Inflammatory tissue response in human soft tissue is caused by a higher particle load near carbon fiber-reinforced PEEK compared to titanium plates.

Titanium as the leading implant material in locked plating is challenged by polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK), which became the focus of interest of researchers and manufacturers in recent years. However, data on human tissue response to these new implant materials are rare. Osteosynthesis plates and peri­implant soft tissue samples of 16 healed proximal humerus fractures were examined (n = 8 CFR-PEEK, n = 8 titanium). Soft tissue was analyzed by immunohistochemistry and µCT. The entrapped foreign bodies were further examined for their material composition by FTIR. To gain insight into their origin and formation mechanism, explanted and new plates were evaluated by SEM, EDX, profilometry and HR-CT. In the peri­implant soft tissue of the CFR-PEEK plates, an inflammatory tissue reaction was detected. Tissues contained foreign bodies, which could be identified as tantalum wires, carbon fiber fragments and PEEK particles. Titanium particles were also found in the peri­implant soft tissue of the titanium plates but showed a less intense surrounding tissue inflammation in immunohistochemistry. The surface of explanted CFR-PEEK plates was rougher and showed exposed and broken carbon fibers as well as protruding and deformed tantalum wires, especially in used screw holes, whereas scratches were identified on the titanium plate surfaces. Particles were present in the peri­implant soft tissue neighboring both implant materials and could be clearly assigned to the plate material. Particles from both plate materials caused detectable tissue inflammation, with more inflammatory cells found in soft tissue over CFR-PEEK plates than over titanium plates. STATEMENT OF SIGNIFICANCE: Osteosynthesis plates are ubiquitously used in various medical specialties for the reconstruction of bone fractures and defects and are therefore indispensable for trauma surgeons, ENT specialists and many others. The leading implant material are metals such as titanium, but recently implants made of polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK) have become increasingly popular. However, little is known about human tissue reaction and particle generation related to these new implant types. To clarify this question, 16 osteosynthesis plates (n = 8 titanium and n = 8 CFR-PEEK) and the overlying soft tissue were analyzed regarding particle occurrence and tissue inflammation. Tissue inflammation is clinically relevant for the development of scar tissue, which is discussed to cause movement restrictions and thus contributes significantly to patient outcome.

Functional outcomes before and after implant removal in patients with posttraumatic shoulder stiffness and healed proximal humerus fractures: does implant material (PEEK vs. titanium) have an impact? - a pilot study.

BACKGROUND: Posttraumatic shoulder stiffness remains a problem after proximal humerus fracture (PHF) despite good healing rates. The aim of this pilot study was to determine whether the implant material and overlying soft tissue have an effect on shoulder range of motion (ROM) before and after implant removal (IR). METHODS: 16 patients (mean age 55.2 ± 15.3 (SD) years; 62.5% female) were included who underwent operative treatment with locking plates of either carbon fiber reinforced Polyetheretherketone (PEEK) (PEEKPower® humeral fracture plate, Arthrex, Naples, Florida, USA, n = 8) or titanium alloy (Ti) (Philos®, DePuy Synthes, Johnson & Johnson Medical, Raynham, Massachusetts, USA, n = 8) for PHF. All patients presented with a limited ROM and persistent pain in everyday life after the fracture had healed, whereupon IR was indicated. ROM before and after IR were compared as well as the Constant Score (CS) and the CS compared to the contralateral shoulder (%CS) 1 year after IR. RESULTS: In group PEEK, elevation was 116.3° ± 19.2° pre- and 129.4° ± 23.7° post-IR (p = 0.027). External rotation was 35.0° ± 7.6° pre- and 50.6° ± 21.8° post-IR (p = 0.041). External rotation with the humerus abducted 90° was 38.8° ± 18.1° pre- and 52.5° ± 25.5° post-IR (p = 0.024). In group Ti, elevation was 110.0° ± 34.6° pre- and 133.8° ± 31.1° post-IR (p = 0.011). External rotation with the humerus at rest was 33.8° ± 23.1° pre- and 48.8° ± 18.7° post-IR (p = 0.048). External rotation with the humerus abducted 90° was 40.0° ± 31.6° pre- and 52.5° ± 22.5° post-IR (p = 0.011). Comparison of the two implant materials showed no significant difference. The overall CS was 90.3 ± 8.8, the %CS was 91.8% ± 14.7%. CONCLUSION: There was no significant difference in ROM, CS and %CS with respect to plate materials, although lower cell adhesion is reported for the hydrophobic PEEK. However, all patients showed improved functional outcomes after IR in this pilot study. In patients with shoulder stiffness following locked plating for PHF, implants should be removed and open arthrolysis should be performed, independently from the hardware material. LEVEL OF EVIDENCE: II.

