Orthopaedic

Osteolysis induced by ultra high molecular weight polyethylene wear debris is one of the primary factors limiting the lifespan of total hip replacements. Crosslinking polyethylene is known to improve its wear resistance in certain industrial applications, and crosslinked polyethylene acetabular cups have shown improved wear resistance in two clinical studies. In the present study, crosslinked polyethylene cups were produced by two methods. Chemically crosslinked cups were produced by mixing a peroxide with ultra high molecular weight polyethylene powder and then molding the cups directly to shape. Radiation-crosslinked cups were produced by exposing conventional extruded ultra high molecular weight polyethylene bar stock to gamma radiation at various doses from 3.3 to 100 Mrad (1 Mrad = 10 kGy), remelting the bars to extinguish residual free radicals (i.e., to minimize long-term oxidation), and then machining the cups by conventional techniques. In hip-joint simulator tests lasting as long as 5 million cycles, both types of crosslinked cups exhibited dramatically improved resistance to wear. Artificial aging of the cups by heating for 30 days in air at 80°C induced oxidation of the chemically crosslinked cups. However, a chemically crosslinked cup that was aged 2.7 years at room temperature had very little oxidation. Thus, whether substantial oxidation of chemically crosslinked polyethylene would occur at body temperature remains unclear. The radiationcrosslinked remelted cups exhibited excellent resistance to oxidation. Because crosslinking can reduce the ultimate tensile strength, fatigue strength, and elongation to failure of ultra high molecular weight polyethylene, the optimal crosslinking dose provides a balance between these physical properties and the wear resistance of the implant and might substantially reduce the incidence of wear-induced osteolysis with total hip replacements.

Using the knee joints of New Zealand White rabbits, a baseline study was made to determine the intrinsic capability of cartilage for healing defects that do not fracture the subchondral plate. A second experiment examined the effect of autologous chondrocytes grown in vitro on the healing rate of these defects. To determine whether any of the reconstituted cartilage resulted from the chondrocyte graft, a third experiment was conducted involving grafts with chondrocytes that had been labeled prior to grafting with a nuclear tracer. Results were evaluated using both qualitative and quantitative light microscopy. Macroscopic results from grafted specimens displayed a marked decrease in synovitis and other degenerative changes. In defects that had received transplants, a significant amount of cartilage was reconstituted (82%) compared to ungrafted controls (18%). Autoradiography on reconstituted cartilage showed that there were labeled cells incorporated into the repair matrix.

pro-uPA) activation on the surface of endothelial cells Vascular endothelial growth factor (VEGF) induces rapid prourokinase http://bloodjournal.hematologylibrary.org/content/103/3/955.full.html Updated information and services can be found at: (1930 articles) Signal Transduction (2497 articles) Hemostasis, Thrombosis, and Vascular Biology (790 articles) Cell Adhesion and Motility

The anterior cruciate ligament (ACL) can be anatomically divided into anteromedial (AM) and posterolateral (PL) bundles. Current ACL reconstruction techniques focus primarily on reproducing the AM bundle, but are insufficient in response to rotatory loads. The objective of this study was to determine the distribution of in situ force between the two bundles when the knee is subjected to anterior tibial and rotatory loads. Ten cadaveric knees (50 k 10 years) were tested using a roboticluniversal forcemoment sensor (UFS) testing system. Two external loading conditions were applied: a 134 N anterior tibial load at full knee extension and 15", 30°, 60", and 90" of flexion and a combined rotatory load of 10 N m valgus and 5 N m internal tibial torque at 15" and 30" of flexion. The resulting 6 degrees of freedom kinematics of the knee and the in situ forces in the ACL and its two bundles were determined. Under an anterior tibial load, the in situ force in the PL bundle was the highest at full extension (67 k 30 N) and decreased with increasing flexion. The in situ force in the AM bundle was lower than in the PL bundle at full extension, but increased with increasing flexion, reaching a maximum (90 f 17 N) at 60" of flexion and then decreasing at 90". Under a combined rotatory load, the in situ force of the PL bundle was higher at 15" (21 k 11 N) and lower at 30" of flexion (14 f 6 N). The in situ force in the AM bundle was similar at 15" and 30" of knee flexion (30k 15 vs. 3 5 2 16 N, respectively). Comparing these two external loading conditions demonstrated the importance of the PL bundle, especially when the knee is near full extension. These findings provide a better understanding of the function of the two bundles of the ACL and could serve as a basis for future considerations of surgical reconstruction in the replacement of the ACL.

Despite the success in clinical application, the exact mechanism of shock wave therapy remains unknown. We hypothesized that shock wave therapy induces the ingrowth of neovascularization and improves blood supply to the tissues. The purpose of this study was to investigate the effect of shock wave therapy on neovascularization at the tendon-bone junction. Fifty New Zealand white rabbits with body weight ranging from 2.5 to 3.5 kg were used in this study. The right limb (the study side) received shock wave therapy to the Achilles tendon near the insertion to bone. The left limb (the control side) received no shock wave therapy. Biopsies of the tendon-bone junction were performed in 0, 1,4, 8 and 12 weeks. The number of neo-vessels was examined microscopically with heniatoxylin-eosin stain. Neovascularization was confirmed by the angiogenic markers including vessel endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) expressions and endothelial cell proliferation determined by proliferating cell nuclear antigen (PCNA) expression examined microscopically with immunohistochemical stains. The results showed that shock wave therapy produced a significantly higher number of neo-vessels and angiogenesis-related markers including eNOS, VEGF and PCNA than the control without shock wave treatment. The eNOS and VEGF began to rise in as early as one week and remained high for 8 weeks, then declined at 12 weeks; whereas the increases of PCNA and neo-vessels began at 4 weeks and persisted for 12 weeks. In conclusion, shock wave therapy induces the ingrowth of neovascularization associated with early release of angiogenesisrelated markers at the Achilles tendon-bone junction in rabbits. The neovascularization may play a role to improve blood supply and tissue regeneration at the tendon-bone junction.

