Chris J Shales1, Lindsay White, Sorrel J Langley-Hobbs. 1. Department of Veterinary Medicine, The Queen's Veterinary School Hospital, Cambridge University, Madingley Road, Cambridge, UK. c.shales@bris.ac.uk
Abstract
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.
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.