Fibrocartilage in various regions of the human glenoid labrum. An immunohistochemical study on human cadavers

Histological Analysis of Regenerative Properties in Human Glenoid Labral Regions

BACKGROUND

The healing capacity of the human glenoid labrum varies by tear location. Current evidence suggests that the healing capacity of meniscal and cartilage injuries relates to cellular composition and vascularity. However, little is known about the histological characteristics of the glenoid labrum and how they may affect healing potential in specific anatomic regions.

HYPOTHESIS

Regenerative characteristics of the glenoid labrum differ based on the anatomic region.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Human glenoid labra from fresh unpreserved cadavers were transversely sectioned in different anatomic regions. Masson trichrome stain was used to determine dense and loose extracellular matrix regions and vessel densities. Hematoxylin and eosin, Ki-67+, and CD90+/CD105+ stains were performed to determine total, proliferative, and progenitor cell densities, respectively. Regression models demonstrated relationships between vascular area, progenitor cell quantity, and probability of successful operation.

RESULTS

Among all labral aspects, the superior glenoid labrum had the highest percentage (56.8% ± 6.9%) of dense extracellular matrix or avascular tissue (P < .1). The vascular region of the superior labrum had the fewest total cells (321 ± 135 cells/mm2; P < .01) and progenitor cells (20 ± 4 cells/mm2; P < .001). Vascular area was directly correlated with progenitor cell quantity (P = .006002). An increase in probability of successful operation was associated with a linear increase in vascular area (R2 = 0.765) and an exponential increase in progenitor cell quantity (R2 = 0.795). Subsequently, quadratic models of vascularity and progenitor cell quantity around the labral clock were used to assess relative healing potential. Quadratic models for percentage vascular area (P = 6.35e-07) and weighted progenitor cell density (P = 3.03e-05) around the labral clock showed that percentage vascular area and progenitor cell quantity increased as labral tissue neared the inferior aspect and diminished near the superior aspect.

CONCLUSION

Anatomic regions of the glenoid labrum differ in extracellular matrix composition, vascularity, and cell composition. The superior glenoid labrum is deficient in vascularity and progenitor cells, which may explain the high failure rates for repairs in this location.

CLINICAL RELEVANCE

Improved understanding of the composition of distinct glenoid labral positions may help to improve therapeutic strategies for labral pathology.

Superior and Anterior Glenoid Labral Tears Are Associated With Increased Neurofilament Concentration

BACKGROUND

Pain is a common presentation after glenohumeral labral injuries. However, the source of that pain is undetermined.

PURPOSE/HYPOTHESIS

We aimed to determine if there is a differential expression of nerve fibers around the glenoid labrum and if torn labra have increased neuronal expression compared with untorn labra (rotator cuff repair labra). We hypothesized that the superior labrum would have a higher concentration of neurofilament than would the rest of the labrum and that the concentration of neurofilament would increase at the site of a labral tear.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Seven labra were sampled at the 3-, 5-, 9-, and 12-o'clock positions during total shoulder arthroplasty. Samples were also collected at the 3-, 5-, and 12-o'clock positions during rotator cuff repair (16 labra), anterior labral repair (6 labra), type II superior labral anterior to posterior (SLAP) repair (4 labra), and capsular release for idiopathic capsulitis (5 labra). Sections were immunostained with antibodies to neurofilament, a specific neuronal marker that is used to identify central and peripheral nerve fibers, and the concentration and intensity of immunostained-positive cells assessed.

RESULTS

The concentration of neurofilament staining was similar in the superior, anterior, posterior, and inferior glenoid labrum in untorn labra (8 neurofilament expressing cells per square millimeter; P = .3). Torn labra exhibited a 3- to 4-fold increase in neuronal expression, which was isolated to the location of the tear in SLAP (P = .09) and anterior labral tears (P = .02). The concentration of neurofilament expressing cells in torn glenoid labrum samples was comparable that in with the glenoid labrum of adhesive capsulitis samples (P = .7).

CONCLUSION

This study supports the hypothesis that after a tear of the anterior or superior labrum the labrum in that region becomes populated with new nerves fibers and that these fibers may be responsible for the pain noted by patients with superior (SLAP) and/or anterior labral (Bankart) tears.

