Use of multiple pharmacodynamic measures to deconstruct the Nix-TB regimen in a short-course murine model of tuberculosis

A major challenge for tuberculosis (TB) drug development is to prioritize promising combination regimens from a large and growing number of possibilities. This includes demonstrating individual drug contributions to the activity of higher-order combinations. A BALB/c mouse TB infection model was used to evaluate the contributions of each drug and pairwise combination in the clinically relevant Nix-TB regimen [bedaquiline-pretomanid-linezolid (BPaL)] during the first 3 weeks of treatment at human equivalent doses. The rRNA synthesis (RS) ratio, an exploratory pharmacodynamic (PD) marker of ongoing Mycobacterium tuberculosis rRNA synthesis, together with solid culture CFU counts and liquid culture time to positivity (TTP) were used as PD markers of treatment response in lung tissue; and their time-course profiles were mathematically modeled using rate equations with pharmacologically interpretable parameters. Antimicrobial interactions were quantified using Bliss independence and Isserlis formulas. Subadditive (or antagonistic) and additive effects on bacillary load, assessed by CFU and TTP, were found for bedaquiline-pretomanid and linezolid-containing pairs, respectively. In contrast, subadditive and additive effects on rRNA synthesis were found for pretomanid-linezolid and bedaquiline-containing pairs, respectively. Additionally, accurate predictions of the response to BPaL for all three PD markers were made using only the single-drug and pairwise effects together with an assumption of negligible three-way drug interactions. The results represent an experimental and PD modeling approach aimed at reducing combinatorial complexity and improving the cost-effectiveness of in vivo systems for preclinical TB regimen development.

Use of Multiple Pharmacodynamic Measures to Deconstruct the Nix-TB Regimen in a Short-Course Murine Model of Tuberculosis

A major challenge for tuberculosis (TB) drug development is to prioritize promising combination regimens from a large and growing number of possibilities. This includes demonstrating individual drug contributions to the activity of higher-order combinations. A BALB/c mouse TB infection model was used to evaluate the contributions of each drug and pairwise combination in the clinically relevant Nix-TB regimen (bedaquiline-pretomanid-linezolid [BPaL]) during the first three weeks of treatment at human equivalent doses. RS ratio, an exploratory pharmacodynamic (PD) marker of ongoing Mycobacterium tuberculosis rRNA synthesis, to-gether with solid culture CFU and liquid culture time to positivity (TTP) were used as PD markers of treatment response in lung tissue; and their time course profiles were mathematically modeled using rate equations with pharmacologically interpretable parameters. Antimicrobial interactions were quantified using Bliss independence and Isserlis formulas. Subadditive (or antagonistic) and additive effects on bacillary load, assessed by CFU and TTP, were found for bedaquiline-pretomanid and linezolid-containing pairs, respectively. In contrast, subadditive and additive effects on rRNA synthesis were found for pretomanid-linezolid and bedaquiline-containing pairs, respectively. Additionally, accurate predictions of the response to BPaL for all three PD markers were made using only the single-drug and pairwise effects together with an assumption of negligible three-way drug interactions. The results represent an experimental and PD modeling approach aimed at reducing combinatorial complexity and improving the cost-effectiveness of in vivo systems for preclinical TB regimen development.

Current concepts review. Management of proximal tibial fractures

The management of proximal tibial fractures has evolved significantly in recent years. While the main goals of treatment - stability, restoration of the mechanical axis, and smooth articular surfaces - remain the same, methods have advanced substantially. In diagnostics, technical progress in CT and MR imaging has led to a better three-dimensional understanding of the injury. Newly developed classification systems such as the three-column concept of Luo et al. and the 10-segment concept of Krause et al. take this into account. Accordingly, there is a trend towards tailored approaches for particular fracture localizations. Parallel to this development, there is increasing evidence of the advantages of arthroscopically assisted surgical procedures. This Current Concepts article reviews classifications, diagnostics, treatment options as well as complications in fractures of the proximal tibia.

Osteogenesis and angiogenesis of a bulk metallic glass for biomedical implants

Implantation is an essential issue in orthopedic surgery. Bulk metallic glasses (BMGs), as a kind of novel materials, attract lots of attentions in biological field owing to their comprehensive excellent properties. Here, we show that a Zr61Ti2Cu25Al12 (at. %) BMG (Zr-based BMG) displays the best cytocompatibility, pronounced positive effects on cellular migration, and tube formation from in-vitro tests as compared to those of commercial-pure titanium and poly-ether-ether-ketone. The in-vivo micro-CT and histological evaluation demonstrate the Zr-based BMG can significantly promote a bone formation. Immunofluorescence tests and digital reconstructed radiographs manifest a stimulated effect on early blood vessel formation from the Zr-based BMG. Accordingly, the intimate connection and coupling effect between angiogenesis and osteogenesis must be effective during bone regeneration after implanting Zr-based BMG. Dynamic gait analysis in rats after implanting Zr-based BMG demonstrates a tendency to decrease the pain level during recovery, simultaneously, without abnormal ionic accumulation and inflammatory reactions. Considering suitable mechanical properties, we provide a realistic candidate of the Zr61Ti2Cu25Al12 BMG for biomedical applications.

Three-stage revision arthroplasty for the treatment of fungal periprosthetic joint infection: outcome analysis of a novel treatment algorithm : a prospective study

Aims

Fungal periprosthetic joint infections (fPJIs) are rare complications, constituting only 1% of all PJIs. Neither a uniform definition for fPJI has been established, nor a standardized treatment regimen. Compared to bacterial PJI, there is little evidence for fPJI in the literature with divergent results. Hence, we implemented a novel treatment algorithm based on three-stage revision arthroplasty, with local and systemic antifungal therapy to optimize treatment for fPJI.

Methods

From 2015 to 2018, a total of 18 patients with fPJI were included in a prospective, single-centre study (DKRS-ID 00020409). The diagnosis of PJI is based on the European Bone and Joint Infection Society definition of periprosthetic joint infections. The baseline parameters (age, sex, and BMI) and additional data (previous surgeries, pathogen spectrum, and Charlson Comorbidity Index) were recorded. A therapy protocol with three-stage revision, including a scheduled spacer exchange, was implemented. Systemic antifungal medication was administered throughout the entire treatment period and continued for six months after reimplantation. A minimum follow-up of 24 months was defined.

Results

Eradication of infection was achieved in 16 out of 18 patients (88.8%), with a mean follow-up of 35 months (25 to 54). Mixed bacterial and fungal infections were present in seven cases (39%). The interval period, defined as the period of time from explantation to reimplantation, was 119 days (55 to 202). In five patients, a salvage procedure was performed (three cementless modular knee arthrodesis, and two Girdlestone procedures).

