The developmental anatomy of the neonatal glenohumeral joint

The embryologic development of the capsular ligaments, synovial lining, rotator cuff, and bony structures of the shoulder is incompletely understood. The purpose of this study is to report the gross and microscopic anatomy of the developing glenohumeral joint on the basis of dissections of fetal shoulder specimens. After Institutional Review Board approval from our hospital, 51 shoulders in 37 fetal specimens were obtained from cases of fetal demise. The gestation time of these specimens ranged from 9 to 40 weeks. The morphology of the capsule, labrum, and associated ligaments were studied by dissection under a dissecting microscope. High-resolution radiographs were made, and sections were processed for routine histology. There was noted to be minimal variation in the shape and slope of the acromion. The coracoid was much larger in relation to the shoulder than in the mature shoulder. The coracoacromial ligament was grossly evident at this stage of development, with distinct anterolateral and posteromedial bands in this ligament. The inferior glenohumeral ligament was seen as a prominent thickening in the capsule, whereas the middle and superior glenohumeral ligaments were thinner and more difficult to identify as distinct structures. Upon histologic examination, the inferior glenohumeral ligament was seen to consist of several layers of organized collagen fibers. The inferior glenohumeral ligament inserted into the labrum and margin of the glenoid. The capsule was much thinner in the region superior to the inferior glenohumeral ligament. A rotator interval capsular defect was often present, and the coracohumeral ligament was seen as a distinct structure as early as 15 weeks. A bare spot in the glenoid was not observed. This study indicates that some of the important functional elements of the structure of the mature human shoulder are present early in development, including the glenohumeral and coracohumeral ligaments. The coracoacromial ligament plays a significant role in the formation of the coracoacromial arch in the neonatal shoulder. The presence of a capsular rotator interval indicates that this aspect of capsular anatomy is congenital.     

The coracoacromial ligament: morphology and study of acromial enthesopathy

The coracoacromial ligament (CAL), normally a superior restraint against humeral translation, is frequently involved in rotator cuff impingement pathology. However, surgical excision of the CAL is not always clinically successful. Little anatomic information exists about the morphology and function of this ligament. The CAL and glenohumeral joint in 56 cadaveric shoulders were examined in 31 cadavers. Nineteen dimensional parameters were obtained by direct measurement. In 16 shoulders, specific attention was directed at the anterior band of the CAL. Variation exists in the morphology of the CAL. The most common configuration of the CAL was two distinct ligamentous bands that could be classified anatomically as an anterolateral band (ALB) and posteromedial band (PMB). The ALB commonly extended to the posterolateral aspect of the acromion. Furthermore, it frequently extended anterolaterally to the acromion, ending in a coracoacromial falx. Spur formation had occurred in 10 of 16 shoulders evaluated and always appeared in the ALB. Spur formation in the ALB correlated with a focal CAL that was narrower, less divergent, shorter, and thicker than a diffuse CAL that did not have a spur. The mean angle of diversion between the ALB and PMB, when a spur was present, was 31 degrees compared with 45 degrees when no spur was present. CAL band thickness varied, with the ALB being thicker at the acromion than at the coracoid and the PMB being thicker at the coracoid than at the acromion. During arthroscopic subacromial decompression, failure to visualize the anterolateral corner of the acromion adequately may result in incomplete resection of the CAL, especially if the PMB is mistaken to be the entire ligament. Incomplete removal of the CAL may be a factor in clinical failures of arthroscopic subacromial decompression. The preferential location of spurs in the ALB suggests that it is a major load-bearing structure. Furthermore, the ALB is thicker at the acromion, suggesting increased strain. Our data suggest that a possible function of the CAL is to dampen stress on the acromion from muscle activity.     

Release of the coracoacromial ligament can lead to glenohumeral laxity: a biomechanical study

