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.     

Anatomy of the coracoacromial veil

The coracoacromial (CA) ligament plays an important role in the stability of the shoulder joint by limiting superior translation of the glenohumeral joint. This ligament is further divided into anterolateral and posteromedial bands. Attached to the CA ligament, a supportive structure was noted in some previous studies. The purpose of this study was to learn more about the anatomy of this structure. Twenty-eight shoulders were obtained. Deltoid and trapezius muscles were removed without damaging the rotator cuff and coracoacromial arch. The CA ligament was dissected further to reveal two constituent bands, an anterolateral and a posteromedial band. A connective tissue structure was noted between the posteromedial band, CA ligament, and rotator interval capsule. This structure was oriented as an L-shaped curtain, which the authors termed the "coracoacromial veil." Anatomical position of this veil provides a stabilizing link between the CA ligament and the rotator interval capsule. This structure potentially limits inferior translation of the glenohumeral joint.     

Degenerated coracoacromial ligament in shoulders with rotator cuff tears shows higher elastic modulus: measurement with scanning acoustic microscopy

Purpose  The purpose of this study was to determine the elasticity of the coracoacromial ligament in shoulders with and without rotator cuff tears. Methods  The coracoacromial ligaments from 20 cadaveric shoulders (average patient age 79.5 years; 8 men, 12 women) were divided into six portions — three portions (acromial, central, and coracoid) in two layers (superficial and deep). A total of 120 samples were studied. First, the samples were classified by the collagen fiber orientation into three degeneration patterns: wavy, straight, irregular. For each pattern, the tissue sound speed, which shows a positive correlation with elasticity, was measured with scanning acoustic microscopy. Next, the samples were divided into three groups: 60 samples from shoulders with rotator cuff tears (RCT group), 30 samples from shoulders with an intact rotator cuff and a subacromial spur (spur group), and 30 samples from shoulders with an intact rotator cuff without a subacromial spur (control group). All shoulders with rotator cuff tears had subacromial spurs. The tissue sound speed and the histological findings were compared among the groups. Results  The sound speeds in the wavy, straight, and irregular patterns were 1592 ± 17.2 m/s (mean ± SD), 1626 ± 28.0 m/s, and 1607 ± 29.8 m/s, respectively (P < 0.0001). The sound speed in the straight pattern was higher than that in the wavy pattern (P < 0.0001), and that in the irregular pattern was lower than that in the straight pattern (P = 0.0023). The RCT group and the spur group had more straight patterns (P = 0.0002) and fewer wavy patterns (P < 0.0001) than did the control group. Significant differences in the sound speed were observed between the groups (P < 0.0001): 1596 ± 19.1 m/s in the control group, 1630 ± 31.5 m/s in the spur group, 1612 ± 28.6 m/s in the RCT group. Conclusions  The coracoacromial ligament in shoulders with rotator cuff tears shows higher elastic modulus than in age-matched normal shoulders due to degeneration of the ligament.     

Biomechanics of coracoacromial arch modification

Although the biomechanics of the coracoacromial arch and coracoacromial ligament (CAL) morphology are well studied, to our knowledge, the biomechanics of the coracoacromial arch after CAL resection and medial reattachment have not yet been studied. The purpose of this report is to examine the biomechanical consequences of coracoacromial arch alteration and subsequent reconstruction in cadaveric specimens. Anterosuperior humeral head translation was measured after the application of an anterosuperior 150-N load under 5 sequential scenarios: (1) intact CAL, (2) subperiosteal CAL release, (3) standard acromioplasty, (4) CAL reconstruction, and (5) modified Neer acromioplasty. A significant decrease in anterosuperior migration was found after CAL reconstruction compared with both anterior acromioplasty (P = .038) and modified Neer acromioplasty (P = .01). Thus, in patients with massive rotator cuff tears, reconstruction of the CAL may provide the necessary stabilizing force to prevent excessive anterosuperior translation and possible humeral head escape from the coracoacromial arch.     

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 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.     

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.     

Coracoacromial ligament release for shoulder impingement syndrome using the Universal Subcutaneous Endoscope system.

We developed a new operative procedure of coracoacromial ligament release for shoulder impingement syndrome. The operative procedure was confirmed by cadaveric studies and applied to clinical cases in 40 shoulders of 37 patients who suffered from shoulder impingement without bony abnormalities. The subacromial space was observed under local anesthesia using the Universal Subcutaneous Endoscope (USE) system on an outpatient basis. A popping phenomenon was observed between the coracoacromial ligament and the greater tuberosity of the humerus, which was covered by the rotator cuff, and the coracoacromial ligament was resected with a rongeur under endoscopic visualization in all shoulders. Resection of the coracoacromial ligament relieved the impingement and clinical signs, as in open or arthroscopic resection of the coracoacromial ligament. Resection of the coracoacromial ligament using the USE system is a safe and less-stressful surgical invasion than open or standard arthroscopic resection of the coracoacromial ligament.     