Conclusion

Therapy for fPJI is complex, with low cure rates according to the literature. No uniform treatment recommendations presently exist for fPJI. Three-stage revision arthroplasty with prolonged systemic antifungal therapy showed promising results.

Cite this article: Bone Jt Open 2021;2(8):671–678.

Characteristics of functional shoulder instability

BACKGROUND

Pathologic activation pattern of muscles can cause shoulder instability. We propose to call this pathology functional shoulder instability (FSI). The purpose of this prospective study was to provide an in-detail description of the characteristics of FSI.

METHODS

In the year 2017, a total of 36 consecutive cases of FSI presenting to our outpatient clinic were prospectively collected. Diagnostic investigation included a pathology-specific questionnaire, standardized clinical scores, clinical examination, psychological evaluation, video and dynamic fluoroscopy documentation of the instability mechanism, as well as magnetic resonance imaging (MRI). In a final reviewing process, the material from all collected cases was evaluated and, according to the observed pattern, different subtypes of FSI were determined and compared.

RESULTS

Based on the pathomechanism, positional FSI (78%) was distinguished from nonpositional FSI (22%). Controllable positional FSI was observed in 6% of all cases and noncontrollable positional FSI in 72%, whereas controllable and noncontrollable nonpositional FSI were each detected in 11% of the cases. The different subtypes of FSI showed significant differences in all clinical scores (Western Ontario Shoulder Instability Index: P = .002, Rowe Score: P = .001, Subjective Shoulder Value: P = .001) and regarding functional impairment (shoulder stability: P < .001, daily activities: P = .001, sports activities: P < .001). Seventy-eight percent had posterior, 17% anterior, and 6% multidirectional instability. Although several patients showed constitutional glenoid shape alterations or soft tissue hyperlaxity, only few patients with acquired minor structural defects were observed.

CONCLUSION

FSI can be classified into 4 subtypes based on pathomechanism and volitional control. Depending on the subtype, patients show different degrees of functional impairment. The majority of patients suffer from unidirectional posterior FSI.

Risk Factors for Rotator Cuff Disease: An Experimental Study on Intact Human Subscapularis Tendons

Although several studies revealed a multifactorial pathogenesis of degenerative rotator cuff disorders, the impact and interaction of extrinsic variables is still poorly understood. Thus, this study aimed at uncovering the effect of patient- and pathology-specific risk factors that may contribute to degeneration of the rotator cuff tendons. Between 2015 and 2018, 54 patients who underwent arthroscopic shoulder surgery at three specialized shoulder clinics were prospectively included. Using tendon samples harvested from the macroscopically intact subscapularis (SSC) tendon, targeted messenger RNA expression profile analysis was performed in the first cohort (n = 38). Furthermore, histological analyses were conducted on tendon tissue samples obtained from a second cohort (n = 16). Overall, both study cohorts were comparable concerning patient demographics. Results were then analyzed with respect to specific extrinsic factors, such as patient age, body mass index, current as well as previous professions and sport activities, smoking habit, and systemic metabolic diseases. While patient age, sports-activity level, and preexisting rotator cuff lesions were considered to contribute most strongly to tendinopathogenesis, no further coherences were found. With regards to gene expression analysis, change in expression correlated most strongly with patient age and severity of the rotator cuff pathology. Further, chronic disorders increased overall gene expression variation. Taken together, our study provides further evidence that tendon degeneration is the consequence of a multifactorial process and pathological changes of the supraspinatus tendon affect the quality of SSC tendon and most likely vice versa. Therefore, the rotator cuff tendons need to be considered as a unit when managing rotator cuff pathologies. © 2019 The Authors. Journal of Orthopaedic Research^® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 38:182-191, 2020.

Reverse shoulder arthroplasty: the role of physical therapy on the clinical outcome in the mid-term to long-term follow-up

INTRODUCTION

Reverse shoulder arthroplasty shifts the rotational center of the shoulder joint caudally and medially to restore shoulder function in a rotator cuff deficient shoulder. Despite promising results in early- and mid-term follow-up, long-term loss in shoulder function has been described in the literature. A lack of exercise in elderly patients may be one reason for this loss in function. This study examines the functional benefits of physical therapy in the mid-term to long-term follow-up regarding the subjective and objective shoulder function.

MATERIALS AND METHODS

Twenty patients with a mean age of 73 years were included in this series. The study was performed as a single-center, prospective study. Initial indications for reverse shoulder arthroplasty were cuff tear arthropathy, failed anatomical shoulder arthroplasty, and fracture sequelae. The patients were clinically examined at a mean follow-up of 62 months using the Constant score (CS) and the DASH score for the operated and the non-operated shoulder. They were reevaluated using the same scores following a standardized physical therapy program of 6 weeks' duration.

RESULTS

The mean CS as well as the mean age- and gender-adjusted CS of the affected shoulder improved significantly from 53.5 to 59.3 points, and 72.7-80.8%, respectively. The subcategories activities of daily living (ADL) and range of motion (ROM) of the CS improved significantly, whereas no significant improvement was observed for the subcategories pain and strength. Evaluating the contralateral shoulder, no significant change was observed for the age- and gender-adjusted CS and the CS as well as its subcategories. We found no significant difference in the CS comparing the different etiologies prior to physical therapy.

DISCUSSION

Physical therapy plays an important role subsequent to reverse shoulder arthroplasty. It also has an effect in the mid-term to long-term follow-up regarding the range of motion as well as activities of daily living. However, physical therapy seems to have limited effect on the strength and the residual pain level.

LEVEL OF EVIDENCE

Level III.

The effect of autologous platelet rich plasma on tenocytes of the human rotator cuff

Background

Platelet rich plasma (PRP) is widely used in rotator cuff repairs but its effect on the healing process is unclear. Several cell culture studies on the effect of allogenic PRP have reported promising results but are not transferable to clinical practice.

The aim of the present study is to assess the possible effect of autologous PRP on rotator cuff tendon cells. The amount of growth factors involved with tendon-bone healing (PDGF-AB, IGF-1, TGF-β1, BMP-7 and -12) is quantified.

Methods

Rotator cuff tissue samples were obtained from (n = 24) patients grouped by age (>/< 65 years) and sex into four groups and cells were isolated and characterized. Later, autologous PRP preparations were obtained and the effect was analyzed by means of cell proliferation, collagen I synthesis and expression of collagen I and III. Furthermore, the PRPs were quantified for growth factor content by means of platelet-derived growth factor (PDGF-AB), insulin-like growth factor (IGF-1), transforming growth factor (TGF-β1), as well as bone morphogenetic protein (BMP) -7 and − 12.

Results

Cell proliferation and absolute synthesis of collagen I were positively affected by PRP exposure compared to controls (p < 0.05), but expression and relative synthesis of collagen I (normalized to cell proliferation) were significantly reduced.

