Grading of anterolisthesis
Grading of anterolisthesis

What is Anterolisthesis?

Anterolisthesis is a spinal condition in which there is a forward slippage of a vertebral body in relation to the vertebra immediately below it. It is important to realise that this condition does not refer to bulging, herniated, or deformed intervertebral discs but is a condition of the bones themselves, although disc problems are also usually present in this condition. The name, like most medical terms, is modern Latin and it is derived from earlier Greek words: antero meaning forward or front and listhesis meaning slippage. A more comprehensive name for this condition is anterospondylolisthesis with the term spondylo indicating that the condition refers to the vertebrae.

Anterolisthesis is also commonly referred to as spondyolisthesis or simply listhesis but care should be taken to distinguish it from retrolisthesis which is a related condition in which the vertebral slippage occurs in a rearward direction. In anterolisthesis, the actual body of the vertebra is involved (the drum shaped circle of bone that surrounds the spinal cord) rather than simply a part of the vertebra such as one of the various processes or appendages. In cases where the vertebral displacement is due to trauma, such as in a car accident, it can occur at any point along the spine but it is by far the most commonly seen affecting the vertebrae of the lower spine where the lumbar vertebrae join the fused sacral vertebrae of the pelvis. More specifically, the joint between the upper sacral vertebra S1 and lower lumbar vertebra L5 is the usual location of this problem with the L4 lumbar vertebra sometimes being affected.

Anterolisthesis vs. Spondylolisthesis

The names anterolisthesis and spondylolisthesis are often regarded as being interchangeable and used as synonyms but this is not 100% correct as the latter makes no reference as to the direction of the slippage which can be forward, rearward (as in retrolisthesis / retrospondylolisthesis), lateral or any other direction but the former is much more specific referring only to forward vertebral displacement.

Anterolisthesis Causes

Spinal injuries from accidental causes may result in anterolisthesis at any point of the spine, with the possible exception of the C1 and C2 vertebrae, but even with this cause, the L5-S1 junction is particularly vulnerable due to the very heavy mechanical loading at this point. The spinal column is made up of many vertebrae which fit together in the manner of a three dimensional jigsaw puzzle. The joints between the individual vertebrae allow for a range of movement which varies depending on location in the spinal column. The joints are separated by the intervertebral discs which provide a cushioning effect and are held firmly in place by both the interlocking nature of the geometric shapes of the vertebrae and by strong ligaments.

A severe impact may cause damage such as a fracture to a specific part of a vertebra known as the pars interarticularis. This section of bone plays a major part in ensuring that the vertebra remains correctly located. In many cases, injury to the pars may initially occur in the teenage years and then go unnoticed for many years with chronic symptoms appearing later in life. In addition to accidents, high-impact sports may also result in pars injuries. In some cases the pars may have become misshaped and misaligned and in others it may have become elongated possibly as a result of several episodes of fracture and fusion.

There are other instances where spinal joint abnormalities may be genetic in origin. These abnormalities may be present at birth or the bones may exhibit abnormal growth (dysplastic development). Such problems are commonly seen on the joint faces of the L5 and S1 vertebrae. Age also plays a part with intervertebral discs tending to lose some of their bulk and resilience along with a general weakening of the tendons and other connective tissues resulting in a looser joint more susceptible to inappropriate movement. Osteoarthritis may further damage the joints and abnormal bone growth may occur resulting in a remodelling of the joint. There is also the possibility of joint damage from a pathological cause such as a severe infection or the presence of a malignant tumour. Some people are simply more prone to this condition than others but there are also environmental and lifestyle considerations. This section of the lower back carries the whole weight of the upper body and so care needs to be taken not to inflict any additional loading to the joints in this region. Heavy contact sports are fairly simple to avoid but even incorrect lifting, especially when lifting a load from one side of the body or twisting during the process of lifting, can cause anterolisthesis of a weakened spine. Lack of exercise or obesity may also be contributory factors as may be poor posture or long periods of sitting.

Grade 1 Anterolisthesis

The grading and classification of anterolisthesis is based not on the severity of the symptoms experienced but quite simply on the amount of movement of one vertebra with regard to its adjacent neighbour. Grade 1 is the lowest grade and regarded as the least severe, although physical symptoms vary from person to person. Grade 1 anterolisthesis may even exist as an asymptomatic (having no symptoms) condition. Such spinal conditions are extremely common and some studies have produced estimates that around 12% of the general population suffer from some degree of spondylolisthesis.

