Correlation between pelvic incidence minus lumbar lordosis mismatch after surgery for degenerative scoliosis and clinical outcomes

SUN Xiang-yao; ZHANG Xi-nuo; HAI Yong

doi:10.3969/j.issn.2095-252X.2017.01.005

Abstract：Objective To explore the correlation between pelvic incidence minus lumbar lordosis ( PI-LL ) mismatch after the surgery for adult degenerative scoliosis ( ADS ) and correction of scoliosis, quality of life and failure of internal fixation. Methods The clinical data of 69 patients with ADS who underwent long posteriorinstrumentation and fusion from January 2010 to January 2014 were retrospectively reviewed. There were 21 males and 48 females, whose mean age was ( 63.7 ± 4.7 ) years old. They were followed up for an average period of ( 3.2 ± 0.7 ) years. The patients were divided into 3 groups:group A ( PI-LL≤10° ), group B ( 10°<PI-LL≤20° ) and group C ( PI-LL>20° ). The radiographic sagittal parameters were measured before and after the operation and at the latest follow-up. The patients’ quality of life was evaluated after the operation and at the latest follow-up according to the Japanese Orthopaedic Association ( JOA ) score, Oswestry disability index ( ODI ), visual analogue scale ( VAS ) and lumbar stiffness disability index ( LSDI ), and these parameters were statistically analyzed. Then, PI-LL could be worked out. Univariate linear regression equation was performed to investigate the relative inlfuence of postoperative PI-LL on radiographic parameters and clinical outcomes. Results In group A, the preoperative Cobb’s angle of scoliosis, preoperative PI-LL, preoperative ODI, preoperative JOA, preoperative VAS, Cobb’s angle of scoliosis at the latest follow-up, immediate postoperative PI-LL, ODI at the latest follow-up, JOA at the latest follow-up, VAS at the latest follow-up and LSDI at the latest follow-up were ( 19.4 ± 2.9 ) °, ( 35.8 ± 5.2 ) °, 63.5 ± 2.7, 5.4 ± 1.2, 7.1 ± 1.3, ( 4.4 ± 2.7 ) °, ( 5.1 ± 3.0 ) °, 26.7 ± 4.1, 2.7 ± 1.3, 3.0 ± 1.2 and 3.2 ± 1.0 respectively. In group B, the preoperative Cobb’s angle of scoliosis, preoperative PI-LL, preoperative ODI, preoperative JOA, preoperative VAS, Cobb’s angle of scoliosis at the latest follow-up, immediate postoperative PI-LL, ODI at the latest follow-up, JOA at the latest follow-up, VAS at the latest follow-up and LSDI at the latest follow-up were ( 20.1 ± 2.6 ) °, ( 36.6 ± 4.0 ) °, 62.9 ± 3.0, 5.6 ± 1.2, 6.8 ± 1.4, ( 3.7 ± 1.3 ) °, ( 17.6 ± 2.0 ) °, 17.5 ± 3.9, 3.2 ± 1.2, 3.1 ± 0.9 and 1.5 ± 1.2 respectively. In group C, the preoperative Cobb’s angle of scoliosis, preoperative PI-LL, preoperative ODI, preoperative JOA, preoperative VAS, Cobb’s angle of scoliosis at the latest follow-up, immediate postoperative PI-LL, ODI at the latest follow-up, JOA at the latest follow-up, VAS at the latest follow-up and LSDI at the latest follow-up were ( 21.3 ± 2.8 ) °, ( 35.3 ± 4.1 )°, 62.4 ± 2.8, 5.8 ± 1.3, 6.7 ± 1.3, ( 4.5 ± 0.8 ) °, ( 25.9 ± 2.9 ) °, 32.7 ± 5.2, 3.1 ± 1.6, 3.1 ± 0.8 and 0.8 ± 0.8 respectively. The postoperative Cobb’s angle of scoliosis, PI-LL, JOA, ODI and VAS were signiifcantly improved, compared with the preoperative data ( P<0.001 ). There were statistically signiifcant differences in immediate postoperative PI-LL among the 3 groups ( P<0.001 ). However, there were no statistically signiifcant differences in other radiographic parameters among the 3 groups. There were statistically signiifcant differences in ODI and LSDI at the latest follow-up among the 3 groups ( P<0.001 ). However, there were no statistically signiifcant differences in other life quality indexes. The internal ifxation failure rate was lower in group B than the other groups ( P=0.005 ). There were no statistically signiifcant differences in the reoperation rate ( P=0.620 ). Curve estimation showed that stroke equation iftted the relationship between postoperative PI-LL and Cobb’s angle ( R2=0.416, P<0.001 ). Cubic equation iftted the relationship between postoperative PI-LL and ODI ( R2=0.370, P<0.001 ) or LSDI at the latest follow-up ( R2=0.720, P<0.001 ). However, there was a low correlation between postoperative PI-LL and other indexes ( P<0.05 ). Conclusions The optimal PI-LL may be between 10° and 20° in ADS patients after long posterior instrumentation and fusion for better clinical outcomes and lower complication rates related to postoperative internal fixation. The overcorrection of LL will result in lower PI-LL, and then may lead to more serious postoperative lumbar stiffness.