Thoracic joint abnormalities and impaired thoracic motion in idiopathic pleuroparenchymal fibroelastosis: an exploratory study using inspiratory and expiratory CT

Idiopathic pleuroparenchymal fibroelastosis (IPPFE) is a rare interstitial lung disease characterized by restricted ventilation and upper-lobe fibroelastosis. Historically, ankylosing spondylitis has been implicated in upper-lobe fibrosis and ventilatory impairment due to chest wall restriction, and impaired thoracic motion has recently been appreciated in IPPFE. We hypothesized that thoracic joint abnormalities (costovertebral, manubriosternal, and sternocostal joints) contribute to the impaired thoracic motion in patients with IPPFE.

Seventeen patients with IPPFE and 15 non-PPFE interstitial lung disease were retrospectively investigated. Thoracic joint abnormalities were assessed as abnormal calcifications on inspiratory CT images. Thoracic motion was evaluated by the average moving distance of four anterior thoracic landmarks between inspiratory and expiratory CT images. Thoracic motion ratio (TMR) was defined as the ratio of the measured average moving distance to the cube root of the predicted vital capacity. The ratio of the lung volume change (LVCR) was calculated from inspiratory and expiratory CT images. Associations between TMR, LVCR, and pulmonary function test parameters (PFT) parameters were assessed.

Thoracic joint abnormalities were observed in 14 of 17 IPPFE patients, mainly at sternocostal joints. Impaired thoracic motion, defined by the thoracic motion ratio less than half of the normal value, was observed in 9 of 17 IPPFE patients, but in only 1 of 15 non-PPFE patients. All 9 IPPFE patients with impaired thoracic motion exhibited joint abnormalities. The correlation between TMR and LVCR was stronger in the IPPFE group than in the non-PPFE group.

Thoracic joint abnormalities associated with impaired motion are frequently observed in IPPFE patients. These abnormalities may restrict thoracic movement and lead to the development of IPPFE.