Glenohumeral Joint Stiffness Research Articles

An injectable thermosensitive hyaluronic acid/pluronic F-127 hydrogel for deep penetration and combination therapy of frozen shoulder

Frozen shoulder (FS) is a common and progressive shoulder disorder that causes glenohumeral joint stiffness, characterized by inflammation and fibrosis. The treatment options are quite limited, and the therapeutic response is hindered by the fibrous membrane formed by excessive collagen and the rapid removal by synovial fluid. To address these challenges, we designed a hyaluronic acid/Pluronic F-127 (HP)-based injectable thermosensitive hydrogel as a drug carrier loaded with dexamethasone and collagenase (HPDC). We screened for an optimal HP hydrogel that can sustain drug release for approximately 10 days both in vitro and in vivo. In the meanwhile, we found that HP hydrogel could inhibit the proliferation and diminish the adhesion capacity of rat synovial cells induced by transforming growth factor-β1. Furthermore, using an established immobilization rat model of FS, intra-articular injection of HPDC significantly improved joint range of motion compared to medication alone. Relying on sustained drug release, the accumulated collagen fibers were degraded by collagenase to promote the deep delivery of dexamethasone. These findings showed a positive combined treatment effect of HPDC, providing a novel idea for the comprehensive treatment of FS.

Objective measurement of Inferior-Directed stiffness in glenohumeral joint using a specially designed robotic device in healthy shoulders; Within- and Between-Session reliability

Clinical assessment of capsuloligamentous structures of the glenohumeral joint has been qualitative and subjective in nature, as demonstrated by limited intra- and inter-rater reliability. Robotic devices were utilized to develop a clinically objective measurement technique for glenohumeral joint stiffness. The purpose of this study was to quantify the amount of inferior-direction stiffness of the glenohumeral joint using a safe clinical device in the asymptomatic individuals, and to determine between trial and between session reliability of the robotic device. Twenty healthy subjects were recruited via convenience sampling. Inferior-directed translation and applying force were measured using displacement and force sensors of a robotic device. The stiffness values were calculated as the mean of the slopes of the linear portions of the force–displacement curves for the cycles obtained after familiarization and preconditioning. Four trials for each measurement occasion were averaged to determine the stiffness value for each subject in one session. Repeatability of glenohumeral joint stiffness measurements for between trials and between two sessions was determined using intraclass correlation values and standard error of the measurements. The mean stiffness value was 1.50 N/mm (±0.40) and 1.52 N/mm (±0.40), respectively. The robotic device for stiffness assessment was reliable for repeated measures of stiffness in one session, and between sessions with ICC equal 0.96 (95% CI 0.93–0.98), and 0.97 (95% CI 0.95–0.99), respectively. The SEM between the trials was in each session 0.08 N/mm. The results of this study provide that our robotic technique for quantifying glenohumeral joint stiffness is precise and reproducible.

Paper #17 - Remplissage of an off-track hill-sachs lesion is necessary to restore biomechanical glenohumeral joint stability in a bipolar bone loss model

Purpose: To validate the “glenoid track” concept in a cadaveric bipolar bone loss model and to test whether “on-track” and “off-track” lesions can be adequately stabilized with Bankart or remplissage repair techniques. Methods: Eight fresh-frozen cadaver shoulders were tested in a custom shoulder rig with passive axial rotation and then progressive translational loading (10-40N). The injury conditions included glenoid bone loss of 15% with “on-track” (15%) and “off-track” (30%) Hill-Sachs lesions. Repair conditions included Hill-Sachs remplissage and/or Bankart repair. Engagement of bipolar lesions was noted, and glenohumeral joint stiffness was calculated from force-displacement measurements. Results: As seen in Table 1, for on-track lesions, engagement was rare and stability was adequately restored with Bankart repair only. For off-track lesions, engagement was routine and the addition of Hill-Sachs remplissage was necessary to restore biomechanical stability. As seen in Figure 1, injury conditions had much lower stiffness than the intact shoulder. Stiffness after off-track HS remplissage was much larger than that of the intact shoulder, injury conditions, and Bankart repair only conditions. Bankart repair of the on-track HS injury condition improved stiffness to near intact, while addition of on-track HS remplissage increased stiffness over Bankart repair alone at 90°. Conclusions: The glenoid track concept is supported by this model of two Hill-Sachs lesions with 15% glenoid bone loss. Our results support the paradigm of Bankart repair for on-track lesions and Bankart plus remplissage for off-track lesions. Remplissage of on-track lesions might be considered for increased stability in high-risk patients. Level of Evidence: Biomechanical study. Table 1Force at 60 or 90° causing engagement of the Hill-Sachs lesions with the glenoid. – indicates no engagement. Bold indicates that a given repair affected the engagement of the experimental condition to the left Figure 1Glenohumeral joint stiffness calculated from the translation of the humeral head with applied loads from 10-40 N at two rotation positions for the various injury and repair conditions of the shoulder. View Large Image Figure Viewer Download Hi-res image

