Influence of footwear and equipment on stride length and range of motion of ankle, knee and hip joint

PURPOSE

Footwear and equipment worn by military personnel is of importance for them to be able to meet the physical demands specific to their profession daily activities. The aim of the present study was to investigate by means of gait analysis how army-provided footwear and equipment influence the range of motion of hip, knee and ankle joints as well as stride length.

METHODS

Thirty-two soldiers were subjected to gait analysis on a treadmill by way of video recordings and goniometric measurements.

RESULTS

The stride length increased when military shoes are worn. We found no influence on stride length in connection to increased loading. The weight of the shoes represents the decisive factor. Neither shoes nor equipment changed the range of motion of the knee joint. Weight of equipment affected range of motion of the hip joint. The range of motion of the upper and lower ankle joints was mainly influenced by the properties of the shoes.

CONCLUSIONS

Military footwear and weight of equipment influence stride length and range of motion of joints of the lower extremities in a specific way. Shape of material is the decisive factor.

A model of implant-associated infection in the tibial metaphysis of rats

OBJECTIVE

Implant-associated infections remain serious complications in orthopaedic and trauma surgery. A main scientific focus has thus been drawn to the development of anti-infective implant coatings. Animal models of implant-associated infections are considered helpful in the in vivo testing of new anti-infective implant coatings. The aim of the present study was to evaluate a novel animal model for generation of implant-associated infections in the tibial metaphysis of rats.

MATERIALS AND METHODS

A custom-made conical implant made of Ti6Al4V was inserted bilaterally at the medial proximal tibia of 26 female Sprague-Dawley rats. Staphylococcus aureus in amounts spanning four orders of magnitude and each suspended in 15  μ l phosphate buffered saline (PBS) was inoculated into the inner cavity of the implant after the implantation into the defined position. Controls were treated accordingly with PBS alone. Animals were then followed for six weeks until sacrifice. Implant-associated infection was evaluated by microbiological investigation using swabs and determination of viable bacteria in the bone around the implant and the biofilm on the implants after sonification.

RESULTS

Irrespective of the initial inoculum, all animals in the various groups harbored viable bacteria in the intraoperative swabs as well as the sonication fluid of the implant and the bone samples. No correlation could be established between initially inoculated CFU and population sizes on implant surfaces at sacrifice. However, a significantly higher viable count was observed from peri-implant bone samples for animals inoculated with 10(6) CFU. Macroscopic signs of animal infection (pus and abscess formation) were only observed for implants inoculated with at least 10(5) CFU S. aureus.

DISCUSSION/CONCLUSION

The results demonstrate the feasibility of this novel animal model to induce an implant-associated infection in the metaphysis of rats, even with comparatively low bacterial inocula. The specific design of the implant allows an application of bacteria in reproducible numbers at well-defined contact sites to the animal bone.

Characterization of polyethylene wear particle: The impact of methodology

Due to the prevalence of problems caused by wear particles, the reduced durability of total joint replacements is well documented. The characterization of wear debris enables the size and morphology of these wear particles to be measured and provides an assessment of the biological response in vivo. However, the impact of different methodologies of particle analysis is not yet clear. Hence, the aim of this investigation was to analyze the influence of different particle characterization methods performed by three research centers within the scope of a "round robin test". To obtain knowledge about possible pitfalls, single steps of the particle characterization process (storage, pore size of the filter, coating durations by gold sputtering and scanning electron microscopy (SEM) magnification) were analyzed. The round robin test showed significant differences between the research groups, especially for the morphology of the particles. The SEM magnification was identified as having the greatest influence on the size and shape of the particles, followed by the storage conditions of the wear particle containing lubricant. Gold sputter coating and filter pore size also exhibit significant effects. However, even though they are statistically significant, it should be emphasized that the differences are small. In conclusion, particle characterization is a complex analytical method with a multiplicity of influencing factors. It becomes apparent that a comparison of wear particle results between different research groups is challenging.

Total knee replacement system with a ceramic femoral component versus two traditional metallic designs: a prospective short-term study

PURPOSE

To compare the short-term outcome of the Multigen Plus system using a symmetric ceramic femoral component with that of 2 metallic total knee replacement (TKR) systems.