Blood platelets become activated and aggregate at the site of vessel injury. Upon activation by thrombin, platelets release storage pools of proteins and growth factors (GFs), including those involved in tissue repair. Our goal was to evaluate the potential beneficial effect of proteins released from platelet-rich clots on tendon healing. PDGF, TGF-P-I, IGF-I, HGF, VEGF and EGF were measured in human platelet-poor plasma (PPP) and in the releasates collected from either platelet-poor or platelet-rich clots prepared in vitro. We then studied the effects of the releasates on human tendon cells in culture. Releasates from both platelet-rich and platelet-poor clots stimulated tendon cell proliferation, in contrast to un-clotted PPP. The mitogenic activity of the supernatants was not decreased by the thrombin inhibitor, hirudin. Cultured tendon cells synthesise VEGF and HGF in the presence of PPP-clots and PRP-clot releasates, thus the synthesised amount was significantly higher with supernatants from platelet-rich clots than supernatants from a platelet-poor clot zyxwvutsr @ < 0.05). These results suggest that administering autologous platelet-rich clots may be beneficial to the treatment of tendon injuries by inducing cell proliferation and promoting the synthesis of angiogenic factors during the healing process. zyxwvutsr

The flow-independent (intrinsic) tensile modulus of the extracellular matrix of human knee joint cartilage has been measured for normal, fibrillated, and osteoarthritic (removed from total knee joint replacements) cartilage. The modulus was determined in our isometric tensile apparatus and measured at equilibrium. We found a linear equilibrium stress-strain behavior up to ∼15% strain. The modulus was measured for tissues from the high and low weight-bearing areas of the joint surfaces, the medial femoral condyle and lateral patello femoral groove, and from different zones (surface, subsurface, middle, and middle-deep) within the tissue. For all specimens, the intrinsic tensile modulus was always less than 30 MPa. Tissues from low weight-bearing areas (LWA) are stiffer than those from high weight-bearing areas (HWA). The tensile modulus of the ECM correlates strongly with the collagen/proteoglycan ratio; it is higher for LWA than for HWA. Osteoarthritic cartilage from total knee replacement procedures has a tensile stiffness less than 2 MPa.

Impairment of the human neuromusculoskeletal system can lead to significant mobility limitations and decreased quality of life. Computational models that accurately represent the musculoskeletal systems of individual patients could be used to explore different treatment options and optimize clinical outcome. The most significant barrier to model-based treatment design is validation of model-based estimates of in vivo contact and muscle forces. This paper introduces an annual ''Grand Challenge Competition to Predict In Vivo Knee Loads'' based on a series of comprehensive publicly available in vivo data sets for evaluating musculoskeletal model predictions of contact and muscle forces in the knee. The data sets come from patients implanted with force-measuring tibial prostheses. Following a historical review of musculoskeletal modeling methods used for estimating knee muscle and contact forces, we describe the first two data sets used for the first two competitions and summarize four subsequent data sets to be used for future competitions. These data sets include tibial contact force, video motion, ground reaction, muscle EMG, muscle strength, static and dynamic imaging, and implant geometry data. Competition participants create musculoskeletal models to predict tibial contact forces without having access to the corresponding in vivo measurements. These blinded predictions provide an unbiased evaluation of the capabilities and limitations of musculoskeletal modeling methods. The paper concludes with a discussion of how these unique data sets can be used by the musculoskeletal modeling research community to improve the estimation of in vivo muscle and contact forces and ultimately to help make musculoskeletal models clinically useful. ß

Objective: To propose a technique for evaluation of pulmonary lesions using contrast-enhanced MRI; to assess morphological patterns of enhancement and correlate quantitative analysis with histopathology. Material and methods: Thirty-six patients were prospectively studied. Volumetric-interpolated T1W images were obtained during consecutive breath holds after bolus triggered contrast injection. Volume coverage of first three acquisitions was limited (higher temporal resolution) and last acquisition obtained at 4th min. Two radiologists individually evaluated the patterns of enhancement. Region-ofinterest-based signal intensity (SI)-time curves were created to assess quantitative parameters. Results: Readers agreed moderately to substantially concerning lesions' enhancement pattern. SI-time curves could be created for all lesions. In comparison to benign, malignant lesions showed higher values of maximum enhancement, early peak, slope and 4th min enhancement. Early peak >15% showed 100% sensitivity to detect malignancy, maximum enhancement >40% showed 100% specificity. Conclusions: The proposed technique is robust, simple to perform and can be applied in clinical scenario. It allows visual evaluation of enhancement pattern/progression together with creation of SI-time curves and assessment of derived quantitative parameters. Perfusion analysis was highly sensitive to detect malignancy, in accordance to what is recommended by most recent guidelines on imaging evaluation of pulmonary lesions.

