What type of cartilage repair are we attempting to attain?

Delivery Strategies of Growth Factors in Cartilage Tissue Engineering

Cartilage plays an important role in supporting soft tissues, reducing joint friction, and distributing pressure. However, its self-repair capacity is limited due to the lack of blood vessels, nerves, and lymphatic systems. Tissue engineering offers a potential solution to promote cartilage regeneration by combining scaffolds, seed cells, and growth factors. Among these, growth factors play a critical role in regulating cell proliferation, differentiation, and extracellular matrix remodeling. However, their instability, susceptibility to degradation, and potential side effects limit their effectiveness. This paper reviews the main growth factors used in cartilage tissue engineering and their delivery strategies, including affinity-based delivery, carrier-assisted delivery, stimulus-responsive delivery, spatial structure-based delivery, and cell system-based delivery. Each method shows unique advantages in enhancing the delivery efficiency and specificity of growth factors, but also faces challenges such as cost, biocompatibility, and safety. Future research needs to further optimize these strategies to achieve more efficient, safe, and economical delivery of growth factors, thereby advancing the clinical application of cartilage tissue engineering.

Histophysiology of Fibrocartilage

There are 3 types of cartilage found in the human body: hyaline cartilage, elastic cartilage, and fibrocartilage. Fibrocartilage may be found in intervertebral discs, symphysis pubis, tendinous insertions, acetabular labrums, and the temporomandibular joint. Specifically, in the foot and ankle we mainly see fibrocartilage in tendinous insertions and in areas where tendons wrap around boney prominence. Histologically, fibrocartilage is comprised of an extracellular matrix that contains glycosaminoglycans, proteoglycans, and collagens. This composition allows for a hydrophilic environment, which allows tissue to withstand high compressive forces seen in weight bearing.

The role of TGF-β2 in cartilage development and diseases

Transforming growth factor-beta2 (TGF-β2) is recognized as a versatile cytokine that plays a vital role in regulation of joint development, homeostasis, and diseases, but its role as a biological mechanism is understood far less than that of its counterpart, TGF-β1. Cartilage as a load-resisting structure in vertebrates however displays a fragile performance when any tissue disturbance occurs, due to its lack of blood vessels, nerves, and lymphatics. Recent reports have indicated that TGF-β2 is involved in the physiological processes of chondrocytes such as proliferation, differentiation, migration, and apoptosis, and the pathological progress of cartilage such as osteoarthritis (OA) and rheumatoid arthritis (RA). TGF-β2 also shows its potent capacity in the repair of cartilage defects by recruiting autologous mesenchymal stem cells and promoting secretion of other growth factor clusters. In addition, some pioneering studies have already considered it as a potential target in the treatment of OA and RA. This article aims to summarize the current progress of TGF-β2 in cartilage development and diseases, which might provide new cues for remodelling of cartilage defect and intervention of cartilage diseases.

Headless screw fixation through the dorsal rough surface for proximal-pole scaphoid-nonunion: a report of 15 patients

Clinical outcomes of the dorsal-retrograde headless screw-fixation technique in 15 patients with proximal scaphoid nonunion are presented. In this technique, screws are inserted from the dorsal rough surface of the scaphoid, located between the dorsal ridge and scaphoid-trapezium-trapezoid joint. Fifteen patients underwent osteosynthesis with this technique with iliac bone graft. Seven patients required primary surgery, and eight patients with a history of failed operation required revision surgery. Among 15 patients, 13 achieved union and two with persistent nonunion were asymptomatic with average follow-up of 24 months (range 14-57). Mean time to union was 20 weeks (range 12-40). Our experience with the dorsal-retrograde headless screw fixation technique has shown encouraging results for the treatment of proximal-scaphoid nonunion, especially in revision surgery wherein secure fixation of the small proximal fragments can be difficult using conventional anterograde techniques.Level of evidence: IV.

Simultaneous Recruitment of Stem Cells and Chondrocytes Induced by a Functionalized Self-Assembling Peptide Hydrogel Improves Endogenous Cartilage Regeneration

The goal of treating articular cartilage (AC) injury is to regenerate cartilage tissue and to integrate the neo-cartilage with surrounding host cartilage. However, most current studies tend to focus on engineering cartilage; interface integration has been somewhat neglected. An endogenous regenerative strategy that simultaneously increases the recruitment of bone marrow mesenchymal stem cells (BMSCs) and chondrocytes may improve interface integration and cartilage regeneration. In this study, a novel functionalized self-assembling peptide hydrogel (KLD-12/KLD-12-LPP, KLPP) containing link protein N-peptide (LPP) was designed to optimize cartilage repair. KLPP hydrogel was characterized using transmission electron microscopy (TEM) and rheometry. KLPP hydrogel shared a similar microstructure to KLD-12 hydrogel which possesses a nanostructure with a fiber diameter of 25–35 nm. In vitro experiments showed that KLPP hydrogel had little cytotoxicity, and significantly induced chondrocyte migration and increased BMSC migration compared to KLD-12 hydrogel. In vivo results showed that defects treated with KLPP hydrogel had higher overall International Cartilage Repair Society (ICRS) scores, Safranin-O staining scores and cumulative histology scores than untreated defects or defects treated with KLD-12 hydrogel, although defects treated with KLD-12 and KLPP hydrogels received similar type II collagen immunostaining scores. All these findings indicated that the simple injectable functionalized self-assembling peptide hydrogel KLPP facilitated simultaneous recruitment of endogenous chondrocytes and BMSCs to promote interface integration and improve cartilage regeneration, holding great potential as a one-step surgery strategy for endogenous cartilage repair.

Kartogenin-loaded coaxial PGS/PCL aligned nanofibers for cartilage tissue engineering

Electrospinning is a valuable technology for cartilage tissue engineering (CTE) due to its ability to produce fibrous scaffolds mimicking the nanoscale and alignment of collagen fibers present within the superficial zone of articular cartilage. Coaxial electrospinning allows the fabrication of core-shell fibers able to incorporate and release bioactive molecules (e.g., drugs or growth factors) in a controlled manner. Herein, we used coaxial electrospinning to produce coaxial poly(glycerol sebacate) (PGS)/poly(caprolactone) (PCL) aligned nanofibers (core:PGS/shell:PCL). The obtained scaffolds were characterized in terms of their structure, chemical composition, thermal properties, mechanical performance and in vitro degradation kinetics, in comparison to monoaxial PCL aligned fibers and respective non-aligned controls. All the electrospun scaffolds produced presented average fiber diameters within the nanometer-scale and the core-shell structure of the composite fibers was clearly confirmed by TEM. Additionally, fiber alignment significantly increased (>2-fold) the elastic modulus of both coaxial and monoxial scaffolds. Kartogenin (KGN), a small molecule known to promote mesenchymal stem/stromal cells (MSC) chondrogenesis, was loaded into the core PGS solution to generate coaxial PGS-KGN/PCL nanofibers. The KGN release kinetics and scaffold biological performance were evaluated in comparison to KGN-loaded monoaxial fibers and respective non-loaded controls. Coaxial PGS-KGN/PCL nanofibers showed a more controlled and sustained KGN release over 21 days than monoaxial PCL-KGN nanofibers. When cultured with human bone marrow MSC in incomplete chondrogenic medium (without TGF-β3), KGN-loaded scaffolds enhanced significantly cell proliferation and chondrogenic differentiation, as suggested by the increased sGAG amounts and chondrogenic markers gene expression levels. Overall, these findings highlight the potential of using coaxial PGS-KGN/PCL aligned nanofibers as a bioactive scaffold for CTE applications.