METHODS

60 patients (62 knees) with osteoarthritis or rheumatoid arthritis underwent primary TKR using the Genia system (n=20), the Multigen Plus system (n=17), and the Multigen Plus system with a ceramic femoral component (n=25). Outcome was evaluated pre- and post-operatively (at 3, 12, and 24 months) using the Hospital for Special Surgery (HSS) score, the Western Ontario and McMaster Universities (WOMAC) score, and the Short-Form 36 (SF-36) score.

RESULTS

The 3 groups did not differ significantly at all 4 time points in terms of the HSS score, WOMAC score, and SF-36 score. The range of motion was significantly less in patients treated with the Genia system. Postoperatively, the HSS and WOMAC scores improved significantly in all 3 groups, whereas the SF-36 score improved significantly (at 12 and 24 months) only in patients treated with the Multigen Plus system with a ceramic femoral component. The implant position in most patients was optimal. All radiolucent lines were within 1 mm and did not progress.

CONCLUSION

The short-term outcome of the 3 TKR systems was comparable. Ceramic femoral components performed comparably to traditional metallic designs.

Articular cartilage-derived cells hold a strong osteogenic differentiation potential in comparison to mesenchymal stem cells in vitro

Cartilaginous matrix-degenerative diseases like osteoarthritis (OA) are characterized by gradual cartilage erosion, and also by increased presence of cells with mesenchymal stem cell (MSC) character within the affected tissues. Moreover, primary chondrocytes long since are known to de-differentiate in vitro and to be chondrogenically re-differentiable. Since both findings appear to conflict with each other, we quantitatively assessed the mesenchymal differentiation potential of OA patient cartilage-derived cells (CDC) towards the osteogenic and adipogenic lineage in vitro and compared it to that of MSC isolated from adipose tissue (adMSC) of healthy donors. We analyzed expression of MSC markers CD29, CD44, CD105, and CD166, and, following osteogenic and adipogenic induction in vitro, quantified their expression of osteogenic and adipogenic differentiation markers. Furthermore, CDC phenotype and proliferation were monitored. We found that CDC exhibit an MSC CD marker expression pattern similar to adMSC and a similar increase in proliferation rate during osteogenic differentiation. In contrast, the marked reduction of proliferation observed during adipogenic differentiation of adMSC was absent in CDC. Quantification of differentiation markers revealed a strong osteogenic differentiation potential for CDC, however almost no capacity for adipogenic differentiation. Since in the pathogenesis of OA, cartilage degeneration coincides with high bone turnover rates, the high osteogenic differentiation potential of OA patient-derived CDC may affect clinical therapeutic regimens aiming at autologous cartilage regeneration in these patients.

New Coating Technique of Ceramic Implants with Different Glass Solder Matrices for Improved Osseointegration-Mechanical Investigations

Ceramics are a very popular material in dental implant technology due to their tribological properties, their biocompatibility and their esthetic appearance. However, their natural surface structure lacks the ability of proper osseointegration, which constitutes a crucial process for the stability and, thus, the functionality of a bone implant. We investigated the application of a glass solder matrix in three configurations—consisting mainly of SiO₂, Al₂O₃, K₂O and Na₂O to TZP-A ceramic specimens. The corresponding adhesive strength and surface roughness of the coatings on ceramic specimens have been analyzed. Thereby, high adhesive strength (70.3 ± 7.9 MPa) was found for the three different coatings. The obtained roughness (R_z) amounted to 18.24 ± 2.48 µm in average, with significant differences between the glass solder configurations. Furthermore, one configuration was also tested after additional etching which did not lead to significant increase of surface roughness (19.37 ± 1.04 µm) or adhesive strength (57.2 ± 5.8 MPa). In conclusion, coating with glass solder matrix seems to be a promising surface modification technique that may enable direct insertion of ceramic implants in dental and orthopaedic surgery.

Wear testing and particle characterisation of sequentially crosslinked polyethylene acetabular liners using different femoral head sizes

Larger femoral heads lead to a decreased risk of total hip dislocation and an improved range of motion. However, the larger diameter is associated with increased wear rates. The low wear rates of crosslinked polyethylene opens up the possibility of using larger heads. The aim of this experimental study was to evaluate the wear of conventional non-crosslinked versus sequentially crosslinked polyethylene liners in combination with different ceramic head sizes (28, 36, 44 mm). Wear testing was performed in a hip simulator according to ISO 14242. Wear particles from the polyethylene liners were characterized after wear testing. The wear measurements revealed a significant increase in the wear of crosslinked polyethylene liners with larger heads. By sequential crosslinking, however, the gravimetric wear using larger heads was reduced to a fractional amount of the wear using conventional polyethylene. Significant differences were observed for particle morphology but not for the number of particles when comparing non-crosslinked and crosslinked polyethylene.

