Fibrocartilage in the extensor tendons of the human metacarpophalangeal joints

The biomechanical evaluation of metacarpal fractures fixation methods during finger movements: a finite element study

Objective

This study used finite element analysis to simulate four commonly used fixation methods for metacarpal shaft oblique fractures during finger motion and evaluate their biomechanical performance. The aim was to provide evidence for clinically selecting the optimal fixation method, guiding early rehabilitation treatment, and reducing the risk of complications.

Methods

Finite element analysis simulated dynamic proximal phalanx motion (60° flexion, 20° extension, 20° adduction, and 20° abduction). We analysed stress, displacement, and distributions for dorsal plates, intramedullary nails, Kirschner wire, and screw fixation methods.

Results

At 60° of finger flexion and 20° of abduction, plate fixation demonstrated greater stability and minimal displacement, with a peak displacement of 0.19 mm; however, it showed higher stress levels in all motion states, increasing the risk of failure. The stability of the intramedullary nail was similar to that of the dorsal plate, with a maximum displacement difference of 0.04 mm, and it performed better than the dorsal plate during adduction of 20°. Kirschner wire showed the highest stress levels of 81.6 Mpa during finger flexion of 60°, indicating a greater risk of failure and unstable displacement. Screws had lower stress levels in all finger motion states, reducing the risk of failure, but had poorer stability. Stress and displacement distributions showed that the dorsal plate, intramedullary nail, and Kirschner wire mainly bore stress on the implants, concentrating near the fracture line and the proximal metacarpal. In contrast, the screws partially bore stress in the screw group. The anterior end of the metacarpal mainly hosted the maximum displacement.

Conclusion

This study demonstrates that under simulated finger motion states, the dorsal plate fixation method provides the best stability in most cases, especially during finger flexion and abduction. However, high stress levels also indicate a higher risk of failure. The intramedullary nail is similar to the dorsal plate in stability and performs better in certain motion states. Kirschner wire exhibits the highest risk of failure during flexion. Although screws have poorer stability in some motion states, they offer a lower risk of failure. These findings provide important reference and surgical selection strategies for treating metacarpal fractures.

Enthesitis in Psoriatic Arthritis, the Sonographic Perspective

Purpose of Review

To provide an overview of the ultrasound (US) studies focusing on enthesitis in psoriatic arthritis (PsA).

Recent Findings

Last-generation US equipment has demonstrated the ability to detect subtle morphostructural and vascular abnormalities at entheseal level. US is able to identify pathologic changes in both “classical” (i.e., the site of attachment of tendons, ligaments, and joint capsules into the bone) and “functional” entheses (i.e., anatomical regions where tendons or ligaments wrap around bony pulleys).

Summary

US has the potential to be the first-line method in the assessment of enthesitis. In the present review we critically discussed the current definitions of US enthesitis, the scoring systems, and the main fields of application (i.e., the detection of enthesitis in PsA and psoriasis, the identification of different disease subsets, and the assessment of response to treatment).

Autologous endothelialized vein allografts in coronary artery bypass surgery - Long term results

BACKGROUND

Lack of autologous graft material restricts the ability to treat patients requiring coronary artery bypass surgery (CABG). An off the shelf tissue engineered small diameter vascular graft is the holy grail of cardiovascular surgery.

METHODS

Allograft saphenous veins were harvested from organ donors, cryopreserved, deendothelialized and then seeded with autologous endothelial cells prior to implantation during coronary artery bypass surgery. All patients treated were followed-up until death and angiographic results were collected. Grafts were explanted during autopsy and immunohistochemistry was performed.

RESULTS

Twelve patients received 15 engineered grafts. Mean patient survival was 9.1 ± 1.8 years. Six month graft patency was 80 (95% CI: 59-100) and 9 month graft patency was 50 (95% CI: 27-93) - graft patency detected up to 32 months after surgery. Immunohistochemistry in grafts explanted showed a presence of CD31 and CD68 positive cells in the luminal region of the vessel walls and layers of Collagen Type I in the abluminal vessel walls.

CONCLUSIONS

Our small diameter tissue engineered vascular graft shows openness up to 32 months after implantation. Immunohistochemistry suggests that monocyte activation may lead to vessel remodeling with thickening of the vessel wall. Research should concentrate on a manipulation of remodeling processes.

Peritenon Extensor Tendon Inflammation in Psoriatic Arthritis Is an Enthesitis-related Lesion

Objective.

