Lag screw fixation
1. General considerations
Although the technique and indications for lag screw fixation are the same as in dogs, the size of the bone and the thinness of the cortices makes lag screw fixation more difficult in cats.
2. Screw direction
The screws are inserted in lag fashion. To achieve maximal interfragmentary compression, the screws must be directed perpendicular to the fracture plane.
3. Screw insertion
A glide hole (outer diameter of the screw) is first drilled into the cis (near) cortex followed by the thread hole (core diameter of the screw) in the trans (far) cortex using the appropriate drill bits and drill sleeves. The drill sleeve for the thread hole must be inserted to the trans cortex to ensure proper placement and compression.
The hole is slightly countersunk to enlarge the contact area of the screw head to the bone.
The screw length is measured with a depth gauge. Use the longer measurement.
The thread hole is tapped and a screw of appropriate length is inserted. The screw should exit the trans cortex by 2mm.
Depending on fracture configuration, 1-2 additional screws are inserted in the same fashion.
Note: take care not to place them too close to each other. Safe distance is at least 1 screw diameter away from any fracture line and 2 screws should be separated by 2 x their diameter.
