Stabilization of sacroiliac luxation in 40 cats using screws inserted in lag fashion

To (1) identify prognostic indicators for stability after stabilization of sacroiliac luxation with screws inserted in lag fashion and (2) report dorsoventral dimensions of the sacrum in cats.

Multicenter retrospective study.

Cats (n=40) with sacroiliac luxation.

Case records and radiographs of cats presented at the Queen's Veterinary School Hospital Cambridge and the Royal Veterinary College Hatfield for screw fixation of sacroiliac luxation were reviewed. Dorsoventral dimensions of 15 feline cadaveric sacral bodies were measured to identify the appropriate implant size for use in fixation with screws inserted in lag fashion.

Of 40 cats, 13 had left, 14 right, and 13 bilateral sacroiliac luxations. Of 48 screws analyzed, 42 (87.5%) were placed within the sacral body or exited ventrally and 6 (12.5%) were considered malpositioned. Screw purchase within the sacrum was statistically different between unstable and stable repairs (P=.001). Using confidence intervals for screw length within the sacrum and effect on stability, the lowest screw depth that contained 95% of the screws that did not loosen was approximately 60% of the sacral width. Mean dorsoventral sacral dimension at its narrowest point was 5.9+/-1.14 mm. There was no significant difference in the incidence of implant loosening between those luxations that were 100% reduced and those that were <100% reduced (P=.7837).

Screw purchase within the feline sacrum of at least 60% of the sacral width significantly reduces the risk of loosening.

Screw placement to a depth of 60% of the width of the feline sacrum is recommended.