The aging effects on the glenohumeral joint stiffness in association with anteroposterior glide mobilization: in vivo robotic testing

The aging effects on the glenohumeral joint stiffness in association with anteroposterior glide mobilization: in vivo robotic testing

Superficial shoulder muscle co-activations during lifting tasks: Influence of lifting height, weight and phase

This study aimed to assess the level of co-activation of the superficial shoulder muscles during lifting movement. Boxes containing three different loads (6, 12, and 18kg) were lifted by fourteen subjects from the waist to shoulder or eye level. The 3D kinematics and electromyograms of the three deltoids, latissimus dorsi and pectoralis major were recorded. A musculoskeletal model was used to determine direction of the moment arm of these muscles. Finally an index of muscle co-activation named the muscle focus was used to evaluate the effects of lifting height, weight lifted and phase (pulling, lifting and dropping phases) on superficial shoulder muscle coactivation. The muscle focus was lower (more co-contraction) during the dropping phase compared to the two other phases (−13%, p<0.001). This was explained by greater muscle activations and by a change in the direction of the muscle moment arm as a function of glenohumeral joint position. Consequently, the function of the shoulder superficial muscles varied with respect to the glenohumeral joint position. To increase the superficial muscle coactivation during the dropping phase may be a solution to increase glenohumeral joint stiffness.

A quantitative method for evaluating inferior glenohumeral joint stiffness using ultrasonography

Subluxation of the affected shoulder in post-stroke patients is associated with nerve disorders and muscle fatigue. Clinicians must be able to accurately and reliably measure inferior glenohumeral subluxation in patients to provide appropriate treatment. However, quantitative methods for evaluating the laxity and stiffness of the glenohumeral joint (GHJ) are still being developed. The aim of this study was to develop a new protocol for evaluating the laxity and stiffness of the inferior GHJ using ultrasonography under optimal testing conditions and to investigate changes in the GHJ from a commercially available humerus brace and shoulder brace. Multistage inferior displacement forces were applied to create a glide between the most cephalad point on the visible anterosuperior surface of the humeral head and coracoid process in seven healthy volunteers. GHJ stiffness was defined as the slope of the linear regression line between the glides and different testing loads. The testing conditions were defined by different test loading mechanisms (n=2), shoulder constraining conditions (n=2), and loading modes (n=4). The optimal testing condition was defined as the condition with the least residual variance of measured laxity to the calculated stiffness under different testing loads. A paired t-test was used to compare the laxity and stiffness of the inferior GHJ using different braces. No significant difference was identified between the two test loading mechanisms (t=0.218, p=0.831) and two shoulder constraining conditions (t=−0.235, p=0.818). We concluded that ultrasonographic laxity measurements performed using a pulley set loading mechanism was as reliable as direct loading. Additionally, constraining the unloaded shoulder was proposed due to the lower mean residual variance value. Moreover, pulling the elbow downward with loading on the upper arm was suggested, as pulling the elbow downward with the elbow flexed and loading on the forearm may overestimate stiffness and pain in the inferior GHJ at the loading point due to friction between the wide belt and skin. Furthermore, subjects wearing a humerus brace with a belt, which creates the effect of lifting the humerus toward the acromion, had greater GHJ stiffness compared to subjects wearing a shoulder brace without a belt to lift the humerus under the proposed testing conditions. This study provides experimental evidence that shoulder braces may reduce GHJ laxity under an external load, implying that the use of a humeral brace can prevent subluxation in post-stroke patients. The resulting optimal testing conditions for measuring the laxity and stiffness of the GHJ is to constrain the unloaded shoulder and bend the loaded arm at the elbow with loading on the upper arm using a pulley system.