Anterolisthesis Grading

Although anterolisthesis is sometimes described simply as an amount of vertebral displacement measured in millimetres, it is more commonly graded having reference to the percentage of slippage present. This system of measurement looks at the amount of slippage and expresses it as a percentage of the front to rear dimension of the vertebral body at that location. In other words, if for example, the vertebral body measured 50mm and the amount of displacement was 25mm, this is described as 50% slippage. Four grades are normally used with Grade 1 being the least and Grade 4 the most severe. The boundaries between the grades lie at 25%, 50% and 75%. The term Grade 5 anterolisthesis may be encountered and this refers to the condition where the amount of slippage is in excess of 100% meaning that the rearmost part of the vertebral body is sited ahead of the anterior part of the vertebra below. This condition is more correctly called spondyloptosis.

Anterolisthesis Symptoms

The most severe types of anterolisthesis may result in a severe physical instability of the spine but many of the symptoms occur due to the trapping of nerves, usually at the points where they exit the spine via openings known as foramina. This is known as foraminal stenosis. It is also possible for the spinal cord itself to be compressed as it passes through the centres of the vertebrae in a condition known as central spinal stenosis. Perhaps the most obvious symptom is back pain and this can range from mild to severe. Pain, weakness and numbness are often experienced affecting the buttocks and running down to the thigh and sometimes the calf. This is most frequently unilateral, affecting just one side of the body, but can be bilateral affecting both sides. Spasms of the muscles of the lower back may be experienced along with a tightness of the hamstrings and leg muscles. In some severe cases, there may be problems in controlling bowel and bladder functions and a feeling of numbness affecting the buttocks and inside of the thighs and groin area. This is known as cauda equina syndrome and is sometimes termed saddle anesthesia. Sufferers of severe anterolisthesis may develop a modified waddling gait and a change in body posture with increased lordosis (this is the forward spinal curvature in the area sometimes referred to as the small of the back).

Anterolisthesis Diagnosis and Treatment

Consideration of the symptoms present is likely to give a strong indication of some form of listhesis but confirmation relies on the use of X-rays and possibly MRI or CT scans. Only then is it possible to know the position, type and severity of the problem. In the majority of cases, especially with Grades 1 and 2, a conservative treatment regime is the preferred option. The first recommendation is a period of rest in order to allow the inflamed area to settle down.

Anti-inflammatory painkillers are also useful at this stage and these may be over-the-counter products such as ibuprofen or a doctor may offer a stronger, prescription-only drug if considered appropriate. Some level of movement and exercise is recommended but care must be taken not to aggravate the problem so everything must be kept as gentle as possible. Once the initial inflammation has subsided, physiotherapy can play a part and there are many stretching and strengthening exercises which can help both the back and the legs. It is important to follow an exercise programme drawn up by a qualified professional rather than attempting a “DIY” approach. Health professionals will know exactly which nerves are being affected and tailor the treatment accordingly.

Manipulative therapy may also offer some relief but it is important to realise that there is no way of simply clicking a displaced bone back into place. Even more severe grades of anterolisthesis may be effectively treated using conservative, non-invasive, methods but in some cases greater levels of intervention may be needed. Where there is serious instability of the spine, a back brace may be used but such use is controversial as many experts believe that such a brace actually causes a further weakening of the spine. Surgery is often regarded as a last resort and it must be said that spinal surgery is not without risks but the good news is that surgical procedures to remedy this problem have a very high success rate. The precise procedure will of course depend on the specific problems with no two cases being the same but one of the most common procedures is known as interbody-fusion and in this the surgeon actually fuses one vertebra to the one below it. Screws are usually employed which remain in-situ and the disc from the offending joint is normally removed and replaced with a “cage” seeded with bone fragments which then grow to form a strong permanent bond. Bone grafts are taken from another part of the patient’s body. This is a complex operation which is carried out under a general anesthetic.

Anterolisthesis has been around ever since man decided to walk on two legs but fortunately with today’s treatments it no longer has to be the debilitating condition that it once was and although there may be some loss of previous levels of fitness and mobility, most people go on to make a good recovery.


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