Anatomy of the posterior rotator interval: implications for cuff mobilization

Release of the posterior rotator interval between the supraspinatus and infraspinatus tendons may be necessary to obtain appropriate mobilization for an anatomic rotator cuff repair. Ten cadaver shoulders were dissected to expose the region between the infraspinatus and supraspinatus from the spinoglenoid notch to the greater tuberosity. Measurements were made from the spinoglenoid notch to the glenoid rim, the glenoid rim to the confluence of the supraspinatus and infraspinatus musculotendinous junction, and from the confluence of the tendons to the insertion on the humerus. The histologic features of the posterior rotator interval were examined. The posterior rotator interval is a clear structure, consisting of the glenohumeral capsule medially, which fuses with the supraspinatus and infraspinatus tendons laterally. The average length of the posterior rotator interval was 77.8 mm which includes the distance from the spinoglenoid notch to the glenoid rim (25 mm; standard deviation, 2.89 mm; range, 21-28 mm), from the glenoid to the tendon confluence (25 mm; standard deviation, 1.95 mm; range, 21-28 mm), and from the tendon confluence to insertion (28 mm; standard deviation, 2.36 mm; range, 24-31 mm). Release of the posterior rotator interval can be important to realign the supraspinatus tendon if it is retracted and scarred at its posterior edge.     

Atrophy of the rotator cuff muscles and site of cuff tears

We determined the relationship between the site of rotator cuff tears and atrophy of the cuff muscles. 28 shoulders (28 patients) had rotator cuff tears: 19 isolated tears of the supraspinatus tendon (isolatedtear group) and 9 combined tears of the supraspinatus and infraspinatus tendons (combined-tear group). The cross-sectional area of the subscapularis, supraspinatus, the infraspinatus and teres minor muscles in the coronal oblique MR images were measured before and after surgery. Although we found no difference in tear size, the cross-sectional areas of the muscles were smaller in the combined-tear group than in the isolated-tear group. We conclude that atrophy of the supraspinatus and infraspinatus muscles also depends on the site of the tear.     

Atrophy of the rotator cuff muscles and site of cuff tears

We determined the relationship between the site of rotator cuff tears and atrophy of the cuff muscles. 28 shoulders (28 patients) had rotator cuff tears: 19 isolated tears of the supraspinatus tendon (isolated-tear group) and 9 combined tears of the supraspinatus and infraspinatus tendons (combined-tear group). The cross-sectional area of the subscapularis, supraspinatus, the infraspinatus and teres minor muscles in the coronal oblique MR images were measured before and after surgery. Although we found no difference in tear size, the cross-sectional areas of the muscles were smaller in the combined-tear group than in the isolated-tear group. We conclude that atrophy of the supraspinatus and infraspinatus muscles also depends on the site of the tear.     

Arthroscopic repair of full-thickness tears of the supraspinatus: does the tendon really heal?