Photopolymerizable gelatin and hyaluronic acid for stereolithographic 3D bioprinting of tissue-engineered cartilage

To create artificial cartilage in vitro, mimicking the function of native extracellular matrix (ECM) and morphological cartilage-like shape is essential. The interplay of cell patterning and matrix concentration has high impact on the phenotype and viability of the printed cells. To advance the capabilities of cartilage bioprinting, we investigated different ECMs to create an in vitro chondrocyte niche. Therefore, we used methacrylated gelatin (GelMA) and methacrylated hyaluronic acid (HAMA) in a stereolithographic bioprinting approach. Both materials have been shown to support cartilage ECM formation and recovery of chondrocyte phenotype. We used these materials as bioinks to create cartilage models with varying chondrocyte densities. The models maintained shape, viability, and homogenous cell distribution over 14 days in culture. Chondrogenic differentiation was demonstrated by cartilage-typical proteoglycan and type II collagen deposition and gene expression (COL2A1, ACAN) after 14 days of culture. The differentiation pattern was influenced by cell density. A high cell density print (25 × 106  cells/mL) led to enhanced cartilage-typical zonal segmentation compared to cultures with lower cell density (5 × 106  cells/mL). Compared to HAMA, GelMA resulted in a higher expression of COL1A1, typical for a more premature chondrocyte phenotype. Both bioinks are feasible for printing in vitro cartilage with varying differentiation patterns and ECM organization depending on starting cell density and chosen bioink. The presented technique could find application in the creation of cartilage models and in the treatment of articular cartilage defects using autologous material and adjusting the bioprinted constructs size and shape to the patient. © 2019 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2649-2657, 2019.

Minimally Manipulated Mesenchymal Stem Cells for the Treatment of Knee Osteoarthritis: A Systematic Review of Clinical Evidence

Background

The use of laboratory-expanded mesenchymal stem cells (MSCs) is subject to several restrictions, resulting in “minimal manipulation” methods becoming the current most popular strategy to increase the use of MSCs in an orthopaedic practice. The aim of the present systematic review is to assess the clinical applications of “minimally” manipulated MSCs, either as bone marrow aspirate concentrate (BMAC) or as stromal vascular fraction (SVF), in the treatment of knee osteoarthritis (OA).

Methods

A systematic review of three databases (PubMed, ScienceDirect, and Google Scholar) was performed using the following keywords: “Knee Osteoarthritis” with “(Bone marrow aspirate) OR (bone marrow concentrate)” or with “(adipose-derived mesenchymal stem cells) OR (adipose derived stromal cells) OR (stromal vascular fraction) OR (SVF)” as either keywords or MeSH terms. The reference lists of all retrieved articles were further reviewed for identification of potentially relevant studies.

Results

Twenty-three papers were included in the final analysis (10 on BMAC and 13 on SVF). Of these, only 4 were randomized controlled trials (RCTs). Bias risk evaluation, performed using a modified Coleman score, revealed an overall poor quality of the studies. In terms of clinical application, despite the apparent safety of minimally manipulated MSCs and the short-term positive clinical outcomes associated with their use, clinicians reported different preparation and administration methods, ranging from single intra-articular injections to intraosseous applications to administration in combination with other surgical procedures.

Conclusions

The available literature is undermined by both the lack of high-quality studies and the varied clinical settings and different protocols reported in the few RCTs presently published. This prevents any recommendation on the use of either product in a clinical practice. Nevertheless, the use of minimally manipulated MSCs (in the form of BMAC or SVF) has been shown to be safe and have some short-term beneficial effects.

Adipose-Derived Stem Cell Treatments and Formulations

This article analyzes the current literature on the use of adipose-derived stem cells (ASCs) to evaluate the available evidence regarding their therapeutic potential in the treatment of cartilage pathology. Seventeen articles were included and analyzed, showing that there is overall a lack of high-quality evidence concerning the use of ASCs. Most trials are case series with short-term evaluation. The most adopted approach consists of an intra-articular injection of the stromal vascular fraction (SVF) rather than the expanded cells. Based on the available data, no specific preparation method or formulation could be considered as the preferred choice in clinical practice.

Micro Screw Fixation for Small Proximal Pole Scaphoid Fractures with Distal Radius Bone Graft

Background  Achieving adequate fixation and healing of small proximal pole acute scaphoid fractures can be surgically challenging due to both fragment size and tenuous vascularity. Purpose  The purpose of this study was to demonstrate that this injury can be managed successfully with osteosynthesis using a "micro" small diameter compression screw with distal radius bone graft with leading and trailing screw threads less than 2.8 mm. Patients and Methods  Patients with proximal pole scaphoid fragments comprising less than 20% of the entire scaphoid were included. Fixation was accomplished from a dorsal approach with a micro headless compression screw and distal radius bone graft. Six patients were included. Average follow-up was 44 months (range, 11-92). Results  Mean proximal pole fragment size was 14% (range, 9-18%) of the entire scaphoid. The mean immobilization time was 6 weeks, time-to-union of 6 weeks, and final flexion/extension arc of 88°/87°. All patients had a successful union, and no patient had deterioration in range of motion, avascular necrosis, or fragmentation of the proximal pole. Conclusion  Small diameter screws with a maximal thread diameter of ≤ 2.8 mm can be used to fix the union of proximal pole acute scaphoid fractures comprising less than 20% of the total area with good success. Level of Evidence  Therapeutic case series, Level IV.

Nonvascularized Cartilage Grafts Versus Vascularized Cartilage Flaps: Comparison of Cartilage Quality 6 Months After Transfer

PURPOSE

Subchondral perfusion of osteochondral grafts has been shown to be important in preventing long-term cartilage degeneration. In carpal reconstruction, subchondral perfusion from the graft bed is limited. This study's purpose was to compare the histological characteristics of cartilage in osteochondral grafts supported by synovial imbibition alone to cartilage of vascularized osteochondral flaps that have both synovial and vascular pedicle perfusion.

METHODS

Two adjacent osteochondral segments were harvested on the medial femoral trochlea in domestic 6- to 8-month-old pigs. Each segment measured approximately 12 mm × 15 mm × 17 mm. One segment was maintained on the descending geniculate artery vascular pedicle. The adjacent segment was separated from the pedicle to serve as a nonvascularized graft. A thin layer of methylmethacrylate cement was used to line the harvest site defect to prevent vascular ingrowth to the subsequently replaced specimens. The pigs were maintained on a high-calorie feed and returned to ambulation and full weight-bearing on the surgical legs. The animals were sacrificed after 6 months and the specimens were reharvested, sectioned, and examined. The cartilage was graded by 2 pathologists blinded to the origin of specimens as vascularized flaps or nonvascularized grafts.

RESULTS

All specimens were assigned scores utilizing the International Cartilage Repair Society grading system. Scoring for chondrocyte viability, cartilage surface morphology, and cell and matrix appearance was significantly higher in the vascularized osteochondral group than in the graft group.

CONCLUSIONS

When deprived of subchondral perfusion from underlying bone, osteochondral vascularized flaps in an intrasynovial environment demonstrate superior cartilage quality and survival compared with nonvascularized grafts.

CLINICAL RELEVANCE

In locations in which perfusion from surrounding bone may be limited (ie, proximal scaphoid or proximal lunate reconstruction), articular reconstruction using vascularized osteochondral flaps will yield superior cartilage organization and architecture than nonvascularized osteochondral grafts. The clinical and functional relevance of this finding requires further study.

