Search

Background: Bipolar or “kissing” cartilage lesions formed on 2 opposite articular surfaces of the knee joint are commonly listed as exclusion criteria for advanced cartilage therapies. Purpose: To test, in a pilot large-animal study, whether autologous nasal chondrocyte (NC)–based tissue engineering, recently introduced for the treatment of focal cartilage injuries, could provide a solution for challenging kissing lesions. Study Design: Controlled laboratory study. Methods: Osteochondral kissing lesions were freshly introduced into the knee joints of 26 sheep and covered with NC-based grafts with a low or high hyaline-like extracellular matrix; a control group was treated with a cell-free scaffold collagen membrane (SCA). The cartilage repair site was assessed at 6 weeks and 6 months after implantation by histology, immunohistochemistry, and magnetic resonance imaging evaluation. Results: NC-based grafts, independently of their composition, induced partial hyaline cartilage repair with stable integrity in surrounding healthy tissue at 6 months after treatment. The SCA repaired cartilage to a similar degree to that of NC-based grafts. Conclusion: Kissing lesion repair, as evidenced in this sheep study, demonstrated the feasibility of the treatment of complex cartilage injuries with advanced biological methods. However, the potential advantages of an NC-based approach over a cell-free approach warrant further investigations in a more relevant preclinical model. Clinical Relevance: NC-based grafts currently undergoing phase II clinical trials have a high potential to replace existing cartilage therapies that show significant limitations in the quality and reproducibility of the repair method. We have brought this innovative concept to the next level by addressing a new clinical indication.

Izolirana rekonstrukcija prednjeg križnog ligamenta (ACL) predstavlja zlatni standard u kirurškom liječenju rupture prednjeg križnog ligamenta. No, neuspjeh cijeljenja presatka i ostatna rotacijska nestabilnost koljena i dalje su česte postoperativne komplikacije. Anterolateralni ligament (ALL) i njegova uloga u kontroli rotacijske stabilnosti dobila je značajan interes 2013. nakon objave njegova „ponovnog otkrića”. Ta ligamentarna struktura, opisana još davne 1879., potječe od proksimalnog i stražnjeg dijela lateralnog epikondila bedrene kosti i hvata se na goljeničnoj kosti, na sredini između Gerdyjeva tuberkla i glavice fibule. Biomehanička ispitivanja pokazala su da anterolateralni ligament djeluje kao pasivni stabilizator koljena tijekom unutarnje rotacije koljena, i kod rupture ACL-a i lateralnih struktura koljena odgovoran je za nastanak pivot-shift fenomena. Pokazalo se da izolirana rekonstrukcija ACL-a u pacijenata s ozljedom ACL-a i ALL-a ne može vratiti normalnu kinematiku koljena, za razliku od njihove kombinirane rekonstrukcije. Uz to, dosadašnja literatura nudi brojne dokaze u smislu poboljšanja stabilnosti koljena nakon kombiniranog postupka rekonstrukcije ACL-a i ALL-a. Štoviše, nedavne kliničke studije pokazale su da ALL ima zaštitni učinak na očuvanje presatka ACL-a, kao i na brži ponovni povratak u sport i opće zadovoljstvo pacijenata s operativnim zahvatom. Ovaj pregledni rad ima za cilj dati pregled dosadašnjeg znanja anatomije, funkcije i učinka rekonstrukcije ACL-a i ALL-a u pacijenata s puknućem ACL-a., Isolated anterior cruciate ligament (ACL) reconstruction is the gold standard in surgical treatment of anterior cruciate ligament rupture. However, graft failure rates and residual rotational instability of the knee are still common post-operative complications. The anterolateral ligament (ALL) and its role in controlling rotational stability gained considerable interest in 2013 following the announcement of its ‟rediscovery”. This ligamentous structure, described back in 1879, originates just proximal and posterior of the lateral epicondyle of the femur and it ends on the tibia, midway between Gerdy's tubercle and the head of the fibula. Biomechanical studies have shown that the anterolateral ligament acts as a passive knee stabilizer during internal knee rotation and in the rupture of the ACL and lateral knee structures is responsible for the presence of a pivot-shift knee phenomenon. It has been shown that isolated ACL reconstruction in patients with ACL and ALL injury cannot restore normal knee kinematics unlike their combined reconstruction. In addition, recent literature shows evidence in terms of improving knee stability after a combined ACL and ALL reconstruction procedure. Moreover, recent clinical studies have shown that ALL has a protective effect on the preservation of ACL graft as well as on the faster return to sport and overall patient satisfaction. This review aims to give an overview of our current knowledge of the anatomy, function, and effect of combined ACL and ALL reconstruction in patients with ACL rupture.

Increased knowledge of the long-term destructive consequences of meniscectomy has created a shift towards operative repair of isolated meniscus lesions. However, in the literature the results of isolated meniscal repair in athletes currently remain underreported. Our objective was to investigate the clinical and functional outcomes as well as survival and return to sport in patients who underwent meniscal repair after isolated meniscal tear, with a focus on athletes (both professional and recreational) in the study population. This retrospective study included 52 athletes who underwent knee surgery for isolated meniscal tear between 2014 and 2020. Patients with concomitant ligamentous and/or chondral injury were not included in this study. The mean age of the patients was 25.5 years (ranging from 12 to 57 years). The mean follow-up period of all patients was 33.3 months (ranging 10 to 80 months). The mean purpose of the study was to report the return to sport. The International Knee Documentation Committee rating (IKDC), Lysholm score, the Knee Osteoarthritis Outcome Score (KOOS) and Tegner activity level were determined at the follow-up. Failure was defined as re-operation with meniscectomy or revision meniscal repair. In total, 44 out of 52 patients (85%) returned to their previous sports activities. At follow-up, the mean Lysholm score was 90, representing a good to excellent result. Assessment of KOOS (mean value 88.8) and IKDC (mean value 89) scores also showed good to excellent results. A mean level of Tegner scale was 6.2, indicating a relatively high level of sports participation. Failure was encountered in 8 out of 52 knees (15%). Therefore, isolated meniscal repair resulted in good to excellent knee function and most athletes can return to their previous level of sports participation.

Cushing's syndrome is an uncommon clinical condition most frequently presenting with central obesity, facial rounding, proximal muscle weakness, and skin thinning. The objective of this case report is to highlight an unusual presentation of Cushing's syndrome. A 35-year-old woman presented to the orthopedic clinic with a 1-year history of foot pain without any history of trauma. Radiography of the foot showed multiple metatarsal fractures. Evaluation for secondary causes of reduced bone strength revealed that the patient had Cushing's disease, although other typical signs and symptoms were not remarkable. It can be concluded that Cushing's syndrome should always be included in the differential diagnosis of foot fracture without any evidence of trauma.

