• Orthosis is a biomechanical device which can be modified to achieve or improved body portion and functions.
• Orthosis is a combination of two words “ortho” meaning to straighten it out or correct it and “tic” meaning “systematic pursuit of”. Hence it refers to an external skeleton appliance applied to a part of body part and is a modern version of “brace.” However, it must be remembered that brace in its true sense means that when it is applied it would allow movement at a joint while a splint does not allow any movement.
• ISO (854901 1989) defines an orthosis as an externally applied device used to modify the structure and function characteristics of the neuromuscular and skeletal system.
• In simplistic terms one can say that it is an orthopaedic appliance which is used to support, align, prevent, and/or correct deformities of a body part or segment and improve function of moveable parts of the body.
• Although the terms brace, splint and orthosis have been and are used interchangeably, in their true sense they are different appliances and should only be used as meant to be.
• The American Academy of Orthopedic Surgeons (AAOS) and American Orthotic and Prosthetic Association developed a standard nomenclature for devices. Various generic acronyms have been used and a table is provided below. Orthosis are described by the joint they encompass, e.g. ankle foot orthosis (AFO) covers foot and ankle joints while FO is a foot orthosis, which is applied to a foot by either being placed inside or outside of foot wear.

 Figure 1. Example of a foot orthothic with posts along the medial side and posterolateral heel showing plantar, lateral and top views.

• An orthosis is an externally applied device that is designed and fitted to a segment/part of body to achieve one, more or all of the following goals:

• Control biomechanical alignment.
• Correct or accommodate deformity.
• Protect and support an injury or a painful conditions like in feet – metatarsalgia, Morton neuroma. In-knee varus brace to offload an arthritic compartment of knee. Assist rehabilitation or activities of daily living (ADL).
• Increase mobility.
• Increase independence.

To understand and prescribe orthosis one first needs to understand the terminology. Most orthoses are prescribed as CAPITAL ALPHABETS like AFO (ankle foot orthosis) and named according to body region:

S = Shoulder

E = Elbow

W = Wrist

H = Hand

H = Hip

K = Knee

A = Ankle

F = Foot

C = Cervical

T = Thoracic

L = Lumbar

S = Sacroiliac

• Some functional characteristics of orthosis are:

• Providing support during healing – TLO (thoraco-lumbar orthosis) for osteoporotic lumbar fractures.
• Limit movements like resting hand splints.
• Correct deformity or prevent further progression of deformity, e.g. AFO in foot drop to correct or prevent deformity in cerebral palsy (CP).
• Assist in movements like hip–knee–foot–ankle (HKFA orthosis which help those suffering from myelomeningocoele.

• Commonly prescribed orthoses include:

• Foot orthoses (FOs) – like metatarsal dome for morton neuroma, metatarsal bar for metatarsalgia, etc.
• Ankle orthoses (AOs).
• Knee orthoses (KOs) – for joint protection, pain reduction or support after surgery.
• Ankle-foot orthoses (AFOs) and knee-ankle-foot orthoses (KAFOs) – to improve mobility, support rehabilitation and biomechanical stability.
• Various upper-limb orthoses, although less commonly used, are to provide positional and functional support to the upper limb.
• Spinal orthoses – to correct or control spinal deformities especially in setting of spinal curvatures like scoliosis and injuries and to provide immobilisation or support to spinal injuries like cervico-thoraco-lumbar orthosis (CTLO), TLO.

• To understand the function of orthosis one needs to have understanding of basic biomechanical principles. In normal gait cycle ground reaction forces oases anterior to the ankle at heel strike. For example in a spastic diplegic the ground reaction force passes behind the ankle and results in increased knee flexion ipsilaterally. With the use of an AFO which prevents dorsiflexion of ankle the ground reaction force (GRF) passes in front of ankle and thus results in reduced knee flexion and results in better gait.
• Basic types of orthosis are:

• Static
• Dynamic

• Static orthoses are rigid devices which support either weakened or paralysed segments of the body in a particular position.
• Dynamic splints facilitate motion of a normal part to allow better function.
• When prescribing an orthosis one need to take into consideration:

• Three point pressure control system.
• Static or dynamic splint.
• Tissue tolerance to compression and shear force.

