Humeral attachment of the supraspinatus and infraspinatus tendons: an anatomic study

We investigated the anatomic relationship of the supraspinatus (SSP) and infraspinatus (ISP) tendons to the three facets of the greater tuberosity. After removing the superficial layer of the cuff to expose the tendon fibers in 10 embalmed shoulders, the cuff tendon attachment to the facets was examined, and the location of attachment was measured in reference to (1) the anterior margin of the greater tuberosity and (2) the superior margin of the sulcus (anatomic neck without cartilage). The SSP tendon attached to the superior facet and the superior half of the middle facet. The ISP tendon attached to the entire middle facet, covering a portion of the SSP tendon. Thus, the anterior half of the superior cuff tendon (12.6 ± 1.1 mm) was composed of only the SSP tendon, whereas the posterior half (9.8 ± 3.2 mm) was composed of both the SSP and ISP tendons. The sulcus was located not at the SSP-ISP interval but slightly posterior to the posterior margin of the SSP tendon (4.3 ± 2.4 mm). We conclude that (1) there is an overlap between the SSP and ISP tendons identifiable by the facets or the distance from the anterior greater tuberosity and (2) the sulcus is located slightly posterior to the posterior margin of the SSP tendon.Arthroscopy 1998 Apr;14(3):302-6     

Anatomy and dimensions of rotator cuff insertions

The purpose of this study was to devise and implement an accurate and reproducible method of measuring the area and dimensions of the rotator cuff tendon insertions and their distance from the articular surface. Twenty fresh-frozen cadaveric upper-extremity specimens were divided into 2 groups of 10. In group 1 the specimens were dissected, leaving only the most distal rotator cuff tendons attached to the humerus. The periphery of the insertion onto the greater tuberosity was marked at 3-mm intervals. The specimens were then mounted onto a custom jig, and the insertion was mapped by a 3-space digitizer. In group 2 the specimens were prepared by removing all tissues except the rotator cuff muscles and tendons and the joint capsule. The interval between the muscles of the rotator cuff was identified and marked. The rotator cuff muscles and tendons were then removed, leaving only the most distal tendons attached to the tuberosities. The periphery of the individual cuff insertions was then marked as in group 1 and mapped in the same fashion. The articular margin also was marked at similar intervals and mapped with the same technique. The area of insertion of the 3 tendons on the greater tuberosity averaged 6.24 cm(2) (SD, 2.04 cm(2)) in group 1. The mean minimum transverse dimension across the cuff insertion occurred in the mid portion of the supraspinatus, with a mean distance of 14.7 mm (SD, 3.22 mm). In group 2 the mean area of insertion of the supraspinatus was 1.55 cm(2) (range, 0.68-2.64 cm(2); SD, 0.66 cm(2)) and the mean area of insertion for the infraspinatus was 1.76 cm(2) (range, 1.23-2.53 cm(2); SD, 0.40 cm(2)). The distance from the articular margin to the most medial rotator cuff fibers was less than 1 mm along the anterior-most 2.1 cm of the cuff insertion onto the greater tuberosity. No correlation could be made between humeral head dimension and the dimensions of the rotator cuff insertions. The mean minimum medial-to-lateral distance across the rotator cuff insertion was sizeable, at 14.7 mm. This represents the minimum possible distance, as the mathematical calculation to determine the dimensions used a perpendicular measurement. The rotator cuff inserts very closely to the articular margin along the anterior 2.1 cm of the greater tuberosity. These anatomic measurements may be useful in evaluating and reattaching the rotator cuff to the humerus.     

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.     

Electromyographic evaluation after primary repair of massive rotator cuff tears

Anatomic dissections have suggested that mobilization of the supraspinatus and infraspinatus tendons greater than 1 cm may cause suprascapular nerve injury. This study evaluated rotator cuff function by use of electromyographic (EMG) analysis after primary repair of massive tears in 9 patients. All subjects had massive rotator cuff tears involving at least the entire supraspinatus and entire infraspinatus tendons. Rotator cuff advancement averaged 2.5 cm (range, 2.0-3.5 cm). No EMG evidence of suprascapular nerve injury was found postoperatively. The UCLA shoulder score improved from a preoperative mean of 11 to a postoperative mean of 28. There was 1 excellent, 6 good, 1 fair, and 1 poor result. The poor result was due to a documented failed repair. The EMG results suggest that mobilization and advancement of the rotator cuff up to 3.5 cm during primary repair may be performed safely without as much risk to the suprascapular nerve as anatomic studies would suggest.     

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.     

A quantitative histological study of the vascularity of the rotator cuff tendon.