BACKGROUND: Good functional results have been reported for arthroscopic repair of rotator cuff tears, but the rate of tendon-to-bone healing is still unknown. Our hypothesis was that arthroscopic repair of full-thickness supraspinatus tears achieves a rate of complete tendon healing equivalent to those reported in the literature with open or mini-open techniques. METHODS: Sixty-five consecutive shoulders with a chronic full-thickness supraspinatus tear were repaired arthroscopically in sixty-five patients with use of a tension-band suture technique. Patients ranged in age from twenty-nine to seventy-nine years. The average duration of follow-up was twenty-nine months. Fifty-one patients (fifty-one shoulders) had a computed tomographic arthrogram, and fourteen had a magnetic resonance imaging scan, performed between six months and three years after surgery. All patients were assessed with regard to function and the strength of the shoulder elevation. RESULTS: The rotator cuff was completely healed and watertight in forty-six (71%) of the sixty-five patients and was partially healed in three. Although the supraspinatus tendon did not heal to the tuberosity in sixteen shoulders, the size of the persistent defect was smaller than the initial tear in fifteen. Sixty-two of the sixty-five patients were satisfied with the result. The Constant score improved from an average (and standard deviation) of 51.6 +/- 10.6 points preoperatively to 83.8 +/- 10.3 points at the time of the last follow-up evaluation (p < 0.001), and the average University of California at Los Angeles score improved from 11.5 +/- 1.1 to 32.3 +/- 1.3 (p < 0.001). The average strength of the shoulder elevation was significantly better (p = 0.001) when the tendon had healed (7.3 +/- 2.9 kg) than when it had not (4.7 +/- 1.9 kg). Factors that were negatively associated with tendon healing were increasing age and associated delamination of the subscapularis or infraspinatus tendon. Only ten (43%) of twenty-three patients over the age of sixty-five years had completely healed tendons (p < 0.001). CONCLUSIONS: Arthroscopic repair of an isolated supraspinatus detachment commonly leads to complete tendon healing. The absence of healing of the repaired rotator cuff is associated with inferior strength. Patients over the age of sixty-five years (p = 0.001) and patients with associated delamination of the subscapularis and/or the infraspinatus (p = 0.02) have significantly lower rates of healing.     

Restoration of anterior–posterior rotator cuff force balance improves shoulder function in a rat model of chronic massive tears

The rotator cuff musculature imparts dynamic stability to the glenohumeral joint. In particular, the balance between the subscapularis anteriorly and the infraspinatus posteriorly, often referred to as the rotator cuff “force couple,” is critical for concavity compression and concentric rotation of the humeral head. Restoration of this anterior–posterior force balance after chronic, massive rotator cuff tears may allow for deltoid compensation, but no in vivo studies have quantitatively demonstrated an improvement in shoulder function. Our goal was to determine if restoring this balance of forces improves shoulder function after two‐tendon rotator cuff tears in a rat model. Forty‐eight rats underwent detachment of the supraspinatus and infraspinatus. After four weeks, rats were randomly assigned to three groups: no repair, infraspinatus repair, and two‐tendon repair. Quantitative ambulatory measures including medial/lateral forces, braking, propulsion, and step width were significantly different between the infraspinatus and no repair group and similar between the infraspinatus and two‐tendon repair groups at almost all time points. These results suggest that repairing the infraspinatus back to its insertion site without repair of the supraspinatus can improve shoulder function to a level similar to repairing both the infraspinatus and supraspinatus tendons. Clinically, a partial repair of the posterior cuff after a two‐tendon tear may be sufficient to restore adequate function. An in vivo model system for two‐tendon repair of massive rotator cuff tears is presented. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1028–1033, 2011     

关节镜下缝线桥技术治疗巨大肩袖撕裂的临床研究

目的探讨关节镜下缝线桥技术缝合巨大肩袖撕裂的临床疗效。 方法回顾分析2014年6月至2016年6月在广州市正骨医院收治并取得完整随访的38例采用关节镜下缝线桥技术修复的巨大肩袖撕裂患者的临床资料,排除无法取得随访、依从性差的患者,分析术前X线片、MRI检查,了解肩袖撕裂口大小、肩袖回缩程度、肌肉萎缩及脂肪浸润情况,应用SPSS 17.0统计学软件配对t检验对术前与术后半年随访时视觉模拟评分系统(VAS)评分和美国加州大学肩关节评分系统(UCLA)评分进行比较。 结果本组患者38例,男23例,女15例,平均年龄(66±6)岁,所有患者均获半年以上的随访,随访时间(12±5)月。所有患者在关节镜下均发现有2条或以上的肌腱撕裂,关节镜下见15例患者冈上肌腱和冈下肌腱撕裂,8例冈上肌、冈下肌和小圆肌腱撕裂,10例冈上肌腱、冈下肌腱撕裂和肩胛下肌腱撕裂,5例冈上肌腱和肩胛下肌腱撕裂。术前VAS评分为(6.7±1.6)分,术后6月随访时为(2.4±1.7)分,术前与术后6月随访的VAS评分差异均有统计学意义(t ＝10.123,P<0.01);术前UCLA评分为(7.9±1.2)分,术后6月随访时为(23.4±5.1)分,术前与术后6月随访的UCLA评分差异均有统计学意义(t ＝－18.979,P<0.01);术后的UCLA、VAS评分均明显升高。术后半年MR检查结果,5例患者出现小型再撕裂,裂口均<3 cm,术后再撕裂患者与无再撕裂患者的VAS评分和UCLA肩关节评分无明显统计学差异(P>0.05)。 结论关节镜下缝线桥技术修复巨大肩袖撕裂取得较好的短期疗效,是1种合理、有效的治疗方法。     

