The effect of glenosphere lateralization on joint mobility of reverse shoulder arthroplasty: a cadaveric biomechanical study

Objectives: The lateralization of the glenosphere reduces scapular notching or impingement. But the effect on joint mobility remains unclear. With the increased attention to reverse shoulder arthroplasty, this biomechanical study analyzes the effect ofglenosphere lateralization on range of motions in reverse shoulder arthroplasty.

Methods: In this biomechanical study reverse shoulder arthroplasty was performed in 5 cadaveric shoulders (DeltaXtend; Fa. Depuy/Synthes). The glenosphere lateralization was classified in 3 groups: I) + 0 mm, II) + 5 mm and III) +10 mm for each cadaveric shoulder. We measured the range of motion by using a motion capture system (Optotrak Certus) in the sagittal (y-axis) and the coronar plane (x-axis). Besides the range of motion of the M. deltoideus the rotator cuff (TMI; ISF and SCP) were measured. A custom biomechanical set up was used to test the samples with a constant valley load (+ 1; 2; 3; 4 kg) for each.

Results and Conclusion: The first 5 specimens have shown a higher range of motion in abduction (M. deltoideus, pars acromialis) and external rotation (ISF/TMI) by a maximal load in group II and III as in group I (p = .08). The internal rotation (SCP) is lower in the group III than in group II and I. The main abduction by a maximal load (4 kg) was 44,87 ° (group I), 59,18 ° (group II) and 63,88 ° (group III). The mean external rotation (ISF) was measured by a maximal load (4 kg) 33,02 ° (I), 56,83 ° (II) and 47,73 ° (III). But the results have not shown a significantly difference, so in order to ensure this, the number of specimens needed for the verification of the hypothesis had to be calculated with the aid of a power analysis. For the verification of the hypothesis 3 more specimens are needed.

Conclusion: In the first step of our study the lateralization of the glenosphere seems to be improving the range of motion, especially for the abduction and the external rotation. So the second step of our study will be with 3 more specimens to verify our hypothesis.

We will finish the second step and present the expected results at the congress.

Stichwörter: Reverse shoulder arthroplasty, lateralization, glenosphere, joint mobility, biomechanics

Publication History

Article published online:
15 October 2020