CLINICAL RELEVANCE

This study suggests that neural infiltration contributes to the pain experienced by patients with labral tears. It may help with patient education and direct future management of labral lesions.

Anatomical, functional and biomechanical review of the glenoid labrum

The glenohumeral joint is the most mobile joint in the human skeleton, supported by both active and passive stabilisers. As one of the passive stabilisers, the glenoid labrum has increasingly been recognised to play an important role in stability of the glenohumeral joint, acting to maintain intraarticular pressure, centralise the humeral head and contribute to concavity-compression stability. Several studies have investigated the macro- and micro-anatomical features of the labrum as well as its biomechanical function. However, in order to better understand the role of the labrum and its mechanics, a comprehensive anatomical, functional and biomechanical review of these studies is needed. Therefore, this article reviews the current literature detailing anatomical descriptions of the glenoid labrum, with an emphasis on its function(s) and biomechanics, as well as its interaction with neighbouring structures. The intimate relationship between the labrum and the surrounding structures was found to be important in glenohumeral stability, which owes further investigation into the microanatomy of labrum to better understand this relationship.

The glenoid labrum: does labral lesion location matter?

Background

The glenoid labrum can be torn in 1 or more locations. It is undetermined if the location of the labral tear alters patient outcomes after repair.

Methods

A total of 252 labral repair cases were retrospectively reviewed using prospectively collected patient-ranked outcomes and examiner-determined assessments preoperatively, at 1 week, 6 weeks, 24 weeks, and at a minimum of 2 years after surgery.

Results

Preoperatively, patients who underwent a superior labral repair reported worse pain at night and during activity than patients who subsequently underwent an isolated anterior labral repair or a combined anterior and superior labral repair (P < .05). After surgery, patients who underwent an isolated superior labral repair reported more severe pain at night and during activity, increased stiffness, and less satisfaction with their shoulder than patients who had an isolated anterior (P < .05) or a combined anterior and superior labral repair (P < .05).

Conclusions

Patients with isolated superior labral repairs have more pain both before and after repair than patients who undergo anterior or anterior and superior labral repairs.

Histology, vascularity and innervation of the glenoid labrum

BACKGROUND

Although the glenoid labrum has an important role in shoulder stability, little is known about its composition, vascularity and innervation. The aims of this study were therefore to evaluate the histology, vascularity and innervation of the glenoid labrum.

MATERIALS AND METHODS

Ten glenoid labrum specimens (three male, two female: mean age 81.2 years, range 76-90 years) were detached at the glenoid neck. Following decalcification, sections were cut through the whole thickness of each specimen perpendicular to the glenoid labrum at 12 radii corresponding to a clock face superimposed on the glenoid fossa. Then they were stained using haematoxylin and eosin, a silver nitrate protocol or subjected to immunohistochemistry using anti-protein gene protein 9.5 to demonstrate neuronal processes.

RESULTS

The labrum was fibrocartilaginous, being more fibrous in its free margin. There was a variable distribution of blood vessels, being more vascular in its periphery, with many originating from the fibrous capsule and piercing the glenoid labrum. Immunohistochemistry revealed positive staining of nerve fibres within the glenoid labrum.

CONCLUSION

The glenoid labrum is fibrocartilaginous, being more fibrous in its periphery, and is vascularized, with the anterosuperior aspect having a rich blood supply. Free sensory nerve fibres were also present; no encapsulated mechanoreceptors were observed. The presence of sensory nerve fibres in the glenoid labrum could explain why tears induce pain. It is postulated that these sensory fibres could play a role in glenohumeral joint proprioception.

Cartilage Morphological and Histological Findings After Reconstruction of the Glenoid With an Iliac Crest Bone Graft

BACKGROUND

The J-bone graft is presumably representative of iliac crest bone grafts in general and allows anatomic glenoid reconstruction in cases of bone defects due to recurrent traumatic anterior shoulder dislocations. As a side effect, these grafts have been observed to be covered by some soft, cartilage-like tissue when arthroscopy has been indicated after such procedures.