Foot orthosis (FO)

• Indications: flat feet, plantar fascitis, correction of resting heel.
• Heel cup – a rigid plastic insert which prevents lateral calcaneal shift in flexible flatfoot.
• UCBL (University of California Biomechanical Lab) or as some people suggest University of California Berkeley Campus) which provides maximal manual correction and is prescribed in conditions like plantar fasciitis.
• Arizona brace – a laced brace made either of leather or synthetic material to make it breathable. Please see Figure 1.

Ankle foot orthosis (AFO)

• Indications: maintaining ankle positions in conditions like foot drop, ankle instability, weakness of dorsiflexion in swing phase to avoid tripping over, etc.

• Posterior leaf spring (PLS) allows slight plantar flexion as well as dorsiflexion because of its trim line behind malleolis giving it a thin posterior heel support that widens as it moves into the calf. This results in a normal ankle rocker and improved gait with orthosis.
• Hinged AFO (HAFO), allows free dorsiflexion in stance phase and limits plantar flexion to preset level like 90 degrees. This results in normal ankle motion during stance and swing phases of gait. This helps clearance of toes during swing phase.
• Solid AFO (SAFO) does not allow any motion at ankle. 
• Ground (floor) reaction AFO which is a rear entry device with anterior shin and foot sections.

• When prescribing a AFO one needs also to consider the rigidity of AFO. Posterior leaf spring is the least rigid, while maximal resistance AFO provides maximum resistance for dorsiflexion and hence resists plantar flexion.

Knee ankle foot orthosis (KAFO)

• Indications: quadriceps paralysis or quads weakness, provides stability in genu valgum or varum or patients with paraplegia as a result spinal cord injury.
• KAFO is difficult to wear and take off and requires patient to have enough cognitive skills to be able to do that.

• Double upright metal KAFO (most commonly used).
• Scott Craig orthosis (spinal patients).
• Supra-condylar plastic orthosis.

• Other orthosis are knee orthosis, like cricket pad splints, knee extension braces, HKAFOs which extend up to the knees and THKAFO (trunk hip knee ankle foot orthoses).

• A prefabricated orthosis is a device which is pre-made and is subsequently customised to meet the specific needs of the patient.
• These orthoses are often prescribed for short-term use or in the case of non-complex clinical presentations.
• A custom-made orthosis is a highly specialised device that is manufactured from a cast or mould of the individual client. It is not able to be fitted to another person, as it has been designed and manufactured to meet the specific needs of the individual. 
• These are normally made using different casting techniques such as:

• Full weight-bearing polstyrene foam step-in boxes.
• Neutral position semi-weight-bearing polystyrene foam step-ins.
• Neutral position OFF weight-bearing plaster casts.
• Hand technique plaster casts.
• In-shoe vacuum techniques.
• CAD-CAM (21st century computer designed) techniques.

Laboratory preparation and orthotics fabrication

• Modification of positive model.
• Intrinsic forefoot posting.
• Shell selection.
• Extrinsic forefoot and tip posting techniques.
• Intrinsic rear foot position.
• Extrinsic rear foot posting.
• Orthotic additions.
• Sports-specific alterations.
• In-office fabrication techniques.

• A prosthesis is an artificial device attached or applied to the body to replace a missing limb, part or an appendage.
• Prostheses have moved on immensely from the days of Captain Cook from wooden pegs for legs and hooks for hands to lighter, stronger and more naturally functioning prostheses.
• Technological advances include the “energy storing foot,” the “microprocessor controlled knee” and the “myoelectric” (bionic) hand.

1. Socket
2. Suspension
3. Articulation
4. Shank/pylon
5. Terminal device

1.Socket is the element which connects the residual limb with the prosthesis. Socket not only protects the appendage but also transmits the forces while standing and ambulating.
Most prostheses initially have a temporary or preparatory socket to allow the oedema of the appendage to settle and allow the limb to embed into the prosthesis.

2 Suspension mechanism consists of belts, wedges, straps, suction or a combination of all of the above.
Suction mechanisms are either standard suction, which is contoured to the shape of the limb or silicon suction-based system. In silicone systems a socks slips onto the affected limb which then inserts into the prosthesis. This allows to form an airtight seal that stabilises the prosthesis.

