The tibial cut in total knee arthroplasty influences the varus alignment, the femoral roll-back and the tibiofemoral rotation in patients with constitutional varus.

PURPOSE: Different alignment types for a better outcome after TKA were described. However, it is not clear how kinematic alignment influences knee joint kinematic. The purpose of this study was to analyze whether adapted tibial cuts in constitutional varus knees affect knee joint kinematics regarding femoral roll-back, varus/valgus angle, and femorotibial rotation. METHODS: Seven cadaveric knees with constitutional varus alignment were examined in the native state and after implantation of a cruciate retaining (CR)-TKA with 0°, 3° and 6° tibia cuts using an established knee joint simulator. The effects of varus alignment on femorotibial rollback and rotation was determined. In addition, the native knee joint and different tibial cuts in CR-TKA were compared with Student's t test. RESULTS: Total knee replacement with a 3° and 6° varus tibia cut had the greatest varus deviation to the native knee (mean 1.6° ± 0.09°, respectively); while, knees with a 0° (mean 0.2° ± 0.01°) tibia cut were most similar to the constitutional varus knee joint. The femoral roll-back in the medial compartment was increased in the native knee (5.7-12.5 mm). A 6° varus cut had a restricted translation in the medial compartment (2-3.2 mm). In the lateral compartment, the extensive translation was observed with a 0° varus cut, followed by 3° and 6° and the native knee. All cuts showed significantly different mean values. Only the cuts at 3° and at 6° in the medial compartment and the cuts at 0° and at 3° in the lateral compartment did not differ significantly. In respect to tibiofemoral rotation, 0° and 3° varus cuts across all loads had the least difference to the native knee (3.4°), with a 0° varus cut showing a higher absolute internal rotation of the tibia than the native knee. Changes in knee kinematics of the tibiofemoral rotation showed significantly different mean values. CONCLUSION: The potentially improved outcome parameters in TKA with adapted tibia cuts in constitutional varus knees cannot be completely explained by the changes to knee kinematics. Mechanical alignment seems to result in more balanced load distribution and kinematics more closely resembling the native knee. From a kinematic point of view, it is not recommended to place the tibia in more than 3° of varus. LEVEL OF EVIDENCE: Biomechanical study.

Degeneration alters the biomechanical properties and structural composition of lateral human menisci.

OBJECTIVE: Because the literature relating to the influence of degeneration on the viscoelasticity and tissue composition of human lateral menisci remains contradictory or completely lacking, the aim of this study was to fill these gaps by comprehensively characterising the biomechanical properties of menisci with regard to the degree of degeneration. DESIGN: Meniscal tissue from 24 patients undergoing a total knee replacement was collected and the degeneration of each region classified according to Pauli et al. For biomechanical characterisation, compression and tensile tests were performed. Additionally, the water content was determined and infrared (IR) spectroscopy was applied to detect changes in the structural composition, particularly of the proteoglycan and collagen content. RESULTS: With an increasing degree of degeneration, a significant decrease of the equilibrium modulus was detected, while simultaneously the water content and the hydraulic permeability significantly increased. However, the tensile modulus displayed a tendency to decrease with increasing degeneration, which might be due to the significantly decreasing amount of collagen content identified by the IR measurements. CONCLUSION: The findings of the current study may contribute to the understanding of meniscus degeneration, showing that degenerative processes appear to mainly worsen viscoelastic properties of the inner circumference by disrupting the collagen integrity.

Osseointegration of titanium implants with a novel silver coating under dynamic loading.

Postoperative implant-associated infections are a severe complication in orthopaedics and trauma surgery. To address this problem, a novel implant coating was recently developed, which allows for the release of low concentrations of bactericidal silver. For an intended use on load-bearing endoprostheses, stable bone integration is required. The aim of the present study was to evaluate the biocompatibility and osseointegration of titanium implants with the novel coating in a mechanically loaded bone-defect model in sheep. Silver-coated devices were implanted into weight-bearing and non-weight-bearing tibial and femoral bone defects whereas, in the control group, uncoated titanium implants were inserted. The bony integration of the implants was assessed mechanically and histologically after 6 months. Silver concentrations were assessed in peripheral blood, liver, kidney and local draining lymph nodes as well as at the implantation site. After 6 months, shear strength at the interface and bone apposition to the implant surface were not significantly different between coated and uncoated devices. Mechanical loading reduced bony integration independently of the coating. Silver content at the implantation site was larger in the group with silver-coated implants, yet it remained below toxic levels and no cytotoxic side effects were observed. Concluding, the novel antibacterial silver coating did not negatively influence bone regeneration or implant integration under mechanically unloaded and even loaded conditions, suggesting that the silver coating might be suitable for orthopaedic load-bearing implants, including endoprostheses.

