Restoring more natural kinematics is crucial for the success of knee TKA. The relative size of the tibia to the femur may differ in each patient and requires the possibility to combine different tibia sizes for a given femur size. Therefore, TKA systems need to be designed to allow for different size combinations. In literature some report higher revision rates when the femoral size is greater than the tibia, while others find no impact of the size mismatch on the clinical outcome. The tibio-femoral kinematics resulting from different size combinations has not been analyzed yet. The Columbus Deep Dish implant (Aesculap, Tuttlingen, Germany) is designed to allow a full size compatibility. Therefore we hypothesized that the kinematics would not be affected by the different size combinations. The goal of this study was to investigate the impact on kinematics of different tibio-femoral size combinations with the Columbus Deep Dish implant. 6 fresh frozen cadavers were tested in a force controlled well established knee rig after implantation of a cruciate retaining, fixed bearing Columbus Deep Dish TKA (Aesculap, Tuttlingen, Germany). Femoro-tibial kinematics were recorded while performing a loaded squat from 30° to 130°. Specifically developed and manufactured inlays allowed simulating different tibia sizes on each bone/tibial implant. For each cadaver, a total of 4 different tibia sizes were tested (1 original size, 3 simulated different sizes). Tibio-femoral internal/external rotation and antero-posterior translation of the medial and of the lateral condyles were computed for all size combinations. The kinematics obtained with the simulated sizes were compared to the kinematics obtained with the original inlay. For each flexion angle from 30° to 130°, the difference between the rotation (resp. translation) obtained with the original inlay was subtracted from the rotation obtained with the simulated tibia size. The mean value and standard deviation of the differences were computed.Objectives
Methods
Revision total hip arthroplasty is often associated with acetabular bone defects. In most cases, assessment of such defects is still qualitative and biased by subjective interpretations. Three-dimensional imaging techniques and novel anatomical reconstructions using statistical shape models (SSM) allow a more impartial and quantitative assessment of acetabular bone defects [1]. The objectives of this study are to define five clinically relevant parameters and to assess 50 acetabular bone defects in a quantitative way. Anonymized CT-data of 50 hemi-pelvises with acetabular bone defects were included in the study. The assessment was based on solid models of the defect pelvis (i.e. pelvis with bone defect) and its anatomical reconstruction (i.e. native pelvis without bone defect) (Fig.1A). Five clinically relevant parameters were defined: (1) Bone loss, defined by subtracting defect pelvis from native pelvis. (2) Bone formation, defined by subtracting native pelvis from defect pelvis. Bone formation represents bone structures, which were not present in the native pelvis (e.g. caused by remodeling processes around a migrated implant). (3) Ovality, defined by the length to width ratio of an ellipse fitted in the defect acetabulum. A ratio of 1.0 would represent a circular acetabulum. (4) Lateral center-edge angle (LCE angle), defined by the angle between the most lateral edge of the cranial roof and the body Z-axis, and (5) implant migration, defined by the distance between center of rotation (CoR) of the existing implant and CoR of native pelvis (Fig. 1B).Introduction
Methods
It is well-known that wear debris generated by metal-on-metal hip replacements leads to aseptic loosening. This process starts in the local tissue where an inflammatory reaction is induced, followed by an periprosthetic osteolysis. MOM bearings generate particles as well as ions. The influence of both in human bodies is still the subject of debate. For instance hypersensitivity and high blood metal ion levels are under discussion for systemic reactions or pseudotumors around the hip replacement as a local reaction. The exact biopathologic mechanism is still unknown. The aim of this study was to investigate the impact of local injected metal ions and metal particles. We used an established murine inflammation model with Balb/c mice and generated three groups. Group PBS (control group, n=10) got an injection of 50µl 0.1 vol% PBS-suspension, Group MI (Metal-ion, n=10) got an injection of 50µl metal ion suspension at a concentration of 200µg/l and Group MP (Metal-particles, n=10) got an injection of 50µl 0.1 vol% metal particle suspension each in the left knee. After incubation for 7 days the mice were euthanized and the extraction of the left knee ensued. Followed by immunhistochemical treatment with markers of inflammation that implied TNFα, IL-6, IL-1β, CD 45, CD 68, CD 3, we counted the positive cells in the synovial layer in the left knees by light microscopy, subdivided into visual fields 200× magnified. The statistical analysis was done with Kruskal-Wallis test and a post hoc Bonferroni correction.Introduction
