Degrees Of Glenohumeral Abduction Research Articles

Influence of distinct anatomic subregions of the supraspinatus on humeral rotation

The supraspinatus, having distinct anterior and posterior subregions, is most commonly considered an abductor of the humerus, but it has also been shown to induce humeral rotation. The objective of this study was to quantify the magnitude and direction of humeral rotation that results from loading the distinct anterior and posterior subregions of the supraspinatus. Fourteen cadaver specimens were tested under four loading conditions based on physiological cross section area of the supraspinatus: (1) anterior only; (2) posterior only; (3) physiologic (each subregion loaded simultaneously); and (4) nonphysiologic (the tendon loaded as a whole). Each specimen was tested at 0, 15, 30, 45, and 60 degrees of glenohumeral abduction in the scapular plane and from 60 degrees of internal to 45 degrees of external rotation in 15 degrees increments. The humeral rotation that occurred with loading from the initial starting rotation position was measured using a rotary variable inductance transducer. In the scapular plane, the anterior subregion of the supraspinatus acts as both an internal and external rotator depending on the initial position of the humerus. The posterior subregion either acted as an external rotator or did not induce rotation. This study demonstrated a distinct functional difference between the anatomic subregions of the supraspinatus. This understanding will help to improve testing methods and the development of repair strategies of the supraspinatus.

Biomechanical stability of an arthroscopic anterior capsular shift and suture anchor repair in anterior shoulder instability: a human cadaveric shoulder model

It was hypothesized that an arthroscopic Bankart repair with suture anchors supplies sufficient anterior shoulder stability, which cannot be improved by an additional capsular shift. In an experimental biomechanical human cadaver study, we tested ten fresh human cadaver shoulders in a robot-assisted shoulder simulator. External rotation and glenohumeral translation were measured at 0 degrees and 80 degrees of glenohumeral abduction. All measurements were performed under the following conditions: on the non-operated shoulder; following the setting of three arthroscopic portals; following an arthroscopic anterior capsular shift; following a simulated Bankart lesion; and following an arthroscopic Bankart repair. The application of three arthroscopic portals resulted in a significant increase of the anterior (P = 0.01) and antero-inferior translation (P = 0.03) at 0 degrees and 80 degrees abduction, as well as an increase in external rotation at 80 degrees abduction (P = 0.03). Capsular shift reduced external rotation (P = 0.03), but did not significantly decrease translation. Simulating anterior shoulder instability, glenohumeral translation significantly increased, ranging from 50 to 279% of physiological translation. Arthroscopic shoulder stabilization resulted in a decrease of translation in all tested directions to approximately physiologic levels. External rotation in 0 degrees abduction was thus decreased significantly (P = 0.003) to an average of 19 degrees . The study proved that an arthroscopic anterior capsular shift in a cadaveric model decreases external rotation without a significant influence on glenohumeral translation. Arthroscopic shoulder stabilization with suture anchors thus sufficiently restores increased glenohumeral translation, but also decreases external rotation in neutral abduction. An anatomic reconstruction of the Bankart lesion without overconstraining of the antero-inferior capsule should therefore be the aim in arthroscopic anterior shoulder stabilization.

Determining the Resting Position of the Glenohumeral Joint in Subjects Who Are Healthy

The resting position is frequently used by clinicians in the examination and early treatment of patients with joint impairments. However, there is a lack of research on the kinematic characteristics of the resting position of the glenohumeral (GH) joint. The aim of this study was to define the resting position of the GH joint by quantifying the humeral head translation and axial rotational range of motion (ROM). The anterior and posterior translation of the humeral head and the rotational ROM of the dominant arm were assessed in the seated position at multiple abduction positions in 15 subjects who were healthy by use of an electromagnetic tracking device. A force of 80 N and a torque of 4 N.m were applied during the measurement procedures for the translation of the humeral head and the rotational ROM, respectively. The mean resting position determined by rotational movement was located at 49.8 degrees of GH abduction. However, the mean resting position determined by translational movement was located at 23.7 degrees of GH abduction and was significantly lower than the resting position determined by rotational movement (t=5.45, P=.000). The mean resting position for rotational movement is consistent with the already accepted range of 30 to 60 degrees for a "loosely packed" position of the GH joint. The mean resting position for translational movement appears to be lower than 30 to 60 degrees. The results of this study suggest that, at least for the GH joint, different resting positions should be assessed with different movement criteria (accessory or physiological movement).