PRP contained high amounts of IGF-1 and lower levels of TGF-β1 and PDGF-AB. The amounts of BMP-7 and -12 were below the detection limits.

Conclusions

PRP is a source of growth factors such involved with tendon-bone healing. PRP had an anabolic effect on the human rotator cuff tenocytes of the same individual in vitro by means of cell proliferation and absolute, but not relative collagen I synthesis.

These results encourage further studies on clinical outcomes with more comparable standards in terms of preparation and application methods.

Level of evidence

Controlled laboratory study.

[Arthroscopic double-row reconstruction of high-grade subscapularis tendon tears]

OBJECTIVE

Reconstruction of tendon integrity to maintain glenohumeral joint centration and hence to restore shoulder functional range of motion and to reduce pain.

INDICATIONS

Isolated or combined full-thickness subscapularis tendon tears (≥upper two-thirds of the tendon) without both substantial soft tissue degeneration and cranialization of the humeral head.

CONTRAINDICATIONS

Chronic tears of the subscapularis tendon with higher grade muscle atrophy, fatty infiltration, and static decentration of the humeral head.

SURGICAL TECHNIQUE

After arthroscopic three-sided subscapularis tendon release, two double-loaded suture anchors are placed medially to the humeral footprint. Next to the suture passage, the suture limbs are tied and secured laterally with up to two knotless anchors creating a transosseous-equivalent repair.

POSTOPERATIVE MANAGEMENT

The affected arm is placed in a shoulder brace with 20° of abduction and slight internal rotation for 6 weeks postoperatively. Rehabilitation protocol including progressive physical therapy from a maximum protection phase to a minimum protection phase is required. Overhead activities are permitted after 6 months.

RESULTS

While previous studies have demonstrated superior biomechanical properties and clinical results after double-row compared to single-row and transosseous fixation techniques, further mid- to long-term clinical investigations are needed to confirm these findings.

Influence of the Ag concentration on the medium-range order in a CuZrAlAg bulk metallic glass

Fluctuation electron microscopy of bulk metallic glasses of CuZrAl(Ag) demonstrates that medium-range order is sensitive to minor compositional changes. By analyzing nanodiffraction patterns medium-range order is detected with crystal-like motifs based on the B2 CuZr structure and its distorted structures resembling the martensitic ones. This result demonstrates some structural homology between the metallic glass and its high temperature crystalline phase. The amount of medium-range order seems slightly affected with increasing Ag concentration (0, 2, 5 at.%) but the structural motifs of the medium-range ordered clusters become more diverse at the highest Ag concentration. The decrease of dominant clusters is consistent with the destabilization of the B2 structure measured by calorimetry and accounts for the increased glass-forming ability.

Combined arthroscopic tenodesis of the long head of biceps and rotator cuff repair in antero-superior cuff tears

PURPOSE AND HYPOTHESIS

This study evaluates the functional and cosmetic results following fixation of the long head of the biceps (LHB) tendon at the antero-medial footprint anchor of a rotator cuff reconstruction, using the "lasso-loop" technique.

METHODS

39 patients with a mean age of 62 years with a rotator cuff tear and associated lesion of the LHB tendon were included in this study. Besides rotator cuff repair in an arthroscopic anchor technique, all patients received additional LHB tenodeses using the lasso-loop technique. Clinical follow-up consisted of the Constant score (CS), LHB score, DASH score, and WORC index. Relevant sub-items, such as elbow flexion strength and cosmesis, were compared to the contralateral arm.

RESULTS

At an average follow-up of 22 months (11-39 months), the CS resulted in an average of 81 points. The biceps-specific LHB score showed a mean value of 89 points. The analysis of the DASH score showed an average of 16.9 points and the analysis of the WORC index showed an average result of 79.7 %. Distalization of the biceps muscle was objectively in three cases (7.7 %) (as observed by the examiner) and subjectively in one of those cases (as noted by the patient). There was a loss in elbow flexion strength compared to the contralateral side; however, this loss was not statistically significant and not associated with clinical apparent re-tear or insufficiency of the tenodesis.

DISCUSSION

The arthroscopic lasso-loop tenodesis of the LHB tendon is a time and cost-efficient technique. No additional anchor is needed when included in the rotator cuff repair. Functional and cosmetical results as well as results from the biceps-specific LHB score were good to excellent. The loss in elbow flexion strength is most likely associated with concomitant rotator cuff lesion.

CONCLUSION

The lasso-loop fixation technique of the LHB tendon using the antero-medial footprint anchor in rotator cuff tears is a reliable and cost-efficient procedure.

LEVEL OF EVIDENCE

III.

Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated.

Clinical performance of lateralized versus non-lateralized reverse shoulder arthroplasty: a prospective randomized study

BACKGROUND

Reverse shoulder arthroplasty (RSA) is an established therapeutic option in the treatment of cuff tear arthropathy (CTA). Recent studies have described a positive effect of lateralization of the center of rotation, especially on postoperative rotational function. The goal of this study is to compare the outcome of non-lateralized versus lateralized RSA with particular regard to rotational function in patients with CTA.

METHODS

Thirty-four patients underwent implantation of RSA either with lateralization (n = 17) or without lateralization (n = 17) by use of a 1-cm autologous bone graft ("bony increased offset") of the humeral head for CTA. Clinical outcomes were measured with the Constant score; the Disabilities of the Arm, Shoulder and Hand score; and the Activities of Daily Living Requiring External Rotation score, as well as measurement of external rotation and determination of the external rotation lag sign with the arm at the side and at 90° of abduction, at 1 year postoperatively and at final follow-up. Computed tomography scan evaluation was performed in all patients preoperatively and at 1 year postoperatively to assess preoperative fatty infiltration of the rotator cuff and bony integration of the graft postoperatively.

RESULTS

At final follow-up, all patients showed significantly increased functional results. There were no significant differences in the evaluated parameters. If patients with degenerative changes of the teres minor were excluded, the lateralized group showed significantly increased external rotation. Bony integration of the graft could be verified on postoperative computed tomography scans in all patients.

CONCLUSION

RSA with bony lateralization shows a trend toward improved external rotation in lateralized RSA, with a statistically significant improvement in external rotation in patients with an intact teres minor.

Do patient age and sex influence tendon cell biology and clinical/radiographic outcomes after rotator cuff repair?

BACKGROUND

Many clinical and radiographic studies suggest that patient age and sex have an influence on rotator cuff (RC) repair outcomes. However, these findings result from retrospective statistical analyses and cannot provide a causal answer.