Rotator cuff rupture

The rotator cuff is the complex of four muscles that arise from the scapula; supscapularis, supraspinatus, infraspinatus and teres minor. The long head of the biceps tendon may be considered a functional part of the rotator cuff. The rotator cuff is key structure of the shoulder which gives dynamic stability and movements. Rotator cuff tears my occur as consequence of impingement syndrome or degenerative changes. Most tears occur in the supraspinatus tendon. The patients are usually older than 40 years. On clinical examination there is weakness of abducation and external rotation of the arm. Open or arthroscopic repair should be performed in active individuals.     

Effect of glenohumeral abduction angle on the mechanical interaction between the supraspinatus and infraspinatus tendons for the intact,partial‐thickness torn,and repaired supraspinatus tendon conditions

Rotator cuff tears are difficult to manage because of the structural and mechanical inhomogeneity of the supraspinatus tendon. Previously, we showed that with the arm at the side, the supraspinatus and infraspinatus tendons mechanically interact such that conditions that increase supraspinatus tendon strain, such as load or full‐thickness tears, also increase infraspinatus tendon strain. This suggests that the infraspinatus tendon may shield the supraspinatus tendon from further injury while becoming at increased risk of injury itself. In this study, the effect of glenohumeral abduction angle on the interaction between the two tendons was evaluated for supraspinatus tendon partial‐thickness tears and two repair techniques. Principal strains were quantified in both tendons for 0°, 30°, and 60° of glenohumeral abduction. Results showed that interaction between the two tendons is interrupted by an increase in abduction angle for all supraspinatus tendon conditions evaluated. Infraspinatus tendon strain was lower at 30° and 60° than at 0° abduction angle. In conclusion, interaction between the supraspinatus and infraspinatus tendons is interrupted with increase in abduction angle. Additionally, 30° abduction should be further evaluated for management of rotator cuff tears and repairs as it is the angle at which both supraspinatus and infraspinatus tendon strain is decreased. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:846–851, 2010     

Biomechanical comparison of effects of supraspinatus tendon detachments,tendon defects,and muscle retractions

BACKGROUND: Rotator cuff ruptures are frequently associated with loss of strength of the shoulder. However, the characteristics of the rotator cuff tear that are responsible for the loss of force generation and transmission have not yet been identified. The purpose of this study was to compare the effects of supraspinatus tendon detachments, tendon defects, and muscle retractions on in vitro force transmission by the rotator cuff to the humerus. METHODS: The rotator cuff tendons from ten cadaver shoulders were loaded proportionally to the respective cross-sectional areas of their muscles. A fiberglass rod was cemented into the medullary canal of the humerus and connected to a three-component load cell for the measurement of the forces transmitted by the rotator cuff to the humerus. This study was performed with the humerus in a hanging arm position and with various sizes of supraspinatus tendon detachments, tendon defects, and muscle retractions. RESULTS: Detachment or creation of a defect involving one-third or two-thirds of the supraspinatus tendon resulted in a minor reduction in the force transmitted by the rotator cuff (< or =5%), while detachment or creation of a defect involving the whole tendon resulted in a moderate reduction (11% and 17%, respectively). Simulated muscle retraction involving one-third, two-thirds, and the whole tendon resulted in losses of torque measuring 19%, 36%, and 58%, respectively. Side-to-side repair of the one-third and two-thirds defects nearly restored the force transmission capability, whereas a deficit remained after side-to-side repair following complete resection. CONCLUSIONS: Our results support the rotator cable concept and correspond to the clinical observation that patients with a small rupture of the rotator cuff may present without a loss of shoulder strength. Muscle retraction is potentially an important factor responsible for loss of shoulder strength following large rotator cuff ruptures. Clinical Relevance: Supraspinatus muscle retraction diminishes glenohumeral abduction torque significantly more than either a defect in the tendon or a simple detachment of the tendon from the tuberosity. In cases of irreparable defects, side-to-side repair may be worthwhile to restore muscle tension and the integrity of the rotator cable.     