PURPOSE

To evaluate the soft tissue covering of J-bone grafts by use of magnetic resonance imaging (MRI) and histological analysis.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients underwent MRI at 1 year after the J-bone graft procedures. Radiological data were digitally processed and evaluated by segmentation of axial images. Independent from the MRI analysis, 2 biopsy specimens of J-bone grafts were harvested for descriptive histological analysis.

RESULTS

Segmentation of the images revealed that all grafts were covered by soft tissue. This layer had an average thickness of 0.87 mm compared with 1.96 mm at the adjacent native glenoid. Of the 2 biopsy specimens, one exhibited evident hyaline-like cartilage and the other presented patches of chondrocytes embedded in a glycosaminoglycan-rich extracellular matrix.

CONCLUSION

J-bone grafts are covered by soft tissue that can differentiate into fibrous and potentially hyaline cartilage. This feature may prove beneficial for delaying the onset of dislocation arthropathy of the shoulder.

Serum Cartilage Biomarkers and Shoulder Instability

Differences in cartilage biomarkers have been noted in patients with anterior cruciate ligament tears, but little is known about any similar relationship with shoulder instability. This study evaluated the relationship between serum cartilage biomarkers and shoulder instability. The authors present a prospective cohort study of young athletes followed from 2006 to 2010. A nested case-control analysis was conducted within this cohort to evaluate the association between preinjury collagen type II cleavage (a marker for type II collagen cleavage) and procollagen II carboxy propeptide (a marker of cartilage synthesis) and the subsequent likelihood of shoulder instability during the 4-year follow-up period. Preinjury collagen type II cleavage and procollagen II carboxy propeptide levels in 51 subjects who had shoulder instability were compared with levels in 210 subjects without documented anterior cruciate ligament or shoulder instability (control group) with commercially available enzyme-linked immunosorbent assay kits. Mean preinjury collagen type II cleavage levels in patients who subsequently had shoulder instability were significantly lower than those in the control group (73.91 vs 79.24 pg/mL, P=.03). No significant difference was found in preinjury procollagen II carboxy propeptide levels compared with the control group (359.94 vs 396.37, P=.24). This study is the first to examine the relationship between baseline collagen biomarkers and subsequent shoulder instability. The finding of lower baseline collagen type II cleavage levels in patients with subsequent shoulder instability may represent a genetic predisposition or a compensatory mechanism by which cartilage degradation is decreased in those who are more likely to have instability. [Orthopedics. 2017; 40(1):34-36.].

Quantitative analysis of attachment of the labrum to the glenoid fossa: a cadaveric study

PURPOSE

This study investigated the direct and continuous attachment of the labrum to the glenoid fossa, including the fibrocartilaginous tissue, using image-analysis software and histology.

METHODS

Twenty-six cadaveric shoulders (11 male, 15 female; mean age 80.1 years; age range 36-103 years) were used. The glenoid of each specimen was divided into six pie-slice-shaped pieces from the center perpendicular to the articular surface by radial incisions at the 2, 4, 6, 8, 10, and 12 o'clock positions. The general distribution of the labrum, including the fibrocartilage, was assessed in hematoxylin and eosin-, Safranin O- and Azan-Mallory-stained sections. The continuous length of attachment of the labrum to the glenoid was measured using image-analysis software. The width of attachment to the articular surface of the glenoid was assessed in each position.

RESULTS

The labrum attached to both the articular surface and the neck of the glenoid in all shoulders (100 %) in the 4 and 6 o'clock positions. The mean length of the entire attachment to the glenoid was 4.6 mm (range 3.2-6.1 mm). The width of attachment from the bony edge of the glenoid to the edge of the labrum on the articular surface ranged from 0 to 4.3 mm. The length of the entire attachment of the labrum was shortest in the 2 o'clock position (p = 0.229). Additionally, the length of the entire attachment of the labrum was longest in the 4 o'clock position. The width of attachment to the articular surface of the glenoid was greatest in the 4 o'clock position (p < 0.01).

CONCLUSION

In the 4 and 6 o'clock positions, the labrum attached to both the articular surface and neck of the glenoid in all of the shoulders (100 %). The length of the entire attachment to the labrum, including the fibrocartilage, was shortest in the 2 o'clock position. The width of attachment to the articular surface of the glenoid was greatest in the 4 o'clock position (p < 0.01).