The knee joint has also a periarticular adipose tissue, which is known as Hoffa's fat pad (IPFP). IPFP has a dual function in the joint it reduces the concentration of Nitric Oxide, the release of glycosaminoglycans and the expression of MMP1 in the cartilage, but it also contains MSC and macrophages. Our hypothesis is that synovial fluid contains elements, not all of which are understood, which act as messengers and alter the “homeostasis” of the knee and the metabolism of all the cellular components of the joint, including the MSC of Hoffa's fat pad, thus making them another piece in the puzzle as far as OA of the knee is concerned. The IPFP of 37 patients with OA and 36 patients with ACL rupture were analyzed. Isolation, primary culture, and a functional and proteomic study of MSCs from IPFP were performed. Our results show that OA of the knee, in its more severe phases, also affects the MSC's of IPFP, which is a new actor in the OA degenerative process and which can contribute to the origin, onset and progression of the disease. A differential protein profile between OA and ACL patients were identified. Infrapatellar pad should be regarded as an adipose tissue with its own characteristics and it´s also able to produce and excrete important inflammatory mediators directly into the knee joint

Introduction. High-volume image guided injections (HVIGI) followed by structured rehabilitation have been shown to be effective in various musculoskeletal conditions including Achilles tendinopathy and shoulder impingement syndrome. The aim was to explore the effect of a HVIGI in Hoffa's fat pad impingement, a common cause of anterior knee pain. Materials and Methods. 100 consecutive subjects who received a HVIGI followed by a standardised physiotherapy rehabilitation regime for Hoffa's fat pad impingement (diagnosed using clinical history, examination and magnetic resonance imaging) at one specialist MSK centre were sent a follow-up questionnaire. The questionnaire collected demographics, symptom length and the percentage improvement in symptoms following the HVIGI. All had received HVIGI consisting of 10ml of 0.5% Marcaine and 50mg of hydrocortisone followed by a structured rehabilitation programme with a focus on lower limb alignment control, flexibility, hip and knee strengthening in line with best practice. Data was analysed using SPSS version 20 at this interim stage; data collection is continuing. Results. The response rate at this point is currently 28%. Of the twenty-six subjects (9 female; 19 male; average age 37.8 ± 13.4) who completed the questionnaire 82% had had anterior knee pain symptoms for >6 months prior to receiving a HVIGI. The average percentage improvement in anterior knee pain was 45 ± 36.5% (range 0–100%). 48% of subjects reported a >6 month improvement in symptoms. No adverse effects were reported and no subject required anytime off work. Discussion. HVIGI with a structured rehabilitation programme should be considered in the short term management of Hoffa's fat pad impingement. Future research should be prospective, to improve the response rate, and consider longer term outcomes

Multipotential processed lipoaspirate (PLA) cells extracted from five human infrapatellar fat pads and embedded into fibrin glue nodules, were induced into the chondrogenic phenotype using chondrogenic media. The remaining cells were placed in osteogenic media and were transfected with an adenovirus carrying the cDNA for bone morphogenetic protein-2 (BMP-2). We evaluated the tissue-engineered cartilage and bone using in vitro techniques and by placing cells into the hind legs of five severe combined immunodeficient mice. After six weeks, radiological and histological analysis indicated that the PLA cells induced into the chondrogenic phenotype had the histological appearance of hyaline cartilage. Cells transfected with the BMP-2 gene media produced abundant bone, which was beginning to establish a marrow cavity. Tissue-engineered cartilage and bone from infrapatellar fat pads may prove to be useful for the treatment of osteochondral defects

