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Summary Objective In ovine hips chondrolabral damage as seen in cam-type femoroacetabular impingement (FAI) can be induced via an intertrochanteric varus osteotomy. However, it is yet to proven whether the observed cartilage damage is caused by a dynamic cam type impingement. Thus we asked, (1) whether actual cartilage damage observed after FAI induction in ovine hips occurs at the predicted, computed zone of FAI; (2) whether the extent of cartilage damage increases with ambulation time in this animal model? Design In this experimental, controlled, comparative study 20 sheep underwent unilateral FAI induction through an intertrochanteric varus osteotomy. Preoperatively sheep underwent computed tomography to generate three-dimensional models of the osseous pelvis and femur. The models were used to predict impingement zones before and after simulated varus osteotomy using range of motion (ROM) analysis. Sheep were sacrificed after 14–40 weeks of ambulation. At sacrifice cartilage was inspected and (1) location of actual damage and computed impingement zones were compared; (2) Cartilage damage was compared between short- and long ambulation groups. Results (1) The average location and the extent of peripheral and central cartilage lesions did not differ with the computed impingement zones (all P > 0.05). (2) Grades of central, posterior cartilage damage were more severe in the long-compared to the short ambulation group (2.2 ± 1.8 vs 0.4 ± 0.5; P = 0.030). Conclusions In this experimental ovine FAI model the surgical induction of an osseous impingement conflict between the femur and acetabulum causes cartilage damage at the zone of simulated FAI.

The experimental induction of cam-type femoroacetabular impingement (FAI) in sheep is established. To tap the full potential of this ovine model, one should be able to perform a femoral osteochondroplasty safely. This study was based on previous cadaver experiments on the blood supply to the ovine femoral head and on the biomechanical strength of the proximal femur following offset creation. We hypothesized that offset creation in this ovine FAI model does not lead to (1) avascular necrosis (AVN) of the ovine femoral head or (2) iatrogenic femoral neck fractures and (3) can be performed effectively.In this experimental, controlled, prospective study nine sheep underwent unilateral FAI induction through an intertrochanteric, varus osteotomy. Seventy days following FAI induction, femoral osteochondroplasty was performed. Sheep were sacrificed after another 140 days. Radiographs, computed tomography (CT) scans and MRI were acquired. Histologic samples were stained with hematoxylin-eosin. (1) The multimodal Association Research Circulation Osseous (ARCO) classification was used for assessment of AVN. (2) Femoral neck fractures were assessed with the multimodal imaging approach. (3) Pre- and postoperative (=after sacrifice) alpha angles and femoral neck diameters were compared.(1) No signs for AVN according to the ARCO classification or (2) for femoral neck fractures were detected. (3) Mean alpha angles and femoral neck diameters decreased significantly (p0.001) superiorly by at least 30° respectively 4 mm after the offset creation.Femoral osteochondroplasty can be performed effectively and without the risk of AVN or femoral neck fractures in this ovine FAI model.

Background & Aim Osteoarthritis (OA) is the most prevalent joint disorder causing pain and disability predominantly in the ageing population but also in young individuals. Current treatments are limited to alleviate symptoms, e.g. with anti-inflammatory drugs, until at the end stage of the disease the degenerated joint is replaced by a prosthetic implant. In this study we hypothesize that degenerative cartilage defects can be treated using Nasal chondrocyte-based Tissue Engineered Cartilage (N-TEC), as previously applied for the repair of focal articular cartilage lesions. In particular, we tested (i) the response of N-TECs to inflammatory factors, (ii) their capacity to modulate the inflammatory profile of OA joint cells in vitro as well as (iii) their survival in - and integration with OA tissues in vivo. Based on these results we then (iv) assessed the performance of N-TEC upon implantation in OA knee cartilage lesions of human patients. Methods, Results & Conclusion When N-TEC was exposed in vitro to inflammatory stimuli, as those found in OA joints (IL-1β/TNFα/IL-6 cytokines or factors secreted by OA synoviocytes) we demonstrate that it maintained its cartilaginous properties (i). Moreover, the secretome of N-TEC positively influenced the inflammatory profile of cells from OA joints, i.a. by reducing the expression of IL-6 and TNFα (ii). In vivo in an ectopic mouse model reproducing a human osteochondral OA tissue environment as well as in chronified articular cartilage defects in sheep, we further demonstrated cell survival and engraftment of N-TEC with the surrounding OA tissues (iii). Finally, we tested clinically the implantation of autologous N-TEC in two patients with advanced OA (Kellgren and Lawrence grade 3 and 4), who were otherwise considered for unicondylar knee arthroplasty. Patients reported reduced pain as well as improved joint function and life quality 14 months after surgery. In addition, a radiologically observed increase in joint space, indicating safety and feasibility of the treatment (iv). Together, our findings indicate that N-TEC can directly contribute to cartilage repair in OA joints. A phase II clinical trial is now required to assess efficacy in a larger cohort of OA patients.

© 2018 Acta Materialia Inc. Less than optimal particle isolation techniques have impeded analysis of orthopaedic wear debris in vivo. The purpose of this research was to develop and test an improved method for particle isolation from tissue. A volume of 0.018 mm 3 of clinically relevant CoCrMo, Ti-6Al-4V or Si 3 N 4 particles was injected into rat stifle joints for seven days of in vivo exposure. Following sacrifice, particles were located within tissues using histology. The particles were recovered by enzymatic digestion of periarticular tissue with papain and proteinase K, followed by ultracentrifugation using a sodium polytungstate density gradient. Particles were recovered from all samples, observed using SEM and the particle composition was verified using EDX, which demonstrated that all isolated particles were free from contamination. Particle size, aspect ratio and circularity were measured using image analysis software. There were no significant changes to the measured parameters of CoCrMo or Si 3 N 4 particles before and after the recovery process (KS tests, p > 0.05). Titanium particles were too few before and after isolation to analyse statistically, though size and morphologies were similar. Overall the method demonstrated a significant improvement to current particle isolation methods from tissue in terms of sensitivity and efficacy at removal of protein, and has the potential to be used for the isolation of ultra-low wearing total joint replacement materials from periprosthetic tissues. Statement of Significance: This research presents a novel method for the isolation of wear particles from tissue. Methodology outlined in this work would be a valuable resource for future researchers wishing to isolate particles from tissues, either as part of preclinical testing, or from explants from patients for diagnostic purposes. It is increasingly recognised that analysis of wear particles is critical to evaluating the safety of an orthopaedic device.