The effect of infraspinatus disruption on glenohumeral torque and superior migration of the humeral head: a biomechanical study

Rotator cuff ruptures that extend into the infraspinatus tendon may cause dysfunction and superior migration of the humerus. The purpose of this study was to determine whether a threshold size of infraspinatus defect exists beyond which abduction torque generation decreases and superior migration of the humeral head increases. Glenohumeral abduction torque and superior humeral head translations were measured in hanging arms in neutral rotation in cadaver shoulders (n = 10). Loads were applied to the rotator cuff tendons and the middle deltoid. After sequential detachment of the infraspinatus, abduction torque progressively decreased. At three-fifths detachment, abduction torque was significantly lower than after supraspinatus release alone (52% vs 61%, P <.05). Superior translation after complete supraspinatus and infraspinatus detachment increased significantly (P <.05), but no intermediate threshold was detected. Therefore, the entire infraspinatus contributes to abduction torque generation and stabilizes the humeral head against superior subluxation. Even with a tear extending into the superior infraspinatus, the infraspinatus contributes abduction force generation across the glenohumeral joint.     

Clinical and structural results of open repair of an isolated one-tendon tear of the rotator cuff

BACKGROUND: The clinical outcomes of open rotator cuff repair are well established, but the structural results and their effect on clinical outcome are poorly known. We assessed the structural changes in the musculotendinous units after open rotator cuff repair and correlated these findings with the clinical outcome to establish a benchmark for future series. METHODS: Thirty-two consecutive standardized open repairs of a single tendon tear of the rotator cuff were analyzed in twenty-one men and eleven women with an average age of 59.0 years. The supraspinatus tendon was involved in twenty-two patients and the subscapularis tendon, in ten. The clinical outcome, including the Constant score, was assessed prospectively for all patients at an average of thirty-eight months postoperatively. The structural outcome was assessed on standardized magnetic resonance imaging scans. RESULTS: The mean overall subjective shoulder value was 82.8% of the value for a normal shoulder. On the average, the age and gender-adjusted Constant score increased from 63.9% preoperatively to 94.5% postoperatively (p < 0.0001); the score for pain, from 6.8 points to 13.2 points (p < 0.0001); and the score for activities of daily living, from 11.2 points to 17.9 points (p < 0.0001). The overall rerupture rate was 13% (four of the thirty-two shoulders). All reruptures were distinctly smaller than the original tear. Muscular atrophy or fatty infiltration did not significantly decrease after the tendon repair. In fact, fatty infiltration in the supraspinatus (p < 0.0053) and infraspinatus (p < 0.003) muscles increased significantly. CONCLUSIONS: Direct open repair of a complete, isolated tear of one tendon of the rotator cuff resulted in significant subjective and objective improvement and very high patient satisfaction. Successful direct repair was not associated with a decrease in preoperative muscular atrophy and was associated with increased fatty infiltration of the muscle.     