The incidence of osteoarthritis (OA) is increasing in our younger population. OA development early in life is often related to cartilage damage, caused by (sport) injury or trauma. Detection of early knee OA is therefore crucial to target early treatment. However, early markers for OA prognosis or diagnosis are lacking. Hoffa's fat pad (HFP) is an emerging source for knee biomarkers, as it is easily accessible and shows important interaction with the homeostasis of the knee. In this study, we used Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) as a first approach. MALDI-MSI allows the study of tissue-specific molecular distributions. Therefore, we used MALDI-MSI to analyze the lipid profiles in the HFP of three patients with OA and three patients undergoing cartilage regenerative treatment. We demonstrate that the lipid profile of patients with OA is different from patients with cartilage defects. HFP of each patient were snap frozen directly after surgical resection and cryosectioned at 15 μm. Each slide was sublimed with Norharmane matrix and analyzed by MALDI-MSI in positive and negative ion modes at a lateral resolution of 50 μm on a RapifleX Tissue Typer. The difference between patient groups were analyzed using principle component analysis and linear discriminant analysis. Lipid identifications were obtained on an Orbitrap Elite™ Hybrid Ion Trap-Orbitrap Mass Spectrometer in data dependent acquisition mode and analyzed using Lipostar software. Linear discriminant analysis showed a specific lipid profile for each group (variance 33.94%). Score projections revealed a differential lipid spatial distribution of OA patients compared to cartilage defect patients. Among the lipids that differed significantly, for instance, the m/z 760.59 [M+H]. +. was associated to osteoarthritis and identified as glycerophospholipid (PC 34:1), a main component of biological membranes. Additionally, the samples were found to be intra-tissue heterogeneous, with molecular profiles found in adipose-, connective- and synovial tissue. These results suggest that lipid profiles in HFP could be useful for early OA detection. However, intra-tissue heterogeneity in HFP should be recognized when using HFP as a biomarker source

Early detection of knee osteoarthritis (OA) is critical for possible preventive treatment, such as weight loss, physical activity and sports advice and restoring biomechanics, to postpone total knee arthroplasty (TKA). Specific biomarkers for prognosis and early diagnosis of OA are lacking. Therefore, in this study, we analyzed the lipid profiles of different tissue types within Hoffa's fat pad (HFP) of OA and cartilage defect (CD) patients, using matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI). The HFP has already been shown to play an important role in the inflammatory process in OA by prostaglandin release. Additionally, MALDI-MSI allows us to investigate on tissue lipid distribution at molecular level, which makes it a promising tool for the detection of disease specific biomarkers for OA development. Samples of HFP were obtained of patients undergoing surgical treatment for OA (n=3) (TKA) or CD (n=3) (cartilage repair). In all cases, tissue was obtained without patient harm. HFP samples were washed in phosphate buffered saline (PBS) and snap-frozen directly after surgical dissection to remove redundant blood contamination and to prevent as much tissue degradation as possible. Tissue sections were cut at 15 µm thickness in a cryostat (Leica Microsystems, Wetzlar) and deposited on indium tin oxide glass slides. Norharmane (Sigma-Aldrich) matrix was sublimed onto the tissue using the HTX Sublimator (HTX Technologies, Chapel Hill). µMALDI-MSI was performed using Synapt G2Si (Waters) at 50 µm resolution in positive ion mode. MS/MS fragmentation was performed for lipid identification. Data were processed with in-house Tricks for MATLAB and analyzed using principle component analysis (PCA) and verlan. OA and CD HFP specific lipid profiles were revealed by MALDI-MSI followed by PCA and DA. With these analyses we were able to distinguish different tissue types within HFP of different patient groups. Further discriminant analysis showed HFP intra-tissue heterogeneity with characteristic lipid profiles specific for connective and adipose tissues, but also for synovial tissue and blood vessels, revealing the high molecular complexity of this tissue. As expected, lipid signals were lower at the site of the connective tissue, compared to the adipose tissue. In particular, tri-acyl glycerol, di-acyl glycerol, sphingomyelin and phosphocholine species were differently abundant in the adipose tissue of HFP of OA compared to CD. To our knowledge, this is the first study comparing lipid profiles in HFP of OA patients with CD patients using MALDI-MSI. Our results show different lipid profiles between OA and CD patients, as well as intra-tissue heterogeneity within HFP, rendering MALDI-MSI as a useful technology for OA biomarker discovery. Future research will focus on expanding the number of subjects and the improvement of lipid detection signals

