Gait in prosthetic rehabilitation
A complete cycle of gait begins at initial contact of one limb and ends at the repeated initial contact of the same limb, performing all phases of gait in doing so. This full cycle can be described as a stride. A step is sometimes incorrectly used to describe this cycle. A step however, is different; it is described as the distance of heel strike from one leg to the heel strike of the opposite leg.
The gait cycle can be split into 2 stages;
- Stance Phase -Time the foot is in contact with the floor, weight acceptance and single leg stance, which makes up 60% of the cycle
- Swing Phase – The period of time where the limb is lifted from the floor, limb advancement. This makes up 40% of the cycle
- Initial Contact
- Loading Response
- Terminal Stance
- Initial Swing
- Terminal Swing
The diagram demonstrates this division of gait cycle.
Also known as heel strike. This is the first moment the foot comes into contact with the floor. The hip is flexed approximately to 30 degrees , knee extended between 0-5 degrees and ankle dorsiflexed to a neutral position, giving contact with the floor at approximately a 25 degree angle. This is the first phase of double limb support. The aim of initial contact is to stabilise the limb in preparation for it to take the impending forward translation of body weight.
The foot flattens on the floor through pronation. The hip begins to extend and propels the body forwards and over the foot, using the heel as a ‘rocker’. The knee then flexes to allow shock absorption. The aim of this phase is shock absorption, weight bearing stability and preservation of progression.
This is the first half of single limb support. Weight is aligned fully over the supporting foot through ankle dorsiflexion, while the hip and knee extend, as the other foot lifts off the floor. The body weight is fully supported on one leg.
This is the second half of single leg support; it begins as the other leg lifts off the floor. The heel of the loaded limb lifts off the floor and the body weight moves forward past the forefoot, as the hip increases in extension. The knee gains full extension and begins to flex again. This phase is completed when the non-loaded limb makes contact with the floor.
Also known as ‘toe off’ and is the final phase of stance. The other limb has now begun a new stance phase and is in the initial contact phase. The limb is rapidly off loaded with a forward push to transfer the weight onto the opposite limb. The knee is flexed and the ankle plantarflexes as the toe leaves the ground.
The foot is lifted off the floor by hip and knee flexion, as the ankle begins to dorsiflex. The other foot will be in midstance phase. When the off loading limb is level with the leg in stance phase the initial swing phase is complete.
The limb swings forward of the body through hip flexion as the knee begins to extend. The foot is clear of the floor
Also known as late swing, the knee becomes fully extended and the ankle dorsiflexes to neutral as the foot prepares to make contact with the floor.
The diagram below demonstrates the 8 phases of the gait cycle:
After an amputation the amputee uses different muscle groups in order to create a smoother gait pattern. Overall energy consumption required is higher, due to the increased effort required to compensate for the lose of the limb. The amount of metabolic oxygen consumption in a non amputee correlates directly to increased walking distance and speeds. In the amputees, however, this metabolic cost is higher even at normal speed. On average these increased requirements are:
- Traumatic Transtibial Gait - 25% increased energy requirement
- Vascular Transtibial Gait - 40 % increased energy requiremeny
- Traumatic Transfemoral Gait - 68% increased energy requirement
- Vascular Transfemoral Gait -100% increased energy requirement
The average gait pattern will vary dependent on the type of prosthesis used for mobility, however generalisations can be made. The ankle of the prosthesis has a reduced range of movement compared to the anatomical ankle. This results in prolonged heel strike and weight bearing through the heel before flat foot contact, with delayed forefoot loading
Knee flexion is decreased at initial contact and the overall maximum flexion achieved is reduced as the foot moves to floor contact to. During swing phase of the non prosthetic limb the body weight begins to move forward over the prosthetic limb, which is in stance phase. In order to gain adequate step length of the non prosthetic limb, heel rise on the prosthesis occurs earlier. The heel rise achieved is greater than that of a normal gait pattern. This creates an elevation of the body and results in a greater loading force on the non prosthetic side (approx 130% compared to average 111%) as the body weight drops more rapidly onto the limb. Greater quadriceps contraction is needed to absorb the force. The ‘toe off’ force generated from the prosthetic limb is reduced, which is compensated for by the hip flexors. Flexion of the knee on the prosthetic limb occurs with some hamstring contraction but mainly eccentric contraction of the quadriceps
During the stance phase the energy generated by the prosthetic limb is reduced by 50% to that which would be generated by the normal limb, this is compensated by greater energy expenditure in muscles higher up the limb. The rocker effect of the prosthesis results in increased instability and the reduced knee flexion achieved on the prosthetic side requires hip muscles to generate greater energy to ensure stability. As the body transfers weight in a forward motion this energy generation is then transmitted to the trunk muscles in order to generate enough force to propel the body forward and to compensate for the loss of energy through the prosthesis.