The purpose of this study was to determine change in glenohumeral joint translation after release of the coracoacromial ligament. Six fresh, frozen unpaired glenohumeral joints were tested in a neutral position and at 30 degrees internal and 30 degrees external rotation of the humerus at 0 degrees, 30 degrees, and 60 degrees of abduction on a custom glenohumeral joint translation testing apparatus. A joint compression load of 20 N was simulated; then a 15-N load was applied to the humerus in anterior, posterior, superior, and inferior directions, and translations on the glenoid were measured with an electromagnetic tracking device. The tests were then repeated after a 1.5-cm section of the coracoacromial ligament was released from the acromion. A multivariate analysis of variance was used for statistical analyses with a P value of.05 as the level of significance. At 0 degrees and 30 degrees of abduction, release of the coracoacromial ligament resulted in a significant increase in glenohumeral joint translations, in both the anterior and inferior directions. In addition, the differences in translation between before and after the release of the coracoacromial ligament decreased in all directions as glenohumeral abduction increased, and they were not significant at 60 degrees of abduction in any of the rotations. The results of this study suggest that the coracoacromial ligament has a role in static restraint of the glenohumeral joint. It provides a suspension function and may restrain anterior and inferior translations through an interaction with the coracohumeral ligament. Although this is a biomechanical study without simulation of the shoulder muscles, it indicates that the coracoacromial ligament contributes to glenohumeral stability. Caution should be exercised in the release of the coracoacromial ligament in those with rotator cuff pain associated with glenohumeral instability.     

Contact pressure and glenohumeral translation following subacromial decompression: how much is enough?

Subacromial decompression is a common surgical procedure that has historically included coracoacromial ligament resection. However, recent reports have advocated preserving the coracoacromial ligament to avoid the potential complication of anterosuperior escape. The optimal subacromial decompression would achieve a smooth coracoacromial arch and decreased rotator cuff contact pressures while preserving the function of the arch in glenohumeral stability. We hypothesized that a subacromial decompression with a limited acromioplasty with preservation of the coracoacromial ligament can decrease extrinsic pressure on the rotator cuff similar to a coracoacromial ligament resection, without altering glenohumeral translation. Three different subacromial decompressions, including a "smooth and move," a limited acromioplasty with coracoacromial ligament preservation, and a coracoacromial ligament resection, were performed on 6 cadaveric specimens with intact rotator cuffs. Glenohumeral translation and peak rotator cuff pressure during abduction were recorded. No change in translation was observed after a smooth and move or a limited acromioplasty. Compared to baseline specimens, anterosuperior translation was increased at 30° of abduction following coracoacromial ligament resection (P<.05). Baseline rotator cuff pressure was greatest during abduction with the arm in 30° of internal rotation. Peak rotator cuff pressure decreased up to 32% following a smooth and move, up to 64% following a limited acromioplasty, and up to 72% following a coracoacromial ligament resection. Based on the present study, a limited acromioplasty with coracoacromial ligament preservation may best provide decompression of the rotator cuff while avoiding potential anterosuperior glenohumeral translation.     

The rotator interval: anatomy, pathology, and strategies for treatment

Over the past two decades, it has become accepted that the rotator interval is a distinct anatomic entity that plays an important role in affecting the proper function of the glenohumeral joint. The rotator interval is an anatomic region in the anterosuperior aspect of the glenohumeral joint that represents a complex interaction of the fibers of the coracohumeral ligament, the superior glenohumeral ligament, the glenohumeral joint capsule, and the supraspinatus and subscapularis tendons. As basic science and clinical studies continue to elucidate the precise role of the rotator interval, understanding of and therapeutic interventions for rotator interval pathology also continue to evolve. Lesions of the rotator interval may result in glenohumeral joint contractures, shoulder instability, or in lesions to the long head of the biceps tendon. Long-term clinical trials may clarify the results of current surgical interventions and further enhance understanding of the rotator interval.     

Anatomy and functional aspects of the rotator interval

The anatomy of the region between the supraspinatus and subscapularis tendons, called the rotator interval, was studied in 22 shoulders of 12 cadavers. Its function was then examined by sequential cutting of tendon or rotator interval structures. The rotator interval was found to be composed of parts of the supraspinatus, subscapularis, coracohumeral ligament, superior glenohumeral ligament, and glenohumeral joint capsule. A medial part composed of 2 layers was defined and distinguished from a more lateral part composed of 4 layers. The most superior 3 layers of the lateral part formed a fibrous plate. The medial part was found to primarily limit inferior translation and, to a lesser extent, external rotation. The fibrous plate of the lateral part of the rotator interval mainly limited external rotation of the adducted arm. The coracohumeral ligament played a key role in external rotation as well as in inferior translation.     