To analyze the association between enthesitis, synovitis, and peritenon extensor tendon inflammation (PTI) in psoriatic arthritis (PsA).

Methods.

PsA patients with swelling of metacarpophalangeal joints were included. Greyscale and power Doppler (PD) were used for synovitis and PTI ultrasound identification. Madrid Sonographic Enthesis Index (MASEI) was used for enthesitis assessment. PD activity was evaluated using PD item of MASEI and PD Outcome Measures in Rheumatology (OMERACT) definition.

Results.

Synovitis had no association with enthesitis. PTI was associated with PD MASEI and PD OMERACT. Only PD OMERACT showed a positive correlation with PTI.

Conclusion.

In PsA, PTI is associated to enthesitis, as opposed to synovitis.

Imaging in Psoriatic Arthritis-Insights About Pathogenesis of the Disease

PURPOSE OF REVIEW

Heterogeneity is a hallmark of PsA as musculoskeletal inflammation can affect different tissues including the synovial joint, tendons, entheses, bursa, and bone.

RECENT FINDINGS

Relying on clinical examination for investigating underlying mechanisms in PsA is limited by the inherent inaccuracies of examination of the joints, enthesis, and spine. In addition, unlike synovial-centered diseases, histology is hard to obtain for the entheses and spine, limiting the knowledge for different manifestations of PsA. These limitations prompted the use of imaging modalities to improve our understanding of the underlying mechanisms in PsA. Imaging modalities can identify and quantify the extent of inflammation and damage in the synovial joints, entheses, and tendons which all contribute to the heterogeneity of PsA. This review summarizes the contribution of imaging to the understanding of the underlying mechanisms of different clinical manifestations of PsA.

The Dorsal Triangular Fibrocartilage of the Metacarpophalangeal Joint: A Cadaveric Study

PURPOSE

To describe a fibrocartilaginous structure on the dorsal surface of the metacarpophalangeal (MCP) joint.

METHODS

A combination of anatomical dissection, histology, ultrasound, and magnetic resonance imaging was undertaken to explore the anatomical structure described, with clinical correlation undertaken by surgical exploration of MCP joints.

RESULTS

A dorsal structure of the MCP joint was identified as fibrocartilagenous in composition, triangular in shape, and-together with the volar plate and collateral and accessory collateral ligaments-forming a deepened dorsal fossa in which the metacarpal head invaginated. It was attached to the extensor tendon by loose connective tissue and formed part of the joint capsule.

CONCLUSIONS

The dorsal fibrocartilage of the MCP joint is a constant anatomical structure that appears to complement the structural support for the metacarpal head and extensor tendon. Possible functions include stabilization of the extensor tendon, formation of a dorsal fossa, prevention of extensor tendon attrition, and synovial fluid production. Its structure and function may have implications in future development of joint replacement devices.

CLINICAL RELEVANCE

This study adds to the collective knowledge about the precise anatomy of the MCP joint. Reconstructive surgery and, in particular, joint replacement surgery should consider the potential function and importance of this structure when designing interventions on the joint.

Analysis of periarticular bone changes in patients with cutaneous psoriasis without associated psoriatic arthritis

Objectives

To search for structural bone changes in the joints of psoriasis patients without psoriatic arthritis (PsA).

Methods

55 psoriasis patients without any current or past symptoms of arthritis or enthesitis and 47 healthy controls were examined by high-resolution peripheral quantitative CT scans of the metacarpophalangeal joints. Number, size and exact localisation of erosions and enthesiophytes were recorded by analysing axial scans of the metacarpal heads and phalangeal bases and were confirmed in additional coronal and/or sagittal sections. In addition, we collected demographic and clinical data including subtype, duration and severity of psoriasis.

Results

Psoriasis patients showed a larger and significantly increased number of enthesiophytes (total number 306; mean±SD/patient 5.62±3.30) compared with healthy controls (total number 138; mean±SD/patient 3.04±1.81, p<0.001). Enthesiophytes were typically found at the dorsal and palmar sides of the metacarpal heads where functional entheses related to extensor and flexor tendons are localised. Bone erosions were rare and not significantly different between psoriasis patients and healthy controls. If present, erosions were almost exclusively found at the radial side of the second metacarpal head in both psoriasis patients and healthy controls.

Conclusions

Psoriasis patients without PsA show substantial signs of enthesiophyte formation compared with healthy controls. These changes represent new bone formation at mechanically exposed sites of the joint and substantiate the concept of the existence of a ‘Deep Koebner Phenomenon’ at enthesial sites in psoriasis patients.

