A comparison of the thermal properties of 2- and 3-fluted drills and the effects on bone cell viability and screw pull-out strength in an ovine model.

BACKGROUND: Drilling of bone is associated with an increase in temperature of the surrounding bone which may result in osteonecrosis. METHODS: In this study, cutting efficiency and thermal properties of one 2-fluted drill and two 3-fluted drills were determined in vitro using a porcine model. Drills were then used to create pilot holes in an in vivo ovine model to facilitate implantation of pedicle screws. The effect of the characteristic thermal profiles of each drill on cortical bone cell viability and screw pull-out strength was then assessed. FINDINGS: Cutting efficiencies of both 3-fluted designs were found to be greater than that of the 2-fluted drill, but this did not translate into a decrease in the maximum temperatures during drilling for both drills. Histologically, no empty osteocyte lacunae were seen at 2 or 4 weeks, suggesting that temperatures were not sufficiently high enough to induce thermonecrosis in the ovine tibia. No differences were found in the pull-out strength of the screws. INTERPRETATION: Both 2- and 3-fluted drills are currently in clinical use. Despite the theoretical advantage that 3-fluted drills possess over their 2-fluted counterparts, there is a lack of evidence in the literature in support of their use. In this study the observed increases in cutting efficiency of the 3-fluted drills tested did not translate into a reduction in heat generation or improvement in bone healing or screw fixation.

A retrospective study of daylily toxicosis in cats.

The Easter, Japanese, stargazer and tiger lilies (Lilium sp) are nephrotoxic to cats. This study examined risks posed to cats by the common daylily (Hemerocallis sp: H. dumortierei, H. fulvi, H. graminea, H. seiboldii) following ingestion. Records describing ingestion of Hemerocallis sp between January 1998 and June 2002 were reviewed for signalment, quantity ingested, clinical signs (onset, severity, duration), treatments administered, and outcome. Twenty-two cases of confirmed exposure resulting in toxicosis were evaluated. Cats that ingest daylilies are at risk for gastrointestinal distress and acute renal failure. Successful treatment can be accomplished with early decontamination and aggressive fluid therapy.