During the past few decades, surgical techniques for anterior cruciate ligament (ACL) reconstruction have been developing significantly. To date, studies have shown that after ACL reconstruction, rotational stability has a greater impact on the patient's satisfaction, functional scores, and return to sports than translational stability. Although challenged by many authors in the literature, biomechanical studies on the anterolateral ligament (ALL) of the knee and clinical studies regarding ALL reconstruction have been revealing promising results. Thus, the potentially significant role of the ALL in biomechanical load sharing and improving rotational control of the knee has led to the development of various reconstruction techniques whose goal is to achieve simplicity and yield the best results possible. Guided by this idea, we have developed a modified ACL-ALL reconstruction surgical technique. In this article, our simple, bone-saving, anatomic technique to reconstruct both the ACL and ALL using hamstring tendon autograft is described., Technique Video Video 1 On the Graft Prep Station Base (Arthrex), the harvested semitendinosus tendon is marked every 8 cm and tripled over a TightRope on the tibial side, ensuring a graft length of 8 cm. The most distal suture (No. 2-0 Vicryl) is placed to stabilize the tripled semitendinosus graft and secure the length. The gracilis tendon is put inside the tripled semitendinosus graft, and the whole graft is then tagged with multiple sutures (No. 2-0 Vicryl) to secure the gracilis position and to tubularize the graft. A No. 2 FiberWire is placed on the femoral end of the anterior cruciate ligament (ACL) graft by going around and through the tendons to ensure secure further graft manipulation. The ACL graft is marked 3 cm from both the femoral and tibial sides, representing parts of the graft that will be placed inside the bone tunnels. An ACL graft consisting of 3 parts semitendinosus and 1 part gracilis is obtained, with a diameter of 8 to 10 mm and length of 8 cm. With the patient in the supine position and the left knee in 90° of flexion and in a leg holder, 3 bony landmarks are marked on the patient's left knee: the lateral epicondyle, the Gerdy tubercle, and the head of the fibula. Two convergent bony tunnels are drilled in the proximal part of the left tibia with a 4.5-mm drill bit, separated by roughly 2 cm and approximately 1 cm distal to the joint line. A suture (No. 2 Vicryl) is then passed through the tunnels in a retroverted fashion to create a loop for further anterolateral ligament (ALL) graft (gracilis tendon) passage. The tibial guidewire (outside-in jig) is placed 55° from the external medial tibial cortex into the ACL remnant. Subsequent reaming with the retro-drill is performed for 35 mm according to the previously measured ACL graft size, with preservation of the ACL remnant synovial cover and tibial attachment. A 2- to 3-cm incision is made along the lateral aspect of the thigh, extending proximal from the lateral epicondyle. A Kirschner wire is used to mark the femoral epicondyle. A guide is introduced through the anteromedial portal. The tip of the guide is anchored at the ACL femoral insertion. The guide sleeve is pushed onto the lateral cortex through the femoral stab incision underneath the iliotibial band (ITB) and into the incision made longitudinally through the ITB fibers to position a drill for femoral tunnel drilling roughly 1 cm proximal and 8 mm posterior to the Kirschner wire. Then, subsequent femoral bone drilling is performed to the appropriate measured ACL size. By use of a suture, the TightRope and graft are passed through the longitudinal incision of the ITB and the ACL femoral tunnel to the distal 3-cm mark inside the tibial tunnel. To ensure the exact length of the graft in the tibial bone tunnel (distal demarcation), tension on the graft from the femoral side is used and the correct graft and demarcation position is monitored arthroscopically. Subsequently, the TightRope is tightened on the tibial side and secured with the knee at 90° of flexion. The knee is then placed at 20° of flexion, and the femoral part of the ACL graft is tightened and secured with an outside-in bioabsorbable interference screw. With the use of a grasper or a shuttle suture, the suture tied to the gracilis is shuttled under the ITB through the incision made longitudinally through the ITB fibers and then through the skin incision made for the posterior end of the tibial bone tunnel. The ALL graft is shuttled through the tibial bone tunnel from posterior to anterior, using the previously passed suture loop (No. 2 Vicryl). The gracilis graft is brought back proximally again under the ITB and tied with FiberWire from the femoral end of the ACL graft with the patient's left knee in full extension and neutral rotation.

The treatment of cartilage defect remains a challenging issue in clinical practice. Chitosan- based materials have been recognized as a suitable microenvironment for chondrocyte adhesion, proliferation and differentiation forming articular cartilage. The use of nasal chondrocytes to culture articular cartilage on an appropriate scaffold emerged as a promising novel strategy for cartilage regeneration. Beside excellent properties, chitosan lacks in biological activity, such as RGD-sequences. In this work, we have prepared pure and protein- modified chitosan scaffolds of different deacetylation degree and molecular weight as platforms for the culture of sheep nasal chondrocytes. Fibronectin (FN) was chosen as an adhesive protein for the improvement of chitosan bioactivity. Prepared scaffolds were characterised in terms of microstructure, physical and biodegradation properties, while FN interactions with different chitosans were investigated through adsorption–desorption studies. The results indicated faster enzymatic degradation of chitosan scaffolds with lower deacetylation degree, while better FN interactions with material were achieved on chitosan with higher number of amine groups. Histological and immunohistochemical analysis of in vitro engineered cartilage grafts showed presence of hyaline cartilage produced by nasal chondrocytes.

Objective Nasal septal pathologies requiring surgical intervention are common in the population. Additionally, nasal chondrocytes are becoming an important cell source in cartilage tissue engineering strategies for the repair of articular cartilage lesions. These procedures damage the nasal septal cartilage whose healing potential is limited due to its avascular, aneural, and alymphatic nature. Despite the high incidence of various surgical interventions that affect septum cartilage, limited nasal cartilage repair characterizations have been performed to date. Methods To evaluate the healing of the nasal septum cartilage perforation, a septal biopsy was performed in 14 sheep. Two and 6 months later, the tissue formed on the place of perforation was explanted and compared with the native tissue. Tissue morphology, protein and gene expression of explanted tissue was determined using histological, immunohistochemical and real-time quantitative polymerase chain reaction analysis. Results Tissue formed on the defect site, 2 and 6 months after the biopsy was characterized as mostly connective tissue with the presence of fibroblastic cells. This newly formed tissue contained no glycosaminoglycans and collagen type II but was positively stained for collagen type I. Cartilage-specific genes COL2, AGG, and COMP were significantly decreased in 2- and 6-month samples compared with the native nasal cartilage. Levels of COL1, COL4, and CRABP1 genes specific for perichondrium and connective tissue were higher in both test group samples in comparison with native cartilage. Conclusions Newly formed tissue was not cartilage but rather fibrous tissue suggesting the role of perichondrium and mucosa in tissue repair after nasal septum injury.