Endoscopic management of shoulder pain in long-term haemodialysis patients

In 48 shoulders of 29 patients receiving long-term haemodialysis and complaining of intolerable shoulder pain, endoscopic resection of the coracoacromial ligament was performed under local anaesthesia on an outpatient basis, using the Universal Subcutaneous Endoscope system. Predominant endoscopic findings were proliferation of the subacromial bursae and popping between the coracoacromial ligament and the rotator cuff. Amyloid originating from beta 2 microglobulin (beta 2-M) was demonstrated in 87% of the resected coracoacromial ligaments and 86% of the subacromial bursae. Resection of the coracoacromial ligament relieved the shoulder pain in all patients.     

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 relationship between the orientation of the glenoid and tears of the rotator cuff

Our aim was to determine the most repeatable three-dimensional measurement of glenoid orientation and to compare it between shoulders with intact and torn rotator cuffs. Our null hypothesis was that glenoid orientation in the scapulae of shoulders with a full-thickness tear of the rotator cuff was the same as that in shoulders with an intact rotator cuff. We studied 24 shoulders in cadavers, 12 with an intact rotator cuff and 12 with a full-thickness tear. Two different observers used a three-dimensional digitising system to measure glenoid orientation in the scapular plane (ie glenoid inclination) using six different techniques. Glenoid version was also measured. The overall precision of the measurements revealed an error of less than 0.6 degrees. Intraobserver reliability (correlation coefficients of 0.990 and 0.984 for each observer) and interobserver reliability (correlation coefficient of 0.985) were highest for measurement of glenoid inclination based on the angle obtained from a line connecting the superior and inferior points of the glenoid and that connecting the most superior point of the glenoid and the most superior point on the body of the scapula. There were no differences in glenoid inclination (p = 0.34) or glenoid version (p = 0.12) in scapulae from shoulders with an intact rotator cuff and those with a full-thickness tear. Abnormal glenoid orientation was not present in shoulders with a torn rotator cuff.     

Stress distribution patterns at the coracoacromial arch in rotator cuff tear measured by computed tomography osteoabsorptiometry.

When a rotator cuff tear occurs, forces compressing the humeral head toward the glenoid are disturbed, and the kinematics of the glenohumeral joint change. Therefore, stress distributions at the coracoacromial arch in cuff tear shoulders should differ from those in normal shoulders. To investigate this hypothesis, we studied stress distribution patterns at the coracoacromial arch in normal and cuff tear shoulders using a computed tomography (CT) osteoabsorptiometry method, in which bone density correlates directly with long-term physiologic loading. Eight normal subjects and 11 patients with cuff tear were examined. The stress distributions at the undersurface of the acromion and the posterolateral surface of the coracoid process differed markedly between normal and cuff tear shoulders. In cuff tear shoulders, a high-density area was located at the anterior or the anterolateral part of the undersurface of the acromion, while it was located at the posterior part in all but one normal shoulder. Additionally, a high-density area was located at the superior or the lateral part of the coracoid process in most of the cuff tear shoulders; on the other hand, it was located at the base in all but one normal shoulder. We believe that the differences in stress distribution patterns are due to impingement at the coracoacromial arch in cuff tear shoulders. CT osteoabsorptiometry can provide useful information in performing coracoacromial arch decompression for cuff tear shoulders.     

Shoulder hemiarthroplasty for glenohumeral arthritis associated with severe rotator cuff deficiency.

BACKGROUND: Hemiarthroplasty for the treatment of shoulders with glenohumeral arthritis and severe rotator cuff deficiency has been reported to provide reasonable clinical results. The purposes of this study were to determine the clinical and radiographic results of hemiarthroplasty for this condition and to identify pathological and technical factors that may influence its outcome. METHODS: Thirty patients (thirty-three shoulders) managed with hemiarthroplasty because of glenohumeral arthritis and a massive, irreparable tear of the rotator cuff were followed for an average of five years (range, two to eleven years). Eight shoulders had undergone a prior acromioplasty and resection of the coracoacromial ligament. A small prosthetic head was used in three shoulders; a medium head, in twenty-six; and a large head, in four. Clinical results were graded according to the limited-goals criteria of Neer et al. RESULTS: The mean pain score decreased from 4.2 points preoperatively to 2.2 points at the time of the most recent follow-up (p = 0.0001). However, at the time of the most recent follow-up, nine shoulders (27%) had moderate pain at rest (four shoulders) or pain with activity (five shoulders). Mean active elevation improved from 72 degrees (range, 30 degrees to 150 degrees) to 91 degrees (range, 40 degrees to 165 degrees) (p = 0.008). Anterosuperior instability occurred in seven shoulders and was associated with a history of subacromial decompression (p = 0.04). The result was graded as successful for twenty-two shoulders (67%). CONCLUSIONS: Shoulder hemiarthroplasty provides marked pain relief in three-quarters of patients with glenohumeral arthritis and severe rotator cuff deficiency. It is a reconstructive option that provides durable results, but it may be complicated by instability and progressive bone loss.     