Due to the reduced ankle movement of the prosthesis the range of extension at the hip is reduced to approx half of that of the opposite limb. The stance time on the non prosthetic side is also increased compared to the prosthetic side.
A person with a transfemoral amputation has to compensate for the loss of both the knee and ankle joint. The gait cycle is affected by the quality of the surgery, the type and alignment of prosthesis, the condition of the stump and the length of the remaining muscular structure and how well these are reattached.
The main focus of the gait cycle is to prevent the knee from buckling during stance phase. A ‘fixed knee’ prosthesis will counteract this issue. A ‘free knee’ will need to remain in extension for longer throughout the stance phase approx 30-40% to ensure buckling does not occur. This extension causes prolonged heel strike and the body will move forward over the prosthetic leg as one unit for stance phase. The hip extensors on the prosthetic side will work to stabilise the limb in prosthetic weight bearing.
During swing phase of the prosthetic limb the hip extensors and calf muscles on the non prosthetic side help to generate force for the non prosthetic limb to gain swing forwards. Hip flexors on the prosthetic limb must generate the same force required during normal gait. Although the prosthesis is generally 30% lighter than the limb would be, speed generated by the hip flexors is required in order to snap the prosthesis of a ‘free knee’ into extension for heel strike. General control and strength is reduced in a transfemoral amputation due to the shortened lever length of the thigh muscles, which reduces the force of contraction. For amputees with a fixed knee prosthesis floor clearance is reduced during swing phase, due to the lack of knee flexion and ankle dorsi flexion. Elevation of the hip using trunk and hip muscles is required to prevent dragging on the floor known as ‘hip hitching’ or ‘hip hiking’. Stance time on the non prosthetic limb is increased as it is for transtibial amputees, because of the instability resulting from the prosthesis and the reduced range of motion available. Overall energy expenditure is higher than is required for a transtibial amputee due to the energy which is lost through the prosthesis over two joints and not one. Greater compensation is required by the hip and trunk muscles and the contra lateral limb to generate the energy required for stability and movement throughout the gait cycle.
While assessing amputee gait it is important to be aware of normal gait and how normal gait in the amputee is affected. Furthermore there may be deviations which an amputee will adopt to compensate for the prosthesis, muscle weakness or tightening, lack of balance and fear. These deviations create an altered gait pattern and it is important that these are recognised, as rehabilitation of the gait will need to encompass corrections of these deviations.
Learn about common gait deviations on the Gait deviations in amputees page.
Amputees should have a full functional and physical assessment and rehabilitation should be based around personalised functional goals. Individualised exercise programmes are developed thorough assessment. An awareness of normal gait and the deviations and their cause formulates the basis of the correct rehabilitation of the individual. There are numerous techniques that can be used during rehabilitation and not all of them will be appropriate for each individual, therefore the programme and technique must be applied to each individual and reviewed regularly to ensure it remains adequate. The amputee’s previous level of activity, overall health and potential to improve needs to be taken into consideration when formulating a rehabilitation programme and should aim at translating the function gained in a controlled environment into their own home functional environment.
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