The hypoxaemic effects of intravenous alpha2-agonists in sheep are well documented. Based on preliminary trials we hypothesized that intramuscular (IM) administration of medetomidine and dexmedetomidine would lead to less severe side effects than IV administration. Nineteen healthy nonpregnant ewes of various breeds undergoing different orthopaedic procedures were studied. Pre-anaesthetic medication was 15 µg kg−1 dexmedetomidine IM [group A, n = 9] or 30 µg kg−1 medetomidine IM [group B, n = 10] 30 minutes prior to induction of anaesthesia with ketamine (2 mg kg−1) IV. Anaesthesia was maintained with isoflurane in 100% oxygen. End expired anaesthetic concentration (F eiso) and respiratory frequency (fR) were determined with a methane insensitive infrared gas analyser (Anaesthetic Gas Monitor Type 1304, Bruel & Kjaer, Naerum, Denmark). Direct mean arterial blood pressure (MAP) and a lead II ECG were monitored continuously. Arterial blood samples were taken 10 minutes after induction of anaesthesia and then at 30 minute intervals. Data were averaged over time and tested for differences between groups by independent t-tests or anova for repeated measures followed by Bonferroni corrected t-tests. The results are presented as mean ± SD. There were no significant (p

In this in-vivo study magnesium alloys with a rare earth composition metal (LAE442) on the one hand and cerium as single rare earth element (LACer442) on the other hand were compared. Extruded cylindrical identically machined implants of both alloys were implanted intramedullary in both tibiae of five New Zealand White rabbits each (group 1 – LAE442, group 2 – LACer442). Three months were planned as postoperative observation period with clinical and radiographical examinations. Postmortal, μ-computed tomographical and histological analyses of the tibiae were done. Although the alloys were very similar, profound differences could be found in biocompatibility. The LAE442-alloys were tolerated well. The μCT showed an even implant degradation as well as marginal new bone formation. Histologically, a good biocompatibility was seen. The rabbits with LACer442-implants had to be euthanized ahead of schedule because of massive implant intolerance due to gas formation and fast implant degradation which could be confirmed and differentiated in the radiographic, μ-computed tomographical and histological examinations. These results show that the single rare earth element cerium can not successfully substitute the rare earth composition metal in a magnesium alloy for biomedical use. In dieser in-vivo Studie wurde eine Magnesium-Legierung mit einem Seltenen-Erden-Mischmetall (LAE442) mit einer Magnesium-Legierung mit Cer als Einzelelement aus der Gruppe der Seltenen Erden (LACer442) verglichen. Identisch hergestellte stranggepresste, zylinderformige Implantate beider Legierungen wurden beidseits intramedullar in Tibiae von je funf New Zealand White Kaninchen implantiert (Gruppe 1 – LAE442, Gruppe 2 – LACer442). Der Untersuchungszeitraum sollte drei Monate betragen. Wahrend des Untersuchungszeitraumes wurden die Tiere klinisch und radiologisch untersucht. Postmortal erfolgte eine μ-computertomographische und histologische Beurteilung der Tibiae. Obwohl die Legierungen sehr ahnlich in ihrer Zusammensetzung waren, wurden fulminante Unterschiede in der Biokompatibilitat gefunden. Die LAE442-Legierung wurde sehr gut vertragen. Im μCT zeigte sich eine beginnende gleichmasige Degradation der Implantate sowie geringgradige Knochenneubildung. Die Histologie zeigte eine gute Biokompatibilitat. Die Kaninchen mit LACer442-Implantaten mussten vorzeitig euthanasiert werden da sie klinisch hochgradige Implantatunvertraglichkeiten bedingt durch Gasbildung und schnelle Implantatdegradation zeigten, welche in den radiologischen, μ-computertomographischen und histologischen Untersuchungen bestatigt wurden. Die Ergebnisse zeigen, dass das Einzelelement Cerium fur das Seltene-Erden-Mischmetall keinen adaquaten Ersatz bei der Verwendung von biodegradablen Magnesiumlegierungen darstellt.

Summary Reasons for performing the study: Similar to human decubitus ulcers, local high pressure points from ill-fitting saddles induce perfusion disturbances of different degrees resulting in tissue hypoxia and alteration in sweat production. Objective: To relate the different clinical manifestations of saddle sores to the magnitude of saddle pressures at the location of the withers. Methods: Sixteen horses with dry spots after exercise (Group A) and 7 cases presented with acute clinical signs of saddle pressure in the withers area (Group B) were compared with a control group of 16 sound horses with well fitting saddles (Group C). All horses underwent a saddle pressure measurement at walk, trot and canter. Mean and maximal pressures in the area of interest were compared between groups within each gait. Results: Mean pressures differed significantly between groups in all 3 gaits. Maximal pressure differed between groups at trot; at walk and canter, however, the only significant difference was between Group C and Groups A and B, respectively, (P>0.05). Mean and maximal pressures at walk in Group A were 15.3 and 30.6 kPa, in Group B 24.0 and 38.9 kPa and in Group C 7.8 and 13.4 kPa, respectively; at trot in Group A 18.1 and 43.4 kPa, in Group B 29.7 and 53.3 kPa and in Group C 9.8 and 21.0 kPa, respectively; and at canter in Group A 21.4 and 48.9 kPa, in Group B 28.6 and 56.0 kPa and in Group C 10.9 and 24.7 kPa, respectively. Conclusion: The study shows that there is a distinguishable difference between the 3 groups regarding the mean pressure value, in all gaits.

Summary Nitric oxide (NO), prostaglandin E2 (PGE2), and the activity of neutral metalloproteinases (NMPs) were measured in conditioned media of equine synovial membrane and articular cartilage explant cultures from horses with normal joints (n = 7) and from horses affected with moderate (n = 7) or severe osteoarthritis (n = 14) as judged by macroscopic appearance. Normal articular cartilage appeared glossy and bluish-white, was of normal thickness and showed no evidence of discolouration, fibrillation or other cartilage discontinuity. Slight discolouration and fibrillation or minor clefts of the cartilage were considered as moderate OA, whereas erosions of articular cartilage down to the subchondral bone were considered as cases of severe OA. Explant cultures of equine synovial membrane and articular cartilage released the local mediators, NO and PGE2, as well as detectable levels of NMP activity into culture media. Concentrations of NO were higherin articular cartilage explants compared to synovial membrane explants, whereas concentrations of PGE2 were higher in synovial membrane explants. The NMPs with collagenolytic activities were similar in both explant cultures, whereas gelatinolytic activities were higherin synovial membrane explant cultures and caseinolytic activities were generally higher in articular cartilage explant cultures. Furthermore it was shown that concentrations or enzyme activities increased according to the severity of disease of the joints. Concentrations for NO, collagenolytic and gelatinolytic NMPs were relatively stable, whereas PGE2 and caseinolytic NMP concentrations increased over time in culture.

