Effects of Simulated Injury on Tissue Deformation and Mechanical Properties of the Anteroinferior Glenohumeral Capsule

Author(s):  
Carrie A. Voycheck ◽  
Andrew J. Brown ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The glenohumeral joint is the most dislocated major joint in the body with most dislocations occurring anteriorly. [1] The anterior band of the inferior glenohumeral ligament (AB-IGHL) is the primary passive restraint to dislocation and experiences the highest strains during these events. [2,3] It has been found that injuries to the capsule following dislocation include permanent deformation, which increases joint mobility and contributes to recurrent instability. [4] Many current surgical repair techniques focus on plicating redundant tissue following injury. However, these techniques are inadequate as 12–25% of patients experience pain and instability afterwards and thus may not fully address all capsular tissue pathologies resulting from dislocation. [5] Therefore, the objective of this study was to determine the effect of permanent deformation on the mechanical properties of the AB-IGHL during a tensile elongation. Improved understanding of the capsular tissue pathologies resulting from dislocation may lead to new repair techniques that better restore joint stability and improve patient outcome by placating the capsule in specific locations.

Author(s):  
Daniel P. Browe ◽  
Carrie A. Rainis ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The glenohumeral joint is the most frequently dislocated major joint in the body with about 2% of the population dislocating their shoulders between the ages of 18 and 70 [1]. Instability due to permanent deformation of the glenohumeral capsule is commonly associated with dislocation [2]. Current surgical repair techniques for shoulder dislocations typically consist of plication of the glenohumeral capsule, or folding the tissue over on itself, to reduce redundancy in the capsule and restore stability to the shoulder. Up to 25% of patients who undergo surgery for a shoulder dislocation still experience pain, instability, and recurrent dislocation after surgery [3]. It is hypothesized that the mechanical properties of the glenohumeral capsule change in response to dislocation. In addition, the magnitude and location of these changes may have implications for the ideal location and extent of plication. Therefore, the objective of this study was to quantify the mechanical properties of the axillary pouch of the glenohumeral capsule in tension and shear after anterior dislocation.


Author(s):  
Carrie A. Voycheck ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The glenohumeral joint suffers more dislocations than any other joint, most of which occur in the anterior direction. The anterior band of the inferior glenohumeral ligament (AB-IGHL) is the primary restraint to these dislocations and as a result experiences the highest strains during these events. [1] Injuries to the capsule following dislocation include permanent tissue deformation that increases joint mobility and contributes to recurrent instability. [2] This deformation can be quantified by measuring nonrecoverable strain. [3] Simulated injury of the capsule results in permanently elongated tissue and nonrecoverable strain. Current surgical repair techniques are subjective and may not fully address all capsular tissue pathologies resulting from dislocation. Surgeons typically repair the injured capsule by plicating the stretched-out tissue; however, these techniques are inadequate with 23% of patients needing an additional repair. [4] Quantitative data on the changes in the biomechanical properties of the capsule following dislocation may help to predict the amount of capsular tissue to plicate for restoring normal stability. Therefore, the objectives of this study were to quantify changes in stiffness and material properties of the AB-IGHL tissue sample following simulated injury (creation of nonrecoverable strain).


Author(s):  
Eric J. Rainis ◽  
Carrie A. Voycheck ◽  
Elizabeth A. Timcho ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The glenohumeral joint is the most dislocated major joint in the body and the axillary pouch of the glenohumeral capsule is the primary stabilizer at the extreme ranges of external rotation. [1] Procedures to repair the capsule following dislocation result in 12–25% of patients still experiencing pain and instability. [2] Studies performing clinical exams have found inconsistent data on differences between males and females. Increased laxity in the glenohumeral joint of females has been found as well as overall hypermobility when compared to males. [3,4] However, others have found no differences in overall joint stiffness between genders. [5] These findings suggest that a difference in the mechanical properties might exist between genders. Therefore, the objective of this study was to determine the effects of gender on the mechanical properties of the axillary pouch during tensile loading. A combined experimental and computational approach was used to evaluate the properties of the tissue. This data could potentially be utilized to improve surgical procedures and necessitate gender-specific repair techniques.