Primärstabilität des Kapsel-Labrum-Komplexes nach Rekonstruktion mit Mitek-Bioknotless-Fadenankern am humanen Schulterkadavermodell

This study examines the postoperative stability of the Mitek Bioknotless anchor system with biomechanical draw-out pulling in human cadaver shoulders. With simulation of anterior shoulder dislocation a test group (n=10, Ø 45 years) was tested against a native group (n=8, Ø 47 years). All shoulders were dissected up to the passive stabilizers. In the test group an artificial Bankart lesion was created and repaired with three Mitek Bioknotless anchors. The humeri of both groups were fixed in 60 degrees glenohumeral abduction and 90 degrees external rotation and then dislocated in a ventral direction. For evaluation purposes the ultimate draw-out strength, mode of failure, translation of humeral head, capsular slope, and bone density in the test group were measured. In the test group the ultimate strength was a median of 937 N (min. 554 N, max. 1,294 N) with 28 bony anchor dislocations, 1 suture rupture, and 1 capsular rupture, and in the native group with 6 Bankart and 2 HAGL lesions it was 1,214 N (708 N, 1,471 N). The bone density showed a positive correlation to the draw-out strength regarding cortical density and total density. Regarding the high draw-out strength the Mitek Bioknotless anchor system provides enough stability for early functional treatment.

Orientation feedback during simulated simple translation tests has little clinical significance on the magnitude and precision of glenohumeral joint translations

The repeatability of shoulder instability clinical examinations has been reported to be poor, producing a large range of translations. The objective of this study was to determine the effect of providing the clinician with joint orientation feedback on the magnitude and precision of glenohumeral joint kinematics. A 6-degree of freedom magnetic tracking system was used to determine the kinematics of the humerus with respect to the scapula (n=8 cadaveric shoulders). The joints were preconditioned with simple loading tests five times. At 60 degrees of glenohumeral abduction and 0 degrees of flexion/extension, a clinician then applied an anterior and posterior load to the humerus until a manual maximum simulating a simple translation test (STT) was achieved at 0, 30, and 60 degrees of external rotation with and without angular orientation feedback of the humerus with respect to the scapula. The precision for the external rotation was within 4.3 degrees for the feedback group and 17.5 degrees for the no feedback group over all external rotations. For achieving the target external rotation of 30 degrees , there was a significant difference in precision between the feedback and no feedback groups (p<0.05). The magnitudes of the anterior translations were 18.2+/-5.3, 15.5+/-5.1, and 9.9+/-5.5 mm for the feedback group and 19.3+/-6.6, 17.5+/-4.9, and 11.5+/-5.3 mm for the no feedback group, at 0, 30, and 60 degrees of external rotation, respectively. There was a significant difference in the precision of anterior translation at 30 and 60 degrees of external rotation for 4 of 8 specimens (p<0.05). Significant differences in the precision of the posterior translation was only detected at 0 degrees of external rotation for 3 of 8 specimens (p<0.05). Based on the data obtained, providing orientation feedback to a clinician performing a simulated STT results in increased precision for not only the target external rotations but also the resulting glenohumeral translations. While providing feedback may be a necessary step to achieving precise results for experimental studies, the magnitudes of translations in the anterior and posterior directions were relatively similar for the feedback and no feedback states indicating little benefit for clinical examinations.

Biomechanical Evaluation of Different Suture Anchors for the Stabilization of Anterior Labrum Lesions

The aim of the study was to investigate the biomechanical performance of different devices for anterior shoulder reconstruction in a clinically relevant human cadaver shoulder model. Biomechanical cadaveric study. The soft tissue, except for the joint capsule, was dissected from 28 fresh-frozen human shoulder specimens. A Bankart lesion was created and repaired with 3 suture anchors. The devices tested were the 2.4-mm Fastak (Arthrex, Karlsfeld, Germany) with either Ethibond (Ethicon, Westwood, MA) no. 2 or 3, the 2.8-mm Fastak with Ethibond no. 2, the Panalok (Mitek, Norwood, MA) with Ethibond no. 2 with a modified setting technique, and the 8-mm Suretac (Acufex Microsurgical, Mansfield, MA). The specimens were anteriorly dislocated in 60 degrees glenohumeral abduction and 90 degrees external rotation. Load was measured continuously and failures were noted. The experimental groups were compared with each other and with a control group with intact shoulders. Bankart repair with 2.4-mm Fastaks and Ethibond no. 2 and 3 failed at a mean load of 342.0 N and 692.2 N, respectively, predominantly by suture rupture at the eyelet of the anchor. Shoulder reconstruction with 2.8-mm Fastaks failed at an average load of 722.8 N, mostly by suture rupture at the knot. The difference to the 2.4-mm Fastak with Ethibond no. 2 was significant (P < .05). The mean load to failure was 983.8 N in the Panalok group, and the most frequent failure mode was suture rupture at the knot. Bankart repair with Suretac failed at an average load of 468.4 N, typically by capsular damage at the repair site. Capsular injuries in the control group occurred at a mean load of 958.2 N. Anterior shoulder reconstruction with 2.4-mm Fastak with Ethibond no. 2 and with Suretac were statistically significantly inferior to the control group (P < .05). All tested devices allow stable anterior shoulder reconstruction, but we recommend the Panalok and the 2.8-mm Fastak because they provided greater stability than either the 2.4-mm Fastak or the Suretac in our experiments. Suretac can possibly cause additional capsular damage in redislocations after Bankart repair. This cadaveric study gives an insight into the biomechanical performance of a Bankart repair with different devices directly postoperative and shows possible failure modes and additional injuries in case of early traumatic redislocation.