Periosteal transection and elevation is a standard treatment for angular limb deformities in foals. It is used to correct axis deviations in the limbs at an early age to assure that the foals grow up with straight limbs to improve their chances to reach their full potential as future athletes. Although clinically proven, its mechanisms of action were never elucidated on a more basic scientific level. In this experimental study the molecular response to periosteal stripping was investigated within the growth plate and adjacent perichondrium. The study was based on the hypothesis that a growth restraining feedback loop related to Indian hedgehog (Ihh), parathyroid hormone related protein (PTHrP) and parathyroid hormone receptors (PTHR) was responsible for the corrective effect of periosteal stripping. Twelve 3 months old lambs underwent periosteal stripping of the distal lateral radius and tibia on one side. The contralateral side served as non-operated controls. Two animals each group were sacrificed at 2, 6, 10, 14, 18 and 21 days after surgery and the growth plates with minimal adjacent bone tissue were harvested for histological investigations. After decalcification, paraffin-embedded sections with routine hematoxylin-eosin stains were prepared to assess morphology and length of growth plates, whereas immunohistochemistry of Ihh, PTHrP, PTHR and the two cytokines fibroblast(FGF) and transforming growth factor (TGF) was performed to study different protein expression between operated limbs and controls. The results indicate that periosteal stripping caused an up-regulation of Ihh in the early preand hypertrophic zone of the growth plate, followed by an increase of PTHrP mainly in the perichondrium, while an increase of PTHR was noticed in all zones, although highest in the perichondrium and hypertrophic zones. The growth factors FGF and TGF were upregulated in all zones, but FGF in response to periosteal stripping was more intensely expressed in the proliferative zone and the highest peak of TGF was found in the perichondrium. Length measurements of the various growth zones revealed significant negative correlations between the proliferative and pre-and hypertrophic zones, indicating that indeed a negative feed back loop after periosteal stripping exists coupled by the Ihh/PTHrP/PTHR cascade.The hypothesis that periosteal stripping had an effect on the Ihh/PTHrP/PTHR related feedback loop in epiphyseal growth was confirmed in this experimental study in lambs. Since these mechanisms are very basic and similar in most species, it can be safely assumed that the effects in foals are similar. In fact, the asymmetric mechanical load in animals suffering from axis deviation may even increase the enhancing effect of length correction.

In the present study the effects of „periosteal stripping“ on bone and cartilage metabolism of foals with angular limb deformities and healthy experimental lambs were examined. Five foals with angular limb deformities were treated surgically by means of „hemicircumferential transection of the periosteum and periosteal stripping“ (HCTP/HP). Before surgery as well as twice after surgery, 1,25(OH)2Vitamin D, bone and cartilage markers in the serum were determined and compared to 5 healthy foals of the same age. In addition 10 healthy lambs were treated by HCTP/HP, in which the same parameters and bone density were determined. At 22 days after surgery the lambs were sacrificed and treated and control bones were sampled and processed for immunohistochemistry. Neither in foals nor in lambs, significant differences could be observed between treated and untreated animals with regard to the parameters measured in serum. Nevertheless, both treated groups revealed a tendency for higher bone remodelling compared to control animals. This could be the result of an increased bone remodelling rate following surgery. No statistically significant difference in bone mineral density between treated and untreated animals could be detected. In contrast local changes of signal transduction related to parathyroid hormone related protein and indian hedgehog (PTHrP/Ihh) were observed using immunhistochemistry. It was concluded that HCTP/HP at the level of epiphysis and metaphysis does not lead to systemic effects, even though local events detected by immunohistochemistry point to an increased bone formation at the treated site.

The surface of cylindrical MgCa0.8 implants were differently machined which leads to smooth implants, sandblasted and threaded cylinders. 16 implants of each group were implanted into the medial femoral condylus of New Zealand White rabbits (totally n = 48). Each half of the implants remained for three and six months, respectively. After euthanasia 5 μm thin slices were produced, stained and evaluated through a semi quantitative scoring. Two specimen of each surface were used for EDX-analysis. Specified areas were examined for the appearance of predetermined elements. The EDX-analysis showed phosphorus in the edge layer of the implants. It appeared at all surface varieties. Magnesium could be found in the bone near the implants. It decreased with increasing distance to the implant site. The appearance of phosphorus indicates a possible new bone formation in the periphery of the implants. This also points to a good biocompatibility and a possible osteoinductive tendency. All bone preparations developed a fibrotic layer around the implant. It was strongest in sandblasted implants. The layer decreased from three to six months. Within the layer macrophages appeared most frequently at both defined times. They contained ingested implant material. Lymphocytes, plasma cells and foreign body cells appeared most frequently in sandblasted implants at both points in time. After six months, foreign body cells occurred exclusively at sandblasted implants. Einfluss der unterschiedlichen Oberflachenbearbeitung von resorbierbaren Implantaten aus Magnesiumlegierungen auf die Degradation – Ergebnisse der EDX-Analysen und der histologischen Untersuchungen Die Oberflache von zylindrischen MgCa0,8-Implantaten wurde unterschiedlich bearbeitet, so dass glatte, gestrahlte und Gewindezylinder resultierten. 16 Implantate jeder Oberflache wurden in die mediale Femurkondyle von New Zealand White Kaninchen implantiert (n = 48). Jeweils die Halfte der Implantate verblieb fur 3 bzw. 6 Monate im Knochen. Nach der Euthanasie wurden 5 μm dunne Schnitte hergestellt, gefarbt und durch ein semiquantitatives Scoring bewertet. Zwei Probenblocke jeder Oberflache wurden fur eine EDX-Analyse genutzt. Bestimmte Bereiche wurden auf das Vorkommen spezieller Elemente untersucht. Die EDX-Analyse ergab das Vorhandensein von Phosphor in der Degradationsschicht aller Implantate. Im Knochen direkt neben dem fruheren Implantatlager konnte Magnesium detektiert werden. Mit zunehmender Entfernung zum Implantatlager nahm der Magnesiumgehalt ab. Das Vorhandensein von Phosphor deutet eine mogliche Neubildung von Knochen im Randbereich des Implantates an. Hierin wird ein Zeichen fur eine gute Biokompatibilitat und eine mogliche osteoinduktive Wirkung von Magnesium gesehen. Bei allen Proben entwickelte sich eine Bindegewebsschicht um das Implantatlager. Gestrahlte Implantate zeigten die starkste Schicht. Nach sechs Monaten hatte die Schicht bei allen Oberflachen abgenommen. Innerhalb der Bindegewebszuge traten Makrophagen zu beiden Zeitpunkten am zahlreichsten auf. Sie enthielten aufgenommenes Implantatmaterial. Lymphozyten, Plasmazellen und Fremdkorperzellen konnten sowohl nach drei als auch nach sechs Monaten am haufigsten in gestrahlten Implantaten gefunden werden. Nach sechs Monaten wurden Fremdkorperzellen ausschlieslich bei gestrahlten Implantaten gefunden.

This study reports on in vivo particle induced X-ray emission (PIXE) measurements combined with Rutherford backscattering spectroscopy (RBS) analyses of new remodeled sheep bone formed around TiAIV screws. The implants (screws) were anodized by a modified TiMax (TM) process. The interface between the implant and the bone was carefully investigated. [Zn]/[Ca] in-depth composition profiles as well as Ca, Fe elemental maps were recorded. The thickness of new bone formed around the screw reached 300 - 400 mu m. Osteon and Osteoid phases were identified in the new bone. A higher [Zn]/[Ca] ratio was observed in the new bone as compared to the mature bone. Blood vessels were observed in the bone in close contact with the screw. This study shows the potential of ion beam analysis for biological and biomedical characterization.