Introduction. Kager's fat pad (KFP) is located in Kager's triangle between the Achilles tendon (AT), the superior cortex of the calcaneus and Flexor Hallucis Longus (FHL) muscle & tendon. Although the biomechanical functions of KFP are not yet fully understood, a number of studies suggested that KFP performs important biomechanical roles including assisting in the dynamic lubrication of the AT subtendinous area, protection of AT vascular supply, and load and stress distribution within the retrocalcaneal bursa space. Similar to the knee meniscus, KFP has become under increasing investigations since strong indications were found that it serves more than just a space filler. Both KFP and the knee meniscus are anchored to their surrounding tissues via fibrous attachments, they can be found in encapsulated (or ‘air tight’) regions, lined by synovial membranes, and they both slide within their motion ranges. The protruding wedge (PW) of KFP was observed to slide in and out of the retrocalcaneal bursal space during ankle plantarflexion and dorsiflexion, respectively. In-vitro studies of KFP suggest that it reduces the load by 39%, which is similar to that of the knee meniscus (30%-70% of the load applied on the knee joint). This study investigated the in-vivo load bearing functionality of KFP. Materials and Methods. The ankles of 5 volunteers (3 males, 2 females, Age 20-28, BMI 21-26) were scanned using a 0.2T MRI scanner at ankle plantarflexion and neutral positions. The ankles of 2 of those volunteers were later scanned using a 3T MRI scanner for higher accuracy. The areas and volumes of KFP were measured using Reconstruct¯ 3D modelling software. The hind foot of the volunteers were scanned using dynamic ultrasound to measure in-vivo real time shape changes of PW. Results. The cross sectional area of KFP in the AT midline saggital plane increased on average by 10% when ankles were changed from neutral to plantarflexion positions. The volume of KFP showed less variation than cross sectional areas (3.9% variation in volume). Previous studies showed the cross sectional area of the knee meniscus changes by 9.8% during loading, or flexing the knee by 90°, and its volume was reduced by 3.5%-5.9% (medial and lateral menisci respectively). Ultrasound imaging showed that PW's thickness decreased during dorsiflexion compared to plantarflexion by an average of 1mm and a hysteresis was found between the location of PW's tip and the insertion angle of AT, suggesting the fibrous tip of PW bears load during dorsiflexion. Discussions and conclusions. The similarities in results between the knee meniscus (literature review) and KFP supports hypotheses that KFP assists in reducing the load applied at the AT enthesis organ. Furthermore, histological studies showed a fibrosis is evident at the tip of PW, which is thought to be developed as a result of resisting external loading. This also supports speculations that KFP removal is likely to reduce lubrication, pressure distribution, load bearing, and consequently, increasing the tear and wear level within AT enthesis

Introduction. Mesenchymal stem cells are a potential source of cells for the repair of articular cartilage defects. We have previously demonstrated that the infrapatellar synovial fat pad is a rich source of mesenchymal stem cells and these cells are able to undergo chondrogenic differentiation. Although synovial fat pad derived mesenchymal stem cells may represent a heterogenous population, clonal populations derived from the synovial fat pad have not previously been studied. Materials and Methods. Mesenchymal stem cells were isolated from the infrapatellar synovial fat pad of a patient undergoing total knee arthroplasty and expanded in culture. Six clonal populations were also isolated before initial plating using limiting dilution and expanded. The cells from the mixed parent population and the derived clonal populations were characterised for stem cell surface epitopes, and then cultured as cell aggregates in chondrogenic medium for 14 days. Gene expression analyses; glycosoaminoglycan and DNA assays; and immunohistochemical staining were determined to assess chondrogenic responses. Results. Cells from the mixed parent population and the derived clonal populations stained strongly for markers of adult mesenchymal stem cells including CD44, CD90 and CD105, and they were negative for the haematopoietic marker CD34 and for the neural and myogenic marker CD56. Interestingly, a variable number of cells were also positive for the pericyte marker 3G5 both in the mixed parent and clonal populations. The clonal populations exhibited a variable chondrogenic response; one clonal cell population exhibited a significantly greater chondrogenic response when compared with the mixed parent population. Discussion. Pericytes are a candidate stem cell in many tissue and our results show that all six clonal populations derived from the heterogenous synovial fat pad population express the pericyte marker 3G5. The variable chondrogenic responses suggest inherent differences between these populations. The chondrogenic potential of the synovial fat pad could be optimised by the identification of clonal populations with a propensity to differentiate down particular differentiation pathways, and this has implications on the future tissue engineering applications of these cells for cartilage repair

