5. improved functional ability and lower dependency; 6. shorter rehabilitation period; 7. cheaper prosthesis as compared to the above-knee prosthesis.
Modern transtibial prostheses are built from modular components.
There is a multitude of components available along with numerous socket concepts that can be applied to this common level of amputation.
Choices are based on the individual user’s presentation.
Specific to the diabetic person is that sensation as well as healing capacity may be impaired in the residual limb.
Neuropathy in the contralateral leg may reduce proprioception, affecting balance and increasing risk.
Hand function and vision may be impaired.
These factors need to be considered when determining the prosthetic specification.
Good suspension is important in order to maximise proprioception and minimise ground impact on the residual limb during ambulation.
The suspension is a function of the interface (socket design) that connects the prosthesis to the residual limb.
Materials such as silicones and polyurethanes that combine good suspension and pressure-distributing properties are used in either prefabri- cated or bespoke interface stump sleeves.
A lightweight modular system (Figure 27.3) and a reasonably responsive composite foot help to minimise the energy loss associated with pros- thetic use.
Knee Disarticulation (Through-Knee) Amputation This is considered to be an atraumatic surgical procedure that involves no disturbance to the bone. It is especially indicated when the patient’s general condition is poor and a decision has been made that the patient will not (for other medical reasons) be a suitable candidate for mobilisation with a prosthesis. Functioning hamstrings allow controlled hip extension, thereby
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332 REHABILITATION OF THE AMPUTEE WITH DIABETES
(a) (b)
(c) (d)
Figure 27.3 (a,b) A 79-year-old man with type 2 diabetes; (c) fitted with appropriate appliances; (d) functions as community ambulator
improving sitting balance, as compared to the transfemoral amputation.
Knee disarticulation produces a very strong, functional level of amputation because of the long skeletal lever and the natural ability of the femoral condyles to carry weight.
Nevertheless, it is not very commonly done, perhaps due to the restricted prosthetic solutions, which makes it cosmetically and biomechanically mismatched when compared to the contralateral knee.
As in the case of ankle amputation, the shape of the residuum may be bulbous distally due to the presence of the femoral condyles.
When designing the prosthetic socket, access traps and differential liners allow a wider circumference to enter through a narrower section of the socket.
Differential liners are flexible inner sockets, which have been built up on the outside of the narrower sections to form an almost uniform external circumference, enough
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LEVELS OF AMPUTATION 333
to allow the bulbous portion of the residuum to pass through the narrower section during donning.
Consequently, the rigid outer socket with marginal undercut will help to maintain good suspension of the prosthesis.
As the femur retains its full length, the prosthetic knee joint will inevitably be placed below the level of the anatomical knee joint of the contralateral side.
This causes a thigh segment length discrepancy that is particularly noticeable whilst sitting.
The effect can be minimised by the use of polycentric knee joints.
These knee joints have a complex centre of rotation, typically involving four axes.
As a result, they protrude less than single axis knees when flexed, making the prosthesis cosmetically more acceptable.
The restricted space for knee components also limits the functionality of the knee.
The choice of foot component is dependent on the type of knee in use.
Transfemoral (Above-Knee) Amputation Transfemoral amputations should only rarely be performed on people with diabetes.
At surgery, about 12, 15 cm of distal femur should be removed and the thigh muscles should be reattached to the femoral end in order to avoid muscle retraction.
Secure attachment of the hip adductors as advocated by Gotschalk18 allows better control of the stump within the prosthetic socket.
When amputation takes place at this level because of diabetes, the patient’s general health is likely to be poor and the functional deficit is likely to be considerable.
The loss of the knee joint and shortening of the femur limits propulsive power and control of the prosthesis.
The increase in energy expenditure when walking is significant.
Consequently, the weight of the prosthesis needs to be kept to a minimum.
Critical for safe ambulation is the user’s ability to control the prosthetic knee joint.
Many different knees are available, featuring varying degrees of functionality and safety.
In general terms, increased functionality results in increased weight of the component.
In practice, this often restricts the choice of knee joints for diabetic patients.
For the lowest functional levels, a locked knee joint can be used to achieve safe low-level ambulation with a stiff knee.
The knee is manually unlocked when the user wants to sit down and locks automatically when the knee is fully extended for standing.
The prosthetic foot choice is dependent on the type of knee in use.
Such components are light and safe but result in an uncosmetic, asymmetric, high-energy gait.
For the more able person, sophisticated hydraulic and microprocessor swing/stance control are available.
Suspension is important as it contributes to the control of the prosthesis.
The stump is often cylindrical in cross section.
Therefore, rotational stability of the prosthesis may be difficult to achieve and there will occasionally be a requirement to add auxiliary suspension such as a belt around the waist.
Second Limb (Bilateral Amputations) For people with diabetes, there is a significant chance of loosing the second limb.
Before undertaking surgery, it is important to assess the patient’s medical condition.
Should there be a good chance of walking and prosthetic rehabilitation is to be considered, only the most distal amputation possible should be performed.
On the other hand, if the person is too ill and unlikely to walk, the amputation should be designed to allow good sitting balance and ease of transfers.
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334 REHABILITATION OF THE AMPUTEE WITH DIABETES
PROBLEMS PARTICULAR TO THE PERSON WITH DIABETES Fluctuating stump volume is associated with the occurrence of cardiac failure and nephropathy.
This makes fitting an accurate prosthetic socket extremely difficult.
Such patients require regular prosthetic adjustment and review.
Using two or more stump socks when measuring for the prosthetic socket allows flexibility in coping with the fluctuating stump volume.
Impaired vision makes accurate donning and doffing of the prosthesis extremely difficult.
Walking, particularly over uneven surfaces, can be hazardous.
Many of these patients restrict walking to indoors, or when outdoors link arms with a companion.
Peripheral neuropathy is generally associated with poor balance,19 and increases the risk of falling.
Cheiroarthropathy (limited joint mobility) and muscle wasting are common in people with diabetes.
When determining the prosthetic specification, consideration needs to be given to any loss of hand function and/or vision impairment, as the complexity of the donning and doffing process can vary.
If at all possible, the goal should be for an individual to be able to don and doff the prosthesis independently.
CONCLUDING REMARKS Diabetes is a medical condition that affects multiple systems.
Limb amputation is only one part of the picture.
Simply replacing the lost limb with a prosthesis will produce an unsatisfactory result.
The coordinated efforts of a multidisciplinary team are crucial in providing physical, psychological, social and environmental support.
The rehabilitation team has an extended duty to help the amputees in their return to society.
Lord Holderness, politician, soldier, campaigner for the disabled and double above-knee amputee, summed it up when he said, ‘Rehabilitation converts a patient back into a person’.