Lumbar spondylolysis: a life long dynamic condition? A cross sectional survey of 4.151 adults.

Lumbar spondylolysis (LS) has been the subject of several studies focusing on adolescent athletes. Few, if any, studies have examined LS in the general population. Lysis of the pars interarticularis of the vertebra may be associated with slipping (olisthesis), or it may be stable. In the present survey of lumbar radiographs and general epidemiological data recorded from the Copenhagen Osteoarthritis Study cohort of 4.151 subjects (age range, 22-93 years), we identified the distribution and individual risk factors for LS-development. Men were significantly more at risk of L5 spondylolysis (P = 0.002). There were no sex-specific significant differences regarding LS-incidence at the L4 level. We found no significant differences of risk of LS between nulliparous or multiparous women (L4 P = 0.54/L5 P = 0.35). Furthermore, we found no significant relationship between age at menopause and LS-development. Increased lumbar lordosis was associated to L4/L5 spondylolysis in men (L4 P < 0.001/L5 P = 0.008). In women increased lumbar lordosis had a significant association with L5 spondylolysis (P < 0.001). Increased pelvic inclination was associated with L5 spondylolysis in both men and women (P < 0.001). There were no sex-specific differences regarding the occurrence of simultaneous slips/non-slips. In men, no individual risk factors for L4 slips with concomitant LS were found. In women slipped LS of L4 were significantly associated to aging (P < 0.001) and with decreased pelvic inclination (P = 0.001). In men slipped LS of L5 was significantly associated to increased BMI (P = 0.002), but not to aging (P = 0.10). In women, slips of L5 LS were significantly correlated to aging (P = 0.005), to BMI recorded at the time of radiographic examination (P = 0.006), and BMI measured 17 years before radiographic index examination (P = 0.004). The present study contrasts with commonly held views regarding lumbar spondylolysis. The prevalence of LS increases throughout life and is apparently not a condition restricted to adolescence. Although the cross-sectional nature of the present study prevents an exact estimate of the age at onset; future, sequential studies of the cohort may provide us with some important answers on this topic. Apart from aging-obesity, lordotic angle and pelvic inclination were found to be individual risk factors for LS.