Articular cartilage in adults has limited ability for self-repair. Some methods devised to augment the natural healing response stimulate some regeneration, but the repair is often incomplete and lacks durability. Hyaluronan-based polymers were tested for their ability to enhance the natural healing response. It is hypothesized that hyaluronan-based polymers recreate an embryonic-like milieu where host progenitor cells can rcgcncrate the damaged articular surface and underlying bone. Oskochondral dcfccts were made on the femoral condyles of 4-month-old rabbits and were left empty or filled with hyaluronan-based polymers. The polymers tested were ACP sponge. made of crosslinked hyaluronan, and HYAFF-11 sponge, made of benxylated hyaluronan. The rabbits were killed 4 and 12 weeks after surgery, and the condyles were processed for histology. All 12-week defects were scored with a 29-point scale, and the scores were compared with a Kruskall-Wallis analysis of variance on ranks. Untreated defects filled with bone tissue up to or beyond the tidemark, and the noncalcified surface layer varied from fibrous to hyaline-like tissue. Four weeks aftcr surgery, defects treated with ACP exhibited bone filling to the level of the tidemark and the surface layer was composed of hyaline-like cartilage well integrated with the adjacent cartilage. At 12 weeks, the specimens had bone beyond the tidemark that was covered with a thin layer of hyaline cartilage. Four weeks after surgery, defects treated with HYAFF-11 contained a rim of chondrogcnic cells at the interface of the implant and the host tissue. In general, the 12-week dcfccts exhibited good bone fill and the surface was mainly hyaline cartilage. Treated defects received significantly higher scores than untreated defects (p < 0.05), and ACP-trcatcd defects scored significantly higher than HYAFF-11-treated defects (p < 0.05). The introduction of these hyaluronan-based polymers into delects provides an appropriate scaffolding and favorable microenvironnient for the reparative process. Further work is required to lully assess thc long-term outcome of defects treated with these polymers.

Collagen gels were seeded with rabbit bone marrow-derived mesenchymal stem cells (MSCs) and contracted onto sutures at initial cell densities of I , 4, and 8 million cellslml. These MSC-collagen composites were then implanted into full thickness, full length, central defects created in the patellar tendons of the animals providing the cells. These autologous repairs were compared to natural repair of identical defects on the contralateral side. Biomechanical, histological, and morphometric analyses were performed on both repair tissue types at 6, 12, and 26 weeks after surgery. Repair tissues containing the MSC-collagen composites showed significantly higher maximum stresses and moduli than natural repair tissues at 12 and 26 weeks postsurgery. However, no significant differences were observed in any dimensional or mechanical properties of the repair tissues across seeding densities at each evaluation time. By 26 weeks, the repairs grafted with MSC-collagen composites were one-fourth of the maximum stress of the normal central portion of the patellar tendon with bone ends. The modulus and maximum stress of the repair tissues grafted with MSCLcollagen composites increased at significantly faster rates than did natural repairs over time. Unexpectedly, 28% of the MSC ~ collagen grafted tendons formed bone in the regenerating repair site. Except for increased repair tissue volume, no significant differences in cellular organization or histological appearance were observed between the natural repairs and MSC-collagen grafted repairs. Overall, these results show that surgically implanting tissue engineered MSC-collagen composites significantly improves the biomechanical properties of tendon repair tissues, although greater MSC concentrations produced no additional significant histological or biomechanical improvement.

The tendon to bone insertion site is a complex transitional region that links two very different materials. The insertion site must transfer a complex loading environment effectively to prevent injury and provide proper joint function. In order to accomplish this load transfer effectively, the properties of the insertion site were hypothesized to vary along its length. The quasilinear viscoelastic (QLV) Model was used to determine biomechanical properties, polarized light analysis was used to quantitate collagen orientation (structure), and in situ hybridization was used to determine the expression of extracellular matrix genes (composition). All assays were performed at two insertion site locations: the tendon end of the insertion and the bony end of the insertion. Biomechanically, the apparent properties of peak strain, the coefficients (A and B ) that describe the elastic component of the QLV model, and one of the coefficients ( 7 , ) of the viscous component of the model were significantly higher, while another of the coefficients ( C ) of the viscous component was significantly lower at the tendon insertion compared to the bony insertion. The collagen was significantly more oriented at the tendon insertion compared to the bony insertion. Finally, collagen types 11, IX, and X, and aggrecan were localized only to the bony insertion, while decorin and biglycan were localized only to the tendon insertion. Thus, the tendon to bony insertion site varies dramatically along its length in terms of its viscoelastic properties, collagen structure, and extracellular matrix composition.

Over the past 8 years, our group has been continuously improving tendon repair using a functional tissue engineering (FTE) paradigm. This paradigm was motivated by inconsistent clinical results after tendon repair and reconstruction, and the modest biomechanical improvements we observed after repair of rabbit central patellar tendon defects using mesenchymal stem cell-gelsuture constructs. Although possessing a significantly higher stiffness and failure force than for natural healing, these first generation constructs were quite weak compared to normal tendon. Fundamental to the new FTE paradigm was the need to determine in vivo forces to which the repair tissue might be exposed. We first recorded these force patterns in two normal tendon models and then compared these peak forces to those for repairs of central defects in the rabbit patellar tendon model (PT). Replacing the suture with end-posts in culture and lowering the mesenchymal stem cell (MSC) concentration of these constructs resulted in failure forces greater than peak in vivo forces that were measured for all the studied activities. Augmenting the gel with a type I collagen sponge further increased repair stiffness and maximum force, and resulted in the repair tangent stiffness matching normal stiffness up to peak in vivo forces. Mechanically stimulating these constructs in bioreactors further enhanced repair biomechanics compared to normal. We are now optimizing components of the mechanical signal that is delivered in culture to further improve construct and repair outcome. Our contributions in the area of tendon functional tissue engineering have the potential to create functional load-bearing repairs that will revolutionize surgical reconstruction after tendon and ligament injury. ß

Puvpos~: We have isolated pluripotent mesenchymal progenitor cells in large numbers from liposuction aspirates (processed lipoaspirate cells or PLAs). This study examines the osteogenic potential of PLAs and bone marrow aspirate cells (BMAs), when exposed to either recombinant human bone morphogenetic protein (BMPI-2 (rh-BMP-2) or adenovirus containing BMP-2 cDNA Mrthoulc: Liposuction aspirates underwent proteolytic digestion to obtain PLAs. After exposure to exogenous rh-BMP-2 or Ad-BMP-2 for four or seven days, PLAs and BMAs were assessed by histochemistry, spectrophotometry and RT-PCR. Western blotting and ELISA confirmed BMP gene transduction. Results were compared to osteoblasts and cells in osteogenic media only. PLA-Ad-BMP-2 cells were seeded on matrices and implanted in the hind limbs of SCID mice.