The degradation of Co-Cr-Mo ASTM F75-92 hip implants after a harvesting period of 8 1/2 months in sheep was investigated. Hip prostheses and tissue samples were obtained from a medical study involving total hip arthroplasty of the cemented type in 12 sheep. Upon euthanasia, the explants were retrieved for analyses of the surfaces and evidence of degradation, while tissue samples from the interface regions were harvested for chemical analysis and evidence of Co, Cr, and Mo contents. Clear evidence of wear and corrosion was detected. Results also indicated that the modes of metal transport through the poly(methyl methacrylate) bone cement play an important role as the surface degradation mechanisms of the metal. The results are being discussed in terms of electrochemical and triboelectrochemical behaviour of the Co-Cr-Mo alloy.

Clinical drawbacks of bone grafting prompt the search for alternative bone augmentation technologies such as use of growth and differentiation factors, gene therapy, and cell therapy. Osteopromotive matrices are frequently employed for the local delivery and controlled release of these augmentation agents. Some matrices also provide an osteoconductive scaffold to support new bone growth. In this study, silkworm-derived silk fibroin was evaluated as an osteoconductive matrix for healing critical sized mid-femoral segmental defects in nude rats. Four treatment groups were assessed over eight weeks: silk scaffolds (SS) with recombinant human BMP-2 (rhBMP-2) and human mesenchymal stem cells (HMSC) that had been pre-differentiated along an osteoblastic lineage ex vivo (Group I; pdHMSC/rhBMP-2/SS); SS with rhBMP-2 and undifferentiated HMSCs (Group II; udHMSC/rhBMP-2/SS); SS and rhBMP-2 alone (Group III; rhBMP-2/SS); and empty defects (Group IV). Bi-weekly radiographs revealed a progressive and similar increase in Group I-III mean defect mineralization through post-operative week (POW) 8. Radiographs, dual energy x-ray absorptiometry, and micro-computed tomography confirmed that Groups I-III exhibited similar substantial and significantly (p

We released the infraspinatus tendons of six sheep, allowed retraction of the musculotendinous unit over a period of 40 weeks and then performed a repair. We studied retraction of the musculotendinous unit 35 weeks later using CT, MRI and macroscopic dissection. The tendon was retracted by a mean of 4.7 cm (3.8 to 5.1) 40 weeks after release and remained at a mean of 4.2 cm (3.3 to 4.7) 35 weeks after the repair. Retraction of the muscle was only a mean of 2.7 cm (2.0 to 3.3) and 1.7 cm (1.1 to 2.2) respectively at these two points. Thus, the musculotendinous junction had shifted distally by a mean of 2.5 cm (2.0 to 2.8) relative to the tendon. Sheep muscle showed an ability to compensate for approximately 60% of the tendon retraction in a hitherto unknown fashion. Such retraction may not be a quantitatively reliable indicator of retraction of the muscle and may overestimate the need for elongation of the musculotendinous unit during repair.

SummaryThe goal was to study the performance of mushroom shaped, photooxidized, osteochondral grafts in mosaicplasty focusing on graft stability and survival. Mushroom shaped, photooxidized grafts (6 mm for the cartilaginous head of the mushroom, 3 mm for the stem) were implanted in the medial femoral condyle of 10 sheep. Four transplants were inserted per condyle in an overlapping fashion using the pressfit technique (n=40 grafts in 10 condyles). The grafts were followed for 6 and 12 months. Semi-quantitative evaluation of graft performance was performed using a validated score system. All grafts were mechanically stable at 6 and 12 months with one exception, where the mushroom head broke off. The formation of cystic lesions in the subchondral bone area was minimal. Repopulation of the old photooxidized cartilage was noticed with cells invading the matrix from the subchondral bone area and also from the pannus on the surface. Fusion between host and graft cartilage was observed in some of the grafts at 12 months, while remodeling of the calcified cartilage zone and tidemark was noticed in all grafts. Results scored significantly better for the 6 months compared to the 12 months group if cartilage surface integrity was compared (p

For future clinical use as synthetic bone replacement, an injectable brushite-(chronOS-Inject) and hydroxylapatite-(Biobon) cement were compared in a drill hole model in 10 sheep over time at 2, 4, 6, 8, 16 and 24 weeks. Results were compared regarding their practical use, biocompatibiliy, resorption mechanism and subsequent new bone formation. The cements were filled into drill holes (psi 8 x 13mm) of the proximal and distal humerus, and femur and the samples evaluated macroscopically, radiologically and microscopically including histomorphometrical quantification of percentages of new bone, fibrous tissue and remnants of cements. The cement area decreased continuously from 2 to 24 weeks with chronOS-Inject, as well as the area of granules. Inversely, the subsequent new bone formation increased from 2-24 weeks accordingly. With Biobon the cement area decreased slower between 2 and 24 weeks, and the new bone formation was less. Both cements were well integrated into the bone in long bones. chronOS-Inject demonstrated good biocompatibility and was almost completely replaced through bone within 24 weeks. Biobon was resorbed considerably slower and initially a slight inflammatory reaction including bone resorption was observed within the adjacent host bone.

Two dicalcium phosphate dihydrate (DCPD) hydraulic cements and one apatite hydraulic cement were implanted in epiphyseal and metaphyseal, cylindrical bone defects of sheep. The in vivo study was performed to assess the biocompatibility of the DCPD cements, using the apatite cement as control. After time periods of 2, 4 and 6 months the cement samples were clinically and histologically evaluated. Histomorphometrically the amount of new bone formation, fibrous tissue and the area of remaining cement were measured over time. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. All cements were replaced by different amounts of new bone. The two DCPD-cements showed the highest new bone formation and least cement remnants at 6 months, whereas the apatite was almost unchanged over all time periods.

Objective : This article addresses the problem of structural design with osteochondral grafts used for cartilage resurfacing. Methods : Photooxidized cylindrical or mushroom-shaped grafts were surgically implanted in the weight bearing area of the medial and lateral femoral condyles of eight sheep (condyles: N =8/group). Both types of photooxidized grafts contained no viable chondrocytes at the time of implantation. Results were evaluated at 2 and 6 months after surgical implantation of the grafts. Qualitative and quantitative evaluation of the subchondral bone area was performed using plastic embedded sections of non-decalcified bone and cartilage specimens and placing emphasis on graft anchorage, cyst-like lesions at the base of the cartilage junction and at the base of the graft in the subchondral bone region. Cartilage morphology was studied qualitatively focusing on viability of the graft and adjacent host cartilage, while a score system was developed for semi-quantitative evaluation of the overall articular cartilage performance. The semiquantitative scores and histomorphometrical measurements were subjected to statistical analysis using a factorial analysis of variance (ANOVA-test). Results : The photooxidized mushroom-shaped grafts developed less fibrous tissue and cyst-like lesions in the subchondral bone area at 2 and 6 months compared to the cylindrical grafts. Areas of endochondral ossification and bone remodeling were noticeable in the mushroom structured grafts at 2 months, and also bone remodeling was more complete at 6 months than with the cylindrical grafts. Increased numbers of cells were seen in the basal remodeling zones of both graft types increased from the 2 months to the 6 months specimens, but mushroom structured grafts showed better results. In both graft types, however, the midzone of the cartilage matrix was still acellular at 6 months. Cells from the subchondral bone area started to penetrate the calcified cartilage zone and tide mark at 2 months and repopulated the old photooxidized cartilage matrix already at 6 months after implantation. Cartilage repopulation was dependant on a stable subchondral bone area in both types of grafts. Matrix degradation of the adjacent host cartilage was minimal at 2 and 6 months. At 6 months a junction between host and graft cartilage was already noticed in some of the mushroom-shaped grafts. Conclusion : This study confirmed the importance of the subchondral bone area for osteochondral graft survival. In addition it demonstrated that the structure of the graft influences considerably the architecture of the subchondral bone, and with this the possibility for the repopulation of the old cartilage matrix including the junction between the host and graft cartilage matrix.