Stiffness Regulation and Muscle-Recruitment Strategies of the Shoulder in Response to External Rotation Perturbations

The complex interactions between capsuloligamentous structures and muscle-recruitment strategies that maintain glenohumeral stability remain unclear. The purposes of the present study were to determine whether stiffness regulation and muscle-activation strategies differed under varying joint positions and levels of contraction in the shoulder and to determine the relationship between generalized joint laxity, glenohumeral joint laxity, and joint stiffness. Forty healthy, physically active subjects with a mean age (and standard deviation) of 25.2 +/- 4.6 years, a mean height of 174.7 +/- 6.7 cm, and a mean mass of 73.1 +/- 13.8 kg were tested. Shoulder stiffness and the activation of muscles (including the rotator cuff and the anterior deltoid) were measured at two levels of internal rotation torque (0% and 50% of maximum) and two joint positions (0 degrees and 90% of maximum external rotation) before and after a 5 degrees external rotation perturbation. Generalized laxity and glenohumeral joint laxity (in the anterior, posterior, and inferior directions) were also assessed. Stiffness was 77% greater at 50% of maximum internal rotation torque than at 0% of maximum internal rotation torque (p < 0.001) but was not significantly different between joint positions (p = 0.73). From 0% to 50% of maximum internal rotation torque, preparatory and reactive recruitment of the subscapularis increased significantly more (p < 0.05) than those of the other muscles. Also, subscapularis preparatory activity was 36% greater in 0 degrees of external rotation than in 90% of maximum external rotation (p < 0.01). Generalized joint laxity (as indicated by a score of >/=4) was present in 20% of the subjects. Glenohumeral joint laxity (as indicated by a grade of >/=2) was present in the anterior, posterior, and inferior directions in 13%, 15%, and 15% of the subjects, respectively. No correlation existed between passive stiffness and generalized or glenohumeral laxity (r = -0.12 to 0.29; p = 0.08 to 0.48). Moderate levels of muscle contraction can significantly increase glenohumeral joint stiffness and stability. Preactivation of the subscapularis appears to be the primary dynamic stabilizer with the arm in 0 degrees of external rotation. However, with the arm in 90% of maximum external rotation (the apprehension position), less subscapularis activity is observed and the maintenance of stability may shift toward other musculoskeletal structures because joint stiffness does not change. A relationship between generalized joint laxity, glenohumeral laxity, and stiffness was not observed in healthy subjects.

Reliability of stiffness measured in glenohumeral joint and its application to assess the effect of end-range mobilization in subjects with adhesive capsulitis

End-range mobilization techniques are recommended for the treatment of patients with hypomobile joints. The purposes of this study were (1) to assess the reliability of a glenohumeral (GH) stiffness measurement technique and (2) apply the measurement technique on subjects with adhesive capsulitis to compare the GH end-range stiffness and rotational range of motions (ROMs) before and immediately after the application of end-range translational mobilization techniques. Fifteen normal subjects were recruited for assessment of test–retest reliability. Four men and two women with adhesive capsulitis in the glenohumeral joint (mean disease duration=6.5 months, SD=2.7) were treated with end-range mobilization by an experienced physical therapist. The passive abduction angles, rotational ROM and GH joint stiffness were measured by the same observer before and immediately after end-range mobilization treatment. The test–retest reliability was assessed and revealed good to excellent reliability in anterior–posterior glenohumeral joint stiffness and fair to excellent reliability of GH stiffness in posterior–anterior direction. The GH joint stiffness decreased and passive abduction range of motion increased immediately after end-range mobilization of the shoulder joint. The use of intensive mobilization techniques may help to decrease the risk of further stiffness or joint contracture progression in patients with adhesive capsulitis.

Stiffness, Viscosity, and Upper-Limb Inertia about the Glenohumeral Abduction Axis

To evaluate the dynamic properties of the shoulder and understand how they are controlled by the central nervous system, glenohumeral-joint stiffness and viscosity and upper-limb inertia were quantified under various levels of muscle contraction in seven healthy human subjects. Through a cast attachment, the upper limb was perturbed in a precise pattern by a computer-controlled servomotor to manifest the dynamic properties of the joint. The recorded joint position and torque were used to estimate joint stiffness and viscosity and upper-limb inertia. With moderate muscle contraction, the stiffness and viscosity increased several fold. A stiffer shoulder joint associated with stronger muscle contraction made the shoulder more stable and protected it from potential injuries during strenuous tasks. Joint viscosity, especially the stronger viscous damping associated with more strenuous contraction, smoothed shoulder movement and stabilized the joint. From the control viewpoint, the glenohumeral joint responded to the central nervous system more quickly with increasing muscle contraction, which was useful during strenuous tasks. On the other hand, the central nervous system controlled stiffness and viscosity synchronously so that it dealt with only a nearly constant damping ratio of the joint over various levels of contraction, which simplified its task substantially. This approach quantified the dynamic and static properties of the shoulder under various levels of contraction more accurately and completely than a manual test, and it can potentially be used to evaluate changes in these properties caused by musculoskeletal injuries and their surgical treatments.