Type II SLAP lesions: A new scoring system— the sulcus score

A new scoring system-the sulcus score-was developed to differentiate between a large superior labral sulcus and a type II superior labrum anterior-posterior (SLAP) lesion. The sulcus scoring system permits quantification of the size of the superior labral sulcus and the severity of a type II SLAP lesion. Specifically, the depth of the superior labral sulcus was classified into 4 grades, and the length was recorded by clock position. The sulcus score was then calculated by multiplying the depth (grade) by the length (the number of "hours" from the clock position). After stretching of the anterior capsule into excessive humeral external rotation at 60 degrees glenohumeral abduction, the sulcus score of cadaveric shoulders increased significantly (before, 3.4; after, 6.8), indicating the extension of the superior labral sulcus and resulting in a pathologically created type II SLAP lesion. The intraclass correlation coefficient and mean difference were 0.77 and 0.8 +/- 0.7, respectively, for intraobserver repeatability and 0.72 and 0.9 +/- 0.6, respectively, for interobserver reproducibility. The sulcus score provided a consistent and objective means for quantitatively describing the size and severity of type II SLAP lesions. Clinical assessment of the superior labral sulcus by use of the sulcus score may be useful for the diagnosis and treatment of type II SLAP lesions.

Determining the resting position of the glenohumeral joint: a cadaver study.

Single-session repeated-measures design. To define the resting position of the glenohumeral joint by investigating the magnitude of the anterior and posterior displacements of the humeral head and medial and lateral rotation ranges of motion (ROMs) of the glenohumeral joint at different abduction angles in cadaver specimens. The resting position of a joint is the position in the joint's ROM at which the joint capsule has its greatest laxity. It is frequently chosen as the position for assessing and treating joints with dysfunction. However, no study has been conducted to determine the resting position of the glenohumeral joint. Seven freshly frozen cadaver shoulder specimens (age at time of death [mean +/- SD] was 66.9 +/- 2.5 years) were studied. Specimens were mounted on a system that uses computer-controlled hydraulics and motors to induce and monitor translation and rotation movements of the glenohumeral joint. The magnitudes of total displacement (DTotal) of the head of the humerus and total ROM (RTotal) of the glenohumeral joint were measured in the plane of the scapula at 0 degrees (neutral), 30 degrees, 40 degrees, 50 degrees, 60 degrees, and the end range of glenohumeral joint abduction. The resting position was determined as the midpoint of the shared range of the 95% to 99.9% confidence intervals of the predicted abduction position where the peaks of displacement and rotation occurred. The DTotal measurements (mean +/- SD) at 0 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and the end range of glenohumeral joint abduction were 30.53 +/- 9.35, 44.87 +/- 7.34, 45.35 +/- 8.53, 43.99 +/- 10.02, 39.63 +/- 9.85, and 23.80 +/- 10.42 mm, respectively. The RTotal measurements (mean +/- SD) for the same positions were 67.15 degrees +/- 15.87 degrees, 95.64 degrees +/- 24.26 degrees, 98.88 degrees +/- 29.56 degrees, 97.08 degrees +/- 30.17 degrees, 90.91 degrees +/- 28.73 degrees, and 63.48 degrees +/- 25.93 degrees, respectively. The resting position was located at 39.33 degrees +/- 4.37 degrees of glenohumeral abduction (45.13% +/- 7.58% of the available abduction ROM). The resting position (Y) varied linearly with the maximum available abduction ROM (X) (Y = 0.607X - 13.120, R2 = 0.679, F = 10.61, P = 0.023). There was a main effect of joint position on both displacement (P<0.001) and rotation ROM (P<0.001). In the plane of the scapula, the resting position of the glenohumeral joint (angle measured between the scapula and humerus) occurred at 39 degrees of abduction (45% of the maximum available abduction ROM) and varied linearly with the amount of available abduction ROM. This finding suggests that in patients with glenohumeral joint hypomobility the resting position is located closer to neutral and that evaluation and treatment should be initiated accordingly at a smaller angle of abduction than the traditional resting position. Our data were derived from cadaver specimens, therefore, caution should be taken when generalizing the results of the present study to a patient population.

