Surgical Impact on Global Sagittal Alignment and Health-Related Quality of Life Following Cervical Kyphosis Correction Surgery: Systematic Review

Abstract

When spinal imbalance occurs, the human body reacts through various compensatory mechanisms to maintain the head over the pelvis and to retain a horizontal gaze. These compensations occur through mobile spine segments as well as pelvic tilt and lower extremities. The purpose of this review was to understand the surgical impact on global sagittal alignment and health-related quality of life (HRQoL) following cervical kyphosis correction surgery. The cervical kyphosis correction surgery induces reciprocal changes in craniocervical and thoracolumbar alignment. Successful cervical deformity correction needs to focus not only on restoring proper cervical lordosis, but also on achieving global balance of the cervical spine with other parts of the spine. The goal of the surgery is to achieve occiputtrunk (OT) concordance (the center of gravity-C7 sagittal vertical axis < 30 mm) and cervical sagittal balance. Once OT-concordance is achieved, subsequent thoracolumbar alignment changes occur as needed to harmonize global spinal alignment. Reciprocal changes after surgery exhibit different patterns depending on whether patients have compensation ability in their thoracolumbar spine or not. C2-7 sagittal vertical axis and sagittal morphotype of the cervical kyphosis are correlated with HRQoL. Changes in cervical lordosis minus T1 slope correlate to HRQoL improvements.

Keywords: Cervical reconstruction; Global sagittal alignment; Health-related quality of life; Reciprocal change.

Fig. 1.

Revised cervical spinal deformity classification system [7], which consists of a deformity descriptor and 5 modifiers. CBVA, chin-brow to vertical angle; TS, T1 slope; CL, cervical lordosis; mJOA, modified Japanese Orthopedic Association score; SRS, Scoliosis Research Society; PI, pelvic incidence; LL, lumbar lordosis; D, double; L, lordosis; T, thoracic; N, none.

Fig. 2.

Compensation mechanisms in patients with symptomatic primary cervical kyphosis. PL, plumb line; CK, cervical kyphosis; LL, lumbar lordosis; PI, pelvic incidence; TK, thoracic kyphosis.

Fig. 3.

A representative case of a patient having compensated cervical kyphosis. Pre- (A) and postoperative whole-body EOS lateral image (B) showing that center of gravity (COG) plumb line (PL, blue line) was located on the femoral head, but the C7 PL (red line) was located markedly posteriorly. Cervical malalignment was corrected to achieve global sagittal balance (sagittal vertical axis [SVA]C2, SVA_COG–C7 and SVA_C2–7 & 40 mm) and OT concordance (distance between the COG PL and C7 PL & 30 mm). TK, thoracic kyphosis; LL, lumbar lordosis; PI, pelvic incidence; SRS, Scoliosis Research Society; SF-36 PCS, Short-Form-36 physical component; NDI, Neck Disability Index; ODI, Oswestry Disability Index; VAS, visual analogue scale; SFA, sacrofemoral angle; KA, knee angle; AA, ankle angle.

Fig. 4.

Whole-body images of a patient having decompensated cervical kyphosis. T1 slope and throracic kyphosis decreased while spinopelvic- and lower extremity parameters did not change following cervical deformity correction surgery.