Wnt signaling in cartilage development and diseases: lessons from animal studies

Cartilage not only plays essential roles in skeletal development and growth during pre- and postnatal stages but also serves to provide smooth movement of skeletons throughout life. Thus, dysfunction of cartilage causes a variety of skeletal disorders. Results from animal studies reveal that β-catenin-dependent canonical and independent non-canonical Wnt signaling pathways have multiple roles in regulation of cartilage development, growth, and maintenance. β-Catenin-dependent signaling is required for progression of endochondral ossification and growth of axial and appendicular skeletons, while excessive activation of this signaling can cause severe inhibition of initial cartilage formation and growth plate organization and function in mice. In contrast, non-canonical Wnt signaling is important in columnar organization of growth plate chondrocytes. Manipulation of Wnt signaling causes or ameliorates articular cartilage degeneration in rodent osteoarthritis models. Human genetic studies indicate that Wnt/β-catenin signaling is a risk factor for osteoarthritis. Accumulative findings from analysis of expression of Wnt signaling molecules and in vivo and in vitro functional experiments suggest that Wnt signaling is a therapeutic target for osteoarthritis. The target tissues of Wnt signaling may be not only articular cartilage but also synovium and subchondral bone.

Mechanical properties and structure-function relationships in articular cartilage repaired using IGF-I gene-enhanced chondrocytes

Several studies have demonstrated the benefits of IGF-I gene therapy in enhancing the histologic and biochemical content of cartilage repaired by chondrocyte transplantation. However, there is little to no data on the mechanical performance of IGF-I augmented cartilage grafts. This study evaluated the compressive properties of full-thickness chondral defects in the equine femur repaired with and without IGF-I gene therapy. Animals were randomly assigned to one of three study cohorts based on chondrocyte treatment provided in each defect: (i) IGF-I gene delivered by recombinant adeno-associated virus (rAAV)-5; (ii) AAV-5 delivering GFP as a reporter; (iii) naïve cells without virus. In each case, the opposite limb was implanted with a fibrin carrier without cells. Samples were prepared for confined compression testing to measure the aggregate modulus and hydraulic permeability. All treatment groups, regardless of cell content or transduction, had mechanical properties inferior to native cartilage. Overexpression of IGF-I increased modulus and lowered permeability relative to other treatments. Investigation of structure-property relationships revealed that Ha and k were linearly correlated with GAG content but logarithmically correlated with collagen content. This provides evidence that IGF-I gene therapy can improve healing of articular cartilage and can greatly increase the mechanical properties of repaired grafts.

Fabrication of poly(ester-urethane)urea elastomer/gelatin electrospun nanofibrous membranes for potential applications in skin tissue engineering

In this study, PEUU was blended with gelatin for electrospun nanofiber and nanoyarn. PEUU/gelatin with a mass ratio of 75 : 25 showed better comprehensive property than nanofiber thus paving way for the further research in tissue engineering field.

Resident mesenchymal progenitors of articular cartilage

Articular cartilage has poor capacity of self-renewal and repair. Insufficient number and activity of resident mesenchymal (connective tissue) progenitors is likely one of the underlying reasons. Chondroprogenitors reside not only in the superficial zone of articular cartilage but also in other zones of articular cartilage and in the neighboring tissues, including perichondrium (groove of Ranvier), synovium and fat pad. These cells may respond to injury and contribute to articular cartilage healing. In addition, marrow stromal cells can migrate through subchondral bone when articular cartilage is damaged. We should develop drugs and methods that correctly stimulate resident progenitors for improvement of repair and inhibition of degenerative changes in articular cartilage.

Experimental chondrocyte hypertrophy is promoted by the activation of discoidin domain receptor 2

The aim of the present study was to assess the association between chondrocytes and the extracellular matrix (ECM), and determine whether this contributes to osteoarthritis (OA). Chondrocyte hypertrophy was measured in articular cartilage samples from early-stage OA patients. In addition, rat chondrocytes were cultured and divided into four groups (A to D): Group A was an untreated control group, group B was incubated with chicken collagen II, group C was transfected with the discoidin domain of discoidin domain receptor-2 (DDR2) and group D was transfected with full‑length DDR2. The expression levels of DDR2 and hypertrophic markers in each group were then measured by quantitative polymerase chain reaction (qPCR) and western blot analyses. Chondrocyte hypertrophy was identified in samples of early‑stage OA patients. In rat chondrocyte cultures, the relative mRNA and protein expression levels of hypertrophic markers were determined as: Group D > B > C > A. In conclusion, transfection with DDR2 induced the expression of hypertrophic markers, as assessed by qPCR and western blot analyses. DDR2 therefore promoted chondrocyte hypertrophy and terminal differentiation.

A new building block: costo-osteochondral graft for intra-articular incongruity after distal radius fracture

Even with the invention of locking plates, intra-articular fractures of distal radius with extreme comminution remain a challenge for orthopaedic surgeons. Osteochondral graft is a potential choice to reconstruct the articular defect. We report a patient who had a fracture of distal radius with costo-osteochondral graft for articular reconstruction which has not yet been described in the English literature. At nine-year follow-up, he was pain free and had full range of movement of the wrist. The authors suggest that costo-osteochondral graft could be an option with satisfactory result.

Toward regeneration of articular cartilage

Articular cartilage is classified as permanent hyaline cartilage and has significant differences in structure, extracelluar matrix components, gene expression profile, and mechanical property from transient hyaline cartilage found in the epiphyseal growth plate. In the process of synovial joint development, articular cartilage originates from the interzone, developing at the edge of the cartilaginous anlagen, and establishes zonal structure over time and supports smooth movement of the synovial joint through life. The cascade actions of key regulators, such as Wnts, GDF5, Erg, and PTHLH, coordinate sequential steps of articular cartilage formation. Articular chondrocytes are restrictedly controlled not to differentiate into a hypertrophic stage by autocrine and paracrine factors and extracellular matrix microenvironment, but retain potential to undergo hypertrophy. The basal calcified zone of articular cartilage is connected with subchondral bone, but not invaded by blood vessels nor replaced by bone, which is highly contrasted with the growth plate. Articular cartilage has limited regenerative capacity, but likely possesses and potentially uses intrinsic stem cell source in the superficial layer, Ranvier's groove, the intra-articular tissues such as synovium and fat pad, and marrow below the subchondral bone. Considering the biological views on articular cartilage, several important points are raised for regeneration of articular cartilage. We should evaluate the nature of regenerated cartilage as permanent hyaline cartilage and not just hyaline cartilage. We should study how a hypertrophic phenotype of transplanted cells can be lastingly suppressed in regenerating tissue. Furthermore, we should develop the methods and reagents to activate recruitment of intrinsic stem/progenitor cells into the damaged site.