[Principles of tendon healing at the shoulder and consequences for their treatment : Importance of platelet-rich plasma and regenerative medicine]. / Grundlagen der Sehnenheilung an der Schulter und Konsequenzen für ihre Therapie : Stellenwert des plättchenreichen Plasmas und regenerativer Medizin.

Tendon pathologies are a frequent cause of shoulder pain and can lead to significant decline in the quality of life. Conservative treatment is suitable for most tendon pathologies. In addition to classical conservative treatment options, such as physiotherapy, oral analgesia and infiltrations, there are a number of additive treatment options to promote structural tendon healing and clinical outcome. Furthermore, there are approaches to improve the results of the surgical treatment of tendon injuries by biological augmentation. The objective of this article is to give an overview of biological and regenerative therapeutic options in the treatment of tendon injuries of the shoulder. Therefore, the anatomical and molecular biological principles of the tendon structure and their importance for tendon healing are explained in order to highlight the various therapeutic options for daily practice. Biological augmentation procedures and regenerative medicine represent a promising therapeutic option for tendon injuries of the shoulder, however, the benefits are so far supported by little or no evidence at all.

A cluster of two human cases of tick-borne encephalitis (TBE) transmitted by unpasteurised goat milk and cheese in Germany, May 2016.

In May 2016, two cases of tick-borne encephalitis (TBE) were confirmed by serology (positive IgM and IgG antibodies against TBE virus (TBEV) in serum), with a possible link to raw milk and cheese from a goat farm in a region in Baden-Württemberg, Germany not previously known as TBE-endemic. The outbreak investigation identified 32 consumers of goat dairy products (29 consumers, one farm employee, two owners) of whom none had IgM antibodies against TBEV 3-8 weeks after consumption. Of the 27 notified TBE cases in the State, none reported consumption of raw goat milk or cheese from the suspected farm. Five of 22 cheese samples from 18 different batches were RT-qPCR-positive for TBEV -genome, and two of the five samples were confirmed by virus isolation, indicating viability of TBEV in the cheese. Nine of the 45 goats had neutralising TBEV antibodies, two of them with a high titre indicating recent infection. One of 412 Ixodes ricinus was RT-qPCR-positive, and sequencing of the E gene from nucleic acid extracted from the tick confirmed TBEV. Phylogenetic analyses of tick and cheese isolates showed 100% amino acid homology in the E gene and a close relation to TBEV strains from Switzerland and Austria.

Dimensions of hard and soft tissue around adjacent, compared with single-tooth, zirconia implants.

Preservation or regeneration of the papilla has always been a challenge around consecutive implants or with implants next to teeth, and many studies have evaluated the papilla's behaviour and patterns based on surgical technique and prosthetic design, though evidence about its behaviour around zirconia implants is scarce. The aim of this study was to evaluate papilla behaviour between implants and teeth (tooth-implant group) and between consecutive implants (implant-implant group). Ninety patients with 122 zirconia implants (Straumann® PURE Ceramic Implant) were examined at the one-year follow up. We measured the effect of the distance: first from the base of the contact point of the crowns to the contact with bone at the implant site (D1); secondly, to the contact with the bone at the neighbouring tooth or implant site (D2); and thirdly on the papillary deficit (D3). In both the tooth-implant group and the implant-implant group, D1 and D2 correlated significantly with the papillary deficit (D3), whereas D2 was the major determinant factor (Spearman's rho=0.60). In both groups, when D1 and D2 were <6mm, the papilla was present every time. The papillary deficit was significantly greater in the tooth-implant group than in the implant-implant group (p=0.048). We conclude that the ideal distance from the base of the contact point to the bone contact at the implant and to the bone contact at the adjacent tooth in both groups is <6mm. The height of the bone on the teeth adjacent to implants has a significant impact on that of the papilla.

Papilla and alveolar crest levels in immediate versus delayed single-tooth zirconia implants.