Previous perfusion studies of the rotator cuff have demonstrated an area of hypovascularity in the distal part of the supraspinatus tendon. This has been implicated in the pathogenesis of its rupture. We performed a quantitative histological analysis of the vascularity of the tendons of supraspinatus and infraspinatus. Vessel number, size and the percentage of the tendon occupied by vessels were measured at 5 mm intervals from the humeral insertions to the muscle bellies. Both tendons were hypovascular in their distal 15 mm. No significant difference was demonstrated between the vascularity of supraspinatus and infraspinatus. We conclude that factors other than vascularity are important in the pathogenesis of supraspinatus rupture.     

Occult fractures of the greater tuberosity of the humerus

We studied the highest reported number of patients with occult fracture of the greater tuberosity of the humerus and we analysed why fracture was not diagnosed, shoulder function and prevalence of eventually associated rotator cuff tear (RCT). Twenty-four patients with a missed fracture of the greater tuberosity underwent MR study for a suspect RCT. We evaluated shoulder function and self-assessed comfort with the Constant score (CS) and Simple Shoulder Test (SST). Nine patients showed evidence of cuff tendinosis, 11 of partial (p) RCT (2: subscapularis; 6: supraspinatus and 3: supraspinatus and infraspinatus). All patients with pRCT were older than 40. Initially, the mean CS and SST were 54% and 5/12; at follow-up, values increased to 36% and 5 points. MR should be performed in patients apparently negative for fracture but with painful shoulders and decreased ROM. Of our patients, 45.8% had pRCT; nevertheless function recovery was verified in 16 weeks.     

Begutachtung des Rotatorenschadens

The key to analyzing defects and tears in the rotator cuff is a profound knowledge of the anatomical structures and the resulting biomechanics. Defects of the rotator cuff are very frequent shoulder pathologies in the older population. Due to insurance requirements expert opinions have to differentiate between defects as a result of degenerative processes and tears caused through trauma. This article gives some advice for this decision. The rotator cuff is a tendon plate of four muscles inserting on the humeral head that works as a twin force coupling. The tendons of the supraspinatus and the infraspinatus muscles act as a cable system with two anchor points, comparable to a suspension bridge. The function of the delta muscle is particularly supported by the supraspinatus. Therefore, injuries of the central rotator cuff will affect the rotator cable system and the delta muscle. If this cannot be shown, there has to be substantial doubt about any trauma or primary injury. The medical assessment of rotator cuff injuries requires an accurate clinical and radiological diagnosis.     

Biomechanical effect of patch graft for large rotator cuff tears: a cadaver study

It is not possible for some rotator cuff tears to be repaired because of a large defect associated with muscle retraction. The purpose of the current study was to investigate the use of a synthetic patch graft to restore abduction force transmission in the glenohumeral joint with a rotator cuff defect. Shoulders from cadavers (n = 10) were fixed in the hanging arm and in neutral rotation, and loading was applied to the rotator cuff tendons and middle deltoid. After a simulated supraspinatus tendon defect and retraction, a patch graft was inserted into the defect and the effects of reattachment to the greater tuberosity, narrowing of the defect by using a smaller graft, and anterior graft attachment (rotator interval tissue versus subscapularis) were investigated. Abduction torque generation was measured and normalized to the intact condition. Compared with torque generation after creation of a supraspinatus defect (61% of normal torque), abduction torque increased with a graft between the infraspinatus and either the rotator interval (68% of normal) or subscapularis (80% of normal). The optimum grafting technique for abduction torque restoration occurred with a reduced size patch connected anteriorly to the subscapularis and sutured to the greater tuberosity (107% of normal). The patch graft acts to redirect force transmission, thereby providing a potential treatment option for otherwise irreparable defects. These same principles can be applied when tendon transfers are used to reconstruct large or massive cuff tears.     

Editorial Commentary: Superior Capsule Reconstruction: Acellular Allograft at 45° of Glenohumeral Abduction Improves Glenohumeral Stability,but Fascia Lata Autograft Remains Superior

Originally, fascia lata autograft was used for superior capsule reconstruction (SCR) to restore glenohumeral stability in irreparable rotator cuff tears. Consistently excellent clinical outcomes with low graft tear rates have been reported, without repair of tears in the supraspinatus and infraspinatus tendons. On the basis of our experience and studies published in the 15 years since the first SCR using fascia lata autograft in 2007, we can say that this technique is the gold standard. SCR using fascia lata autograft can cover all irreparable rotator cuff tears (Hamada grade 1-3; although the indication for SCR using other grafts, including dermal allograft, biceps, and hamstrings, is only Hamada grade 1 or 2); creates excellent clinical outcomes with low graft tear rates in short-term, long-term, and multicenter studies; regenerates the fibrocartilaginous insertions at both the greater tuberosity and superior glenoid according to histological study; and enables complete restoration of shoulder stability and subacromial contact pressure in cadaveric biomechanical studies.In some countries, dermal allograft is preferred for SCR. However, high rates of graft tear and complications have been reported after SCR using dermal allografts, even in limited indications of irreparable rotator cuff tears (Hamada grade 1 or 2). This high failure rate results from the lack of stiffness and thickness of the dermal allograft. Dermal allografts in SCR can be elongated by 15% after only a couple of physiological shoulder movements, whereas fascia lata graft cannot. This 15% graft elongation, which creates less glenohumeral stability and high graft tear after SCR, is a fatal problem of dermal allograft for SCR in irreparable rotator cuff tears. Current research suggests that SCR using dermal allografts is not strongly recommended for the treatment of irreparable rotator cuff tears. Dermal allograft probably should be used only for augmentation of rotator cuff complete repair.     