PURPOSE

To analyze whether age and sex influence the biological potential at the time of RC repair or midterm clinical and radiographic outcomes. Also assessed was the effect of the biological potential on intraindividual clinical/radiographic results.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 40 patients underwent arthroscopic RC repair. At the time of surgery (t = 0), supraspinatus tendon biopsy specimens were obtained, cultivated, and assessed for their biological potential, particularly (1) cell growth and (2) collagen type I production. After a follow-up at 24 months (t = 1), all patients were assessed by clinical scores (Constant score, subjective shoulder value, American Shoulder and Elbow Surgeons [ASES] score, and Western Ontario Rotator Cuff Index [WORC] score) and underwent magnetic resonance imaging to determine RC integrity. The data were examined for age- and sex-related differences and to identify the correlation between biological potential (t = 0) and clinical/radiographic outcome (t = 1).

RESULTS

The follow-up rate for the imaging and clinical evaluation was 100%. Age, but not sex, influenced the biological tendon cell parameters at t = 0. However, there was no effect of age or sex on the clinical and radiographic results at t = 1. Furthermore, no correlation was observed between the initial biological parameters and later clinical outcomes or radiographic RC integrity. Finally, there was no significant difference between intact and nonhealed repairs in terms of the respective clinical scores.

CONCLUSION

Age, but not sex, was found to have a negative effect on RC tendon cell biology. However, neither sex nor, in particular, a higher age influenced repair outcomes after 24 months.

Interaction of age and mechanical stability on bone defect healing: an early transcriptional analysis of fracture hematoma in rat

Among other stressors, age and mechanical constraints significantly influence regeneration cascades in bone healing. Here, our aim was to identify genes and, through their functional annotation, related biological processes that are influenced by an interaction between the effects of mechanical fixation stability and age. Therefore, at day three post-osteotomy, chip-based whole-genome gene expression analyses of fracture hematoma tissue were performed for four groups of Sprague-Dawley rats with a 1.5-mm osteotomy gap in the femora with varying age (12 vs. 52 weeks - biologically challenging) and external fixator stiffness (mechanically challenging). From 31099 analysed genes, 1103 genes were differentially expressed between the six possible combinations of the four groups and from those 144 genes were identified as statistically significantly influenced by the interaction between age and fixation stability. Functional annotation of these differentially expressed genes revealed an association with extracellular space, cell migration or vasculature development. The chip-based whole-genome gene expression data was validated by q-RT-PCR at days three and seven post-osteotomy for MMP-9 and MMP-13, members of the mechanosensitive matrix metalloproteinase family and key players in cell migration and angiogenesis. Furthermore, we observed an interaction of age and mechanical stimuli in vitro on cell migration of mesenchymal stromal cells. These cells are a subpopulation of the fracture hematoma and are known to be key players in bone regeneration. In summary, these data correspond to and might explain our previously described biomechanical healing outcome after six weeks in response to fixation stiffness variation. In conclusion, our data highlight the importance of analysing the influence of risk factors of fracture healing (e.g. advanced age, suboptimal fixator stability) in combination rather than alone.

Relationship between muscle fatty infiltration and the biological characteristics and stimulation potential of tenocytes from rotator cuff tears

The healing after rotator cuff surgery is still dissatisfying, and increased muscle fatty infiltration even more impairs the healing success. To achieve sufficient healing after rotator cuff reconstructions, the use of growth factors may be one possibility. The aim of the study was to identify a possible relationship between fatty infiltration of the supraspinatus muscle and cellular biological characteristics and stimulation potential of tenocyte-like cells (TLCs). TLCs of 3 donor groups differing in grade of muscle fatty infiltration were analyzed for their cellular characteristics and were stimulated with BMP-2 or BMP-7 in a 3D scaffold culture. The cell count and potency for self-renewal were significantly decreased in TLCs from donors with high muscle fatty infiltration compared to the lower fatty infiltration groups. Cell count and collagen-I expression as well as protein synthesis were stimulated by growth factors. Interestingly, TLCs of the high fatty infiltration group exhibited a weaker stimulation potential compared to the other groups. TLCs from donors with high muscle fatty infiltration generally revealed inferior characteristics compared to cells of lower fatty infiltration groups, which may be one reason for a weaker healing potential and may represent a possible starting point for the development of future treatment options.

A tensile deformation model for in-situ dendrite/metallic glass matrix composites

In-situ dendrite/metallic glass matrix composites (MGMCs) with a composition of Ti₄₆Zr₂₀V₁₂Cu₅Be₁₇ exhibit ultimate tensile strength of 1510 MPa and fracture strain of about 7.6%. A tensile deformation model is established, based on the five-stage classification: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (yield platform), (4) plastic-plastic (work hardening), and (5) plastic-plastic (softening) stages, analogous to the tensile behavior of common carbon steels. The constitutive relations strongly elucidate the tensile deformation mechanism. In parallel, the simulation results by a finite-element method (FEM) are in good agreement with the experimental findings and theoretical calculations. The present study gives a mathematical model to clarify the work-hardening behavior of dendrites and softening of the amorphous matrix. Furthermore, the model can be employed to simulate the tensile behavior of in-situ dendrite/MGMCs.

Characteristics and stimulation potential with BMP-2 and BMP-7 of tenocyte-like cells isolated from the rotator cuff of female donors

Tendon bone healing of the rotator cuff is often associated with non-healing or recurrent defects, which seems to be influenced by the patient’s age and sex. The present study aims to examine cellular biological characteristics of tenocyte-like cells that may contribute to this impaired rotator cuff healing. Moreover, a therapeutic approach using growth factors could possibly stimulate tendon bone healing. Therefore, our second aim was to identify patient groups who would particularly benefit from growth factor stimulation. Tenocyte-like cells isolated from supraspinatus tendons of female donors younger and older than 65 years of age were characterized with respect to different cellular biological parameters, such as cell density, cell count, marker expression, collagen-I protein synthesis, and stem cell potential. Furthermore, cells of the donor groups were stimulated with BMP-2 and BMP-7 (200 and 1000 ng/ml) in 3D-culture and analyzed for cell count, marker expression and collagen-I protein synthesis. Female donors older than 65 years of age showed significantly decreased cell count and collagen-I protein synthesis compared to cells from donors younger than 65 years. Cellular biological parameters including cell count, collagen-I and –III expression, and collagen-I protein synthesis of cells from both donor groups were stimulated with BMP-2 and BMP-7. The cells from donors older than 65 years revealed a decreased stimulation potential for cell count compared to the younger group. Cells from female donors older than 65 years of age showed inferior cellular biological characteristics. This may be one reason for a weaker healing potential observed in older female patients and should be taken into consideration for tendon bone healing of the rotator cuff.