A hydraulic calcium phosphate cement having dicalcium phosphate dihydrate (DCPD) as end-product of the setting reaction was implanted in a cylindrical defect in the diaphysis of sheep for up to 6 months. The composition of the cement was investigated as a function of time. After setting, the cement composition consisted essentially of a mixture of DCPD and beta-tricalcium phosphate (beta-TCP). In the first few weeks of implantation, the edges of the cement samples became depleted in DCPD, suggesting a selective dissolution of DCPD, possibly due to low pH conditions. The cement resorption at this stage was high. After 8 weeks, the resorption rate slowed down. Simultaneously, a change of the color and density of the cement center was observed. These changes were due to the conversion of DCPD into a poorly crystalline apatite. Precipitation started after 6-8 weeks and progressed rapidly. At 9 weeks, the colored central zone reached its maximal size. The fraction of beta-TCP in the cement was constant at all time. Therefore, this study demonstrates that the resorption rate of DCPD cement is more pronounced as long as DCPD is not transformed in vivo.

Defining the most adequate architecture of a bone substitute scaffold is a topic that has received much attention over the last 40 years. However, contradictory results exist on the effect of grain size and microporosity. Therefore, the aim of this study was to determine the effect of these two factors on the in vivo behaviour of β-tricalcium phosphate (β-TCP) scaffolds. For that purpose, β-TCP scaffolds were produced with roughly the same macropore size (≈ 150 μm), and porosity (≈ 80 %), but two levels of microporosity (low: 10 % / high: ≈ 25 %) and grain size (small: 1.3 μm /large: ≈ 3.3 μm). The sample architecture was characterised extensively using materialography, Hg porosimetry, micro-computed tomography (μCT), and nitrogen adsorption. The scaffolds were implanted for 2, 4 and 8 weeks in a cylindrical 5-wall cancellous bone defect in sheep. The histological, histomorphometrical and μCT analysis of the samples revealed that all four scaffold types were almost completely resorbed within 8 weeks and replaced by new bone. Despite the three-fold difference in microporosity and grain size, very few biological differences were observed. The only significant effect at p < 0.01 was a slightly faster resorption rate and soft tissue formation between 4 and 8 weeks of implantation when microporosity was increased. Past and present results suggest that the biological response of this particular defect is not very sensitive towards physico-chemical differences of resorbable bone graft substitutes. As bone formed not only in the macropores but also in the micropores, a closer study at the microscopic and localised effects is necessary.

Surgical treatment of osteoporotic distal radius fractures with locking plates does not completely prevent loss of reduction. Additional bone deficit stabilisation with the use of bone substitute materials is receiving increased attention. Most knowledge on the in vivo behavior of bone substitutes originates from a small number of animal models after its implantation in young, good vascularized bone.This paper investigates the osteoconductivity, resorption and biocompatibility of beta-tricalcium phosphate as a temporary bone replacement in osteoporotic type distal radius fractures.15 bone samples taken from the augmented area of the distal radius of elderly people during metal removal were examined.The material was found to be osteoconductive, good degradable, and biocompatible. Degrading process and remodelling to woven bone seem to require more time than in available comparative bioassays.The material is suitable for temporary replacement of lost, distal radius bone from the histological point of view.

The objective of the present study was to determine the potency of dexmedetomidine in relation to medetomidine in sheep undergoing orthopaedic surgery by comparing the anaesthetic requirements and cardiovascular changes at a dose relationship that represented equipotency in vitro. Twenty-four non-pregnant, female sheep were used. The study was carried out as a blind, randomized, experimental trial. Group 1 received 5 micrograms/kg bodyweight (BW) dexmedetomidine and group 2 received 10 micrograms/kg BW medetomidine intravenously 5 min prior to induction of anaesthesia. Anaesthesia was induced with ketamine (2.0 mg/kg BW intravenously) and maintained with isoflurane in 100% oxygen. End expired anaesthetic concentration (FEIso), end expired carbon dioxide concentration (FECO2), respiratory frequency (fR), direct arterial blood pressures, heart rates (HR) and arterial blood gases were monitored. Data were averaged over time and tested for differences between groups by independent t-tests, and analysis of variance for repeated measures. Average FEIso concentrations required to maintain a surgical plane of anaesthesia were not different between groups (1: 1.02 +/- 0.04%; 2: 0.99 +/- 0.07%). There was no difference in HR, arterial blood pressures, fR, FECO2 and arterial blood gases between groups. Average mean PaO2 were 279.54 +/- 113.37 mmHg and 220.21 +/- 102.15 mmHg with individual minimum values of 27.2 mmHg and 58.5 mmHg in groups 1 and 2, respectively. In conclusion, intravenous dexmedetomidine at 5 micrograms/kg BW and medetomidine at 10 micrograms/kg BW have the same effects on isoflurane requirements and cardiopulmonary parameters in sheep, indicating an equipotent dose relationship. Both preparations induced moderate to severe hypoxaemia in individual sheep.

Specific amplification and quantitation of nucleic acid sequences by the polymerase chain reaction (PCR) has been extensively used for the detection of viral infection and gene expression. Although successful amplification of DNA and RNA sequences extracted from paraffin embedded tissue have been described, there are presently no reports available regarding RNA analysis from bone and calcified tissues embedded in hydrophobic acrylic resin. Here we describe a general method for quantitation of specific mRNA sequences extracted from undecalcified bone sections, fixed in paraformaldehyde, and embedded in a hydrophobic acrylic resin. Total RNA was extracted from defined regions of single 50 microm sawed sections. These RNA preparations are suitable for quantitative PCR analysis of mRNA of different cytokines. In addition, the universally expressed housekeeping GAPDH mRNA proved to be useful as an amplification control and to correct for the degree of RNA degradation, which may vary considerably among samples. Reverse transcribed mRNA was amplified and quantitated in Real-Time PCR using a fluorescein labeled internal TaqMan probe.

