Cervical sagittal plane decompensation after surgery for adolescent idiopathic scoliosis: an effect imparted by postoperative thoracic hypokyphosis

Abstract

The sagittal profile of the thoracic spine is related to that of the cervical spine. The surgical treatment of Lenke Type 1 and 2 curves by using all pedicle screw constructs has a significant hypokyphotic effect on thoracic sagittal plane alignment (19 [86%] of 22 patients). If postoperative thoracic kyphosis is excessively decreased (mean 25.6°, p < 0.05), the cervical spine may decompensate into significant kyphosis.

Investigation of Cervical Intervertebral Discs before and after Surgery for Adolescent Idiopathic Scoliosis

“…First, more postoperative changes in sagittal alignment were noted for the cervical spine than for the lumbar spine, suggesting that intervertebral disc intensity changes are a mechanical issue caused by corrective fusion surgery and could be easily influenced by sagittal alignment. In fact, Hwang et al [8] reported a correlation between postoperative thoracic kyphosis in AIS patients and cervical alignment and that thoracic hypokyphosis was a risk factor for cervical kyphosis. In addition, several reports have indicated that the three-dimensional correction of thoracic scoliosis in AIS patients had a significant impact on cervical alignment [8][9][10][11][12]21,22].…”

“…In fact, Hwang et al [8] reported a correlation between postoperative thoracic kyphosis in AIS patients and cervical alignment and that thoracic hypokyphosis was a risk factor for cervical kyphosis. In addition, several reports have indicated that the three-dimensional correction of thoracic scoliosis in AIS patients had a significant impact on cervical alignment [8][9][10][11][12]21,22]. Second, because intervertebral discs of the cervical spine are smaller and narrower than those of the lumbar spine, it may have been difficult to discern signal intensity changes on MRI in a precise manner.…”

Parameters for the Evaluation of Cervical Sagittal Balance in Idiopathic Scoliosis

“…It should be noted, however, that although information about the relationship between thoracic kyphosis and lumbar lordosis has already been published in the literature, very little has been published about the reaction of the cervical spine to correction of deformity in idiopathic scoliosis. 2 Hilibrand et al 3 were the first to confirm the radiographic relationship between cervical and thoracic alignment in the sagittal plane. They noticed an inverse relationship between thoracic kyphosis and cervical lordosis in idiopathic scoliosis, in other words, the less the thoracic kyphosis the greater the loss of cervical lordosis.…”

“…When not corrected, the inversion of the cervical lordosis can cause early degenerative changes, increasing the incidence of cervicalgia. 2,4 Until very recently, the radiographic parameters of the sagittal balance of the cervical spine were typically inferred from a plumb line dropped from the seventh cervical vertebra and were not accurate in measuring the alignment of the cervical spine. 2 There are no standard values for the evaluation parameters of cervical sagittal balance in patients with idiopathic scoliosis defined in the literature.…”

“…2,4 Until very recently, the radiographic parameters of the sagittal balance of the cervical spine were typically inferred from a plumb line dropped from the seventh cervical vertebra and were not accurate in measuring the alignment of the cervical spine. 2 There are no standard values for the evaluation parameters of cervical sagittal balance in patients with idiopathic scoliosis defined in the literature. This study seeks to describe the cervical sagittal parameters in patients with adolescent idiopathic scoliosis.…”