Origin of intermittent plastic flow and instability of shear band sliding in bulk metallic glasses

Intermittent or serrated plastic flow is widely observed in the deformation of bulk metallic glasses (BMGs) or other disordered solids at low temperatures. However, the underlying physical process responsible for the phenomena is still poorly understood. Here, we give an interpretation of the serrated flow behavior in BMGs by relating the atomic-scale deformation with the macroscopic shear band behavior. Our theoretical analysis shows that serrated flow in fact arises from an intrinsic dynamic instability of the shear band sliding, which is determined by a critical stiffness parameter in stick-slip dynamics. Based on this, the transition from serrated to nonserrated flow with the strain rate or the temperature is well predicted and the effects of various extrinsic and intrinsic factors on shear band stability can be quantitatively analyzed in BMGs. Our results, which are verified by a series of compression tests on various BMGs, provide key ingredients to fundamentally understand serrated flow and may bridge the gap between the atomic-scale physics and the larger-scale shear band dynamics governing the deformation of BMGs.

Histopathologic evaluation of passive stabilizers in shoulder instability

BACKGROUND

The macroscopic pathomorphology in recurrent shoulder instability has been described. However, less is known regarding the histopathologic details of the affected structures. This study evaluates different histopathologic stages of shoulder instability by assessing biopsy specimens of static stabilizers for possible correlations with clinical parameters. Our hypothesis was that clinical parameters of shoulder instability correlate with histopathologic findings.

MATERIALS AND METHODS

Passive shoulder stabilizers (labrum, anterior bundle of the inferior glenohumeral ligament) were biopsied during arthroscopic shoulder stabilization. Samples were submitted to immunohistochemistry, in situ hybridization, and blinded evaluation. Clinical data, comprising age (<30 years or ≥30 years), total number of dislocations (1, 2-3, or >3), and period since initial dislocation (<6 months, 6 months to 6 years, or >6 years), were tested for statistical correlation with the following histopathologic parameters: inflammation, lipomatous changes, vascular proliferation, tissue fragmentation, and cellularity.

RESULTS

Standardized biopsies were performed in 30 consecutive patients (4 women and 26 men; mean age, 32.6 years) with anterior shoulder instability. Microscopic evaluation showed only small variations in histologic changes among all samples. Only limited variations in cell density, matrix swelling, and collagen fiber disruptions were found. Immunohistochemical analysis showed a similar expression of decorin in all samples. Clinical parameters (age, total number of dislocations, and period since initial dislocation) were statistically independent from histopathologic parameters (inflammation, lipomatous changes, vascular proliferation, tissue fragmentation, and cellularity). No correlation was found in patients with 1 dislocation versus those with more than 1 dislocation.

CONCLUSIONS

In contrast to macroscopic findings among different grades of shoulder instability, this study detected no correlation between clinical items (age, total number of dislocations, and period since initial dislocation) and histopathologic parameters. These clinical items seem to be independent from the tissue status of static stabilizers of the shoulder.

[Value of one-stage surgical treatment of diffuse peritonitis (relaparotomy on demand): a single-center analysis]

BACKGROUND

Despite modern surgical and intensive-care concepts, diffuse peritonitis remains a major source of high morbidity and mortality. The aim of this study was to critically evaluate the value of relaparotomy on demand (ROD) for patients with diffuse peritonitis.

PATIENTS AND RESULTS

In a retrospective analysis, the clinical course of 231 patients with diffuse peritonitis was analysed. The mean Mannheim Peritonitis Index (MPI) was 25.3. Overall lethality in this cohort was 14.3 %. In 214 patients, source control was successful during the index operation, and these patients were treated according to an on-demand strategy. For 178 of these patients, there was no demand for a relaparotomy, whereas 36 of these patients required further surgical interventions. Lethality for these subgroups was 9 % (no relaparotomy) and 27 % (relaparotomy), respectively.

CONCLUSIONS

This retrospective analysis confirms that an on-demand strategy is reasonable and feasible after successful source control and lavage. However, it still remains of clinical importance to identify parameters that may assist in selecting those patients who require a relaparotomy.

Arthroscopic single-row modified mason-allen repair versus double-row suture bridge reconstruction for supraspinatus tendon tears: a matched-pair analysis

BACKGROUND

Arthroscopic double-row fixation of supraspinatus tendon tears compared with single-row techniques is still a matter of debate.

HYPOTHESIS

Arthroscopic double-row rotator cuff repair using the suture bridge technique provides better clinical results and lower retear rates than does single-row repair using a modified Mason-Allen stitch technique.

STUDY DESIGN

Cohort study; Level of evidence 3.

METHODS

Forty patients underwent either an arthroscopic single-row modified Mason-Allen stitch (SR) (n = 20; mean age ± SD, 61.5 ± 7.4 y) or a modified suture bridge double-row repair (DR) (n = 20; age, 61.2 ± 7.5 y). The anteroposterior extension was classified as Bateman I in 10% and Bateman II in 90% of patients in the SR group and as Bateman II in 80% and Bateman III in 20% of patients in the DR group. Patients were matched for sex and age. The subjective shoulder value (SSV), Constant-Murley score (CS), and Western Ontario Rotator Cuff Index (WORC) were used for clinical follow-up. Furthermore, MRI scans were conducted for analysis of tendon integrity, muscle atrophy, and fatty infiltration via semiquantitative signal intensity analysis. In addition, re-defect patterns were evaluated.

RESULTS

The mean follow-up time in the SR group was 16.8 ± 4.6 months. The mean SSV was 91.0% ± 8.8%, mean CS was 82.2 ± 8.1 (contralateral side, 88.8 ± 5.3), and mean WORC score was 96.5% ± 3.2%. The mean follow-up time in the DR group was 23.4 ± 2.9 months, with patients achieving scores of 92.9% ± 9.6% for the SSV, 77.0 ± 8.6 for the CS (contralateral side, 76.7 ± 17.1), and 90.7% ± 12.6% for the WORC (P > .05). No significant differences were detected in the clinical outcome between groups. Tendon integrity was as follows. Type 1, none in either group; type 2, 4 SR and 5 DR; type 3, 9 SR and 10 DR; type 4, 3 SR and 3 DR; and type 5, 3 SR and 2 DR. The failure rate was 31.6% (n = 6) in the SR group and 25% (n = 5) in the DR group (P > .05). No significant differences were obtained for muscular atrophy or fatty degeneration (SR group, 0.94 ± 0.16; DR group, 1.15 ± 0.5) (P > .05). Re-defects revealed lateral cuff failure in 83.3% of SR patients in contrast to patients treated with DR techniques. The re-defect pattern was medial cuff failure in 80% of the patients.

CONCLUSION

The clinical results after modified Mason-Allen single-row versus double-mattress suture bridge technique did not demonstrate significant differences in a matched patient cohort. Concerning the failure mode, single- and double-row techniques seem to demonstrate different re-defect patterns.

Influence of statins locally applied from orthopedic implants on osseous integration

Background

Simvastatin increases the expression of bone morphogenetic protein 2 (BMP-2) in osteoblasts, therefore it is important to investigate the influence of statins on bone formation, fracture healing and implant integration. The aim of the present study was to investigate the effect of Simvastatin, locally applied from intramedullary coated and bioactive implants, on bone integration using biomechanical and histomorphometrical analyses.

