Mary Tebb – Specialist prosthetic physiotherapist at the Southern Clinic
Many of our clients with lower limb loss report that they have low back pain. In fact, it’s more common to have back pain as an amputee than to not have it, with researchers reporting 52%-89.6% occurrence. This is significantly higher than for the non-amputee population. There is also a tendency for greater levels of back pain if the amputation is at a higher level with above knee amputees reporting more pain than below knee amputees. For many, back pain is more of a problem than stump pain or phantom limb pain.
So why do amputees get low back pain, where is the pain coming from and what can be done about it? Well, all these questions have been researched and reported on and I will try to summarise what we do and don’t know.
Firstly, why do so many amputees get back pain? Well, there are many factors to consider here, some which you may not have appreciated. The obvious is that the walking pattern of an amputee will never be completely natural and that this will cause a change in the loading pattern up through the spine and a consequent change in muscle activity. For most amputees, there is a notable weakness on the side of the amputation and also a change in how muscles are recruited with some effectively trying too hard and some becoming a bit lazy. For example, with the loss of normal thigh muscles in an above knee amputee, the back muscles have to work harder on that side to propel the leg backwards when walking. Also, when there is no calf muscle, there is a loss of propulsion on the amputated side, resulting in more muscle work required from the intact side.
Take a look at some still shots of one of our clients who is an above knee amputee. Note how, in the first picture, his bodyweight is taken on the intact leg and the body is nicely upright due to the muscles working correctly and effectively throughout his left side. In the second picture, his bodyweight is thrown over to the right as he weight bears onto this side. This is due to weakness in his right gluteus medius muscle – the muscle which forms the upper outer third of the buttock and is responsible for a lot of stability around the pelvis and hip. Gluteus medius is like a guy rope on a tent, anchoring the pelvis to the leg to keep the body upright. This muscle frequently becomes “lazy” and often needs specifically targeting in exercise programmes to regain its correct pattern of movement. When it is weak, the trunk rocks to the side as in the picture, using bodyweight to maintain balance.
There are many good exercises to target gluteus medius, probably the most useful being the “step touch” exercise. Here, the intact leg repeatedly touches a step whilst the weight is taken on the prosthetic side and hand support is gradually removed whilst an upright posture maintained.
Secondly, where is the pain coming from? Again, this has been researched with the scans and X-rays of non-amputees and amputees being compared. What has been found is that there is no significant difference in joint problems between age-matched individuals. This means that the normal process of joint wear in the joints of the spine seem to be the same regardless of whether someone is an amputee or not. Not so in the opposite hip and knee joints, but that’s another article. So if the pain is not joint related for many, the conclusion is that it is from the soft tissues – the muscles in particular but also the tendons and the ligaments. Interestingly, modern pain science describes how repeatedly annoying structures such as these can lead to a phenomena known as “sensitisation”. This is a bit like nagging a teenager to do their homework again and again and the consequent over-reaction you get from them after the umpteenth polite request to get their books out! However, whilst most teenagers calm down after a while, the body stays in a state of sensitisation and the next time the structure is annoyed, yet more pain results. Annoyingly, there are other influences on how sensitised a structure can become and these occur within the brain. Depression, anxiety and stress, which are common health problems following amputation, are all known to exacerbate sensitisation. This is why psychological therapies such as mindfulness and cognitive behavioural therapy can be helpful for managing pain.
Muscles which have to work harder for prolonged periods of time than they are capable of will eventually complain. Fortunately, they are quite forgiving and most back pain usually settles down with rest. This allows any “micro-damage” to quickly repair as muscles have a great blood supply and can heal quickly. However, a reduction in pain at rest can often make it feel like rest is the answer and the sufferer will default to this as a treatment strategy which is not a good idea as muscles will then get weaker and more deconditioned, so perpetuating the cycle of overload and consequent pain.
So what can be done about low back pain for amputees? Well, there are many approaches to tackling this problem with no “one size fits all” unfortunately. Clearly, a well-fitting prosthetic leg with the right componentry for the amputee is of paramount importance – fighting to keep an ill-fitting socket on or having an unreliable knee will easily annoy those already overworked muscles. Having had a few falls also increases inappropriate muscle tension throughout the body and aggravates pain. With the right prosthesis, challenging exercises to both strengthen muscles and prompt them to switch on at the right time in the gait cycle is also very important. The most important set of muscles seems to be the gluteals, or buttock muscles, with evidence showing that just working on these twice a week for eight weeks can make a difference to functional performance. Alongside improving muscle strength, improving muscle endurance is also helpful.Let me explain this further.
There are essentially two types of muscle fibres, known as type 1 and type 2 -
Type 1 - Muscle fibres are also known as slow twitch fibres; they contract slowly but are able to keep going for longer periods of time, using oxygen as their main source of energy. Muscles which are involved in keeping you upright, your postural muscles, or core muscles, have mainly type 1 fibres in them. Think of a chicken. The brown meat found in the legs is mainly made of type 1 fibres as a chicken spends a lot of time walking around and scratching at the ground.
Type 2 - The chicken breast, however, is white meat. This is mainly made up of type 2 fibres, also known as fast twitch fibres and these use a different form of energy. These muscles in a chicken are used for short bursts of flights which it can’t sustain as the muscle runs out of energy quickly. In humans, type 2 fibres are mainly found in our power muscles, the ones just under the skin that give us our contours. Strengthening both these types of muscles for the amputee will generally improve the walking pattern and hence reduce low back pain. However, strengthening in isolation without the trained eye of a physiotherapist may not allow you to reap the full benefits of such improved fitness. Many amputees get into bad habits which need correcting with repetition and continued input. Also bear in mind the greater amount of energy that amputees use when walking and we begin to see why improving strength and endurance is so important.
Sometimes, passive therapies can be helpful for low back pain in both amputees and the general population. These might include joint manipulation, stretching, acupuncture, massage and a whole host of more alternative treatments. Bear in mind though, that when various therapies and treatments are researched in clinical trials, exercise invariably comes out tops. Indeed, many studies are unable to support either a short or long term effect from passive therapies used for low back pain.
I hope this brief overview of low back pain in amputees has been helpful.
If you would like your back pain assessed and an exercise programme devised specifically for you, please feel free to book an appointment with one of our physiotherapists by emailing firstname.lastname@example.org or calling 0800 433 2239