Step by step construction of a KAFO orthosis (Knee Ankle Foot Orthosis)
The modular Artikon system offers great simplification to the orthopaedic technician for construction of complex orthotic care. Find valuable tips and practicable know-how for optimal manufacturing and construction, by viewing a practical example in our online-tutorial.
Prepare material for the plaster cast impression.
Grease the silicone tube with Vaseline prior to cutting open.
Mark the ankle rotation point with the blue indelible pencil
Find the medial and lateral knee gap
Mark the lateral knee gap
Measure lateral height from ankle to knee gap.
Insulate the patient’s leg with wrapping foil (slightly tighten wrapping foil).
Fully insulated leg.
Fixate greased silicone tube ventrally at the leg by using masking tape.
Let the patient stand on the plaster heel plate and a height adjustment board (safe stand).
Prepare 6-ply plaster bandage according to foot length.
Prepare 6-ply plaster bandage reaching from knee to heel.
Position torsion wedge correctly at the plaster heel plate (approx. 1 – 1,5 cm in front of the anatomical roll over).
Soak the foot plaster bandage in water and place the patient’s foot on it.
During hardening of the plaster, shape the longitudinal arch by massaging it in.
Model the edge of the plaster bandage with your fingers in circular course.
Soak the dorsal calf plaster bandage and massage well into shape.
The heel must fully stand on the heel plate (plumb line falls through front edge of lateral ankle and front edge of heel).
After the plaster bandages have been hardened, carefully lift the patient’s leg and ask the patient to sit down.
Elevate the leg.
Wrap the leg in circular way with plaster cast bandages (beginning from the tip of the foot).
Let the leg lay down now.
For circular wrapping, the width of the plaster cast bandages must always be wrapped overlapping in triple-steps.
Then let the patient stand correctly on the plaster heel plate and make sure he / she is standing straight (correct standing position of the leg, if necessary) with the plaster cast still damp. Let the cast harden completely.
When the plaster cast has hardened, let the patient sit down and elevate the leg.
Remove the silicone tube.
Mark the cutting lines with the blue indelible pencil.
Carefully cut open the plaster cast in the channel.
Press the plaster cast channel to the leg in half height of the patella, in order to better position the 60:40 gauge later.
Remove plaster cast negative from leg.
Fixate the plaster cast negative circular with masking tape.
Place the plaster cast on the heel and level at the 90° mark.
Prepare the height gauge.
Align the height gauge to the height of the ankle rotation point and mark with blue indelible pencil.
Align the height gauge to knee gap height and mark with blue indelible pencil.
Mark the knee rotation point height, according to “NIETERT” 2 cm above the knee gap (good results were achieved by 1,6 cm for children and 1,8 cm for adults).
Place the 60:40 gauge at level of knee rotation point height, according to“NIETERT” and align to the reference lines in 90° angle.
Mark the knee rotating point using the 60:40 gauge (best if two people are working together).
If the knee joint is back shifted, place the knee rotation point to posterior according to the back shift (16 mm).
Drill a 5,5 mm hole at the mechanical knee rotation point, in order to subsequently position the adjustment axis.
Drill a 5,5 mm hole also at the ankle rotation point.
Align plaster cast negative and position adjustment axis.
Copy square axis with blue indelible pencil onto plaster cast and cut out with scalpel.
Push the adjustment axis through the model.
Fixate the adjustment axis with small plaster bandage at the model.
Watch out for the parallelism of the adjustment axes at both levels!
Prepare a matching bar and fill the model with plaster.
Use proper tools for modelling.
Insulate the plaster cast model with wrapping foil.
Put a nylon stockinette over the model and use PET 6 mm to deep-draw a trial shell.
The joint adapters are evened out in circular way with Pastosil.
A nylon stockinette is pulled over the model and knotted at the tube.
The model is insulated with PVA-foil and a vacuum is pulled.
Wrap the adjustment adapter in circular way with PVA-tape to ensure the vacuum when pricking in the screws.
A nylon stockinette is pulled over the model as first layer.
Basis for further lamination.