Cell viability, collagen synthesis and cytokine expression in human osteoblasts following incubation with generated wear particles using different bone cements

In total hip arthroplasty, wear particles generated at articulating surfaces and interfaces between bone, cement and implants have a negative impact on osteoblasts, leading to osteolysis and implant loosening. The aim of this experimental study was to determine the effects of particulate wear debris generated at the interface between straight stainless steel hip stems (Exeter(®)) and three different bone cements (Palacos(®) R, Simplex™ P and Cemex(®) Genta) on cell viability, collagen synthesis and cytokine expression in human osteoblasts. Primary osteoblasts were treated with various concentrations of wear particles. The synthesis of procollagen type I and different cytokines was analysed, and markers for apoptosis and necrosis were also detected. The cytokine synthesis rates in the osteoblasts were initially increased and varied, depending on incubation time and particle concentration. Specific differences in the synthesis rates of interleukin (IL)‑6, IL-8, vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) were observed with the different bone cements examined. The negative effect of the particles on the synthesis of procollagen type I and increased rates of cell apoptosis and necrosis were observed with all three cements analysed. Our present data suggest that wear particles from the interface between the total hip stem and bone cement have a significant effect on viability, cytokine expression and collagen synthesis in human osteoblasts, depending on the bone cement used.

The IGFBP7 homolog Imp-L2 promotes insulin signaling in distinct neurons of the Drosophila brain

In Drosophila, Insulin-like peptide 2 (Dilp-2) is expressed by insulin-producing cells in the brain, and is secreted into the hemolymph to activate insulin signaling systemically. Within the brain, however, a more local activation of insulin signaling may be required to couple behavioral and physiological traits to nutritional inputs. We show that a small subset of neurons in the larval brain has high Dilp-2-mediated insulin signaling activity. This local insulin signaling activation is accompanied by selective Dilp-2 uptake and depends on the expression of the Imaginal morphogenesis protein-late 2 (Imp-L2) in the target neurons. We suggest that Imp-L2 acts as a licensing factor for neuronal IIS activation through Dilp-2 to further increase the precision of insulin activity in the brain.

[Principles of tribological analysis of endoprostheses]

For the tribological characterization of artificial joints, various experimental methods are currently available. However, the in vitro test conditions applied are only comparable in a limited way and transferability to the in vivo situation is also restricted. This is due to the different wear simulation concepts used and partly insufficient simulation of clinical worst case situations. In the present paper current scientific methods and procedures for tribological testing of artificial joints are presented. In addition, the biological effects of wear products are described enabling clinicians to challenge tribological studies and to facilitate specific interpretation of scientific results taking the clinical situation into account.

In vivo examination of the local inflammatory response after implantation of Ti6Al4V samples with a combined low-temperature plasma treatment using pulsed magnetron sputtering of copper and plasma-polymerized ethylenediamine

Copper (Cu) could serve as antibacterial coating for Ti6Al4V implants. An additional cell-adhesive layer might compensate Cu cytotoxicity. This study aimed at in vitro and in vivo evaluation of low-temperature plasma treatment of Ti6Al4V plates with Ti/Cu magnetron sputtering (Ti6Al4V-Ti/Cu), plasma-polymerized ethylenediamine (Ti6Al4V-PPEDA), or both (Ti6Al4V-Ti/Cu-PPEDA). Ti6Al4V-Ti/Cu and Ti6Al4V-Ti/Cu-PPEDA had comparable in vitro Cu release and antibacterial effectiveness. Following intramuscular implantation of Ti6Al4V-Ti/Cu, Ti6Al4V-PPEDA, Ti6Al4V-Ti/Cu-PPEDA and Ti6Al4V controls for 7, 14 and 56 days with 8 rats/day, peri-implant tissue was immunohistochemically examined for different inflammatory cells. Ti6Al4V-PPEDA had more mast cells and NK cells than Ti6Al4V, and more tissue macrophages, T lymphocytes, mast cells and NK cells than Ti6Al4V-Ti/Cu-PPEDA. Ti6Al4V-Ti/Cu had more mast cells than Ti6Al4V and Ti6Al4V-Ti/Cu-PPEDA. Results indicate that PPEDA-mediated cell adhesion counteracted Cu cytotoxicity. Ti6Al4V-Ti/Cu-PPEDA differed from Ti6Al4V only for mast cells on day 56. Altogether, implants with both plasma treatments had antibacterial properties and did not increase inflammatory reactions.