Articular cartilage is often damaged, and its treatment is usually performed by surgical operation. Today, tissue engineering offers an alternative treatment option for injuries or diseases with increasing importance. Infrapatellar fat pad (IPFP) is a densely vascularized and innervated extra synovial tissue that fills the anterior knee compartment. Adipose-derived stem cells from infrapatellar fat pad (IPFP-ASCs) have multipotency means that they can differentiate into connective tissue cells and have age-independent differentiation capacity as compared to other stem cells. In this study, the osteochondral tissue construct was designed with different inner pattern due to original osteochondral tissue structure and fabrication of it was carried out by 3D printing. For this purpose, alginate (3% w/v) and carboxymethylcellulose (CMC) (9%w /v) were used as bioink. Also, IPFP-ASCs were isolated with enzymatic degradation. Osteogenic and chondrogenic differentiation of IPFP-ASCs were investigated with Alizarin Red and Alcian Blue staining, respectively. IPFP-ASCs-laden osteochondral graft differentiation will be induced by controlled release of growth factor BMP-2 and TGF-β. Before this step, nanocapsules formation with double emission technique with model protein BSA was carried out with different concentration of PCL (5%,10% and 20%). The morphology and structure of the nanocapsules were determined with scanning electron microscopy (SEM). Also, we successfully designed and printed alginate and CMC based scaffold with 20 layers. Chondrogenic and osteogenic differentiation of IPFP-ASCs with suitable culture conditions was obtained. The isolation of IPFP-ASCs, formation of the nanocapsules, and 3D printing of osteochondral graft were carried out successfully

Introduction. Mesenchymal stem cells (MSC) are an attractive cell population for regeneration of mesenchymal tissue such as bone and cartilage. Various studies have demonstrated the repair capacity of MSCs and even their usefulness in treating critical size defects. Much of the work conducted on adult stem cells has focused on MSCs found within the bone marrow stroma. Adipose tissue, like bone marrow, is derived from the embryonic mesenchyme and contains a stroma that is easily isolated. The aim of the present study is to evaluate the differentiation capability of adipose-tissue derived stem cells (ASC) extracted from the infrapatellar fat pad. Materials and Methods. Human infrapatellar fat pad tissue was obtained from patients undergoing total joint replacement for osteoarthritis with full ethical consent. A multipotent progenitor cell population was derived after collagenase digestion from the adipose tissue. The ASCs were induced to differentiate towards adipogenic, chondrogenic, and osteogenic lineages for 21 days both in normoxic and hypoxic cell culture conditions. The differentiation and multilineage potential was assessed according to cell morphology and in vitro detection of tissue-specific differentiation molecules. Results. After 3 weeks in culture the staining for oil-red-o, alcian bue, and alizarin-red confirmed the differentiation capability of ASC's to adipogenic, chondrogenic, and osteogenic lineages, respectively. The hypoxic cell culture condition was found to support the ASCs' chondrogenic differentiation capability and subsequently enhanced the proteoglycan release from the cells. Fluorescence-activated cell sorting (FACS) confirmed the presence of stromal precursor cell marker STRO-1 in the ASC population. Discussion. Subcutaneous adipose tissue is particularly attractive reservoir for progenitor cells because it is easily accessible, rather abundant, and self-replenishing. The results of this study demonstrate that ASCs can be derived from infrapatellar fat pad and that they have potential for musculoskeletal tissue repair and regeneration. Further studies are underway to evaluate how to adopt a biomaterial to deliver these cells into the defect area to facilitate the healing response