Prepared carbon fibre matting (cut at 45° angle to fibre direction), unidirectional carbon fibre webbing and aramide fibre fabric.
Cut the aramide fibre fabric with an electric cutter or special aramide scissors.
Attach one layer of carbon fibre matting at the foot part up to the roll over.
Attach another layer of carbon fibre matting at upper and lower thigh. The matting must reach exactly up to the adjustment anchors.
Between the joints, parallel to the bars, two layers each of unidirectional carbon fibre webbing are glued with spray-adhesive.
ixate unidirectional carbon fibre webbing at the foot sole from ankle joint to ankle joint as “stirrup”.
Now attach unidirectional carbon fibre webbing lengthwise from heel to roll over.
Then glue on another layer of unidirectional carbon fibre webbing as stirrup between the joints.
Control of the reinforcement layers.
For reinforcement, unidirectional carbon fibre webbing is positioned at the highest point of the calf – from medial to lateral.
4 layers of aramide fibre fabric are glued with spray-adhesive to the roll over with 7 mm distance to each other; the layers are in parallel fish scale mode.
To manufacture a soft edge, two layers of aramide fibre fabric are placed dorsally at the upper thigh edge between the medial and lateral reinforcements.
The carbon fibre matting underneath it must be cut out in the area of the aramide fibre fabric.
The aramide fibre fabric should be cut to fit in order to avoid unnecessary grinding later on.
Spray the nylon stockinette with spray adhesive in the area of the adjustment adapter.
Save the thread hole using the scissors.
Insulate the finished reinforced joints with Abdosil at their backside.
Fill the thread hole with Abdosil.
Fill the thread hole with Abdosil.
Immediately, screw the joint into the adapter with light pressure.
Then, seal the joints with Abdosil from the outside.
Now place the casting dummy onto the still liquid Abdosil (for all joints).
The PVC-reinforcement is placed dorsally at the upper thigh in the centre between medial and lateral reinforcement.
Repeat this step at the lower thigh – at the thickest point of the calf.
The reinforcement of the foot stirrups is glued with spray adhesive against each other as stirrup.
The glued foot stirrups.
Now attach another layer of unidirectional carbon fibre webbing from the center to the roll over.
Then reinforce the stirrup once again with unidirectional carbon fibre thread.
As last foot layer, add carbon fibre matting in 45° angle.
Secure the reinforcement of the calf with two layers unidirectional carbon fibre webbing…
…also the reinforcement of the upper thigh
…. and the medial and lateral bars.
The hollow spaces at the joints must be filled with Dacron felt.
To fixate the system anchors, the transverse unidirectional carbon fibre webbing underneath the system anchor cases are sprayed with spray adhesive and then are turned over (for all joints).
Finished reinforced knee joint.
Finally, carbon fibre matting is placed on the lower thigh area.
Also at the upper thigh part. Cut out also the area for the aramide fibre fabric.
The finished reinforced orthosis model.
Optionally, a decorating stockinette can be pulled over the model.
Pull soaked PA foil wrinkle-free over the model.
Fixate a suitable funnel.
Fill in the resin, which has been mixed in correct mixing ratio.
Spread the resin within the entire model and then massage it out in an even, thin layer.
Mark the point to cut free at the finished resin cast.
Carefully uncover the joints in the area of the silicone dummy by means of a scalpel.
Carefully remove the casting dummy.
Remove the joint screw.
Uncover the casting dummy also at the ankle joint.
Carefully remove the dummy.
Loosen the joint screw.
Uncover the model at the markings with an oscillation saw.
Place a circular cut at the centers of knee- and ankle joint.
Remove cut out material.
Carefully take the upper thigh shell from the model.
The shell should become loose easily. If this is not the case, the cutting must be re-checked.
The same is true for the lower thigh.
If the joints do not come off, they can be lifted off the model carefully with a slot screwdriver.
First, pull off the foot part to the rear.
Then take off the lower calf shell.
Finished, demoulded orthosis elements.
Now grind all elements with the socket router in order to deburr the edges.
Finally, uncover the joints with a Dremel grinder. Attach padding and belts to the orthosis and mount.
