Effect of Anterior Glenoid Chondrolabral Defects on Anterior Glenohumeral Stability: A Biomechanical Study

Abstract

Background: It is well known that glenoid osseous defects >13.5% of the glenoid width critically destabilize the shoulder, as do labral tears. Chondrolabral defects often occur with anterior dislocation of the shoulder. It is unclear whether glenoid chondrolabral defects contribute to shoulder stability and, if so, at what size they become critical. Purpose/Hypothesis: The purpose of this study was to determine the effect of incremental chondrolabral defect sizes on anterior shoulder stability in the setting of labral deficiency. The hypothesis was that chondrolabral defects ≥13.5% of the glenoid width will decrease anterior shoulder stability. Study Design: Controlled laboratory study. Methods: This controlled laboratory study tested 12 fresh-frozen shoulders. Specimens were attached to a custom testing device in abduction and neutral rotation with 50-N compression applied to the glenoid. The humeral head was translated 10 mm anterior, anteroinferior, and anterosuperior with the conditions of intact cartilage and labrum and anterior full-thickness chondrolabral defects of 3-, 6-, and 9-mm width. Translation force was measured continuously. Peak translation force divided by 50-N compressive force defined the stability ratio. Data were analyzed using analysis of variance. Results: The anterior stability ratio decreased between the intact state (36% ± 7%) and all defects ≥3 mm (≤32% ± 8%; P ≤ .023). The anteroinferior stability ratio decreased between the intact state (52% ± 7%) and all defects ≥3 mm (≤47% ± 7%; P ≤ .006). The anterosuperior stability ratio decreased between the intact state (36% ± 4%) and all defects ≥6 mm (≤33% ± 4%; P ≤ .006). A 3-mm defect equated to 10% of the glenoid width. There were moderate to strong negative correlations between chondrolabral defect size and stability ratio in the anterior, anteroinferior, and anterosuperior directions ( r = –0.79, –0.63, and –0.58, respectively; P ≤ .001). There were moderate to strong negative correlations between the percentage of glenoid chondrolabral defect size to the glenoid width and the stability percentage in all directions ( r = –0.81, –0.63, and –0.61; P ≤ .001). Conclusion: An anterior glenoid chondrolabral defect ≥3 mm (>10% of the glenoid width) significantly decreased anterior and anteroinferior stability. Chondrolabral defect size negatively correlated with stability. Clinical Relevance: To fully restore glenohumeral stability, in addition to labral repair, it may be necessary to reconstruct chondrolabral defects as small as 3 mm (10% of the glenoid width).

The “Bankart knee”: high‐grade impression fractures of the posterolateral tibial plateau lead to increased translational and anterolateral rotational instability of the ACL‐deficient knee

“…As with the shoulder joint, where the intact osseous support of the bony glenoid helps maintain the biomechanical function of the labrum, a posterolateral tibia plateau impression fracture seems to have the same effect as a bony Bankart lesion [21, 32, 35], resulting in instability of the joint by destabilizing the PHLM; this analogy served as the origin for the derived term “Bankart knee”.…”

“…The intact tibial plateau provides osseous support for the PHLM and is therefore essential for maintaining its stability and biomechanical function [24, 27, 34]. A similar effect was demonstrated in the shoulder joint, where, in cases of a bony Bankart lesion characterized by an impression of the glenoid fossa, the consequential loss of osseous support for the labrum causes its biomechanical function to change [21, 30]. By analogy between the biomechanical influences of a bony Bankart lesion and those of the knee fractures in this study, this type of knee injury is referred to as “the Bankart knee”.…”