Evaluation of oriented electrospun fibers for periosteal flap regeneration in biomimetic triphasic osteochondral implant

Osteochondral defects represent a serious clinical problem. Although the cell-scaffold complexes have been reported to be effective for repairing osteochondral defects, a periosteal flap is frequently needed to arrest leakage of the implanted cells into the defect and to contribute to the secretion of cytokines to stimulate cartilage repair. The electrospun mesh mimicking the function of the flap assists tissue regeneration by preventing cell leakage and merits favorable outcomes in the cartilaginous region. In this study, an oriented poly(ε-caprolactone) (PCL) fibrous membrane (OEM) was fabricated by electrospinning as a periosteal scaffold and then freeze-dried with a collagen type I and hyaluronic acid cartilage scaffold (CH) and finally, freeze-dried with a tricalcium phosphate (TCP) bone substratum. Scanning electron microscopic images show obvious microstructure formation of the trilayered scaffolds, and electrospun fibrous membranes have an oriented fibrous network structure for the periosteal phase. Also shown are opened and interconnected pores with well designed three-dimensional structure, able to be bound in the CH (chondral phase) and TCP (osseous phase) scaffolds. In vitro results showed that the OEM can promote the orientation of bone marrow mesenchymal stem cell (BMSCs) and BMSCs can penetrate into the CH and TCP. After successfully combining the BMSCs, the tissue-engineered cartilage which contained the OEM and TCP complex was successfully used to regenerate the osteochondral defects in the rabbit model with greatly improved repair effects.

Scaphoid overstuffing: the effects of the dimensions of scaphoid reconstruction on scapholunate alignment

PURPOSE

Osteochondral replacement of the proximal scaphoid has been reported using a vascularized flap from the medial femoral trochlea. A concern with this technique is the loss of stability of the scapholunate relationship with resection of the scaphoid proximal pole. Overexpansion of the scaphoid dimensions (overstuffing) during scaphoid reconstruction with the osteochondral flap may play a role in maintaining scapholunate alignment. Our purpose was to determine if overstuffing the scaphoid can correct rotatory carpal instability in a cadaveric model studied radiographically.

METHODS

The radiolunate angle and scapholunate interval were measured for 5 fresh cadaver wrists. We completely incised the scapholunate interosseous ligament and performed an osteotomy to excise the proximal third of the scaphoid to simulate a proximal pole deficiency nonunion and create a dorsal intercalated segmental instability deformity. Radiographic measurements were repeated. The proximal pole of the scaphoid was replaced with its original piece of bone; radiographic measurements were repeated without scapholunate ligament repair. The osteotomy site was overstuffed with a 4-mm sawbone spacer without scapholunate ligament repair, and radiographs were obtained.

RESULTS

Sectioning of scapholunate ligaments and proximal pole excision successfully created carpal instability demonstrated by abnormal radiolunate angles. Without ligament repair, proximal pole replacement did not restore normal radiolunate angles. Expansion of the scaphoid dimensions corrected radiolunate angles on lateral unloaded radiographs and improved scapholunate intervals on clenched fist radiographs. These findings were statistically significant compared with the unexpanded (replaced) scaphoid.

CONCLUSIONS

These findings suggest that scaphoid reconstruction that results in expansion of the scaphoid's normal dimensions will restore carpal alignment without scapholunate ligament reconstruction.

CLINICAL RELEVANCE

Osteochondral reconstruction of difficult proximal pole nonunions may not require any preservation or reconstruction of scapholunate integrity if the reconstruction expands the normal dimensions of the native scaphoid. Scapholunate interval and carpal alignment may be restored by scaphoid over stuffing. The effects on increased contact pressure and range of motion require further investigation.

Vascularized graft from the metatarsal base for reconstructing major osteochondral distal radius defects

PURPOSE

To present our experience of reconstructing distal radius articular defects with a vascularized osteochondral graft from the metatarsal base and to present the mid-term outcomes.

METHODS

Seven patients (average age, 36 y; range, 26-55 y) who had reconstruction of major defects of the articular surface of the radius are presented. In 5, the lunate facet and sigmoid notch were reconstructed; in 1, an isolated defect on the surface of the lunate facet was reconstructed; and in 1, the scaphoid facet was reconstructed. In 6, the base of the third metatarsal was transferred, and in 1, the base of the second was transferred.

RESULTS

All flaps survived without complications. At the latest follow-up (range, 20 mo to 8 y), the flexion-extension arc improved an average of 50°, and the pain on a visual analog scale decreased from 8 to 1 on average. Disabilities of the Arm, Shoulder, and Hand score improved from 54 to 11 on average. One patient did not improve. No major complaints related to the donor site were mentioned (average American Orthopedic Foot and Ankle Society score of 96/100).

CONCLUSIONS

Our mid-term results are promising; however, the decision-making process and the operation are complex. The operation is not indicated when the carpals are devoid of cartilage or when the defect involves the whole radius surface.

Potential of Raloxifene in reversing osteoarthritis-like alterations in rat chondrocytes: an in vitro model study

The aim of this study was to investigate the effects of Raloxifene (Ral) on degeneration-related changes in osteoarthritis (OA)-like chondrocytes using two- and three-dimensional models. Five-azacytidine (Aza-C) was used to induce OA-like alterations in rat articular chondrocytes and the model was verified at molecular and macrolevels. Chondrocytes were treated with Ral (1, 5 and 10 mu M) for 10 days. Caspase-3 activity, gene expressions of aggrecan, collagen II, alkaline phosphatase (ALP), collagen X, matrix metalloproteinases (MMP-13, MMP-3 and MMP-2), and MMP-13, MMP-3 and MMP-2 protein expressions were studied in two-dimensional model. Matrix deposition and mechanical properties of agarose-chondrocyte discs were evaluated in three-dimensional model. One mu M Ral reduced expression of OA-related genes, decreased apoptosis, and MMP-13 and MMP-3 protein expressions. It also increased aggrecan and collagen II gene expressions relative to untreated OA-like chondrocytes. In three-dimensional model, 1 mu M Ral treatment resulted in increased collagen deposition and improved mechanical properties, although a significant increase for sGAG was not observed. In summation, 1 mu M Ral improved matrix-related activities, whereas dose increment reversed these effects except ALP gene expression and sGAG deposition. These results provide evidence that low-dose Ral has the potential to cease or reduce the matrix degeneration in OA.

Vascularized medial femoral trochlea osteocartilaginous flap reconstruction of proximal pole scaphoid nonunions

PURPOSE

The descending geniculate artery's branching pattern includes periosteal vessels supplying the cartilage-bearing trochlea of the medial patellofemoral joint. Previous cadaveric studies described anatomic similarities between the greater curvature of the proximal scaphoid and the convex surface of the medial femoral trochlea (MFT). We describe the technique and report our first 16 consecutive cases of vascularized osteocartilaginous arthroplasty for chronic scaphoid proximal pole nonunions using the MFT, with a minimum of 6 months of follow-up.

METHODS

Chart reviews of 16 consecutive cases of osteocartilaginous MFT flap transfers for scaphoid reconstruction were performed at 2 institutions. Follow-up data were recorded at a minimum of 6 months, with an average of 14 months (range, 6-72 mo). Patient age and sex, duration of nonunion, number of previous surgical procedures, surgical technique, achievement of osseous union, preoperative and postoperative scapholunate angles, preoperative and postoperative range of motion, and pain relief were recorded.

RESULTS

Computed tomography imaging confirmed healing in 15 of 16 reconstructed scaphoids. Mean patient age was 30 years (range, 18-47 y). The average number of previous surgical procedures was 1 (range, 0-3). All patients experienced some wrist pain improvement (12/16 complete relief, 4/16 incomplete relief). Wrist range of motion at follow-up averaged 46° extension (range, 28° to 80°) and 44° flexion (range, 10° to 80°), which was similar to preoperative measurements (average 46° extension and 43° flexion). Scapholunate relationship remained unchanged with average scapholunate angles of 52° before surgery and 49° after surgery.

