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Purpose: A satisfactory clinical outcome in dental implant treatment relies on primary stability for immediate load bearing. While the geometric design of an implant contributes to mechanical stability, the nature of the implant surface itself is also critically important. Biomechanical and microcomputerized tomographic evaluation of implant osseointegration was performed to compare alternative structural, chemical and biochemical, and/or pharmaceutical surface treatments applied to an identical established implant design. Materials and Methods: Dental implants with the same geometry but with 6 different surface treatments were tested in vivo in a sheep model (pelvis). Peri-implant bone density and removal torque were compared at2, 4, and 8 weeks after implantation. Implant surfaces tested were: sandblasted and acid-etched titanium (Ti), sandblasted and etched zirconia, Ti coated with calcium phosphate (CaP), Ti modified via anodic plasma-chemical treatment (APC), bisphosphonatecoated Ti (Ti + Bisphos), and Ti coated with collagen containing chondroitin sulfate (CS). Results: All dental implants were well integrated at the time of sacrifice. There were no significant differences observed in peri-implant bone density between implant groups. After 8 weeks of healing, removal torque values for Ti, Ti + Cap, Ti + Bisphos, and Ti + collagen + CS were significantly higher than those for zirconia and Ti +APC. Conclusions: Whereas the sandblasted/acid-etched Ti implant can still be considered the reference standard surface for dental implants, functional surface modifications such as bisphosphonate or collagen coating seem to enhance early peri-implant bone formation and should be studied further. [ABSTRACT FROM AUTHOR]

Introduction: Different approaches for disc regeneration are currently under investigation. Beside gene therapy and tissue engineering techniques, the application of growth and differentiation factors own promising potential. Studies using reduced intervertebral disc models, such as cell or tissue fragment cultures, have limited validity and show controversial results depending on the employed experimental model. Therefore, the goal of the current study was to investigate the effect of BMP-2 and TGF-β3 on intervertebral disc degeneration using an in vitro full-organ disc/endplate culture system.Materials and Methods: Intervertebral rabbit disc explants were cultured in the presence of 1 μg/ml BMP-2 or TGF-β3 for 21 days in DMEM/F12 media. Nucleus and annulus were analyzed for gene expression of collagen type I and II (Col I/II), aggrecan, collagenases (MMP-1/MMP-13) with RT-qPCR, histological changes with bone and proteoglycan-specific staining (von Kossa, toluidine blue) and differences in cellularity (DNA) and proteoglycan content (alcian blue binding assay).Results: The results demonstrate that disc proteoglycan concentration decreased with time in the TGF-β3 and BMP-2 groups. In the annulus fibrosus (AF), TGF-β3 and BMP-2 resulted in an up-regulation of Col I and type II, and of aggrecan gene expression. In contrast, MMP genes were inhibited. In the nucleus, the growth factors decreased gene expression of aggrecan and spontaneous Col I up-regulation was inhibited by TGF-β3, whereas expression of Col II was decreased with BMP-2. There was no effect on expression of MMP-1 and MMP-13 for most sampling points. However, TGF-β3 and BMP-2 induced ossification of the AF was demonstrated by histology.Conclusion: It can be concluded that both growth factors, at the tested concentrations, may not be suitable to regenerate the whole intervertebral disc organ but they are interesting candidates for being injected alone or in combination into a painful intervertebral disc to induce osseous fusion (spondylodesis). [ABSTRACT FROM AUTHOR]

Loading is important to maintain the balance of matrix turnover in the intervertebral disc (IVD). Daily cyclic diurnal assists in the transport of large soluble factors across the IVD and its surrounding circulation and applies direct and indirect stimulus to disc cells. Acute mechanical injury and accumulated overloading, however, could induce disc degeneration. Recently, there is more information available on how cyclic loading, especially axial compression and hydrostatic pressure, affects IVD cell biology. This review summarises recent studies on the response of the IVD and stem cells to applied cyclic compression and hydrostatic pressure. These studies investigate the possible role of loading in the initiation and progression of disc degeneration as well as quantifying a physiological loading condition for the study of disc degeneration biological therapy. Subsequently, a possible physiological/beneficial loading range is proposed. This physiological/beneficial loading could provide insight into how to design loading regimes in specific system for the testing of various biological therapies such as cell therapy, chemical therapy or tissue engineering constructs to achieve a better final outcome. In addition, the parameter space of 'physiological' loading may also be an important factor for the differentiation of stem cells towards most ideally 'discogenic' cells for tissue engineering purpose. [ABSTRACT FROM AUTHOR]

