Epidemiology and clinical implications of lumbar developmental spinal stenosis

Abstract

Lumbar developmental spinal stenosis (DSS) is described as pre-existing narrowed vertebral canals at multiple lumbar levels. It predisposes patients to a lower threshold of neurological compromise and contributes to a high reoperation rate. In this dissertation, a systematic review was conducted to identify the knowledge gap of DSS. The current radiological diagnostic studies are flawed by being inconsistent in the proposed diagnostic criteria, imaging modalities, and patient orientations, and neglecting the importance of multilevel stenosis. This dissertation also utilized a large-scale southern Chinese cohort to establish a diagnostic criterion for DSS which considered the significance of multilevel stenosis. It was superior to other studies with higher sensitivity and specificity for recognizing subjects at-risk. It also provided a guideline for surgeons to consider pre-emptive decompression which would lower the risk of reoperation. Subjects with axial anteroposterior canal diameter below the criteria in at least three levels are classified as multilevel DSS. A prevalence of 7.3% was also noted. In addition to abnormally small spinal canals, the presence of other spinal abnormalities is also important for evaluating the severity of spinal dysplasia and its clinical implications. The coexistence of osseous and soft tissue changes and DSS further restricts the canal size leading to an early onset of symptoms. However, the relationships between these radiological phenotypes are poorly understood. In this dissertation, logistic regression analyses were performed, and there was no association between subject body size and DSS, while all radiological phenotypes related to the canal were significantly shorter in DSS. The lamina angle was also associated with DSS in which a more obtuse angle contributes to a narrower canal. Besides, although DSS and degenerative changes of the spine can coexist in the same patient, there was no evidence for more degenerative changes in subjects with DSS. This proves that DSS is a result of bony maldevelopment which is confined to the vertebral canal. Determining the patterns of DSS within a family is also essential to provide the basis for future genetic studies. Several single nucleotide polymorphisms and genetic mutations have been associated with DSS. Although evidence has pointed DSS towards a genetic origin, its inheritance pattern is unknown. In this dissertation, families were recruited to identify the stenotic patterns across generations. DSS is likely to be an autosomal dominant disease, and the inheritance is also level specific. Understanding the clinical implications of DSS and different radiological phenotypes is also important to identify possible pain generators. Many studies have assessed similar relationships, but they are inaccurate as they only observed one radiological parameter without adjusting for the coexistence of other radiological and lifestyle factors. In this dissertation, subject demographics, lifestyle factors, and radiological phenotypes were integrated to determine their isolated risks of low back pain (LBP) and radiating leg pain. Subjects with spondylolisthesis had higher odds of acute and chronic LBP, while subjects with DSS had higher odds of acute and chronic radiating leg pain. These spinal abnormalities should be examined carefully in a clinical setting.