Glenoid retroversion is an important factor for humeral head centration and the biomechanics of posterior shoulder stability
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Glenoid retroversion is a known independent risk factor for recurrent posterior instability. The purpose was to investigate progressive angles of glenoid retroversion and their influence on humeral head centration and posterior translation with intact, detached, and repaired posterior labrum in a cadaveric human shoulder model.
A total of 10 fresh-frozen human cadaveric shoulders were investigated for this study. After CT- canning, the glenoids were aligned parallel to the floor, with the capsule intact, and the humerus was fixed in 60° of abduction and neutral rotation. Version of the glenoid was created after wedge resection from posterior and fixed with an external fixator throughout the testing. Specimens underwent three conditions: intact, detached, and repaired posterior labrum, while version of the glenoid was set from + 5° anteversion to − 25° retroversion by 5° increments. Within the biomechanical setup, the glenohumeral joint was axially loaded (22 N) to center the joint. At 0° of glenoid version and intact labrum, the initial position was used as baseline and served as point zero of centerization. After cyclic preloading, posterior translation force (20 N) was then applied by a material testing machine, while start and endpoints of the scapula placed on an X–Y table were measured.
The decentralization of the humeral head at glenoid version angles of 5°, 10°, 15°, and 20° of retroversion and 5° of anteversion was significantly different (P < 0.001). Every increment of 5° of retroversion led to an additional decentralization of the humeral head overall by (average ± SD) 2.0 mm ± 0.3 in the intact and 2.0 mm ± 0.7 in the detached labrum condition. The repaired showed significantly lower posterior translation compared to the intact condition at 10° (P = 0.012) and 15° (P < 0.01) of retroversion. In addition, CT measured parameters (depth, diameter, and native version) of the glenoid showed no correlation with angle of dislocation of each specimen.
Bony alignment in terms of glenoid retroversion angle plays an important role in joint centration and posterior translation, especially in retroversion angles greater than 10°. Isolated posterior labrum repair has a significant effect on posterior translation in glenoid retroversion angles of 5° and 10°. Bony correction of glenoid version may be considered to address posterior shoulder instability with retroversion > 15°.
KeywordsGlenoid dysplasia Retroversion Posterior shoulder instability Shoulder biomechanics Humeral head centration
The authors would like to thank Burkhart Schulz for graphic illustrations.
The University of Connecticut Health Center/UConn Musculoskeletal Institute has received direct funding and material support from Arthrex Inc. (Naples. Fl). The company had no influence on study design, data collection, or interpretation of the results or the final manuscript. No-one of the all mentioned authors has received personal financial support related to this study.
Compliance with ethical standards
Conflict of interest
Authors Imhoff FB, Camenzind RS, Obopilwe E, Cote MP, Mehl J, and Dyrna F declare that they have no conflict of interest. Author Beitzel K is a consultant for Arthrex. Author Imhoff AB is a consultant for Arthrosurface, Arthrex, and mediBayreuth. Author Mazzocca AD is a consultant for Orthofix and Arthrex and receives research grants from Arthrex. Author Arciero RA received an educational and institutional grant from Arthrex and is a consultant for Biorez.
Ethical approval was obtained via Human Research Determination Form to the institutional review board (IRB) of the University of Connecticut and it was documented that no IRB approval was required (de-identified specimen do not constitute human subjects research).
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