AFO in Joint Lamination Technique

AFO

in Joint Lamination Technique

This online tutorial describes the production of an AFO (ankle-foot orthosis) in Joint Lamination Technique. In the Joint Lamination Technique, as opposed to the Anchor Lamination Technique, the system anchors and system cases are embedded into the laminate. The following construction serves as an example:

  • unilateral
  • partially flexible foot piece
  • ventral shell
  • Joint Lamination Technique

The system ankle joint used here is a NEURO SWING. This production technique can also be applied to the production of an AFO with the system joints NEURO CLASSIC-SWING and NEURO SWING-CLASSIC, as it involves the same or similar system components. You can find the joint assembly NEURO SWING here.

 Mounting the Assembly/Lamination Dummies

Step 1/1

Mount the system joint by using the assembly/lamination dummy and in accordance to the exploded view drawing. When laminating, the assembly/lamination dummy serves as placeholder for the system joint's cover plate.
Note: You can find exploded view drawings in our product catalogue System Joints and Articulated System Side Bars.

 Bending the System Stirrups/Anchors

Step 1/11

First, mark the lower edge of the assembly/lamination dummy on the system stirrup. Everything above this line must not be bent, as this area (the joint area) is a part of the system joint later.
Note: When you have acquired a bent system stirrup, you can skip the steps
1 to 4.

Step 2/11

Clamp the system stirrup into a vice with plain jaws to bend it. Pay attention to the marking to avoid a subsequent deformation of the joint areas and to be able to bend very close to the joint.
Note: When you have acquired a bent system stirrup, you can skip the steps
1 to 4.

Step 3/11

Adapt the system stirrup to the shape of the model. Bend the system stirrup neck with a bending iron. Only bend in one direction.
Note: Do not use a hammer and do not heat the material.
When you have acquired a bent system stirrup, you can skip the steps 1 to 4.

Step 4/11

Remove the system stirrup from the vice and check the distance from the system stirrup to the model.
Note: When you have acquired a bent system stirrup, you can skip the steps
1 to 4.

Step 5/11

Adapt the system stirrup to the shape of the model. Bend the lower part of the system stirrup with a bending iron. Only bend in one direction.
Note: Do not use a hammer and do not heat the material.
Check the distance to the model.

Step 6/11

Adapt the system stirrup to the shape of the model. Bend the system stirrup foot with a bending iron. Only bend in one direction.
Note: Do not use a hammer and do not heat the material.
Check the distance to the model.

Step 7/11

Press the system anchor to the joint’s upper part by using a washer and a screw. To do so, use a torque screwdriver and a torque of 6 Nm. Then, remove washer and screw again. 

Step 8/11

Fix the system anchor with the screw (farther away from the joint) at the joint's upper part before you begin bending.

Step 9/11

While bending, please consider the applicable bending radii and use proper tools (bending iron with round edges).
Note: You will find information on bending radii in the manual for System Side Bars and System Anchors.

Step 10/11

Check the distance from system anchor and stirrup to the positive cast. Please make sure to have enough space left for the reinforcing profile and the reinforcement layers in order to avoid later strains to the laminate. Thus, the joint areas stay parallel.

Step 11/11

Grind the system stirrup and the system anchor. Always grind in direction of rolling. Remove all notches from bending and avoid sharp edges.
Note: System ankle joints with dorsiflexion stop, which can be adjusted by filing, should always be mounted in their pre-assembled neutral position without changing the dorsiflexion stop.

 Preparing the System String

Step 1/12

Use the activator spray as basis by spraying it thoroughly on both sides of the system anchor. Begin above the assembly/lamination dummy.

Step 2/12

Use some stockinette as underlay when attaching the profile core. Heat the profile core and adhere it from below to the system anchor with medium viscous fast-acting adhesive.
Note: Mind the safety data sheet when using fast-acting adhesive.

Step 3/12

Pull at the stockinette from both sides and press the profile core from below to the system anchor in order to fix it there.

Step 4/12

Reinforce the profile core of the tibial shell. Add some medium viscous fast-acting adhesive to the system anchor and profile core. Heat a second profile core and adhere it to the first.
Note: Mind the safety data sheet when using fast-acting adhesive.

Step 5/12

Example for the course of the reinforced profile core on a unilateral AFO.
Note: Have the profile core cool down to room temperature before removing it from the model.

Step 6/12

Please make sure to have enough space left for the reinforcement layers in order to avoid later strains to the laminate. Thus, for example, the joint areas stay parallel.

Step 7/12

Example for the course of a profile core on a unilateral AFO. The double profile core increases the torsion resistance of the final orthosis.
Note: With this course, you set the stiffness of an orthosis in the particular areas. You can also use reinforcing carbon fibre braids for the transverse areas.

Step 8/12

Insulate the joint areas of the system stirrup and the joint's upper part with a thin layer of insulating wax. Fill all hollows and grooves which shall remain resin-free as well. Insulate the sliding washer, too.
Note: Use a small syringe in order to apply the insulating wax in a simple and accurate way.

Step 9/12

Insulate all screw threads as well as all hollows and grooves of the assembly/lamination dummy with insulating wax. 