The tibial cut influences the patellofemoral knee kinematics and pressure distribution in total knee arthroplasty with constitutional varus alignment.

PURPOSE: The current literature suggests that kinematic total knee arthroplasty (kTKA) may be associated with better outcome scores in patients with constitutional varus alignment. The underlying patellofemoral kinematic changes (patella tilting and patella tracking) and patellofemoral pressure distribution have not yet been described. The present study compared the effects of different tibial cuts, as used in kTKA, on patellofemoral knee kinematics and the pressure distribution, in addition to comparisons with the natural constitutional varus knee. METHODS: Seven cadaveric knee joints with constitutional varus alignment were examined in the native state and after 0°, 3°, or 6° tibial cut cruciate-retaining (CR)-TKA using an established knee joint simulator. The effects on patella rotation/patella tilting, patellofemoral pressure, and patellofemoral length ratios (= patella tracking) were determined. In addition, the natural knee joint and different tibial cuts in CR-TKA were compared (Student's t test). RESULTS: In the patellofemoral joint, 6° CR-TKA was associated with the greatest similarity with the natural constitutional varus knee. By contrast, knees subjected to 0° CR-TKA exhibited the largest deviations of patellar kinematics. The smallest difference compared with the natural knee joint concerning patella tilting was found for 6° CR-TKA (mean 0.4°, p < 0.001), and the largest difference was noted for 0° CR-TKA (mean 1.7°, p < 0.001). Concerning patellofemoral pressure, 6° CR-TKA resulted in outcomes most similar to the natural knee joint, featuring a mean difference of 3 MPa. The largest difference from the natural knee joint was identified for 0° CR-TKA, with an average difference of 8.1 MPa (p < 0.001; total mean 17.7 MPa). Meanwhile, 3° and 6° CR-TKA induced medialization of the patella, with the latter inducing the largest medialization value of 4.5 mm at 90° flexion. CONCLUSIONS: The improved outcome parameters in kTKA described in the literature could be attributable to the similar kinematics of the patellofemoral joint relative to the normal state. The current study confirmed the similar kinematics between the native constitutional varus knee joint and knee joints subjected to 3° or 6° CR-TKA (patellofemoral rotation/patella tilting and patella pressure). Conversely, there was pronounced medialization of the patella following 6° CR-TKA. Patella pressure and patella tilting are described in the literature as possible causes of anterior knee pain after TKA, whereas medialization of the patella, which is also influenced by other causes, might play a subordinate role. LEVEL OF EVIDENCE: V, Biomechanical study.

Establishment of a clinically relevant large animal model to assess the healing of metaphyseal bone.

Despite the high incidence of metaphyseal bone fractures in patients, the mechanisms underlying the healing processes are poorly understood due to the lack of suitable experimental animal models. Hence, the present study was conducted to establish and characterise a clinically relevant large-animal model for metaphyseal bone healing. Six female adult Merino sheep underwent full wedge-shaped osteotomy at the distal left femur metaphysis. The osteotomy was stabilised internally with a customised anatomical locking titanium plate that allowed immediate post-operative full-weight bearing. Bone healing was evaluated at 12 weeks post-fracture relative to the untouched right femur. Histological and quantitative micro-computed tomography results revealed an increased mineralised bone mass with a rich bone microarchitecture. New trabeculae healed by direct intramembranous ossification, without callus and cartilaginous tissue formation. Stiffness at the cortical and trabecular regions was comparable in both groups. Functional morphological analysis of the osteocyte lacunae revealed regularly arranged spherically shaped lacunae along with the canalicular network. Bone surface biochemical analysis using time-of-flight secondary-ion mass spectrometry showed high and homogeneously distributed levels of calcium and collagenous components. Ultrastructure imaging of the new trabeculae revealed a characteristic parallel arrangement of the collagen fibrils, evenly mineralised by the dense mineral substance. The specialised bone cells were also characterised by their unique structural features. Bone remodelling in the fractured femur was evident in the higher expression levels of prominent bone formation and resorption genes. In conclusion, the novel metaphyseal fracture model is beneficial for studying healing and treatment options for the enhancement of metaphyseal bone defects.

