Analysis of humeral head displacements from sequences of biplanar X-rays: repeatability study and preliminary results in healthy subjects

This work presents an accurate method to measure gleno-humeral translations in a controlled pseudo-kinematic environment. Low-dose biplanar X-rays were acquired from nine healthy subjects at three elevations of the arm in the scapular plane. On each set of images, shoulder bony landmarks were manually located in 3D using a dedicated software. Intra-observer and inter-observer repeatability of landmark identification, as well as humeral head center (GH) translations, were studied. Repeatability for the identification of GH in the global coordinate system (CS) was good with 95% confidence intervals (CIs) ranging from 0.57 to 2.25 mm. Scapular landmark CIs ranged from 0.80 to 12 mm. Gleno-humeral translations of small amplitude ( < 6 mm) were detected in seven out of nine subjects. The results obtained here confirm that calibrated low-dose stereo-radiography is a promising tool for the functional analysis of the shoulder.