The capacity of mesenchymal stem cells (MSCs) to differentiate into intervertebral disc (IVD)-like cells has been well described, but their ability to modulate the inflammatory processes in the IVD remains unclear. We found that tissue obtained by discectomy of degenerated and post-traumatic IVD contains significant amounts of IgG antibodies, a sign of lymphocyte infiltration. Further we investigated whether MSCs in vitro, which were characterized for their multilineage differentiation potential and may have immunomodulatory effects on IVD fragments. IVD fragments were co-cultured in contact with peripheral blood lymphocytes (PBLs) and MSCs, and as functional controls we used contact co-cultures of PBLs stimulated with pokeweed mitogen (2.5 μg/mL) and MSCs. The time course of lymphocyte proliferation (Alamar Blue), IgG (ELISA) and gene expression (RT-PCR) of anti-inflammatory cytokines (TGF-β1, IL-10) by MSCs and pro-inflammatory molecules (IL-1α, IL-1β and TNF-α) by the IVD fragments were analyzed. Depending on the response to the presence of MSCs, the IVD fragments (n = 13) were divided in two groups: responders (n = 9), where inflammation was inhibited by MSCs and non-responders (n = 4), where MSCs did not decrease inflammation. At 1 week in co-culture, MSCs reduced significantly the IgG production in the IVD responders group to 69% and PBLs proliferation to 57% of the control. MSCs expression of the anti-inflammatory TGF-β1 increased with time, while IL-10 was expressed only at day 1. IVD gene expression of TNF-α decreased constantly, whereas IL-1α and IL-1β expression increased. In conclusion, these data suggest that MSCs may modulate disc-specific inflammatory and pain status and aid regeneration of the host tissue. [ABSTRACT FROM AUTHOR]

To investigate how psychosocial resources may improve well-being for older adults, this study explored the relationship among questionnaire measures of optimism, social support and perceptions of control in predicting subjective well-being (measured with the positive affect subscale of the Affect Balance Scale) (Bradburn, 1969) and psychological well-being (measured with the purpose in life scale of the Ryff Psychological Well-being scales) (Ryff, Lee, Essex, & Schmutte, 1994) among older adults. The potential mediating roles of perceived social support and perception of control were also explored. Participants were 225 adults aged from 65 to 94 years. Optimism was found to be a predictor of both subjective and psychological well-being, and perceived social support was found to mediate the relationship between optimism and subjective well-being, but not psychological well-being. In contrast, perception of control was found to mediate the relationship between optimism and psychological well-being, but not subjective well-being. Longitudinal research is needed to confirm these pathways. [ABSTRACT FROM AUTHOR]