Improved tendon healing using bFGF, BMP-12 and TGFß1 in a rat model.

Several growth factors (GFs) are expressed as tendons heal, but it remains unknown whether their combined application enhances the healing process. This matter was addressed by applying a combination of basic fibroblast growth factor (bFGF), bone morphogenetic protein 12 (BMP-12) and transforming growth factor beta 1 (TGFß1) in a rat Achilles tendon transection model. GFs were applied in one of the three following ways: i) direct application of all three factors at the time of surgery; ii) sequential, tiered percutaneous injection of individual factors immediately after surgery, 48 h and 96 h later; iii) load of all three factors onto a collagen sponge implanted at the time of surgery. After 1, 2, 4 and 8 weeks, healing was assessed based on tendon length and thickness, mechanical strength, stiffness and histology. Best results were achieved when GFs were loaded onto a collagen sponge - with a rapid increase in mechanical strength (load to failure, 71.2 N vs. 7.7 N in controls), consistent tendon length over time (9.9 mm vs. 16.2 mm in controls) and faster tendon remodelling, as measured by histology - followed by tiered injection therapy over 96 h. In conclusion, implantation of a GF-loaded collagen sponge could provide a promising treatment, especially in high-performance athletes and revision cases prone to re-rupture. For conservative treatment, tiered percutaneous GF application could be an option for improving clinical outcome.

Friction properties of a new silk fibroin scaffold for meniscal replacement.

The menisci protect the articular cartilage by reducing contact pressure in the knee. To restore their function after injury, a new silk fibroin replacement scaffold was developed. To elucidate its tribological properties, friction of the implant was tested against cartilage and glass, where the latter is typically used in tribological cartilage studies. The silk scaffold exhibited a friction coefficient against cartilage of 0.056, which is higher than meniscus against cartilage but in range of the requirements for meniscal replacements. Further, meniscus friction against glass was lower than cartilage against glass, which correlated with the surface lubricin content. Concluding, the tribological properties of the new material suggest a possible long-term chondroprotective function. In contrast, glass always produced high, non-physiological friction coefficients.

Influence of tibial hybrid fixation on graft tension and stability in ACL double-bundle reconstruction.

PURPOSE: Initial graft tension in anterior cruciate ligament (ACL) reconstruction affects stability and tension loss at follow-up. This study investigated the influence of hybrid tibial fixation in 3-tunnel double-bundle ACL reconstruction on initial graft tension and tension change and stability under anterior and combined rotatory loads. METHODS: Eleven fresh-frozen cadaveric knees were reconstructed with an ACL double bundle using a 3-tunnel technique. Grafts were tightened to 80 N in 60° (AM bundle) and 15° (PL bundle) of flexion. Anterior tibial translation under 134 N of anterior shear load and translation under combined rotatory and valgus loads (10 Nm valgus stress, 4 Nm internal tibial torque) were determined at 0°, 30°, 60°, and 90° flexion. In addition, graft tension under continuous passive motion was determined. Intact, ACL-resected and ACL-reconstructed joints with either tibial extracortical graft fixation or extracortical plus supplemental aperture graft fixation (hybrid fixation) were tested. RESULTS: Hybrid fixation did not increase graft tension in either bundle during fixation or in motion without additional load. AM-bundle tension increased (p < 0.05) at 0° under combined rotatory and valgus loads and at 30° and 60° under both loading conditions without decreasing the anterior tibial translation. PL-bundle tension increased (p < 0.05) only at 90° under combined rotatory and valgus loads. CONCLUSIONS: Tibial hybrid fixation in 3-tunnel double-bundle ACL reconstruction increases time-zero AM- and PL-bundle tensions under loading conditions, generating greater construct stiffness. This could lead to a longer preservation of ACL-graft stability in clinical follow-up before bony incorporation.

Short-term glucocorticoid treatment causes spinal osteoporosis in ovariectomized rats.

