Prosthetic Bird Feet – an Approach using Orthodontic Materials
Author contact: Ed (email@example.com)
Please email me if you want the photographs that go along with this article- they couldn't be included here. Cheers, Ed
The technique following has been carried out on a city pigeon whose both feet had fallen off leaving behind two short stumps of unequal shape and size which had become moderately flattened perhaps as a physiological adaptation.
The problem of pigeons losing feet is not uncommon in big cities. Their feet invariably become entangled in discarded pieces of thread, wool, nylon and similar thread-like, discarded man-made materials in city streets – the foraging territories for most city birds. When the birds attempt to pull these materials off, it can tighten around their limbs to the point that blood flow ceases to these areas resulting in eventual rot and its associated loss of limb.
Plate 1. Shortened limbs on pigeon. Image on left depicts left foot stub while image on right depicts right foot stub.
1.1 Practical considerations for the bird
Most city birds forage in the city streets. In addition to providing stability when they walk and perch, their feet provide an elevation that helps keep their tail feathers from dragging along the floor and caught up in their own excrement and city refuse. However fitting prosthetic feet such as that proposed in this article is not without its own problems. If the bird is unable to bend its prosthetic limbs, it will be unable to lower its body to conserve its body heat during the winter- this point cannot be overemphasised. Fitting such feet may necessitate that the bird be kept as a pet for its remaining lifetime.
The fitted feet should not be permanent just in case the bird takes a dislike to it – this may be the case if the bird has had sufficient time to adjust to having its shortened limbs. A trial period is recommended to observe how the animal responds to the feet and how it affects its flight.
The materials used to make and fit the prosthetic feet should be as lightweight as possible to not hamper the bird’s flight. Each foot made in this procedure weighed no more than 2g (prior to fitting materials), thereby adding no more than 4g to the bird’s body weight. Assuming an average pigeon body weight of 400g, this contributes around 1% additional weight. While I hasten to add that I have no specialised knowledge of maximum weights that can affect flight, I would speculate that a maximum addition of 3-4% or original body weight can be safely allowed for (but do check with an avian specialist if you seek clarification).
1. The orthodontic alginate is first used to make an impression (the negative) of the existing ends of the bird’s limbs to which the prosthetic feet will be fitted. See Section 2.1 below.
2. A stone mixture is then allowed to set in the negative so forming the positive mould which will form the working model for building the prosthetic feet. See Section 2.2 below.
3. The baseplate resin is then used to mould a slip-on “shoe” over the moulds from (2) above which is simultaneously attached to the prosthetic limbs and feet. See Section 2.3 below.
4. The prosthetic limbs are then fitted like a sandal over the feet stubs using elastic bands or other “soft” and light fittings. See Section 3 below.
The chemicals used here were obtained from a local dentist. For availability, try your local dentist and if that fails, check availability on the internet.
2.1 Negative Impressions
Plate 2. Negative impression of feet stubs setting in red rubber trays.
The brand of alginate used for this part was Alginkid.
2.1.1 Materials and Apparatus Used
Alginate powder, digital weighing scale, small water container (5ooml), spatula, mixing bowl (the blue rubber bowl depicted in Plate 3 was used), soft rubber setting tray (see the red tray in Plate 3), sharp knives, candle or clear nail polish, matches or cigarette lighter, two pairs of gloves and dust mask for each worker.
Plate 3: Materials & apparatus used to make negative impression and mould (Ruler depicted has full length of 30cm).
Follow the mixing instructions on the alginate packet (for this brand, 19g powder to 40ml water). Spatulate energetically in mixing bowl for approx. 30 seconds. Place mixture in red rubber tray and build to a height appropriate to the “shoe” height to be fitted. Hold the bird’s limbs firmly in the mixture until the mixture hardens sufficiently to form the negative impression. Both feet can be done at the same time. In this case, this took a little less than 2minutes at 15 degrees Celsius (the instructions recommend a working temperature of 23 degrees Celsius). Once the mixture sets, peel back the rubber tray away from the impressions. Pay attention to which impressions belonging to the left and right feet- this will be important for “distance” considerations when the feet are placed side by side (in my case the inner, prosthetic “toes” needed to be trimmed so that the feet would not tangle each other). It may seem obvious at this stage but I would encourage you to label each mould as left (L) and right (R) and on each, mark the inner side (I), outer side (O), front (F) and back (B) so that when you prepare the resin and build the shoe you know exactly how the prosthetic limb will need to be inserted.