Extensor apparatus of the lesser toes: anatomy with clinical implications--topical review

Lesser toe deformities are one of the most common conditions faced by orthopedic surgeons. Knowledge of the anatomy of the lesser toes is important for ensuring correct diagnosis and treatment of deformities, which are caused by factors such as muscle imbalance between the extensor apparatus and flexor tendons. However, this apparatus has not received sufficient attention in the literature. In addition, the large number of inaccurate and erroneous descriptions means that gaining an understanding of these structures is problematic. The objective of the present article is to clarify the anatomy of the extensor apparatus by means of a pictorial essay, in which the structures involved will be grouped and discussed in detail. The most relevant clinical implications will be addressed.

LEVEL OF EVIDENCE

Level V, expert opinion.

Quantified contours of curvature in female index, middle, ring, and small metacarpophalangeal joints

PURPOSE

To study and quantify the morphology of the curvature of the surfaces of metacarpophalangeal metacarpophalangeal joints and to relate joint morphology to joint function.

METHODS

Forty metacarpophalangeal joints of the index, middle, ring, and small fingers from 5 right and 5 left hands were taken from female cadavers. The articulating surfaces of the metacarpal head and the base of the proximal phalanx were copied in a true-to-scale fashion. The hard plaster models were sliced in 7 sagittal and 7 transverse planes. The curvatures of the section contours were determined with circular gauges. Statistical analyses were performed by analysis of variance and paired Student t-tests.

RESULTS

In the sagittal plane, the cartilaginous surface of the metacarpal head is divided into 2 functional regions and a third dorsal region that does not articulate with the base of the proximal phalanx. The articulating surface of the base of the proximal phalanx approximates a circle in the midsagittal plane. The mean median sagittal radius of curvature of the dorsal articulating aspect of the metacarpal head (6.9 mm) is 33% smaller than that of the base of the proximal phalanx (10.3 mm). The palmar articulating aspect of the metacarpal head (5.8 mm) is 44% smaller than that of the base of the proximal phalanx (10.3 mm). In the median transverse section, the mean radius of curvature of the metacarpal head (7.3 mm) is 18% smaller than that of the base of the proximal phalanx (8.9 mm).

CONCLUSIONS

The data demonstrate the highly significant incongruity in the curvature of the articulating pair. This incongruity provides a joint space with its greatest dimension in the sagittal plane. From a mechanical perspective, the metacarpophalangeal joint mechanically represents a joint with 5 kinematic degrees of freedom: 2 for flexion and extension, 2 for abduction and adduction, and 1 for axial rotation.

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.

Repair of osteochondral defects in the knee by resorbable bioimplants in a rabbit model

BACKGROUND

The intrinsic healing capacity of articular cartilage remains poor, despite various attempts that have been undertaken to treat cartilage defects. This study describes the experimental use of a double-layer bioimplant consisting of a bone-substitute layer and a cartilage-substitute layer.

ANIMALS AND METHODS

In group A, 12 implants were placed into osteochondral defects of the load-bearing area of rabbit femoral condyles. In group B, 12 implantations were done in the same manner, with a separating membrane consisting of cement between both layers to investigate ingrowth of mesenchymal stem cells from the subchondral marrow space. Group C, with 12 similar defects but without treatment, served as control. Investigations by microscopy and immunohistochemistry were done after 12 weeks.

RESULTS

All bioimplants showed coverage of the defect with a regeneration tissue that contained cartilage-like regions. Implants with a cement layer showed less cartilage and more fibrous tissue. The bioimplant group showed more cartilage-like regeneration tissue than the control groups, which only showed incomplete fibrous filling of the defects. Results from the second group supported the hypothesis that the subchondral space must be opened for adequate regeneration. Additional examinations were done using an established semiquantitative score. The bioimplant group showed a significant improvement in results compared to the group with the separating layer and the control group.

INTERPRETATION

Our findings indicate that cartilage repair by resorbable bioimplants seems to be a promising new approach, especially if mesenchymal stem cells are present and can differentiate under mechanical load.