The aim of this study was to determine the correlation between the papilla deficit and the distance between the bone crest at the neighbouring tooth and the contact point of the clinical crown (distance 4) for immediate and delayed zirconia implants. This prospective observational study included 78 patients with 82 implants investigated at the 1-year follow-up. Patients received single-unit zirconia implants (Straumann PURE Ceramic Implant with ZLA surface) that were placed using either the delayed (group A) or immediate (group B) protocol after tooth extraction. The distance of the alveolar crest of the neighbouring tooth to the height of the interdental papilla and the absence of the papilla were also assessed. There was a strong correlation between the papilla deficit and distance 4 in group A (Spearman's rho=0.64). However, in group B, only a weak correlation between the two distances was found (Spearman's rho=0.28). A full soft tissue margin was generated when distance 4 was 7-8mm or less. Delayed implant placement showed a critical distance between the alveolar crest at the neighbouring tooth and the contact point of the crown risking a visible papilla deficit of between 7mm and 8mm.

Stem cells and bFGF in tendon healing: Effects of lentiviral gene transfer and long-term follow-up in a rat Achilles tendon defect model.

BACKGROUND: The influence of stem cells and lentiviral expression of basic fibroblastic growth factor (bFGF) on tendon healing and remodelling was investigated in an in-vivo long-term (12 weeks) rat Achilles tendon defect model. METHODS: In sixty male Lewis rats, complete tendon defects (2.4 mm) were created and either left untreated (PBS) or treated by injection of stem cells lentivirally expressing the enhanced green fluorescence marker gene eGFP (MSC-LV-eGFP) or basic fibroblast growth factor bFGF (MSC-LV-bFGF). Tendons were harvested after 12 weeks and underwent biomechanical and (immuno)-histological analysis. RESULTS: After 12 weeks the mean ultimate load to failure ratio (treated side to contralateral side) in biomechanical testing reached 97 % in the bFGF-group, 103 % in the eGFP-group and 112 % in the PBS-group. Also in the stiffness testing both MSC groups did not reach the results of the PBS group. Histologically, the MSC groups did not show better results than the control group. There were clusters of ossifications found in all groups. In immunohistology, only the staining collagen-type-I was strongly increased in both MSC groups in comparison to PBS control group. However, there were no significant differences in the (immuno)-histological results between both stem cell groups. CONCLUSION: The biomechanical and (immuno)-histological results did not show positive effects of the MSC groups on tendon remodelling in a long-term follow-up. Interestingly, in later stages stem cells had hardly any effects on biomechanical results. This study inspires a critical and reflected use of stem cells in tendon healing.

[Macroscopic and functional anatomy of the apophyseal plate]. / Makroskopische und funktionelle Anatomie der Apophysenfugen.

Apophyses are growth zones attached to the shaft (corpus) of larger bones. They vary in size and develop their own ossification centres or form as part of an usually fibrocartilaginous tendon or ligament insertion. The structure of the cartilaginous apophyseal plate is very similar to that of an epiphyseal growth plate and like these they are adapted to withstand perpendicular compressive forces without becoming harmed. This is best highlighted by the fact that their mineralized borders always orient themselves perpendicular to the overall resulting force vector. The edges of the apophyseal plates are characteristically bent which allows them to resist moderate shear forces. Like the epiphyseal plates the apophyseal plates exhibit a zonal organization which is not very well adapted to permanently withstand shear forces, especially if they occur under dynamic conditions. In these situations the tendinous insertions with their collagen fibre anchoring system have to provide compensation when balancing the load transmitted across the system.

[Anatomy of the acromioclavicular and coracoclavicular region. Functional and clinical aspects]. / Anatomie der akromiokorakoklavikulären Region. Funktionell-klinische Aspekte.

BACKGROUND: The acromioclavicular (AC) joint connects the acromion with the lateral end of the clavicle and constitutes an important load-transmitting element between the upper extremity and the skeleton of the trunk. AIM: This review discusses functional aspects that relate the AC and the coracoclavicular (CC) ligaments to AC joint instability and lateral clavicle fracture. RESULTS: In terms of stability the AC and CC ligaments play a pivotal role for this region. Under normal conditions the restraint system is balanced and becomes unbalanced in cases of injury such as AC joint instability or lateral clavicular fractures. Skeletal injuries frequently affect the ligaments with their usually sharp-angled insertion sites, which alters the function of the restraint system. As a consequence these injuries lead to multidirectional dislocating forces acting on the scapula in relationship to the lateral end of the clavicle. Previously, special attention was given to the vertical dislocation of the lateral clavicle, whereas less attention was paid to other factors which could lead to dislocation in other directions. Therefore, in this review emphasis is placed on the anatomical principles of multidirectional dislocation of the AC joint the fractured lateral clavicle. CONCLUSION: Current clinical classification schemes fail to sufficiently include these multidirectional dislocating forces; however, they have to be considered when choosing the appropriate treatment modality. Thus, understanding the anatomical and functional context of the AC/CC region is essential for a sound management of AC joint injuries and fractures of the distal clavicle.