Material and Methods
Wear is an important factor in the long term success of total knee arthroplasty. Therefore, wear testing methods and machines become a standard in research and implant development. These methods are based on two simulation concepts which are defined in standards ISO 14243-1 and 14243-3. The difference in both concepts is the control mode. One is force controlled while the other has a displacement controlled concept. The aim of this study was to compare the mechanical stresses within the different ISO concepts. Furthermore the force controlled ISO was updated in the year 2009 and should be compared with the older which was developed in 2001. A finite element model based on the different ISO standards was developed. A validation calculated with kinematic profile data of the same implant (Aesculap, Columbus CR) in an experimental wear test setup (Endolap GmbH) was done. Based on this model all three different ISO standards were calculated and analysed. Validation results showed Pearson correlation for anterior posterior movement of 0.3 and for internal external rotation 0.9. Two main pressure maximums were present in ISO 14243-1:2001 (force controlled) with 17.9 MPa and 13.5 MPa for 13 % and 48 % of the gait cycle. In contrast ISO 14243-1:2009 (force controlled) showed three pressure maximums of 18.5 MPa (13 % of gait cycle), 16.4 MPa (48 % of gait cycle) and 13.2 MPa (75 % of gait cycle). The displacement controlled ISO (14243-3:2014) showed two pressure maximums of 16.0 MPa (13 % of gait cycle) and 17.2 MPa (48 % of gait cycle). The adapted force controlled ISO of the year 2009 showed higher mechanical stress during gait cycle which also might lead to higher wear rates. The displacement controlled ISO leads to higher mechanical stress because of the constraint at the end of the stance phase of the gait cycle. Future studies should analyse different inlay designs within these ISO standards.
Metal on metal bearings are used especially in hip resurfacing. On the one hand, small bone preserving implants can be used. On the other hand recent studies found a variety of local and systemic side effects, for instance the appearance of pseudotumors, that are explained by pathologic biological reaction of the metal wear debris. The detailed mechanisms are still not understood until now. Thus it was the aim of this study to investigate the local reaction of metal wear particles and metal ions in a murine model. The hypothesis was that mainly metal ions provoke adverse histopathological reactions in vivo. Three groups, each with 10 Balb / c mice were generated. Group A: injection of a 50 µl metal ion suspension at a concentration of 200 µg / l in the left knee. Group B: injection of a 50 µl 0,1 vol% metal particle suspension into the left knee joint. Group C (control group): injection of a 50 µl of 0,1 vol% PBS-suspension in the left knee. Incubation for 7 days, followed by euthanasia of the animals by intracardiac pentobarbital. The left and right knee, the lungs, kidneys, liver and spleen were removed. Histologic paraffin sections in 2 microns thickness were made, followed by HE (overview staining) and Movat (Pentachrom staining) staining. The histologic analysis was a done by a light microscopic evaluation of the subdivided visual fields at 200× magnification.Introduction
Material and Methods
The complex process of inflammation and osteolysis due to wear particles still is not understood in detail. So far, Ultra-high-molecular-weight-polyethylene (UHMWPE) is the bearing material of choice in knee arthroplasty and revision knee arthroplasty, but there is a growing demand for alternative bearing materials with improved wear properties. Lately, increasing interest developed in the use of natural and carbon-fiber-reinforced-poly-ether-ether-ketones (CFR-PEEK). While there is a lack of data concerning the effects of CFR-PEEK particles on human tissue, the effects of such wear debris The aim of this study was to analyze human tissue containing CFR-PEEK as well as UHMWPE wear debris. The authors hypothesized no difference between the used biomaterials because of similar size parameters of the wear particles in a prior knee simulator study of this implant. Synovial tissue samples of 10 patients while knee revision surgery of a rotating hinge knee implant design (Enduro®, Aesculap, Germany) were achieved. The tibial inserts of this design were made from UHMWPE (GUR 1020), whereas the bushings and flanges are made of CFR-PEEK containing 30% polyacrylonitrile (PAN) based carbon fibers (PEEK-Optima LT1, Invibio Ltd. Thornton-Cleveleys, UK). In a prior The tissue was fixed with 4% paraformaldehyde, embedded in paraffin, sliced into 2 µm thick sections stained with hematoxylin and eosin in a standard process. A modified panoptical staining (preincubation in propylenglycol; >3h; 35°C) was also done which stained the UHMWPE particles turquoise. The study was approved by the ethics committee of the local university.Introduction