Mechanical properties of the long‐head of the biceps tendon are altered in the presence of rotator cuff tears in a rat model

Rotator cuff tears are disabling conditions that result in changes in joint loading and functional deficiencies. Clinically, damage to the long‐head of the biceps tendon has been found in conjunction with rotator cuff tears, and this damage is thought to increase with increasing tear size. Despite its importance, controversy exists regarding the optimal treatment for the biceps. An animal model of this condition would allow for controlled studies to investigate the etiology of this problem and potential treatment strategies. We created rotator cuff tears in the rat model by detaching single (supraspinatus) and multiple (supraspinatus + infraspinatus or supraspinatus + subscapularis) rotator cuff tendons and measured the mechanical properties along the length of the long‐head of the biceps tendon 4 and 8 weeks following injury. Cross‐sectional area of the biceps was increased in the presence of a single rotator cuff tendon tear (by ～150%), with a greater increase in the presence of a multiple rotator cuff tendon tear (by up to 220%). Modulus values decreased as much as 43 and 56% with one and two tendon tears, respectively. Also, multiple tendon tear conditions involving the infraspinatus in addition to the supraspinatus affected the biceps tendon more than those involving the subscapularis and supraspinatus. Finally, biceps tendon mechanical properties worsened over time in multiple rotator cuff tendon tears. Therefore, the rat model correlates well with clinical findings of biceps tendon pathology in the presence of rotator cuff tears, and can be used to evaluate etiology and treatment modalities. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:416–420, 2009     

Disruption of the anterior–posterior rotator cuff force balance alters joint function and leads to joint damage in a rat model

The rotator cuff assists in shoulder movement and provides dynamic stability to the glenohumeral joint. Specifically, the anterior–posterior (AP) force balance, provided by the subscapularis anteriorly and the infraspinatus and teres minor posteriorly, is critical for joint stability and concentric rotation of the humeral head on the glenoid. However, limited understanding exists of the consequences associated with disruption of the AP force balance (due to tears of both the supraspinatus and infraspinatus tendons) on joint function and joint damage. We investigated the effect of disrupting the APforce balance on joint function and joint damage in an overuse rat model. Twenty‐eight rats underwent 4 weeks of overuse to produce a tendinopathic condition and were then randomized into two surgical groups: Detachment of the supraspinatus only or detachment of the supraspinatus and infraspinatus tendons. Rats were then gradually returned to their overuse protocol. Quantitative ambulatory measures including medial/lateral, propulsion, braking, and vertical forces were significantly different between groups. Additionally, cartilage and adjacent tendon properties were significantly altered. These results identify joint imbalance as a mechanical mechanism for joint damage and demonstrate the importance of preserving rotator cuff balance when treating active cuff tear patients. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:638–644, 2014.     

The tension required at repair to reappose the supraspinatus tendon to bone rapidly increases after injury

Rotator cuff tears occur frequently and can cause significant pain and reduced shoulder function. A high percentage of patients are satisfied after surgical repair of rotator cuff tears, but a smaller percentage of patients with chronic tears continue to have pain and poor shoulder function. This may be partly attributable to an increase in the repair tension, the force required at repair to reappose the tendon to its original insertion site on the humerus. Increases in repair tension have been shown to occur for long-standing ruptures of the supraspinatus tendon, but the precise tension at various times after injury are unknown. Therefore, the objective of the current study was to determine the repair tension at various times after a rotator cuff tear. This was achieved by creating a full-thickness supraspinatus tendon tear in a rat model and measuring the mechanical characteristics of the musculotendinous unit at 0, 2, 4, 9, and 16 weeks after injury. The repair tension rapidly increased initially after injury followed by a progressive, but less dramatic, increase with additional time. These findings suggest that rotator cuff tears should be repaired early in the clinical setting. Future studies will investigate the effect of repair tension on tendon to bone healing after repair.     