3 Articulation allows support during stance phase, smooth control during swing phase and allows motion for sitting and kneeling. Such an articulation can be either single axis or polycentric axis.

4 Shank/pylon is a simple tubular structure that attaches a socket to the terminal devices. These vary from simple tubular shells to dynamic devices that not only allow axial control by controlling rotation but may also absorb, store and release energy

5 Terminal device – in lower limb prosthesis is mainly a foot but could be a running blade as used by runners in the London Olympics.
Although ankle function is built in into the terminal device like foot but on occasions may be separate as those involved in manual labour, etc.
The terminal device has a basic function to provide a stable weight-bearing surface, a shock absorbing surface, replace lost muscle function, replicate the anatomical joint, and last but not the least provide cosmetic appearance.

Commonly two types of terminal device are available, namely energy storing feet and non-energy storing feet.
Also terminal devices can be non-articulated or articulated (which again can be uni or multiaxial).

SACH (solid ankle cushioned heel) foot is a non-energy storing terminal device. It replicates plantar flexion in a similar fashion to normal ankle and hence allows a smooth gait pattern. It is ideal for those patients who have a sedentary lifestyle and with a prosthesis for a transfemotal or transtibial amputation. It is a low maintenance device which is cheap in economic terms.

Uni-axial foot provides greater stability in the stance phase as it has passive plantar flexion and dorsiflexion built into it.

Energy storing feet are multiaxial feet giving them near normal functional potential. They can perform inversion, eversion, plantar flexion and dorsiflexion and to an extent rotation. Because of these abilities they can be utilised walking on uneven or rough surfaces like cobbled or pebbled surfaces.
Another energy storing terminal device is a DRF (dynamic response foot) which is favoured by young and athletic individuals due to its performance.

1. Choking syndrome
2. Skin problems
3. Limb pain
4. Prosthethic gait
5. Increased energy requirement for ambulation

• Acute choking syndrome results from venous obstruction at the proximal segment of the residual limb where the socket is too tightly fitted and has space in prosthesis distal to it. This snug fit acts like a venous tourniquet and causes swelling distally which engorges the remaining residual limb. As the limb is more swollen than when it went inside it causes further tissue ischaemia resulting in pain and redness and a peau d'orange appearance similar to skin peel of an orange.

• Continued existence of this situation leads to chronic skin changes and haemosiderin deposition similar to venous ulcerations.

• Skin sequale are varied ranging from contact dermatitis which may settle down with topical steroids to excessive sweating and cyst formation.

• Continued limb pain may be an issue which may either be a continuation of phantom limb pain to poor surgical technique. Improper division of nerves can lead to neuroma formation in which an unstable residual stump/limb may result from lack of balanced myodesis (suturing of muscle to tendon or bone), e.g. failure to perform adductor myodesis in a transfermoal amputation may result in unopposed hip abductor action. Myodesis should not be confused with “myoplasty” which is suturing of muscles to periosteum.

• Other causes of continued limb pain could be because of poor fitting of prosthesis from the beginning to those leading to poor fitting later on. As the oedema resolves in the limb, it necessitates readjustment. The very reason that temporary sockets are used initially. However, it is possible that either due to heterotrophic ossification or unsuitable soft tissue pad on the residual limb can result in poor fit and a source of pain.

• Although the energy consumption is less with transtibial prosthesis than mobilising with crutches, energy expenditure is increased with ambulation. For a Syme amputation the energy requirement is increased only 15% while with vascular transfemoral it is increased by 100%, which puts increased demands on one’s cardiovascular and respiratory systems. Traumatic transfemoral amputation increases energy demands by 68%.

