What is it ?
These are two very specific terms. Spondylolysis refers to a “rupture” (lysis) of a bone bridge in the posterior arch of a lumbar vertebra. Most often, this lysis appears in teenagers practicing an intense and regular sports activity. Sports at risk are: football, basketball, rowing, artistic gymnastics, etc. Lysis is a kind of fatigue fracture caused by repeated movements, in the context of growth and a particular anatomy of the spine. Very often, teenagers are asymptomatic and the pain is triggered rather in adulthood when the disc begins to degenerate (normal aging). However, pain can occur during adolescence, forcing the child to temporarily interrupt sports.
Spondylolisthesis refers to a “sliding” (listhesis), in general progressive and slow, of a lumbar vertebra (spondylos) in relation to the one below. This shift can be appear in the context of isthmic lysis (see above) and is called in this case isthmic spondylolisthesis, but most commonly, it occurs in adults whose discs and facet joints are worn out. It is then called “degenerative spondylolisthesis”, whose peculiarity is that it also causes a narrowing of the lumbar canal, and potentially a neurogenic claudication (see lumbar spinal stenosis).