Step 10/12

Mount the assembly/lamination dummy according to the exploded view drawing. Fill all hollows, grooves and screw threads with insulating wax.
Note: You can find exploded view drawings in our product catalogue System Joints and Articulated System Side Bars.

Step 11/12

Clean all areas (from all sides) which shall be embedded into the laminate later. Remove insulating wax and grease residues.

Step 12/12

Pull carbon fibre braided tube over the system stirrup as well as the profile core (incl. system anchor). Fix it as close to the joint as possible by sewing and/or tying it with aramid fibre roving. Then, stretch the fibres and fix the other end too, if applicable.
Important! Only the stretched fibre can take on load and release it again!

 Reinforcing the AFO

Step 1/27

If the positive cast is still wet, insulate it with compression film first. Then, pull a PA reinforcement stocking over the positive cast. Now, the PVA film tube can easily be pulled over as base film layer.
Note: We recommend to use a 0.10mm thick film layer.

Step 2/27

In order to increase the load capacity and useful life of the material of a partially flexible foot piece, reinforce the forefoot and rolling-off area (arrows) flexible and without a brim.
Note: A toes bank, or similar, can be attached subsequently if required.

Step 3/27

We recommend to use electrical scissors (e.g. Easy Cutter) to cut the separate fabric layers (carbon as well as aramid).
Note: Use adhesive transfer tape without backing material to fix the cutting edges, so that the edges cannot fray.

Step 4/27

Dry the aramid fibre fabric at 120°C in an oven for at least one hour.
Thus, you remove any moisture that has been absorbed during storage and improve the fabric’s properties for further processing.

Step 5/27

Consider the foot’s rolling-off area when laminating a partially flexible foot piece. It encompasses the area from anterior of the metatarsophalangeal joint (d1) of the big toe to posterior of the metatarsophalangeal joint (d2) of the little toe.

Step 6/27

Consider the order of the different reinforcing layers when laminating a partially flexible foot piece. The quantity of the reinforcing layers should match the individual needs of your patient. The following reinforcing steps indicate where you can adhere more reinforcing layers, if necessary.
Note: Aramide is a flexible material that is particularly well suited for areas bearing dynamic loads.

Step 7/27

Scarcely cover an aramid fibre fabric pre-cut with adhesive spray and adhere it to the entire sole. Mind the 45° direction of the fibres. Apply the next layer of aramid fibre fabric with a 90° direction of the fibres. Use as many layers of aramid fibre fabric as you need (this is an exemplary picture).
Important! Take care to use the fibres stretched!

Step 8/27

Scarcely cover a carbon fibre fabric pre-cut with adhesive spray and adhere it up to the rolling-off area. Then, cover the foot piece’s sole and sides with a carbon fibre fabric pre-cut.
Important! Take care to use the fibres stretched!

Step 9/27

Keep on reinforcing with carbon fibre fabric. Each layer of the pre-cuts should end further ahead (distally) in the rolling-off area. Use as many layers of carbon fibre fabric as you need (this is an exemplary picture).
Note: Always only spray the pre-cut which still needs to be adhered and not the already adhered reinforcement.

Step 10/27

Attach unidirectional carbon fibre band below the joint retainer at the foot piece. Mind the direction of the fibres (arrows).

Step 11/27

Keep on reinforcing in a v-shape way. Mind the direction of the fibres (arrows).

Step 12/27

Take care not to cover the edges of the rolling-off area with carbon fibre band when adhering the unidirectional carbon fibre band in a v-shape way.

Step 13/27

Reinforce the midfoot and forefoot area with unidirectional carbon fibre band. Spare the edges.

Step 14/27

Reinforce the area of the lower leg with carbon fibre fabric. Spare the joint retainer. Use as many layers of carbon fibre fabric as you need (this is an exemplary picture).
Important! Take care to use the fibres stretched!

Step 15/27

Attach unidirectional carbon fibre band above the joint retainer. First, adhere a strap transversely around the lower leg. Then, reinforce along the profile core. Mind the direction of the fibres (arrows). Use as many layers of carbon fibre band as you need (this is an exemplary picture).
Note: Always only spray the pre-cut which still needs to be adhered and not the already adhered reinforcement.

Step 16/27

Attach unidirectional carbon fibre band along the profile core. Mind the direction of the fibres (arrows). Use as many layers of carbon fibre band as you need (this is an exemplary picture).

Step 17/27

Apply some insulating wax to the thread of the joint retainer in order to seal it airtight.

Step 18/27

Mount the assembly/lamination dummy with system string to the joint retainer. Find the correct position (the shape of the joint retainer matches the hollow for the bearing nut of the joint's upper part). Screw the retaining screw through the base film into the joint retainer and screw it tight.

Step 19/27

Attach unidirectional carbon fibre band in a v-shape below the joint retainer at the foot piece again. Mind the direction of the fibres (arrows).

Step 20/27

Take care not to cover the edges of the rolling-off area with carbon fibre band when adhering the unidirectional carbon fibre band in a v-shape way.

Step 21/27

Attach carbon fibre fabric below the joint retainer. Mind the direction of the fibres (arrows).

