Dominic Bachmann (Cologne), Lukas Berringer (Saarbrücken), Dr. Karen aus der Fünten (Saarbrücken), Prof. Dr. Guenther Schneider (Saarbrücken), Dr. Oliver Steimer (Saarbrücken), Dr. Diana Hell (Saarbrücken), Prof. Dr. Wolfgang Potthast (Cologne)
Abstract-Text (inkl. Referenzen und Bildunterschriften)
In most biomechanical studies, the hip joint (HJ) is described as a 3 DoF joint with no translation (trans), resembling a perfect ball-socket joint. However, studies report HJ trans (HJT) up to 4.1 mm1. Despite this, a comprehensive analysis of HJT and its impact on premature joint contact is lacking. Therefore, this study employs a multivariate regression (MR) approach to define HJT based on HJ orientation. Two male subjects (age=28, height = 1.90m) underwent MRI to capture seven hip orientations on each side. Mesh-to-point registration was used to align reference segmentation with MRIs. The femoral head center (FHC) was determined using a best spherical fit. To define HJT, a local coordinate system (LCS) was established: MP=[RP,PAC] (RP= rotation matrix pelvis, PAC= center of acetabulum) and the FHC was transformed into this LCS: P'= RP (PFC-PAC) (PFC= FHC). LCS for the femur was defined and rotated into the pelvis to define Euler angles. Three MR analyses treated rotations as ind. variables and trans as dep. variables. MR analysis revealed significant relationships between Flex/Ext and Ant/Post trans (adj. R2=0.583, p<0.001, coef.=0.03) and Add/Abd and Sup/Inf trans (adj. R2=0.62, p<0.001, coef.=0.047) (see Fig. 1). The results suggest coupling mechanisms between Flex/Ext and Ant/Post trans as well as Abd/Add and Sup/Inf trans. Clinical relevance lies in their impact on premature contact during flexion or abduction in individuals with femoroacetabular impingement (FAI). Implementing these insights into modulations is crucial for clinical considerations, given the influence of trans on premature joint contact in specific movement scenarios with FAI.
Figure 1 Regression results: a) Flex/Ext and Ant/Post trans (adj. R2=0.58, p<0.001, coef.=0.03) b) Add/Abd and Inf/Sup trans (adj. R2=0.62, p<0.001, coef.=0.047)
1Kapron, A. L. et al. (2015). In-vivo hip arthrokinematics during supine clinical exams: Application to the study of FAI. Journal of Biomechanics