Relationships Between Total and Non-Recoverable Strain Fields in Glenohumeral Capsule During Shoulder Subluxation

Abstract

Non-recoverable strain in the glenohumeral capsule is of prime clinical significance, but the factors that contribute to non-recoverable strain are largely unknown. This study examined the relationship between total and non-recoverable strain in the antero-inferior glenohumeral capsule using an experimental model. Maximum principal total strain alone explained up to 35% of the variance in non-recoverable strain. A multiple regression model, including variables for lateral position and specimen, explained 50% of the variance in non-recoverable strain. Both linear and quadratic terms for maximum principal total strain were significant predictors of non-recoverable strain. The correlation of total and non-recoverable strain directions exhibited a slope of nearly 1:1. The regression model showed that non-recoverable strain is likely to be low for small levels of total strain, and increase non-linearly with total strain. Non-recoverable strain tended to be higher closer to the glenoid, even when controlling for total strain. Minimum principal total strain was not a significant predictor of non-recoverable strain for the cases examined, indicating that the glenohumeral capsule may demonstrate uniaxial failure behavior even when loaded biaxially. These results are important toward prediction of non-recoverable strain in computational models of glenohumeral subluxation, as well as for theoretical models of ligament failure.

Location and magnitude of capsular injuries varies following multiple anterior dislocations of the shoulder: Implications for surgical repair

“…11 In terms of the nonrecoverable strain of the capsule following dislocations, prior studies have only determined the strain distribution of the capsule during a simulated clinical exam for uninjured shoulders and the nonrecoverable strain due to joint subluxations. 13,14,16,33,35 Only one additional study has quantified the resulting nonrecoverable strain due to a single dislocation and compared it to the location and extent of the injury to the anteroinferior capsule. 17 The PAPH was reported to experience the highest nonrecoverable stain in the apprehension position.…”

“…[8][9][10][11] Nonrecoverable strain occurs when the capsule is loaded beyond its elastic limit and is a contributor to to recurrent anterior instability. 12 Prior studies have evaluated the nonrecoverable strain of the glenohumeral capsule during a simulated clinical exam and anterior subluxation of the shoulder, [13][14][15][16] but only following a single dislocation of the glenohumeral joint in the anterior direction. 12,17 During surgical repair, the glenohumeral capsule is often plicated and shifted to reduce joint laxity, especially following multiple dislocations.…”

All-Arthroscopic, 270° Reconstruction of the Inferior Glenohumeral Ligament With Palmaris Longus Autograft

“…Recent studies have described the influence of age and previous instability episodes on shoulder capsule composition, with younger patients and patients with multidirectional instability showing significantly higher elastin density 17 . At the same time, the presence of residual plastic deformity of the anteroinferior capsule (which includes the anterior bundle of the IGHL) due to repetitive dislocations or subluxations seems to play a crucial role 18 . These 2 conditions contribute to an insufficient capsuloligamentous complex that is prone to higher failure rates if only the native soft tissue has been repaired.…”

“…Many authors advocate that patients with hyperlaxity have a higher risk of failure because of inherent capsule deficiency 15, 16, 17. These patients show a different proportion of elastic fibers in the capsule, which causes residual stretching and leads to an increased intra-articular volume over time, even after a Bankart repair 18 . Thus, meticulous surgical technique and restoration of anatomy are of paramount importance.…”

Effects of simulated injury on the anteroinferior glenohumeral capsule

“…Similar results have been reported when a univariate regression model was used to examine the relationship between the maximum principal strain at the injured and nonrecoverable strain states produced by applying varying degrees of glenohumeral subluxation (R 2 = 0.35, r = 0.6). [18] …”