PURPOSE: In humans, glucocorticoid-induced osteoporosis is the most common cause of medication-induced osteoporosis. Recent clinical data suggest that glucocorticoid therapy increases the risk of vertebral fractures within a short treatment period. Therefore, this study aimed at investigating vertebral bone in a rat model of glucocorticoid-induced postmenopausal osteoporosis. METHODS: Fifty Sprague-Dawley rats were randomly assigned into three groups: 1) untreated controls, 2) Sham-operated group, and 3) ovariectomized rats treated with glucocorticoid (dexamethasone) for 3 months (3M) after recovery from bilateral ovariectomy. Osteoporotic bone status was determined by means of the gold standard dual energy X-ray absorptiometry (DEXA) scan. Vertebral bodies were examined using µCT, histological analysis, mRNA expression analysis, and biomechanical compression testing. Further systemic effects were studied biochemically using serum marker analysis. RESULTS: Dexamethasone treatment showed at 3M a significantly lower bone mineral density in ovariectomized rats compared to Sham-operated control (p < 0.0001) as analyzed in vivo by DEXA. Furthermore, Z scores reached levels of -5.7 in the spine indicating sever osteoporotic bone status. Biomechanical testing of compression stability indicated a lower functional competence (p < 0.0001) in the spine of treated rats. µCT analysis showed significant reduction of bone volume density (BV/TV%; p < 0.0001), significantly enhanced trabecular spacing (Tb.Sp; p < 0.0001) with less trabecular number (Tb.N; p < 0.001) and complete loss of trabecular structures in glucocorticoid-treated ovariectomized rats. Histological analysis by osteoblast and osteoclast activities reflected a higher bone catabolism reflected by osteoclast counts by TRAP (p < 0.019) and lower bone catabolism indicated by ALP-stained area (p < 0.035).Serum analysis showed a significant increase in osteocalcin (p < 0.0001), osteopontin (p < 0.01) and insulin (p < 0.001) at 3M. Expression analysis of molecular markers in the vertebral body revealed lower expression in tenascin C in the OVX-steroid animals at 3M. CONCLUSIONS: Short-term glucocorticoid treatment of ovariectomized rats indicates according to DEXA standards a severe osteoporotic bone status in vertebral bone. Nonetheless, dysfunctional bone anabolism and enhanced bone catabolism are observed. Alterations of bone extracellular matrix proteins that correlate to inferior mechanical stability and affected microstructure were noticed and suggest further investigation. Treatment with dexamethasone was also seen to affect insulin and osteopontin levels and thus osteoblast function and maturation. This described animal model presents a recapitulation of clinically obtained data from early phase glucocorticoid-induced osteoporosis observed in patients.

The effects of femoral external derotational osteotomy on frontal plane alignment.

PURPOSE: Femoral osteotomies are the preferred treatment in significant torsional deformity of the femur. The influence of torsional osteotomies on frontal plane alignment is poorly understood. Therefore, the aim of the present study was to evaluate the effects of external derotational osteotomies on proximal, mid-shaft and distal levels onto frontal plane alignment. METHODS: The effect of rotation around the anatomical axis of the femur on frontal plane alignment was determined with a 3D computer model, created from CT data of a right human cadaver femur. Virtual torsional osteotomies of 10°, 20° and 30° were performed at proximal, mid-shaft and distal levels under five antecurvatum angles of the femur. The change of the frontal plane alignment was expressed by the mechanical lateral femoral angle. RESULTS: Proximal derotational osteotomies resulted in an increased mechanical lateral distal femoral angle (mLDFA) of 0.8°-2.6° for 10°, of 1.6°-5.1° for 20° and of 2.3-7.9° for 30° derotational osteotomy, indicating an increased varus angulation. Supracondylar derotational osteotomy resulted in a decreased mLDFA of -0.1° to -1.7° for 10°, of -0.2 to -3.7° for 20° and of -0.7 to -6.9° for 30° derotational osteotomy, indicating an increased valgus angulation. The effect increased with the amount of torsional correction and virtually increased antecurvatum angles. Mid-shaft torsional osteotomies had the smallest effect on frontal plane alignment. CONCLUSION: This three-dimensional computer model study demonstrates the relationship between femoral torsional osteotomies and frontal plane alignment. Proximal external derotational osteotomies tend to result in an increased varus angulation, whilst distal external derotational osteotomies tend to result in an increased valgus angulation. As a clinical consequence, torsional osteotomies have an increased risk of unintentional implications on frontal plane alignment.

