Fibrocartilage at the entheses of the suprascapular (superior transverse scapular) ligament of man--a ligament spanning two regions of a single bone

Clinical and ultrasonographic enthesopathy in inflammatory rheumatic diseases : Is MASEI or only calcaneal enthesitis sufficient?

AIM

We aimed at investigating the ultrasonographic (US) and clinical prevalence of enthesopathy in patients with rheumatoid arthritis (RA), and axial spondyloarthropathy (SpA), as well as the correlation between this condition and disease activity, along with the quality of life.

METHODS

Included in the study were 30 axial SpA, 21 patients with RA, and 25 healthy cases. Bath Anklylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Quality of Life (ASQoL), Disease activity index  28 (DAS28), and Health Assessment Questionnaire (HAQ) were used for clinical evaluation, and enthesal pain was evaluated by VAS, whereas enthesitis US evaluation was performed by using the MAdrid Sonographic Enthesitis Index (MASEI). A total of 152 knees, ankles, and elbow regions of all patients and controls were examined by US.

RESULTS

Total scores of physical examination of enthesitis were 1.97 ± 2.68 in axial SpA, 2.43 ± 1.80 in RA, and 0.23 ± 0.12 in the control groups. No statistically significant difference was identified in the enthesitis examination between axial SpA and RA groups (p = 0.123). According to the MASEI, no significant difference was observed in quadriceps tendon enthesitis or in distal patellar ligament enthesitis between axial SpA and RA groups (MASEI 3, 4, 5: p = 0.993, p = 0.124, p = 0.652). Aside from those points, axial SpA patients had statistically higher enthesitis scores at all MASEI enthesitis points (p < 0.05). In the axial SpA group, a significant and positive correlation was identified between BASDAI scores and total scores of enthesitis physical examination and MASEI total scores (r = 0.739, p = 0.0001, r = 0.516, p = 0.002). A moderately significant correlation was identified between ASQoL total scores and MASEI total scores (r = 0.466, p = 0.006), but not between the HAQ total scores and MASEI total scores (r = 0.213, p = 0.065).

CONCLUSIONS

Compared to RA, US and clinical examination of enthesitis in patients with axial SpA should focus on the calcaneal enthesitis region. In axial SpA, ultrasonographic enthesitis is associated with impaired quality of life.

The prevalence and morphometric analysis of ossified superior transverse scapular ligaments in patients with rotator cuff tears

BACKGROUND

The prevalence of ossified superior transverse scapular ligaments (OSTSLs) in rotator cuff tears (RCTs) has not yet been determined. The purposes of this study were to evaluate the prevalence of OSTSLs in RCTs and to investigate the correlation between OSTSL morphology and supraspinatus muscle atrophy.

METHODS

We analyzed a total of 213 patients with RCTs for whom 3-dimensional (3D) computed tomography (CT) and magnetic resonance imaging were performed prior to arthroscopic procedures. The mean age of the patients was 59.73 ± 8.43 years, and 103 patients were men. OSTSLs were identified based on 3D CT findings. The correlations between OSTSLs and age, sex, and RCT size were analyzed. The horizontal and vertical diameters, area, and circumference of the suprascapular foramen were measured. By use of the occupation ratio calculated from magnetic resonance imaging results, supraspinatus muscle atrophy was evaluated.

RESULTS

Of 213 patients with RCTs, 22 (10.3%) had OSTSLs. OSTSLs were found at a rate of 15.5% (16 of 103) in men, higher than that in women (P = .016). The rate of OSTSLs increased with age (P = .003). RCT size was not correlated with the prevalence of OSTSLs. As the horizontal diameter and circumference of the suprascapular foramen increased, muscle atrophy progressed (P = .001 and P = .046, respectively).

CONCLUSION

One of ten patients with RCTs had OSTSLs; the rate of OSTSLs was higher among men and increased with age. For patients with RCTs preparing to undergo arthroscopic superior transverse ligament resection, preoperatively identifying OSTSLs through 3D CT would be useful for the resection.

The suprascapular notch narrows with aging: a preliminary solution of the old conjecture based on a 3D-CT evaluation

PURPOSE

The purpose of this study was to describe the morphology of the suprascapular notch in terms of age distribution. We hypothesized that the notch narrows with aging.

METHODS

Seven hundred and sixty consecutive patients (465 men and 295 women) scheduled for a shoulder surgery were retrospectively reviewed. A 3D-CT of the shoulder was taken to evaluate the shape of the notch according to the Rengachary classification. The six types of Rengachary classification were arranged into three major categories according to transverse scapular ligament ossification and notch size as follows: the wide notch (type 1 and type 2); the narrow notch (type 3 and type 4); and the ossified notch (type 5 and type 6). Comparisons between categories were done with a one-way analysis of variance.

