DRAFT Custom Design Process

 

Custom Design Processes

The posting techniques, cast modification and design principles we use, determine the shape of the finished orthotic shell. Different shell materials require different design principles to ensure a comfortable fit and ensure the device is as functional or accommodative as required. Our “Tissue Stress” Close Contact functional devices are PPL’s most popular devices, being suitable for most patients. Total Contact Accommodative offloading devices are chosen for patients with more complex foot shapes, and used extensively in the Woundcare area.

Tissue Stress Design - Close contact & functional orthoses

Tissue Stress devices are made using materials which have strength, yet some degree of flexibility. This allows us to design devices to fi t closely to the shape of the foot. More flexible materials facilitate normal dynamic movements of the foot, and provide high levels of comfort, control and shock attention. Tissue Stress orthotic shells are ¾ length, but can be extended to full length using cushioning materials.

When to Use

These types of devices should be selected when stability and correction in excess of 8° is required. Custom casted Tissue Stress orthoses are the optimal choice for conditions such as the supinated Pes Cavus foot, the mobile hyper-pronated flat foot with Tib Post Dysfunction and unusual foot shapes with orthopaedic presentations.

Posting Techniques

The design process we employ to adapt casts/scans for Tissue Stress devices is a variation of the Blake and Modified Root techniques. Intrinsic posting which is integral to the shape of the shell can be used at high levels (up to 15°), and is favoured over bulkier extrinsic posting (5-8°max). This along with a flat base ensures Tissue Stress devices are suited to patients requiring high levels of functional control and stability.

Cast/Shell Modifications

Modifications are added to allow normal 1st Ray plantarflexion, however minimal arch fill is added to ensure a close contact with the rearfoot and midfoot for maximum control and shock attenuation. As the materials have flexibility limited heel expansions are required producing a device which snuggly fits the heel, resulting in a highly stabilising device.

Root Functional Design - Rigid & semi-rigid orthoses

Root functional design devices are made using materials which have strength, but less flexibility and shock attenuation. Less flexible materials require more cast modifications to ensure comfort and device toleration. While these devices are harder and resist more force, they do not fit closely to the shape of the arch and midfoot. Root devices are slimmer in design and are accommodated more easily in dress footwear. Root orthotic shells are ¾ length but can be extended to full length using cushioning materials.

When to Use

These types of devices should be selected when stability and correction is required in slim fitting footwear. Root functional orthoses are the optimal choice when stiffness and durability are essential, however they provide less shock attenuation and cushioning than Tissue Stress devices.

Posting Techniques

We use Modified Root alongside Kirby techniques to adapt casts/scans for Root Functional devices. Intrinsic posting which is integral to the shape of the shell is limited to a maximum of 5°. Kirby skives are advised for high posting as it adds less bulk than extrinsic posting (max 5°).

Cast/Shell Modifications

More rigid materials require a larger amount of arch fill and heel expansions, as the hard shell edges can cause irritation. Whilst modifications are added to allow normal 1st Ray plantarflexion, however 1st Metatarsal & 1st Ray cut-outs can be used for enhanced mobilisation.

Total Contact Design - Accommodating & offloading orthoses

Total Contact devices are designed to accommodate deformity, limit motion and offload high pressure areas. Total Contact shells are all Full Length, made of flexible shock attenuation materials and manufactured using CAD CAM processes.

When to Use

Total Contact devices are used widely in the at risk and diabetic foot, and where there is gross orthopaedic deformity. They offload peak pressure areas by redistributing load over the full plantar surface of the foot. They immobilise the foot, rather than promoting function, and therefore minimal cast corrections and postings are used.

Posting Techniques

As accommodative full length devices, the bare minimum of cast/scan modifications are used, to ensure a close as possible fit to the foot shape. Intrinsic posting is not used, as the objective is to limit motion. However extrinsic posting can be applied to both the rearfoot and forefoot. Complex foot shapes, such as a rigid flat foot with large forefoot inversions, benefit from the devices having total forefoot posting/wedging built into the full length shells.

Cast/Shell Modifications

Whilst minimal cast modifications are uses, to offload specific high pressure areas, cut-outs can be applied to the shell and filled with softer materials. With softer shell materials offloading lifts such as metatarsal domes can also be directly milled into the shells. Please see device types section for further information.