Author(s):  
Daniel P. Browe ◽  
Carrie A. Voycheck ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The glenohumeral joint is the most frequently dislocated major joint in the body with about 2% of the population dislocating their shoulders between the ages of 18 and 70 [1]. About 80% of these shoulder dislocations occur in the anterior direction, and they most commonly occur in the apprehension position, which is characterized by 60° of glenohumeral abduction and 60° of external rotation [2]. The most common pathology associated with dislocation is instability due to permanent deformation [3]. Current surgical repair techniques for shoulder dislocations are inadequate with about 25% of patients still experiencing pain and instability after surgery [4]. By assessing the strain distribution, it is possible to determine the stabilizing function of the various capsular regions. In addition, surgeons could benefit from knowing the location and extent of tissue damage when placating the capsule during repair procedures. Therefore, the objective of this study was to determine the location and extent of injury to the anteroinferior capsule during anterior dislocation by quantifying the strain at dislocation and the non-recoverable strain following dislocation.


2004 ◽  
Vol 126 (2) ◽  
pp. 284-288 ◽  
Author(s):  
Susan M. Moore ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The objective of this study was to determine the mechanical properties of the axillary pouch of the inferior glenohumeral ligament in the directions perpendicular (transverse) and parallel (longitudinal) to the longitudinal axis of the anterior band of the inferior glenohumeral ligament. A punch was used to excise one transverse and one longitudinal tissue sample from the axillary pouch of each cadaveric shoulder (n=10). Each tissue sample was preconditioned and then a load-to-failure test was performed. All tissue samples exhibited the typical nonlinear behavior reported for ligaments and tendons. Significant differences (p<0.05) were detected between the transverse and longitudinal tissue samples for ultimate stress (0.8±0.4 MPa and 2.0±1.0 MPa, respectively) and tangent modulus (5.4±2.9 MPa and 14.8±13.1 MPa, respectively). No significant differences (p>0.05) were observed between the ultimate strain (transverse: 23.5±11.5%, longitudinal: 33.3±23.6%) and strain energy density (transverse: 10.8±8.5 MPa, longitudinal: 21.1±15.4 MPa) of the transverse and longitudinal tissue samples. The ultimate stress determined for the longitudinal axillary pouch tissue samples was comparable to a previous study that reported it to be 5.5±2.0 MPa. The ratio of the longitudinal to transverse moduli (3.3±2.8) is considerably less than that of the medial collateral ligament of the knee (30) and interosseous ligament of the forearm (385), suggesting that the axillary pouch functions to stabilize the joint in more than just one direction. Future models of the glenohumeral joint and surgical repair procedures should consider the properties of the axillary pouch in its transverse and longitudinal directions to fully describe the behavior of the inferior glenohumeral ligament.


Author(s):  
William J. Newman ◽  
Richard E. Debski ◽  
Susan M. Moore ◽  
Jeffrey A. Weiss

The shoulder is one of the most complex and often injured joints in the human body. The inferior glenohumeral ligament (IGHL), composed of the anterior band (AB), posterior band (PB) and the axillary pouch, has been shown to be an important contributor to anterior shoulder stability (Turkel, 1981). Injuries to the IGHL of the glenohumeral capsule are especially difficult to diagnose and treat effectively. The objective of this research was to develop a methodology for subject-specific finite element (FE) modeling of the ligamentous structures of the glenohumeral joint, specifically the IGHL, and to determine how changes in material properties affect predicted strains in the IGHL at 60° of external rotation. Using the techniques developed in this research, an improved understanding of the contribution of the IGHL to shoulder stability can be acquired.


Author(s):  
Kelvin Luu ◽  
Carrie A. Voycheck ◽  
Patrick J. McMahon ◽  
Richard E. Debski

The glenohumeral joint is frequently dislocated causing injury to the glenohumeral capsule (axillary pouch (AP), anterior band of the inferior glenohumeral ligament (AB-IGHL), posterior band of the inferior glenohumeral ligament (PB-IGHL), posterior (Post), and anterosuperior region (AS)). [1, 2] The capsule is a passive stabilizer to the glenohumeral joint and primarily functions to resist dislocation during extreme ranges of motion. [3] When unloaded, the capsule consists of randomly oriented collagen fibers, which play a pertinent role in its function to resist loading in multiple directions. [4] The location of failure in only the axillary pouch has been shown to correspond with the highest degree of collagen fiber orientation and maximum principle strain just prior to failure. [4, 5] However, several discrepancies were found when comparing the collagen fiber alignment between the AB-IGHL, AP, and PB-IGHL. [3,6,7] Therefore, the objective was to determine the collagen fiber alignment and maximum principal strain in five regions of the capsule during uniaxial extension to failure and to determine if these parameters could predict the location of tissue failure. Since the capsule functions as a continuous sheet, we hypothesized that maximum principal strain and peak collagen fiber alignment would correspond with the location of tissue failure in all regions of the glenohumeral capsule.


