogs. However, percentage of relaxation for adult do gs was significantly lower. Tracheal rings of adult dogs had a signifi cantly higher proteoglycan content and a significantly lower water con tent than did those of immature dogs. Water content and biomechanical parameters were significantly correlated, and proteoglycan content and biomechanical properties were significantly but weakly correlated. On histologic sectioning, a qualitative decrease in safranin-O staining in the rings of immature dogs also was observed. Conclusions and Clini cal Relevance-Biomechanical and biochemical properties of the canine t racheal ring cartilage are altered with age. However, location of the ring along the trachea did not affect these properties for either age group. Results lend support to the theory that proteoglycan content ha s some effect on tensile properties of tracheal rings and may explain increased compliance observed in rings from dogs with collapsed trache a.