The influence of rotator cuff tears on glenohumeral stability during abduction tasks (original) (raw)
Related papers
Influence of rotator cuff tears on glenohumeral stability during abduction tasks
Journal of Orthopaedic Research, 2016
One of the main goals in reconstructing rotator cuff tears is the restoration of glenohumeral joint stability, which is subsequently of utmost importance in order to prevent degenerative damage such as superior labral anterior posterior (SLAP) lesion, arthrosis, and malfunction. The goal of the current study was to facilitate musculoskeletal models in order to estimate glenohumeral instability introduced by muscle weakness due to cuff lesions. Inverse dynamics simulations were used to compute joint reaction forces for several static abduction tasks with different muscle weakness. Results were compared with the existing literature in order to ensure the model validity. Further arm positions taken from activities of daily living, requiring the rotator cuff muscles were modeled and their contribution to joint kinetics computed. Weakness of the superior rotator cuff muscles (supraspinatus; infraspinatus) leads to a deviation of the joint reaction force to the cranial dorsal rim of the glenoid. Massive rotator cuff defects showed higher potential for glenohumeral instability in contrast to single muscle ruptures. The teres minor muscle seems to substitute lost joint torque during several simulated muscle tears to maintain joint stability. Joint instability increases with cuff tear size. Weakness of the upper part of the rotator cuff leads to a joint reaction force closer to the upper glenoid rim. This indicates the comorbidity of cuff tears with SLAP lesions. The teres minor is crucial for maintaining joint stability in case of massive cuff defects and should be uprated in clinical decision-making.
Glenohumeral stability in simulated rotator cuff tears
Journal of Biomechanics, 2009
Rotator cuff tears disrupt the force balance in the shoulder and the glenohumeral joint in particular, resulting in compromised arm elevation torques. The trade-off between glenohumeral torque and glenohumeral stability is not yet understood. We hypothesize that compensation of lost abduction torque will lead to a superior redirection of the reaction force vector onto the glenoid surface, which will require additional muscle forces to maintain glenohumeral stability. Muscle forces in a single arm position for five combinations of simulated cuff tears were estimated by inverse dynamic simulation (Delft Shoulder and Elbow Model) and compared with muscle forces in the non-injured condition. Each cuff tear condition was simulated both without and with an active modeling constraint for glenohumeral stability, which was defined as the condition in which the glenohumeral reaction force intersects the glenoid surface. For the simulated position an isolated tear of the supraspinatus only increased the effort of the other muscles with 8%, and did not introduce instability. For massive cuff tears beyond the supraspinatus, instability became a prominent factor: the deltoids were not able to fully compensate lost net abduction torque without introducing destabilizing forces; unfavorable abductor muscles (i.e. in the simulated position the subscapularis and the biceps longum) remain to compensate the necessary abduction torque; the teres minor appeared to be of vital importance to maintain glenohumeral stability. Adverse adductor muscle co-contraction is essential to preserve glenohumeral stability.
The effect of rotator cuff tears on reaction forces at the glenohumeral joint
Journal of Orthopaedic Research, 2002
The rotator cuff muscles maintain glenohumeral stability by compressing the hunieral head into the glenoid. Disruption of the rotator cuff compromises concavity compression and can directly affect the loads on the glenohumeral joint. The purpose of this study was to quantify tlie effect of rotator cuff tears on the magnitude and direction of glenohumeral joint reaction forces during active shoulder abduction in the scapular plane using nine cadaveric upper extremities. Motion of the full upper extremity was simulated using a dynamic shoulder testing apparatus. Glenohumeral joint reaction forces were measured by a universal forcemoment sensor. Five conditions of rotator cuff tears were tested: Intcict, bicoiiiplete Suprcispiiiutus Teur, Coiiiplete SLil)rcis~)iiicitus Teur, Supru.~~~inutuslInfi.u.~piizatirs Tear, and Global Tear. Reaction forces a t the glenohumeral joint were found to steadily increase throughout abduction and peaked at maximum abduction for all conditions tested. There were no significant differences in reaction force magnitude for the intact condition (337 f 88 N) or those involving an isolated incomplete tear (296 f 83 N ) or complete tear (300 f 85 N) of the supraspinatus tendon. Extension of tears beyond the supraspinatus tendon into the anterior and posterior aspect of the rotator cuff led to a significant decrease in the magnitude of joint reaction force . Similarly, such tears resulted in a significant change in the direction of the reaction force at the glenohumeral joint. These results suggest that joint reaction forces are significantly affected by the integrity of the rotator cuff, specifically, by tlie transverse force couple formed by the anterior and posterior aspects of the cuff. The quantitative data obtained in this study on the effect of rotator cuff tears on magnitude and direction of the reaction force a t the glenohumeral joint helps clarify the relationship between joint motion, joint compression and stability.