CONCLUSIONS

Osteochondral vascularized MFT flaps provide a reliable means of achieving resolution of difficult proximal pole scaphoid nonunions. These flaps allow resection of the proximal portion of the unhealed scaphoid and reconstruction with an anatomically analogous convex segment of cartilage-bearing bone. This technique provides the advantages of vascularized bone and ease of fixation. Early follow-up demonstrates a high rate of union with acceptable motion and pain relief.

CLINICAL RELEVANCE

Early follow-up suggests that the vascularized MFT osteocartilaginous flap is a valuable tool for treating challenging proximal pole scaphoid nonunions.

The impact of PLGA scaffold orientation on in vitro cartilage regeneration

The success of in vitro cartilage regeneration provides a promising approach for cartilage repair. However, the currently engineered cartilage in vitro is unsatisfactory for clinical application due to non-homogeneous structure, inadequate thickness, and poor mechanical property. It has been widely reported that orientation of scaffolds can promote cell migration and thus probably contributes to improving tissue regeneration. This study explored the impact of microtubular oriented scaffold on in vitro cartilage regeneration. Porcine articular chondrocytes were seeded into microtubule-oriented PLGA scaffolds and non-oriented scaffolds respectively. A long-term in vitro culture followed by a long-term in vivo implantation was performed to evaluate the influence of scaffold orientation on cartilage regeneration. The current results showed that the oriented scaffolds could efficiently promote cell migration towards the inner region of the constructs. After 12 weeks of in vitro culture, the chondrocyte-scaffold constructs in the oriented group formed thicker cartilage with more homogeneous structure, stronger mechanical property, and higher cartilage matrix content compared to the non-oriented group. Furthermore, the in vitro engineered cartilage based on oriented scaffolds showed better cartilage formation in terms of size, wet weight, and homogeneity after 12-week in vivo implantation in nude mice. These results indicated that the longitudinal microtubular orientation of scaffolds can efficiently improve the structure and function of in vitro engineered cartilage.

Equine Models of Articular Cartilage Repair

Articular cartilage injuries of the knee and ankle are common, and a number of different methods have been developed in an attempt to improve their repair. Clinically, there are 2 distinct aims of cartilage repair: 1) restoration of joint function and 2) prevention or at least delay of the onset of osteoarthritis. These goals can potentially be achieved through replacement of damaged or lost articular cartilage with tissue capable of functioning under normal physiological environments for an extended period, but limitations of the final repair product have long been recognized and still exist today. Screening of potential procedures for human clinical use is done by preclinical studies using animal models. This article reviews equine chondral defect models that have been recently recognized to have specific advantages for translation into human articular cartilage regeneration. Defect models in the femoropatellar, femorotibial, and tibiotalar joints have been developed. The horse provides the closest approximation to humans in terms of articular cartilage and subchondral bone thickness, and it is possible to selectively leave the entire calcified cartilage layer or completely remove it. The defect on the equine medial femoral condyle emulates medial femoral condylar lesions in humans. Other advantages of the equine model include an ability to use an arthroscope to create lesions and perform second-look arthroscopies, the large lesion size allowing for more tissue for evaluation, and the ability to have controlled exercise and test the ability of the repair to cope with athletic exercise as well as institute rehabilitation regimens.

Periosteum as a source of mesenchymal stem cells: the effects of TGF-β3 on chondrogenesis

INTRODUCTION

Numerous experimental efforts have been undertaken to induce the healing of lesions within articular cartilage by re-establishing competent repair tissue. Adult mesenchymal stem cells have attracted attention as a source of cells for cartilage tissue engineering. The purpose of this study was to investigate chondrogenesis employing periosteal mesenchymal cells.

METHODS

Periosteum was harvested from patients who underwent orthopedic surgeries. Mesenchymal stem cells were characterized through flow cytometry using specific antibodies. The stem cells were divided into four groups. Two groups were stimulated with transforming growth factor β3 (TGF-β3), of which one group was cultivated in a monolayer culture and the other was cultured in a micromass culture. The remaining two groups were cultivated in monolayer or micromass cultures in the absence of TGF-β3. Cell differentiation was verified through quantitative reverse transcription-polymerase chain reaction (RT-PCR) and using western blot analysis.

RESULT

In the groups cultured without TGF-β3, only the cells maintained in the micromass culture expressed type II collagen. Both the monolayer and the micromass groups that were stimulated with TGF-β3 expressed type II collagen, which was observed in both quantitative RT-PCR and western blot analysis. The expression of type II collagen was significantly greater in the micromass system than in the monolayer system.

CONCLUSION

The results of this study demonstrate that the interactions between the cells in the micromass culture system can regulate the proliferation and differentiation of periosteal mesenchymal cells during chondrogenesis and that this effect is enhanced by TGF-β3.

Developmental mechanisms in articular cartilage degradation in osteoarthritis

Osteoarthritis is the most common arthritic condition, which involves progressive degeneration of articular cartilage. The most recent accomplishments have significantly advanced our understanding on the mechanisms of the disease development and progression. The most intriguing is the growing evidence indicating that extracellular matrix destruction in osteoarthritic articular cartilage resembles that in the hypertrophic zone of fetal growth plate during endochondral ossification. This suggests common regulatory mechanisms of matrix degradation in OA and in the development and can provide new approaches for the treatment of the disease by targeting reparation of chondrocyte phenotype.

In vitro investigation and biomechanical modeling of the effects of PLF-68 on osteoarthritis in a three-dimensional model

In this study, it was hypothesized that Pluronic F-68 (PLF-68) increases matrix synthesis of osteoarthritis (OA) chondrocytes in addition to its well-documented cell survival effect. To test this hypothesis, rat articular chondrocytes were embedded in agarose discs and were exposed to 5-azacytidine (Aza-C) to induce OA-like alterations. Chondrocytes were then treated with PLF-68 (8 and 12 mg/ml) for 10 days. Aza-C-exposed and PLF-68-untreated chondrocytes and Aza-C-unexposed and PLF-68-untreated chondrocytes were used as negative and positive control groups, respectively. Dynamic hydrostatic pressure (max 0.2 MPa, 0.1 Hz) was applied to discs for 30 min/day (5 days/week). Cell viability, collagen and proteoglycan deposition in discs were determined. Unconfined compression stress relaxation tests were performed to determine peak stress and material parameters of discs--namely spring constants (k (1) and k (2)), damping coefficient (η), instantaneous modulus (E (0)) and relaxed modulus (E (∞)) using Kelvin model to evaluate the functional coherence of the matrix. PLF-68 treatment significantly increased the collagen deposition in discs and viability of OA-like chondrocytes. A dose-dependent increase was also observed for elastic stiffness parameters (k (1), k (2), E (0) and E (∞)). Same positive effect of PLF-68 was not observed for proteoglycan deposition. However, dose-dependent increase in η suggests that PLF-68 treatment resulted with the deposition of functional matrix. This is the first study which reports that PLF-68 has also positive effect on collagen synthesis of OA cells. As a conclusion, our results suggest that PLF-68 has a potential for recovery from OA-like alterations, which should be further analyzed.

A new histology scoring system for the assessment of the quality of human cartilage repair: ICRS II

BACKGROUND

A reliable and reproducible method is needed to assess cartilage repair.