Ischemia predisposes orthopaedic trauma patients to delayed fracture healing or non-union. The goal of this study was to test the ability of bone morphogenetic protein 7 (BMP7) to stimulate fracture repair in an ischemic environment. Ischemic fractures were generated in male adult mice by resecting the femoral artery prior to the creation of a non-stabilized tibia fracture. Recombinant human BMP7 (rhBMP7, 50µg) was injected into the fracture site immediately after surgery. Histomorphometric analyses revealed that rhBMP7 induced more cartilage at day 7, more callus and bone at days 14 and 28, and more adipose tissue and fibrous tissue at days 7, 14 and 28 compared to controls (n=5/group/time). At day 28, all fractures treated with rhBMP7 (50µg, n=5) healed, whereas only 3 of 5 control fractures exhibited slight bony bridging. In addition, we found that rhBMP7 (both 10 and 50µg) significantly increased the amount of cartilage compared to controls in stabilized fractures, confirming its chondrogenic effect. No significant effects of rhBMP7 on tissue vascularization were observed at 3 days after fracture. Lastly, using bone marrow transplantation we determined that no donor-derived osteocytes or chondrocytes were present in rhBMP7 treated fractures, suggesting rhBMP7 did not recruit mesenchymal stem cells from the bone marrow to the fracture site. In conclusion, our results indicate that rhBMP7 is a promising treatment for fractures with severely disrupted blood supply.

Surgical intervention of the knee joint routinely endeavors to recreate a physiologically normal joint loading environment. The loading conditions resulting from osteotomies, fracture treatment, ligament replacements, and arthroplasties of the knee are considered to have an impact on the long term clinical outcome; however, knowledge regarding in vivo loading conditions is limited. Using a previously validated musculoskeletal lower limb model, we predicted the tibio-femoral joint contact forces that occur in the human knee during the common daily activities of walking and stair climbing. The average resultant peak force during walking was 3.1 times body weight (BW) across four total hip arthroplasty patients. Inter-individual variations proved larger than the variation of forces for each patient repeating the same task. Forces through the knee were considerably larger during stair climbing than during walking: the average resultant peak force during stair climbing was 5.4 BW although peaks of up to 6.2 BW were calculated for one particular patient. Average anteroposterior peak shear components of 0.6 BW were determined during walking and 1.3 BW during stair climbing. These results confirm both the joint contact forces reported in the literature and the importance of muscular activity in creating high forces across the joint. The magnitudes of these forces, specifically in shear, have implications for all forms of surgical intervention in the knee. The data demonstrate that high contact and shear forces are generated during weight bearing combined with knee flexion angles greater than approximately 15 degrees. Clinically, the conditions that produce these larger contact forces should be avoided during post-operative rehabilitation.

Femoroacetabular impingement secondary to the cam effect is thought to be associated with an insufficient anterior concavity in the sagittallaxial plane of the femoral head-neck junction. Using three-dimensional computed tomography the anterior and posterior concavity of the femoral head-neck junction was assessed in 36 painful non-dysplastic hips (30 patients). The mean age of the symptomatic hips was 40.7 with 13 females and 17 males. Eighteen out of the 36 hips had a pistol grip deformity. Magnetic resonance gadolinium arthrography was performed to assess for labral and cartilage lesions. Alpha and beta angles measuring the anterior and posterior femoral head-neck junction concavities were also determined in 20 asymptomatic hips (12 patients; mean age 37, 5 females and 7 males) using three-dimensional computed tomography. The mean alpha angle for the symptomatic and the control group were: 66.4 versus 43.8 0, = 0.001), and for the beta angle 40.2 versus 43.8 0, = 0.01 l), respectively. All but one of the symptomatic hips had a labral tear with 61% of these hips having associated cartilage damage. Three-dimensional computed tomography represents an accurate tool to quantify the femoral head-neck concavity providing a non-invasive assessment of hips at risk of femoroacetabular impingement.

OBJECTIVE: To determine if females presenting with patellofemoral pain syndrome (PFPS) from no discernable cause other than overuse demonstrate hip weakness and increased hip internal rotation, hip adduction, and knee valgus during stair descent. BACKGROUND: Historically, PFPS has been viewed exclusively as a knee problem. Recent findings have indicated a possible association between hip weakness and PFPS. Researchers have hypothesized that patients who demonstrate hip weakness would exhibit increased hip internal rotation, hip adduction, and knee valgus during functional activities. To date, researchers have not simultaneously examined hip and knee strength and kinematics in subjects with PFPS to make this determination. METHODS AND MEASURES: Eighteen females diagnosed with PFPS and 18 matched controls participated. Strength measures were taken for the hip external rotators and hip abduc-tors. Hip and knee kinematics were collected as subjects completed a standardized stair-stepping task. Independent t tests were used to determine between-group differences in strength and kinematics during stair descent. RESULTS: Subjects with PFPS generated 24% less hip external rotator (P = .002) and 26% less hip abductor (P =. 006) torque. No between-group differences (P .05) were found for average hip and knee transverse and frontal plane angles during stair descent. CONCLUSION: Subjects with PFPS had significant hip weakness but did not demonstrate altered hip and knee kinematics as previously theorized. Additional investigations are needed to better understand the association between hip weakness and PFPS etiology.