Variation in external rotation moment arms among subregions of supraspinatus, infraspinatus, and teres minor muscles.

A rotator cuff tear causes morphologic changes in rotator cuff muscles and tendons and reduced shoulder strength. The mechanisms by which these changes affect joint strength are not understood. This study's purpose was to empirically determine rotation moment arms for subregions of supraspinatus, infraspinatus, and for teres minor, and to test the hypothesis that subregions of the cuff tendons increase their effective moment arms through connections to other subregions. Tendon excursions were measured for full ranges of rotation on 10 independent glenohumeral specimens with the humerus abducted in the scapular plane at 10 and 60 degrees . Supraspinatus and infraspinatus tendons were divided into equal width subregions. Two conditions were tested: tendon divided to the musculotendinous junction, and tendon divided to the insertion on the humerus. Moment arms were determined from tendon excursion via the principle of virtual work. Moment arms for the infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly greater when the tendon was only divided to the musculotendinous junction versus division to the humeral head. Moment arms across subregions of infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly different. A difference in teres minor moment arm was not found for the two cuff tendon conditions. Moment arm differences between muscle subregions and for tendon division conditions have clinical implications. Interaction between cuff regions could explain why some subjects retain strength after a small cuff tear. This finding helps explain why a partial cuff repair may be beneficial when a complete repair is not possible. Data presented here can help differentiate between cuff tear cases that would benefit from cuff repair and cases for which cuff repair might not be as favorable.     

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     

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.     

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。     

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     

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.     

Glenoid cartilage mechanical properties decrease after rotator cuff tears in a rat model

Rotator cuff repairs are commonly performed to reduce pain and restore function. Tears are also treated successfully without surgical intervention; however, the effect that a torn tendon has on the glenohumeral cartilage remains unknown. Clinically, a correlation between massive rotator cuff tears and glenohumeral arthritis has often been observed. This may be due to a disruption in the balance of forces at the shoulder, resulting in migration of the humeral head and subsequently, abnormal loading of the glenoid. Our lab previously demonstrated changes in ambulation and intact tendon mechanical properties following supraspinatus and infraspinatus rotator cuff tendon tears in a rat model. Therefore, the purpose of this study was to investigate the effects of supraspinatus and infraspinatus rotator cuff tears on the glenoid cartilage. Nine rats underwent unilateral detachment of the supraspinatus and infraspinatus tendons and were sacrificed after 4 weeks. Cartilage thickness significantly decreased in the antero‐inferior region of injured shoulders. In addition, equilibrium elastic modulus significantly decreased in the center, antero‐superior, antero‐inferior, and superior regions. These results suggest that altered loading after rotator cuff injury may lead to damage to the joint with significant pain and dysfunction. Clinically, understanding the mechanical processes involved with joint damage will allow physicians to better advise patients. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1435–1439, 2012     

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     

Humeral head cysts: association with rotator cuff tears and age

The objective of this study was to retrospectively evaluate the prevalence of the cystic changes at rotator cuff footprint on proximal humeral tuberosities and investigate their relationship with rotator cuff tears and patient age. Magnetic resonance (MR) images of 657 patients who underwent shoulder arthroscopy for treatment of rotator cuff disorders were reviewed to localize the cystic changes at anterior (supraspinatus insertion) and posterior (infraspinatus insertion) aspects of greater tuberosity (GT) and lesser tuberosity (subscapularis insertion). Preoperative MR reports as well as cyst size and locations on MR images were correlated with arthroscopic records of rotator cuff pathology (tear type, size, location and tendon involvement) and patient age. The prevalence of cystic changes was 9.1 % (60 patients) in the study population. Anterior GT cysts were found in 56 % of patients and were strongly associated with full-thickness (p < .001) and articular-sided partial-thickness rotator cuff tears (p = .02). Posterior GT and lesser tuberosity cysts were found in 27 and 17 % of patients, respectively, and were not significantly related to rotator cuff tears, although there was an increased trend of posterior cysts in patients with infraspinatus tears (p = .09). A significant relation was found between patient age and the cyst size (p = .01), while none of the cyst localizations were statistically related to age. Anterior GT cysts were more common in this patient group and demonstrated a strong association with rotator cuff disorders regardless of age. Posterior GT and lesser tuberosity cysts were less common and showed no association with rotator cuff pathology or patient age.