Marko Pećina

Bone Morphogenetic Protein–7 (Osteogenic Protein–1) Promotes Tendon Graft Integration in Anterior Cruciate Ligament Reconstruction in Sheep

Background Bone morphogenetic proteins induce new bone both in patients with bone defects and at extraskeletal sites in animals. After anterior cruciate ligament rupture, tendon graft fixation into a bone tunnel is a widely used method for anterior cruciate ligament reconstruction. Hypothesis Bone morphogenetic protein–7 applied to the bone-tendon interface enables better integration of a free tendon graft into the surrounding bone. Study Design Controlled laboratory study. Methods The anterior cruciate ligament was reconstructed using a free tendon graft in the right rear knees of 30 one-year-old male sheep. Recombinant human bone morphogenetic protein–7 (25 μg) was applied randomly to the bone-tendon interface in 15 animals, and a vehicle was applied in 15 control animals. At 3 weeks, 10 animals from each group were sacrificed, and the remaining sheep were sacrificed at 6 weeks after surgery. Subsequently, histologic analysis and mechanical testing were performed. In another group of 20 sheep, the same procedure was used and mechanical testing was performed after 3 weeks. Results More new bone was formed at the bone-tendon interface in the knees treated with bone morphogenetic protein–7 as compared histologically with similar areas in control animals, creating areas of dense trabecular network with significantly greater invasion of the tendon fibrous tissue into the bone marrow space. Mechanical testing showed greater strain resistance to force (368 N) in the knees treated with bone morphogenetic protein–7 than in control specimens (214 N). There was no difference between mechanical testing of samples from 3 and 6 weeks after surgery. Conclusion Bone morphogenetic protein–7 promotes complete tendon graft integration into the newly formed surrounding trabecular bone in the reconstruction of the anterior cruciate ligament. Clinical Relevance Bone morphogenetic protein–7 in tendon graft integration might be successfully used in reconstructive surgery of ligaments.

The incidence of injuries in elite junior figure skaters.

Background There has been rapid growth in the technical and physiologic demands made on skaters who perform more and more difficult jumps, spins, lifts, throws, and free skating movements. Purpose To investigate the frequency of injuries and overuse syndromes in elite junior skaters. Study Design Questionnaire. Methods During four consecutive Junior World Figure Skating Championships and the Croatia Cup, we interviewed 236 female and 233 male skaters by questionnaire to determine the frequency of injuries and overuse syndromes. Results Fifty-nine of the female skaters (25%) and 65 of the male skaters (27.9%) reported sustaining acute injuries; 101 female (42.8%) and 106 male (45.5%) skaters reported overuse syndromes. Low back pain was reported by 19 female and 23 male skaters. The most frequent acute injury was ankle sprain. In singles female skaters, the most frequent overuse injury was stress fracture (19.8%), followed by jumpers knee (14.9%). In singles male skaters, jumpers knee (16.1%) was the most frequent injury, followed by Osgood-Schlatter disease (14.2%). More than 50% of injuries in young singles figure skaters involved overuse syndromes. Pairs skaters and ice dance skaters had a higher risk of acute injury than overuse syndrome because of falls from lifts and throw jumps. Conclusions Programs to improve postural alignment, flexibility, and strength, especially during the asynchronous period of bone and soft tissue development, should be instituted to prevent and reduce overuse syndromes.