The function of passive stabilizers of the glenohumeral joint--a biomechanical study

In a biomechanical study we evaluated the passive stabilizing ligaments of 9 fresh shoulder specimens with mercury bands. While preparing the specimens we found two interesting entities: there are fibers of the coracohumeral ligament running from the humeral head to the coracoacromial ligament and there was an reproducible thickening in the posterior joint capsule. Functional evaluation shows that the coracohumeral ligament limits external rotation independently of the amount of abduction as well as inferior subluxation. The mediale glenohumeral ligament shows the highest tension in external rotation and 30 degrees abduction. The anterior inferior ligament strengthens the joint capsule in abduction and external rotation. The posterior inferior ligament shows the highest tension in abduction and internal rotation. CLINICAL RELEVANCE: Immobilization in internal rotation and adduction may lead to shortening of the coracohumeral ligament, which may result in severe limitation of external rotation and abduction. Resection of the coracoacromial ligament relaxes the coracohumeral ligament leading to an increased cranio-caudal instability. The posterior inferior ligament is complementary to the anterior inferior ligament thus stabilizing the shoulder joint in abduction and internal rotation. Sparing this structure in arthroscopy with dorsal portals and restoring in the case of a rupture seems to be of value for a normal joint function.     

Role of the coracoacromial ligament as restraint after shoulder hemiarthroplasty

Patients with an irreparable rotator cuff tear and glenohumeral degeneration often are treated with hemiarthroplasty. This procedure has proven effective as long as the coracoacromial ligament remained intact. The ligament reportedly acts as a restraint against anterosuperior dislocation. The purpose of the current study was to test the role of the coracoacromial ligament as an anterosuperior restraint after hemiarthroplasty in shoulders from cadavers with simulated irreparable rotator cuff tears. Six fresh-frozen shoulders were dissected to mimic a massive rotator cuff tear. After a hemiarthroplasty was done, each shoulder was mounted in a fixture, which was attached to a materials testing device. Using this device, the role of the coracoacromial ligament was evaluated by loading the shoulders in various positions and then measuring displacement before and after excision of the ligament. The mean difference in anterosuperior displacement was 3.44 mm. In all shoulders, subjective observation revealed that the humeral head often becomes wedged between the coracoid and the acromion during axial loading after excision of the coracoacromial ligament. Therefore, the coracoacromial ligament should be preserved to enhance the stability of the joint and to preserve the superior fulcrum.     

Arthroscopic rotator cuff interval capsular closure

Closure of the rotator cuff interval is an important component of open stabilization techniques in shoulder surgery. This study describes a technique in which the deep layer of the capsule within the rotator cuff interval is closed arthroscopically. The effect of closure of this capsule within the rotator cuff interval on glenohumeral motion also is quantified. Sutures were placed from the superior glenohumeral ligament to the middle glenohumeral ligament and tied intra-articularly in fresh-frozen cadaveric shoulders. Closure of the interval capsule resulted in statistically significant limitation of humeral elevation, external rotation, and extension. Arthroscopic closure of the deep layer of the rotator cuff interval capsule produced a visible superior shifting of the middle and inferior glenohumeral ligaments and imbricated the anterosuperior capsule of the shoulder. In addition, this procedure can be performed in conjunction with arthroscopic capsulolabral reconstruction.     

The relationship of the glenohumeral joint capsule to the rotator cuff

The glenohumeral joint capsules of 23 shoulders in which the rotator cuff was not torn were studied by gross dissection and histologic methods. The cuff tendons were resected, leaving the intact capsule attached to the bones. This dissection method provided a unique overview of the capsule in situ and allowed the areas of cuff tendon and muscle attachment to be mapped. The capsule was found to be a continuous cylinder between humerus and glenoid. On approximately one-third of the capsule (the portion adjacent to the humeral tuberosities), tight insertions of cuff tendons were noted. The superior segment between subscapularis and supraspinatus contained the coracohumeral ligament. This segment appeared to reinforce the cuff through a transversely oriented band similar to the glenohumeral ligaments.     

The role of the rotator interval capsule in passive motion and stability of the shoulder.

The purpose of this study was to characterize the role of the capsule in the interval between the supraspinatus and subscapularis tendons with respect to glenohumeral motion, translation, and stability. We used a six-degrees-of-freedom position-sensor and a six-degrees-of-freedom force and torque-transducer to determine the glenohumoral rotations and translations that resulted from applied loads in eight cadaver shoulders. The range of motion of each specimen was measured with the capsule in the rotator interval in a normal state, after the capsule had been sectioned, and after it had been imbricated. Operative alteration of this capsular interval was found to affect flexion, extension, external rotation, and adduction of the humerus with respect to the scapula. Modification of this portion of the capsule also affected obligate anterior translation of the humeral head on the glenoid during flexion. Limitation of motion and obligate translation were increased by operative imbrication and diminished by sectioning of the rotator interval capsule. Passive stability of the glenohumeral joint was evaluated with the use of anterior, posterior, and inferior stress tests. Instability and occasional frank dislocation of the glenohumeral joint occurred inferiorly and posteriorly after section of the rotator interval capsule. Imbrication of this part of the capsule increased the resistance to inferior and posterior translation.     