Methods

Eighty rats received retrograde nailing of the femur with titanium implants: uncoated vs. polymer-only (poly(D,L-lactide)) vs. polymer plus drug coated (either Simvastatin low- or high dosed; “SIM low/ high”). Femurs were harvested after 56 days for radiographic and histomorphometric or biomechanical analysis (push-out).

Results

Radiographic analysis revealed no pathological findings for animals of the control and SIM low dose group. However, n=2/10 animals of the SIM high group showed osteolysis next to the implant without evidence of bacterial infection determined by microbiological analysis. Biomechanical results showed a significant decrease in fixation strength for SIM high coated implants vs. the control groups (uncoated and PDLLA). Histomorphometry revealed a significantly reduced total as well as direct bone/implant contact for SIM high- implants vs. controls (uncoated and PDLLA-groups). Total contact was reduced for SIM low vs. uncoated controls. Significantly reduced new bone formation was measured around SIM high coated implants vs. both control groups.

Conclusions

This animal study suggests impaired implant integration with local application of Simvastatin from intramedullary titanium implants after 8 weeks when compared to uncoated or carrier-only coated controls.

Influence of age on the cell biological characteristics and the stimulation potential of male human tenocyte-like cells

The incidence of rotator cuff tears and recurrent defects positively correlate with patient age. However, this observation has never been analysed at the cellular level. The present study aims to better understand this correlation by investigating cellular characteristics of rotator cuff tenocytes of different age groups. Additionally, previous studies reported on stimulating effects of Bone Morphogenetic Protein (BMP) -2 and BMP-7 on tenocytes. Thus, the second aim was to investigate, whether the stimulation potential of tenocytes demonstrates age-related differences. Tenocyte-like cells from supraspinatus tendons of young and aged patients were analysed for the following cell biological characteristics: cell density, cell growth, marker expression, collagen-I protein synthesis, stem cell phenotype, potential for multipotent differentiation and self-renewal. To analyse the stimulation potential, cells were treated with BMP-2 and BMP-7 in 2D-/3D-cultures. Measured parameters included cell activity, marker expression and collagen-I protein synthesis. An effect of age was seen for cell growth and stem cell potential but not on extracellular matrix level. Cells from both groups responded to BMP-7 by increasing cell activity, collagen-I expression and protein synthesis. BMP-2 led to smaller increases in these parameters when compared to BMP-7. In general, 3D-cultivation improved the stimulation compared to 2D-culture. The cell biological characteristics of tenocyte-like cells, considered important for successful restoration of the tendon-bone unit, were inferior in elderly donors. This may help explain higher rates of recurrent defects seen in elderly patients. Regarding the stimulation potential, on a cellular level young and aged patients may benefit from biological augmentation with BMPs.

BMP-2 and BMP-7 affect human rotator cuff tendon cells in vitro

BACKGROUND

Rotator cuff repair is prone to incomplete regeneration. To explore biological improvements of tendon-bone healing, it was the aim of this study to investigate the influence of growth factors bone morphogenetic protein (BMP)-2 and BMP-7 on tenocyte cell activity and matrix gene expression and production. A beneficial effect of these factors would be promising to improve tendon-bone healing in vivo.

METHODS

Tenocyte-like cells were isolated from human rotator cuff tissue samples (supraspinatus and long head of biceps tendon) and incubated with BMP-2 (100-1000 ng/mL) and BMP-7 (100-2000 ng/mL), both alone and in combination. At days 0, 3, and 6, cell activity was assessed. At day 6, collagen type I production and the expression of several tendon-, bone-, and cartilage-related markers (collagen types I-III, osteocalcin, scleraxis) were evaluated.

RESULTS

Dose-dependent effects of both investigated growth factors on tenocyte-like cells were observed. Application of BMP-2 increased collagen type I production significantly but its expression only slightly. Cell activity was decreased in higher doses over time. For BMP-7, a significant increase in collagen type I production and expression, as well as increased cell activity, was observed. The addition of both factors resulted in decreased parameters when compared with BMP-7 alone. The expression of collagen types II and III, osteocalcin, and scleraxis was not significantly affected by application of BMPs.

CONCLUSION

Besides the well-known effects of BMP-2 and BMP-7 on osteoblasts, this study describes further effects on rotator cuff tendon cell biology. Both tissue types potentially need to be addressed to improve tendon-bone healing of the rotator cuff.

Effect of local zoledronate on implant osseointegration in a rat model

Background

An implant coating with poly(D, L-lactide) (PDLLA) releasing incorporated Zoledronic acid (ZOL) has already proven to positively effect osteoblasts, to inhibit osteoclasts and to accelerate fracture healing. Aim of this study was to investigate the release kinetics of the chosen coating and the effect of different concentrations of ZOL locally released from this coating on the osseointegration of implants.

Methods

For release kinetics the release of C14-labled ZOL out of the coating was monitored over a period of six weeks in vitro. For testing the osseointegration, titanium Kirschner wires were implanted into the medullary canal of right femurs of 100 Sprague Dawley rats. The animals were divided into five groups receiving implants either uncoated or coated with PDLLA, PDLLA/ZOL low (1.2% w/w) or PDLLA/ZOL high (2% w/w). Additionally, a group with uncoated implants received ZOL intravenously (i.v.). After 56 days animals were sacrificed, femurs dissected and either strength of fixation or histological bone/implant contacts and newly formed bone around the implants were determined.

Results

Release kinetics revealed an initial peak in the release of C14-ZOL with a slight further progression over the following weeks. There was no significant enhancement of osseointegration for both groups who received ZOL-coated implants or ZOL i.v. compared to the controls in biomechanical or histological analyses, except for a significant raise in strength of fixation of ZOL i.v. versus PDLLA.

Conclusions

Even though the investigated local ZOL application did not enhance the osseointegration of the implant, the findings might support its application in fracture treatment, since fracture stabilization devices are often explanted after consolidation.

Biomechanical comparison of four double-row speed-bridging rotator cuff repair techniques with or without medial or lateral row enhancement

BACKGROUND

Biomechanical comparison of four different Speed-Bridge configurations with or without medial or lateral row reinforcement. Reinforcement of the knotless Speed-Bridge double-row repair technique with additional medial mattress- or lateral single-stitches was hypothesized to improve biomechanical repair stability at time zero.

METHODS

Controlled laboratory study: In 36 porcine fresh-frozen shoulders, the infraspinatus tendons were dissected and shoulders were randomized to four groups: (1) Speed-Bridge technique with single tendon perforation per anchor (STP); (2) Speed-Bridge technique with double tendon perforation per anchor (DTP); (3) Speed-Bridge technique with medial mattress-stitch reinforcement (MMS); (4) Speed-Bridge technique with lateral single-stitch reinforcement (LSS). All repairs were cyclically loaded from 10-60 N up to 10-200 N (20 N stepwise increase) using a material testing device. Forces at 3 and 5 mm gap formation, mode of failure and maximum load to failure were recorded.