Background Matrix metalloproteinases (MMPs) play an important role in matrix remodelling, as well as in tendon integrity. Due to overuse, athletes often develop chronic tendinopathies. If not treated, they lead to severe impairment, even complete tendon ruptures. Aim The main purpose of this study was to investigate whether three functional polymorphisms within the MMP3 gene are associated with increased risk of developing tendinopathies in high-level Croatian athletes. Methods We have recruited one hundred fifty- five (63 high-level athletes with diagnosed tendinopathies and 92 asymptomatic controls) unrelated Caucasians for this case- control genetic study. All participants were genotyped for three single nucleotide polymorphisms (SNP) within the MMP3 gene: rs591058 C/T, rs650108 A/G and rs679620 G/A using the pyrosequencing method. Results The MMP3 rs650108 GG (P = 0.0074) and rs679620 AA (P = 0.0119) genotypes were significantly over-represented in cases compared with controls, while rs591058 TT (P = 0.0759), as well as haplotype variant T - G - A (P = 0.06), implicated that there is an indication of predisposition for tendinopathies. Conclusion These results support association between functional variants within the MMP3 gene and the risk of tendinopathies in high-level athletes. Further research is needed to replicate these results in a larger population.

Matrix metalloproteinases (MMPs) play an important role in matrix remodelling, as well as in tendon integrity. Due to overuse, athletes often develop chronic tendinopathies. If not treated, they lead to severe impairment, even complete tendon ruptures.The main purpose of this study was to investigate whether three functional polymorphisms within the MMP3 gene are associated with increased risk of developing tendinopathies in high-level Croatian athletes.We have recruited one hundred fifty-five (63 high-level athletes with diagnosed tendinopathies and 92 asymptomatic controls) unrelated Caucasians for this case-control genetic study. All participants were genotyped for three single nucleotide polymorphisms (SNP) within the MMP3 gene: rs591058 C/T, rs650108 A/G and rs679620 G/A using the pyrosequencing method.The MMP3 rs650108 GG (P = 0.0074) and rs679620 AA (P = 0.0119) genotypes were significantly over-represented in cases compared with controls, while rs591058 TT (P = 0.0759), as well as haplotype variant T - G - A (P = 0.06), implicated that there is an indication of predisposition for tendinopathies.These results support association between functional variants within the MMP3 gene and the risk of tendinopathies in high-level athletes. Further research is needed to replicate these results in a larger population.

Izolirana rekonstrukcija prednjeg križnog ligamenta (ACL) predstavlja zlatni standard u kirurškom liječenju rupture prednjeg križnog ligamenta. No, neuspjeh cijeljenja presatka i ostatna rotacijska nestabilnost koljena i dalje su česte postoperativne komplikacije. Anterolateralni ligament (ALL) i njegova uloga u kontroli rotacijske stabilnosti dobila je značajan interes 2013. nakon objave njegova „ponovnog otkrića”. Ta ligamentarna struktura, opisana još davne 1879., potječe od proksimalnog i stražnjeg dijela lateralnog epikondila bedrene kosti i hvata se na goljeničnoj kosti, na sredini između Gerdyjeva tuberkla i glavice fibule. Biomehanička ispitivanja pokazala su da anterolateralni ligament djeluje kao pasivni stabilizator koljena tijekom unutarnje rotacije koljena, i kod rupture ACL-a i lateralnih struktura koljena odgovoran je za nastanak pivot-shift fenomena. Pokazalo se da izolirana rekonstrukcija ACL-a u pacijenata s ozljedom ACL-a i ALL-a ne može vratiti normalnu kinematiku koljena, za razliku od njihove kombinirane rekonstrukcije. Uz to, dosadašnja literatura nudi brojne dokaze u smislu poboljšanja stabilnosti koljena nakon kombiniranog postupka rekonstrukcije ACL-a i ALL-a. Štoviše, nedavne kliničke studije pokazale su da ALL ima zaštitni učinak na očuvanje presatka ACL-a, kao i na brži ponovni povratak u sport i opće zadovoljstvo pacijenata s operativnim zahvatom. Ovaj pregledni rad ima za cilj dati pregled dosadašnjeg znanja anatomije, funkcije i učinka rekonstrukcije ACL-a i ALL-a u pacijenata s puknućem ACL-a.

Objectives Bioreactor-based production systems have the potential to overcome limitations associated with conventional tissue engineering manufacturing methods, facilitating regulatory compliant and cost-effective production of engineered grafts for widespread clinical use. In this work, we established a bioreactor-based manufacturing system for the production of cartilage grafts. Materials & methods All bioprocesses, from cartilage biopsy digestion through the generation of engineered grafts, were performed in our bioreactor-based manufacturing system. All bioreactor technologies and cartilage tissue engineering bioprocesses were transferred to an independent GMP facility, where engineered grafts were manufactured for two large animal studies. Results The results of these studies demonstrate the safety and feasibility of the bioreactor-based manufacturing approach. Moreover, grafts produced in the manufacturing system were first shown to accelerate the repair of acute osteochondral defects, compared to cell-free scaffold implants. We then demonstrated that grafts produced in the system also facilitated faster repair in a more clinically relevant chronic defect model. Our data also suggested that bioreactor-manufactured grafts may result in a more robust repair in the longer term. Conclusion By demonstrating the safety and efficacy of bioreactor-generated grafts in two large animal models, this work represents a pivotal step towards implementing the bioreactor-based manufacturing system for the production of human cartilage grafts for clinical applications. Read the Editorial for this article on doi:10.1111/cpr.12625.

