The influencing factor of degenerative lumbar scoliosis severity in patients with rheumatoid arthritis: a case-control study

English Keywords:Rheumatoid arthritis  Degenerative lumbar scoliosis  Total knee arthroplasty  Knee society score  Influencing factor

English Abstract:

  【Abstract】 Objectives: To perform retrospective analysis on patients with rheumatoid arthritis(RA) diagnosed as degenerative lumbar scoliosis(DLS), and to clarify the influencing factors of the degree of scoliosis. Methods: The single-center study enrolled 61 RA underwent lumbar spine surgery from January 2013 to April 2018 according to the inclusion criteria. They were divided into DLS group(27 cases) and NDLS group with non-spine deformity(34 cases). The extracted information includes demographic information such as gender, age, and body mass index(BMI), RA-related parameters such as disease duration, Steinbrocker classification, disease-modifying anti-rheumatic drugs(DMARDs), surgery-related information and information on DLS such as the incidence of DLS, Cobb angle, intercrestal line, rotation angle and coronal displacement of apical vertebrae, osteoporosis, total knee arthroplasty(TKA) history and knee society score(KSS). Steinbrocker classification was used to evaluate the activity of RA, Cobb angle was to reflect the degree of lumbar scoliosis, and KSS was induced to evaluate knee function. Results: The mean RA duration was 16.8±12.7 years. There were respectively 14 cases, 34 cases and 13 cases in grade Ⅰ, Ⅱ and Ⅲ of Steinbrocker classification. Females were the majorities of the two groups. There was a statistical difference in gender between DLS group(male∶female=1∶26) and NDLS group(male∶female=8∶26)(P=0.031), but none in age and BMI(both P>0.05). There was no statistical difference in Steinbrocker classification, proportion of taking DMARDs and osteoporosis(P>0.05). A total of 11 patients underwent TKA and there was no significance in TKA distribution between the two groups(P=0.153). The mean Cobb angle in DLS group was 18.4°±9.0°(10.4°-39.2°). The Cobb angle(11.8°±1.5°) in patients underwent TKA was less than those without TKA(20.6°±9.5°) (P=0.001). Rotation angle and coronal displacement of apical vertebrae were respectively 8.4°±6.8° and 47.3±7.8mm, and almost all the intercrestal line was within L4/5 level. Cobb angle was in correlation to rotation angle and coronal displacement of apical vertebrae and TKA(P<0.05), but not to other parameters. Linear regression analysis for scoliosis degree in DLS group showed that TKA was the independent influencing factor(P=0.029), while there was unclear correlation with TKA duration and Cobb angle. KSS(88.7±5.3) in patients with TKA was higher than ones without TKA(80.4±10.0)(P=0.034). There was a negative correlation between KSS and Cobb angle(r=-0.717, P<0.001). The fitting formula between the two variables was Cobb angle=70.38-0.64×KSS. Conclusions: DLS are more susceptible in middle-aged and elderly women in RA patients. Patients previously underwent TKA suffer from less severe degree of DLS and there is a close correlation between KSS and Cobb angle.