Eighty lumbar segments from 16 female sheep were used to investigate the effect of laminar decortication on the strength of the lamina during sublaminar wiring procedure. Sheep were 12-14 months old. Forty vertebrae from eight animals were decorticated before loading with sublaminar wire to failure, and 40 vertebrae from the remaining eight sheep were tested with the same procedure but intact. The effects of bone mineral density (BMD) and laminar dimensions on laminar strength in both decorticated and nondecorticated groups were also investigated. The failure force values of the laminae for decorticated and nondecorticated groups were 881.15 +/- 36.86 and 298.48 +/- 21.99 N, respectively (P < 0.001). There was a positive linear relationship between BMD and laminar strength in an intact lamina. In a decorticated lamina, no significant relationship existed between these variables. There was a negative linear relationship between mediolateral length of hemilamina and laminar strength in both intact and decorticated vertebra. Laminar strength after decortication was positively related to dorsoventral length of the remaining portion of the lamina. Decortication leads to a statistically significant decrease in laminar strength.