Coracoacromial ligament tension in vivo

Tension in the coracoacromial (CA) ligament has been postulated as the mechanism of acromial spur formation. Five patients (mean age, 58 years) undergoing open rotator cuff repair were recruited. A differential variable reluctance transducer (DVRT) was inserted into the CA ligament parallel to the fiber orientation. The DVRT measured linear displacement as the glenohumeral joint was moved through 90 degrees of abduction and full internal/external rotation. The CA ligament was then removed with the DVRT in situ. The specimen was mounted on a material-testing machine. Load was applied in the line of the CA ligament fibers, and the DVRT output recorded. The CA ligament was found to be under tension, which was lowest with the arm adducted (mean, 8.9 N; range, 3.7-22 N) and highest in abduction (mean, 15.7 N; range, 6.5-38 N). This study confirms CA ligament tension in vivo as a possible stimulus for acromial spur formation.     

Dynamic capsuloligamentous anatomy of the glenohumeral joint

Though many anatomic and biomechanical studies have been performed to elucidate capsuloligamentous anatomy of the glenohumeral joint, no previous studies have evaluated capsuloligamentous anatomy during rotator cuff contraction. The purpose of this study was to define and document the orientation and interrelationship between the glenohumeral ligaments during simulated rotator cuff contraction. Six fresh cadaveric shoulders were arthroscoped to document and grade ligamentous anatomy. The superior and middle glenohumeral ligaments and the anterior and posterior bands of the inferior glenohumeral ligament complex were labeled by an arthroscopicassisted technique with a linked metallic bead system. Shoulders were then placed onto an experimental apparatus that simulated rotator cuff function through computer-controlled servo-hydrolic actuators attached to the rotator cuff and biceps by a clamp and cable-and-pulley system. Simulated rotator cuff action and manual placement allowed shoulders to be placed into three positions of rotation (neutral, internal, and external) in three positions of scapular plane abduction (0°, 45°, 90°). Anteroposterior and axillary lateral plane radiographs were taken in each position to document orientation of all four ligaments. Both the superior and middle glenohumeral ligaments were maximally lengthened in 0° and 45° abduction and external rotation and appeared to shorten in all positions of abduction. The anterior and posterior bands of the inferior glenohumeral ligament complex maintained a cruciate orientation in all positions of abduction in the anteroposterior plane, except at 90° abduction and external rotation, where they are parallel. This cruciate orientation is due to the different location of the glenoid origin and humeral insertion of each band and may allow reciprocal tightening of each during rotation. The glenohumeral capsule is composed of discreet ligaments that undergo large charges in orientation during rotation. The superior and middle glenohumeral ligaments appear to complement the inferior glenohumeral ligaments, with the former tightening in adduction and the latter tightening in abduction. This relationship permits the large range of motion normally seen in the glenohumeral joint.     

Anterior shoulder stability: Contributions of rotator cuff forces and the capsular ligaments in a cadaver model

The purpose of this study was to quantify in a biomechanical model the contributions to shoulder joint stability that are made by tensions in the four tendons of the rotator cuff and by static resistance of defined portions of the capsular ligaments. A materials testing machine was used to directly determine anterior joint laxity by measurement of the force required to produce a standard anterior subluxation. Shoulders were tested in external or neutral humeral rotation. Data were analyzed by multiway analysis of variance with regression analysis. This model simulated tensions in the rotator cuff musculature by applying static loads at the tendon insertion sites acting along the anatomic lines of action. A load in any of the cuff tendons resulted in a measurable and statistically significant contribution to anterior joint stability. The contributions between different tendons were not significantly different and did not depend on the humeral rotation (neutral or external). In neutral humeral rotation the superior and middle glenohumeral ligaments together function equally with the inferior glenohumeral ligament as primary stabilizers against anterior humeral translation. The posterior capsule is a secondary stabilizer. The external rotation of the abducted humerus increases anterior stability by more than doubling the stability contribution from the inferior glenohumeral ligament. The stability contribution from the posterior capsule is larger in external rotation than in neutral rotation but is still of secondary magnitude. In external rotation the stability contribution of the anterior capsule, including the superior glenohumeral ligament and the middle glenohumeral ligament, becomes insignificant. The model presented here simulates the combined effect of two major sources of shoulder stability. This versatile model permits the direct measurement of the contributions to anterior shoulder stability that are made by tensions in the rotator cuff tendons and by static resistance of defined capsular zones. The use of multiple regression analysis-a standard statistical technique but one relatively new to the orthopaedic literature-permits quantitative determination of the contribution of each independent variable to the dependent variable, shoulder stability.     