The Pathomechanics of Plantar Fasciitis

Plantar fasciitis is a musculoskeletal disorder primarily affecting the fascial enthesis. Although poorly understood, the development of plantar fasciitis is thought to have a mechanical origin. In particular, pes planus foot types and lower-limb biomechanics that result in a lowered medial longitudinal arch are thought to create excessive tensile strain within the fascia, producing microscopic tears and chronic inflammation. However, contrary to clinical doctrine, histological evidence does not support this concept, with inflammation rarely observed in chronic plantar fasciitis. Similarly, scientific support for the role of arch mechanics in the development of plantar fasciitis is equivocal, despite an abundance of anecdotal evidence indicating a causal link between arch function and heel pain. This may, in part, reflect the difficulty in measuring arch mechanics in vivo. However, it may also indicate that tensile failure is not a predominant feature in the pathomechanics of plantar fasciitis. Alternative mechanisms including 'stress-shielding', vascular and metabolic disturbances, the formation of free radicals, hyperthermia and genetic factors have also been linked to degenerative change in connective tissues. Further research is needed to ascertain the importance of such factors in the development of plantar fasciitis.

Supraspinatus tendon composition remains altered long after tendon detachment

Most rotator cuff surgery is performed on chronic tears, but changes in the composition of chronically torn tendons remain poorly understood. In this study we surgically created supraspinatus tears in the rat and analyzed the composition of the tendon over time using immunohistochemistry. We found that collagen types I and XII were greatly increased initially after injury and then decreased with time. Collagen type III was detected and persisted in the scar for months. Decorin and biglycan were increased initially and then decreased, although decorin remained elevated from normal for months after injury. Aggrecan and collagen type II were detected in small amounts after detachment, which was associated with the expression of sulfated glycosaminoglycans. These alterations were similar to those seen in human studies. As the quality of the tendon is an important factor in repair, these findings may partially explain why chronic tears heal differently than acute tears.

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.

An immunohistochemical study of the rabbit suprapatella, a sesamoid fibrocartilage in the quadriceps tendon containing aggrecan

The rabbit suprapatella is a sesamoid fibrocartilage in the deep surface of the tendon of vastus intermedius and an integral part of the knee joint. We report the presence of a variety of proteoglycans (aggrecan and versican), glycosaminoglycans (chondroitin 4 and 6 sulfate, dermatan sulfate, keratan sulfate) and glycoproteins (tenascin) in its extracellular matrix and the intermediate filament vimentin in the fibrocartilage cells. The most significant finding is the presence of aggrecan in the extracellular matrix, along with its associated link protein and several of its integral glycosaminoglycans. Aggrecan probably enables the suprapatella to withstand compression. Although it can be assumed that aggrecan metabolites detected in synovial fluid from some human joints are predominantly associated with articular hyaline cartilage, the presence of aggrecan in the rabbit suprapatella means that this cannot be assumed for all animal knee joints. We conclude that it is important for orthopedic researchers who use animal models for arthritis research to check for the presence of a suprapatella when joint fluid analyses are interpreted.

The anatomical basis for disease localisation in seronegative spondyloarthropathy at entheses and related sites

The 2 major categories of idiopathic inflammatory arthritis are rheumatoid arthritis and the seronegative spondyloarthropathies. Whilst the synovium is the primary site of joint disease in the former, the primary site in the latter is less well defined. However, it has recently been proposed that enthesitis-associated changes in the spondyloarthropathies are primary and that all other joint manifestations are secondary. Nevertheless, some of the sites of disease localisation have not been adequately explained in terms of enthesitis. This article summarises current knowledge of the structure, function, blood supply, innervation, molecular composition and histopathology of the classic enthesis (i.e. the bony attachment of a tendon or ligament) and introduces the concept of 'functional' and articular 'fibrocartilaginous' entheses. The former are regions where tendons or ligaments wrap-around bony pulleys, but are not attached to them, and the latter are synovial joints that are lined by fibrocartilage rather than hyaline cartilage. We describe how these 3 types of entheses relate to other, and how all are prone to pathological changes in spondyloarthropathy. We propose that the inflammatory responses characteristic of spondyloarthropathies are triggered at these seemingly diverse sites, in genetically susceptible individuals, by a combination of anatomical factors which lead to higher levels of tissue microtrauma, and the deposition of microbes.

