A novel classification on degenerative thoracolumbar kyphosis based on sagittal spino-pelvic alignment: should the thoracolumbar segments be intervened?

PURPOSE: There are few researches on characterizing the sagittal alignment of degenerative thoracolumbar kyphosis (DTLK). In addition, the debate on the reasonable surgical strategies, for various patterns of DTLK, still continues. So, the study was to identify the features of DTLK, propose a novel classification of DTLK, and develop surgical strategies for this population.

METHODS

An overall 245 patients diagnosed with DTLK combined with lumbar stenosis performed surgeries (acquired satisfied) were selected from January 2016 to December 2022. The spino-pelvic measurements thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sagittal vertical axis (SVA) as well as the severe osteoporosis were recorded. To identify groups with similar spino-pelvic sagittal alignment parameters and clinical features, a 2-step cluster analysis was performed.

RESULTS

Close relationships were found among the parameters. Four types of DTLK based on TLK and balance were classified with Type I: mild kyphosis and balance, Type II: mild kyphosis and imbalance, Type III: severe kyphosis and balance, Type IV: severe kyphosis and imbalance. The probability for imbalance with severe osteoporosis was 8.4 times higher than no osteoporosis (RR = 8.410). The probability for imbalance with PI-LL mismatch was 10 times higher than PI-LL matching (RR = 0.099 in Type II and RR = 0.103 in Type IV). For patients with DTLK, the TK was correlated with LL, PI-LL or PI in Type I to III group but not in Type IV group. Targeted treatment strategies for different types of patients was then addressed.

CONCLUSION

We proposed a novel classifcation with four types of DTLK based on TLK and balance, followed by targeted treatment strategies for various types. Osteoporosis and lumbo-pelvic mismatch were risk factors for DTLK imbalance.