Storage of RBCs results in an increased susceptibility for complement-mediated degradation.

OBJECTIVE: The objective of this study was to elucidate whether complement activation occurs during the storage of RBCs in newly formulated PAGGS-M storage medium. BACKGROUND: The reason for red blood cell (RBC) storage lesions is not yet fully understood. The contribution of complement to RBC storage lesion has not been extensively characterised. STUDY DESIGN AND METHODS: We investigated the surface expression of CD35, CD55, CD59 and CD47, as well as deposition of C3d, using flow cytometry over a storage period of up to 42 days on a weekly basis. C3d and the immunoglobulins IgG, IgM and IgA were additionally investigated via the direct antiglobulin test (DAT). The effect of contact with homologous serum for 30 min at 37 °C was also performed for C3d and CD35 and is subsequently termed as a 'transfusion simulation (TS)'. RESULTS: A weak but significant increase of C3d was observed prior to TS (anova P = 0.0103), whereas a stronger increase from 74.0 ± 12.4 to 101.2 ± 9.7 was observed post-TS (anova; P < 0.0001). These findings were confirmed by the DAT. CD35, CD55 and CD47 demonstrated a decrease in their expression over storage time (anova; P < 0.0001 each). The majority of changes occurred following 14 days. There was neither a decrease of CD59 observed nor an increase of IgG, IgM and IgA. CONCLUSION: RBCs are becoming increasingly susceptible to spontaneous complement deposition following TS, which might be associated with the decrease of C35 and CD55 by proteolytic cleavage and vesiculation during storage. As the impact of storage lesions is rather controversial, institutions involved in blood collection and administration of blood products should focus on carrying out research on the prevention of storage lesions.

Stem cells and basic fibroblast growth factor failed to improve tendon healing: an in vivo study using lentiviral gene transfer in a rat model.

BACKGROUND: The aim of this controlled study was to investigate the influence of mesenchymal stem cells (MSCs) and lentiviral (LV) expression of basic fibroblast growth factor (bFGF) on tendon remodeling in an in vivo rat model of an Achilles tendon defect. METHODS: In eighty-four male Lewis rats, complete 2.4-mm tendon defects were created and were either left untreated (the phosphate-buffered saline solution [PBS] group) or were treated with mesenchymal stem cells expressing enhanced green fluorescent protein (the MSC-LV-eGFP group) or with mesenchymal stem cells expressing basic fibroblast growth factor lentivirally (the MSC-LV-bFGF group). After fourteen and twenty-eight days, the tendons were harvested and analyzed biomechanically and immunohistologically. RESULTS: After fourteen days, both mesenchymal stem cell groups were slightly superior in biomechanical testing. However, only the PBS control group showed a significant increase in biomechanical results over time (fourteen versus twenty-eight days; p = 0.012). Biomechanical results were better after twenty-eight days for the control group than for both MSC groups. However, the difference was significant only with regard to the stiffness results in the comparison of the PBS control and the eGFP stem cell group (p = 0.024). Histologically, the MSC groups had no better results than the control group after fourteen and twenty-eight days. In immunohistology, only labeling for type-I procollagen was strongly increased in both MSC groups in comparison with the PBS control group (p = 0.0009 for the MSC-LV-bFGF group and p = 0.0041 for the MSC-LV-eGFP group at fourteen days, and p = 0.004 and p = 0.132, respectively, at twenty-eight days). There were no significant differences in the immunohistological results between the stem cell groups. CONCLUSIONS: The biomechanical and immunohistological results showed that mesenchymal stem cells in both groups had only partially positive effects on tendon remodeling in the initial stages; however, in later stages, stem cells had potentially negative effects on biomechanical results. The additional expression of bFGF in stem cells had negligible effects on tendon remodeling. CLINICAL RELEVANCE: Preliminary studies using stem cells are partially promising; however, there are no relevant clinical data showing that stem cells are of significant benefit. The present study should lead to a more critical evaluation and thoughtful use of stem cells in humans until more clinical data are available.