Vertebral cement augmentation can restore the stiffness and strength of a fractured vertebra and relieve chronic pain. Previous finite element analysis, biomechanical tests and clinical studies have indirectly associated new adjacent vertebral fractures following augmentation to altered loading. The aim of this repeated measures in situ biomechanical study was to determine the changes in the adjacent and augmented endplate deformation following cement augmentation of human cadaveric functional spine units (FSU) using micro-computed tomography (micro-CT). The surrounding soft tissue and posterior elements of 22 cadaveric human FSU were removed. FSU were assigned to two groups, control (n = 8) (loaded on day 1 and day 2) and augmented (n = 14) (loaded on day 1, augmented 20% cement fill, and loaded on day 2). The augmented group was further subdivided into a prophylactic augmentation group (n = 9), and vertebrae which spontaneously fractured during loading on day 1 (n = 5). The FSU were axially loaded (200, 1,000, 1,500-2,000 N) within a custom made radiolucent, saline filled loading device. At each loading step, FSUs were scanned using the micro-CT. Endplate heights were determined using custom software. No significant increase in endplate deformation following cement augmentation was noted for the adjacent endplate (P > 0.05). The deformation of the augmented endplate was significantly reduced following cement augmentation for both the prophylactic and fracture group (P < 0.05, P < 0.01, respectively). Endplate deformation of the controls showed no statistically significant differences between loading on day 1 and day 2. A linear relationship was noted between the applied compressive load and endplate deflection (R (2) = 0.58). Evidence of significant endplate deformation differences between unaugmented and augmented FSU, while evident for the augmented endplate, was not present for the adjacent endplate. This non-invasive micro-CT method may also be useful to investigate endplate failure, and parameters that predict vertebral failure. [ABSTRACT FROM AUTHOR]

There is a major controversy whether spinal trauma with vertebral endplate fractures can result in post-traumatic disc degeneration. Intervertebral discs, which are adjacent to burst endplates, are frequently removed and an intercorporal spondylodesis is performed. In any case, the biological effects within the discs following endplate fractures are poorly elucidated to date. The aim of our investigations was therefore to establish a novel disc/endplate trauma culture model to reproducibly induce endplate fractures and investigate concurrent disc changes in vitro. This model is based on a full-organ disc/endplate culture system, which has been validated by the authors before. Intervertebral disc/endplate specimens were isolated from Burgundy rabbits and cultured in standard media (DMEM/F12, 10%FCS). Burst endplate fractures were induced in half of the specimens with a custom-made fracture device and subsequently cultured for 9 days. The biological effects such as necrotic or apoptotic cell death and the expression of pro-apoptotic genes and other genes involved in organ degeneration, e.g. matrix metalloproteinases (MMPs) were analyzed. Cell damage was assessed by quantification of the lactate dehydrogenase (LDH) activity in the supernatant. The expression of genes involved in the cellular apoptotic pathway (caspase 3) and the pro-apoptotic proteins FasL and TNF-alpha were monitored. The results demonstrate that LDH levels increased significantly post trauma compared to the control and remained elevated for 3 days. Furthermore, a constant up-regulation of the caspase 3 gene in both disc compartments was present. The pro-apoptotic proteins FasL and TNF-alpha were up regulated predominantly in the nucleus whereas the MMP-1 and -13 transcripts (collagenases) were increased in both disc structures. From this study we can conclude that endplate burst fractures result in both necrotic and apoptotic cell death in nucleus and annulus tissue. Moreover, FasL and TNF-alpha expression by nucleus cells may lead to continued apoptosis induced by Fas- and TNF-alpha receptor bearing cells. In addition TNF-alpha over-expression has potentially deleterious effects on disc metabolism such as over-expression of matrix proteinases. Taken together, the short term biological response of the disc following endplate fracture exhibits characteristics, which may initiate the degeneration of the organ. [ABSTRACT FROM AUTHOR]

BACKGROUND: The biomechanical role of the posterior spinal ligaments for spinal stability has been stated in previous studies. The investigation of the viscoelastic properties of human lumbar spinal ligaments is essential for the understanding of physiological differences between healthy and degenerated tissues. The stress-relaxation behavior of biological tissues is commonly described with the quasi-linear viscoelastic model of Fung, which assumes that the stress-relaxation response is independent of the applied strain. The goal of this study was to investigate the stress-relaxation response of ovine posterior spinal ligaments at different elongations to verify the above-mentioned hypothesis. METHODS: Twenty-four ovine lumbar spinal segments, consisting of only the supraspinous and interspinous ligaments and adjoining spinous processes, were elongated uniaxially to different strain levels within the physiological elastic region (5-20%). The experimental data were described with a non-linear viscoelastic model: the modified superposition method of Findley. FINDINGS: A linear dependency of the relaxation rate to the applied strains was observed on intact segments, when both ligaments were considered, as well as on each individual ligament. This result can be applied to the human spinal ligaments, due to similarities observed between the sheep and human spinal segment under physiological loading. INTERPRETATION: The non-linear viscoelastic modified superposition method of Findley is an appropriate model for describing the viscoelastic properties of lumbar spinal ligaments in vitro due to its ability to address variation in applied strain during the force relaxation measurements. [ABSTRACT FROM AUTHOR]

