Analysis of healthy glenohumeral arthrokinematics using four-dimensional computed tomography throughout internal rotation and forward elevation

Abstract

BackgroundThe glenohumeral joint is the most mobile joint in the human body and can translate in addition to rotating in its socket. Currently, it is not well established in literature how much the healthy humeral head translates, and how that changes overtime as people age. The objective of this study is to quantify glenohumeral joint proximity and translation in healthy patients and determine if there are any age, position, or direction related differences. MethodsThirty-one participants were recruited for this study and split into two cohorts: young (≤ 37 years old) and old (≥45 years old). Four-dimensional computed tomography scans were taken as these participants completed internal rotation to the back (IR) and forward elevation (FE). 3D bone models of the humerus and scapula were created using 3D Slicer. An inter-bone distance algorithm, and an Iterative Closest Point algorithm were used to determine glenohumeral joint proximity and translation, respectively. ResultsThis study found that older participants displayed significantly closer joint proximity (63% of glenoid surface was within 4mm of humeral head) during the middle of IR, compared to younger participants (52% of glenoid surface within 4mm of humeral head). Additionally, younger participants had significantly more translation in the Superior/Inferior direction (16% of glenoid height) compared to the Anterior/Posterior direction (10% of glenoid width) throughout IR. ConclusionThis study demonstrates the significance of translational movements within the glenohumeral joint throughout IR and FE, which will aid implant manufacturers in designing implants that will allow for more normalized glenohumeral translations.