Contribution of the passive properties of the rotator cuff to glenohumeral stability during anterior-posterior loading.

The passive properties of the rotator cuff have been shown to provide some stability during anterior-posterior (AP) translation. However, the relative importance of the rotator cuff to joint stability remains unclear. The purpose of this study was to quantify the force contributions of the rotator cuff and of capsuloligamentous structures at the glenohumeral joint during AP loading. We hypothesized that the rotator cuff acts as a significant passive stabilizer of the glenohumeral joint and that its contribution to joint stability is comparable to the contribution made by the components of the glenohumeral capsule. A robotic/universal force-moment sensor testing system was used to determine both the multiple "degrees of freedom" joint motion and the in situ force carried by each soft tissue structure during application of an 89N AP load at 4 abduction angles. The percent contribution of the rotator cuff to the resisting force of the intact joint during AP loading was significantly greater during posterior loading (35% +/- 26%) than during anterior loading at 60 degrees of abduction (P < .05). The contribution of the rotator cuff (i.e., 29% +/- 16% at 30 degrees of abduction) was found to be significantly greater than the contributions of the capsule components during posterior loading at 30 degrees, 60 degrees, and 90 degrees of abduction (P < .05). However, no differences could be found between the respective contributions of the rotator cuff and the capsule components during anterior loading. The results support our hypothesis and suggest that passive tension in the rotator cuff plays a more significant role than other soft tissue structures in resisting posterior loads at the glenohumeral joint. The important role of the rotator cuff during posterior loading may be a result of the thin posterior joint capsule compared with the anterior capsule, which has several thickenings. This information increases our understanding of posterior stability at the glenohumeral joint during clinical laxity tests.     

Variations in the superior capsuloligamentous complex and description of a new ligament

Although the rotator cuff interval and the adjacent ligaments are gaining interest because of their importance for glenohumeral instability and adhesive capsulitis, there seems to be some confusion about their anatomy. This study reinvestigates the superior capsular structures in 110 cadaveric shoulders by a combination of arthroscopy, dissection, histology, and functional analysis. The structure of the superior capsule was found to be more complex than suspected until now. The coracohumeral, coracoglenoid, and superior glenohumeral ligaments joined with a circular transverse band to form the anterior limb of a suspension sling. This was 9 to 26 mm wide at its midportion. In 90% of the specimens, there also was a posterior limb composed of a broad fibrous sheet, 6 to 26 mm wide at its midportion. This hitherto unrecognized posterosuperior glenohumeral ligament joined posterolaterally with the circular transverse band. Four types of configuration for the superior complex could be identified. The suspension sling formed by the superior complex functions in the same way as the hammock formed by the inferior glenohumeral ligament complex. The posterior limb seems to restrict internal rotation, like the anterior limb restricts external rotation. The expanded knowledge of the superior capsular complex increases the understanding of the pathology involved in anterosuperior and posterosuperior impingement, as well as articular-sided rotator cuff tears. It also has clinical implications for rotator cuff interval and biceps pulley lesions, because these areas are bordered by the anterior limb of the superior complex, as well as for adhesive capsulitis, where we can now understand why internal rotation is limited and why the release needs to be extended posterosuperiorly.     

Rotator cuff interval reconstruction

Five pairs of cadaveric shoulders underwent posterior and anterior drawer and inferior sulcus tests in five progressive conditions: intact, vented, following opening of the rotator cuff interval, reconstruction of the interval, and transfer of the coracoacromial ligament. The surgical treatments--vented, open rotator cuff interval, reconstruction, and coracoacromial ligament transfer--had an effect compared to the intact shoulders on the inferior stiffness (P = .00002) and on the anteroposterior stiffness (P = .00031). The difference between the stiffness of the reconstructed rotator cuff interval compared to the coracoacromial ligament transfer was significant for loading in the AP direction (P = .006) and for loading in the inferior direction (P = .005).     

Glenohumeral motion after complete capsular release.