Structural Properties of the Supraspinatus Tendon in Two Joint Positions

The supraspinatus tendon is frequently involved in rotator cuff tears. It has been suggested that joint position affects the structural mechanics of the tendon–bone complex. The purpose of this study was to determine regional variations in structural properties of the supraspinatus tendon in two glenohumeral positions. Supraspinatus tendons from 17 fresh frozen cadavers were divided into three strips of equal width and tested with a material-testing machine. The arm orientation was either in hanging position or 60 degrees glenohumeral abduction corresponding to 90 degrees arm abduction assuming 30 degrees scapular rotation. Tensile force, tendon elongation and failure mode were recorded. Overall, there was no significant difference in structural properties between hanging arm position and 60 degrees of glenohumeral abduction (p>0.05). However, the mean ultimate load (385 N, SD 56 N) and mean ultimate stress (14 MPa, SD 3 MPa) of the anterior tendon section with the arm in glenohumeral abduction were lower in 60 degrees abduction than in the hanging arm position (611 N, SD 276 N; 24 MPa, SD 10 MPa). In hanging arm position, the anterior tendon portion had a significantly greater ultimate load and stiffness than the middle and posterior portions (p<0.05). The regional variation in structural properties substantiates the clinical finding that rotator cuff ruptures easily extend posteriorly. Our study suggests that glenohumeral abduction reduces the failure strength of the supraspinatus tendon, specifically of its anterior portion. In our study, the maximum load of the anterior portion was substantially higher than predicted maximum loads transmitted physiologically through the entire tendon.

STRUCTURAL PROPERTIES OF THE SUPRASPINATUS TENDON IN TWO JOINT POSITIONS

The supraspinatus tendon is frequently involved in rotator cuff tears. It has been suggested that joint position affects the structural mechanics of the tendon–bone complex. The purpose of this study was to determine regional variations in structural properties of the supraspinatus tendon in two glenohumeral positions. Supraspinatus tendons from 17 fresh frozen cadavers were divided into three strips of equal width and tested with a material-testing machine. The arm orientation was either in hanging position or 60 degrees glenohumeral abduction corresponding to 90 degrees arm abduction assuming 30 degrees scapular rotation. Tensile force, tendon elongation and failure mode were recorded. Overall, there was no significant difference in structural properties between hanging arm position and 60 degrees of glenohumeral abduction (p&gt;0.05). However, the mean ultimate load (385 N, SD 56 N) and mean ultimate stress (14 MPa, SD 3 MPa) of the anterior tendon section with the arm in glenohumeral abduction were lower in 60 degrees abduction than in the hanging arm position (611 N, SD 276 N; 24 MPa, SD 10 MPa). In hanging arm position, the anterior tendon portion had a significantly greater ultimate load and stiffness than the middle and posterior portions (p&lt;0.05). The regional variation in structural properties substantiates the clinical finding that rotator cuff ruptures easily extend posteriorly. Our study suggests that glenohumeral abduction reduces the failure strength of the supraspinatus tendon, specifically of its anterior portion. In our study, the maximum load of the anterior portion was substantially higher than predicted maximum loads transmitted physiologically through the entire tendon.

Effects of Position and Speed on Eccentric and Concentric Isokinetic Testing of the Shoulder Rotators

This study investigated the effects of position and speed on peak torque values of the shoulder internal and external rotators during concentric and eccentric activity. The dominant shoulder of 9 males and 10 females, 21-33 years, were tested at two velocities (60 and 180 degrees /sec) in two positions (45 degrees glenohumeral abduction and 45 degrees glenohumeral flexion) and two contraction types (eccentric and concentric). Results indicated that 1) concentric internal rotation decreased significantly (p < 0.0001) at the higher speed in males, 2) eccentric external rotation increased significantly (p < 0.003) at the higher speed in females, and 3) peak torque values were significantly greater (p < 0.01) in the 45 degrees glenohumeral abduction position compared to the 45 degrees glenohumeral flexion position during eccentric and concentric external rotation for both females and males, and for eccentric internal rotation in females. These findings are useful when planning to progress the intensity of the testing and training of the shoulder rotators according to patient tolerance. J Orthop Sports Phys Ther 1989;11(2):64-69.