Abstract. Objectives. Osteoarthritis is a common articular cartilage disorder and causes a significant global disease burden. Articular cartilage has a limited capacity of repair and there is increasing interest in the use of cell-based therapies to facilitate repair including the use of Mesenchymal Stromal Cells (MSCs). There is some evidence in the literature that suggests that advancing age and gender is associated with declining MSC function, including reduced proliferation and differentiation potential, and greater cellular apoptosis. In our study, we first performed a systematic review of the literature to determine the effects of chronological age and gender on the in vitro properties of MSCs, and then performed a laboratory study to investigate these properties. Methods and Results. We initially conducted a PRISMA systematic review of the literature to review the evidence base for the effects of chronological age and gender on the in vitro properties of MSCs including cell numbers, expansion, cell surface characterization and differentiation potential. This was followed by laboratory-based experiments to assess these properties. Compare the extent of the effect of age on MSC cell marker expression, proliferation and pathways. Tissue from patients undergoing total knee replacement surgery was used to isolate MSCs from the synovium, fat pad and bone fragments using a method developed in our laboratory. The growth kinetics was determined by calculating the population doublings per day. Following expansion in culture, MSCs at P2 were characterised for a panel of cell surface markers using flow cytometry. The cells were positive for CD73, CD90 and CD105, and negative for antibody cocktail (eg included CD34, CD45). The differentiation potential of the MSCs was assessed through tri-lineage differentiation assays. At P2 after extracting RNA, we investigate the gene analysis using Bulk seq. Clear differences between the younger and older patients and gender were indicated. Conclusions. Chronological age and gender-related changes in MSC function have important implications on the use of these cells in clinical applications for an ageing population. The results from this study will be used to plan further work looking at the effects of chronological age and gender on cellular senescence and identify pathways that could be targeted to potentially reverse any age and gender-related changes. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Osteoarthritis is a common articular cartilage disorder and causes a significant global disease burden. Articular cartilage has a limited capacity of repair and there is increasing interest in the use of cell-based therapies to facilitate repair including the use of Mesenchymal Stromal Cells (MSCs). There is some evidence in the literature that suggests that advancing age is associated with declining MSC function, including reduced proliferation and differentiation potential, and greater cellular apoptosis. In our study, we first performed a systematic review of the literature to determine the effects of chronological age on the in vitro properties of MSCs, and then performed a laboratory study to investigate these properties. We initially conducted a PRISMA systematic review of the literature to review the evidence base for the effects of chronological age on the in vitro properties of MSCs including cell numbers, expansion, cell surface characterization and differentiation potential. This was followed by laboratory based experiments to assess these properties. Tissue from patients undergoing total knee replacement surgery was used to isolate MSCs from the infrapatellar fat pad using a method developed in our laboratory. The growth kinetics was determined by calculating the population doublings per day. Following expansion in culture, MSCs at P2 were characterised for a panel of cell surface markers using flow cytometry. The cells were positive for CD73, CD90 and CD105, and negative for CD34 and CD45. The differentiation potential of the MSCs was assessed through tri-lineage differentiation assays. Chronological age-related changes in MSC function have important implications on the use of these cells in clinical applications for an ageing population. The results from this study will be used to plan further work looking at the effects of chronological age on cellular senescence and identify pathways that could be targeted to potentially reverse any age-related changes

Abstract. Focal articular cartilage defects do not heal and, left untreated, progress to more widespread degenerative changes. A promising new approach for the repair of articular cartilage defects is the application of cell-based regenerative therapies using mesenchymal stromal cells (MSCs). MSCs are however present in a number of tissues and studies suggest that they vary in their proliferation, cell surface characterisation and differentiation. As the phenotypic properties of MSCs vary depending on tissue source, a systematic comparison of the transcriptomic signature would allow a better understanding of these differences between tissues, and allow the identification of markers specific to a MSC source that is best suited for clinical application. Tissue was used from patients undergoing total knee replacement surgery for osteoarthritis following ethical approval and informed consent. MSCs were isolated from bone, cartilage, synovium and infrapatellar fat pad. MSC number and expansion were quantified. Following expansion in culture, MSCs were characterised using flow cytometry with several cell surface markers; the cells from all sources were positive for CD44, CD90 and CD105. Their differentiation potential was assessed through tri-lineage differentiation assays. In addition, bulk mRNA-sequencing was used to determine the transcriptomic signatures. Differentially expressed (DE) genes were predicted. An enrichment analysis focused on the DE genes, against GO and pathway databases (KEGG and Reactome) was performed; protein-protein interaction networks were also inferred (Metascape, Reactome, Cytoscape). Optimal sourcing of MSCs will amplify their cartilage regeneration potential. This is imperative for assessing future therapeutic transplantation to maximise the chance of successful cartilage repair. A better understanding of differences in MSCs from various sources has implications beyond cartilage repair

