Topcat’s range of pneumatic actuators for mechanical threshold limb testing are light, easy to put on and do not affect the animal’s behaviour. They have very low internal friction and are smooth and silent in operation. This is the small animal version with a force capacity of 30N and a single pin of either 1 or 2mm diameter at the tip. (Click here for our recent paper, presented in Capetown on the effect of tip size on mechanical threshold). Here’s the datasheet. Actuators are supplied as a kit including the following items:
- Active actuator
- Strap and buckle to react the force during the test
- Placement boot. for LA this is a modified brushing boot
- Dummy actuator and placement boot for the contra-lateral limb
This is the large animal version with a working stroke of the actuator is 20mm, making it suitable for most limb sites (the tendon sheath on the hind limb of a cow is the most taxing environment we’ve found so far).
Connection to the actuator is through our own ‘donut’ design. This push-on ring with the pneumatic line built-in is self sealing and releases automatically without damage if the subject becomes over-excited.
The smallest size was designed for use on the leg of a chicken and is also suitable for the tail of a rat. Seen here with three 1.5mm ball tips, this actuator is more commonly used with a single 1mm pin. Its force range is 10N and it weighs just 7 grams.
The cat here is wearing the limb actuator, but with the pressure line disconnected between tests. (She’s also wearing our remote controlled thermal threshold testing system, allowing the two modalities to be measured alternately). On the left is the small animal version, suitable for sheep and dogs. The curved lilac piece is removable and may be adjusted to suit the curvature of the limb under test. They are suitable for sterilisation by wiping with alcohol and contain limits stops to prevent accidental over-travel. All the actuators are suitable for use with our bench mounted and wireless mechanical threshold testing systems as well as with the Prodpro algometer.
The graph on the left, taken from our recent abstract presented at the AVA meeting in Davos, shows the difference in mechanical thresholds taken on the front canon bone of a group of horses, for a range of pin sizes ranging from 1mm diameter (sharp) to 3mm diameter (blunt). Also included is another configuration of three pins, each tipped with a ball bearing 2.5mm in diameter and arranged on a 10mm triangle, and a final sharp pin with an internal spring to bias it lightly against the tissue. This was included to test the hypothesis that, in some cases, animals respond to the first touch of the pin rather than at the pain threshold. As you can see, it did not make a significant difference in this case.