Abstract
Orthotics and prosthetics is a subject often neglected during revision, but is an important topic because various aspects may be incorporated into other topics, such as gait, hand injuries or amputations.
This chapter attempts to cover the concepts that have been tested previously in the FRCS (Tr & Orth) exam. The questions and answers provide a high-order thinking framework to build on your answer in the exam oral tables.
Candidates are likely to be shown a clinical photograph, followed by a starting question. You are not normally marked on the starting question – it serves to melt the ice and give you confidence to get going.
Introduction
Orthotics and prosthetics is a subject often neglected during revision, but is an important topic because various aspects may be incorporated into other topics, such as gait, hand injuries or amputations.
This chapter attempts to cover the concepts that have been tested previously in the FRCS (Tr & Orth) exam. The questions and answers provide a high-order thinking framework to build on your answer in the exam oral tables.
Candidates are likely to be shown a clinical photograph, followed by a starting question. You are not normally marked on the starting question – it serves to melt the ice and give you confidence to get going. This will be followed by a competency question, which is a pass–fail benchmark. Once achieved, the examiners will then move on to advanced questions to give you higher scores.
Remember that examiners are looking for a logical and confident approach, testing your higher-order thinking in the application and evaluation of clinical knowledge.
Learn to draw as you talk, this will assist the examiners to understand what you are drawing, especially if your artistic skills are not the best! It will look and feel very awkward to draw silently while examiners are looking at you! Talking while drawing will also save you time and make you look more confident about the topic.
The topics discussed within this chapter are interchangeable, and answers can be mixed according to the scenarios given. Therefore, agility and the ability to adapt your answer to the specific question asked is an essential skill for the FRCS exam, and this is best mastered through repeated practice with other exam candidates and consultants.
Candidates can also be asked about orthotics and prosthetics in both the MCQ and clinical components of the exam. This chapter also helps to cover the knowledge and skills required for these parts of the exam.
Orthotics
EXAMINER: [Hands the candidate a picture of an orthosis] What is an orthosis?
CANDIDATE: The definition that is endorsed by the International Society for Prosthetics and Orthotics is a device that is externally attached to the body to improve function.
It supports weak muscles and corrects or compensates for skeletal deformity.
EXAMINER: What are the ideal characteristics of an orthosis?
CANDIDATE: The ideal orthotic should be effective, lightweight, cosmetically acceptable, easy to put on and take off, and comfortable.
EXAMINER: What are the different types of orthotics that you know of? Can you give me examples of each?
CANDIDATE: Orthoses can be classified according to function into corrective and accommodative.
The corrective ones tend to be hard. They limit joint motion and stabilize flexible deformities. An example is the rocker sole that can lessen the bending forces on an arthritic or stiff midfoot during the midstance as the foot changes from accepting the weight-bearing load to pushing off. It is also useful in treating metatarsalgia and hallux rigidus.
The accommodative ones tend to be soft to allow them to shock-absorb and to accommodate fixed deformities, such as various pressure-relieving insoles that are used to dissipate local pressures over bony prominences to treat diabetic foot.
Sometimes the same orthotic can be used for support and/or correction. An example is the TLSO, which can be supportive in the case of fractures or corrective in the case of idiopathic scoliosis. Another example is the AFO, which can be supportive for weak muscle in polio or corrective in cerebral palsy.
EXAMINER: What different materials are used to make orthotics?
CANDIDATE: Orthotic materials need to be light, strong and sufficiently hard-wearing to survive for the duration of their intended use.
Various materials can be used, such as metal, plaster of Paris, carbon fibre, silicone, leather and plastic.
EXAMINER: [Shows a photo] Can you tell me what this orthosis is made of and the different types of this material that can be used to make an orthosis (Figure 22.1b)?
CANDIDATE: This is made of plastic. Plastic can be thermosetting or thermoforming.
Thermosetting plastics are pliable above a certain temperature and return to solid upon cooling. They are hard and difficult to fabricate as they require high temperature to be moulded. However, they are durable, which makes them good for making prostheses and orthoses that are to be put under great stress.
Thermoforming plastics have the advantage of allowing to be reshaped by reheating. They can be moulded at high temperatures, such as those used to make AFO (e.g. polyethylene), or a medium temperature, which can be moulded directly on the patients as they have low heat conductivity (e.g. Plastozote). Or moulded at low temperature for making hand therapy splints in clinic; these can be modified if required by gentle heating in water or by a hair dryer (e.g. orthoplast).
CANDIDATE: They work according to the three-point pressure principle to control the forces on the body part. This is the same principle that was proposed by Sir Charnley for fracture immobilization.
To control joint movements, one force should be over the joint and the other two act in the opposite direction to the first one.
COMMENT: It would be preferable here to ask for a piece of paper and ‘draw as you talk’.
EXAMINER: [Shows the candidate a picture of an orthosis (Figure 22.1d)] Can you describe this orthosis for me?
COMMENT: This can be anything! It could be something you have never seen. It doesn’t really matter. Chances are that the examiner also didn’t know before the start of the exam. Stick to the below principles and you will impress any examiner.
Start describing the part of the body it supports such as AFO, KAFO, etc.
In the 1960s the American Academy of Orthopaedic surgeons suggested standard reproducible terminology of orthoses. Described by the joint or region of the body it encompasses.
Figure 22.1a Orthosis (courtesy of Blatchford).
Figure 22.1b Plastic foot drop splint (courtesy Blanchford).
Figure 22.1c Three-point pressure principle for an orthotic.
