The natural history of spondylolysis and spondylolisthesis.
This is a classic Spine Study looking at the natural history of spondylolysis and spondylolisthesis in a population of 500 first grade students in a small community bordering New York and Pennsylvania. The initial enrollment period was 1954 to 1957. The inclusion criteria was that the first grader had parental permission and attended one of several local elementary schools. Radiographs (supine AP, Lateral, and Oblique) were obtained and reviewed by the study authors as well as a radiologist. Any questionable results subjects had tomograms or follow-up x-rays the following year to confirm the presence or absence of spondylolysis or spondylolisthesis.
Each of the 500 subjects were asked to have follow-up x-rays at ages 10-12, 15-16 and age 18. The study was terminated in 1979. There was a significant drop off in the number of subjects who had x-rays at age 15-16 and age 18. No subject who had a defect was lost to follow-up.
The 4.4 % of the original 500 sets of x-rays demonstrated unilateral or bilateral pars defects at age 6 years old.
Of the first graders who did not have the defect initially, two subjects developed a defect during the course of the study. The paper does not indicate when the defect developed and since there was a significant fall off of testing after age 10-12, no conclusions on this information can be drawn.
One ancillary study took the 23 children with defect (at first grade) and x-rayed all family members who was more than a year old and also did follow up x-rays like the original study subjects. 32% of the fathers did have a spondylolysis. The possibility of a genetic factor was discussed.
A second ancillary study reviewed x-rays of 500 normal neonates. No neonates had spondylolisthesis. Because of the nature of x-rays on neonates, it would be impossible to know if these neonates did have spondylolysis, without a slip.
A third ancillary study involved family members of 32 consecutive children delivered at community’s obstetrics unit in 1955 or 1956. Each of the study families had x-ray and the neonates had x-rays at ages 1-3. Three parents had a pars defect (5%). One sibling in the family with a parent that had a defect also had a defect (7%). None of the newborns had defects when x-rayed at ages 1-2.
The study concludes the incidence of a pars defect is 4.4 % at age 6 and 6% in adulthood. Spondylolithesis does not exist at birth. Slipping rarely progresses. Inheritance is a factor. A child with a defect can be permitted to enjoy a normal childhood and adolescence without restrictions.
Comments: For 1984, this was a great population study on the natural history of pars defects in a defined population from the 1950’s. The objective was simple and the findings measurable on x-rays. Utilizing modern day criteria to evaluate studies, it could not rate high on our scale. The study demonstrated the incidence for pars defects in a population of 1st graders, and followed the subjects to adulthood. The constructive criticism is about the steep drop off in follow up after age 12 (by age 15-16, only 37%). While 2 subjects developed a pars defect during the examination period, the significance of this number is unknown without knowing what happened to the remainder of the cohort. Not surprisingly, those 1st graders who had pars defects continued to participate in the follow-up x-rays. Their parents had enough concerns that they continued to get x-rays, and none of the pars defect subjects were lost to follow up. The bias is evident.
Still, this study attempted to define the natural history of pars defects in a defined population and draws some conclusions that is accepted as fact, even today. Dr. Frederickson and colleagues continue to be recognized for this landmark population study on spondylolysis and spondylolisthesis.