Articular cartilage repair by genetically modified bone marrow aspirate in sheep

Bone marrow presents an attractive option for the treatment of articular cartilage defects as it is readily accessible, it contains mesenchymal progenitor cells that can undergo chondrogenic differentiation and, once coagulated, it provides a natural scaffold that contains the cells within the defect. This study was performed to test whether an abbreviated ex vivo protocol using vector-laden, coagulated bone marrow aspirates for gene delivery to cartilage defects may be feasible for clinical application. Ovine autologous bone marrow was transduced with adenoviral vectors containing cDNA for green fluorescent protein or transforming growth factor (TGF)-β1. The marrow was allowed to clot forming a gene plug and implanted into partial-thickness defects created on the medial condyle. At 6 months, the quality of articular cartilage repair was evaluated using histological, biochemical and biomechanical parameters. Assessment of repair showed that the groups treated with constructs transplantation contained more cartilage-like tissue than untreated controls. Improved cartilage repair was observed in groups treated with unmodified bone marrow plugs and Ad.TGF-β1-transduced plugs, but the repaired tissue from TGF-treated defects showed significantly higher amounts of collagen II (P<0.001). The results confirmed that the proposed method is fairly straightforward technique for application in clinical settings. Genetically modified bone marrow clots are sufficient to facilitate articular cartilage repair of partial-thickness defects in vivo. Further studies should focus on selection of transgene combinations that promote more natural healing.

Traumatic and Overuse Injuries Among International Elite Junior Rowers

Background Junior rowers have competed internationally for over 4 decades, and there are no epidemiological data available on traumatic and overuse injury in this population. Objective To define the types of musculoskeletal problems present in international elite-level junior rowers and to determine whether gender, physical stature, rowing discipline, and training programs affect the incidence of reported injuries. Study Design Descriptive epidemiology study. Methods Injury data were obtained from a total of 398 rowers (42% female, 58% male) who completed a 4-page questionnaire on injury incidence while participating at the Junior World Rowing Championships in Beijing, People’s Republic of China, in August 2007. Results Overall, 290 (73.8%) reported injuries involved overuse, and 103 (26.2%) were related to a single traumatic event. Female rowers were injured more frequently than male rowers (110.2 vs 90.5 injuries per 100 rowers). In both genders, the most common injury site was the low back followed by the knee and the forearm/wrist. The severity of reported injuries was incidental in 65.1%, minor in 21.4%, moderate in 10.4%, and major in 3.1% of cases. The rowers with traumatic injuries had less rowing experience than the uninjured rowers (median [C] ± interquartile range [Q] = 3 ± 3 years vs 4 ± 3 years; P = .043, Mann-Whitney test). Sweep rowers who changed rowing side during the current season had significantly more acute-onset low back injuries (P = .012, χ2 test) than those who did not change rowing side during the same period. The incidence of traumatic injuries was significantly lower in rowers who regularly performed more than 10 minutes of posttraining stretching (P = .030, χ2 test). Athletes who ran more than once a week had more overuse knee injuries than those who ran once or less per week (P = .033, χ2 test). Conclusion Elite junior rowers attending the World Rowing Championships reported predominantly overuse injuries of low severity during the current rowing season. Low back injuries were the most frequent complaint of elite-level junior rowers.

Influence of the acetabular cup position on hip load during arthroplasty in hip dysplasia

Placement of the acetabular cup during total hip arthroplasty is of great importance because usually every deviation from the ideal centre of rotation negatively influences endoprosthesis survival, polyethylene wear and hip load. Here we present hip load change in respect to various acetabular cup positions in female patients who underwent total hip replacement surgery due to hip dysplasia. The calculation suggests that, in the majority of cases, for every millimeter of lateral displacement of the acetabular cup (relative to the ideal centre of rotation) an increase of 0.7% in hip load should be expected and for every millimeter of proximal displacement an increase of 0.1% in hip load should be expected (or decreased if displacement is medial or distal). Also, for every millimeter of neck length increase, 1% decrease is expected and for every millimeter of lateral offset, 0.8% decrease is expected. Altogether, hip load decreases when the cup is placed more medially or distally and when the femoral neck is longer or lateral offset is used.RésuméLe positionnement de la cupule acétabulaire durant la réalisation d’une prothèse totale de hanche est très important car une déviation de la position idéale du centre de rotation peut influer de façon négative sur la survie, sur l’usure et sur les vecteurs de forces au niveau de la hanche. Nous présentons une étude qui permet de visualiser les vecteurs de forces en fonction des différentes positions de la cupule chez des patients de sexe féminin qui ont bénéficié d’une prothèse totale de hanche mise en place pour dysplasie. Les calculs permettent de penser que dans la majorité des cas chaque millimètre de latéralisation de la cupule augmente de 0,7% la charge au niveau de la hanche et que chaque déplacement proximal l’augmente de 0,1%. Ainsi chaque augmentation millimétrique de la longueur du col peut entraîner une diminution de 1% des forces, de même en ce qui concerne chaque millimètre d’offset latéral qui permet d’obtenir une diminution de 0,8%. En conclusion, les charges diminuent au niveau de la hanche quand la cupule est placée de façon plus médiane ou distale et quand les longueurs du col fémoral ou de l’offset son utilisées.