Age-related changes in neuromuscular function of the quadriceps muscle in physically active adults

Substantial evidence exists for the age-related decline in maximal strength and strength development. Despite the importance of knee extensor strength for physical function and mobility in the elderly, studies focusing on the underlying neuromuscular mechanisms of the quadriceps muscle weakness are limited. The aim of this study was to investigate the contributions of age-related neural and muscular changes in the quadriceps muscle to decreases in isometric maximal voluntary torque (iMVT) and explosive voluntary strength. The interpolated twitch technique and normalized surface electromyography (EMG) signal during iMVT were analyzed to assess changes in neural drive to the muscles of 15 young and 15 elderly volunteers. The maximal rate of torque development as well as rate of torque development, impulse and neuromuscular activation in the early phase of contraction were determined. Spinal excitability was estimated using the H reflex technique. Changes at the muscle level were evaluated by analyzing the contractile properties and lean mass. The age-related decrease in iMVT was accompanied by a decline in voluntary activation and normalized surface EMG amplitude. Mechanical parameters of explosive voluntary strength were reduced while the corresponding muscle activation remained primarily unchanged. The spinal excitability of the vastus medialis was not different while M wave latency was longer. Contractile properties and lean mass were reduced. In conclusion, the age-related decline in iMVT of the quadriceps muscle might be due to a reduced neural drive and changes in skeletal muscle properties. The decrease in explosive voluntary strength seemed to be more affected by muscular than by neural changes.

[Recommendations for documentation of incidents with medical devices in orthopaedic surgery]

The growing number of revisions in orthopaedic surgery as well as the multifactorial reasons for implant failure give cause for taking a closer look at the clinical documentation of adverse events. Based on our long-term experience it is our goal to present recommendations for an adequate documentation and filing. In the framework of the introduction of a quality management system (ISO 9001:2008) in our hospital, a process was developed for reportable incidents with medical devices regulating adequate documentation. Therefore, specific forms were developed. The retrievals are stored for subsequent damage analyses and are available for possible legal claims and tracking. A file should be opened for each reportable incident containing information about the event, a copy of the obligatory BfArM report, surgery report, medical device labels, radiographs and photographs. Declarations of agreement as well as handover certificates should be maintained in order to keep record of the retrievals. In order to assure consistent documentation, we recommend use of specific forms as presented in this paper. Identification of risk factors for implant failure and a long-term reduction of damage cases will only be possible under consequent incident reporting and responsible documentation of adverse events. Processing of cases of damage is accelerated and simplified by the presented recommendations and forms. Together with the newly established joint replacement registry, a higher quality of patient treatment and implant safety should be obtained.

Biomechanical study of the influence of the weight of equipment on selected trunk muscles

Overexertion and pain of the musculoskeletal system may occur partly owing to load application by the equipment. Both the weight of equipment and the duration of loading are relevant. The aim of the present study was to examine the extent of loading and resultant strain in the trunk muscles. Therefore, the trunk posture of soldiers and muscular activity in reaction to different equipment components (helmet, load-carrying equipment, gun and backpack) were evaluated. Electromyography was performed and a visual assessment of body axis was conducted based on standardised planar images. Data indicate that the activity of the trunk muscles examined (latissimus dorsi, trapezius and pectoralis major) is dependent on the weight and distribution of the equipment components. Activity in the trapezius muscle, for instance, was doubled during specific load application. Moreover, the method of carrying the rifle had a significant influence on the activity of the trapezius muscle (one-sided decrease of activity by 50%). Subjects were able to stabilise the body axis in the coronal plane through increased muscle activity, however, in the sagittal plane a compensatory ventral inclination of the body was observed. Uneven load distribution can lead to an irregular strain on the musculoskeletal system.