The differential effect of cervical kyphosis correction surgery on global sagittal alignment and health-related quality of life according to head- and trunk-balanced subtype

Seung-Jae Hyun MD, PhD, Ki-Jeong Kim MD, PhD, and Tae-Ahn Jahng MD, PhD
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  • Department of Neurosurgery, Spine Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea
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OBJECTIVE

No reports have investigated how cervical reconstructive surgery affects global sagittal alignment (GSA), including the lower extremities, and health-related quality of life (HRQOL). The study was aimed at elucidating the effects of cervical reconstruction on GSA and HRQOL.

METHODS

Twenty-three patients who underwent reconstructive surgery for cervical kyphosis were divided into a head-balanced group (n = 13) and a trunk-balanced group (n = 10) according to the values of the C7 plumb line, T1 slope (T1S), and pelvic incidence minus lumbar lordosis (PI-LL). Head-balanced patients are those with a negative C7 sagittal vertical axis (SVA), a larger LL than PI, and a low T1S. Trunk-balanced patients are those with a positive SVAC7, a normal PI-LL, and a normal to high T1S. Various sagittal Cobb angles, SVA, and lower-extremity alignment parameters were measured before and after surgery using whole-body stereoradiography.

RESULTS

Cervical malalignment was corrected to achieve cervical sagittal balance and occiput-trunk (OT) concordance (center of gravity [COG]–C7 SVA < 30 mm). Significant changes in the upper cervical spine and thoracolumbar spine were observed in the head-balanced group, but no significant change in lumbopelvic alignment was observed in the trunk-balanced group. Lower-extremity alignment did not change substantially in either group. HRQOL scores improved significantly after surgery in both groups. SVACOG–C7 and SVAC2–7 were negatively and positively correlated with the 36-Item Short-Form Health Survey physical component score and Neck Disability Index, respectively. The visual analog scale for back pain, Oswestry Disability Index, and PI-LL mismatch improved significantly in the head-balanced group after cervical reconstruction surgery.

CONCLUSIONS

Patients with cervical kyphosis exhibited compensatory changes in the upper cervical spine and thoracolumbar spine, instead of in the lower extremities. These compensatory mechanisms resolved reciprocally in a different fashion in the head- and trunk-balanced groups. HRQOL scores improved significantly with GSA restoration and OT concordance following cervical reconstruction.

ABBREVIATIONS AA = ankle angle; CL = C2–7 lordosis; COG = center of gravity of the head; DJK = distal junctional kyphosis; GSA = global sagittal alignment; HRQOL = health-related quality of life; KA = knee angle; LL = lumbar lordosis; NDI = Neck Disability Index; ODI = Oswestry Disability Index; OT = occiput-trunk; PI = pelvic incidence; PJK = proximal junctional kyphosis; PL = plumb line; PT = pelvic tilt; SF-36 PCS = physical component score of the 36-Item Short-Form Health Survey; SFA = sacrofemoral angle; SRS-22r = Scoliosis Research Society–22 questionnaire, revised version; SVA = sagittal vertical axis; T1S = T1 slope; TK = thoracic kyphosis; VAS = visual analog scale.

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Contributor Notes

Correspondence Seung-Jae Hyun: Spine Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Gyeonggi, Republic of Korea. hyunsj@snu.ac.kr.

INCLUDE WHEN CITING Published online April 2, 2021; DOI: 10.3171/2020.9.SPINE201309.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

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