Pressure profilometry of the lumbosacral disk in dogs

Objective To investigate the biomechanical behavior of the lumbosacral disk under compressive load in dogs, using pressure profilometry, and to invest igate the relationship between pressure profile features and background and disease variables. Sample Population-23 lumbosacral disks and adjacent vertebrae harvested fro m medium and large breed dogs. Procedure-A 1.3-mm unidirectional needle-mounted pressure transducer was in serted into the disk in a ventral-to-dorsal manner while the disk was loade d in compression by a materials testing machine. Withdrawal of the transduc er resulted in a pressure profile for cranial and lateral stress. Pressure profiles were analyzed, and relationships to age and gross evidence of dege neration were investigated. Results-There was a moderate positive correlation between age and degree of nuclear degeneration (r(s) = 0.420, P = 0.046), but no relationship betwee n age and mean nuclear pressure was detected. Mean nuclear pressure correla ted negatively with severity of degenerative changes in the nucleus pulposu s. Receiver operator characteristic curves to evaluate mean nuclear pressur e as a diagnostic test for nuclear degeneration revealed a sensitivity and specificity of 82 and 83%, respectively. In addition, age was moderately co rrelated with the magnitude of stress peaks (r(s), = -0.571, P = 0.004). St ress peaks were not related to the severity of nuclear degeneration. Conclusions and Clinical Relevance-Determination of the mean nuclear pressu re by disk profilometry provides information on the severity of lumbosacral disk degeneration with a high degree of sensitivity and specificity, The m agnitude of single stress peaks within the dorsal annulus fibrosus is corre lated with age and may not necessarily reflect advancing degeneration.