2.2 Mould of existing feet stumps
Plate 4. Positive moulds obtained. Mould at left of image belongs to right foot.
2.2.1 Materials and Apparatus Used
Stone powder, small water container (5ooml), spatula, mixing bowl (the blue rubber bowl depicted in Plate 2 was used), soft rubber setting tray (see the red tray in Plate 2).
Mix the stone powder according to manufacturer’s instructions. The brand that I used is unknown but the mixing instructions were 200g of stone powder to 65ml water. Spatulate thoroughly to a consistent and even mixture without air bubbles and fill in the negative impressions from Section 2.1. Build up a handle on each limb with the remaining stone as this will facilitate an easier build of the prosthetic feet in the next section. Once the stone hardens a bit, remove the negative impression and allow the mould to dry according to manufacturer’s instructions. I left mine for 24 hours. Coat the surface of each mould with molten candle wax or clear nail polish to form a spacer which will facilitate easy removal of the mould from the shoe which will be built in the next section.
2.3 Building the Prosthetic Feet
There are probably many different items that can be used to form the new prosthetic feet. I used the little plastic protectors that come in some pizza boxes to prevent the boxes from being crushed while the pizza is being delivered (available at Pizza Hut here in New Zealand).
2.3.1 Materials and Apparatus Used
Two pizza box protectors, digital weighing scale, spatula, mixing bowl (the blue rubber bowl depicted in Plate 2 was used), two pairs of gloves and dust mask for each worker, Orthodontic baseplate resin powder and liquid.
Plate 5. Resin materials used. Image on left is of Ostron 100 resin liquid and image on right is of Ostron 100 resin powder.
Cut off two of the legs from each of the plastic pizza box pieces and shorten the other leg to an appropriate height – this is form the new prosthetic limb that will be attached to the slip-on shoe. Rather than trimming this limb with a knife, I burnt the open end until it reached the desired height. Before the plastic cooled, I pressed the limb on a flat surface to form a small disc at the end. I did this so that when I build the shoe and moulded it onto this limb, the disc prevented the prosthetic shoe (which will be built next) from rotating about the supporting prosthetic limb. The more irregular you can make the disc the sturdier the fit. However, burning off the extra height is quite tricky where two limbs are being fitted as they will have to be burnt down so that they provide the same height on each limb. You may need a few trials to get it right so do have extra pizza box protectors on hand. I then cut off a bit from the inner prosthetic toes so that the prosthetic toes would fit together for the given limb spacing on the bird. Try not to trim too much as these would provide stability to the bird.
Plate 6. The finished prosthetic limbs. Left image of frontal view. Right image of aerial view.
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Making Prosthetic Bird Feet
Here is the complete article with photos about making prosthetic bird feet. The photos ARE in the document, but you may have to move your mouse pointer over the space where they should appear in order to get them to display .. don't know why this is and will try to fix it, but you should be able to view the entire document and the photos with a little bit of effort ..
Thank you, Ed for providing this.
Hi All- thanks for the messages. Yes, I appreciate the humour in using something as insignificant as a pizza box throwaway but hey...if it works, why reinvent the wheel? She is doing well at my place. I built a shelf for her in front my window and she loves to sit there and look out at the other birds in the garden. She is free to fly around my home but she has adapted nicely to walking around on her stumps- but I don't think she stands much of a chance in the wild- I brought her home as she was struggling to find food out there. I put this ad up only in the hope that she may find some other pigeons to socialise with but I am quite happy to keep her as long as I need to. Thanks again for the messages- I don't get much time to check messages here so if you want to know anything else, please email me at firstname.lastname@example.org -I've been sorta busy organising protests and petitions to stop my local city council from culling by shooting the city's pigeons. It's going well so far and I think we have a good chance to stop them.
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