Cartilage was obtained from eight matched knee (tibiofemoral and femoropatellar) and ankle (talocrural) joints of five different donors (both left and right from donors 14, 22, and 38 years of age, and left only from donors 31 and 45 years of age) within 24 hours of death. All cartilage was graded as normal by the macroscopic visual Collins' scale and the histological Mankin scale. Cylindrical disks of cartilage were harvested from 10 sites within the tibiofemoral and femoropatellar joint surfaces and four sites within the talocrural joint. and uniaxial confincd compression measurements were performed to quantify a spectrum of physical properties including the equilibrium modulus, hydraulic permeability, dynamic stiffness, streaming potential, electrokinetic coupling coefficient, and electrical conductivity. Matched specimens from the same 14 sites were used for complementary measurements of biochemical composition and molecular interaction, including water content, hypotonic swelling behavior, and sulfated glycosaminoglycan and collagen contents. In comparison of the top 1-mm slices of talar cartilage with the top 1-mm of tibiofemoral cartilage. the talar cartilage appeared denser with a higher sulfated glycosaminoglycan content, lower water content. higher equilibrium modulus and dynamic stiffness, and lower hydraulic pcrmcability. The equilibrium modulus increased with increasing sulfated glycosaininoglycans per wct wcight and decreased with increasing water content for all joint surfaces. Multiple linear regression showcd that greater than 80% of the variation in the equilibrium modulus could be accounted for by variations in the biochemical parameters (water content, sulfated glycosaminoglycansiwet weight, and hydroxyproline contentiwcl wcight) for each joint surface. Nonhomogeneous depth-dependent changes in the physical properties and biochemical composition of fullthickness distal femoral cartilage were consistent with previous reports. Since the comprcssive deformation of cartilage during cyclic loading is confined to the more superficial rcgions, the differences in properties of the upper regions of the talar compared with tibiofemoral or femoropatellar cartilage may be important in the eliology of osteoarthritis.

Advancements in nanobiotechnology are revolutionizing our capability to understand biological intricacies and resolve biological and medical problems by developing subtle biomimetic techniques. Nanocomposites and nanostructured materials are believed to play a pivotal role in orthopedic research since bone itself is a typical example of a nanocomposite. This article reviews current strategies using nanobiomaterials to improve current orthopedic materials and examines their applications in bone tissue engineering. Preliminary investigations support the potential of nanobiomaterials in orthopedic applications; however, significant advancements are necessary to achieve clinical use. Overall, current trends in nanobiotechnology foreshadow a bright future through the use of nanobiomaterials in the orthopedic domain. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:11–22, 2007

Urist made the key discovery that demineralized bone fragments implanted either subcutaneously or intramuscularly in animals induce bone formation (100, 101). The hunt for the factors responsible for this effect has resulted in the identification of a family of bone morphogenetic proteins (BMPs) (115). BMPs play a crucial role in cell growth and differentiation in a variety of cell types including osteoblasts (49.83,84). BMPs trigger cellular effects by way of heterotetrameric serine/threonine kinase receptors and intracellular signaling proteins known as Smads (31,62). Evidence suggests BMPs and their receptors are required to promote bone regeneration following fracture (91). Shortly after a bone is fractured, BMP is released from cells at the injury site (4). Difficulties wilh bone regeneration may be linked to abnormal or insufficient endogenous BMPs, their receptors, and other recognized clinical etiologies (91,115). An overwhelming num bcr of preclinical studies have validated the ability of recombinant human BMPs (rhBMPs) to regenerate bone (18,20,22,63,121). Therefore, because BMPs will likely become conunonplace therapeutic agents for surgeons, it is timely to survey some of the recent exciting findings about the proteins, their receptors, signal transducers, and preclinical applications, as well as BMP-responsive genes. Moreover, by clearly defining current BMP biology, scientists and clinicians may collectively pursue the answers to questions that will benefit patients. Update: Review and Discussion of Current Knowledge Classification and Characterization BMPs are members of the transforming growth factor-~ (TGF-~) superfamily. Major subdivisions within the superfamily include the TGF-~s, BMPs (ex

Bilateral closed femoral shaft fractures were made in 22 male Long-Evans rats. In 16 animals, ultrasound was applied to one limb for 15 minutes daily 10 times within the first 14 postoperative days. The treated limbs received a 200 psec burst of 1.5 or 0.5 MHz sine waves repeated at 1.0 kHz at a spatial average and temporal average intensity of 30 mW/cm2. The contralateral limb of each animal served as a nontreated control. Six remaining animals with fractures and six additional animals without fractures received sham ultrasound treatment to control for the effects of anesthesia and handling. Fracture repair was evaluated on postoperative day 21 by radiography, mechanical testing in torsion, and histology. Five of 16 ultrasound-treated fractures showed obliteration of the fracture gap on radiographs, whereas none of the 28 controls did. The average maximum torque of fractures treated with either signal was 22% greater than that of the contralateral controls (p < 0.05). The stiffness of treated fractures was greater than that of control fractures, but the difference was significant only in animals treated with the 1.5 MHz signal (p < 0.02). Sham treatment did not affect repair in the control group. These results indicate that low-intensity pulsed ultrasound at either 0.5 or 1.5 MHz can accelerate fracture repair at 21 days in this highly controlled model.

