Deformity, particularly positive sagittal malalignment, may go undetected unless one maintains a high index of suspicion and obtains long radiographic cassette. It is recommended that spine surgeons recognize the prevalence and importance of such deformity when contemplating operative intervention ¹⁾.

Vendatam et al. ²⁾ demonstrated that the mean sagittal vertical axis (SVA) shifts forward in the ageing population from −5.6 cm in adolescents to −3.2 cm in the middle aged and elderly population. A strong correlation exists between a positive shift in the SVA and a loss of lumbar lordosis and the onset of symptoms in patients, such as back pain and fatigue. Moreover, Glassman et al. ^{3) 4)} demonstrated that a positive sagittal imbalance was the most reliable radiographic predictor and indicator of clinical health status. It was shown in 352 patients that a mildly positive sagittal imbalance is detrimental with a linear fashion increase in symptoms with progressive sagittal imbalance. It is of note that disability was worse amongst those with a degree of kyphosis in their lumbar spine in comparison to the normal and lordotic lumbar spines. The causes of sagittal spine imbalance are multifactorial and these range from iatrogenic causes to genetic and metabolic causes.