Summary: In the present study, we evaluated the potential for aminobisphosphonates to enhance the development of bone-forming osteoblasts from progenitor cells isolated from aged female osteoporotic patients. The aminobisphosphonates tested significantly enhanced osteoblast formation and thus lend further insights into their possible mode of action in the treatment of osteoporosis. Introduction: The primary aim of this study was to evaluate the influence of aminobisphosphonates on the osteogenesis of human bone marrow stromal cells (hBMSCs) and mineralization of differentiating bone-forming cells isolated from osteoporotic patients. Methods: The influence of aminobisphosphonate treatment on hBMSC osteogenesis was assessed by the quantitative measurement of alkaline phosphatase (ALP) activity, in addition to quantitative reverse transcription polymerase chain reaction and Western blot analysis of known osteogenic markers. Mineralized matrix formation by hBMSC-derived osteoblasts was visualized and quantified using Alizarin red staining. Results: hBMSC cultures treated with osteogenic medium supplemented with zoledronate demonstrated a significant increase in Alizarin red staining after 3weeks as compared to cells cultured in osteogenic medium alone. Similarly, cultures of differentiating hBMSCs isolated from patients receiving alendronate treatment also demonstrated an increased propensity for mineralization, even in the absence of further in vitro stimulation by zoledronate. The stimulatory effects of aminobisphosphonate treatment on hBMSC-derived osteoblast-mediated mineralization were independent of any alterations in ALP activity, although significant decreases in the expression levels of osteopontin (SPP1) were evident in hBMSCs following exposure to aminobisphosphonates. Further analysis including Western blotting and loss-of-function studies revealed osteopontin as having a negative influence on the mineralization of differentiating osteoporotic bone-forming cells. Conclusions: The results presented here demonstrate for the first time that aminobisphosphonate treatment of osteoporotic hBMSCs enhances their capacity for osteoblast formation and subsequent mineral deposition, thus supporting the concept of aminobisphosphonates as having an osteoanabolic effect in osteoporosis.

SummaryDue to a perceived need for better information on the occurrence and repair of equine fractures, we developed a system designed to gather data on an interinstitutional basis. Fundamental to our task was the creation of a system of classifying the injuries most commonly treated by internal fixation, but including other fracture forms as well.The initial ("paper") documentation system, designed along the lines of the existing AO/ASIF Human format was praised by pilot study participants for its thoroughness and relevance, but individual clinician compliance was low due to the system’s length and complexity. The present ("diskette") version was designed for use with the Apple Macintosh, and was later modified for IBM PCs and their clones. It is currently being distributed to participating AO/ASIF Vet member clinics. The AO/ASIF EFDS was designed with a view toward crossover with existing human and developing small animal systems. As such it should provide an important building block for efforts in veterinary comparative orthopedics and traumatology.The need for a classification of commonly occurring equine fractures was recognized, and a corresponding system developed. Originally conceived on paper with computer-readable sheets, the system was later modified to be committed to diskettes. In its current form, the system is in use documenting the outcome of repair of exercise induced fractures. Updates will incorporate other (e.g. long bone) fractures, and long-term follow-up data.

Similar to human decubitus ulcers, local high pressure points from ill-fitting saddles induce perfusion disturbances of different degrees resulting in tissue hypoxia and alteration in sweat production.To relate the different clinical manifestations of saddle sores to the magnitude of saddle pressures at the location of the withers.Sixteen horses with dry spots after exercise (Group A) and 7 cases presented with acute clinical signs of saddle pressure in the withers area (Group B) were compared with a control group of 16 sound horses with well fitting saddles (Group C). All horses underwent a saddle pressure measurement at walk, trot and canter. Mean and maximal pressures in the area of interest were compared between groups within each gait.Mean pressures differed significantly between groups in all 3 gaits. Maximal pressure differed between groups at trot; at walk and canter, however, the only significant difference was between Group C and Groups A and B, respectively, (P0.05). Mean and maximal pressures at walk in Group A were 15.3 and 30.6 kPa, in Group B 24.0 and 38.9 kPa and in Group C 7.8 and 13.4 kPa, respectively; at trot in Group A 18.1 and 43.4 kPa, in Group B 29.7 and 53.3 kPa and in Group C 9.8 and 21.0 kPa, respectively; and at canter in Group A 21.4 and 48.9 kPa, in Group B 28.6 and 56.0 kPa and in Group C 10.9 and 24.7 kPa, respectively.The study shows that there is a distinguishable difference between the 3 groups regarding the mean pressure value, in all gaits.

Background: Preliminary studies investigated advanced scaffold design and tissue engineering approaches towards restoring congruent articulating surfaces in small joints. - Materials and methods: Anatomical femoral and tibial cartilage constructs, fabricated by three-dimensional fibre deposition (3DF) or compression moulding/particulate leaching (CM), were evaluated in vitro and in vivo in an autologous rabbit model. Effects of scaffold pore architecture on rabbit chondrocyte differentiation and mechanical properties were evaluated following in vitro culture and subcutaneous implantation in nude mice. After femoral and tibial osteotomy and autologous implantation of tissue-engineered constructs in rabbit knee joints, implant fixation and joint articulation were evaluated. - Results: Rapid prototyping of 3DF architectures with 100% interconnecting pores promoted homogeneous distribution of viable cells, glycosaminoglycan (GAG) and collagen type II; significantly greater GAG content and differentiation capacity (GAG/DNA) in vitro compared to CM architectures; and higher mechanical equilibrium modulus and dynamic stiffness (at 0.1 Hz). Six weeks after implantation, femoral and tibial constructs had integrated with rabbit bone and knee flexion/extension and partial load bearing were regained. Histology demonstrated articulating surfaces between femoral and tibial constructs for CM and 3DF architectures; however, repair tissue appeared fibrocartilage-like and did not resemble implanted cartilage. - Conclusions: Anatomically shaped, tissue-engineered constructs with designed mechanical properties and internal pore architectures may offer alternatives for reconstruction or restoration of congruent articulating surfaces in small joints.

Purpose: A non-spherical femoral head is a known risk factor for early osteoarthritis of the hip joint. Recently, a new pathomechanism termed femoro-acetabular impingement has been postulated as an underlying cause. This mechanism is postulated to represent an abutment conflict between the non-spherical portion of the head/neck junction and the acetabular rim during extreme flexion and internal rotation. It is thought to lead to repetitive trauma resulting in subsequent lesions of the labrum and adjacent cartilage at the acetabular rim or femoral head. The aim of this research study is to confirm in an animal model, that a non-spherical head contour leads to primary lesions at the acetabulum and at the nonspherical portion of the femoral head similar to the findings in human hip joints. Methods: Sheep have been chosen as animal model since the acetabular anatomy is close to that in humans including the presence of a labrum and the femoral head has a distinct non-spherical extension of the cartilage in its superior portion. By performing an intertrochanteric adduction osteotomy of the proximal femur the non-spherical portion was rotated toward the weight bearing zone and created similar impingement conditions during the end range of flexion as postulated in young adult human beings. In a pilot study with 6 sheep localized peripheral hip joint lesions could be produced at the acetabular rim and the non-spherical portion of the head similar to the finding in humans. For this study a total of 16 sheep was chosen. The sheep were divided into 4 groups, each group with 4 sheep that were sacrificed after 14, 22, 30, 38-weeks after surgery. After sacrifice the joint cartilage was evaluated for visible alterations macroscopically according to grading by Beck et al. Thereafter samples were harvested of standardized segments on both, the operated and non-operated (control) sides for histological work-up using conventional staining methods with Toluidin-blue O to evaluate proteoglycan depletion and grading of cartilage alterations according to Mankin. Results: Localized labral lesions as also typically seen in humans were present in 14 out of 16 hips on the operated side versus 2 lesions on the unoperated side. Cartilage lesions including flaps, tears or superficial fraying were seen in all 16 operated hips in the caudodorsal segment of the acetabulum versus alterations in 3 out of 16 hips on the unoperated side (different stages of alteration showed in Figure). Histochemical staining confirmed the macroscopic findings and showed statistically significant higher degenerative changes according to the Mankin staging in the caudodorsal segment on the operated side versus the non-operated side. Conclusions: With the presented animal model a cam impingementmechanism and localized, peripheral intraarticular lesions of the hip similar those seen in humans could be reproduced. Therefore a model of development of early osteoarthritis in the hip with different stages of the disease could be defined. This allows to develop and to evaluate new invasive and non-invasive treatment methods for this pathomechanism. It will be also used to further clarify the sequential steps of the osteoarthritic process and help to define the ideal time point for surgical interventions.

