Jun Mizutani1,2, Kushagra Verma3, Kenji Endo4, Ken Ishii5, Kuniyoshi Abumi6, Mitsuru Yagi7, Naobumi Hosogane8, Jeffrey Yang9, Bobby Tay3, Vedat Deviren3, Christopher Ames1. 1. Department of Neurological Surgery, University of California San Francisco, San Francisco, California. 2. Department of Rehabilitation Medicine and Department of Orthopaedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. 3. Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, California. 4. Department of Orthopedic Surgery, Tokyo Medical University, Tokyo, Japan. 5. Department of Orthopaedic Surgery, Keio University School of Medicine and International University of Health and Welfare (IUHW), Tokyo, Japan. 6. Sapporo Orthopaedic Hospital, Sapporo, Japan. 7. Department of Orthopaedic Surgery, National Hospital Organization Murayama Medical Center, Tokyo, Japan. 8. Department of Orthopaedic Surgery National Defence Medical College, Saitama, Japan. 9. University of California San Francisco Medical School, San Francisco, California.
Abstract
BACKGROUND: Previous studies have evaluated cervical kyphosis (C-kypho) using cervical curvature or chin-brow vertical angle, but the relationship between C-kypho and global spinal alignment is currently unknown. OBJECTIVE: To elucidate global spinal alignment and compensatory mechanisms in primary symptomatic C-kypho using full-spine radiography. METHODS: In this retrospective multicenter study, symptomatic primary C-kypho patients (Cerv group; n = 103) and adult thoracolumbar deformity patients (TL group; n = 119) were compared. We subanalyzed Cerv subgroups according to sagittal vertical axis (SVA) values of C7 (SVAC7 positive or negative [C7P or C7N]). Various Cobb angles (°) and SVAs (mm) were evaluated. RESULTS: SVAC7 values were -20.2 and 63.6 mm in the Cerv group and TL group, respectively (P < .0001). Various statistically significant compensatory curvatures were observed in the Cerv group, namely larger lumbar lordosis (LL) and thoracic kyphosis. The C7N group had significantly lower SVACOG (center of gravity of the head) and SVAC7 (32.9 and -49.5 mm) values than the C7P group (115.9 and 45.1 mm). Sagittal curvatures were also different in T4-12, T10-L2, LL4-S, and LL. The value of pelvic incidence (PI)-LL was different (C7N vs C7P; -2.2° vs 9.9°; P < .0003). Compensatory sagittal curvatures were associated with potential for shifting of SVAC7 posteriorly to adjust head position. PI-LL affected these compensatory mechanisms. CONCLUSION: Compensation in symptomatic primary C-kypho was via posterior shifting of SVAC7, small T1 slope, and large LL. However, even in C-kypho patients, lumbar degeneration might affect global spinal alignment. Thus, global spinal alignment with cervical kyphosis is characterized as head balanced or trunk balanced.
BACKGROUND: Previous studies have evaluated cervical kyphosis (C-kypho) using cervical curvature or chin-brow vertical angle, but the relationship between C-kypho and global spinal alignment is currently unknown. OBJECTIVE: To elucidate global spinal alignment and compensatory mechanisms in primary symptomatic C-kypho using full-spine radiography. METHODS: In this retrospective multicenter study, symptomatic primary C-kypho patients (Cerv group; n = 103) and adult thoracolumbar deformitypatients (TL group; n = 119) were compared. We subanalyzed Cerv subgroups according to sagittal vertical axis (SVA) values of C7 (SVAC7 positive or negative [C7P or C7N]). Various Cobb angles (°) and SVAs (mm) were evaluated. RESULTS: SVAC7 values were -20.2 and 63.6 mm in the Cerv group and TL group, respectively (P < .0001). Various statistically significant compensatory curvatures were observed in the Cerv group, namely larger lumbar lordosis (LL) and thoracic kyphosis. The C7N group had significantly lower SVACOG (center of gravity of the head) and SVAC7 (32.9 and -49.5 mm) values than the C7P group (115.9 and 45.1 mm). Sagittal curvatures were also different in T4-12, T10-L2, LL4-S, and LL. The value of pelvic incidence (PI)-LL was different (C7N vs C7P; -2.2° vs 9.9°; P < .0003). Compensatory sagittal curvatures were associated with potential for shifting of SVAC7 posteriorly to adjust head position. PI-LL affected these compensatory mechanisms. CONCLUSION: Compensation in symptomatic primary C-kypho was via posterior shifting of SVAC7, small T1 slope, and large LL. However, even in C-kypho patients, lumbar degeneration might affect global spinal alignment. Thus, global spinal alignment with cervical kyphosis is characterized as head balanced or trunk balanced.
Authors: Cole Bortz; Peter G Passias; Katherine Elizabeth Pierce; Haddy Alas; Avery Brown; Sara Naessig; Waleed Ahmad; Renaud Lafage; Christopher P Ames; Bassel G Diebo; Breton G Line; Eric O Klineberg; Douglas C Burton; Robert K Eastlack; Han Jo Kim; Daniel M Sciubba; Alex Soroceanu; Shay Bess; Christopher I Shaffrey; Frank J Schwab; Justin S Smith; Virginie Lafage Journal: J Craniovertebr Junction Spine Date: 2020-06-05