RESULTS

There was a statistically significant difference among the three categories (P < .01): the narrow notch group (n = 442, 63.4 ± 12.8 years) and the ossified notch group (n = 66, 65.9 ± 10.6 years) were significantly older than the wide notch group (n = 252, 57.5 ± 17.8 years), respectively. In patients with Rengachary type 5 shoulders, ossification was dominant on the medial side of the notch in 37 of 39 shoulders (92.3 %).

CONCLUSION

The current study showed that morphological changes of the scapular notch are related to aging. The narrow notch and the ossified notch are seemed to be developed from the wide notch in terms of the ossification starting from the medial side.

MRI appearance of the superior transverse scapular ligament

OBJECTIVE

The superior transverse scapular ligament (STSL) forms the roof of the suprascapular notch, which is the most common location of entrapment of the suprascapular nerve, a cause of shoulder pain and weakness. The purpose of this study is to determine the frequency of visualization of the STSL on routine shoulder MRIs, to identify the sequences and imaging planes on which it is visualized most frequently, and to describe its typical MRI appearance, none of which have been previously addressed in the radiologic literature.

MATERIALS AND METHODS

One hundred twenty-one consecutive shoulder MRIs were reviewed for the presence or absence of the STSL, including the imaging plane and sequence that best depicted the ligament. Dimensions of the ligament were recorded.

RESULTS

Fifty four of 121 shoulder MRIs were technically adequate for visualization of the STSL, and it was identified on 51 of these studies (94%). There was no statistically significant difference between 1.5-T and 3-T systems. The best individual sequence for visualizing the STSL was the sagittal T1-weighted sequence, in which the STSL was visible on 75/80 technically adequate sequences (94%). The sagittal plane was the best plane for visualizing the STSL, in which it was visible on 65/69 technically adequate studies (94%). The STSL on average measured 12.8 ± 1.5 mm in transverse dimension.

CONCLUSIONS

The STSL can be visualized on the majority of shoulder MRIs and is best seen on sagittal T1-weighted images on our imaging protocol. Evaluation of the STSL can potentially help in identifying pathologic conditions affecting the suprascapular nerve.

Morphological and radiological study of ossified superior transverse scapular ligament as potential risk factor of suprascapular nerve entrapment

The suprascapular notch is covered superiorly by the superior transverse scapular ligament. This region is the most common place of suprascapular nerve entrapment formation. The study was performed on 812 specimens: 86 dry scapulae, 104 formalin-fixed cadaveric shoulders, and 622 computer topography scans of scapulae. In the cases with completely ossified superior transverse scapular ligament, the following measurements were performed: proximal and distal width of the bony bridge, middle transverse and vertical diameter of the suprascapular foramen, and area of the suprascapular foramen. An ossified superior transverse scapular ligament was observed more often in men and in the right scapula. The mean age of the subjects with a completely ossified superior transverse scapular ligament was found to be similar than in those without ossification. The ossified band-shaped type of superior transverse scapular ligament was more common than the fan-shaped type and reduced the space below the ligament to a significantly greater degree. The ossified band-shaped type should be taken into consideration as a potential risk factor in the formation of suprascapular nerve entrapment. It could explain the comparable frequency of neuropathy in various populations throughout the world despite the significant differences between them in occurrence of ossified superior transverse scapular ligament.

Therapeutic potential of perivascular cells from human pluripotent stem cells

Vascularization of injured tissues or artificial grafts is a major challenge in tissue engineering, stimulating a continued search for alternative sources for vasculogenic cells and the development of therapeutic strategies. Human pluripotent stem cells (hPSCs), either embryonic or induced, offer a plentiful platform for the derivation of large numbers of vasculogenic cells, as required for clinical transplantations. Various protocols for generation of vasculogenic smooth muscle cells (SMCs) from hPSCs have been described with considerably different SMC derivatives. In addition, we recently identified hPSC-derived pericytes, which are similar to their physiological counterparts, exhibiting unique features of blood vessel-residing perivascular cells, as well as multipotent mesenchymal precursors with therapeutic angiogenic potential. In this review we refer to methodologies for the development of a variety of perivascular cells from hPSCs with respect to developmental induction, differentiation capabilities, potency and their dual function as mesenchymal precursors. The therapeutic effect of hPSC-derived perivascular cells in experimental models of tissue engineering and regenerative medicine are described and compared to those of their native physiological counterparts.

