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Prognostic Factors for Curve Progression in De-novo Degenerative Lumbar Scoliosis: A Systematic Review on Observational Studies

Introduction De-novo degenerative lumbar scoliosis (DNDLS) causes an increasing burden on society in aging populations, in particular reducing the overall quality of life due to severe back and leg pain. DNDLS has been reported to undergo unpredictable curve progression.1 To date, little is known about progression in DNDLS and it is unclear what factors play an important role in the process. Indications whether a degenerative scoliotic spine will undergo curve progression forms an ever-increasing challenge for health care providers to determine the optimal timing for therapeutic interventions. Existing reports on this continuously expanding societal problem are inconsistent. Therefore, the aim of this study was to perform a systemic review of the literature to identify prognostic factors for DNDLS curve progression. Material and Methods systematic searches were performed in the bibliographic databases PubMed and EMBASE prior to June 2015. The following inclusion criteria were applied: (1) de novo degenerative lumbar scoliosis, (2) adult scoliosis, (3) curve progression, (4) study population of N ≥ 10, and (5) studies published in the English language. Exclusion criteria were: (1) animal studies, (2) biomechanical studies, (3) prior juvenile, adolescent, associated congenital, developmental, or neuromuscular spinal abnormalities, and (4) history of spinal surgery. Studies that met our inclusion criteria were assessed for methodological quality by two authors (XX and XX) based on: study population, follow-up time, exposure, outcome, and statistical analysis.2 Data was extracted and presented according to a best evidence synthesis which has been adopted and modified from previous studies on prognostic factors in knee and hip arthritis.3,4 Results The literature search generated a total of 2696 references: 1323 in PubMed and 1373 in EMBASE. After removing duplicates and articles that did not meet inclusion criteria, 12 studies were included. Because a large heterogeneity was encountered in measurement methods, statistical analyses, sample sizes, variations in definition of DNDLS and curve progression, pooling was not possible. In total 33 determinants were obtained and grouped into two categories: patient and radiographic characteristics. Strong evidence indicates that intervertebral disc degeneration, lateral vertebral translation ≥6mm, and an intercrest line through L5 are associated with DNDLS curve progression. Further, moderate evidence suggests that apical vertebral rotation grade II or III is associated with curve progression. For the majority of determinants, limited, conflicting, or inconclusive evidence was found. Conclusion Strong evidence was found for several radiographic prognostic factors for DNDLS curve progression. A large variety in definitions of DNDLS and curve progression remains, which made pooling impossible. Additionally, because the sample sizes in the included studies were often small, these results may not be applicable to the individual patient. Large patient registries have shown to provide relevant information about the outcome after surgery for specific patient categories. Similarly, untreated patients with DNDLS should be included in similar registries or long-term prospective trials to be able to identify prognostic factors and to help understand the pathophysiology of curve progression in DNDLS. This is crucial to establish optimal follow-up strategies and timing for therapeutic interventions for this ever-increasing group of patients. References Xu L, Sun X, Huang S, et al. Degenerative lumbar scoliosis in Chinese Han population: prevalence and relationship to age, gender, bone mineral density, and body mass index. Eur Spine J 2013;22(6):1326–1331 Hayden JA, Côté P, Bombardier C. Evaluation of the quality of prognosis studies in systematic reviews. Ann Intern Med 2006;144(6):427–437 Bastick AN, Runhaar J, Belo JN, Bierma-Zeinstra SMA. Prognostic factors for progression of clinical osteoarthritis of the knee: a systematic review of observational studies. Arthritis Res Ther 2015;17:152 Lievense AM, Bierma-Zeinstra SMA, Verhagen AP, Verhaar JAN, Koes BW. Prognostic factors of progress of hip osteoarthritis: a systematic review. Arthritis Rheum 2002;47(5):556–562