Aim To assess whether an adenoviral vector carrying the bone morphogenetic protein genes (Ad.BMP-2) can transduce human muscle tissue and direct it toward osteogenic differentiation within one hour. Methods This in vitro study, performed at the Department of Molecular Biology, Faculty of Science, Zagreb from 2012 to 2017, used human muscle tissue samples collected during anterior cruciate ligament reconstructions performed in St Catherine Hospital, Zabok. Samples from 28 patients were transduced with adenoviral vector carrying firefly luciferase cDNA (Ad.luc) by using different doses and times of transduction, and with addition of positive ions for transduction enhancement. The optimized protocol was further tested on muscle samples from three new patients, which were transduced with Ad.BMP-2. Released bone morphogenetic protein 2 (BMP-2) levels in osteogenic medium were measured every three days during a period of 21 days. Expression of osteogenic markers was measured at day 14 and 21. After 21 days of cultivation, muscle tissue was immunohistochemically stained for collagen type I detection (COL-I). Results The new transduction protocol was established using 108 plaque-forming units (P < 0.001) as an optimal dose of adenoviral vector and 30 minutes (P < 0.001) as an optimal contact time. Positive ions did not enhance transduction. Samples transduced with Ad.BMP-2 according to the optimized protocol showed enhanced expression of osteogenic markers (P < 0.050), BMP-2 (P < 0.001), and COL I. Conclusion This study confirms that Ad.BMP-2 can transduce human muscle tissue and direct it toward osteogenic differentiation within 30 minutes.

Orthopedic surgeons sometimes combine recombinant, human BMP-2 with autograft bone when dealing with problematic osseous fractures. Although some case reports indicate success with this off-label strategy, there have been no randomized controlled trials. Moreover, a literature search revealed only one pre-clinical study and this was in a cranial defect model. The present project examined the consequences of combining BMP-2 with particles of living bone in a rat femoral defect model. Human bone particles were recovered with a reamer-irrigator-aspirator (RIA). To allow acceptance of the xenograft as surrogate autograft, rats were administered an immunosuppressive cocktail that does not interfere with bone healing. Implantation of 200 µg living bone particles generated a small amount of new bone and defects did not heal. Graded amounts of BMP-2 that alone provoked no healing (1.1 µg), borderline healing (5.5 µg), or full healing (11 µg) were added to this amount of bone particles. Addition of BMP-2 (1.1 µg) increased osteogenesis, and produced bridging in 2 of 7 defects. The combination of BMP-2 (5.5 µg) and bone particles made healing more reliable and advanced the maturation of the regenerate. Bone formation with BMP-2 (11 µg) and bone particles showed improved maturation. Thus, the combination of autograft and BMP-2 may be helpful clinically under conditions where the healing response is suboptimal. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2137-2145, 2016. Clinical significance These data support the clinical use of recombinant, human BMP-2 with autograft bone when treating large segmental osseous defects. The combination leads to greater bone formation and accelerates the maturation of the regenerate.

Bone autografting remains the clinical treatment of choice for resolving problematic fractures. The precise mechanisms through which the autograft promotes bone healing are unknown. The present study examined the hypothesis that cells within the autograft secrete osteogenic factors promoting the differentiation of mesenchymal stem cells (MSCs) into osteoblasts. Particles of human bone (“chips”) were recovered at the time of joint replacement surgery and placed in culture. Then, conditioned media were added to cultures of human, adipose-derived MSCs under both basal and osteogenic conditions. Contrary to expectation, medium conditioned by bone chips reduced the expression of alkaline phosphatase and strongly inhibited mineral deposition by MSCs cultured in osteogenic medium. Real time PCR revealed the inhibition of collagen type I alpha 1 chain (Col1A1) and osteopontin (OPN) expression. These data indicated that the factors secreted by bone chips inhibited the osteogenic differentiation of MSCs. However, in late cultures, bone morphogenetic protein-2 (BMP-2) expression was stimulated, suggesting the possibility of a delayed, secondary osteogenic effect. © A Atasoy-Zeybek et al. Türkiye Bilimsel ve Teknolojik Araştirma Kurumu The work of A. Atasoy-Zeybek was supported by The Scientific and Technological Research Council of Turkey (TUBITAK)-BIDEB 2211-A domestic scholarship for PhD studies.

The main goal of this study was the formation of bone tissue using dexamethasone (DEX)-loaded [COCH3]-RADARADARADARADA-[CONH2] (RADA 16-I) scaffold that has the ability to release optimal DEX concentration under perfusion force. Bone-marrow samples were collected from three patients during a hip arthroplasty. Human mesenchymal stem cells (hMSCs) were isolated and propagated in vitro in order to be seeded on scaffolds made of DEX-loaded RADA 16-I hydrogel in a perfusion bioreactor. DEX concentrations were as follows: 4 &times, 10&minus, 3, 4 &times, 4 and 4 &times, 5 M. After 21 days in a perfusion bioreactor, tissue was analyzed by scanning electron microscopy (SEM) and histology. Markers of osteogenic differentiation were quantified by real-time polymerase chain reaction (RT-PCR) and immunocytochemistry. Minerals were quantified and detected by the von Kossa method. In addition, DEX release from the scaffold in a perfusion bioreactor was assessed. The osteoblast differentiation was confirmed by the expression analysis of osteoblast-related genes (alkaline phosphatase (ALP), collagen I (COL1A1) and osteocalcin (OC). The hematoxylin/eosin staining confirmed the presence of cells and connective tissue, while SEM revealed morphological characteristics of cells, extracellular matrix and minerals&mdash, three main components of mature bone tissue. Immunocytochemical detection of collagen I is in concordance with given results, supporting the conclusion that scaffold with DEX concentration of 4 &times, 4 M has the optimal engineered tissue morphology. The best-engineered bone tissue is produced on scaffold loaded with 4 &times, 4 M DEX with a perfusion rate of 0.1 mL/min for 21 days. Differentiation of hMSCs on DEX-loaded RADA 16-I scaffold under perfusion force has a high potential for application in regenerative orthopedics.

[EN] The extensive need for hard tissue substituent greatly motivates development of suitable allogeneic grafts for therapeutic recreation. Different calcium phosphate phases have been accepted as scaffold's components with positive influence on osteoinduction and differentiation of human mesenchymal stem cells, in terms of their higher fraction within the graft. Nevertheless, the creation of unlimited nutrients diffusion through newly formed grafts is of great importance. The media flow accomplished by perfusion forces can provide physicochemical, and also, biomechanical stimuli for three-dimensional bone-construct growth. In the present study, the influence of a different scaffold's composition on the human mesenchymal stem cells (hMSCs) differentiation performed in a U-CUP bioreactor under perfusion conditioning was investigated. The histological and immunohistochemical analysis of cultured bony tissues, and the evaluation of osteogenic genes' expression indicate that the lower fraction of in situ formed hydroxyapatite in the range of 10-30% within chitosan scaffold could be preferable for bone-construct development., BICRO PoC5_1_82, the Croatian Science Foundation under the project IP-2014-09-3752 and L'Oreal-UNESCO Foundation 'ForWomen in Science' are gratefully acknowledged.

