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Spondylolysis and Spondylolisthesis: when a lumbar vertebra "slips"

Today instead we will talk about a particular form of back pain that affects a smaller number of dancers but that must be monitored with caution both by doctors and dance teachers: in this case the low back pain is linked to the presence of an interruption of the isthmus of the vertebra (spondylolysis) which, if bilateral, allows the sliding of the body of a vertebra with respect to that of the underlying vertebra (spondylolisthesis).


  To better understand the characteristics of this pathological condition, it is necessary to remember that each vertebra is composed of a cylindrical anterior portion called body and a posterior portion, horseshoe-shaped, called vertebral arch, from which various extensions start: a spinous process, two transverse processes and four joint processes, of which two are upper and two are lower.




With the term isthmus (or pars interarticularis), a restricted portion of the posterior arch of the vertebra is indicated which is between the upper and lower articular process; in each vertebra, therefore, we have two isthmuses, one for each side. In this specific area the vertebral arch is relatively thin and in some subjects it can be interrupted due to various causes: the interruption of the isthmus is defined as spondylolysis.






Most authors believe that the predisposition to spondylolysis is to be considered congenital, in the sense that some people are born with a particularly fragile vertebral isthmus and that this, being the vertebral column subjected to continuous loading and movement, over time it stops, giving rise to the aforementioned pathology. It is easy to understand how this interruption almost exclusively affects the lumbar spine and how it mainly affects the last lumbar vertebra (L5) and less frequently the penultimate vertebra (L4). The appearance of spondylolysis is favored by the practice of all those activities that repeatedly stress the vertebral column in hyperextension, especially if this movement is combined with torsion of the trunk, or by the repeated lifting of large loads. For these reasons, spondylolysis is most frequently diagnosed among athletes and in particular among gymnasts, weightlifters, divers, skaters and obviously dancers (Trepman et al., 1990; Fehlandt and Micheli, 1993; Seitsalo et al., 1997; Eck and Riley, 2004).


In most cases the condition of spondylolysis is practically asymptomatic: often the diagnosis can be defined as random in the sense that the interruption of the vertebral isthmus is highlighted during radiographic examinations performed, for example, to assess the presence of a scoliosis or other postural defects of adolescence. The above makes us understand how, in the scientific literature, there are a series of studies carried out on dancers and young athletes, which demonstrate how this condition is particularly highlighted among adolescents, especially if they carry out their specific activities for more than 15 hours a week ( Micheli and Wood, 1995; Hall, 1999). In reality, however, before we can say that spondylolisthesis is clearly more frequent among young dancers than adolescents who do not practice this activity, we should reflect on the fact that athletes are normally subjected, even in the absence of specific symptoms, to a series of diagnostic tests that the rest of the population does not normally enjoy and that, perhaps, this significant increase in the frequency of the pathology examined in the dancers could also be linked to the greater accuracy and frequency of screening investigations. On the other hand it is true that, in the presence of a predisposing congenital condition (thin isthmus), the practice of dancing, repeatedly urging the column in extension, can favor the appearance of a spondylolysis.


A clinical condition closely related to spondylolysis is represented by spondylolisthesis: in the case of interruption of both vertebral isthmuses, in fact, the body of the vertebra is free to move forward due to the force of gravity and tends to slide with respect to the underlying vertebra













The extent of the sliding of the body of the vertebra with respect to that of the underlying vertebra allows to classify the spondylolisthesis in 4 different degrees: from the first, in which the displacement is slight, up to the fourth in which it witnesses a massive vertebral sliding. As previously mentioned, it is usually the fifth lumbar vertebra that slides on the sacral first (see fig. 3) or it can be the fourth lumbar vertebra that moves with respect to the body of the fifth.


The symptomatology of spondylolisthesis can be different from individual to individual: there are professional dancers, with also significant slips, who during the years in which they practice the activity have never suffered from back pain and who instead begin to experience problems when they stop dancing while, on the other hand, there are dancers with a slight vertebral slide that begin to complain prematurely for a low back pain, especially when their column is set in hyperextension while they are resting on a single limb (eg arabesque). By relating these different clinical pictures to the most current principles of biomechanics of the spine, we could say that the extent of pain in spondylolisthesis is linked to the subject's ability to stabilize the lumbar tract in the execution of the extension movement: for this reason, therefore, in dancers with a strong and controlled "center", pain occurs only at the end of their career when the decrease in hours of daily activity leads to a relative "weakening" of the deep musculature; in weaker or less controlled dancers, on the other hand, the pain begins early, due to the instability of the lumbar tract during trunk and limb movements.


Every time a dancer, especially if young, complains of discomfort or pain in the lumbar region that has persisted for some time and becomes more evident at the end of the lesson or the tests, a specialist examination is indicated: the doctor will then decide whether to deepen the diagnostic tests with radiographs (in standard and oblique projections) or with a Nuclear Magnetic Resonance. This latter method has completely replaced other methods of investigation, such as bone scintigraphy, which in the past were used for the diagnosis of spondylolysis. In the case in which the presence of a spondylolisthesis is highlighted, the so-called "dynamic radiographs", or radiographs of the lumbar spine performed in lateral projection with the subject in maximum flexion and in maximum extension of the rachis, will allow the specialist to evaluate the stability of the vertebra that is slipping and will allow to set a more correct therapeutic plan.


Every time a dancer, especially if young, complains of discomfort or pain in the lumbar region that has persisted for some time and becomes more evident at the end of the lesson or the tests, a specialist examination is indicated: the doctor will then decide whether to deepen the diagnostic tests with radiographs (in standard and oblique projections) or with a Nuclear Magnetic Resonance. This latter method has completely replaced other methods of investigation, such as bone scintigraphy, which in the past were used for the diagnosis of spondylolysis. In the case in which the presence of a spondylolisthesis is highlighted, the so-called "dynamic radiographs", or radiographs of the lumbar spine performed in lateral projection with the subject in maximum flexion and in maximum extension of the rachis, will allow the specialist to evaluate the stability of the vertebra that is slipping and will allow setting a more correct therapeutic plan.ation of the "slipped" vertebra (Clippinger, 2007).

The symptomatology of spondylolisthesis can be different from individual to individual: there are professional dancers, with also significant slips, who during the years in which they practice the activity have never suffered from back pain and who instead begin to experience problems when they stop dancing while, on the other hand, there are dancers with a slight vertebral slide that begins to complain prematurely about a low back pain, especially when their column is set in hyperextension while they are resting on a single limb (eg arabesque). By relating these different clinical pictures to the most current principles of biomechanics of the spine, we could say that the extent of pain in spondylolisthesis is linked to the subject's ability to stabilize the lumbar tract in the execution of the extension movement: for this reason, therefore, in dancers with a strong and controlled "centre", pain occurs only at the end of their career when the decrease in hours of daily activity leads to a relative "weakening" of the deep musculature; in weaker or less controlled dancers, on the other hand, the pain begins early, due to the instability of the lumbar tract during trunk and limb movements.ts..ning investigations. On the other hand, it is true that, in the presence of a predisposing congenital condition (thin isthmus), the practice of dancing, repeatedly urging the column in extension, can favour the appearance of a spondylolysis.

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