The range of glenohumeral motion is primarily limited by the joint capsule. If the capsule is contracted, greater restriction in glenohumeral motion is exhibited. Release of a tight capsule has been an effective means of managing refractory stiffness of the glenohumeral joint. The effect of a complete capsular release on glenohumeral kinematics has not been previously studied in a cadaver model. Elevation, rotation, and translation of eight cadaveric glenohumeral preparations were studied before and after complete capsular release. As the intact joint was positioned near the limits of motion, glenohumeral torque rose rapidly with relatively small concomitant increases in elevation and rotational angles. Notable torque, due to tension in the capsule or cuff, ensued only after glenohumeral elevation reached approximately 80% of maximal range. After complete capsular release, maximal elevation increased on average 15%, yet retained definitive endpoints due to residual tension in the rotator cuff. Axial humeral rotation with an intact capsule decreased as maximum elevation approached, especially at elevation angles greater than 60 degrees. Maximum internal rotation was less than external, for all planes except +90 degrees. After complete capsular release, the greatest net gains for external rotation tended to be in the posterior scapular planes, whereas gains for internal rotation tended to be in the anterior scapular planes. Maximal translation in an intact vented capsule was 21 mm, 14 mm, and 15 mm in the anterior, posterior, and inferior directions, respectively. After complete capsular release, translation increased in all positions with maximal anterior, posterior, and inferior translations of 28 mm, 25 mm, and 28 mm, respectively. In general, relative gains in translation were greater in planes posterior to the scapula and at extremes of the range of motion. Although large glenohumeral translations were measured, no preparation could be dislocated before or after complete capsular release. Complete capsular release significantly increased glenohumeral range of motion and translation. The intact rotator cuff myotendinous units serves to limit the range of motion and translation after all capsuloligamentous attachments are rendered incompetent by complete capsular release.     

In situ force distribution in the glenohumeral joint capsule during anterior-posterior loading.

Our objective was to examine the function of the glenohumeral capsule and ligaments during application of an anterior-posterior load by directly measuring the in situ force distribution in these structures as well as the compliance of the joint. We hypothesized that interaction between different regions of the capsule due to its continuous nature results in a complex force distribution throughout the glenohumeral joint capsule. A robotic/universal force-moment sensor testing system was utilized to determine the force distribution in the glenohumeral capsule and ligaments of intact shoulder specimens and the joint kinematics resulting from the application of external loads at four abduction angles. Our results suggest that the glenohumeral capsule carries no force when the humeral head is centered in the glenoid with the humerus in anatomic rotation. However, once an anterior-posterior load is applied to the joint, the glenohumeral ligaments carry force (during anterior loading, the superior glenohumeral-coracohumeral ligaments carried 26+/-16 N at 0 degrees and the anterior band of the inferior glenohumeral ligament carried 30+/-21 N at 90 degrees). Therefore, the patient's ability to use the arm with the humerus in anatomic rotation should not be limited following repair procedures for shoulder instability because the repaired capsuloligamentous structures should not carry force during this motion. Separation of the capsule into its components revealed that forces are being transmitted between each region and that the glenohumeral ligaments do not act as traditional ligaments that carry a pure tensile force along their length. The interrelationship of the glenohumeral ligaments forms the biomechanical basis for the capsular shift procedure. The compliance of the joint under our loading conditions indicates that the passive properties of the capsule provide little resistance to motion of the humerus during 10 mm of anterior or posterior translation with anatomic humeral rotation. Finally, this knowledge also enhances the understanding of arm positioning relative to the portion of the glenohumeral capsule that limits translation during examination under anesthesia.     

The coracoacromial ligament: the morphology and relation to rotator cuff pathology

We dissected 80 shoulders from 44 fresh cadavers to define variants of the coracoacromial ligament and their relationship to rotator cuff degeneration. The shapes and the geometric data of the ligaments were investigated, and the rotator cuffs of the cadavers were evaluated macroscopically. Five main types of coracoacromial ligaments were found: Y-shaped, broad band, quadrangular, V-shaped, and multiple-banded. The Y-shaped ligament was the most frequent type, with a frequency of 41.3%, and the V-shaped ligament (11.2%) has not been previously reported. Of the cadavers that were dissected bilaterally, 64% showed the same type of ligament. There was no statistical significance between rotator cuff degeneration and the type or geometric measurement of the ligament. However, the coracoacromial ligaments with more than 1 bundle showed significant association with rotator cuff degeneration with a longer lateral border and larger coracoid insertion.