Department for Shoulder and Elbow Surgery, Center for Musculoskeletal Surgery, Campus Virchow, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Am J Sports Med. 2019 Mar;47(3):688-694. doi: 10.1177/0363546518819102. Epub 2019 Jan 14.
Bone loss at the anterior glenoid rim is a main reason for failure of soft-tissue based surgical stabilization procedures in patients with anterior shoulder instability.
To evaluate the capability of conventional glenoid bone loss measurement techniques to provide an adequate estimation of the actual biomechanical effect of glenoid defects.
Descriptive laboratory study.
Thirty consecutive patients with unilateral anterior shoulder instability and varying degrees of glenoid defect were included. Patient-specific computer tomography-based 3-dimensional shoulder models of the affected and unaffected sides were created. The bony shoulder stability ratio (SR) was determined in various potential dislocation directions with finite element analysis. Values obtained from conventional glenoid defect size measurement techniques (Pico and Sugaya) were correlated with the finite element analysis results. Additionally, a mathematical model was developed to theoretically analyze the correlation between glenoid defect size measurements and the SR.
The authors found substantial interindividual differences of the SR of the unaffected shoulders in all directions of measurement. Bone loss at the anterior glenoid rim significantly reduced the SR in the 2-o'clock ( P = .011), 3-o'clock ( P < .001), and 4-o'clock ( P < .001) directions referring to a right shoulder. The correlation between the defect size measurements and the SR for the 2-o'clock (rho = -0.522 and -0.580), 3-o'clock (rho = -0.597 and -0.580), and 4-o'clock (rho = -0.527 and -0.522) directions was statistically significant. However, it showed only moderate strength and was nonlinear as well as dependent on the inherent shape of the concavity. As shown by the mathematical model, bone loss has the most considerable effect at the edge of the glenoid rim, and an increasingly concave-shaped glenoid leads to an increase in loss of SR provoked by the same extent of bone loss.
Current glenoid bone loss measurements are unable to provide an adequate estimation on the actual biomechanical effect of glenoid defects because (1) the relation between the glenoid defect size and its biomechanical effect is nonlinear and (2) patients with shoulder instability have constitutional biomechanically relevant glenoid concavity shape differences.
These findings challenge the current concept of setting a general threshold for critical glenoid bone loss, which requires bony reconstruction surgery.
在前肩胛盂缘的骨丢失是导致软组织基础手术稳定程序在前肩不稳定患者中失败的主要原因。
评估常规肩胛盂骨丢失测量技术提供对肩胛盂缺损实际生物力学影响的充分估计的能力。
描述性实验室研究。
纳入 30 例单侧前肩不稳定且肩胛盂缺损程度不同的连续患者。基于患者特定的计算机断层扫描的 3 维肩部模型分别创建受累侧和未受累侧。通过有限元分析确定各种潜在脱位方向的骨性肩部稳定性比（SR）。从常规肩胛盂缺损尺寸测量技术（Pico 和 Sugaya）获得的值与有限元分析结果相关。此外，还开发了一个数学模型，从理论上分析了肩胛盂缺损尺寸测量与 SR 之间的相关性。
作者发现所有测量方向的未受累侧 SR 的个体间差异很大。前肩胛盂缘的骨丢失显著降低了 2 点钟（P =.011）、3 点钟（P <.001）和 4 点钟（P <.001）方向的 SR。2 点钟（rho = -0.522 和 -0.580）、3 点钟（rho = -0.597 和 -0.580）和 4 点钟（rho = -0.527 和 -0.522）方向的缺损尺寸测量与 SR 的相关性具有统计学意义。然而，它仅显示出中等强度，并且是非线性的，并且依赖于凹面的固有形状。正如数学模型所示，骨丢失对肩胛盂缘的边缘影响最大，并且具有相同程度的骨丢失会导致 SR 丧失的增加。
目前的肩胛盂骨丢失测量方法无法对肩胛盂缺损的实际生物力学效果进行充分估计，原因是（1）肩胛盂缺损大小与其生物力学效果之间的关系是非线性的，（2）肩不稳定患者具有与生物力学相关的固有肩胛盂凹形形状差异。
这些发现挑战了目前对临界肩胛盂骨丢失设置一般阈值的概念，这需要进行骨重建手术。