Topographical anatomy of the suprascapular nerve and vessels at the suprascapular notch

Suprascapular nerve entrapment caused by the superior transverse scapular ligament (STSL) causes pain, and limitation of motion in the shoulder. To relieve these symptoms, suprascapular nerve decompression is performed through the resection of STSL. To describe and classify the topographic anatomy of the suprascapular notch, 103 cadaveric shoulders were dissected. The mean length and width of STSLs were 11.2 and 3.4 mm, respectively. The bony bridges replacing STSL in four shoulders were 8.2 mm long and 3.5 mm wide on average. The suprascapular nerve always ran through the notch under the STSL. All shoulders had a single suprascapular artery, while multiple suprascapular veins appeared in 21.3%. The arrangement of the suprascapular vessels was classified into three types: in Type I (59.4%), all suprascapular vessels ran over the STSL; in Type II (29.7%), the vessels ran over and under the STSL simultaneously; in Type III (10.9%), all vessels ran under the STSL. In 48.9% of cadavers, these types were bilaterally matched. The omohyoid muscle originated distantly from the STSL in 38.0%, was adjacent to it in 44.0%, and was partially over the STSL in 18.0%. The number of suprascapular vessels running under the STSL was positively correlated with the size of the STSL and the middle diameter of the suprascapular notch. Age was inversely correlated with the length of STSL. The STSL was wider in males than in females. This study provides details of the structural variations in the region of the suprascapular notch.

Arthroscopic decompression of a bony suprascapular foramen

Arthroscopic decompression of the suprascapular nerve by transection of the transverse scapular ligament has only recently been described. Arthroscopic decompression of a bony suprascapular notch foramen has not been previously reported. This article presents a case report and outlines an arthroscopic technique to safely decompress a bony suprascapular notch. In the subacromial space, a lateral portal is used for viewing and a posterior portal for instrumentation. The medial wall of the subacromial bursa located behind the acromioclavicular joint is debrided with the shaver facing laterally and superiorly. The posterior acromioclavicular artery is routinely coagulated. A superomedial portal is now established using spinal needle localization. A smooth 5.5-mm cannula is placed in this portal and the coracoclavicular ligaments (trapezoid and conoid) are followed to the coracoid. The smooth cannula serves nicely to sweep and retract the suprascapular artery and associated fibrofatty tissue from the field of view while allowing instrumentation and visualization of the suprascapular notch. The course of the suprascapular nerve and morphology of the notch is confirmed. A Kerrison punch rongeur, routinely used in spine surgery, is introduced through the superomedial portal and a notchplasty is performed safely, allowing decompression of the suprascapular nerve.

The structure of the coracoacromial ligament: fibrocartilage differentiation does not necessarily mean pathology

The coracoacromial ligament forms part of the coracoacromial arch and is implicated in impingement syndrome and acromial spur formation. Here, we describe its structure and the composition of its extracellular matrix. Ligaments were obtained from 15 cadavers, nine from older people (average age 74.7 years) and six from younger individuals (average age 24.2 years). Cryosections of methanol-fixed tissue were cut and sections were immunolabelled with monoclonal antibodies against collagens, glycosaminoglycans, proteoglycans, matrix proteins and neurofilament proteins. Both ligament entheses were highly fibrocartilaginous and immunolabelled strongly for type II collagen, aggrecan and link protein. The area of labelling was more extensive in older people. However, fibrocartilage also characterized the ligament midsubstance, particularly with increased age. Signs of fibrocartilage degeneration were more common in older people. Ligament fat (containing blood vessels and nerve fibers) was conspicuous in both age groups, especially between fiber bundles at the entheses. We conclude that fibrocartilage is a normal feature but becomes more pronounced with age. It is not necessarily pathological, for it simply indicates that the ligament is subject to compression and/or shear. Nevertheless, the prominence of fibrocartilage at the acromial enthesis may relate to the frequency with which enthesophytes develop.

Quantitative and comparative studies of the vocal fold extracellular matrix II: collagen

OBJECTIVES

This study examines the collagen content and turnover in the midmembranous vocal fold laminae propriae (LPs) of humans, dogs, pigs, and ferrets.

METHODS

The LP collagen levels were assessed by quantifying tissue hydroxyproline. Quantitative histology allowed evaluation of the collagen content in specific LP regions. Several collagen types and two markers of collagen turnover were examined immunohistochemically.

RESULTS

Collagen made up 43.4% +/- 2.6% of human LP total protein (TP), with men having approximately 30% higher collagen content than women (p < .024). The collagen levels in pigs (52.6% +/- 1.9% of TP) and ferrets (29.8% +/- 3.7% of TP), but not that in dogs (45.3% +/- 1.2% of TP), varied significantly from that in humans (pigs, p < .016; ferrets, p < .011). Quantitative histology indicated marked interspecies differences in total collagen distribution. Collagen types I, III, and IV were detected in the LP, and spatially complex staining patterns were observed for the two markers of collagen turnover studied.