Gradients of three-dimensional (3D) hierarchical tissues are common in nature and present specific architectures, as this is the case of the anisotropic subchondral bone interfaced with articular cartilage. While diverse fabrication techniques based on 3D printing, microfabrication, and microfluidics have been used to recreate tailored biomimetic tissues and their respective microenvironment, an alternative solution is still needed for improved biomimetic gradient tissues under dynamic conditions with control over pre-vasculature formation. Here, we engineered a gradient osteochondral human-based tissue with precise control over both cell/tissue phenotype and pre-vasculature formation, which opens-up possibilities for the study of complex tissues interfaces, with broader applications in drug testing and regenerative medicine. The fabrication of 3D gradients of microparticles was performed combining methacrylated gelatin (GelMA) and gellan gum (GG) (3:1, w:w ratio) with hydroxyapatite microparticles (HAp, 30% w/w). The mixing of the interface was controlled by the temperature of two polymeric layers, being the second added at 10 ºC higher than the first one. This subsequent addition of polymeric solutions at different temperatures promoted convection, which drove the microparticles through the interface from the first to the second layered gel forming the HAp gradient. After ionic and photo-crosslinking, the freezing step was programmed using an external cover of styrofoam forcing the ice crystals to grow linearly, generating an anisotropic architecture in a gradient scaffold. A dual-chamber microreactor device was designed (figure 1A) to culture fat pad adipose-derived stem cells and microvascular endothelial cells under two biochemical microenvironments. Using control over temperature and crosslinking, hydrogel-like structures were built in 3D anisotropic HAp gradients. Then, an in vitro osteochondral tissue model was obtained using a dual-chamber platform. Results showed a significant difference of SOX9 (p < 0.05), Osteocalcin and RUNX2 (p < 0.05) from the top to the bottom regions of the 3D gradient structures under dynamic conditions. Finally, a pre-vasculature was controlled over 7 days, stimulating the endothelization of the subchondral bone-like region 35% more (p < 0.05) when compared to the cartilage-like region. In this work, microparticle and biochemical gradients were fabricated into anisotropic architectures. The obtained outcomes enable the precise control of 3D gradients in programmable architectures, such as anisotropic structures, with broad applications in interfaced tissue engineering, regenerative medicine and drug testing

Background. The pattern of appearance of secondary ossification centers in the elbow has been based on historical studies and is popularly referred to with the mnemonic CRITOL. However the six secondary ossification centers can be variable in their presentation and pose a challenge in assessment of children with elbow injuries. Furthermore limited studies available in the current literature have reported an aberration to the sequence of appearance especially with the ossification centers of trochlea and olecranon. Aims. The aim of the study was to evaluate the relative sequence of appearance of secondary ossification centers for the trochlea and olecranon. Methods. Children between 8 and 10 years of age who had radiographs of elbow following trivial trauma between July 2013 and Feb 2015 were identified using the hospital PACS database. Cases with radiographic markers of significant trauma ie. fat pad sign, displaced fracture were excluded. Anteroposterior and lateral views of elbow were reviewed for the presence of the six ossification centers. Results. A total of 114 radiographs were reviewed of which 51 were boys and 63 were girls with a mean age of 9.03 years (±0.59). 60 radiographs were of right elbow and 54 were of the left elbow. The capitulum, radial head and medial epicondyle ossification centers were present in all patients. Both trochlea and olecranon ossification centers were noted in 51/114 (44.7%) children. 12/114 (10.5%) of the children were noted to have trochlea ossification center with no olecranon ossification center. Of these 12 children 7 were boys and 5 were girls. On the other hand 19/114 (16.7%) of the children had an olecranon ossification center but without a trochlea ossification center. Amongst these 7 were boys and 12 were girls. Discussion and Conclusions. The results of this limited cross sectional study demonstrate that the CRITOL sequence may not followed in 16.7% of cases and more so in girls. Historical studies were based on conventional radiographs. However the current digital radiographs with image enhancement tools help in accurate identification of relatively small ossification centers which may not be apparent on conventional radiographs. The current study has helped to quantify the violators to CRITOL sequence. Level of Evidence. Level III (Cross-sectional study among non-consecutive patients)