Step 22/27

Keep on reinforcing. Each layer of the pre-cuts should end further ahead (distally) in the rolling-off area. Use as many layers of carbon fibre band as you need (this is an exemplary picture). Attach a final layer of carbon fibre fabric to the foot piece. Cover the entire rolling-off area without exceeding it with the reinforcement. Also, cover the assembly/lamination dummy up to one half.

Step 23/27

Finish reinforcing the partially flexible foot piece with aramid fibre fabric. While doing so, cover the entire sole. Mind the 90° direction of the fibres. Apply the final layer with a 45° direction of the fibres. Use as many layers of aramid fibre fabric as you need (this is an exemplary picture).

Step 24/27

Reinforce the lower leg area with unidirectional carbon fibre band along the system string. Mind the direction of the fibres (arrows).
Important! Take care to use the fibres stretched!

Step 25/27

Attach a final layer of unidirectional carbon fibre band above the assembly/lamination dummy. Mind the direction of the fibres (arrows).
Note: Always only spray the pre-cut which still needs to be adhered and not the already adhered reinforcement.

Step 26/27

Attach a final layer of carbon fibre fabric to the lower leg area. Cover the assembly/lamination dummy up to one half.
Note: Always only spray the pre-cut which still needs to be adhered and not the already adhered reinforcement.
Important! Take care to use the fibres stretched!

Step 27/27

Finally, in order to fix the reinforcement layers, pull a decorative fabric or a PA reinforcement stocking (for a carbon look) over the model. Thus, the PVA film tube can easily be pulled over as top film layer.
Note: We recommend to use a 0.10mm thick film layer.

 Laminating the AFO

Step 1/5

This production technique is especially adapted to our epoxy resin and hardener.
Important! Please consider the processing instructions and the safety data sheets for our epoxy resin and hardener. Precisely stick to the mixture ratio and thoroughly mix resin and hardener.

Step 2/5

Mix a sufficient amount of resin and hardener. Let the fabrics soak completely and rub surplus resin out.

Step 3/5

Press out the foot piece in order to receive the highest possible fibre volume ratio. While doing so, protect the film with some padding material and make sure to maintain the form of the modified pitch.

Step 4/5

The shaping dummy increases the fibre volume ratio at the system joint area and facilitates mounting the NEURO SWING cover plate later. Align the shaping dummy, fitting the joint's upper part, and fix it with adhesive tape.

Step 5/5

Have the model harden over night (at least 10 hours), under vacuum and at room temperature.
Important! Here, again, please consider the processing instructions for epoxy resin.

 Cutting the AFO

Step 1/6

Use a sharp knife to remove the thin laminate layer over the assembly/lamination dummy.

Step 2/6

Mark the cutting lines on the laminate. To do so, prolong the cutting lines of the assembly/lamination dummy, which enable you to cut out the orthosis as close to the joint as possible.

Step 3/6

Carefully lever the assembly/lamination dummy out of the laminate. Make sure not to damage the joint areas of the system stirrup in the process.

Step 4/6

Use an oscillating saw to saw along the edges in order to remove the orthosis parts from the model. You can see the recommended saw blade in the picture. Thus, you can saw very close to the system joint without damaging it.

Step 5/6

Remove all laminate parts which are no longer necessary.

Step 6/6

Carefully remove the orthosis parts from the model. Those are not yet completely hardened. Consider this while removing the orthosis parts, in order to avoid deformations.

 Tempering and Grinding the AFO

Step 1/4

Clean all the joint areas as well as the system stirrup before you temper the parts of the orthosis. Heat all wax residues with a hot air blower (1) and blow the liquefied insulating wax out of the hollows (2). Remove all residues with a cloth (3). Remove the PVA film tube as well.

Step 2/4

Temper all parts of the orthosis before you grind them. Place the orthosis parts into a cold oven and heat it up slowly. When tempered, the parts of the orthosis are stable and can be worked in the best possible way.
Important! Here, again, please consider the processing instructions for epoxy resin.

Step 3/4

Grind the edges of the orthosis parts (e.g. with an angle grinder). But absolutely avoid producing predetermined breaking points! Also make sure that the flexible area of the foot piece is even (without brinks).
Note: Even after tempering, you can still work aramid fibres with sharp scissors.

Step 4/4

In order to remove all possibly caused notches, remove resin residues from the joints' surfaces with a sharp knife and polish them subsequently (e.g. with a marbling tool).

 Mounting the System Joint

Step 1/1

Mount the system joint according to the assembly instruction in the manual of each respective system joint.
Note: You can also find manuals in the download area.

 Applying the Padding Material

Step 1/3

Cut some attachable padding material into shape for the orthosis (e.g. the xDry towelling padding material).
Note: You can use the dummy for the padding material as a template.

Step 2/3

Adhere hook dots to appropriate areas of the orthosis shells. Attach the padding material.

Step 3/3

Now, the orthosis can be tried on.

 Alignment of the Orthosis

Step 1/1

The alignment of the orthosis is based on the individual, gait-related normal posture of the patient. In mid stance, this results in a gait pattern that is as physiological as possible.