Introduction
Lumbar spondylolysis during growth is a fatigue fracture caused by repeated extension and rotational stress on the pars interarticularis because of sports activities. It is commonly found in middle school students and reported even in children aged 6 years. Elementary students often have bilateral occurrences, and many cases have already developed into pseudarthrosis upon initial diagnosis. There is a higher incidence of spina bifida occulta and lumbar spondylolisthesis, resulting in a lower bone union rate. While there are many reports on orthotic therapy for lumbar spondylolysis in high school students, there are few studies comparing bone union rates among different braces for elementary students. This study aims to compare the bone union rates of different braces used for elementary students with lumbar spondylolysis.
Methods
Between April 2012 and January 2019, elementary students diagnosed with lumbar spondylolysis based on magnetic resonance imaging (MRI) and computed tomography (CT) examinations who could be followed up were included. Diagnosis and treatment were based on initial X-ray examination, followed by MRI screening. Lumbar spondylolysis was classified into three stages (early, progressive, terminal) based on sagittal CT images and MRI findings. Three types of braces were used during this period: soft braces from 2012 to 2015, semi-rigid braces from 2015 to 2016, and rigid braces from 2016 to 2019. Braces were worn except during sleep and bath. Bone union in lumbar spondylolysis was defined by the disappearance of the fracture line or improvement on CT. The treatment period was until the bone union was achieved or determined as non-union. The bone union rate was evaluated for three different types of braces.
Results
32 elementary students (24 males; mean age 10.4 ± 1.4 years) were included. Out of 32 cases, 19 cases (59%) had bilateral lumbar spondylolysis, while 13 cases (41%) had unilateral lumbar spondylolysis. All participants were involved in sports activities. Bone union rates varied with brace types. Using a soft brace, semi-rigid brace, and rigid brace, union rates were achieved at 25% (2 out of 8 sites), 56% (12 out of 18 sites), and 76% (19 out of 25 sites), respectively. Regarding the union rates by stage, early stages showed rates of 50%, 82%, and 87%, while progressive stages showed rates of 0%, 33%, and 71%, respectively. Statistical analysis revealed a significant difference between the soft and rigid brace groups (p=0.015). No significant difference was observed between the soft and semi-rigid groups (p=0.216) or semi-rigid and rigid groups (p=0.158).
Discussion
In this study, the bone union rate with the rigid brace was significantly higher. Extension and rotational stress on the pars interarticularis are significant in the onset of lumbar spondylolysis, and the rigid brace, which restricts both, is superior in fixation strength. Elementary students with lumbar spondylolysis have factors that reduce bone union, requiring more careful management. For the orthotic treatment of lumbar spondylolysis in elementary students, the rigid brace is considered the best. However, for early stages cases, it might be worth considering the use of a semi-rigid brace.