Summary. Nasal Chondrocytes are safe and feasible for tissue engineering approaches in articular cartilage repair. Introduction. As compared to articular chondrocytes (AC), nasal septum chondrocytes (NC) proliferate faster and have a higher and more reproducible capacity to generate hyaline-like cartilaginous tissues. Moreover, the use of NC would allow reducing the morbidity associated with the harvesting of cartilage biopsy from the patient. The objective of the present study was to demonstrate safety and feasibility in the use of tissue engineered cartilage graft based on autologous nasal chondrocytes for the repair of articular defect in goats. Methods. Isolated autologous NC and AC from 6 goats were expanded and GFP-labelled before seeding 4×10. 4. cells/cm. 2. on a type I/III collagen membrane (Chondro-Gide®, Geistlich). After 2 weeks of chondrogenic differentiation 2 NC- and 2 AC-based grafts were implanted into chondral defects (6mm diameter) of the same posterior stifle joint. Repair tissue was harvested after 3 or 6 months and the decalcified samples evaluated according to O'Driscoll. Furthermore, samples from the surrounding fat pad, ligament, synovium, tendon and patellar cartilage were harvested and isolated cells tested for GFP-positivity after expansion using FACS. Results. No surgical complication or signs of inflammation occurred in any of the animals. GFP-positive cells were detectable in the repair tissue, indicating the contribution of the implanted cells to the newly formed cartilage. The O'Driscoll score of the repair tissue increased from 8.6 and 7.6 after 3 months to 14.1 and 12.4 after 6 months for nasal and articular grafts, respectively. Surrounding tissues showed no or very low (fat pad 0–0.36%) migration of the grafted cells. Conclusion. Our results demonstrate the use of NC as safe and feasible for tissue engineering approaches in articular cartilage repair. The repair tissue-quality generated by NC-grafts was demonstrated to be at least comparable to that of AC-grafts, thus opening the way for clinical test of a novel therapeutic strategy