Tendon-defect and muscle-unloaded models for relating a rotator cuff tear to glenohumeral stability
Journal of Orthopaedic Research, 2000
Rotator cuff tear and glenohumeral instability arc closely related. Any tear may disturb muscle force gencration due to pain inhibition. In addition, a full-thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon-defect model. dynamic and static elements of the joint were sacrificed. In a muscle-unloadcd model, only the dynamic element was removed. The location and size of the defect were also investigated. The effcct on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand. with a larger tear the defect had a greater effect than muscle-unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention. therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer.
Effects of rotator cuff tears on muscle moment arms: A computational study
Journal of Biomechanics, 2007
Rotator cuff tears cause morphologic changes to cuff tendons and muscles, which can alter muscle architecture and moment arm. The effects of these alterations on shoulder mechanical performance in terms of muscle force and joint strength are not well understood. The purpose of this study was to develop a three-dimensional explicit finite element model for investigating morphological changes to rotator cuff tendons following cuff tear. The subsequent objectives were to validate the model by comparing model-predicted moment arms to empirical data, and to use the model to investigate the hypothesis that rotator cuff muscle moment arms are reduced when tendons are divided along the force-bearing direction of the tendon. The model was constructed by extracting tendon, cartilage, and bone geometry from the male Visible Human data set. Infraspinatus and teres minor muscle and tendon paths were identified relative to the humerus and scapula. Kinetic and kinematic boundary conditions in the model replicated experimental protocols, which rotated the humerus from 451 internal to 451 external rotation with constant loads on the tendons. External rotation moment arms were calculated for two conditions of the cuff tendons: intact normal and divided tendon. Predicted moment arms were within the 1-99% confidence intervals of experimental data for nearly all joint angles and tendon sub-regions. In agreement with the experimental findings, when compared to the intact condition, predicted moment arms were reduced for the divided tendon condition. The results of this study provide evidence that one potential mechanism for the reduction in strength observed with cuff tear is reduction of muscle moment arms. The model provides a platform for future studies addressing mechanisms responsible for reduced muscle force and joint strength including changes to muscle length-tension operating range due to altered muscle and tendon excursions, and the effects of cuff tear size and location on moment arms and muscle forces. r
Journal of Shoulder and Elbow Surgery, 2014
Background: Superior migration of the humeral head after massive rotator cuff tear (mRCT) is thought to lead to cuff tear arthropathy. Previous biomechanical studies have demonstrated the ability of the pectoralis major and latissimus dorsi (PM/LD) muscles to resist this migration. This study examined the role of PM/ LD muscles on glenohumeral joint forces and acromiohumeral contact pressures in a mRCT model. Methods: Six cadaveric shoulders were tested using a custom shoulder-testing system. Muscle insertions of the rotator cuff, deltoid, and PM/LD were preserved and used for muscle loading. Specimens were tested in 3 different humeral rotation positions at 0 abduction and 2 rotation positions at 60 abduction. Testing was performed for intact specimens, after supraspinatus removal, and after supraspinatus/infraspinatus/ teres minor removal. PM/LD were loaded or unloaded to determine their effect. Humeral head kinematics, glenohumeral joint forces, and acromiohumeral contact area and pressure were measured. Results: For the mRCT condition at 0 abduction, unloading the PM/LD resulted in superior shift of the humeral head. Acromiohumeral contact pressures were undetectable when the PM/LD were loaded but increased significantly after PM/LD unloading. After mRCT, superior joint forces were increased and compressive forces were decreased compared with intact; loading the PM/LD resolved these abnormal forces in some testing conditions. Conclusion: In mRCT, the PM and LD muscles are effective in improving glenohumeral kinematics and reducing acromiohumeral pressures. Strengthening or neuromuscular training of this musculature, or both, may delay the progression to cuff tear arthropathy.