The influence of variations of the coracoacromial arch on the development of rotator cuff tears

In order to define the geometry of the coracoacromial arch in both its bony and soft parts and to bring it into relationship with rotator cuff tears, 54 cadaver shoulders (from subjects aged 47–90 years) were dissected And X-rayed (anteroposterior projection and supraspinatus outlet view). Partial rotator cuff tears were assessed additionally by transillumination and polarized microscopy. After transfixation of the coracoacromial arch with a polyurethane mould, sections were made along the coracoacromial ligament. The morphology of the acromion was described following the classification of Bigliani et al. [5]. Amongst other parameters, measurements were taken between the long axis of the scapula, the spina, and the acromion. In 19 of 22 cases, a traction osteophyte was associated with rotator cuff tears. In incomplete tears, spurs were completely encased within the ligament and did not impair the subacromial space. The number of rotator cuff tears was significantly increased in shoulders with curved acromia, flat acromial slope, and increased angle between the scapular plane and the spina (intact, mean 58°; tears, mean 47°). The morphology of the subacromial space was secondarily determined by this angle. In contrast to Bigliani et al. we were unable to find a hooked acromion. These results indicate that the combination of a flat and curved acromion or a position of the acromioclavicular joint above the cranial pole of the glenoid must be regarded as considerable risks for the development of rotator cuff tears. The concept of anterior acromioplasty is supported by our results.     

In-vitro reconstruction of massive rotator cuff ruptures with triceps tendon or coracoacromial ligament

The possibility of reconstructing a massive rotator cuff rupture with a free graft of the triceps tendon or the coracoacromial ligament was tested experimentally in an anatomical and biophysical cadaver investigation. After dissection of the rotator cuff, a section of the supraspinatus tendon was removed to simulate a defect in the cuff. In dissection of the grafts, a bony squama was incorporated by osteotomy. The rotator cuff was reconstructed by suturing the free grafts into the defect. In addition, the bony squama was refixed in a prepared bone groove in the greater tuberosity of the humerus. The tensile strength and the elasticity of the grafts were compared with that of the supraspinatus tendon in rupture tests. The mean value of the maximum load determined (FRm) was greatest for the triceps tendon (706.451 N), while very much lower values were found for the coracoacromial ligament (395.836 N) and the supraspinatus tendon (496.792 N). The mean value of the maximum elasticity (LAm) was lowest for the coracoacromial ligament (4.701%); the supraspinatus tendon (7.047%) and the triceps tendon (8.250%) showed very much greater elasticity. Received: 6 November 1999     

Anatomy of provocative tests for impingement syndrome of the shoulder

The purpose of this study was to describe the extra- and intra-articular anatomic relationships present during the Neer and Hawkins tests. Nine fresh-frozen cadaveric shoulders were positioned in the impingement position described by Neer (n = 5) or that described by Hawkins (n = 4), embedded in polyurethane, and studied with the use of a cross-sectional technique. All shoulders placed in the Neer position demonstrated soft tissue contact with the medial acromion and contact between the articular surface of the rotator cuff tendons and the anterosuperior glenoid rim. Shoulders placed in the Hawkins position demonstrated consistent contact between soft tissues and the coracoacromial ligament. In all Hawkins positioned shoulders, contact between the articular surface of the rotator cuff tendons and the anterosuperior glenoid was observed. The subscapularis tendon was deformed by the coracoid in 1 of the Hawkins positioned specimens. Although factors inherent to human subjects such as edema and muscle tone may influence the anatomy, these provocative tests for subacromial impingement appear to elicit contact consistent with impingement.     

Augmented subscapularis muscle transposition for rotator cuff repair during shoulder arthroplasty in patients with rheumatoid arthritis

The effectiveness of rotator cuff repair by augmented subscapularis transposition via the Leeds-Keio artificial ligament was evaluated in patients with rheumatoid arthritis undergoing total shoulder arthroplasty. The minimum follow-up period was 2 years. Final clinical scores (Hospital for Special Surgery scoring system) and the incidence of radiolucency and upward migration of shoulder components in 20 shoulders with rotator cuff repair by augmented subscapularis transposition were superior to those of 19 shoulders with cuff repair by subscapularis transposition alone and similar to those of 22 shoulders with intact rotator cuffs. In shoulders with augmented subscapularis transposition and intact cuffs, clinical scores continued to improve even after the first postoperative year. Our augmented subscapularis transposition did not increase postoperative complications. We conclude that cuff repair by augmented subscapularis transposition is an acceptable alternative for repairing a supraspinatus or supraspinatus and infraspinatus rotator cuff defect in rheumatoid arthritis patients undergoing total shoulder arthroplasty.     

