Dysmetria (short leg) of the lower limbs (DMI) is defined as the difference or discrepancy in the length of the lower limbs; either by excess (hypermetry), or what is more frequent by default (hypometry). It is a pathology of frequent consultation since when the magnitude of the difference is important it leads to lameness.
It is quite common, about 10% of “normal” individuals, without pathologies or disabilities, have a length difference of less than 10mm,
When it is very small, it is barely noticeable and the body resolves it by itself by adapting to the imbalance, but if it is greater than 1cm, it needs treatment as it has ascending consequences in the ankle, knee, hip, imbalance in the pelvis and even scoliosis in the spinal column. It is considered a dynamic process, which can vary, until the patient reaches bone maturation, since it depends on the growth cartilage.
Short leg or Dysmetria. False or true?
This is a crucial concept when we talk about dysmetria or short legs, since it must completely mark the treatment and approach to this problem so that we will or will not put a lift to compensate for the dysmetria according to this differentiation.
Origin or etiology of lower limb Dysmetria or short leg
True lower limb length discrepancy has a multifactorial origin, which can be:
- Idiopathic There is no known cause for dysmetria.
- Congenital There are multiple causes, some are: agenesis (absence) of the fibula, clubfoot, coxa vara, congenital hip dislocation.
- Infectious Osteomyelitis, septic arthritis.
- Traumatic Sequelae of growth cartilage breakage , shortening of the bone body due to fracture.
- Other causes Perthes disease, radiotherapy, surgery.
Leg discrepancy. True or false?
When we are faced with a dysmetria or discrepancy in the length of the lower limbs, we can talk about:
1. Actual shortening or true short leg (true Dysmetria)
The length of the leg bones is actually different between the two legs for some of the above reasons.
2. Apparent shortening or false short leg (false Dysmetria)
They are mainly due to alterations in the alignment of the legs or inclinations in the back area due to scoliosis or muscular contractures or vertebral blockages, due to sacroiliac and pelvic dysfunction or alteration, any problem in the back can cause a false dysmetria.
When the problem in the spine and pelvis disappears, the dysmetria disappears, for this reason it is called false dysmetria because, in reality, with the help of a physiotherapist, the original size of the leg can be restored.
Symptoms of dysmetria in the lower limbs
A patient with lower limb dysmetria is prone to certain muscle pain, especially in the back area, as well as pain or discomfort in the knees as a result of the difference in the length of one leg and the other.
This is why, on many occasions, lower limb dysmetria can be misdiagnosed or confused with another pathology and not treated properly. In addition, the patient may present:
- Gait disturbance
- Scoliotic postures
Causes of lower limb Dysmetria
The causes of lower limb dysmetria can be congenital or acquired at some point in life for the following reasons:
- Congenital anomalies
- Developmental disorders
- Caused by trauma
- Neuromuscular-type diseases
- Inflammatory processes
Effects or consequences of dysmetria in lower limbs
The fact that the difference between the length of the legs or dysmetria can be more or less pronounced and this degree of difference can be the consequence of multiple pathologies.
In any case, these repercussions do not occur in all cases and will often be linked or caused by other added factors. In other words, it would be incorrect to blame dysmetria for all our pain and dysfunction in general.
List of the most significant problems:
There are problems that people who have lower limb dysmetria experience, whether true or false, but as long as it is present, it may exist:
- When there is dysmetria of the lower limbs due to overload of the quadratus lumborum and the paravertebral muscles, a functional lumbar scoliosis usually develops .
- Lower limb dysmetria contributes to low back pain by imposing chronic muscle tension and overload.
- It only contributes to myofascial pain syndromes if chronic overstress activates trigger points in overworked muscles.
- It appears to contribute significantly to the development of degenerative hip osteoarthritis on the side of the longer lower limb, which can also occur in the scoliotic spine.
- Appearance of compensatory spinal scoliosis in standing. To avoid this, the patient places the long limb to one side or forward, loading on the short limb, thus leveling the pelvis.
- Alteration of the gait scheme; the individual with dysmetria may keep the pelvis level at the expense of forced plantar flexion and, as a consequence, possible overloading of the gluteal muscles.