Titanium implants have a tendency for high bone-implant bonding, and, in comparison to stainless steel implants are more difficult to remove. The current study was carried out to evaluate, i) the release strength of three selected anodized titanium surfaces with increased nanohardness and low roughness, and ii) bone-implant bonding in vivo. These modified surfaces were intended to give improved anchorage while facilitating easier removal of temporary implants.The new surfaces were referenced to a stainless steel implant and a standard titanium implant surface (TiMAX). In a sheep limb model, healing period was 3 months. Bone-implant bonding was evaluated either biomechanically or histologically.The new surface anodized screws demonstrated similar or slightly higher bone-implant-contact (BIC) and torque release forces than the titanium reference. The BIC of the stainless steel implants was significant lower than two of the anodized surfaces (p = 0.04), but differences between stainless steel and all titanium implants in torque release forces were not significant (p = 0.06).The new anodized titanium surfaces showed good bone-implant bonding despite a smooth surface and increased nanohardness. However, they failed to facilitate implant removal at 3 months.

OBJECTIVES: Implementation of an experimental model to compare cartilage MR imaging by means of histological analyses. MATERIAL AND METHODS: MRI was obtained from 4 patients expecting total knee replacement at 1.5 and/or 3T prior surgery. The timeframe between pre-op MRI and knee replacement was within two days. Resected cartilage-bone samples were tagged with Ethi((R))-pins to reproduce the histological cutting course. Pre-operative scanning at 1.5T included following parameters for fast low angle shot (FLASH: TR/TE/FA=33ms/6ms/30 degrees , BW=110kHz, 120mmx120mm FOV, 256x256 matrix, 0.65mm slice-thickness) and double echo steady state (DESS: TR/TE/FA=23.7ms/6.9ms/40 degrees , BW=130kHz, 120x120mm FOV, 256x256 matrix, 0.65mm slice-thickness). At 3T, scan parameters were: FLASH (TR/TE/FA=12.2ms/5.1ms/10 degrees , BW=130kHz, 170x170mm FOV, 320x320, 0.5mm slice-thickness) and DESS (TR/TE/FA=15.6ms/4.5ms/25 degrees , BW=200kHz, 135mmx150mm FOV, 288x320matrix, 0.5mm slice-thickness). Imaging of the specimens was done the same day at 1.5T. MRI (Noyes) and histological (Mankin) score scales were correlated using the paired t-test. Sensitivity and specificity for the detection of different grades of cartilage degeneration were assessed. Inter-reader and intra-reader reliability was determined using Kappa analysis. RESULTS: Low correlation (sensitivity, specificity) was found for both sequences in normal to mild Mankin grades. Only moderate to severe changes were diagnosed with higher significance and specificity. The use of higher field-strengths was advantageous for both protocols with sensitivity values ranging from 13.6% to 93.3% (FLASH) and 20.5% to 96.2% (DESS). Kappa values ranged from 0.488 to 0.944. CONCLUSIONS: Correlating MR images with continuous histological slices was feasible by using three-dimensional imaging, multi-planar-reformat and marker pins. The capability of diagnosing early cartilage changes with high accuracy could not be proven for both FLASH and DESS.

Summary Objectives: Titanium implants have a tendency for high bone-implant bonding, and, in comparison to stainless steel implants are more difficult to remove. The current study was carried out to evaluate, i) the release strength of three selected anodized titanium surfaces with increased nanohardness and low roughness, and ii) bone-implant bonding in vivo. These modified surfaces were intended to give improved anchorage while facilitating easier removal of temporary implants. Material and methods: The new surfaces were referenced to a stainless steel implant and a standard titanium implant surface (TiMAX™). In a sheep limb model, healing period was 3 months. Bone-implant bonding was evaluated either biomechanically or histologically. Results: The new surface anodized screws demonstrated similar or slightly higher bone-implantcontact (BIC) and torque release forces than the titanium reference. The BIC of the stainless steel implants was significant lower than two of the anodized surfaces (p=0.04), but differences between stainless steel and all titanium implants in torque release forces were not significant (p=0.06). Conclusion: The new anodized titanium surfaces showed good bone-implant bonding despite a smooth surface and increased nanohardness. However, they failed to facilitate implant removal at 3 months.

Advanced surface modifications and materials were tested on the same implant geometry. Six types of dental implants were tested for osseointegration after 2, 4 and 8 weeks in a sheep pelvis model. Four titanium implant types were treated with newly developed surface modifications, of which two were chemically and two were pharmacologically modified. One implant was made of zirconia. A sandblasted and acid-etched titanium surface was used as reference. The chemically modified implants were plasma-anodized or coated with calcium phosphate. The pharmacological coatings contained either bisphosphonate or collagen type I with chondroitin sulphate. The implants were evaluated using macroscopic, radiographic and histomorphometric methods. All implants were well osseointegrated at the time of death. All titanium implants had similar bone implant contact (BIC) at 2 weeks (57-61%); only zirconia was better (77%). The main BIC increase was between 2 and 4 weeks. The pharmacologically coated implants (78-79%) and the calcium phosphate coating (83%) showed similar results compared with the reference implant (80%) at 8 weeks. There were no significant differences in BIC. Compared with previous studies the results of all implants were comparatively good.

The goal was to study the performance of mushroom shaped, photooxidized, osteochondral grafts in mosaicplasty focusing on graft stability and survival. Mushroom shaped, photooxidized grafts (6 mm for the cartilaginous head of the mushroom, 3 mm for the stem) were implanted in the medial femoral condyle of 10 sheep. Four transplants were inserted per condyle in an overlapping fashion using the pressfit technique (n=40 grafts in 10 condyles). The grafts were followed for 6 and 12 months. Semi-quantitative evaluation of graft performance was performed using a validated score system. All grafts were mechanically stable at 6 and 12 months with one exception, where the mushroom head broke off. The formation of cystic lesions in the subchondral bone area was minimal. Repopulation of the old photooxidized cartilage was noticed with cells invading the matrix from the subchondral bone area and also from the pannus on the surface. Fusion between host and graft cartilage was observed in some of the grafts at 12 months, while remodeling of the calcified cartilage zone and tidemark was noticed in all grafts. Results scored significantly better for the 6 months compared to the 12 months group if cartilage surface integrity was compared (p0.05). In all other variables no significant differences were found between groups. Despite moderate graft recession in the 12 months group partial fusion of grafts and functional results were satisfactory. The photooxidized mushroom shaped osteochondral transplants may be a suitable type of graft for functional results in cartilage resurfacing if stable anchorage of the grafts can be achieved.