Acetabular retroversion has been proposed to contribute to the development of osteoarthritis of the hip. For the diagnosis of this condition, conventional AP pelvic radiographs may represent a reliable, easily available diagnostic modality as they can be obtained with a reproducible technique allowing the anterior and posterior acetabular rims to be visible for assessment. This study was designed to: (i) determine cranial, central, and caudal anatomic acetabular version (AV) from cadaveric specimens; (ii) establish the validity and reliability of the radiographic measurements of central acetabular anteversion; and (iii) determine the validity and reliability of the radiographic “cross-over-sign” to detect acetabular retroversion. Using 43 desiccated pelvises (86 acetabuli) the anatomic AVs were measured at three different transverse planes (cranially, centrally, and caudally). From these pelvises, standardized AP pelvic radiographs were obtained. To directly measure central AV, a modified radiographic method is introduced for the use of AP pelvic radiographs. The validity and reliability of this radiographic method and of the radiographic cross-over-sign to detect cranial acetabular retroversion were determined. The mean central and caudal anatomic AVs were approximately 20°, and the mean cranial AV was 8°. Cranial retroversion (AV < 0°) was present in 19 of 86 hips (22%). A linear correlation was found between the central and cranial AV. Below 10° of central AV, all acetabuli were cranially retroverted. Between 10° and 20°, 30% of the acetabuli were cranially retroverted, and above 20°, only 1 of 45 acetabuli was cranially retroverted. The radiographic measurement of the central AV (20.3 ± 6.5°) correlated strongly with the anatomic AV (20.1 ± 6.4°). The sensitivity of the cross-over-sign to detect a cranial acetabular anteversion of less than 4° was 96%, its specificity 95%, and the positive predictive and negative predictive values 90% and 98%, respectively. Both the modified radiographic anteversion measurements and the cross-over-sign demonstrated substantial inter- and intraobserver reliability. Retroversion is almost exclusively a problem of the cranial acetabulum. The cranial AV is on average 12° lower than the central AV, with the latter directly measurable from AP pelvic radiographs. A central AV of less than 10° was associated with cranial retroversion. The presence of a positive cross-over-sign is a highly reliable indicator of cranial AV of <4°. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25: 758–765, 2007

The hypothesis of this study was that collagen denaturation would lead to a significant decrease in the toughness of bone, but has little effect on the stiffness of bone. Using a heating model, effects of collagen denaturation on the biomechanical properties of human cadaveric bone were examined. Prior to testing, bone specimens were heat treated at varied temperatures (37-200°C) to induce different degrees of collagen denaturation. Collagen denaturation and mechanical properties of bone were determined using a selective digestion technique and three-point bending tests, respectively. The densities and weight fractions of the mineral and organic phases in bone also were determined. A repeated measures analysis of variance showed that heating had a significant effect on the biomechanical integrity of bone, corresponding to the degree of collagen denaturation. The results of this study indicate that the toughness and strength of bone decreases significantly with increasing collagen denaturation, whereas the elastic modulus of bone is almost constant irrespective of collagen denaturation. These results suggest that the collagen network plays an important role in the toughness of bone, but has little effect on the stiffness of bone. thereby supporting the hypothesis of this study.

Diabetes mellitus is a common systemic disease that has been associated with poor fracture healing outcomes. The mechanism through which diabetes impairs bone regeneration is unknown. One possible mechanism may be related to either decreased or uncoordinated release of local growth factors at the fracture site. Indeed, previous studies have found reduced platelet-derived growth factor (PDGF) levels in the fracture callus of diabetic rats, suggesting that local application of PDGF may overcome the negative effects of diabetes and promote fracture healing. To test this hypothesis, low (22 mg) and high (75 ug) doses of recombinant human PDGF-BB (rhPDGF-BB) were applied directly to femur fracture sites in BB Wistar diabetic rats that were then compared to untreated or vehicle-treated animals. rhPDGF-BB treatment significantly increased early callus cell proliferation compared to that in control specimens. Low dose rhPDGF-BB treatment significantly increased callus peak torque values (p < 0.05) at 8 weeks after fracture as compared to controls. High dose rhPDGF-BB treatment increased callus bone area at 12 weeks postfracture. These data indicate that rhPDGF-BB treatment ameliorates the effects of diabetes on fracture healing by promoting early cellular proliferation that ultimately leads to more bone formation. Local application of rhPDGF-BB may be a new therapeutic approach to treat diabetes-impaired fracture healing. ß

Overuse injuries and trauma in tendon often involve acute or chronic pain and eventual matrix destruction. Anti-inflammatory drugs have been used as a treatment, however, the cellular and molecular mechanisms of the destructive processes in tendon are not clearly ...

The anterior cruciate ligament (ACL) fails to heal after suture repair. One hypothesis for this failure is the premature loss of the fibrin clot, or provisional scaffolding, between the two ligament ends in the joint environment. To test this hypothesis, a substitute provisional scaffold of collagen–platelet rich plasma (PRP) hydrogel was used to fill the ACL wound site at the time of suture repair and the structural properties of the healing ACLs evaluated 4 weeks after surgery. Bilateral ACL transections were performed in five 30-kg Yorkshire pigs and treated with suture repair. In each animal, one of the repairs was augmented with placement of a collagen–PRP hydrogel at the ACL transection site, while the contralateral knee had suture repair alone. In addition, six control knees with intact ACLs from three additional animals were used as a control group. No postoperative immobilization was used. After 4 weeks the animals underwent in vivo magnetic resonance imaging to assess the size of the healing ACL, followed by biomechanical testing to determine tensile properties. The supplementation of suture repair with a collagen–PRP hydrogel resulted in significant improvements in load at yield, maximum load, and linear stiffness at 4 weeks. We conclude that use of a stabilized provisional scaffold, such as a collagen–PRP hydrogel, to supplement primary repair of the ACL can result in improved biomechanical properties at an early time point. Further studies to determine the long-term effect of primary repair enhancement are needed. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:81–91, 2007