The aim of this study is to examine the capacity of muscle tissue preserved on hamstring tendons forming candy-stripe grafts in order to improve tendon to bone ingrowth and ligamentization. We hypothesized that muscle tissue does possess a stem cell population that could enhance the healing process of the ACL graft when preserved on the tendons. Human samples from gracilis and semitendinosus muscles were collected during ACL surgery from ten patients and from these tissue samples human muscle-derived stem cells and tendon- derived stem cells were isolated and propagated. Both stem cell populations were in- vitro differentiated into osteogenic lineage. Alkaline phosphatase activity was determined at days zero and 14 of the osteogenic induction and von Kossa staining to assess mineralization of the cultures. Total RNA was collected from osteoblast cultures and real time quantitative PCR was performed. Western-blot for osteocalcin and collagen type I followed protein isolation. Immunofluorescence double labeling of pericytes in muscle and tendon tissue was performed. Mesenchymal stem cells from muscle and tendon tissue were isolated and expanded in cell culture. More time was needed to grow the tendon derived culture compared to muscle derived culture. Muscle derived stem cells exhibited more alkaline phosphatase actvity compared to tendon derived stem cells, whereas tendon derived stem cells formed more mineralized nodules after 14 days of osteoinduction. Muscle derived stem cells exhibited higher expression levels of bone sialoprotein, and tendon derived stem cells showed higher expression of dental-matrix- protein 1 and osteocalcin. Immunofluorescent staining against pericytes indicated that they are more abundant in muscle tissue. These results indicate that muscle tissue is a better source of stem cells than tendon tissue. Achievement of this study is proof that there is vast innate capacity of muscle tissue for enhancement of bone-tendon integration and ligamentization of ACL hamstring grafts and consequently muscle tissue should not be treated as waste after harvesting.

The aim of this chapter is to describe the main issues of bone tissue engineering. Bone transplants are widely used in orthopedic, plastic and reconstructive surgery. Current technologies like autologous and allogenic transplantation have several disadvantages making them relatively unsatisfactory, like donor site morbidity, chronic pain, and immunogenicity and risk hazard from infectious disease. Therefore, regenerative orthopedics seeks to establish a successful protocol for the healing of severe bone damage using engineered bone grafts. The optimization of protocols for bone graft production using autologous mesenchymal stem cells loaded on appropriate scaffolds, exposed to osteogenic inducers and mechanical force in bioreactor, should be able to solve the current limitations in managing bone injuries. We discuss mesenchymal stem cells as the most suitable cell type for bone tissue engineering. They can be isolated from a variety of mesenchymal tissues and can differentiate into osteoblasts when given appropriate mechanical support and osteoinductive signal. Mechanical support can be provided by different cell scaffolds based on natural or synthetic biomaterials, as well as combined composite materials. Three-dimensional support is enabled by bioreactor systems providing several advantages as mechanical loading, homogeneous distribution of cells and adequate nutrients/waste exchange. We also discuss the variety of osteoinductive signals that can be applied in bone tissue engineering. The near future of bone healing and regeneration is closely related to advances in tissue engineering. The optimization of protocols of bone graft production using autologous mesenchymal stem cells loaded on appropriate scaffolds, exposed to osteogenic inducers and mechanical force in bioreac‐ tor, should be able to solve the current limitations in managing bone injuries.

Development of artificial materials for the facilitation of cartilage regeneration remains an important challenge in orthopedic practice. Our study investigates the potential for neocartilage formation within a synthetic polyester scaffold based on the polymerization of high internal phase emulsions. The fabrication of polyHIPE polymer (PHP) was specifically tailored to produce a highly porous (85%) structure with the primary pore size in the range of 50–170 μm for cartilage tissue engineering. The resulting PHP scaffold was proven biocompatible with human articular chondrocytes and viable cells were observed within the materials as evaluated using the Live/Dead assay and histological analysis. Chondrocytes with round nuclei were organized into multicellular layers on the PHP surface and were observed to grow approximately 300 μm into the scaffold interior. The accumulation of collagen type 2 was detected using immunohistochemistry and chondrogenic specific genes were expressed with favorable collagen type 2 to 1 ratio. In addition, PHP samples are biodegradable and their baseline mechanical properties are similar to those of native cartilage, which enhance chondrocyte cell growth and proliferation.

Background:Proximal diaphyseal stress fractures of the fifth metatarsal are common in athletes. Conservative treatment has been shown to result in high rates of delayed union, nonunion, and refracture, so internal fixation has become the treatment of choice in competitive athletes.Methods:Twenty top-level athletes with diaphyseal stress fractures fixed with intramedullary malleolar screws were evaluated. Functional outcome was assessed by American Orthopaedic Foot and Ankle Society midfoot score. Static and dynamic maximum vertical force and peak plantar pressures were evaluated with a computerized pedobarograph.Results:Mean follow-up from surgery to interview was 10.3 years (range, 3.5–19.0 years). Clinical healing was 95%, and there has been one refracture (5%). The mean time from surgery to return to sport was 9 weeks (range, 5–14 weeks). Twelve athletes (60%) returned to a higher level of training, 7 (35%) to the same level, and 1 (5%) to a lower level compared with the level of training before injury. Average American Orthopaedic Foot and Ankle Society midfoot score was 93.8 (range, 85–100). During the computerized pedobarographic evaluations, 18 patients (90%) presented with varus of the metatarsus and the midfoot and 2 (10%) presented with a normal plantigrade foot.Conclusions:Intramedullary malleolar screws can yield reliable and effective healing of fifth metatarsal stress fractures in athletes. Varus of the metatarsus and the midfoot were predisposing factors for stress fractures in this population of competitive athletes, and all were recommended to wear orthoses until their competitive careers were completed. (J Am Podiatr Med Assoc 101(6): 517–522, 2011)