[Physical characterization of decellularized cartilage matrix for reconstructive rhinosurgery]. / Physikalische Charakterisierung dezellularisierter Knorpelmatrix zur Anwendung in der Rhinochirurgie.

BACKGROUND: The use of autologous auricular and rib cartilage for the reconstruction of nasal defects and deformities is associated with a number of disadvantages. The development of alternative materials is therefore the focus of intensive research. Recent studies demonstrated that decellularized cartilage is a promising material for cartilage tissue engineering. Hence, the aim of this study was to characterize the materials surface and cellular reactions to the decellularized cartilage matrix in long term-3D-culture. MATERIAL AND METHODS: Material geometry of decellularized cartilage was examined by microcomputed tomography as well as material characteristics by scanning and transmission electron microscopy. The expression of integrins on the surface of human chondrocytes was determined after seeding and migration into the scaffold. RESULTS: After decellularization an obvious enlargement of the matrix surface and an intensive interaction between the chondrocytes and the collagen matrix was observed. ITGA1 and ITGB1 were upregulated indicating chondrogenic differentiation. CONCLUSION: Therefore, decellularized porcine cartilage provides an optimal microstructure for human chondrocytes with respect to cell integration and matrix production. Thus, it offers promising characteristics for clinical application in reconstructive surgery.

[Anterior meniscotibial ligaments. Forces under various load conditions]. / Die anterioren meniskotibialen Ligamente. Kräfte unter verschiedenen Lastsituationen.

The main biomechanical function of the knee meniscus is to enlarge the contact area of the tibiofemoral joint leading to a reduction in articular cartilage contact stress. The meniscal attachments are essential for converting the axial load into circumferential tension in the meniscal periphery. Consequently, meniscal substitutes need sufficient anchorage to the tibial plateau to adequately restore the biomechanical function of a replaced meniscus. Therefore the aim of the present study was to investigate the loads acting on the anterior meniscotibial attachments under various joint loads.

Maximum tensile force of different suture techniques in reconstruction of the renal remnant after nephron-sparing surgery.

BACKGROUND: In nephron-sparing surgery, the closure of the renal remnant is one of the major critical steps in preventing possible complications. Several suture techniques can be used for this purpose. The type of suture used depends on the discretion of the surgeon and not on validated experimental data. METHODS: In an experimental setting, the renal remnant of a standardized defect in 20 porcine kidneys (with and without an intact renal capsule) was reconstructed using three different suture techniques (simple, vertical, and horizontal mattress suture). The maximum tensile force before the suture tears through the renal remnant was recorded. RESULTS: The horizontal mattress suture attains the highest maximum tensile force by far. The values of the simple and vertical mattress sutures are surpassed, with a respective increase of 140 and 83% if the capsule is intact and 172 and 109% if the capsule is not intact. If an intact renal capsule is present, the maximum tensile force in each suture technique increases 43-63%. CONCLUSIONS: The data suggest that of all tested suture techniques, the horizontal mattress suture provides the best adaptation strength before the suture tears through the renal parenchyma/capsule. Furthermore, it is recommended that the kidney capsule be included in the reconstructive suture because this significantly contributes to the safety of the procedure.

[Treatment of peritrochanteric fractures: biomechanical considerations]. / Versorgung pertrochantärer Femurfrakturen: Biomechanische Überlegungen.

Biomechanical considerations are relevant in the treatment of peritrochanteric fractures. Concomitant diseases and osteoporosis place high demands on the primary stability of the operative treatment. In the situation of unstable fractures (AO/ASIF 31-A2 and A3), even normal activities of life can easily exceed the critical limits of stability, which can result in implant failure. Both intramedullary and extramedullary implants are used successfully in the treatment of even unstable fractures. Different variations in the implant design and anchorage of the load carrier of the femoral neck are available and may have different biomechanical characteristics. Biomechanical tests show that new developments of implants can increase stability. Nevertheless, accurate reduction and operative technique is essential to ensure uneventful fracture healing. Although some supportive measures are very promising, such as augmentation, further research is required to increase stability in the unstable and osteoporotic fracture situation.

Optimizing Manufacturing and Osseointegration of Ti6Al4V Implants through Precision Casting and Calcium and Phosphorus Ion Implantation? In Vivo Results of a Large-Scale Animal Trial.