Regional structural and viscoelastic properties of fibrocartilage upon dynamic nanoindentation of the articular condyle

Fibrocartilage,a tissue with macromaterial properties between dense fibrous tissue and hyaline cartilage, is not well understood in its ultrastructure and regional viscoelastic properties. Here nanoindentation with atomic force microscopy was performed on fresh fibrocartilage samples of rabbit jaw joint condyles. Each sample was divided into anteromedial, anterolateral, posteromedial, and posterolateral regions for probing and topographic imaging in 2 x 2 microm and 10 x 10 microm scan sizes. Young's moduli differed significantly among these regions in a descending gradient from the anteromedial (2.34 +/- 0.26 MPa) to the posterolateral (0.95 +/- 0.06 MPa). The Poisson ratio, defined as lateral strain over axial strain, had the same gradient distribution: highest for the anteromedial region (0.46 +/- 0.05) and lowest for the posterolateral region (0.31 +/- 0.05). The same four regions showed a descending gradient of surface roughness: highest for the anteromedial (321.6 +/- 13.8 nm) and lowest for the posterolateral (155.6 +/- 12.6 nm). Thus, the regional ultrastructural and viscoelastic properties of fibrocartilage appear to be coregulated. Based on these region-specific gradient distributions, fibrocartilage is constructed to withstand tissue-borne shear stresses, which likely propagate across its different regions. A model of shear gradient and concentric gradient is proposed to describe the region-specific capacity of fibrocartilage to sustain shear stresses in tendons, ligaments, joints, and the healing bone across species.

Fibrocartilage in the transverse ligament of the human atlas

STUDY DESIGN

Immunohistochemical investigation.

OBJECTIVE

To determine whether molecules typical of articular cartilage are present in the transverse ligament and whether the ligament may be a target for an autoimmune response in rheumatoid arthritis.

SUMMARY OF BACKGROUND DATA

In chronic rheumatoid arthritis there is often a marked instability of the atlantoaxial complex, and the transverse ligament can show degenerative changes that compromise its mechanical function. In some rheumatoid patients there can be an autoimmune response to cartilage link protein, aggrecan, and Type II collagen.

METHODS

Transverse ligaments were removed from 13 cadavers and fixed in 90% methanol. Cryosections were immunolabeled with antibodies against proteoglycans (aggrecan, link protein, and versican), glycosaminoglycans (chondroitin-4-sulfate, chondroitin-6-sulfate, dermatan sulfate, and keratan sulfate), and collagens (Types I, II, III, and VI).

RESULTS

Labeling for aggrecan and link protein was characteristic of the fibrocartilages, but versican was only detected in the fibrous regions. Equally, Types I, III, and VI collagens and keratan, dermatan, and chondroitin-4-sulfates were found throughout the ligament, but labeling for Type II collagen and chondroitin-6-sulfate was restricted to the fibrocartilages.

CONCLUSION

The presence of molecules typical of articular cartilage (aggrecan, link protein, and Type II collagen) in the transverse ligament explains why it can be a target for destruction in rheumatoid arthritis and also suggests that it is subject to constant compression against the dens rather than only at the extremes of movement.

An immunohistochemical study of the dorsal capsule of the lumbar and thoracic facet joints

STUDY DESIGN

The molecular composition of the extracellular matrix in the dorsal capsules of lumbar and thoracic facet joints was analyzed immunohistochemically.

OBJECTIVES

To determine whether the immunohistochemical profile of the lumbar joint capsule suggests a role of the capsule in limiting axial rotation of the lumbar motion segment.

SUMMARY OF BACKGROUND DATA

During axial rotation of the lumbar vertebrae, the axis of rotation shifts toward the facet joints in the direction of rotation. Thus, the capsule of the opposing joint should become tensed and wrap around the inferior articular process. Previous studies suggest that wrap-around ligaments are fibrocartilaginous. However, thoracic joint capsules are largely shielded from such loading and should be purely fibrous.

METHODS

Dorsal capsules were removed from lumbar and thoracic facet joints of six adult cadavers. Specimens were immunolabeled with monoclonal antibodies for collagens, chondroitin, dermatan and keratan sulfates, versican, tenascin, aggrecan and link protein. Antibody binding was detected using the Vectastain ABC 'Elite' peroxidase kit (Vector Laboratories, Inc., Burlingame, CA).

RESULTS

Both lumbar and thoracic joint capsules immunolabelled for most glycosaminoglycans and for Type I, III and VI collagens. However, labeling for Type II collagen, chondroitin-6-sulfate, aggrecan, and link protein was restricted to lumbar capsules. Such labeling was constantly seen at entheses and occasionally in the midsubstance.

CONCLUSIONS

The molecular composition of the lumbar joint capsule suggests that it acts as a fibrocartilaginous, 'wrap-around' ligament that withstands compression in addition to tension during torsional movements of the lumbar spine. It wraps around the inferior articular process as rotation occurs and limits further movement.