Thoracic kyphosis in light of lumbosacral alignment in thoracic adolescent idiopathic scoliosis: recognition of thoracic hypokyphosis and therapeutic implications.

In thoracic AIS, a decreased TK corresponded to an increased SS or a decreased max-LL. The sagittal alignment of thoracic AIS patients could be classified into three types based on SS and max-LL. One of these three types includes the unique sagittal profile of very small TK.