BACKGROUND: Uncemented implants are still associated with several major challenges, especially with regard to their manufacturing and their osseointegration. In this study, a novel manufacturing technique-an optimized form of precision casting-and a novel surface modification to promote osseointegration-calcium and phosphorus ion implantation into the implant surface-were tested in vivo. METHODS: Cylindrical Ti6Al4V implants were inserted bilaterally into the tibia of 110 rats. We compared two generations of cast Ti6Al4V implants (CAST 1st GEN, n = 22, and CAST 2nd GEN, n = 22) as well as cast 2nd GEN Ti6Al4V implants with calcium (CAST + CA, n = 22) and phosphorus (CAST + P, n = 22) ion implantation to standard machined Ti6Al4V implants (control, n = 22). After 4 and 12 weeks, maximal pull-out force and bone-to-implant contact rate (BIC) were measured and compared between all five groups. RESULTS: There was no significant difference between all five groups after 4 weeks or 12 weeks with regard to pull-out force (p > 0.05, Kruskal Wallis test). Histomorphometric analysis showed no significant difference of BIC after 4 weeks (p > 0.05, Kruskal-Wallis test), whereas there was a trend towards a higher BIC in the CAST + P group (54.8% ± 15.2%), especially compared to the control group (38.6% ± 12.8%) after 12 weeks (p = 0.053, Kruskal-Wallis test). CONCLUSION: In this study, we found no indication of inferiority of Ti6Al4V implants cast with the optimized centrifugal precision casting technique of the second generation compared to standard Ti6Al4V implants. As the employed manufacturing process holds considerable economic potential, mainly due to a significantly decreased material demand per implant by casting near net-shape instead of milling away most of the starting ingot, its application in manufacturing uncemented implants seems promising. However, no significant advantages of calcium or phosphorus ion implantation could be observed in this study. Due to the promising results of ion implantation in previous in vitro and in vivo studies, further in vivo studies with different ion implantation conditions should be considered.

[Possibilities and limits in tissue engineering of the anterior cruciate ligament]. / Möglichkeiten und Grenzen des "tissue engineering" des vorderen Kreuzbandes.

Although current concepts of cruciate ligament reconstruction using tendon transplants provide midterm knee joint stabilization, a single-bundle or double-bundle tendon cannot adequately restore the complex three-dimensional structure of the anterior cruciate ligament. Therefore, researchers are attempting to develop alternatives using tissue engineering technology. The basic principle includes seeding of suitable cells on a resorbable carrier construct, in vitro biological and mechanical stimulation to generate a ligament-like extracellular matrix, and subsequent implantation as a cruciate ligament bioprosthesis. Several natural and synthetic materials have proven to be suitable as cell carriers; however, most of these exhibit inadequate tensile strength as well as minor fatigue properties, making an additional load carrier necessary. In principle, research has shown that tissue engineering technology is capable of generating a construct with a ligament-like extracellular matrix. However, the step from basic research to clinical application has not yet been taken.

[Efficient document management by introduction of a new, dynamic quality manual application according to DIN EN ISO 9001:2000]. / Effiziente Qualitätsmanagementdokumentation durch Einführung eines neuen, dynamischen Qualitätsmanagementhandbuchs nach DIN EN ISO 9001:2000.

PURPOSE: Evaluation of the impact of a new, dynamic computer-aided quality manual application (QMA) regarding the acceptance and efficiency of a quality management system (QMS) according to DIN EN ISO 9001:2000. MATERIALS AND METHOD: The QMA combines static pages of HTML with active content generated from an underlying database. Through user access rights, a hierarchy is defined to create and administer quality documents. Document workflow, feedback management and employee survey were analyzed to compare the performance of the new QMH with the formerly used static version. RESULTS: Integration of a document editor and automated document re-approval accelerated the document process by an average of 10 min. In spite of an increase of the yearly document changes of 60%, the administration effort was reduced by approximately 160 h. Integration of the feedback management system into the QMA decreased handling time from an average of 16.5 to 3.4 days. Simultaneously the number of feedback messages increased from 160 in 2005 to 306 in 2006. Employee satisfaction was raised (old: 3.19+/-1.02, new: 1.91+/-0.8). The number of users who partook in the QMA more than once a week also increased from 29.5% to 60%. CONCLUSION: The computer-aided quality manual application constitutes the basis for the success of our QMS. The possibility to actively participate in the quality management process has led to broad acceptance and usage by the employees. The administration effort was able to be tremendously decreased as compared to conventional QMS.