• Upper limb prostheses are different to lower limb prostheses as functionally these are more prehensile (designed around grasping and gripping objects).
• In general, upper limb prostheses are either body powered ones or myoelectric devices, which function by transmitting electrical activity from a residual limb to electric motor of a prosthesis via surface electrodes.
• Myoelectrical prostheses not only provide better cosmesis but higher functional caliber through a more proximal function. Their downside is that they are not only bulky, expensive and require regular maintenance but also lack sensory feedback.
• Two common myoelectrical units in use are two site/two function devices and one site/two function devices. Their main difference is that the first one uses separate electrodes to account for potential flexion and extension of prosthesis. The latter device senses and uses muscle contractions of different strengths to perform the extension flexion function, e.g. strong contractions open terminal device while weak contraction picked up by the same electrode results in closure of terminal device. Although one can learn to adapt, initially these devices can be cumbersome to use.
• Body-powered devices are durable and have reasonable costs and weight. Although they provide a sensory feedback which lacks in myoelectric prosthesis they are less cosmetically pleasing and require gross limb motion to be used properly.
• Wrist, shoulder and elbow prosthetics are outside the scope of FRCS Orth and hence have not been discussed further. However, in recent years some candidates have asked questions on types of hand prosthesis and their advantages and disadvantages.
• Cosmetic hand is a passive terminal device which is less functional but more cosmetic to such an extent that it can look like the other native hand and is difficult to be differentiated physically. Hence they also tend to be generally expensive.
• Mechanical hands are “active terminal devices” and functionally more robust. These can be broadly categorised into three categories:

1. Hand-like devices
2. Hooks and hands with cables
3. Myoelectric devices

• Hand-like devices consist of thumb, index and middle finger, where thumb is placed at 90 degrees to two fingers and hence allow palmar prehension. This can be covered with a silicone hand to make it look like a hand. It is an ideal choice for those working in offices.
• Non-hand prehension devices or hooks similar to the one of Captain Cook are favoured by those involved in physical labour. They have quick couplings to allow transfer between different types of hooks to provide a robust functional mechanical hand.
• Finally, bionic devices are externally powered myoelectric devices which use special force-sensing chips and can provide a stronger grip. However, these cannot be used those by involved in physical jobs as they need to kept away from hostile environments like water, dirt, and oils. 
• Mechanisms of operating terminal devices could either be a voluntary opening mechanism or a voluntary closing mechanism which usually tends to be heavier and less durable

• Biomechanical principles central to how orthoses work and hence their understanding is essential, e.g. FRAFO in a patient with CP improves knee extension and ankle plantar flexion and allows movement/function. In CP foot in relative plantar flexion, GRF is moved anteriorly which results in knee extension moment.
• These are three relatively simple principles:

1. Pressure or total contact area.
2. Equilibrium or three point pressure system.
3. The lever arm principle or sometimes also referred to as kinesiomatic reminder.

• We need to understand these basic concepts. We are going to explore these three one by one. Firstly:
• Pressure is the force per unit area. This is important as the area of the orthosis would be greater there would be less pressure on the skin and hence less pressure effects on skin itself. An easier analogy is that one feels more pain if one’s foot is trodden on by a pointy heel rather than a broader heel. The reason is that there is more area in a broader heel for the same hypothetical 70 kg typical medical person. Please browse the pictures below for explanation.
• Now moving onto equilibrium (definition of which we all know is sum of the forces and the bending moments created must be equal to zero) is essentially the three point force/pressure application system where all the three forces are applied so that the primary one force is against in direction and magnitude to the other two forces bringing the sum of all three to zero like when doing an MUA of a forearm fracture and applying the three point pressure while moulding the plaster cast. The primary force will be at the level or point where the movement is inhibited in the form of an orthothics or movement is facilitated in case of functional orthotics or a brace like a three point extension brace used for lumbar fractures.
• And finally the lever arm principle, which in simplest sense means that the longer the moment arm the smaller the amount of force required to produce a movement in a joint. This principle allows us to help decide the length of the orthosis to allow or prevent movement accordingly.
• The above three principles are used in design by ensuring that there is enough padding covering the area for comfort (first principle – pressure), all forces acting on orthotics are balanced to zero and hence skin is not irritated (second principle – three point pressure system/equilibrium) and the third principle by ensuring that orthotic is of adequate length to ensure that adequate force to create the effect required by orthosis and prevent excessive forces onto tissues or skeleton.
• Understanding control options of joint mobility on orthosis is important. These are free, stop, hold, hold variable, and assist. That is exactly what they do as free one means it exerts no control over the joint, and assist one assists the function of the joint.