Discovery and Clinical Applications of Bone Morphogenetic Proteins

Significant progress has been made in the characterization of cartilage and bone differentiating proteins. A family of unique proteins known as bone morphogenetic proteins has been described, and there is ample evidence that they are directly responsible for de novo cartilage and bone formation in vivo. Extensive research is underway to develop appropriate and optimal delivery systems based on extracellular matrix components. It is likely that bone morphogenetic proteins will play a crucial role in bone and joint regeneration and repair.

Articular cartilage repair: the role of bone morphogenetic proteins.

Joint surface repair is still a major challenge in modernmedicine because the factors initiating cartilage forma-tion, maturation, and repair are poorly understood. Spe-cific biological challenges include the variable qualityand quantity of the cartilage produced, decreasing re-sponsiveness with age, bonding to the adjacent cartilage,and restoration of the subchondral bone [36]. Injury tocartilage initiates a specific reparative response. In le-sions of the articular cartilage with no collagen damage aloss of non-collagenous matrix occurs, leading eventual-ly to complete repair of the damaged matrix [6]. In moresevere cases, where there is a damage of the fibrillar net-work and cell death, the articular cartilage does not heal[33, 44].Over the past several decades in clinical orthopaedicwork, techniques to treat chondral defects included abra-sion, drilling, micro-fracturing of the underlying bone,tissue autografts, allografts, and cell transplantation [1,3, 15, 16, 21, 26, 27, 28, 34, 40, 41, 51]. In recent yearsmore has been learned about various growth factors thatstimulate chondrocyte differentiation and cartilage ma-trix production, but to date no procedure has been fullysuccessful in achieving properly structured regenerativearticular cartilage.

The clinical use of bone morphogenetic proteins revisited: a novel biocompatible carrier device OSTEOGROW for bone healing

PurposeThe purpose of this study was to revise the clinical use of commercial BMP2 (Infuse) and BMP7 (Osigraft) based bone devices and explore the mechanism of action and efficacy of low BMP6 doses in a novel whole blood biocompatible device OSTEOGROW.MethodsComplications from the clinical use of BMP2 and BMP7 have been systemically reviewed in light of their role in bone remodeling. BMP6 function has been assessed in Bmp6-/- mice by μCT and skeletal histology, and has also been examined in mesenchymal stem cells (MSC), hematopoietic stem cells (HSC) and osteoclasts. Safety and efficacy of OSTEOGROW have been assessed in rats and rabbits.ResultsClinical use issues of BMP2 and BMP7 have been ascribed to the limited understanding of their role in bone remodeling at the time of device development for clinical trials. BMP2 and BMP7 in bone devices significantly promote bone resorption leading to osteolysis at the endosteal surfaces, while in parallel stimulating exuberant bone formation in surrounding tissues. Unbound BMP2 and BMP7 in bone devices precipitate on the bovine collagen and cause inflammation and swelling. OSTEOGROW required small amounts of BMP6, applied in a biocompatible blood coagulum carrier, for stimulating differentiation of MSCs and accelerated healing of critical size bone defects in animals, without bone resorption and inflammation. BMP6 decreased the number of osteoclasts derived from HSC, while BMP2 and BMP7 increased their number.ConclusionsCurrent issues and challenges with commercial bone devices may be resolved by using novel BMP6 biocompatible device OSTEOGROW, which will be clinically tested in metaphyseal bone fractures, compartments where BMP2 and BMP7 have not been effective.