PURPOSE

This study was undertaken to test the reproducibility of 2 established histological scoring systems, the Modified O'Driscoll Scale (MODS) and International Cartilage Research Society (ICRS) Visual Assessment Scale (ICRS I), and subsequently to develop and evaluate a new grading system for cartilage repair.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 107 cartilage biopsy specimens were graded using MODS and ICRS I, and the reader variability was measured. The new grading system, ICRS II, was developed and the inter- and intrareader variability determined by 3 independent readers. Collagen type II deposition was assessed immunohistochemically.

RESULTS

The MODS and ICRS I demonstrated high interreader variability, with MODS also showing high intrareader variability. A new histological scoring system, ICRS II, was developed comprising 14 criteria to assess parameters related to chondrocyte phenotype and tissue structure. The ICRS II demonstrated lower inter- and intrareader variability compared with MODS or ICRS I. The overall assessment and matrix staining scores had the best correlation coefficients for inter- and intrareader variability (r = .81 and .82, respectively). The extent of collagen type II in cartilage, considered a marker of differentiation toward hyaline cartilage, could represent a measure of good cartilage repair. A correlation coefficient of .56 was obtained between the extent of collagen type II staining and the overall assessment score.

CONCLUSION

The ICRS II represents an improvement over current histological cartilage repair grading systems in terms of reader reproducibility. The clinical relevance and its ability to predict long-term repair durability will be assessed once long-term clinical data become available.

Shear stress magnitude and duration modulates matrix composition and tensile mechanical properties in engineered cartilaginous tissue

Cartilage tissue-engineering strategies aim to produce a functional extracellular matrix similar to that of the native tissue. However, none of the myriad approaches taken have successfully generated a construct possessing the structure, composition, and mechanical properties of healthy articular cartilage. One possible approach to modulating the matrix composition and mechanical properties of engineered tissues is through the use of bioreactor-driven mechanical stimulation. In this study, we hypothesized that exposing scaffold-free cartilaginous tissue constructs to 7 days of continuous shear stress at 0.001 or 0.1 Pa would increase collagen deposition and tensile mechanical properties compared to that of static controls. Histologically, type II collagen staining was evident in all construct groups, while a surface layer of type I collagen increased in thickness with increasing shear stress magnitude. The areal fraction of type I collagen was higher in the 0.1-Pa group (25.2 +/- 2.2%) than either the 0.001-Pa (13.6 +/- 3.8%) or the static (7.9 +/- 1.5%) group. Type II collagen content, as assessed by ELISA, was also higher in the 0.1-Pa group (7.5 +/- 2.1%) compared to the 0.001-Pa (3.0 +/- 2.25%) or static groups (3.7 +/- 3.2%). Temporal gene expression analysis showed a flow-induced increase in type I and type II collagen expression within 24 h of exposure. Interestingly, while the 0.1-Pa group showed higher collagen content, this group retained less sulfated glycosaminoglycans in the matrix over time in bioreactor culture. Increases in both tensile Young's modulus and ultimate strength were observed with increasing shear stress, yielding constructs possessing a modulus of nearly 5 MPa and strength of 1.3 MPa. This study demonstrates that shear stress is a potent modulator of both the amount and type of synthesized extracellular matrix constituents in engineered cartilaginous tissue with corresponding effects on mechanical function.

Chondrogenic differentiation of human mesenchymal stem cells on oriented nanofibrous scaffolds: engineering the superficial zone of articular cartilage

Cell differentiation, adhesion, and orientation are known to influence the functionality of both natural and engineered tissues, such as articular cartilage. Several attempts have been devised to regulate these important cellular behaviors, including application of inexpensive but efficient electrospinning that can produce patterned extracellular matrix (ECM) features. Electrospun and oriented polycaprolactone (PCL) scaffolds (500 or 3000 nm fiber diameter) were created, and human mesenchymal stem cells (hMSCs) were cultured on these scaffolds. Cell viability, morphology, and orientation on the fibrous scaffolds were quantitatively determined as a function of time. While the fiber-guided initial cell orientation was maintained even after 5 weeks, cells cultured in the chondrogenic media proliferated and differentiated into the chondrogenic lineage, suggesting that cell orientation is controlled by the physical cues and minimally influenced by the soluble factors. Based on assessment by the chondrogenic markers, use of the nanofibrous scaffold (500 nm) appears to enhance the chondrogenic differentiation. These findings indicate that hMSCs seeded on a controllable PCL scaffold may lead to an alternate methodology to mimic the cell and ECM organization that is found, for example, in the superficial zone of articular cartilage.

Matrix-induced autologous chondrocyte implantation in sheep: objective assessments including confocal arthroscopy

The assessment of cartilage repair has largely been limited to macroscopic observation, magnetic resonance imaging (MRI), or destructive biopsy. The aims of this study were to establish an ovine model of articular cartilage injury repair and to examine the efficacy of nondestructive techniques for assessing cartilage regeneration by matrix-induced autologous chondrocyte implantation (MACI). The development of nondestructive assessment techniques facilitates the monitoring of repair treatments in both experimental animal models and human clinical subjects. Defects (Ø 6 mm) were created on the trochlea and medial femoral condyle of 21 sheep randomized into untreated controls or one of two treatment arms: MACI or collagen-only membrane. Each group was divided into 8-, 10-, and 12-week time points. Repair outcomes were examined using laser scanning confocal arthroscopy (LSCA), MRI, histology, macroscopic ICRS grading, and biomechanical compression analysis. Interobserver analysis of the randomized blinded scoring of LSCA images validated our scoring protocol. Pearson correlation analysis demonstrated the correlation between LSCA, MRI, and ICRS grading. Testing of overall treatment effect independent of time point revealed significant differences between MACI and control groups for all sites and assessment modalities (Asym Sig < 0.05), except condyle histology. Biomechanical analysis suggests that while MACI tissue may resemble native tissue histologically in the early stages of remodeling, the biomechanical properties remain inferior at least in the short term. This study demonstrates the potential of a multisite sheep model of articular cartilage defect repair and its assessment via nondestructive methods.

Laser scanning confocal arthroscopy of a fresh cadaveric knee joint

OBJECTIVE

Osteoarthritis (OA) inflicts an enormous burden upon sufferers and healthcare systems worldwide. Continuing efforts to elucidate the aetiology of OA have indicated the need for non-destructive methods of in vivo microstructural assessment of articular cartilage (AC). In this study, we describe the first use of a recently developed laser scanning confocal arthroscope (LSCA) to image the cartilage of a fresh frozen cadaveric knee from a patient with OA.

DESIGN

Using an adaptation of the International Cartilage Repair Society (ICRS) joint mapping protocol, the joint was divided into three discrete regions (femoral condyle, patella and tibial plateau) for grading according to the ICRS (Outerbridge) system. The LSCA was used to generate images from each area within the three regions. Following imaging, the joint was sectioned and histology was performed on the corresponding sites with histological grading (modified-Mankin).

RESULTS

Quantitative results of ICRS, LSCA and histological OA assessment were compared using intraclass correlation (ICC) and Pearson correlation analysis. The LSCA enabled visualisation of chondrocyte morphology and cell density, with classical OA changes such as chondrocyte clustering, surface fibrillation and fissure formation evident. Obvious qualitative similarities between LSCA images and histology were observed, with fair to moderate agreement (P<0.05) demonstrated between modalities.

CONCLUSIONS

In this study, we have shown the viability of the LSCA for non-destructive imaging of the microstructure of OA knee cartilage. LSCA technology is potentially a valuable research and clinical tool for the non-destructive assessment of AC microstructure in early to late OA.