Figure 2. Surface 100mm² as each side of heel is 10 mm x 10mm. P=F/A 75,000/100 =750g/mm²

 

• Assess patient needs:

• Assess comorbidities that affect outcome.
• Assess and categorise functional level of patient.
• Determine appropriate types of a specialised prostheses (running leg, swim leg, blade prosthesis, etc.).
• Determine appropriate design type based on patient acceptance and outcomes:

1. Body-powered versus cosmetic interface.
2. Design and suspension. 
3. Vertical shock and torsional force absorption.

• Prefabricated or custom made.
• Functional levels for prosthetic prescription range from FL1 to FL4. FL1 (functional level 1 which refers to a sedentary life style) is the ability to use the prosthesis for transfer or walking on a level surface.
• While FL4 (functional level 4, a highly active lifestyle) shows ambulation with high impact, stress or energy levels.

Orthotic Rx:

• Essential patient info/demographics
• Details of referrer
• All diagnoses
• Orthosis or shoe 

Modifications:

• Side
• Type
• Component
• Suggestion
• Requirement

e.g. Metatarsal dome if Morton’s neuroma or if two adjacent Morton neuromas a metatarsal bar which can be applied to the shoes/foot wear.

1.Prevent deformity – resultant skeletal alignment. Clinical examples include:

• MSK indications – Milwaukee brace for scoliosis, dynamic splinting to prevent scar shortening in burns.
• Neurological indications – AFOS in patients with cerebral palsy, CTLSO to prevent motion at cervical region.

2.Provide stability by either assistance with motion or reducing excessive motion. Clinical examples of:

• Assistance with joint motion.
•     MSK – AFO with dorsiflexion assist for dorsiflexion weakness.
•     Neurological – reciprocating gait orthosis (RGO) assist patients with spinal cord injury to ambulate.
• Reduced joint motion.
•      MSK – shoe inserts for foot deformity, Futuro splint with thumb extension for osteoarthritis (OA) of thumb

3.Functional action – GRF (ground reaction force).

• Reduce axial loading and reduce forces placed on a joint, e.g.:
•    MSK – shoe inserts for metatarsal pad for diabetic foot deformity.
•    Neurological – heel wedge for a pronated foot of a child with cerebral palsy.

• Indications: allows correction of heel alignment like pushing a varus heel to physiological valgus or corrects an overexcessive valgus into less valgus, e.g. adult acquired flat foot conditions like:
• Tibialis posterior tendon dysfunction this can be used to correct heel alignment and also providing medial longitudinal arch support.
• Sprain of spring ligament.

Design principles

• Accurate impression.
• Application of appropriate three point force.
• Application of appropriate materials and components.
• Ability to control joints as it loads.
• Total contact fit.

• Full weight-bearing polstyrene foam step-in boxes are used.
• Heel cup counters orthothics:

• Rigid or soft.

 

Functions of orthosis

• Orthosis can be either a:

• Reinforcement (heel counter/shank/toe box).
• Insoles/internal modifications (heel pads/metatarsal pads/insoles).
• External modifications (heel wedge/medial heel wedge/metatarsal bar/rocker pad/bar).

• Let’s have a look at an AFO. It has several parts like:

• Foot plate.
• Uprights/shell.
• Posterior calf band.
• Brim.

• AFOs can also be designed either:

• Solid AFO – which limits all foot and ankle motion.
• Hinged AFO – which allows some motion in sagittal plane.
• Assist – posterior leaf spring – (DF assist)/steel DF spring.
• Stop: 

Posterior stop - limits PF

Anterior stop – limits DF.

• Indications: foot drop temporary or permanent like common peronal nerve palsy.

Ankle OA/degeneration

• Indications: mild degenerative ankle/OA ankle.

• Achilles tendinopathy as night time splint to allow for stretching of gastrocnemius.
• Plantar fasciitis – as night time splint to stop plantar flexion and to keep plantar fascia stretched during night.

• Indications: similar to AFOs for foot drop, tendon reconstruction/repair but allows eel to be cleared to avoid get pressure sores at heel.

• Not rigid enough so not suitable for deformity correction and severe OA/degeneration of ankle.

• Benefits: balance enhancement, fits a variety of footwear.
• Features: light weight, cleanable.
• Considerations: indicated for mild foot drop.