Diagnosis and treatment of anterosuperior rotator cuff tears

Nineteen of 407 patients who underwent rotator cuff repair surgery over a 6-year period were found to have a tear of the subscapularis in combination with the supraspinatus and infraspinatus tendons. Nine of these patients had an unsuccessful prior surgery, which failed to recognize the extent of the subscapularis component. Surgical repair of the subscapularis tendon required a deltopectoral approach, and repair of the supraspinatus and infraspinatus components of the tear could only be accomplished through this approach in 4 patients. In the remaining 15, an extended superior approach was required to mobilize and repair the supraspinatus and infraspinatus tendons. In all cases, the biceps tendon was either torn or severely degenerated, requiring tenodesis. At a mean follow-up of 40 months (range 24 to 75 months), subjective results were excellent in 5 patients, good in 3, fair in 4, and poor in 7. The modified Constant score improved to a mean of 69% (range 23% to 130%), compared with a preoperative mean of 38% (range 23% to 100%). Physical findings positive for subscapularis insufficiency persisted in 14 of 19 patients. A significant correlation (P <.05) was found between a lower Constant score and duration of symptoms longer than 6 months as well as an appearance of severe fatty degeneration and atrophy of the subscapularis muscle on magnetic resonance imaging. We conclude that anterosuperior rotator cuff tears are an infrequent configuration that may require surgical repair through an extended approach combining deltopectoral mobilization of the subscapularis with transdeltoid mobilization of the supraspinatus and infraspinatus. Repair before 6 months of symptoms is associated with a better functional outcome and is the result of less involution of muscle and tendon tissue.     

Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy.

We investigated the structure of the myotendinous rotator cuff in thirty-two grossly intact cuffs from thirty fresh cadavera of subjects who had been seventeen to seventy-two years old at the time of death. We studied the gross anatomy of the capsule and ligaments of the cuff, as well as histological sections of the tendons of the subscapularis, supraspinatus, and infraspinatus muscles. The tendons were found to splay out and interdigitate to form a common, continuous insertion on the humerus. The biceps tendon was ensheathed by interwoven fibers derived from the subscapularis and supraspinatus tendons. The anterior margin and bursal surface of the supraspinatus tendon were enveloped by a thick sheet of fibrous tissue derived from the coracohumeral ligament. Fibers from the coracohumeral and glenohumeral ligaments were found concentrated in a plane between the capsule and the tendons of the cuff. Microscopically, in the region of the supraspinatus and infraspinatus tendons, the cuff was composed of five layers defined by the attachments and orientations of the fibrous elements in each of these layers.     

Clinical outcome after structural failure of rotator cuff repairs

BACKGROUND: The clinical outcome for patients with documented rerupture after open repair of one or more rotator cuff tendons is not well known. The purpose of this study was to evaluate the clinical outcomes of a consecutive series of rotator cuff reruptures after repair and to provide information concerning the advisability of rotator cuff repair in situations in which there may be a high probability of rerupture. METHODS: During prospective follow-up after rotator cuff repairs, we detected, with magnetic resonance imaging, structural failure of the repair in twenty patients, who had a mean age of fifty-nine years at the time of the rotator cuff repair. All patients were clinically examined for the purpose of this report at a mean of thirty-eight months. RESULTS: The reruptures invariably involved the originally torn tendon but were smaller than the original tear in sixteen of the twenty patients. Fatty degeneration of the supraspinatus and infraspinatus muscles, atrophy of the supraspinatus muscle, and glenohumeral osteoarthritis progressed significantly from the preoperative state (p < 0.05). At the time of the most recent follow-up, the subjective shoulder value averaged 75 percent of the value for a normal shoulder. Eleven patients were very satisfied with the result, six were satisfied, two were disappointed, and one was dissatisfied. The mean relative score according to the system of Constant and Murley had increased from 49 percent of the score for a normal shoulder preoperatively to 83 percent postoperatively (p = 0.0001). Pain had decreased significantly, and the ranges of active, pain-free forward elevation and abduction as well as the abduction strength had improved significantly (p < 0.05). The clinical outcome was significantly correlated with the size of the postoperative tear, the stage of postoperative fatty muscle degeneration of the infraspinatus and subscapularis, the postoperative acromiohumeral distance, and the degree of postoperative glenohumeral osteoarthritis (p < 0.05). CONCLUSIONS: This study documents that an attempt at rotator cuff repair significantly decreases pain (p = 0.0026) and significantly improves function (p = 0.0005) and strength (p = 0.0137) even if magnetic resonance imaging documents that the repair has failed. This finding suggests that the potential for rerupture should not be considered a formal contraindication to an attempt at repair if optimal functional recovery is the goal of treatment.     