Journal of Orthopaedics and Traumatology
Background Rotator cuff muscles stabilise the glenohumeral joint and contribute to the initial abduction phase with other shoulder muscles. This study aimed to determine if the load-induced increase in shoulder muscle activity during a 30° abduction test is influenced by asymptomatic or symptomatic rotator cuff pathologies. Materials and Methods Twenty-five patients with unilateral rotator cuff tears (age, 64.3 ± 10.2 years), 25 older control subjects (55.4 ± 8.2 years) and 25 younger control subjects (26.1 ± 2.3 years) participated in this study. Participants performed a bilateral 30° arm abduction and adduction movement in the scapular plane with handheld weights (0–4 kg). Activity of the deltoid, infraspinatus, biceps brachii, pectoralis major, latissimus dorsi and upper trapezius muscles was analysed at maximum abduction angle after normalisation to maximum voluntary contraction. Shoulders were classified into rotator cuff tendinopathy, asymptomatic and symptomatic rotator cuff ...
The Journal of Bone and Joint Surgery-American Volume, 2000
The purpose of this study was to investigate quantitatively the dynamic glenohumeral stability provided by the rotator cuff muscles in the late-cocking phase of throwing. Using ten cadaveric shoulders, a new biomechanical parameter (dynamic stability index) was calculated considering compressive and shear forces to the glenoid provided by each cuff muscle. The rotator cuff muscles provided the joint with significant dynamic stability in the late cocking. However, the dynamic stability provided by the cuff muscles with the arm in coronal plane significantly decreased when compared with that in the scapular plane. Rehabilitation of the throwing athletes should emphasize strengthening of the external and internal rotators. Moving the arm into the coronal plane in the late cocking phase should be avoided by a specific strengthening program to prevent further anatomic damage to the static stabilizers.
Journal of Orthopaedic Research, 2018
Rotator cuff tears are known to affect clinical outcome of reverse total shoulder arthroplasty (RSA). This study aimed to use computational modelling to quantify the effect of rotator cuff tear severity on muscle and joint forces after RSA, as well as stresses at the glenosphere, base-plate, fixation screws, scapula, and humeral components. A multi-body musculoskeletal model of the glenohumeral joint was developed comprising the scapula, humerus and nine major upper limb muscles. Simulations of abduction and flexion after RSA were performed in the case of the intact rotator cuff and tears to (i) supraspinatus; (ii) supraspinatus and infraspinatus, and (iii) supraspinatus, infraspinatus and subscapularis. The intact and supraspinatus deficient rotator cuff resulted in the largest calculated muscle forces, glenohumeral joint contact forces and implant stresses. Peak glenohumeral joint forces during flexion were lower than those during abduction in all cases; however, substantially more posterior joint shear force was generated during flexion than abduction. A tear involving the supraspinatus and infraspinatus reduced glenohumeral joint forces by a factor of 8.7 during abduction (603.1 N) and 7.1 during flexion (520.7 N) compared to those in the supraspinatus deficient shoulder. RSA with an intact or supraspinatus deficient rotator cuff produces large glenohumeral joint forces that may increase base-plate failure risk, particularly during flexion when posterior shear forces are largest. Infraspinatus tears after RSA greatly reduce glenohumeral joint compression and may ultimately reduce joint stability. Future research ought to focus on experimental validation of subject-specific muscle recruitment strategies and joint loading after RSA.