The aim of this study was to present long-term results of sagittal osteotomy of the patella after Morscher. The study included 70 patients treated for patellar dysplasia with a postoperative follow-up from nine to 20 years. There were 59 females and 11 males with an average age of 21 years at the time of operation. Results were evaluated for the entire group of 70 patients and then presented separately for the 30 patients in whom sagittal osteotomy of the patella was performed as a single procedure and 40 patients in whom, in addition to sagittal osteotomy of the patella, medialisation and ventralisation or distalisation of the tibial tuberosity were also performed. The mean value of the Wiberg patellar angle was 112 degrees preoperatively and 140 degrees postoperatively. In the whole group of patients excellent results were obtained in 24 (35%), good results in 30 (42%), fair results in 13 (19%) and poor results in three (4%) patients. In 30 patients with sagittal osteotomy as a single operation excellent results were obtained in 13 (43%), good results in 14 (47%) and fair results in three (10%) patients, while in the 40 patients with sagittal osteotomy and additional surgical procedures, 11 (27%) were excellent, 16 (40%) good, ten (25%) fair and three (8%) had poor results. Sagittal osteotomy of the patella after Morscher is an enrichment of the spectrum of the secondary-causal and preventive procedures for the treatment of patello-femoral disorders.

AIM: Determine the levels of expression of pluripotency genes OCT-4 and SOX-2 before and after osteogenic differentiation of human mesenchymal stem cells (hMSCs).METHODS: Human MSCs were derived from the bone marrow and differentiated into osteoblasts. The analyses were performed on days 0 and 14 of the cell culture. In vitro differentiation was evaluated due to bone markers – alkaline phosphatase (AP) activity and the messenger RNA (mRNA) expression of AP and bone sialoprotein (BSP). The OCT-4 and SOX-2 expression was evaluated at mRNA level by real-time qPCR and at protein level by immunocytochemistry.RESULTS: In vitro cultures on day 14 showed an increase in AP activity and upregulation of AP and BSP gene expression. OCT-4 and SOX-2 in undifferentiated hMSCs on day 0 is detectable and very low compared to tumor cell lines as a positive control. Immunocytochemistry detected OCT-4 in the cell nuclei prior (day 0) and post differentiation (day 14). On the same time points, cultures were negative for SOX-2 protein.CONCLUSION: Messenger RNA for pluripotency markers OCT-4 and SOX-2 isolated from hMSCs was less present, while OCT-4 protein was detected in cell nuclei prior and post differentiation into osteoblast lineage.

The last three decades have witnessed a tremendous increase in female sports participation at all levels. However, increased sports participation of female athletes has also increased the incidence of sport-related injuries, which can be either acute trauma or overuse injuries. Overuse injuries may be defined as an imbalance caused by overly intensive training and inadequate recovery, which subsequently leads to a breakdown in tissue reparative mechanisms. This article will review the most frequent overuse injuries in female athletes in the context of anatomical, physiological, and psychological differences between genders.

Usual clinical practice for autologous chondrocyte implantation (ACI) involves harvesting of articular cartilage from non- weightbearing part of the joint. Although effective, it induces additional trauma to the joint and additional surgical procedure with anesthesia. Alternative source of chondrocytes would substantially decrease morbidity and duration of the procedure, as well as the cost of the procedure. Nasal chondrocytes could be viable alternative for ACI in human patients. Before using it in clinical settings, it is necessary to test this hypothesis on translational (large animal) model. Designed model was chronic, full-thickness cartilage defect placed on lateral and medial femoral condyles in sheep. The protocol included two surgical procedures. First procedure was to create two partial-thickness defects, 4 mm in diameter on the lateral and medial femoral condyle with a standard mosaicplasty instruments used in human orthopaedic surgery. Biopsy of nasal septum cartilage was also performed with skin biopsy puncher, 8 mm in diameter. Cartilage samples from both origins were used for production of autologous tissue grafts. Chondrocytes were isolated, seeded on biphasic collagen-hydroxiapatite scaffolds, and cultured in automated bioreactor for 5 weeks. Engineered tissue was then implanted in condyle defects during second procedure. First, 4 mm partial-thickness defects were converted to osteochondral defects 6, 5 mm in diameter and 5 mm deep. Then engineered cartilage tissue was implanted. There were four study groups. Autologous tissue grafts, engineered from scaffold and nasal septum chondrocytes were implanted in the experimental group of animals. One group was implanted with autologous tissue grafts engineered from scaffold and articular chondrocytes. In one group cell free scaffolds were implanted while last group served as negative control in which only conversion of defect was performed, but it was left untreated. Animals were sacrificed and tissue analysis was performed at three different time points: 6 weeks, 3 months and 12 months after the implantation. Tissue analysis included macroscopic, microscopic and molecular evaluation. ICRS score was used to evaluate macroscopic apperance of the repair tissue. Microscopic analysis included different stains (hematoxylin-eosin, safranin O, picrosirius) and immunohistochemistry (collagen I, II and aggrecan) to determine the type of repair tissue, organization of collagen and integration. Semi-quantitative data of morphology were obtained with histological score ICRS II. ELISA and DMMB assays were performed to quantify the amount of collagen I, II and glycosaminoglycans in repair tissue. Results confirmed the feasibility of production of autologous cartilage tissue grafts from nasal septum chondrocyte for treatment of condyle cartilage defects. Furthermore, nasal chondrocyte grafts showed promising results in restoration of damaged articular cartilage. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n°278807.

Bone defects, including normal fracture healing as well as healing prob- lems represent a global health problem. The need for better treatment of bone defects is one of the central issues of tissue engineering and regenerative medicine. Regenerative orthopedics has several approaches – activation of endogenous stem cells, stem cell therapy and tissue engineering. Development of new treatments is mainly focused on the tissue engineering strategies that include stem cells, bioactive signals and appropriate scaffold support. The aim of this review is to describe a variety of stem cells that have an ability to become bone cells and therefore are of central importance for bone tissue engineering. Several cell types have been proposed as starting material - embryonic stem cells, induced pluripotent stem cells and adult stem cells. Due to ethical and safety issues, embryonic and induced pluripotent stem cells may be more suitable for studying human development and tissue for- mation under diverse experimental conditions, and represent an excellent base for understanding human diseases and development of innovative therapeutic solutions. Among adult stem cells, mesenchymal stem cells are the most suitable for bone tissue engineering. They can be isolated from variety of mesenchymal tissues and can differentiate into osteoblasts when given appropriate mechanical support and osteoinductive signal. The near future of bone healing and regeneration is closely related to advances in tissue engineering. The optimization of protocols of bone graft production using autologous mesenchymal stem cells loaded on appropriate scaffolds, exposed to osteogenic inducers and mechanical force in bioreactor, should be able to solve the current limitations in managing bone injuries.

