Vertebral body bone mineral density in patients with lumbar spondylolysis: a quantitative CT study.

PURPOSE Spondylolysis is known to be a part of a disease process, which describes a defect in the pars interarticularis of vertebra. We aimed to use quantitative computed tomography (QCT) to measure vertebral body bone mineral density (BMD) in patients with lumbar spondylolysis and compare it with readings in controls. METHODS Forty symptomatic patients with lumbar spondylolysis aged 18-52 years and 40 matched controls of same sex and approximate age (±2 years) were included in the study. Measurements of BMD were performed by QCT analysis for each vertebral body from T12 to L5 and mean BMD was calculated for each case. RESULTS Of 40 patients, 22 (55%) demonstrated L5 spondylolysis, 14 (35%) L4 spondylolysis, three (7.5%) L3 spondylolysis, and one (2.5%) L2 spondylolysis. Spondylolisthesis was found in 29 patients (73%). Patients with spondylolisthesis were significantly older than patients without spondylolisthesis (42±6.9 vs. 37.2±5.4, P = 0.024). Mean BMD value of the patient group was significantly lower than that of 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 significantly lower than that of the controls in the younger age group as well (108.7±23.5 mg/cm³ vs. 130±25.8 mg/cm³, P = 0.009). CONCLUSION This study demonstrated that patients with spondylolysis had significantly lower mean vertebral body BMD compared with controls.