• Order of bracing: rigid and sturdy to lightweight with less control. Rigid and sturdy as a principle is good for severe disease while less sturdy for early disease but not vice versa.

First line: AFO with laces, e.g. ARIZONA AFO

• Benefits: excellent control, comfort.
• Features: durability.
• Considerations: may require an extra depth/width shoe.

Second line: slim/light weight brace, e.g. AZ Breeze

• Benefits: good control, slim design for easier shoe fit.
• Features: light weight, washable.
• Considerations: less durable than leather, unable to heat to modify pressure spots.

Third line: articluated allowing some movement at ankle joint

• Benefits: enhanced mobility, excellent control.
• Features: lightweight, fits a variety of footwear.
• Considerations: not indicated for severe DJD or when support for the medial longitudinal arch is required.

 

 

 

Figure 11. Solid AFO (SAFO)

 

 

Figure 12. Hinged AFO (HAFO)

    

Figure 13 (a) and (b). Back & side View of AFO with cut out heel

Indications: Similar to AFO’s for Foot Drop, tendon Reconstruction/ Repair but allows eel to be cleared to avoid get pressure sores at heel. Not rigid enough so not suitable for deformity correction and severe OA / degeneration of Ankle.

 

Figure 14 (a) and (b). Example of a Dynamic Short AFO which makes rocking motion possible because of the gel insert (blue coloured) which attaches on the outside of the thermoplastic splint.

Benefits: balance enhancement, fits a variety of footwear

Features: light weight, cleanable

Considerations: indicated for mild foot drop

  

Figure 15 (a) and (b). Carbon Fiber AFO with rear entry (note padding at front) with foot elevated off the ground to allow to provide a rocking motion.

 Bracing for Degenerative Ankle Joint  /OA of Ankle:

Order of Bracing : rigid and sturdy to lightweight with less control. Rigid and sturdy as a principle is good for severe disease while less sturdy for early disease but not vice versa.

Figure 16. OA ankle

 1^st Line: AFO with Laces: e.g ARIZONA AFO

Benefits: excellent control, comfort

Features: durability

Considerations: may require an extra depth/width shoe

Figure 17. The Arizona AFO™ stabilizes the ankle, talocalcaneal, midtarsal and subtalar joints

2^nd  Line: Slim /Light Weight Brace: e.g AZ Breeze

Benefits: good control, slim design for easier shoe fit

Features: light weight, washable

Considerations: less durable than leather, unable to heat to modify pressure spots

3^rd Line: Articluated allowing some movement at Ankle Joint

Benefits: enhanced mobility, excellent control

Features: lightweight, fits a variety of footwear

Considerations: not indicated for severe DJD or when support for the medial longitudinal arch is required

Figure 19. Arizona Articulated AFO. The Articulated Arizona AFO is designed to stabilize the subtalar, talocalcaneal, and midtarsal joints while still allowing motion at the ankle. It is available with a variety of ankle joints and stops.

Figure 20. The successful fitting of Transtibial prosthesis is dependent on the fit of the hard socket. . Casting is used to help create a well fitting socket when an Iceross liner is being used. Inspect residue limb.Knowledge of anatomical landmarks,scarring and sensitive areas will aid in socket fitting.

Figure 21. Identify and mark the following:

• Patella
• Fibulla head
• Crest of tibia
• Other bony areas that may contact socket wall
• Sensitive areas
• Neuroma

Figure 22. The knee should be extended but relaxed.Apply Plaster of Paris to cover distal stump

Figure 23. Mould plaster from anterior to posterior defining the bony prominences and capturing residue limb shape

Figure 24. Modification of cast.Strip cast and ensure all marks are transferred to positive.

Figure 25. Workshop

Figure 26. Hip disarticulation prothesis.Amputations through the hip are commonly referred to as hip disarticulations

Figure 27. Transfemoral silicone locking prosthetic liner(Iceross) and pin

 

Figure 28 (a) and (b). Above elbow exoskeleton prosthesis

Figure 29. Above knee prosthesis.Transfemoral amputations are performed below the hip and above the knee.

Figure 30. Below knee prosthesis.transtibial amputations are performed below the knee and above the ankle

Figure 31. Above knee exoskeleton prosthesis

Figure 32. Various upper limb prostheses