The direct anterior approach to the thoracolumbar junction: an anatomical feasibility study.

INTRODUCTION: The thoracolumbar junction (TJ) is traditionally exposed by lateral or posterior approaches. This usually requires splitting of the diaphragm, or extensile removal of the posterior elements. A circumferential exposure (i.e. simultaneous anterior and bilateral exposure) of the vertebral body is not possible. Direct anterior access would allow circumferential exposure of the vertebral body, with adjacent disc levels, and would avoid splitting the diaphragm or extensive removal of the posterior bony structures. MATERIALS AND METHODS: Twelve Thiel cadavers (8 f/4 m) were dissected to access T12 or L1 via a midline laparotomy. Supra- and infragastric laparatomy techniques were investigated. Six cadavers were used to reach T12 through the lesser omentum, six to reach L1 through the greater omentum. RESULTS: T12 after bluntly dissecting the lesser omentum, the lesser gastric curvature and the caudate lobe of the liver were utilised as landmarks. A small retroperitoneal incision was performed to mobilise the aorta allowing exposure of the T12 vertebra and its adjacent discs. Discectomy, corpectomy and insertion of an anterior column support were possible. The L1 level can be reached through the greater omentum by mobilising the pancreas as a single retroperitoneal structure, leaving the aorta and celiac trunk as landmarks. Retraction of the great vessels is necessary to expose L1 with its adjacent discs. Implantation of an anterior column support was possible utilising this approach. CONCLUSION: Direct anterior access to the TJ is feasible in a reproducible manner. This approach would avoid splitting the diaphragm, or dissection of the erector spinae muscles, and is likely to be less invasive than standard lateral or posterior approaches. This technique may offer a significant time reduction to surgery, especially in exposing the spine. Anterior column support can easily be performed, offering a better avoidance of kyphotic deformities.

Tissue characteristics in tendon-to-bone healing change after rotator cuff repair using botulinumneurotoxin A for temporary paralysis of the supraspinatus muscle in rats.

We hypothesized that botulinumneurotoxin A (BoNtA) positively influences tissue characteristics at the re-insertion site when used as an adjuvant prior to rotator cuff repair. One hundred and sixty Sprague-Dawley rats were randomly assigned to either a BoNtA or saline-injected control group. BoNtA or saline solution was injected into the supraspinatus muscle one week prior to repair of an artificially created supraspinatus tendon defect. Post-operatively, one subgroup was immobilized using a cast on the operated shoulder while the other had immediate mobilization. Histologically, the fibrocartilage transition zone was more prominent and better organized in the BoNtA groups when compared to the saline control group. In the immediately mobilized BoNtA groups significantly more collagen 2 at the insertion was detected than in the control groups (p<0.05). Fiber orientation of all BoNtA groups was better organized and more perpendicular to the epiphysis compared with control groups. Tendon stiffness differed significantly (p<0.05) between casted BoNtA and casted saline groups. Tendon viscoelasticity was significantly higher (p<0.05) in the immobilized saline groups no matter if repaired with increased or normal repair load. The results of this study suggest that reduction of load at the healing tendon-to-bone interface leads to improved repair tissue properties.

Anatomical assessment of iliac crest graft size for anterior spondylodesis.

Standard procedure for monosegmental anterior spondylodesis often combines anterior stabilization with autologous iliac crest graft. Recent publications defined a minimum size of the graft as a technical specification for this procedure. The cross sectional area of the graft to be transplanted should be at least 23.9% of the cross sectional area of the vertebral bodies to be fused. We investigated whether the required minimum size of autologous graft, as identified both experimentally and clinically, is compatible with the anatomical conditions in central european patients. Computed tomography scans (n = 348) of polytraumatized patients were obtained in the course of initial diagnosis. The scans were evaluated for vertebral body size and the possible size of autologous bone graft in the region of the anterior superior iliac crest. The evaluation of 348 CT scans demonstrated that 95% of the quantified iliac crest grafts would achieve the size recommended for anterior spinal fusion between T10 and T12. In 90% of all cases the planned iliac crest graft exceeded the size limit of 23,9% between concerning the endplates T10 and L2. In 85% the planned iliac crest graft exceeded the size limit of 23,9% between T10 and L3. The recommendation to take this value into account for monosegmental anterior spondylodesis should gain in importance in clinical practice.