Features of haptic and tactile feedback in TORS-a comparison of available surgical systems.

Sustained interest and an increase of possible indications endorse the role of robot-assisted surgery of the head and neck region. However, broad clinical application is impeded by substantial extra cost, time exposure and a supposed deficit of haptic and tactile feedback. The role of haptic feedback has barely been examined in this context, and literature provides only limited objective validation. This point of criticism applies to all commercially available systems. We created an experimental setup to evaluate, quantify and compare the performance of surgical systems. The daVinci system (Intuitive Surgical), the Flex system (Medrobotics) and standard rigid instruments (23 cm laryngoscopic grasper, Karl Storz) were compared with the human hand by head and neck surgeons (n = 15), performing a variety of surgical tasks. Specific samples with different rigidity were sorted with all devices, and the resulting orders were analyzed by permutation analysis, indicating differences in precision and accuracy of haptic and tactile feedback. The human hand was superior in all trials, acting as reference modality. The flexible instruments of the Flex system performed better than the electro-mechanically decoupled instruments of the daVinci system for the majority of measures recorded, suggesting a benefit in terms of haptic and tactile feedback in this context. While not all aspects of haptic and tactile feedback were accessible, this first objective comparison endorses the inferiority of robot-assisted surgery in terms of haptic and tactile feedback, compared to the human sense or standard surgical tools. Furthermore, the immediate force transmission of the Flex system seems to be superior to the electro-mechanical transformation of the daVinci system, indicating an advantage in terms of haptic and tactile feedback in immediate comparison. This study is providing a basis for further experiments and the development of robotic surgery towards an implementation in clinical routine.

Can a finite set of knee extension in supine position be used for a knee functional examination?

The kinematic magnetic resonance imaging technique has been developed to provide a functional examination of the knee. Technical limitations require this examination to be performed in supine position, and the knee motion is represented by an assembly of static positions at different knee angles. However, the main knee function is to support the body weight and perform continuous motion, e.g. parallel squat. Our study quantified the knee kinematics of 20 healthy subjects in different motion conditions (finite and continuous) and in different mechanical conditions (continuous unloaded and continuous loaded). We evaluated the angular and localisation difference of a finite helical axis of the knee motion for parallel squat, continuous knee extension in supine position and the finite set of knee extension in supine position. We found large inter-individual dispersion. The majority of subjects had equivalent knee kinematics between continuous knee extension and the finite set of knee extension in supine position, but not between continuous knee extension in supine position and the parallel squat. Therefore, results from a functional examination of a finite set of knee extensions in supine position do not represent the knee motion in a parallel squat. Our results suggest that functional examination of the knee from magnetic resonance imaging do not necessarily reflect the physiological kinematics of the knee. Further investigation should focus on a new magnetic resonance imaging acquisition protocol that allows image acquisition during weight bearing or includes a special device which reproduces the loaded condition.

Quantification of the 3D relative movement of external marker sets vs. bones based on magnetic resonance imaging.

BACKGROUND: Most in vivo knee kinematic analyses are based on external markers attached to the shank and the thigh. Literature data show that markers positioning and soft tissues artifacts affect the kinematic parameters of the bones true movement. Most of the techniques of quantification used were invasive. The aim of the present study was to develop and apply a non-invasive methodology to compute the relative movement between the bones and the markers. METHODS: Magnetic resonance imaging acquisitions were performed on the right knee of eleven volunteers without knee injury. The subjects were equipped with external magnetic resonance imaging-compatible marker sets. A foot drive device allowed the subjects to perform an actively loaded knee extension. The whole volume of the subject's knee was processed for four sequentially held knee flexion positions during the knee movement. The bones and external marker sets geometry were reconstructed from magnetic resonance imaging images. Then a registration algorithm was applied to the bones and the relative movement of the thigh and shank marker sets with respect to their underlying bones was computed. FINDINGS: The protocol resulted in a good geometrical accuracy and reproducibility. Marker sets movement differ from that of the bones with a maximum of 22 mm in translation and 15 degrees in rotation and it affects the knee kinematics. INTERPRETATION: Marker sets relative movement modify the knee movement finite helical axes direction (range 10-35 degrees ) and localization (range 0-40 mm). The methodology developed can evaluate external marker set system to be used for kinematic analysis in a clinical environment.