Apoptosis in rotator cuff tendonopathy.

The aim of this study was to investigate the involvement of apoptosis (programmed cell death) in the pathogenesis of rotator cuff disorders. The edges of torn supraspinatus rotator cuff tendons were collected from patients with rotator cuff tear (n = 25). Samples of the intra-articular portion of subscapularis tendons were collected from patients without rotator cuff tear as control (n = 6). To minimize individual variance, we also collected six pairs of supraspinatus tendon and subscapularis tendon from six patients with rotator cuff tears. Apoptosis was detected by in situ DNA end labelling assay and DNA laddering assay. Immunohistochemical staining was performed to identify cells undergoing apoptosis. Control subscapularis tendon had normal morphology. Tendon from torn supraspinatus rotator cuff showed significant mucoid degeneration. Within the areas of degeneration, there were large numbers of apoptotic cells. The percentage of apoptotic cells in the degenerative rotator cuff (34%) was significantly higher than that in controls (13%) (p < 0.001). The excessive apoptosis detected in degenerative rotator cuff tissue was confirmed by DNA laddering assays. This is the first report of excessive apoptosis in degenerating rotator cuff tendon. Cells undergoing apoptosis in rotator cuff were mainly fibroblast-like cells. These finding indicate that apoptosis may play an important role in the pathogenesis of rotator cuff degeneration.     

Estimation of Total Collagen and Types I and III Collagen in Canine Rotator Cuff Tendons

The collagen composition of the supraspinatus, infraspinatus, and subscapularis tendons, which form part of the rotator cuff of the shoulder, was determined. Tendons were obtained from adult, male beagle dogs and total collagen was estimated by measurement of hydroxyproline. There was little variation in collagen content among the three major cuff tendons and the quantity approximated that cited in the literature for other tendons. However, the collagen content in the insertion zone of the supraspinatus tendon was significantly higher than in the tendon proper. NaCl fractionation of supraspinatus collagen indicated that type I was the predominant collagen but significant amounts of type III and possibly some type II and type V were also present. Interestingly, there appeared to be more type III collagen in the insertion zone than in the tendon proper, cyanogen bromide digestion and peptide mapping confirmed this finding. The differential collagen composition of the supraspinatus tendon may contribute to the high incidence of tear that is associated with this rotator cuff tendon. Received: 10 May 1996 / Accepted: 23 April 1997     

Rotator cuff assessment on imaging

The rotator cuff is a group of four muscles and tendons surrounding the shoulder joint providing it strength and stability. The rotator cuff consists of the subscapularis, supraspinatus, infraspinatus and teres minor. Many shoulder complaints are caused by rotator cuff pathology such as impingement syndrome, tendon tears and other diseases e.g. calcific tendonitis. Diagnosis starts with clinical history and physical examination, after which imaging is often used to help confirm clinical findings depending on the differential diagnosis. The aim of the article is to review the frequently used imaging modalities to assess the rotator cuff and cuff-related disease, specifically focusing on radiography, ultrasonography and magnetic resonance imaging. This article will outline the advantages and disadvantages for each modality and illustrate typical radiological findings of common rotator cuff pathologies.