关节镜下微创治疗肩袖钙化性肌腱炎

目的 探讨关节镜下微创钙化灶清除保留喙肩韧带预防性肩峰成形术治疗肩袖钙化性肌腱炎的适应证、手术方法及疗效.方法 2006年1月至2011年6月间采用肩关节镜下手术治疗肩袖钙化性肌腱炎12例,男3例,女9例;左肩5例,右肩7例;年龄32～72岁,平均54.6岁;病程3个月～2.5年,平均12个月.术前对患者肩关节功能按照加利福尼亚大学洛杉矶分校(universityofCalifornia at Los Angeles,UCLA)评分法进行评估,平均(16.14±2.10)分.本组患者常规进行预防性肩峰成形术.对于本身存在肩峰下骨赘的患者充分去除增生骨质,而对于无明显骨赘的患者则仅做轻度的肩峰成形,去除2 mm左右的骨质,并且保护喙肩韧带完整,从而保护了肩关节上方的被动稳定性结构.对4例钙化灶特别巨大、在彻底清除病灶及被钙化灶侵蚀和破坏的肩袖组织后,评估肩袖缺损深度超过肌腱厚度的50％者使用了锚钉行肩袖修补术.结果 术后随访6～25个月,平均16.4个月.术后疼痛程度及功能评分均有显著提高.肩关节活动范围明显改善.对手术前后UCLA各项进行配对t检验,两组差异有统计学意义(t=37.08,P＜0.01).结论 关节镜下钙化灶清除及保留喙肩韧带的预防性肩峰成形术,是治疗经保守治疗无效的肩袖钙化性肌腱炎患者一种安全有效的方法,具有损伤小、恢复快的优点.     

Acromial spur formation in patients with rotator cuff tears

In this study we analyzed the acromial spurs of 15 patients with impingement syndrome undergoing open rotator cuff repair. Mineral apposition analysis and quantitative cytochemical techniques for glucose-6-phosphate dehydrogenase (G6PD) activity (pentose phosphate pathway), alkaline phosphatase (ALP) activity (osteoblast activity), and tartrate-resistant acid phosphatase (TRAP) activity (osteoclast phenotype) were used to examine the distribution and level of activity of selected marker enzymes within the acromial spur insertion into the coracoacromial ligament in order to establish whether local behavior of bone cells is consistent with the proposed secondary development of the acromial spur. Our results indicate that G6PD and ALP activity was higher in osteoblasts on the inferior surface compared with the superior surface of the acromial spur in all patients (P <.001). This area correlated to the most intense area of mineral apposition shown by dual tetracycline labeling. TRAP activity revealed a heterogeneous distribution within the samples. A greater G6PD activity per cell (mean increase of 87%) was seen at the tip compared with that in post- and pre-tip zones within the coronal plane (P <.0002). The qualitative and quantitative enzyme analyses show that the acromial insertion of the coracoacromial ligament is actively involved in bone turnover. The spatial distribution patterns of metabolically active bone-forming osteoblastic cells compared with a heterogeneous distribution of TRAP-positive osteoclasts provide evidence of bone remodeling consistent with the morphologic contours of the acromial enthesis. The sites of oxytetracycline labeling appear to correlate with the sites of high ALP and G6PD activity, which supports the concept of spur formation being a secondary phenomenon in the presence of established rotator cuff tears.     

Biomechanical comparison of reconstruction techniques for disruption of the acromioclavicular and coracoclavicular ligaments

Injuries to the acromioclavicular joint are common. For selected injuries, operative reconstruction is recommended. The purpose of the current study was to compare three reconstruction procedures: (1) nine strands of woven polydioxanonsulphate (PDS II) suture passed through the clavicle and around the coracoid; (2) procedure No. 1 with 50% of the coracoacromioclavicular ligament placed through 2 clavicular drill holes; (3) No. 5 Merselene tape passed through 2 drill holes in the clavicle and acromion, with 50% of the coracoacromial ligament transferred to the clavicle. Fourteen fresh frozen human shoulders were tested using a 6 degree-of-freedom testing device. The intact shoulder showed significantly less displacement than any of the reconstructions. Merselene tape plus ligament showed the largest displacement, and PDS II braid plus ligament showed the least displacement. None of the procedures reconstituted acromioclavicular joint stiffness to intact state levels, though improved acromioclavicular joint stiffness was noted with a PDS braid plus ligament.