Effects of kyphotic apical vertebra position on the sagittal plane morphology and quality of life in patients with degenerative kyphosis

English Keywords:Degenerative kyphosis  Kyphotic apical vertebra  Health related quality of life  Sagittal alignment

English Abstract:

  【Abstract】 Objectives: To analyze the impact of the kyphotic apical vertebra(KAV) position on sagittal plane characteristics and quality of life in patients with degenerative kyphosis(DK). Methods: A retrospective analysis was conducted on the clinical and imaging data of 68 DK patients hospitalized and treated in the Department of Orthopedic Surgery, Nanjing Drum Tower Hospital from February 2010 to December 2022. There were 8 males and 60 females, aged 46-76 years old(60.6±6.5 years). The patients were divided into two groups based on the position of the KAV: Group 1(G1) included 38 patients with the KAV at or above L1, and Group 2(G2) included 30 patients with the KAV below L1. The thoracic kyphosis(TK), lumbar lordosis(LL), sagittal vertical axis(SVA), pelvic incidence(PI), pelvic tilt(PT), sacral slope(SS), T1-pelvic angle(TPA), and global kyphosis(GK) were measured on standing full-spine lateral X-rays before operation, and the value of PI-LL was calculated. Health related quality of life(HRQoL) was assessed using the Scoliosis Research Society-22(SRS-22) questionnaire, Oswestry disability index(ODI), visual analog scale(VAS) score, and SF-36 questionnaire. Independent samples t-tests were used to compare sagittal plane parameters and HRQoL scores between the two groups. Pearson correlation analysis was employed to examine the relationship between sagittal plane parameters and HRQoL scores. Results: There was no significant difference in the age and sex ratios between the two groups(P>0.05). The GK, LL, TK, SVA, PI, PT, SS, TPA, and PI-LL in G1 group were respectively 61.3°±20.0°, 26.9°±18.9°, 32.3°±19.0°, 53.5±48.1mm, 40.4°±13.4°, 24.8°±12.6°, 17.0°±11.7°, 23.0°±13.5°, and 21.6°±15.6°, which in G2 group were 38.8°±16.0°, 14.4°±13.7, 10.8±9.8°, 96.5±67.8mm, 44.8°±16.2°, 30.1°±10.8°, 14.7°±11.5°, 32.6°±14.5°, and 33.8°±18.3°. The GK, LL, and TK were significantly greater in G1 group than those in G2 group(P<0.05), and SVA, TPA, and PI-LL were less in G1 group than those in G2 group(P<0.05). The VAS score, ODI, SF-36 physical component score(PCS), SF-36 mental component score(MCS), SRS-22(function, pain, self-image, mental health, subtotal score) in G1 group were 4.2±1.6, (37.9±15.2)%, 45.8±11.3, 48.6±12.7, and (17.6±4.6, 18.6±4.3, 17.7±4.5, 17.8±4.9, 71.7±9.3), which were 5.8±1.7, (48.6±20.0)%, 38.2±12.9, 44.2±13.1, and (15.6±4.5, 16.0±3.6, 16.6±4.9, 17.1±4.3, 65.4±11.1) in G2 group. G1 group was lower in VAS score and ODI significantly(P<0.05) and higher in SRS-22 subtotal score, SRS-22 pain domain score, and SF-36 PCS significantly(P<0.05) than G2 group. Pearson correlation analysis showed that SVA was positively correlated with VAS and ODI in both groups(G1 group: r=0.437, P=0.006 and r=0.356, P=0.028; G2 group: r=0.405, P=0.027 and r=0.408, P=0.025), while negatively correlated with SF-36 PCS(G1 group: r=-0.365, P=0.024; G2 group: r=-0.410, P=0.024). TPA was positively correlated with VAS score in both groups(G1 group: r=0.343, P=0.035; G2 group: r=0.369, P=0.045). In G2 group, SVA negatively correlated with SRS-22 subtotal score(r=-0.391, P=0.033), and PI-LL was positively correlated with VAS score(r=0.390, P=0.033). Conclusions: The position of KAV affects the pelvic-spinal sagittal alignment obviously in DK patients, and the patients with KAV located below L1 level have significantly higher SVA, TPA, and PI-LL compared to the patients whose KAV located at or above L1 level, which is significantly associated with decreased quality of life.