CONCLUSIONS

The collagen content of the human LP is approximately 60% to 70% of that of human dermis. Although canine LP collagen levels are most similar to those of humans, quantitative histology indicates that the collagen distribution of the human LP is best matched by the porcine LP. Collagen types I and III seem to be the dominant LP collagens. Spatial variations in collagen turnover appear to exist that may contribute to normal LP physiology.

Distal femoral intercondylar notch dimensions and their relationship to composition and metabolism of the canine anterior cruciate ligament

OBJECTIVE

To determine the relationship between the dimensions of the distal femoral intercondylar notch (ICN) and the composition and metabolism of the anterior cruciate ligament (ACL) in three dog breeds with different relevant risks to ligament rupture and subsequent osteoarthritis (OA).

DESIGN

ICN measurements were obtained from the femurs of Golden Retrievers (high risk), Labrador Retrievers (high risk) and Greyhounds (low risk). Femoral condyle width and height, ICN height and width indices, and notch shape index were measured using Vernier callipers in all dogs. Intact ACLs were obtained from the same dog breeds for a study of the impinged areas and were analysed for collagen content, collagen cross-links, and sulphated glycosaminoglycan (GAG) content, matrix metalloproteinase (MMP)-2 and the tissue inhibitors of metalloproteinases (TIMPs)-1 and -2.

RESULTS

Femoral condyle width and height and ICN width indices were significantly greater in the low risk compared to the high risk breeds (P<0.01 for all parameters). In contrast, the pro (P=0.003) and active (P=0.007) forms of MMP-2 and sulphated GAGs (P=0.0002) were significantly greater in the impinged areas of the ACLs of the rupture predisposed breeds.

CONCLUSIONS

Impingement by the ICN on the ACLs of the high risk breeds may result in increased collagen remodelling and increased sulphated GAG deposition, causing reduced structural integrity of the ligament. Altered ACL composition may predispose the ligament to increased laxity leading to joint degeneration and OA. This may have a comparative implication for pathogenesis of ACL rupture in humans.

An immunohistochemical study of the tissue bridging adult spondylolytic defects--the presence and significance of fibrocartilaginous entheses

Introduction Spondylolytic spondylolisthesis is an osseous discontinuity of the vertebral arch that predominantly affects the fifth lumbar vertebra. Biomechanical factors are closely related to the condition. An immunohistochemical investigation of lysis-zone tissue obtained from patients with isthmic spondylolisthesis was performed to determine the molecular composition of the lysis-zone tissue and enable interpretation of the mechanical demands to which the tissue is subject.

METHODS

During surgery, the tissue filling the spondylytic defects was removed from 13 patients. Twelve spondylolistheses were at the L5/S1 level with slippage being less than Meyerding grade II. Samples were methanol fixed, decalcified and cryosectioned. Sections were labelled with a panel of monoclonal antibodies directed against collagens, glycosaminoglycans and proteoglycans.

RESULTS

The lysis-zone tissue had an ordered collagenous structure with distinct fibrocartilaginous entheses at both ends. Typically, these had zones of calcified and uncalcified fibrocartilage labelling strongly for type II collagen and aggrecan. Labelling was also detected around bony spurs that extended from the enthesis into the lysis-zone. The entheses also labelled for types I, III and VI collagens, chondroitin four and six sulfate, keratan and dermatan sulfate, link protein, versican and tenascin.

CONCLUSIONS

Although the gap filled by the lysis tissue is a pathological feature, the tissue itself has hallmarks of a normal ligament-i.e. fibrocartilaginous entheses at either end of an ordered collagenous fibre structure. The fibrocartilage is believed to dissipate stress concentration at the hard/soft tissue boundary. The widespread occurrence of molecules typical of cartilage in the attachment of the lysis tissue, suggests that compressive and shear forces are present to which the enthesis is adapted, in addition to the expected tensile forces across the spondylolysis. Such a combination of tensile, shear and compressive forces must operate whenever there is any opening or closing of the spondylolytic gap.