Evolving concepts in the management of the bone gap in the upper limb. Long and small defects

Vascularised bone graft is a well accepted technique when dealing with long defects. Its role in refractory nonunion, in small defects and in the growing patient is rarely discussed. In this paper the authors review the different alternatives to deal with bone defects in the upper extremity. The indications of vascularised corticoperiosteal graft for solving small defects harbouring refractory nonunion, and the use of vascularised bone phalanx and metatarsal for complex - but small - defects in the fingers is presented. The ability of the bone to grow and remodel when a living epiphysis is included, and to maintain the cartilage viability when a composite osteochondral graft is transferred are also discussed.

Chondrocyte hypertrophy can be induced by a cryptic sequence of type II collagen and is accompanied by the induction of MMP-13 and collagenase activity: implications for development and arthritis

The objective of this study was to determine whether a peptide of type II collagen which can induce collagenase activity can also induce chondrocyte terminal differentiation (hypertrophy) in articulate cartilage. Full depth explants of normal adult bovine articular cartilage were cultured with or without a 24 mer synthetic peptide of type II collagen (residues 195-218) (CB12-II). Peptide CB12-II lacks any RGD sequence and is derived from the CB12 fragment of type II collagen. Type II collagen cleavage by collagenase was measured by ELISA in cartilage and medium. Real-time RT-PCR was used to analyze gene expression of the chondrocyte hypertrophy markers COL10A1 and MMP-13. Immunostaining for anti-Ki67, anti-PCNA, (proliferation markers), type X collagen, cleavage of type II collagen by collagenases (hypertrophy markers) and TUNEL staining (hypertrophy and apoptosis markers) were used to detect progressive maturational stages of chondrocyte hypertrophy. At high but naturally occurring concentrations (10 microM and up) the collagen peptide CB12-II induced an increase in the expression of MMP-13 (24 h) and cleavage of type II collagen by collagenase in the mid zone (day 4) and also in the superficial zone (day 6). Furthermore the peptide induced an increase in proliferation on day 1 in the mid and deep zones extending to the superficial zone by day 4. There was also upregulation of COL10A1 expression at day 4 and of type X staining in the mid zone extending to the superficial zone by day 6. Apoptotic cell death was increased by day 4 in the lower deep zone and also in the superficial zone at day 7. The increase in apoptosis in the deep zone was also seen in controls. Our results show that the induction of collagenase activity by a cryptic peptide sequence of type II collagen, is accompanied by chondrocyte hypertrophy and associated with cellular and matrix changes. This induction occurs in the mid and superficial zones of previously healthy articular cartilage. This response of the chondrocyte to a cryptic sequence of denatured type II collagen may play a role in naturally occurring hypertrophy in endochondral ossification and in the development of cartilage pathology in osteoarthritis.

Articular cartilage repair by means of biodegradable scaffolds

INTRODUCTION

Articular cartilage has a limited capacity for self-repair; untreated injuries of cartilage may lead to osteoarthritis. In severe cases the only choice a total joint replacement, may be inadequate in young patients. This problem demands new effective methods to reconstruct articular cartilage. The aim of this study was to evaluate the application of collagen matrix for the reconstruction of articular cartilage.

MATERIALS AND METHODS

A group of 28 rabbits had a defect penetrating into the subchondral constructed and either filled with collagen scaffold (group I) or remained empty (group II). The results were observed after 4 and 12 weeks. Macroscopic and microscopic evaluations were performed.

RESULTS

In the first group we observed the presence of hyalinelike cartilage resembling normal articular cartilage. In the second group fibrous tissue dominated. The surface of regenerated tissue was smooth, intact, and the defect completely filled with regenerated tissue, showing good structural integrity. In the second group, superficial irregularities, disorders of structural integrity, and necrotic features were noticed.

CONCLUSIONS

This study showed better results of articular cartilage reconstruction by means of a biodegradable scaffold.

Transforming growth factor-beta2 suppresses collagen cleavage in cultured human osteoarthritic cartilage, reduces expression of genes associated with chondrocyte hypertrophy and degradation, and increases prostaglandin E(2) production

Articular cartilage degeneration in osteoarthritis (OA) involves type II collagen degradation and chondrocyte differentiation (hypertrophy). Because these changes resemble growth plate remodeling, we hypothesized that collagen degradation may be inhibitable by growth factors known to suppress growth plate hypertrophy, namely transforming growth factor (TGF)-beta2, fibroblast growth factor (FGF)-2, and insulin. Full-depth explants of human OA knee articular cartilage from arthroplasty were cultured with TGF-beta2, FGF-2, and insulin in combination (growth factors) or individually. In cultured explants from five OA patients, collagenase-mediated type II collagen cleavage was significantly down-regulated by combined growth factors as measured by enzyme-linked immunosorbent assay. Individually, FGF-2 and insulin failed to inhibit collagen cleavage in some OA explants whereas TGF-beta2 reduced collagen cleavage in these 5 explants and in 19 additional explants. Moreover, TGF-beta2 effectively suppressed cleavage at low concentrations. Together or individually these growth factors did not inhibit glycosaminoglycan (primarily aggrecan) degradation while TGF-beta2 occasionally did. Semiquantitative reverse transcriptase-polymerase chain reaction of articular cartilage from six OA patients revealed that TGF-beta2 suppressed expression of matrix metalloproteinase-13 and matrix metalloproteinase-9, early (PTHrP) and late (COL10A1) differentiation-related genes, and proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha). In contrast, TGF-beta2 up-regulated PGES-1 expression and prostaglandin E(2) release. These observations show that TGF-beta2 can suppress collagen resorption and chondrocyte differentiation in OA cartilage and that this may be mediated by prostaglandin E(2). Therefore TGF-beta2 could provide therapeutic control of type II collagen degeneration in OA.

Reconstruction of the distal radius facet by a free vascularized osteochondral autograft: anatomic study and report of a patient

PURPOSE

Large chondral defects of the distal radius after fractures present a reconstructive challenge. The purpose of this study was to present the anatomic findings from a cadaver of a vascularized osteochondral autograft taken from the third metatarsal appropriate for reconstructing the distal radius articular facet. A patient is presented in whom 70% of the scaphoid fossa was reconstructed with this technique.

METHODS

The base of the third metatarsal was studied in the feet of 20 cadavers. The size and shape of the cartilage were measured. Additionally vessel distribution was recorded and the diameters of vascular foramina were measured with Juch's method.

RESULTS

The base of the third metatarsal is pear shaped and is wider dorsally than plantarly. It averages 19.2 mm long on its main axis. Its cartilaginous surface is minimally concave or flat and it is slanted slightly proximal-dorsal to distal-plantar and proximal-peroneal to distal-tibial. Nutrient foramina were found in every case in the dorsum and on both sides of the proximal shaft. At least 1 nutrient vessel could be tracked back to the dorsalis pedis in every dissected specimen.

CONCLUSIONS

The anatomic features of the base of the third metatarsal make it a potential vascularized autograft to consider for osteochondral defects of the distal radius.

