|Dynamic Chiropractic – December 3, 1993, Vol. 11, Issue 25|
By Deborah Pate, DC, DACBROn occasion a spondylolysis will be present and the question will be, "Was this lesion caused by a recent event or has it been present for years?" Generally the radiographic findings of a spondylolysis are diagnostic. The defect in the pars interarticularis is best viewed on oblique projections, appearing as a break through the neck of the "Scotty dog." The etiology of this entity has long been debated. The present consensus is that this lesion is an acquired traumatic lesion originating sometime between infancy and early adult life, as a type of stress fracture. Most experts support the theory that the spondylolysis results from repeated trauma to the posterior arch. The pars interarticularis is the most vulnerable point when repeated stress is placed upon the posterior arch. It is possible, that a single traumatic incident could result in a spondylolysis. It has also been found that hereditary predisposition also plays a role in patient's with spondylolysis. Due to the multifaceted nature of spondylolysis, the lumbar spondylolysis and spondylolisthesis have been classified into five types:
Type I: dysplastic, with associated congenital abnormality of the upper sacrum and the arch of the lumbar vertebra.
Type II: isthmic, with a defect in the pars interarticularis that may be:
a) a fatigue fracture
b) an elongated but intact pars
c) an acute fracture
Type III: degenerative, due to long-standing intersegmental in stability (pseudospondylolisthesis)
Type IV: traumatic, due to a fracture in areas of the posterior elements other than the pars interarticularis
Type V: pathologic, due to generalized or localized bone disease
Osteoscintigraphy or a bone scan is the modality of choice when questioning the age of a spondylolysis. If the defect is an active stress fracture or a definite fracture the pars will demonstrate an increase in uptake of the radioisotope. The presence of a positive bone scan confirms the active nature of an existing defect or the presence of a developing stress fracture. This is a very important part of patient management, especially in the professional or highly motivated athlete. The increased uptake of the bone scan indicated there should be a reduction in the patient's physical activity. If there is a question of a developing or slight stress fracture, a special type of bone scan should be performed as it is more sensitive than the typical bone scan. It is called SPECT bone scintigraphy, or single-photon emission computed tomographic osteoscintigraphy. The major difference between SPECT and a regular bone scan is that a slice through the pars can be performed at smaller intervals, therefore allowing us to demonstrate the pars to best advantage. This ability will allow us to demonstrate even very subtle increases in uptake, which occurs with small developing stress fractures. If a subtle stress fracture is noted, the patient can modify and stop aggressive training to avoid a complete stress fracture through the pars. If given time, a recent stress fracture will heal and no spondylolysis develops.
Deborah Pate, DC, DACBR
San Diego, CA
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