The influence of the costovertebral joint involvement on pulmonary function in ankylosing spondylitis combined with thoracolumbar kyphosis

English Keywords:Ankylosing spondylitis  Thoracolumbar kyphosis  Pulmonary function tests  Costovertebral joint involvement

English Abstract:

  【Abstract】 Objectives:　To investigate the pulmonary dysfunction patterns in ankylosing spondylitis(AS) patients with thoracolumbar kyphosis and to evaluate the association between pulmonary function and the severity of the costovertebral(CV) joints. Methods: A total of 45 patients underwent spinal osteotomy(41 males and 4 females) with a mean age of 34.6 years(range, 22-60 years) between April 2004 and December 2011 was included in this study. The average duration was 13.5 years(range, 3-37 years) and the average Cobb angle of thoracolumbar kyphosis was 83.5°(range, 55°-120°). Preoperative pulmonary function tests(PFTs) were performed in all patients. The severity of the CV joints was evaluated by CT scan and 5 different degrees(grade 0, 1, 2, 3, 4) were determined. According to the grades of the CV joints involvement, patients suffered form both pulmonary dysfunction and CV joints involvment were divided into two groups: group A(grade 1 or 2) and group B(grade 3 or 4). The parameters of PFTs were compared between two groups. The correlations between the severity of CV joint involvement and age, disease duration and parameters of PFTs were analyzed. Results: 7 patients had normal pulmonary function, while pulmonary dysfunction was observed in 38 patients(84.4%). Among these 38 patients, mild, moderate and severe dysfunction was observed in 13, 22 and 3 patients respectively. The number of patients with restrictive, obstructive and mixed ventilatory dysfunction was 23, 2 and 13 respectively. The CV joint involvement was noted in 41 patients(91.1%), and radiographic changes of grade 1, 2, 3 and 4 in CV joints were observed in 7, 13, 18 and 3 patients respectively. Patients in group B had significantly lower percentages of predicted vital capacity(VC%), forced vital capacity(FVC%) and 30 times forced expiratory volume in one second(FEV1*30%) than those in group A(P<0.05). There was positive correlation between the severity of the CV joint involvement and Cobb angle(r=0.43, P=0.024). Neither age nor disease duration showed a significant correlation with the severity of the CV joint involvement(r=0.08, 0.44, P>0.05). Nevertheless, the severity of radiographic changes of CV joints was negatively correlated with VC%, FVC% and FEV1*30%)(r=-0.49, -0.35, -0.39, P＜0.05). Conclusions: Pulmonary dysfunction is common in AS patients with thoracolumbar kyphosis. Majority of patients present moderate ventilatory impairment. Restrictive ventilatory impairment is the most prevalent pattern of pulmonary dysfunction. The involvement of the CV joints is an influencing factor of pulmonary dysfunction in AS patients with thoracolumbar kyphosis.