Correlations between the inflection point and spinal sagittal alignment in asymptomatic adults.

PURPOSE

The purposes of this study were to analyse the correlations between the inflection point (IP) and spinal sagittal parameters and to establish the corresponding linear regressions in asymptomatic adults.

METHODS

A total of 205 asymptomatic subjects older than 18 years were recruited between April 2017 and September 2019. A full-spine, standing X-ray was collected for each subject. The following parameters were documented: the IP, the apices of thoracic kyphosis (TKA) and lumbar lordosis (LLA), the distance between the plumb line of the thoracic apex (TAPL) or lumbar apex (LAPL) and gravity plumb line, thoracic kyphosis (TK), lumbar lordosis (LL) and the upper arc and the lower arc of lumbar lordosis (LLUA and LLLA, respectively). The correlations between the IP and the above parameters and between the thoracic and lumbar parameters were analysed. The level of significance was P < 0.05.

RESULTS

The IP was statistically correlated with age (r = 0.327), the TKA (r = 0.639), the TAPL (r = 0.338), TK (r = 0.391), the LLA (r = 0.545), the LAPL (r = - 0.383), the LLUA (r = 0.371) and the LLLA (r = - 0.145) but was not linked with LL (r = 0.118). In addition, there were relationships between the TKA and LLA (r = 0.397), the TAPL and LAPL (r = - 0.357), TK and LL (r = 0.529), TK and the LLUA (r = 0.742) and TK and the LLLA (r = 0.148).

CONCLUSION

The IP was significantly related to spinal sagittal alignment in asymptomatic adults. Moreover, predictive formulae for sagittal parameters as a function of the IP were developed, which are helpful for surgeons in comprehending the regulatory mechanisms of spinal sagittal alignment and designing an ideal therapeutic plan. These slides can be retrieved under Electronic Supplementary Material.