Purpose: Spondylolysis is known to be a part of a disease process which describes a defect in the pars interarticularis of vertebra. This study was conducted to investigate vertebral body bone mineral density (BMD) in patients with lumbar spondylolysis by using quantitative computed tomography (QCT) and to compare with controls.
Methods: Forty symptomatic patients with lumbar spondylolysis aged 18 to 52 years and 40 matched controls of the same sex and the same approximate age (±2 years) were included in the study. Measurements of BMD were performed by QCT analysis for each vertebral body between thoracic 12 to lumbar 5 (T12-L5) and the mean BMD of each case was calculated.
Results: Of the 40 patients 22 (55%) demonstrated L5 spondylolysis, 14 (35%) demonstrated L4 spondylolysis, three (7.5%) demonstrated L3 spondylolysis, and one (2.5%) demonstrated L2 spondylolysis. Twenty nine of these patients (73%) also demonstrated spondylolisthesis. Significant difference of age was determined between the patients with and without spondylolisthesis (42±6.9 vs. 37.2 ±5.4, P =0.024). Mean BMD value of patient group was significantly lower, compared with the controls (105±24 mg/cm³ vs. 118.7±25.6 mg/cm³, P = 0.015). Subgroup analysis of 19 patients and 19 controls under the age of 40 revealed that the mean BMD value of the patients was also significantly lower, compared with the controls (108.7±23.5 mg/cm³ vs. 130±25.8 mg/cm³, P =0.009).
Conclusions: This study demonstrated that the mean vertebral body BMD value of the patients with spondylolysis was significantly lower than controls.