Background The reported prevalence of spondylolysis (SL) in the adult population is 6–7%. Data concerning adolescent-onset spondylolisthesis (SLS) and the impact of certain activities on it is scarce. We examined the risk of clinical progression of SL and SLS as a function of primary severity and occupational strain among military recruits. Methods Based on the Israel defense Force (IDF) central human resources database, we identified 1521 18-year-old males inducted to the IDF with SL/SLS between the late nineteen nineties and early two-thousands. We followed changes in the SL/SLS status during the 3 years of obligatory military service. Disease severity was classified as Cat2: radiological findings of SL without clinical findings; Cat3: painful SL or asymptomatic grade 1 SLS; Cat4: grade 1 SLS with pain; Cat5: Grade 2 SLS. The soldiers were subdivided into the following occupational categories: administrative, combat, maintenance, and driving. The purpose was to compare the progression rates in different medical categories and job assignments. Results There were 162 recruits in Cat2, 961 in Cat3, and 398 recruits in Cat4. The overall progression rate to Cat5 (grade 2 SLS) was 1.02%. Significant progression rates were seen amongst administrative soldiers with a relatively higher risk of progression from Cat4 (painful-grade-1 SLS: 2.2%) vs. Cat3 (asymptomatic SLS: 0.5%, relative risk = 4.7, p < 0.02). Other occupational categories did not exhibit significant progression rates. Conclusion Progression of SL/SLS was highest in Cat4, i.e. for recruits already diagnosed with painful SLS (i.e. with a more severe baseline disorder). Progression did not correlate with military occupation. We recommend further follow-up studies that include, aside from progression rates, incidence rates of newly diagnosed grade 2 SL during military service.

Objectives: It is unclear whether adolescence obesity is associated with limited linear growth. We assessed this association in a nationwide cohort of adolescents. Methods: We conducted a nationwide, population-based, cohort study of 2,785,227 Israeli adolescents (60% males) who were examined before military service in 1967 through 2015; Height and weight were measured along with assessment of medical status at age 17.4±0.4 years. The secular trend of height was plotted for US-CDC age- and sex-adjusted BMI percentiles groups. We accounted for health status at enrolment and computed the expected height based on parental data that was available for 512,978 examinees. Results: Mean height has increased by 3.1 cm among males, but remained unchanged among females over five decades. Among males, gain in height was mostly attained during the first 25 years and has stabled since. Obese males were taller than their normal-weight and underweight counterparts. Underweight girls had a prominent increase in mean height during the first 2 decades exceeding by over 2 cm the mean height of their obese counterparts. There was a gradual decrease in the difference between measured and expected height in males and females regardless of BMI status, with the exception of underweight females who achieved consistently higher stature than expected (≥3 cm). Conclusions: During five decades excessive BMI was not a limiting factor in growth potential compared to normal BMI in both sexes. Underweight females with unimpaired health are the sole group that has yet realized its growth potential even when accounting parental height.