Osteogenesis imperfecta or brittle bone disease, a heritable disorder of connective tissue, is the most common of the inherited disorders primarily affecting bone. There are approximately 400 individuals with OI in Croatia alone. It is estimated that twice that number is present, represented by individuals with mild OI in whom the diagnosis has not been made. Due to the relatively low number of patients in the general population, treating physicians have limited experience with this disease, either with children or adults. The basis of this disease in European populations is mostly the result of defects in the structure or processing of collagen type I, an important protein of the extracellular matrix of many tissues. Presently, molecular defects in 16 different genes have been discovered to result in at least one type of OI of which 14 are not COL1 mutation loci. Although fractures occurring with no injury or minor injury are the hallmark of OI, other non-mineralized tissues can be affected as well and the pathological changes can be present in skin, tendons, eyes, teeth and blood vessels. Clinical manifestations are very heterogeneous and numerous signs and symptoms such as blue sclera, deafness, abnormal teeth development, joint hypermobility, increased risk of hernias, capillary fragility, aneurysms etc. Although there is no cure for this disease, there are specific therapies that can reduce the pain and complications associated with OI. The purpose of this review is to provide a brief overview of the molecular basis of this disease, describe clinical presentations, as well as to present orthopaedic therapeutic modalities for the patients with OI.

The localized form of pigmented villonodular synovitis (LPVS) is a lesion characterized by focal involvement of the synovial membrane. The knee is the most commonly affected joint. We report three cases of LPVS of the knee which were not diagnosed upon clinical evaluation. The aim is to bring the attention of clinicians to this pathological entity, which is often regarded as extremely rare and is therefore not considered in the early differential diagnosis of various knee derangements. Diagnostic and therapeutic arthroscopy was performed. The lesions were completely resected and patohistological findings confirmed the diagnosis of LPVS. All of our three patients have remained asymptomatic at 8, 10, and 12-month follow-ups.

Background: Femoral shaft stress fractures in athletes are not common but pose a great diagnostic challenge to clinicians. Because of few clinical signs, diagnosis and treatment are often delayed. Furthermore, if not treated correctly, these fractures are well known for complications and difficulties. Objective: To develop a well structured and reproducible treatment algorithm for athletes with femoral shaft stress fractures. Methods: The proposed algorithm is carried out in four phases, each lasting three weeks, and the move to the next phase is based on the result of the tests carried out at the end of the previous phase. Over nine years, we treated seven top level athletes, aged 17–21. In all athletes, diagnosis was based on physical examination, plain radiographs, and bone scan. Results: As a result of the treatment method, all the athletes were fully engaged in athletic activity 12–18 weeks after the beginning of treatment. After completion of the treatment, the athletes were followed up for 48–96 months. During the follow up, there was no recurrence of discomfort or pain, and all the athletes eventually returned to competition level. Conclusion: These results and data available from the literature suggest that the algorithm is the optimal treatment protocol for femoral shaft stress fractures in athletes, avoiding the common complications and difficulties.

The purpose of this paper is to review current developments in bone tissue engineering, with special focus on the promising role of nanobiotechnology. This unique fusion between nanotechnology and biotechnology offers unprecedented possibilities in studying and modulating biological processes on a molecular and atomic scale. First we discuss the multiscale hierarchical structure of bone and its implication on the design of new scaffolds and delivery systems. Then we briefly present different types of nanostructured scaffolds, and finally we conclude with nanoparticle delivery systems and their potential use in promoting bone regeneration. This review is not meant to be exhaustive and comprehensive, but aims to highlight concepts and key advances in the field of nanobiotechnology and bone regeneration.

We report on 2 cases of hyperextension/valgus elbow injuries in two adult male national team water polo goalkeepers. Both were healthy and had never sustained any major injuries of the elbow. Mechanism and type of injury in both of them was identical. Different medical treatment protocols of these injuries possibly have led to different outcomes, with one of them developing osteochondritis dissecans (OCD). Inadequate medical treatment of acute impact elbow injuries could lead to osteochondritis disecans of the elbow in top-level adult male water polo goalkeepers.

The restoration of damaged articular cartilage remains one of the biggest challenges in modern clinical orthopaedics. There is no pharmacological treatment that promotes the repair of cartilage, and non-operative treatment inevitably leads to the development of premature osteoarthritis. Current treatment modalities include microfracture, transplantation of osteochondral grafts and autologous chondrocyte implantation (ACI), each having its own benefits and shortcomings. New biological approaches to cartilage repair that are based on the use of cells and molecules that promote chondrogenesis and/or inhibit cartilage breakdown offer a promising alternative to current treatment options. Chondrogenesis is a precisely orchestrated process which involves many growth factors and signaling molecules, and by modifying the local cellular environment, it is possible to enhance formation of more natural cartilage tissue within the defect. These bioactive molecules are difficult to administer effectively. For those that are proteins or RNA molecules, gene transfer has emerged as an attractive option for their sustained synthesis at the site of repair. To accomplish this task, two main strategies have been explored. The direct or in vivo approach delivers exogenous DNA directly into the joint. In this case synovial lining cells are the main site of gene transfer; depending on the vector, cells around or within the defect may also be genetically modified. During indirect or ex vivo delivery, cells are recovered, genetically manipulated outside the body, and then returned to the defect. Delivery of the genetic material to the living cell can be accomplished by use of either viral or non-viral vectors. While viral vectors are much more effective, they raise several safety concerns. Numerous preclinical animal studies have confirmed the effectiveness of these approaches in joints, and several phase I and II clinical gene therapy studies in the local treatment of arthritis provide reason for cautious optimism. This chapter will provide insight into the field of gene therapy in cartilage repair, and its potential for safe and effective clinical translation.