- Appearance of an associated pelvic torsion, a posterior rotation of the iliacus on the long side that lowers the sacrum or vice versa, an anterior rotation of the iliacus on the short side to ascend the sacrum.
Classification of dysmetria or short legs
Dysmetries or discrepancies in length in the lower limbs are classified according to the centimeters of difference that exists between one leg with respect to the other, ranging from the smallest degree, which will be a discrepancy of less than 1 cm, to a difference of 10 centimeters or more. Below we detail the classification of lower limb dysmetries.
1. Dysmetria less than 1 cm
They are by far the most frequent and do not require treatment since they do not cause gait disturbances or cause scoliosis.
Some podiatrists and rehabilitators assume that they are the cause of low back pain and that they improve when a rise (insole) is placed.
2. Discrepancy between 1.5 – 4 cm
Placement of a riser to compensate for the difference in length of the lower extremities, with more complications than the previous one and with a fall of one hemipelvis, if the riser is not placed, the imbalance of the hemipelvis is great, in this one it can be easily presented scoliosis and associated problems.
3. Discrepancy between 4 – 10 cm
This dysmetria is recovered with a progressive bone elongation using an external fixator, a surgical fracture of the bone and progressive lengthening of the bone is applied to the extent that it generates bone callus, this surgery of course must be performed by an expert doctor and perform exact measurements with imaging techniques. as well as post-operative follow-up.
4. Discrepancy greater than 10 cm
They are really the most complex cases to deal with. The first option offered to the patient is surgical abstention of the limb, that is, amputation and use of prostheses.
How is lower limb dysmetria diagnosed?
To diagnose lower limb dysmetria, it is necessary to carry out a general physical evaluation of the patient, as well as to practice radiological techniques where the difference in length between the legs is evidenced, in order to have an exact idea of the difference between the legs. exists between both limbs and based on this discern which will be the most appropriate treatment protocol to treat the difference in length between both legs or lower limb dysmetria.
How can I measure my dysmetria?
There is a somewhat orthodox method but it works and you can do at home to quantify the degree of dysmetria, and for this you will need an assistant who must place their hands on your iliac crests of the pelvis so that the crest fits between your thumb and index of both hands, in this way you can see if a hemipelvis, that is, one half of the pelvis is dropped, then it means that you have to place a riser on the side of the dropped pelvis to compensate, for this we are going to use a any book this book on the floor will be the rise where the person must step on it, then depending on the number of pages that we place we can determine how big the dysmetria is.
Treatment of dysmetria or true and false short leg
There are different therapeutic methods to compensate for dysmetria depending on the magnitude of the discrepancy, prognosis, aetiology, height and age.
1. Boost or template
In order to compensate for the shortening of the discrepancy, an insole can be used that is placed inside the shoe and that will have the thickness that we decide to compensate for the discrepancy. Of course, it will be important that the measurement is done correctly since many templates or risers are currently put on false short legs.
2. Added in footwear
In discrepancies greater than 0.75 to 1 cm and depending on the footwear used by the person, we will not be able to put the entire measurement on the insole because we may have difficulty getting the foot into the shoe and a fixed part must be added by adding it to the sole, work that a shoemaker will have to do and that in any case can only be done on shoes with a more or less smooth sole.
3. Surgical solution
n much larger dysmetries, only surgery will be left to definitively correct this difference in length. I leave you an article that describes the surgical technique used
This type of lift should never be used in false dysmetria, since in this case the apparent difference in length is the consequence of an imbalance in the pelvis and spine that must be the objective to be treated by the physiotherapist.
Dysmetria is a condition that will have excellent results with the evaluation and treatment of a doctor specialized in traumatology and orthopedics, a podiatrist and a physiotherapist, since in general, to correct the deformity, an increase (insoles) must be indicated, which must be comfortable and for prolonged use.
In addition, the footprint must be corrected and the physiotherapist must apply the necessary techniques for the proper functioning of the joints and muscles, including the lower back (whether or not it has suffered from scoliosis as a result of the discrepancy), the hips, knees and ankles, indicate exercises for an optimal gait.
Since the body was previously adapted to the dysmetria that when placing the rear sight feels strange again, pain may appear in other places.