Osteoblast-like cells have been shown to be sensitive to the proliferative action of a wide variety of growth factors. Many of these growth factors have been isolated from platelets and are thought to be released at local sites in response to injury. In this study, we tested whether human platelet concentrate, as a supplement to basic medium, would support the proliferative and functional activity of human fetal osteoblast-like cells in both short-term and long-term culture. In short-term studies, uptake of [3H]thymidine was increased in platelet-treated cultures by more than 4-fold compared with 10% serum-supplemented controls. When cultured for prolonged periods on coverslips, the cells formed multilayers, with a collagen-based matrix separating the layers. Long-term cultures that were treated with 1.5% (vol/vol) platelets in serum-supplemented medium showed increases in the depth of the multilayers of as much as 36-fold at 30 days after confluence, compared with the 10% serum-supplemented controls; this difference persisted until day 50. Incorporation of growth factor in the matrix was examined with the use of colloidal gold immunoelectron microscopy. Immunogold labeling intensities for transforming growth factor-β1 were significantly lower in the platelet-treated cultures at 20 days and then increased to a maximum level of 2.1-fold more than in the controls at 40 days. Labeling intensities for insulin-like growth factor-I and basic fibroblast growth factor were significantly lower in the platelet-treated cultures than in the controls at all stages of culture. These results indicate that platelet-supplemented medium stimulates proliferation and maintains the differentiated function of human osteoblast-like cells. Platelets may play an important role in early healing of fractures and also may be useful as a cheap autologous source of multiple growth factors to enhance osteoblast proliferation in vivo and in vitro.

For the histopathological classification of the severity of osteoarthritic lesions of cartilage, the Mankin score is frequently used. A necessary constraint on the validity of this scoring system is the consistency with which cartilage lesions are classified. The intra-and interobserver agreement of the Mankin score was determined. The intra-and interobserver agreement of the 14-point Mankin score was adequate. Between observers 95% of differences were less than -7 points. By a more strict definition of the elements of the Mankin score, the intraobserver differences were reduced only for some observers. The interobserver differences were only slightly reduced: between observers 95% of differences were less than -6 points. We found the Mankin score to be an adequate histopathological tool.

Rotator cuff repair is known to have a high failure rate. Little is known about the natural healing process of the rotator cuff repair site, hence little can be done to improve the tendon's ability to heal. The purpose of this study was to investigate the collagen formation at the early repair site and to localize TGFb-1 and 3 during early healing and compare their levels to cell proliferation and histological changes. Bilateral supraspinatus tendons were transected and repaired in 60 rats. Specimens were harvested and evaluated at 0, 1, 3, 7, 10, 28, and 56 days. Histological sections were evaluated for cell morphology. Immunohistochemistry and in situ hybridization was performed to localize protein and mRNA for collagen types I and III and TGFb-1 and 3. Proliferating cell nuclear antigen (PCNA) assay was performed to measure cell proliferation, and cells were counted to determine cell density. Biomechanical properties were evaluated. Repair tissue demonstrated an initial inflammatory response with multinucleated cells present at 1 and 3 days, and lymphocytes and plasma cells presents at 7 and 10 days. Capillary proliferation began at 3 days and peaked at 10 days. Ultimate force increased significantly over the time period studied. Collagen I protein and mRNA significantly increased at 10 days, and reached a plateau by 28 and 56 days. Collagen III showed a similar trend, with an early increase, and remained high until 56 days. TGFb-1 was localized to the forming scar tissue and showed a distinct peak at 10 days. TGFb-3 was not seen at the healing insertion site. Cell proliferation and density followed the same trend as TGFb-1. A wound healing response does occur at the healing rotator cuff insertion site, however, the characteristics of the tendon after healing differ significantly from the uninjured tendon insertion site at the longest time-point studied. A distinctive collagen remodeling process occurred with an initial increase in the formation of collagen types I and III followed by a decrease toward baseline levels seen at time 0. Growth factor TGFb-1 was localized to repair tissue and coincided with a peak in cell proliferation and cellularity. Repair sites remained unorganized histologically and biomechanically inferior in comparison to previously described uninjured insertion sites. ß

The aim of this study was to investigate the involvement of apoptosis (programmed cell death) in the pathogenesis of rotator cuff 8 disorders. The edges of torn supraspinatus rotator cuff tendons were collected from patients with rotator cuff tear (n ¼ 25). Samples 9 of the intra-articular portion of subscapularis tendons were collected from patients without rotator cuff tear as control (n ¼ 6). To 10 minimize individual variance, we also collected six pairs of supraspinatus tendon and subscapularis tendon from six patients with 11 rotator cuff tears. Apoptosis was detected by in situ DNA end labelling assay and DNA laddering assay. Immunohistochemical 12 staining was performed to identify cells undergoing apoptosis. Control subscapularis tendon had normal morphology. Tendon from 13 torn supraspinatus rotator cuff showed significant mucoid degeneration. Within the areas of degeneration, there were large numbers 14 of apoptotic cells. The percentage of apoptotic cells in the degenerative rotator cuff (34%) was significantly higher than that in 15 controls (13%) (p < 0:001). The excessive apoptosis detected in degenerative rotator cuff tissue was confirmed by DNA laddering 16 assays. This is the first report of excessive apoptosis in degenerating rotator cuff tendon. Cells undergoing apoptosis in rotator cuff 17 were mainly fibroblast-like cells. These finding indicate that apoptosis may play an important role in the pathogenesis of rotator cuff 18 degeneration. Ó