Biological aspects of bone, cartilage and tendon regeneration

Current orthopaedic procedures in supporting regeneration of bone, cartilage and tendon are dependant on our understanding of the molecular processes responsible for tissue repair. At present we know how to regenerate bone when physiological mechanisms of fracture repair fail [13]. Since the original description of the potential of demineralised bone matrix to induce bone at an ectopic site, it has taken more than 3 decades to bring bone morphogenetic proteins (BMPs) to clinical use. By the end of 2007 nearly 1 million patients worldwide will have been treated with BMPs for spinal fusions, non-unions, acute fractures and maxillofacial reconstruction. Use of animal models, genomics and proteomics has deciphered new mechanisms and candidate molecules for the regeneration of joint cartilage and tendons, opening new avenues in regenerative orthopaedics. This special issue reviews novel strategies in the regeneration of bone, cartilage and tendon. Bishop and Einhorn [2] describe the clinical use of recombinant BMP-2 and BMP-7. They predict that current techniques in engineering bone for restoring defined skeletal defects represent a unique opportunity for BMPs in the future. McKay and colleagues [9] review the clinical applications of BMP-2 (INFUSE Bone Graft), while Vaccaro, McKee and colleagues [14] describe the clinical applications of BMP-7 (OP-1 implant or Osigraft). The authors suggest that recombinant human BMP-based devices, when properly applied, can eliminate the need to harvest autologous bone for grafting procedures, benefiting both the surgeon and patients. Grgurevic and collaborators [6] describe molecules discovered by proteomic analysis in the plasma of patients with an acute bone fracture. The characterisation and use of potential new biomarkers, like TGF-β-induced protein IG-H3, cartilage acidic protein 1, procollagen C proteinase enhancer protein and TGF-β receptor III, for bone and cartilage regeneration are discussed. Sendak and colleagues [11] review the newly discovered role of thyroid-stimulating hormone (TSH) and follicle-stimulating hormone (FSH) in bone remodelling. It has been recently found that low doses of TSH increase bone volume and improve bone microarchitecture and strength in aged osteoporotic rats, suggesting that TSH directly affects bone remodelling in vivo [10]. Grasser and collaborators [5], by using a genomic approach, decipher the potential mechanism of bone augmentation following systemic administration of BMP-6, suggesting that IGF-1 and EGF mediate, at least in part, the effects of BMP-6 on bone, which has been recently reported [12]. The role of prostaglandin E2 receptors and their analogs in bone formation is reviewed by Li and colleagues [8], demonstrating that the PGE2 receptor is essential for restoring bone defects in animal models. Cartilage regeneration and chronic back pain due to degenerative disc disease are among major obstacles in orthopaedics. Chubinskaya and colleagues [4] summarise the role of osteogenic protein-1 (BMP-7) in animal models of osteochondral and chondral defects, osteoarthritis and degeneration in intervertebral disc cartilage. They show that OP-1 exhibits unique pro-anabolic and prominent anti-catabolic properties having a potential for treating cartilage and disc lesions. Overuse tendon disorders are common and associated with a significant morbidity. Tendon and ligament function engineering and repair are discussed in articles by Aspenberg [1] and by Hoffman and Gross [7]. Aspenberg found that the repair of subcutaneous tendon ruptures can be stimulated by a single application of one of several growth factors, including PDGF, TGF-β, IGF-1, VEGF and GDF-5,-6,-7, or by a thrombocite concentrate. The response is dependent on the mechanical microenvironment, which is crucial for the repair process. Hoffmann and Gross specifically discuss gene-therapeutic approaches using mesenchymal stem cells for a potential future application in tendon/ligament regeneration. Borovecki and colleagues [3] discuss the potential of a genomic approach in analysing bone homeostasis and diseases. Gene expression profiling studies yielded novel insights into the complex interplay of osteoblast and osteoclast regulation, paracrine and endocrine control of bone and cartilage remodelling, as well as the pathophysiology of osteoporosis and bone tumours. We believe that this issue will provide basic and clinical scientists with the state of the art knowledge in regenerative orthopaedics.

Regenerative medicine and tissue engineering in orthopaedic surgery.

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.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.