Author(s):  
Brooklynn P. Rowland ◽  
Steven M. Smith ◽  
Carrie A. Voycheck ◽  
Jon K. Sekiya ◽  
Richard E. Debski

The shoulder is the most dislocated major joint in the body; approximately 2% of the population will dislocate their glenohumeral joint between the ages of 18 and 70 [1]. Hill-Sachs lesions, compression fractures resulting from the impaction of the posteroloateral humeral head against the solid anterior rim of the glenoid, occur in roughly 30–40% of all anterior dislocations. Humeral head defects have been linked to postoperative recurrent dislocations and overall instability of the shoulder following stabilization procedures for the capsule [2]. However, the forces and deformations required to create these lesions during shoulder dislocation should be identified to properly develop injury models and new repair techniques. Therefore, the objective of this study was to determine the forces required to create bony lesions on the humeral head and quantify the size of the resulting lesions. In order to achieve this objective, a repeatable testing protocol was developed to consistently produce Hill Sachs lesions.


Author(s):  
Carrie A. Voycheck ◽  
Daniel P. Browe ◽  
Patrick J. McMahon ◽  
Richard E. Debski

Glenohumeral joint stability is maintained by a combination of active and passive soft tissue structures and osteoarticular contact. Anatomical structures that contribute to each of these categories include the rotator cuff muscles, the glenohumeral capsule, and the contact between the articular surfaces of the humeral head and glenoid of the scapula, respectively. Dislocation may result in injury to one or more of these stabilizing components requiring the other structures to account for the deficit. For example, previous research has shown that a torn supraspinatus tendon results in increased bony contact forces during glenohumeral abduction. [1] Another common injury resulting from dislocation is permanent deformation of the glenohumeral capsule as the capsule is the primary static restraint to anterior translation in positions of external rotation. [2] Increased joint translations and rotations usually occur following permanent deformation [3] indicating a loss in joint stability provided by the capsule. These changes in joint kinematics following dislocation imply that differences in the contact forces between the humerus and scapula may exist as well. Irregular contact between two articular surfaces can lead to abnormal wear and an increased risk of osteoarthritis when left untreated. Therefore, the objective of this work was to assess the affect of anterior dislocation on glenohumeral joint stability by determining the in situ force in the glenohumeral capsule and the bony contact forces between the humerus and scapula during a simulated clinical exam at three joint positions in the intact and injured joint.


2000 ◽  
Vol 28 (2) ◽  
pp. 200-205 ◽  
Author(s):  
John E. Kuhn ◽  
Michael J. Bey ◽  
Laura J. Huston ◽  
Ralph B. Blasier ◽  
Louis J. Soslowsky

The late-cocking phase of throwing is characterized by extreme external rotation of the abducted arm; repeated stress in this position is a potential source of glenohumeral joint laxity. To determine the ligamentous restraints for external rotation in this position, 20 cadaver shoulders (mean age, 65 16 years) were dissected, leaving the rotator cuff tendons, coracoacromial ligament, glenohumeral capsule and ligaments, and coracohumeral ligament intact. The combined superior and middle glenohumeral ligaments, anterior band of the inferior glenohumeral ligament, and the entire inferior glenohumeral ligament were marked with sutures during arthroscopy. Specimens were mounted in a testing apparatus to simulate the late-cocking position. Forces of 22 N were applied to each of the rotator cuff tendons. An external rotation torque (0.06 N m/sec to a peak of 3.4 N m) was applied to the humerus of each specimen with the capsule intact and again after a single randomly chosen ligament was cut (N 5 in each group). Cutting the entire inferior glenohumeral ligament resulted in the greatest increase in external rotation (10.2° 4.9°). This was not significantly different from sectioning the coracohumeral ligament (8.6° 7.3°). The anterior band of the inferior glenohumeral ligament (2.7° 1.5°) and the superior and middle glenohumeral ligaments (0.7° 0.3°) were significantly less important in limiting external rotation.


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