Effects of pulsed electromagnetic fields on articular hyaline cartilage: review of experimental and clinical studies

Osteoarthritis (OA) is the most common disorder of the musculoskeletal system and is a consequence of mechanical and biological events that destabilize tissue homeostasis in articular joints. Controlling chondrocyte death and apoptosis, function, response to anabolic and catabolic stimuli, matrix synthesis or degradation and inflammation is the most important target of potential chondroprotective treatment, aimed to retard or stabilize the progression of OA. Although many drugs or substances have been recently introduced for the treatment of OA, the majority of them relieve pain and increase function, but do not modify the complex pathological processes that occur in these tissues. Pulsed electromagnetic fields (PEMFs) have a number of well-documented physiological effects on cells and tissues including the upregulation of gene expression of members of the transforming growth factor beta super family, the increase in glycosaminoglycan levels, and an anti-inflammatory action. Therefore, there is a strong rationale supporting the in vivo use of biophysical stimulation with PEMFs for the treatment of OA. In the present paper some recent experimental in vitro and in vivo data on the effect of PEMFs on articular cartilage were reviewed. These data strongly support the clinical use of PEMFs in OA patients.

Biologic approaches to articular cartilage surgery: future trends

The treatment of unicompartmental osteoarthritis and focal chondral pathologic conditions in the knee in active aging athletes has captured the interest of patients, clinicians, basic scientists, and medical industry researchers. Most would agree that a biologic solution to treating hyaline cartilage injuries and degeneration would be optimal over prosthetic joint arthroplasty. Articular cartilage resurfacing techniques and biologic surgical methods continue to evolve and have gained more acceptance in orthopedic practice. A consensus exists for the ultimate goal of achieving a more predictable and durable result after surgical tissue repair or regeneration. Numerous promising approaches are now on the horizon and although the final word is far from in, the integration of many of the anticipated advances in molecular medicine, biomedical engineering, polymer chemistry, cell biology, and clinical orthopedics contributes to an exciting and rapidly evolving field. This article reviews the current concepts of the biologic approach to articular cartilage pathologic conditions and discusses future trends and novel technologies.

Autologous chondrocyte implantation for treatment of focal chondral defects of the knee--a clinical, arthroscopic, MRI and histologic evaluation at 2 years

To determine the efficacy of autologous chondrocyte implantation (ACI) in treating focal chondral defects of the knee, we reviewed the 2-year treatment outcome of ACI in 53 patients (72 lesions) through clinical evaluation, MRI, second-look arthroscopy and biopsies obtained. Improvement in mean subjective score from preoperative (37.6) to 12 months (56.4) and 24 (60.1) months post-ACI were observed. Knee function levels also improved [86% International Cartilage Repair Society (ICRS) III/IV to 66.6% I/II] from preoperative period to 24 months postimplantation. Objective IKDC score of A or B were observed in 88% preoperatively. This decreased to 67.9% at 3 months before improving to 92.5% at 12 months and 94.4% at 24 months post implantation. Transient deterioration in all these clinical scores was observed at 3 months before progressive improvement became evident. MRI studies demonstrated 75.3% with at least 50% defect fill, 46.3% with near normal signal, 68.1% with mild/no effusion and also 66.7% with mild/no underlying bone marrow oedema at 3 months. These values improved to 94.2%, 86.9%, 91.3% and 88.4%, respectively, at 12 months. At 24 months, further improvements to 97%, 97%, 95.6% and 92.6%, respectively, were observed. Second-look arthroscopy carried out in 22 knees (32 lesions) demonstrated all grafts to be normal/nearly normal based on the International Cartilage Repair Society (ICRS) visual repair assessment while core biopsies from 20 lesions demonstrated 13 grafts to have hyaline/hyaline-like tissue. Improvement in clinical and MRI findings obtained from second-look arthroscopy and core biopsies evaluated indicate that, at 24 months post-ACI, the resurfaced focal chondral defects of the knee remained intact and continued to function well.

Repair of porcine articular cartilage defect with autologous chondrocyte transplantation

Articular cartilage is known to have poor healing capacity after injury. Autologous chondral grafting remains the mainstay to treat well-defined, full-thickness, symptomatic cartilage defects. We demonstrated the utilization of gelatin microbeads to deliver autologous chondrocytes for in vivo cartilage generation. Chondrocytes were harvested from the left forelimbs of 12 Lee-Sung pigs. The cells were expanded in monolayer culture and then seeded onto gelatin microbeads or left in monolayer. Shortly before implantation, the cell-laden beads were mixed with collagen type I gel, while the cells in monolayer culture were collected and re-suspended in culture medium. Full-thickness cartilage defects were surgically created in the weight-bearing surface of the femoral condyles of both knees, covered by periosteal patches taken from proximal tibia, and sealed with a porcine fibrin glue. In total, 48 condyles were equally allotted to experimental, control, and null groups that were filled beneath the patch with chondrocyte-laden beads in gel, chondrocytes in plain medium solution, or nothing, respectively. The repair was examined 6 months post-surgery on the basis of macroscopic appearance, histological scores based on the International Cartilage Repair Society Scale, and the proportion of characteristic chondrocytes. Tensile stress-relaxation behavior was determined from uniaxial indentation tests. The experimental group scored higher than the control group in the categories of matrix nature, cell distribution pattern, and absence of mineralization, with similar surface smoothness. Both the experimental and control groups were superior to the null group in the above-mentioned categories. Viable cell populations were equal in all groups, but the proportion of characteristic chondrocytes was highest in the experimental group. Matrix stiffness was ranked as null > native cartilage > control > experimental group. Transplanted autologous chondrocytes survive and could yield hyaline-like cartilage. The application of beads and gel for transplantation helped to retain the transferred cells in situ and maintain a better chondrocyte phenotype.

Surgical management of cartilage defects in athletes

The synovial joints provide a unique environment in which to carry out their critical mechanical function. The complex architecture of the articular cartilage normally provides painless motion throughout a variety of activities. Fluids secreted by cells in the superficial layers of the articular cartilage as well as in the synovium provide an almost frictionless articulation. The synovium also helps to maintain the aseptic environment found within the joint. The cartilage and fluid provide critical protection to the underlying bone. If any of these structures are damaged, or lose their efficiency, the ensuing cascade of damage inflicted on the joint can lead to catastrophic failure.

Accuracy of quantitative magnetic resonance imaging in the detection of ex vivo focal cartilage defects

BACKGROUND

No established, non-invasive diagnostic procedure for quantifying focal cartilage defects is currently available.

OBJECTIVE

To test the accuracy of quantitative magnetic resonance imaging (qMRI) for reliable determination of cartilage defect size in various compartments of the human knee.

METHODS

24 tibial and patellar cartilage plates were harvested during knee arthroplasty. 74 cylindrical defects with diameters of 3, 5, and 8 mm were created with a punch. In 15 specimens (51 defects), the cartilage cylinders (inside the punch) were removed (approach 1), while in 9 specimens (23 defects) the surrounding tissue was removed mechanically and the cartilage cylinder was left in place (approach 2). All plates were imaged with a T(1) weighted water excitation gradient echo sequence at a resolution of 1.5 mm x 0.31 mm x 0.31 mm. The defect size was computed from the image data after interactive segmentation and compared with the known dimensions of the cylinders.

RESULTS

Although there was a significant overestimation of the defect size by qMRI in 3 mm defects (mean (SD) +1.3 (0.58) mm = +/-42%; p<0.001), the overestimation was only +1.0 (0.57) mm (+/-21%; p<0.05) in 5 mm defects and +0.1 (0.39) mm (+/-4%; p = 0.31) in 8 mm defects (approach 1). Values were similar for approaches 1 and 2 and for patellar and tibial cartilage plates.

CONCLUSIONS

These findings show that qMRI allows accurate quantification of focal cartilage defects. It may therefore represent a valuable tool in the diagnosis of traumatic cartilage lesions, osteochondrosis dissecans, and osteochondral fractures, and in monitoring their responsiveness to surgical or other treatments.