For future clinical use as synthetic bone replacement, an injectable brushite-(chronOS-Inject) and hydroxylapatite-(Biobon) cement were compared in a drill hole model in 10 sheep over time at 2, 4, 6, 8, 16 and 24 weeks. Results were compared regarding their practical use, biocompatibiliy, resorption mechanism and subsequent new bone formation. The cements were filled into drill holes (psi 8 x 13mm) of the proximal and distal humerus, and femur and the samples evaluated macroscopically, radiologically and microscopically including histomorphometrical quantification of percentages of new bone, fibrous tissue and remnants of cements. The cement area decreased continuously from 2 to 24 weeks with chronOS-Inject, as well as the area of granules. Inversely, the subsequent new bone formation increased from 2-24 weeks accordingly. With Biobon the cement area decreased slower between 2 and 24 weeks, and the new bone formation was less. Both cements were well integrated into the bone in long bones. chronOS-Inject demonstrated good biocompatibility and was almost completely replaced through bone within 24 weeks. Biobon was resorbed considerably slower and initially a slight inflammatory reaction including bone resorption was observed within the adjacent host bone.

Summary Objective: The aim of this study was to learn whether partial resection of the acetabular labrum would lead to degenerative arthritis in an ovine model. Methods: A 2 cm segment of labrum was removed from one hip in 18 mature Swiss Alpine sheep and a sham procedure was performed on the opposite side. Animals were permitted ad lib activity until sacrifice at 6, 12 or 24 weeks. The hip joint was removed en bloc, and loaded with a force of one body weight, using a custom device designed to recreate a physiologic joint reaction force. While under load, the joint was plunge frozen, and then fixed by freeze substitution using aldehydes in methanol/acetone solvents. The entire joint was embedded in methacrylate and sectioned in a standardized frontal plane following the reaction force and including the femoral neck and the acetabular fossa. The sections were evaluated for concentricity and evidence of arthrosis. Six hip joints of three sheep with no surgical procedure were loaded with high or low loads and served as non-surgical controls. Results: Degenerative changes were present in all surgical hips, but the changes were symmetrical and mild. In 16 of 18 hips, the labrum regenerated to the extent that dense fibrous scar extending from the surgically denuded origin filled the defect. Conclusion: Resection of the labrum does not cause rapid degeneration or altered stability of the sheep hip. © 2004 OsteoArthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Objective : This article addresses the subchondral bone integrity in cartilage resurfacing by comparing fresh, untreated auto-, xeno-, and photooxidized osteochondral allo- and xenografts. Photooxidation was expected to improve mechanical stability of the osteochondral grafts through an improved linkage of the collagen fibers within the bone matrix. Design : Untreated auto- and xenografts and with photooxidation pretreated allo- and xenografts were surgically implanted in femoral condyles of sheep ( n =40). After 2, 6, 12 and 18 months results were evaluated histologically using non-decalcified bone embedded in acrylic resin. Qualitative evaluation was performed with emphasis on bone matrix, biomechanical stability of graft anchorage, formation of cystic lesions, and bone resorption and formation. Quantitative evaluation of the total subchondral bone area was conducted histomorphometrically. Statistical analysis (factorial ANOVA test) was used to compare differences between groups with respect to the percentage of bone matrix and fibrous tissue per section. Results : Subchondral bone resorption was fastest in untreated, fresh autografts, followed by photooxidized allografts, untreated, fresh xenografts and last pretreated photooxidized xenografts. Cystic lesions were seen in all types of grafts, but were most pronounced at 6 months in autografts and least in photooxidized grafts. Cyst-like lesions had subsided substantially in the untreated auto- and photooxidized xenografts, if no graft dislocation occurred during the healing period. Mononuclear cell infiltration and an increase in the presence of multinuclear cells were observed at 2 months, mostly in untreated autografts, followed by photooxidized allo- and untreated xenografts. They were much higher in numbers compared to photooxidized grafts, at least in the early specimens at 2 months. Graft stability was linked to the rate of bone resorption. Conclusion : Substantial resorption of the subchondral bone, involving the development of cyst-like lesions, lead to dislocation and finally to cartilage matrix degradation of the grafts. The process of photooxidation decreased the speed of bone resorption in osteochondral grafts and, thus, improved graft stability and cartilage survival. These results suggest that the remodeling of the subchondral bone of the host and the graft within the first 6 months is an important factor in graft stability and overall results of cartilage resurfacing.

This article addresses the problem of structural design with osteochondral grafts used for cartilage resurfacing.Photooxidized cylindrical or mushroom-shaped grafts were surgically implanted in the weight bearing area of the medial and lateral femoral condyles of eight sheep (condyles: N=8/group). Both types of photooxidized grafts contained no viable chondrocytes at the time of implantation. Results were evaluated at 2 and 6 months after surgical implantation of the grafts. Qualitative and quantitative evaluation of the subchondral bone area was performed using plastic embedded sections of non-decalcified bone and cartilage specimens and placing emphasis on graft anchorage, cyst-like lesions at the base of the cartilage junction and at the base of the graft in the subchondral bone region. Cartilage morphology was studied qualitatively focusing on viability of the graft and adjacent host cartilage, while a score system was developed for semi-quantitative evaluation of the overall articular cartilage performance. The semiquantitative scores and histomorphometrical measurements were subjected to statistical analysis using a factorial analysis of variance (ANOVA-test).The photooxidized mushroom-shaped grafts developed less fibrous tissue and cyst-like lesions in the subchondral bone area at 2 and 6 months compared to the cylindrical grafts. Areas of endochondral ossification and bone remodeling were noticeable in the mushroom structured grafts at 2 months, and also bone remodeling was more complete at 6 months than with the cylindrical grafts. Increased numbers of cells were seen in the basal remodeling zones of both graft types increased from the 2 months to the 6 months specimens, but mushroom structured grafts showed better results. In both graft types, however, the midzone of the cartilage matrix was still acellular at 6 months. Cells from the subchondral bone area started to penetrate the calcified cartilage zone and tide mark at 2 months and repopulated the old photooxidized cartilage matrix already at 6 months after implantation. Cartilage repopulation was dependent on a stable subchondral bone area in both types of grafts. Matrix degradation of the adjacent host cartilage was minimal at 2 and 6 months. At 6 months a junction between host and graft cartilage was already noticed in some of the mushroom-shaped grafts.This study confirmed the importance of the subchondral bone area for osteochondral graft survival. In addition it demonstrated that the structure of the graft influences considerably the architecture of the subchondral bone, and with this the possibility for the repopulation of the old cartilage matrix including the junction between the host and graft cartilage matrix.