Summary. The donor-matched comparison between mesenchymal stem cells from knee infrapatellar and subcutaneous adipose tissue revealed their preferential commitment towards the chondrogenic and osteogenic lineage, respectively. These peculiarities could be relevant for the development of successful bone and cartilage cell-based applications. Introduction. Mesenchymal stem cells (MSCs) have been proposed in bone and cartilage tissue engineering applications as an alternative to terminally differentiated cells. In the present study we characterised and performed a donor-matched comparison between MSCs resident within the infrapatellar fat pad (IFP-MSCs) and the knee subcutaneous adipose tissue (ASCs) of osteoarthritic patients. These two fat depots, indeed, can be considered appealing candidates for orthopaedic cell-based therapies since they are highly accessible during knee surgery. Materials and Methods. IFP-MSCs and ASCs were obtained from 25 osteoarthritic patients undergoing total knee replacement. Undifferentiated cells were compared for their clonogenic ability and surface markers expression. Adipogenic, osteogenic and chondrogenic differentiative potentials were evaluated after IFP-MSCs and ASCs induction towards the various lineages by means of histological, biochemical and gene expression analysis of characteristic markers. Results. We found that undifferentiated IFP-MSCs and ASCs displayed a high clonogenic ability and the typical immunophenotype of MSCs (CD13. +. /CD29. +. /CD44. +. /CD73. +. /CD90. +. /CD105. +. /CD166. +. /CD31. −. /CD45. −. ), without any difference in terms of surface markers expression between these two cell populations. When both cell types were cultured in adequate adipo-, osteo- and chondro- differentiative media, IFP-MSCs and ASCs showed similar adipogenic potential, though undifferentiated ASCs had superior LEP expression compared to undifferentiated IFP-MSCs (p<0.01). ASCs showed a higher response to osteogenic induction in comparison with IFP-MSCs as demonstrated by significantly higher levels of calcified matrix deposition (p<0.05) and alkaline phosphatase activity (p<0.05). After 14 days of chondrogenic induction of cells cultured in pellets, we observed greater amounts of glycosaminoglycans (p<0.01) in IFP-MSCs pellets compared to ASCs pellets. Chondrogenic differentiation of IFP-MSCs showed also a superior gene expression of ACAN (p<0.001), SOX9, COMP (p<0.001) and COL2A1 (p<0.05) compared to ASCs. Furthermore, IFP-MSCs showed significantly lower levels of COL10A1 (p<0.05) and COL1A1 (p<0.01) and lower alkaline phosphatase release (p<0.05) compared to ASCs, supporting the hypothesis of a superior chondrogenic commitment of IFP-MSCs. Discussion/Conclusion. The observed dissimilarities between IFP-MSCs and ASCs suggest that despite similar features at the undifferentiated state, MSCs deriving from different anatomical sites within the same joint can display a specific commitment. The peculiar commitment of IFP-MSCs and ASCs towards the chondrogenic and osteogenic lineage suggests that they may be preferentially used for cartilage and bone applications, respectively

We dissected 20 cadaver hips in order to investigate the anatomy and excursion of the trochanteric muscles in relation to the posterior approach for total hip replacement. String models of each muscle were created and their excursion measured while the femur was moved between its anatomical position and the dislocated position. The position of the hip was determined by computer navigation.

In contrast to previous studies which showed a separate insertion of piriformis and obturator internus, our findings indicated that piriformis inserted onto the superior and anterior margins of the greater trochanter through a conjoint tendon with obturator internus, and had connections to gluteus medius posteriorly. Division of these connections allowed lateral mobilisation of gluteus medius with minimal retraction. Analysis of the excursion of these muscles revealed that positioning the thigh for preparation of the femur through this approach elongated piriformis to a maximum of 182%, obturator internus to 185% and obturator externus to 220% of their resting lengths, which are above the thresholds for rupture of these muscles.

Our findings suggested that gluteus medius may be protected from overstretching by release of its connection with the conjoint tendon. In addition, failure to detach piriformis or the obturators during a posterior approach for total hip replacement could potentially produce damage to these muscles because of over-stretching, obturator externus being the most vulnerable.

There has been only one limited report dating from 1941 using dissection which has described the tibiofemoral joint between 120° and 160° of flexion despite the relevance of this arc to total knee replacement. We now provide a full description having examined one living and eight cadaver knees using MRI, dissection and previously published cryosections in one knee.

In the range of flexion from 120° to 160° the flexion facet centre of the medial femoral condyle moves back 5 mm and rises up on to the posterior horn of the medial meniscus. At 160° the posterior horn is compressed in a synovial recess between the femoral cortex and the tibia. This limits flexion. The lateral femoral condyle also rolls back with the posterior horn of the lateral meniscus moving with the condyle. Both move down over the posterior tibia at 160° of flexion.

Neither the events between 120° and 160° nor the anatomy at 160° could result from a continuation of the kinematics up to 120°. Therefore hyperflexion is a separate arc. The anatomical and functional features of this arc suggest that it would be difficult to design an implant for total knee replacement giving physiological movement from 0° to 160°.

Objectives

Acetabular component orientation in total hip arthroplasty (THA) influences results. Intra-operatively, the natural arthritic acetabulum is often used as a reference to position the acetabular component. Detailed information regarding its orientation is therefore essential. The aim of this study was to identify the acetabular inclination and anteversion in arthritic hips.