One approach to repairing articular defects is to regenerate cartilage by recapitulating the changes that occur during fetal and postnatal growth into adulthood, and to thereby restore functional biomechanical properties, especially those of the normally strong superficial region. The objectives of this study were ( I ) to characterize and compare tensile biomechanical properties of the superficial region of articular cartilage of the patellofemoral groove (PFG) and femoral condyle (FC) from bovine animals over a range of growth stages (third-trimester fetal, 1-3 week-old calf, and adult), and (2) to determine if these properties were correlated with collagen network components. With growth from the fetus to the adult, the equilibrium and dynamic tensile moduli and strength of cartilage samples increased by an average of 391-1060%, while the strain at the failure decreased by 43%. The collagen concentration (per wet weight) increased by 98'%), and the pyridinoline cross-link concentration increased by 730%, while the glycosaminoglycan concentration remained unchanged or decreased slightly. Some growth-associated changes were location-specific, with tensile moduli and strength attaining higher values in the PFG than the FC. The growth-associated variation in tensile moduli and strength were associated strongly with variation in the contents of collagen and pyridinoline cross-link, but not sulfated glycosaminoglycan. The marked changes in the tensile properties and collagen network components of articular cartilage with growth suggest that such parameters may be used to evaluate the degrees to which regenerated cartilage recapitulates normal development and growth.

Osteoarthritis (OA) is a disabling condition in which multiple initiating events or conditions (heritable and nonheritable) result in eventual loss of articular cartilage. However, the etiology of OA remains poorly understood, and diagnosis of early disease is difficult due to the lack of specific identifiers. Recent literature suggests that a series of inflammatory processes may be involved in initiating and propagating OA. We hypothesized that products of neutrophils and macrophages, namely myeloperoxidase (MPO), a specific enzyme responsible for the production of both highly reactive hypochlorous acid (HOCl) and chlorine gas (Cl 2 ) and chlorinated peptides, may be present in the synovial fluid of patients with OA. We examined the synovial fluid from 30 patients to identify and profile the presence of MPO. We divided the samples into three groups using radiographic and clinical assessment: (1) control, patients with acute knee injury with no history of OA and no radiographic evidence of OA; (2) early OA, patients with a mild OA based on radiographs; and (3) late OA, patients with a longstanding history of OA and with radiographic evidence of complete joint loss. Patients with early OA demonstrated significantly elevated levels of MPO. We also demonstrated the presence of HOCl and Cl 2 modified proteins (Cl-peptides) in early OA synovial fluid samples by liquid chromatography and mass spectrometry. Patients in the control and advanced OA groups demonstrated little elevation in MPO levels and Cl-peptides were undetectable. These results indicate that MPO and Cl-peptides may serve as diagnostic markers for the detection of early OA. ß

Tendinitis remains a catastrophic injury among athletes. Mesenchymal stem cells (MSCs) have recently been investigated for use in the treatment of tendinitis. Previous work has demonstrated the value of insulin-like growth factor-I (IGF-I) to stimulate cellular proliferation and tendon fiber deposition in the core lesion of tendinitis. This study examined the effects of MSCs, as well as IGF-I geneenhanced MSCs (AdIGF-MSCs) on tendon healing in vivo. Collagenase-induced bilateral tendinitis lesions were created in equine flexor digitorum superficialis tendons (SDFT). Tendons were treated with 10 Â 10 6 MSCs or 10 Â 10 6 AdIGF-MSCs. Control limbs were injected with 1 mL of phosphate-buffered saline (PBS). Ultrasound examinations were performed at t ¼ 0, 2, 4, 6, and 8 weeks. Horses were euthanized at 8 weeks and SDFTs were mechanically tested to failure and evaluated for biochemical composition and histologic characteristics. Expression of collagen types I and III, IGF-I, cartilage oligomeric matrix protein (COMP), matrix metalloproteinase-3 (MMP-3), matrix metalloproteinase-13 (MMP-13), and aggrecanase-1 (ADAMTS-4) were similar in MSC and control tendons. Both MSC and AdIGF-MSC injection resulted in significantly improved tendon histological scores. These findings indicate a benefit to the use of MSCs and AdIGF-MSCs for the treatment of tendinitis. ß

Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.

Extracorporeal shock waves (ESW) have recently been used in resolving tendinitis. However, mechanisms by which ESW promote tendon repair is not fully understood. In this study, we reported that an optimal ESW treatment promoted healing of Achilles tendintis by inducing TGF-b1 and IGF-I. Rats with the collagenease-induced Achilles tendinitis were given a single ESW treatment (0.16 mJ/mm 2 energy flux density) with 0, 200, 500 and 1000 impulses. Achilles tendons were subjected to biomechanical (load to failure and stiffness), biochemical properties (DNA, glycosaminoglycan and hydroxyproline content) and histological assessment. ESW with 200 impulses restored biomechanical and biochemical characteristics of healing tendons 12 weeks after treatment. However, ESW treatments with 500 and 1000 impulses elicited inhibitory effects on tendinitis repair. Histological observation demonstrated that ESW treatment resolved edema, swelling, and inflammatory cell infiltration in injured tendons. Lesion site underwent intensive tenocyte proliferation, neovascularization and progressive tendon tissue regeneration. Tenocytes at the hypertrophied cellular tissue and newly developed tendon tissue expressed strong proliferating cell nuclear antigen (PCNA) after ESW treatment, suggesting that physical ESW could increase the mitogenic responses of tendons. Moreover, the proliferation of tenocytes adjunct to hypertrophied cell aggregate and newly formed tendon tissue coincided with intensive TGF-b1 and IGF-I expression. Increasing TGF-b1 expression was noted in the early stage of tendon repair, and elevated IGF-I expression was persisted throughout the healing period. Together, low-energy shock wave effectively promoted tendon healing. TGF-b1 and IGF-I played important roles in mediating ESW-stimulated cell proliferation and tissue regeneration of tendon.