RESULTS

The MMS-technique with double tendon perforation showed significantly higher ultimate tensile strength (338.9 ± 90.0 N) than DTP (228.3 ± 99.9 N), LSS (188.9 ± 62.5 N) and STP-technique (122.2 ± 33.8 N). Furthermore, the MMS-technique provided increased maximal force resistance until 3 and 5 mm gap formation (3 mm: 77.8 ± 18.6 N; 5 mm: 113.3 ± 36.1 N) compared with LSS, DTP and STP (P < 0.05 for each 3 and 5 mm gap formation). Failure mode was medial row defect by tendon sawing first, then laterally. No anchor pullout occurred.

CONCLUSION

Double tendon perforation per anchor and additional medial mattress stitches significantly enhance biomechanical construct stability at time zero in this ex vivo model when compared with the all-knotless Speed-Bridge rotator cuff repair.

Subjective and objective outcome after revision arthroscopic stabilization for recurrent anterior instability versus initial shoulder stabilization

BACKGROUND

The value of arthroscopic revision shoulder stabilization after failed instability repair is still a matter of debate.

HYPOTHESIS

Arthroscopic revision shoulder stabilization using suture anchors provides equivalent subjective and objective results compared with initial arthroscopic instability repair.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Twenty consecutive patients who underwent arthroscopic revision shoulder stabilization using suture anchors (group 2) were matched for age, gender, and handedness (dominant or nondominant) with 20 patients who had initial arthroscopic instability repair using the same technique (group 1). At the time of follow-up, a complete physical examination of both shoulders and evaluation with the Rowe score, Walch-Duplay score, Melbourne Instability Shoulder Score, Western Ontario Shoulder Instability Index, and the Subjective Shoulder Value were performed. In addition, standard radiographs (true AP and axillary views) were taken to evaluate signs of osteoarthritis.

RESULTS

After a minimum follow-up of 24 months, no recurrent dislocations were observed in either group. The apprehension sign was positive in 2 cases of revision surgery (0 vs 2; P > .05). No significant differences in the Rowe score (89 vs 81.8 points) were found between groups 1 and 2 (P > .05). However, group 2 revealed significantly lower scores in the Walch-Duplay score (85.3 vs 75.5 points), Melbourne Instability Shoulder Score (90.2 vs 73.7 points), Western Ontario Shoulder Instability Index (89.8% vs 68.9%), and Subjective Shoulder Value (91.8% vs 69.2%) (P < .05). Signs of instability arthropathy were found more often in patients with arthroscopic revision surgery (2 vs 5; P > .05).

CONCLUSION

Arthroscopic revision shoulder stabilization is associated with a lower subjective outcome compared with initial arthroscopic stabilization. The objective results found in this study may overestimate the clinical outcome in this patient population.

Biomechanical comparison of 4 double-row suture-bridging rotator cuff repair techniques using different medial-row configurations

PURPOSE

Biomechanical comparison of different suture-bridge configurations of the medial row with respect to initial construct stability (time 0, porcine model).

METHODS

In 40 porcine fresh-frozen shoulders, the infraspinatus tendons were dissected from their insertions. All specimens were operated on by use of the suture-bridge technique, only differing in terms of the medial-row suture-grasping configuration, and randomized into 4 groups: (1) single-mattress (SM) technique, (2) double-mattress (DM) technique, (3) cross-stitch (CS) technique, and (4) double-pulley (DP) technique. Identical suture anchors were used for all specimens (medial: Bio-Corkscrew FT 5.5 [Arthrex, Naples, FL]; lateral: Bio-PushLock 3.5 [Arthrex]). All repairs were cyclically loaded from 10 to 60 N until 10 to 200 N (20-N stepwise increase after 50 cycles each) with a material testing machine. Forces at 3 and 5 mm of gap formation, mode of failure, and maximum load to failure were recorded.

RESULTS

The DM technique had the highest ultimate tensile strength (368.6 ± 99.5 N) compared with the DP (248.4 ± 122.7 N), SM (204.3 ± 90 N), and CS (184.9 ± 63.8 N) techniques (P = .004). The DM technique provided maximal force resistance until 3 and 5 mm of gap formation (90.0 ± 18.1 N and 128.0 ± 32.3 N, respectively) compared with the CS (72 ± 8.9 N and 108 ± 20.2 N, respectively), SM (66.0 ± 8.9 N and 90.0 ± 26.9 N, respectively), and DP (62.2 ± 6.2 N and 71 ± 13.2 N, respectively) techniques (P < .05 for each 3 and 5 mm of gap formation). The main failure mode was suture cutting through the tendon.

CONCLUSIONS

Comparing the 4 different suture-bridge techniques, we found that modified application of suture-bridge repair with double medial mattress stitches significantly enhanced biomechanical construct stability at time 0 in this porcine ex vivo model.

CLINICAL RELEVANCE

This technique increases initial stability and resistance to suture cutting through the rotator cuff tendon after arthroscopic suture-bridge repair.

Characterization of tendon cell cultures of the human rotator cuff

Rotator cuff tears are common soft tissue injuries of the musculoskeletal system that heal by formation of repair tissue and may lead to high retear rates and joint dysfunction. In particular, tissue from chronic, large tendon tears is of such degenerative nature that it may be prone to retear after surgical repair. Besides several biomechanical approaches, biologically based strategies such as application of growth factors may be promising for increasing cell activity and production of extracellular tendon matrix at the tendon-to-bone unit. As a precondition for subsequent experimental growth factor application, the aim of the present study was to establish and characterize a human rotator cuff tendon cell culture. Long head biceps (LHB)- and supraspinatus muscle (SSP)- tendon samples from donor patients undergoing shoulder surgery were cultivated and examined at the RNA level for expression of collagen type-I, -II and -III, biglycan, decorin, tenascin-C, aggrecan, osteocalcin, tenomodulin and scleraxis (by Real-time PCR). Finally, results were compared to chondrocytes and osteoblasts as control cells. An expression pattern was found which may reflect a human rotator cuff tenocyte-like cell culture. Both SSP and LHB tenocyte-like cells differed from chondrocyte cell cultures in terms of reduced expression of collagen type-II (p<or=0.05) and decorin while higher levels of collagen type-I were seen (p<or=0.05). With respect to osteoblasts, tenocyte-like cells expressed lower levels of osteocalcin (p<or=0.05) as well as tenascin C, biglycan and collagen type-III. Expression of scleraxis, tenomodulin and aggrecan was similar between all cell types. This study represents a characterization of tenocyte-like cells from the human rotator cuff as close as possible. It helps analyzing their biological properties and allows further studies to improve production of tendon matrix and osteofibroblastic integration at the tendon-bone unit following tendon repair.