Background: Numerous physical diagnostic shoulder tests have been established to determine the presence of rotator cuff tears and to identify the affected muscles. However, reported sensitivities and specificities of these tests vary strongly. The aim of this study was to identify diagnostic postures that are biomechanically most sensitive in identifying rotator cuff lesions and compensation mechanisms., Methods: A musculoskeletal modelling study investigating muscle activity in healthy shoulders as well as in shoulders with anterior, superior, and posterosuperior rotator cuff tear patterns, was conducted. Muscle moment arms and muscle synergism for the Lift-off and Bear Hug tests, Jobe and Full-can tests and Infraspinatus and Hornblower tests were compared for healthy and pathological models., Results: In a healthy model the Lift-off test showed significantly higher subscapularis activity compared to the Bear Hug test (p<0.001). Teres minor and infraspinatus activity were threefold and twofold higher, in the Hornblower than the Infraspinatus test, respectively. In superior tests, supraspinatus activity was more than twofold lower than lateral deltoid activity and synergistic activity increase was smallest (Δ 1-3% in deltoid). Activity increase was highest in posterosuperior tests for the teres minor with 66.4% activity increase in the Infraspinatus test (p<0.001) and 81.3% increase in the Hornblower test (p<0.001)., Conclusions: The Lift-off test was significantly more sensitive in detecting subscapularis tears and the Hornblower test was more effective in assessing teres minor integrity in posterosuperior tears. Both, Jobe and Full-can tests demonstrated low biomechanical sensitivity in the detection of superior rotator cuff tears., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Tendon transfers are established techniques to regain external rotation mobility in patients with an irreparable, posterosuperior massive rotator cuff tear (MRCT). Posterosuperior MRCT with intact teres minor (type D MRCT) can lead to excessive teres minor loading to maintain external rotation. We hypothesize that tendon transfers are effective in relieving teres minor loading in type D MRCTs. Our aim was to biomechanically assess muscle synergism with latissimus dorsi (LD transfer) and lower trapezius (LT transfer) tendon transfer during external rotation at different abduction heights., Methods: Using musculoskeletal modeling, we analyzed and compared the moment arm, muscle torque, and muscle activity between a healthy and type D MRCT pathologic model with and without the LD- or LT transfer at infraspinatus and teres minor insertion sites. Output measures were analyzed during external rotation at different abduction angles and 10-50 N resistance against external rotation. We assessed its impact on teres minor loading in a type D MRCT. Morphologic variations were parameterized using the critical shoulder angle and the acromiohumeral distance to address variations among patients., Results: Both transfer types reduced teres minor torque and activity significantly, reaching physiological state at 40 N external resistance (P < .001), with insertion to infraspinatus site being more effective than teres minor site (P < .001). External rotation moment arms of LD transfer were larger than LT transfer at 90° abduction (25.1 ± 0.8 mm vs. 21.2 ± 0.6 mm, P < .001) and vice versa at 0° abduction (17.4 ± 0.5 mm vs. 24.0 ± 0.2 mm, P < .001). Although the healthy infraspinatus was the main external rotator in all abduction angles (50%-70% torque), a type D MRCT resulted in a 70%-90% increase of teres minor torque and an up to 7-fold increase in its activity leading to excessive loadings beyond 10 N resistance against external rotation. Varying the critical shoulder angle and the acromiohumeral distance led to minor variations in muscle moment arm and muscle activity., Conclusion: We identified biomechanical efficacy of both tendon transfers in type D MRCT regarding teres minor load relief and superior performance of the transfers at the infraspinatus insertion site., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)