Stress fractures are common overuse injuries of the bone that are most often seen in athletes and military personnel. These types of injuries seem to be commonly missed or delayed in diagnosis. Physicians should consider the possibility of such an injury while determining the diagnosis of a long-lasting foot pain. The aim of this paper was to report an isolated stress fracture of the lateral cuneiform bone. A review of the literature failed to find a similar case. (J Am Podiatr Med Assoc 103(4): 337–339, 2013)

Background: Large segmental defects in bone do not heal well and present clinical challenges. This study investigated modulation of the mechanical environment as a means of improving bone healing in the presence of bone morphogenetic protein (BMP)-2. Although the influence of mechanical forces on the healing of fractures is well established, no previous studies, to our knowledge, have described their influence on the healing of large segmental defects. We hypothesized that bone-healing would be improved by initial, low-stiffness fixation of the defect, followed by high-stiffness fixation during the healing process. We call this reverse dynamization. Methods: A rat model of a critical-sized femoral defect was used. External fixators were constructed to provide different degrees of stiffness and, importantly, the ability to change stiffness during the healing process in vivo. Healing of the critical-sized defects was initiated by the implantation of 11 mg of recombinant human BMP (rhBMP)-2 on a collagen sponge. Groups of rats receiving BMP-2 were allowed to heal with low, medium, and high-stiffness fixators, as well as under conditions of reverse dynamization, in which the stiffness was changed from low to high at two weeks. Healing was assessed at eight weeks with use of radiographs, histological analysis, microcomputed tomography, dual x-ray absorptiometry, and mechanical testing. Results: Under constant stiffness, the low-stiffness fixator produced the best healing after eight weeks. However, reverse dynamization provided considerable improvement, resulting in a marked acceleration of the healing process by all of the criteria of this study. The histological data suggest that this was the result of intramembranous, rather than endochondral, ossification. Conclusions: Reverse dynamization accelerated healing in the presence of BMP-2 in the rat femur and is worthy of further investigation as a means of improving the healing of large segmental bone defects. Clinical Relevance: These data provide the basis of a novel, simple, and inexpensive way to improve the healing of critical-sized defects in long bones. Reverse dynamization may also be applicable to other circumstances in which bonehealing is problematic.

Articular cartilage is an avascular and aneural tissue lacking lymph drainage, hence its inability of spontaneous repair following injury. Thus, it offers an interesting model for scientific research. A number of methods have been suggested to enhance cartilage repair, but none has yet produced significant success. The possible application of the aforementioned methods has brought about the necessity to evaluate their results. The objective of this study was to analyze results of a study of the effects of the use of TGF-beta gene transduced bone marrow clot on articular cartilage defects using ICRS visual histological assessment scale.The research was conducted on 28 skeletally mature sheep that were randomly assigned to four groups and surgically inflicted femoral chondral defects. The articular surfaces were then treated with TGF-beta1 gene transduced bone marrow clot (TGF group), GFP transduced bone marrow clot (GFP group), untransduced bone marrow clot (BM group) or left untreated (NC group). The analysis was performed by visual examination of cartilage samples and results were obtained using ICRS visual histological assessment scale. The results were subsequently subjected to statistical assessment using Kruskal-Wallis and Mann-Whitney tests.Kruskal-Wallis test yielded statistically significant difference with respect to cell distribution. Mann-Whitney test showed statistically significant difference between TGF and NC groups (P = 0.002), as well as between BM and NC groups (P = 0.002 with Bonferroni correction).Twenty-six of the twenty-eight samples were subjected to histologic and subsequent statistical analysis; two were discarded due to faulty histology technique. Our results indicated a level of certainty as to the positive effect of TGF-beta1 gene transduced bone marrow clot in restoration of articular cartilage defects. However, additional research is necessary in the field. One of the significant drawbacks on histologic assessment of cartilage samples were the errors in histologic preparation, for which some samples had to be discarded and significantly impaired the analytical quality of the others. Defects of structures surrounding the articular cartilage, e.g., subchondral bone or connective tissue, might also impair the quality of histologic analysis. Additional analyses, i.e. polarizing microscopy should be performed to determine the degree of integration of the newly formed tissue with the surrounding cartilage. The semiquantitative ICRS scale, although of great practical value, has limitations as to the objectivity of the assessment, taking into account the analytical ability of the evaluator, as well as the accuracy of semiquantitative analysis in comparison to the methods of quantitative analysis.Overall results of histologic analysis indicated that the application of TGF-beta1 gene transduced bone marrow clot could have measurable clinical effects on articular cartilage repair. The ICRS visual histological assessment scale is a valuable analytical method for cartilage repair evaluation. In this respect, further analyses of the method value would be of great importance.

Total hip replacement (THR) has a very good clinical outcome. Peri-prosthetic infection is a severe complication with infection rates 0.5-2% after primary THR. Systematic reviews and meta-analyses published in recent years have allowed drafting of evidence based guidelines for diagnosis and treatment of peri-prosthetic infection after THR. If an implant related infection is suspected, a complex standardised procedure should be carried out. The most commonly cultured microorganisms causing peri-prosthetic infections are coagulase-negative staphylococci and S.aureus followed by mixed flora, streptococci, gram-negative bacilli, enterococci and anaerobes. Different treatment strategies can be applied regarding virulence of a specific pathogen, mechanical stability of the implant and patient's condition. Treatment options always include antibiotic therapy with/without surgical procedures like debridement, one/two stage approach or resection arthroplasty.

Clinical management of delayed healing or nonunion of long bone fractures and segmental bone defects poses a substantial orthopaedic challenge. Surgical advances and bone tissue engineering are providing new avenues to stimulate bone growth in cases of bone loss and nonunion. The reamer-irrigator-aspirator (RIA) device allows surgeons to aspirate the medullary contents of long bones and use the progenitor-rich “flow-through” fraction in autologous bone grafting. Dexamethasone (DEX) is a synthetic steroid that has been shown to induce osteoblastic differentiation. A series of 13 patients treated with RIA bone grafting enhanced with DEX for nonunion or segmental defect was examined retrospectively to assess the quality of bony union and clinical outcomes. Despite the initial poor prognoses, promising results were achieved using this technique ; and given the complexity of these cases the observed success is of great value and warrants controlled study into both standardisation of the procedure and concentration of the grafting material.

Orthopedic surgery is going through a serious paradigm shift ; instead of simply replacing damaged tissues with prosthetic or allograft material, the aim is to regenerate them. This endeavor has generated the field of regenerative orthopaedics, an increasingly expanding area of research with hopes of providing new and better treatments for diseases and injuries affecting the musculoskeletal system. As part of this process, we are witnessing a substantial accumulation of new cellular and molecular insights into connective tissue function, coupled with emerging new concepts in stem cell biology and scaffolding technologies. Indeed, any successful strategy to regenerate musculoskeletal tissues can be portrayed as an intricate interplay between the three main constituents of the regenerative system: cells, environment and scaffolds. This review is not meant to be exhaustive and comprehensive, but aims to highlight concepts and key advances in the field of regenerative orthopaedics and tissue engineering, as well as to present current possibilities for clinical translation.