Biomechanical comparison of three types of bone graft for anterior spondylodesis.

BACKGROUND: Anterior spondylodesis with bone grafting for fusion of spinal motion segments is a common procedure in clinical routine. Bone grafts for fusion include autologous, allogenic and xenogenic grafts that are inserted in the unstable spinal motion segment. Nevertheless, biomechanical data for autologous, allogenic and xenogenic grafts are rare. OBJECTIVE: The purpose of this study was to conduct biomechanical comparison of native and conserved bone grafts used in spondylodesis of the spine. METHODS: Grafts examined were native ovine tricortical iliac crest grafts, bovine cancellous bone blocks and ovine, tricortical iliac crest grafts, conserved in the same way as the bovine cancellous bone blocks. The grafts were tested biomechanically to failure. Compared parameters were maximum torque, maximum rotation angle and graft stiffness at failure. The Mann-Whitney-U test with Bonferroni adjustment was used for statistical analysis. RESULTS: Maximum torque at failure of the bovine cancellous bone graft did not differ significantly from that of the native ovine tricortical graft. Comparison of the conserved ovine tricortical graft revealed significantly lower values compared to the native ovine tricortical bone graft.Maximum rotation angle at failure of the untreated ovine tricortical bone grafts was significantly higher compared to the other grafts tested. Regarding graft stiffness no significant differences were found. CONCLUSIONS: Based on the functional demands exerted on the spinal motion segment, our results suggest that torsional strength and deformational behavior of the bone graft influence the stability of the spondylodesis. The native tricortical graft best fulfills this requirement.

Comparison of imaging methods used for dental implant osseous integration assessment.

Two different imaging techniques used to determine bone tissue response to dental implants were compared. Dental implants were implanted into the maxillae of 18 pigs, which were sacrificed after 4, 8 and 12 weeks. Implants with surrounding bone tissue were retrieved for methyl methacrylate histology and contact radiography. On identical sections peri-implant bone density and bone implant contact (BIC) ratio were assessed with two different imaging methods. Evaluation of Giemsa eosin stained and contact radiographed sections showed direct osseous integration for all implants and both methods showed a strong correlation with correlation coefficient r = 0.930 (P < 0.0001) for peri-implant bone density and r = 0.817 (P < 0.0001) for bone implant contact ratio. While the two imaging methods showed moderate differences for peri-implant bone density there were significant differences between the BIC values determined. In general, contact radiography tends to underestimate BIC for approximately 4.5 % (P = 0.00003).

Multiscale computational and experimental approaches to elucidate bone and ligament mechanobiology using the ulna-radius-interosseous membrane construct as a model system.

An in vivo axial loading model of the rat ulna was developed almost two decades ago. As a minimally invasive model, it lends itself particularly well for the study of functional adaptation in bone and the interosseous membrane, a ligament spanning between the radius and ulna. The objective of this paper is to review computational and experimental approaches to elucidate its applicability for the study of multiscale bone and ligament mechanobiology. Specifically, this review describes approaches, including i) measurement of strains on bone tissue surfaces, ii) development of a three-dimensional finite element (FE) mesh of a skeletally mature rat ulna, iii) parametric study of the relative influence of mechanical constants and materials properties on computational model predictions, iv) comparison of experimental and computational strain distribution data, and analysis of the radius and interosseous membrane (IOM) ligament's effect on axial load distribution through the ulna of the rat, and v) the effect of mechanical loading on transport through the IOM using different molecular weight fluorescent tagged dextrans. In the first stage of the study a computational stress analysis was performed after applying a 20 N single static load at the ulnar extremities, corresponding to values of experimental strain gauge measurements. To account for the anisotropy of the bone matrix, transverse isotraopic, elastic material properties were applied. In a parametric study, we analyzed the qualitative effect of different material properties on the global load and displacement behavior of the computational model. In a second stage, the same ulnar model used in the parametric study was extended to account for the interaction between the ulna, radius and IOM. The three-dimensional FE model of the rat forelimb confirms the influence of ulnar curvature on its deformation and underscores the influence of the radius and IOM on strain distribution through the ulna. The mode of strain, {i.e.} compression or tension, and strain distribution along the bone diaphysis correspond to those measured experimentally in vivo. When the radius and, indirectly, the IOM were loaded, the bone deformation shifted distally with respect to the diaphysis. In a final stage, the aforementioned ulnar model was used to study the permeability of fluorescent tagged dextrans with different molecular weights in the presence and absence of ulnar compression. Small molecular weight dextrans (3,000 Da) were distributed throughout the IOM in the absence of as well as after mechanical loading. Interestingly, no gradient in distribution was observed in either case. In contrast, very high molecular weight dextrans (1,000,000 Da) were observed only within vascular and lymphatic spaces in the bone (as well as periosteum) and IOM, both in the absence of and after the application of mechanical loading via end load compression. Between the two extremes, both 10 and 70 kDa tracers were distributed throughout the IOM after application of compressive loading. Loading appears to dissipate the steep gradient of fluorescent 70 kDa tracer observed along the lateral surface of the unloaded IOM and its insertion into the radius and ulna. Hence, this combined computational and experimental analysis of the ulna compression model provides new insight into multiscale mechanobiology of the ulna-radius-interosseous membrane construct and may provide new avenues for elucidation of ligament's remarkable structure-function relationships.