Proteoglycans and catabolic products of proteoglycans present in ligament

The aim of the present study was to characterize the proteoglycans and catabolic products of proteoglycans present in the tensile region of ligament and explant cultures of this tissue, and to compare these with those observed in the tensile region of tendon. Approx. 90% of the total proteoglycans in fresh ligament was decorin, as estimated by N-terminal amino acid sequence analysis. Other species that were detected were biglycan and the large proteoglycans versican (splice variants V(0) and/or V1 and/or V2) and aggrecan. Approx. 23% of decorin detected in the matrix was degraded. Intact decorin and decorin fragments similar to those observed in the matrix that retained the N-terminus were also observed in the medium of ligament cultures. Intact biglycan core protein was detected in the matrix and medium of ligament cultures, and two fragments originating from the N-terminal region of biglycan were observed in the matrix of cultured ligament. Versican and versican fragments that retained the N-terminus of versican core protein were detected in fresh matrix and medium of tendon cultures. Approx. 42% of versican present in the fresh ligament was degraded. Aggrecan catabolites appearing in the culture medium were derived from aggrecanase cleavage of the core protein. An intact link protein and a degradation product from the N-terminal region of type XII collagen were also detected in the medium of the ligament explant.

Molecular composition and pathology of entheses on the medial and lateral epicondyles of the humerus: a structural basis for epicondylitis

OBJECTIVES

To improve the understanding of epicondylitis by describing the normal structure and composition of the entheses associated with the medial and lateral epicondyles and their histopathology in elderly cadavers.

METHODS

Medial and lateral epicondyles were obtained from 12 cadavers. Six middle aged cadavers (mean 47 years) were used to assess the molecular composition of "normal" entheses from people within an age range vulnerable to epicondylitis. Cryosections of epicondylar entheses were immunolabelled with monoclonal antibodies against molecules associated with fibrocartilage and related tissues. A further six elderly cadavers (mean 84 years) were used for histology to assess features of entheses related to increasing age.

RESULTS

Tendon entheses on both epicondyles fused with those of the collateral ligaments and formed a more extensive structure than hitherto appreciated. Fibrocartilage (which labelled for type II collagen and aggrecan) was a constant feature of all entheses. Entheses from elderly subjects showed extensive microscopic damage, hitherto regarded as a hallmark of epicondylitis.

CONCLUSIONS

Fibrocartilage is a normal feature and not always a sign of enthesopathy. Furthermore, pathological changes documented in patients with epicondylitis may also be seen in elderly people. The fusion of the common extensor and flexor tendon entheses with those of the collateral ligaments suggests that the latter may be implicated as well. This may explain why pain and tenderness in epicondylitis may extend locally beyond the tendon enthesis and why some patients are refractory to local treatments.

Biology of Fibrocartilage Cells

Fibrocartilage is an avascular tissue that is best documented in menisci, intervertebral discs, tendons, ligaments, and the temporomandibular joint. Several of these sites are of particular interest to those in the emerging field of tissue engineering. Fibrocartilage cells frequently resemble chondrocytes in having prominent rough endoplasmic reticulum, many glycogen granules, and lipid droplets, and intermediate filaments together with and actin stress fibers that help to determine cell organization in the intervertebral disc. Fibrocartilage cells can synthesize a variety of matrix molecules including collagens, proteoglycans, and noncollagenous proteins. All the fibrillar collagens (types I, II, III, V, and XI) have been reported, together with FACIT (types IX and XII) and network-forming collagens (types VI and X). The proteoglycans include large, aggregating types (aggrecan and versican) and small, leucine-rich types (decorin, biglycan, lumican, and fibromodulin). Less attention has been paid to noncollagenous proteins, although tenascin-C expression may be modulated by mechanical strain. As in hyaline cartilage, matrix metalloproteinases are important in matrix turnover and fibrocartilage cells are capable of apoptosis.

Variations in anatomy at the suprascapular notch possibly causing suprascapular nerve entrapment: an anatomical study

The purpose of the study was to determine anatomical variations at the suprascapular notch for better understanding of possible predisposing factors for suprascapular nerve entrapment. We dissected 32 shoulders of 16 cadavers between the ages of 39 and 74 years. We observed abnormally oriented superior fibers of the subscapularis muscle in five shoulders of the 16 cadavers, which were covering the entire anterior surface of the suprascapular notch and significantly reducing the available space for the suprascapular nerve. We also detected anterior coracoscapular ligament in six of the 32 shoulders, and calcified superior transverse scapular ligament in four of the shoulders. In this study, we classified the variations for the superior transverse scapular ligament. In conclusion, knowing the anatomical variations in detail along the course of the suprascapular nerve might be important for better understanding of location and source of the entrapment syndrome, especially for individuals who are involved in violent overhead sports activities such as volleyball and baseball. To our knowledge, close relationship of subscapularis muscle with the suprascapular nerve as a possible risk factor for suprascapular nerve entrapment has not been mentioned previously.