Sacroiliac Luxation in the Cat: Defining a Safe Corridor in the Dorsoventral Plane for Screw Insertion in Lag Fashion

Objective-To define a safe corridor in the dorsoventral plane within the feline sacral body for placement of screws inserted in lag fashion for repair of sacroiliac luxation.

Study Design-Anatomic study.

Sample Population-Frozen cadaveric feline sacra.

Methods-Feline sacra (n = 20) were used to perform a radiographic study to define a safe corridor to a depth of 66% of the sacral body width. Two drill start points (A and B) were evaluated. Dorsal exit from the safe corridor was considered unacceptable.

Results-Forty safe corridors were measured. The mean articular surface was 100 +/- 6.4 degrees from horizontal. Mean maximum, optimum, and minimum safe corridor drill angles from drill point A were 107 +/- 6.8 degrees, 97 +/- 6.9 degrees, and 87 +/- 7.2 degrees, respectively, from the articular surface. Mean maximum, optimum, and minimum angles from drill point B were 109 +/- 7.2 degrees, 99 +/- 7.1 degrees, and 89.5 +/- 7.2 degrees, respectively. Point B increased the risk of ventral exit from the sacral body.

Conclusions-Point A and a drill angle of 90 +/- 4 degrees for drilling of the feline sacral body is recommended. This margin for error risks ventral exit from the body in 23/40 (58%) of the sacra in this study. Reduction of the margin for error to +/- 2 degrees would reduce the risk of ventral exit to 14/40 (35%) of the sacra in this study.

Clinical Relevance-Drilling at 90 degrees to the feline sacral articular surface is recommended. Findings from this study present a strong case for use of angled drill guides. (C) Copyright 2009 by The American College of Veterinary Surgeons