Attachment sites of the coracoclavicular ligaments are characterized by fibrocartilage differentiation: a study on human cadaveric tissue.

We analyzed the immunohistochemical labeling patterns of the extracellular matrix of the coracoclavicular ligaments (CCL) in order to relate the molecular composition of the attachment sites to their mechanical environment. Ligaments were exposed from 12 fresh-frozen human cadaveric samples (four males, mean age: 48.6 ± 12.1 years). Cryosection of methanol-fixed and decalcified tissue was cut and sections were labeled with a panel of monoclonal antibodies directed against collagens, proteoglycans and proteins of vascular components. Attachment sites of both ligaments showed characteristic fibrocartilaginous labeling of collagen type II, aggrecan and link protein in all samples. Labeling for type II collagen was most conspicuous at the insertion of the coracoid process. Morphometry of adjacent samples revealed a fibrocartilage zone of 10-15% in relationship with the ligament proper, where labeling for type II collagen, aggrecan and link protein was negative. The presence of fibrocartilage at both entheses of the trapezoid and conoid ligament suggests that the CCL complex is subject to shear/compression forces. A variable fibrocartilage differentiation at the entheses of both ligaments may be related to the marked change in loading and insertion angle that the ligaments undergo during shoulder movement.

In vivo performance of zirconia and titanium implants: a histomorphometric study in mini pig maxillae.

OBJECTIVES: To compare the bone tissue response to surface-modified zirconia (ZrO2 ) and titanium implants. METHODS: Cylindrical low-pressure injection moulded zirconia (ZrO2 ) implants were produced with an acid-etched surface. Titanium implants with identical shape, sandblasted and acid-etched surface (SLA) served as controls. Eighteen adult miniature pigs received both implant types in the maxilla 6 months after extraction of the canines and incisors. The animals were euthanized after 4, 8 and 12 weeks and 16 zirconia and 18 titanium implants with the surrounding tissue were retrieved, embedded in methylmethacrylate and stained with Giemsa-Eosin. The stained sections were digitized and histomorphometrically analysed with regard to peri-implant bone density (bone volume/total volume) and bone-implant contact (BIC) ratio. Statistical analysis was performed using Mann-Whitney' U-test. RESULTS: Histomorphometrical analysis showed direct osseous integration for both materials. ZrO2 implants revealed mean peri-implant bone density values of 60.4% (SD ± 9.9) at 4 weeks, 65.4% (SD ± 13.8) at 8 weeks, and 63.3% (SD ± 21.5) at 12 weeks after implantation, whereas Ti-SLA implants demonstrated mean values of 61.1% (SD ± 6.2), 63.6% (SD ± 6.8) and 68.2% (SD ± 5.8) at corresponding time intervals. Concerning the BIC ratio, the mean values for ZrO(2) ranged between 67.1% (SD ± 21.1) and 70% (SD ± 14.5) and for Ti-SLA between 64.7% (SD ± 9.4) and 83.7% (SD ± 10.3). For the two parameters investigated, no significant differences between both types of implants could be detected at any time point. CONCLUSION: The results indicate that there was no difference in osseointegration between ZrO2 implants and Ti-SLA controls regarding peri-implant bone density and BIC ratio.