Associations between in-vivo glenohumeral joint motion and morphology

Abstract

Joint morphology has a significant influence on joint motion and may contribute to the development of rotator cuff pathology, but the relationships between glenohumeral joint (GHJ) morphology and in-vivo GHJ motion are not well understood. The objectives of this study were to assess measures of joint morphology and their relationship with in-vivo joint motion in two populations: shoulders with intact rotator cuffs (n=48) and shoulders with rotator cuff pathology (n=36, including 5 symptomatic tears, 9 asymptomatic tears and 22 repaired tears). GHJ morphology was measured from CT-based three-dimensional models of the humerus and scapula. In-vivo GHJ motion was measured during shoulder abduction using biplane x-ray imaging. Associations between GHJ morphology and motion were assessed with univariate and best subsets regression. The only morphological difference identified between the populations was the critical shoulder angle (intact: 34.5±4.7°, pathologic: 36.9±5.0°, p=0.03), which is consistent with previous research. In intact shoulders, the superior/inferior (S/I) position of the humerus on the glenoid during shoulder abduction was significantly associated with the glenoid's S/I radius of curvature (p<0.01), conformity index (p<0.01), and stability angle (p<0.01). Furthermore, the S/I position of the humerus on the glenoid was negatively associated with the critical shoulder angle (p=0.04), which contradicts previous research. No significant associations between GHJ morphology and GHJ motion were detected in shoulders with rotator cuff tears. It is unknown if rotator cuff pathology compromises the relationships between GHJ morphology and motion, or if the absence of this relationship is a pre-existing condition that increases the likelihood of pathology.

Effects of glenoid inclination and acromion index on humeral head translation and glenoid articular cartilage strain

“…7 In vivo joint motion and various morphologic parameters were also tested for correlation, but only CSA proved to be significantly higher in subjects with pathologic rotator cuffs than in controls. 31 Two biomechanical cadaveric experiments confirmed the specific effect of AI and GI on glenohumeral joint stability, as well as their relation with CSA. 15,28 Despite the radiologic observations and recent in vitro simulation studies, the biomechanical rationale between GI, AI, and CSA on the one hand and glenohumeral osteoarthritis and rotator cuff tendon tears on the other hand is not completely understood yet.…”

“…GI and AI were associated with rotator cuff tendon tears and glenohumeral osteoarthritis. 17,27,29,31,39,41 In this study, we used a biomechanical shoulder model to evaluate the relative effects of these 2 different anatomic parameters on upward translation of the humeral head and glenoid articular cartilage strain. Assuming the hypothesis that humeral head translation and articular cartilage strain are mechanically related to rotator cuff tendon tears and glenohumeral osteoarthritis, respectively, the model predictions confirmed all previously reported biomechanical and clinical observations.…”

Thinking outside the glenohumeral box: Hierarchical shape variation of the periarticular anatomy of the scapula using statistical shape modeling

“…The glenoid shape is important in normal shoulder kinematics and dynamics. Peltz et al 11 found that glenoid morphology has a substantial influence on glenohumeral joint (GHJ) motion, with a more superiorly oriented humeral head during abduction in flatter and less conforming glenoids. To recreate normal kinematics and dynamics, the current axiom in surgery skews toward reconstructing the anatomy to the premorbid state.…”

“…9,10 To the contrary, an in vivo study quantifying glenohumeral joint motion found a more inferior orientation of the humeral head during abduction in normal shoulders with a higher CSA. 11 Although it has been subject to debate and thorough biomechanical evidence is still missing, morphologic differences of the coracoacromial (CA) arch have been associated with overuse pathologies such as shoulder impingement syndrome. Anatomic factors that might contribute to this syndrome include shape variation of the acromion, variation in acromial slope, prominent bony spurs on the inferior aspect of the CA-joint or CA-ligament [12][13][14][15][16] and morphologic differences of the coracoid process.…”

Rotator cuff pathology: state of the art

“…When thoracohumeral abduction exceeds 90°, a higher CSA leads to inferior translation of the humeral head in normal shoulders as shown in an in-vivo model 44. This counterintuitive effect may be explained by a downward directed lever arm through the surrounding soft tissue that is pressed into the acromial arch during deltoid activity in abduction above 90°.…”