Diaphragm thickness and stiffness in patients with hyperkyphosis due to osteoporotic vertebral fracture: an ultrasonographic and elastographic study

Abstract

Purpose: The objective of this study was to evaluate the thickness and stiffness of the diaphragm, using ultrasound (US) and strain elastography (SE) in patients with hyperkyphosis due to osteoporotic vertebral fracture.

Material and methods: This prospective and case-control study was conducted between October 2019 and December 2019. Diaphragm thickness, SE, and strain ratio values of patients with hyperkyphosis due to osteoporotic vertebral fracture were compared with those of the control group.

Results: There were 42 patients (14 males, 28 females) with a mean age of 81.10 ± 6.3 years in the kyphosis group and 36 subjects (11 males, 25 females) with a mean age of 81.00 ± 5.5 years in the control group. End-inspirium thickness, change level, and thickening ratio of the diaphragm were significantly higher in the control group (p < 0.001 for all). Strain ratio values were significantly higher in the kyphosis group, and the rate of hardest colour code was significantly higher in the control group. The diaphragm thickness at end-inspirium and thickening ratio values correlated positively with the forced expiratory volume in the first second (FEV₁, %) and forced vital capacity (FVC, %) values. The strain ratio values correlated inversely with the FEV₁ (%) and FVC (%) values. The diaphragm thickness at end-inspirium and thickening ratio values correlated inversely with the Cobb values and number of vertebra fractures. A positive correlation was determined between the strain ratio values and the Cobb values and number of vertebra fractures.

Conclusions: Ultrasonography is a promising imaging tool to evaluate and quantify the diaphragm function and stiffness in relevant patients.

Keywords: diaphragm; musculoskeletal ultrasound; osteoporosis; sonoelastography.

Figure 1

B-mode ultrasound image showing the diaphragm. The diaphragm (D) is visualised between the peritoneum and pleura (thin arrows). The upper and lower white lines correspond to the pleura and peritoneum, respectively

Figure 2

Diaphragm strain ratio measurement using the strain elastography. While measuring the spectral reflectance, the circular region of interest (ROI) was selected at 1-3 mm intervals, and the first ROI was placed in the intercostal muscle as a reference point (strain 1) near the diaphragm (strain 2)

Figure 3

The diaphragm thickening ratio values correlated positively with the forced expiratory volume in the first second (FEV1, %) (r = 0.924, p < 0.001) and forced vital capacity (FVC, %) (r = 0.795, p < 0.001) values. The strain ratio values correlated inversely with the FEV1 (%) (r = –0.929, p < 0.001) and FVC (%) values (r = –0.791, p < 0.001)