Transformation-mediated ductility in CuZr-based bulk metallic glasses

Bulk metallic glasses (BMGs) generally fail in a brittle manner under uniaxial, quasistatic loading at room temperature. The lack of plastic strain is a consequence of shear softening, a phenomenon that originates from shear-induced dilation that causes plastic strain to be highly localized in shear bands. So far, significant tensile ductility has been reported only for microscopic samples of around 100 nm (ref. 4) as well as for high strain rates, and so far no mechanisms are known, which could lead to work hardening and ductility in quasistatic tension in macroscopic BMG samples. In the present work we developed CuZr-based BMGs, which polymorphically precipitate nanocrystals during tensile deformation and subsequently these nanocrystals undergo twinning. The formation of such structural heterogeneities hampers shear band generation and results in macroscopically detectable plastic strain and work hardening. The precipitation of nanocrystals and their subsequent twinning can be understood in terms of a deformation-induced softening of the instantaneous shear modulus. This unique deformation mechanism is believed to be not just limited to CuZr-based BMGs but also to promote ductility in other BMGs.

Simvastatin locally applied from a biodegradable coating of osteosynthetic implants improves fracture healing comparable to BMP-2 application

Many clinical and experimental investigations address the influence of statins on bone formation and fracture healing. Simvastatin was shown to increase the expression of Bone morphogenetic protein (BMP-2), which is one of the most potent growth factors targeting bone formation. In this study, the effect of simvastatin locally applied from a bioactive polymer coating of implants on fracture healing was investigated. A closed fracture of the right tibia of 5-month-old Sprague-Dawley rats was performed. Intramedullary stabilization was achieved with uncoated vs. polymer-only coated vs. polymer plus drug coated titanium Kirschner wires. Test substances (either simvastatin low- or high dosed or BMP-2) were incorporated into a biodegradable layer of poly(d,l-lactide). Tibiae were harvested after 28 or 42 days, respectively and underwent biomechanical testing (torsional stiffness and maximum load) and histomorphometric analysis. Radiographic results demonstrated progressed callus consolidation in the BMP-2- and simvastatin-treated groups compared to the uncoated group at both timepoints. The simvastatin-high-dosed group revealed an increased torsional stiffness and significantly elevated maximum load (d 28) compared to control group as well as a significant increase in both parameters at d 42. BMP-2-treated animals showed significantly elevated maximum load and stiffness at the early timepoint and elevated torsional stiffness after d 42. The histomorphometric analysis revealed a significantly decreased cartilage area for BMP-2 treated animals at d 28. Even though an increase of mineralized areas among periosteal callus was found at d 42 for simvastatin-high as well as BMP-2 treated animals, no significant difference could be detected at both timepoints compared to the uncoated group. However, simvastatin-high treated animals revealed significantly reduced cartilage areas within the periosteal callus at d 42. The present study revealed a dose-dependent effect and improved fracture healing under local application of simvastatin. Biomechanical, radiographic and histomorphometric properties showed comparable results to BMP-2- treated animals in this study.

Arthroscopically assisted coracoclavicular ligament reconstruction for chronic acromioclavicular joint instability

The treatment of symptomatic chronic acromioclavicular joint dislocations can be challenging. Different surgical procedures have been described in the literature. We present an arthroscopically assisted stabilization using a gracilis tendon transclavicular-transcoracoid loop technique augmented with a Tight-Rope (Arthrex, Naples, FL, USA). In contrast to the classic Weaver-Dunn procedures this technique is designed to stabilize the acromioclavicular joint by recreating the anatomy of the coracoclavicular ligaments via a minimal invasive approach.

CD137 expression in tumor vessel walls. High correlation with malignant tumors

CD137 (ILA/4-1BB), a member of the tumor necrosis factor receptor family, and its ligand are expressed on activated T lymphocytes and on antigen-presenting cells, respectively. Via bidirectional signal transduction, this receptor-ligand system regulates the activation, proliferation, and survival of T and B lymphocytes and monocytes. We used immunohistochemical studies on human tissue samples to determine in vivo CD137 expression in nonimmune tissue samples. Strong CD137 expression was found in blood vessel walls, on the endothelial layer, and on the vascular smooth muscle cells. But in 32 healthy tissue samples examined, none contained CD137-positive vessels. Also, in benign tumors (2/14) and in inflammatory tissues (2/9) only a minority had CD137-expressing vessels. However, malignant tumors had a significantly enhanced frequency of CD137-expressing blood vessels (11/34).

CD137-induced apoptosis is independent of CD95

CD95 (APO-1/Fas) and CD137 (ILA/4-1BB) are members of the tumour necrosis factor receptor family, and both are involved in induction of apoptosis in lymphocytes. Contrary to the case of CD95, apoptosis by CD137 is caused by cross-linking of the respective ligand rather than the receptor. Nothing is known so far about the mechanism of CD137-induced cell death. Here, we show that immobilized CD137 protein induces expression of CD95 in resting primary T and B lymphocytes. However, induction of apoptosis by CD137 is independent of CD95, because: (1) antagonistic anti-CD95 antibody fragments do not block CD137-induced apoptosis; and (2) CD137, but not anti-CD95, can induce apoptosis in resting lymphocytes.

Decentralized lab testing. A collaborative approach to point of care testing

What is involved in setting up and managing a decentralized laboratory testing program at a hospital? What elements are involved in making such a program a success? Multidepartmental and multidisciplinary cooperation and communication are the keys to implementing a cost-effective, user-friendly system that assures quality patient care and operator competence.

The Flash Pattern of Photosynthetic Oxygen Evolution after Treatment with Low Concentrations of Hydroxylamine as a Function of the Previous S1/S0-Ratio Further Evidence that NH2OH Reduces the Water Oxidizing Complex in the Dark

Flash induced oxygen evolution patterns of isolated PS II complexes from the cyanobacterium Synechococcus were measured with a Joliot-type electrode. By suitable preflash and dark adaptation procedures, samples were prepared in the state S1 (100%), as well as enriched in S0 (60% S0, 40% S,). After treatment with low concentrations of NH2OH (≤ 100 μм), the two flash patterns were identical. This is further evidence for a reduction of the water oxidizing complex by hydroxylamine in the dark. Two reduced states (S-1 and S-2) below S0 are formed by this reduction.

Hepatoma induction in the rat by the subcutaneous administration of powdered 3'-methyl-p-dimethylaminoazobenzene

A relatively safe and simple procedure was developed for the induction of hepatomas in the rat by the s.c. administration of powdered 3'-methyl-p-dimethylaminoazobenzene.