Stiffness, viscosity, and upper-limb inertia about the glenohumeral abduction axis.

To evaluate the dynamic properties of the shoulder and understand how they are controlled by the central nervous system, glenohumeral-joint stiffness and viscosity and upper-limb inertia were quantified under various levels of muscle contraction in seven healthy human subjects. Through a cast attachment, the upper limb was perturbed in a precise pattern by a computer-controlled servomotor to manifest the dynamic properties of the joint. The recorded joint position and torque were used to estimate joint stiffness and viscosity and upper-limb inertia. With moderate muscle contraction, the stiffness and viscosity increased several fold. A stiffer shoulder joint associated with stronger muscle contraction made the shoulder more stable and protected it from potential injuries during strenuous tasks. Joint viscosity, especially the stronger viscous damping associated with more strenuous contraction, smoothed shoulder movement and stabilized the joint. From the control viewpoint, the glenohumeral joint responded to the central nervous system more quickly with increasing muscle contraction, which was useful during strenuous tasks. On the other hand, the central nervous system controlled stiffness and viscosity synchronously so that it dealt with only a nearly constant damping ratio of the joint over various levels of contraction, which simplified its task substantially. This approach quantified the dynamic and static properties of the shoulder under various levels of contraction more accurately and completely than a manual test, and it can potentially be used to evaluate changes in these properties caused by musculoskeletal injuries and their surgical treatments.

Patterns of stiffness during clinical examination of the glenohumeral joint

Objective. The purpose of our study was to develop a quantitative technique for performing clinical laxity tests, and to characterize the force–displacement response patterns in normal shoulders during two commonly applied clinical tests in different arm positions. Design. The study was an in vivo clinical experiment. Background. We developed a method to objectively quantify the effects of clinical laxity testing at the shoulder. No previous studies have measured the applied force during clinical testing along with the displacement so that glenohumeral joint stiffness could be determined in vivo. Methods. Manually applied forces were measured and shoulder displacement was recorded using electromagnetic tracking sensors during clinical stability testing in 21 subjects with normal shoulders. End-range stiffness was calculated and compared across all test conditions using repeated measures analysis of variance. Results. The maximum force applied by the examiner to reach clinical end-point across all tests ranged from 101–113 N The stiffest position for posterior drawer test was at 180° of abduction with the arm in internal rotation. This position was the most compliant position for the anterior drawer test. Only by internally rotating the arm did the force–dislpacement pattern change significantly ( P < 0.05). For anterior drawer tests, the patterns changed significantly ( P < 0.05) only when the arm was in external rotation. Conclusions. Results showed that end-range stiffness was predominantly dependent on humeral rotation angle and not effected by arm abduction angle for the three angles studied. Stiffness from anterior drawer tests was highest with the arm in external rotation, and stiffness from posterior drawer tests was highest with the arm in internal rotation. Relevance This study has several clinically relevant implications for quantification of a clinical shoulder examination, and as a valuable teaching tool. Our findings also question some accepted notions about clinical “closed-packed” joint positions. The study provides normal patterns of force–displacement and normative stiffness values that can be compared to patients with shoulder pathology for similar testing.

THE ROLE OF PASSIVE MOBILIZATION IN THE IMMEDIATE MANAGEMENT OF THE FRACTURED NECK OF HUMERUS

Conservative management, including an early introduction of pendular exercises to prevent shoulder stiffness, has always been advocated in the treatment of the fractured neck of humerus. However, the problem of glenohumeral joint stiffness can still be present many weeks after the fracture. It was proposed that the inclusion of passive mobilization in the treatment programme could lessen this problem. A method of passive mobilization which could be begun within the first few days post fracture, was used in a pilot study of 14 patients with fractures of the neck of humerus. Initial results indicated that with the inclusion of passive mobilization in an active treatment programme, good functional results could be obtained, while the period of rehabilitation and the number of treatments could also be substantially reduced.