Effects of biceps tension on the torn superior glenoid labrum

Abstract

The purpose of this study was to evaluate the role of the tension on the long head of the biceps tendon in the propagation of SLAP tears by studying the mechanical behavior of the torn superior glenoid labrum. A previously validated finite element model was extended to include a glenoid labrum with type II SLAP tears of three different sizes. The strain distribution within the torn labral tissue with loading applied to the biceps tendon was investigated and compared to the inact and unloaded conditions. The anterior and posterior edges of each SLAP tear experienced the highest strain in the labrum. Labral strain increased with increasing biceps tension. This effect was stronger in the labrum when the size of the tear exceeded the width of the biceps anchor on the superior labrum. Thus, this study indicates that biceps tension influences the propagation of a SLAP tear more than it does the initiation of a tear. Additionally, it also suggests that the tear size greater than the biceps anchor site as a criterion in determining optimal treatment of a type II SLAP tear. Keywords: FE; labrum; SLAP; biceps; propagation A tear of the superior labrum anterior posterior (SLAP tear) is a traumatic lesion in the superior glenoid labrum, which may include the attachment of the long head of the biceps tendon. This tear can contribute to significant pain and disability in the shoulder.1 SLAP tears are classified according to four or more subtypes.1,2 Among them, the type II tear involving detachment of both the superior labrum and the biceps tendon from the glenoid has been reported as the most common lesion. 1,2Both the motion of the humeral head and the traction on the biceps tendon have historically been implicated as predominant factors contributing to SLAP tears in numerous biomechanical studies of the tear mechanism. When SLAP tears were first described, it was hypothesized that they resulted from the traction imposed on the biceps tendon during repeated throwing movements.3 Later, several causal mechanisms were suggested for the SLAP tear, including the combination of humeral head compression and biceps tension 4 and the pulled and twisted biceps tendon. 5However, there is still a knowledge gap concerning how biceps tension relates to SLAP tear pathology and thus the optimal treatment of the SLAP tear. By testing labral strain at a specific phase during certain motions, specific activities at high risk for initiating a SLAP tear have been identified. [6][7][8][9] However, those studies neither observed the strain inside the labral tissue nor investigated the behavior of the labrum with an existing SLAP tear. Moreover, Costa et al. 10 reported that simple traction of the biceps tendon did not play a role in the initiation of the SLAP tear. The lack of clear understanding concerning the role of biceps tension in both the initiation and propagation of a SLAP tear leads to debates among surgeons on the proper treatment for the biceps tendon, which may include arthroscopic repair, debridement, tenodesis, tenotomy, ...

Glenoid Labral Injuries Are More Common Posteriorly Than Superiorly and Are Combined Across Multiple Areas of the Glenoid

“…In addition, these findings indicate that labral injuries associated with glenohumeral instability may have more extensive tissue damage around the glenoid. Taken together, these findings are consistent with anecdotal clinical experience from several centers and from current papers, 3 , 16 , 17 , 18 , 19 , 31 , 32 which suggest that labral injuries that are associated with clinical symptoms may have variable locations of pathology. In addition, the observed injuries may present variable types of injury patterns each of may alter the labral roles that are considered keys in helping confer dynamic concavity/compression for the glenohumeral joint.…”

“…This anatomic area is more rounded and mobile, has been categorized as a mobile organ of tension, a functional tension band, 28 , 37 and encompasses the anatomic area found to be the anchor point for optimum distribution of tensile loads on the biceps labrum complex. 31 The anterior and posterior sections were defined running from their superior demarcation down to the 6:00 position and encompassing the inferior labrum. The inferior labrum is well attached and immobile, and has been categorized as a fixed organ of compression, a bumper conferring edge stability against translation.…”

Isotropic Failure Criteria Are Not Appropriate for Anisotropic Fibrous Biological Tissues

“…The maximum principal stress (MPS) is also commonly reported in finite element simulations of biological tissue [24,25]. Like the von Mises stress, the MPS depends equally on stresses in all directions, thus making it inherently isotropic as well.…”

Histological Analysis of Regenerative Properties in Human Glenoid Labral Regions

“… 55 Biceps tension has been found to cause 13 or to further aggravate SLAP tears. 34 Furthermore, the anterosuperior position has the lowest elastic modulus and yield strength in the glenoid labrum, making it more susceptible to tearing or aggravation. 59 Conversely, the IGL, which has higher elastic modulus and yield strength, 59 has the lowest reoperation rate.…”