'Skipped' level disc degeneration of the lumbar spine: prevalence and associated risk factors

Abstract

Clinical observations suggest that subjects occasionally exhibit a pattern involving non-consecutive ('skipped') levels of lumbar degenerative disc disease (SLDDD). This study aims to address this unpublished issue by examining its prevalence and associated clinical and radiological factors. As part of a large population-based genetic study in Southern Chinese (n=1,989), subjects exhibiting DDD more than two levels (n=838) were grouped into SLDDD (n=174) and non-SLDDD (n=664). SLDDD were classified into five types by the relative location of healthy disc(s) (HD) to DDD levels. Subject demographics and clinical profiles were collected by questionnaire. SLDDD was present in 8.7% and 20.8% of the overall and DDD population, respectively, and more prevalent in males by the relative location of healthy disc(s) (HD) to DDD levels. Subject demographics and clinical profiles were collected by questionnaire. SLDDD was present in 8.7% and 20.8% of the overall and DDD population, respectively, and more prevalent in males (OR: 1.6; 95% CI: 1.1-2.2; p=0.008). Type 1 (38%; one DDD level above and below HD) and Type 2 (32%; one level above and multi-levels of DDD below HD) were the most common types. SLDDD was significantly associated with the presence of Schmorl's node (p =0.0001), which also presented in non-DDD levels. Interestingly, disc bulge/extrusion, back injury history and pain profiles were significantly associated with non-SLDDD (p<0.05). Other demographics, MRI findings and clinical profiles did not significantly differ between groups (p>0.05). This study is the first to describe SLDDD. While its etiology remains unknown, altered spinal biomechanics associated with SLDDD might account for less pronounced clinical symptoms. The understanding of SLDDD may shed light on the cause of back pain.