Methods and Materials
The complex cellular mechanisms of the aseptic loosening of total joint arthroplasties still remain not completely understood in detail. Especially the role of adherent endotoxins in this process remains unclear, as lipopolysaccharides (LPS) are known to be very potent modulators of the cell response on wear particle debris. Contributing factors on the LPS affinity of used orthopedic biomaterials as their surface roughness have to be investigated. The aim of this study was to evaluate the affinity of LPS on the surface roughness of different biomaterials Cubes with a side length from ultra-high-molecular-weight-polyethylene (UHMWPE), crosslinked polytethylene (XPE), carbon fibre reinforced poly-ether-ether-ketone (CFR-PEEK), titanium, titanium alloy, Polymethyl methacrylate (PMMA), implant steel (CoCr) and instrument steel (BC) were produced (figure 1). Cubes of each material have been produced with a rough and a smooth surface. Before the testings, all cubes and used materials were treated with E-Toxa-Clean(®) to eliminate pre-existing LPS on the used surfaces. The cubes were then fixed on the cap of a glass that was filled with a LPS solution with a concentration of 5 IE/ml. After 30 minutes the cube was removed and the LPS concentration in the supernatant was measured. The endotoxin content of each sample was evaluated by a Limulus Amoebocyte Lysate (LAL) - Test (Lonza, Verviers, Belgium). The detection level of endotoxin was set at < 0.005 EU/ml diluted 1/10.Introduction
Materials and methods
Despite consequent advancement in Total Knee Arthroplasty (TKA) up to 20% of patients are not satisfied after having been operated. Beside correct implantation, the design of the TKA-system is supposed to be a key factor of a successful TKA. Consequently it has been tried to restore natural kinematics by the design of the prosthesis. A medially stabilized design therefore is supposed to allow a lateral translation with a medial pivot. Our study compared posterior stabilized (PS) with medially stabilized (MS) TKA-design in terms of kinematics, femorotibial and patellofemoral contact patterns in vitro.Introduction
Objectives
A pain free motion of the patella after total knee arthroplasty (TKA) is still a challenge for surgeons and TKA-designers today. After TKA, the restricted guidance of the patella and kinematic alterations of the femorotibial joint results in increased retropatellar pressure and unphysiological patellar tracking. The alignment of the prosthetic components can influence patellofemoral stresses and tracking of the patella. The aim of this study was to demonstrate the consequences of different alignments of the tibial baseplate on patellar stress and knee kinematics. Different alignments of the tibial baseplate were simulated with five different UHMWPE-Inlets. Inserts with medial and lateral translation (±3mm; Figure 1A) as well as internal and external rotation (±3°; Figure 1B) were manufactured. Original inlays were used to define the neutral position. Eight human knee specimens without TKA were tested in a custom made knee rig. This rig mimics a loaded squat from approximately 20°−120° of flexion under six degrees of freedom in the knee joint. Retropatellar pressure (IScan, Tekscan, USA) as well as knee kinematics (CMS 20, Zebris, Germany) were recorded during squatting. Afterwards, TKA components were implanted in a neutral position via subvastus approach in tibia first technique. Each of the 5 tibial inlets was tested consecutively with the knee rig under the same conditions. Results were compared using mixed effects models with a random intercept per specimen. Component alignment as well as moving direction (flexion/extension) and flexion degree were defined as fixed effects in our model (SPSS, IBM, USA). After TKA in neutral position, retropatellar peak pressure increased by 0.71MPa (p<0.01), femorotibial rollback was reduced (−2.24mm; p<0.01) and the patella kinematics, in particular patella flexion (−2.02°; p<0.01) and rotation (−0.97°; p<0.01), were changed during squatting. Compared to the neutral position, internal rotation of the tibial baseplate increased retropatellar pressure by 0.20 MPa, while an external rotation provided a reduction of −0.24 MPa (p<0.01). In contrast a medialization or lateralization showed no effect on retropatellar pressure (p=0.09). Both, rotation and translation of the tibial baseplate influenced tibiofemoral kinematics significantly. A reduction of the femorotibial rollback was measured in external alignment (rotation and lateral translation; both p<0.01). An internal rotation showed more femoral rollback (0.93mm p<0.01). Patellar kinematics was changed primarily by component translation rather than rotation. A lateralisation of the tibial baseplate resulted in a medial shift of the patella by −0.43mm and vice versa (p<0.01). Rotation of the tibial baseplate had no influence on the patella shift (p=0.8) The findings in this study suggest that the alignment of the tibial baseplate influences patellar biomechanics significantly in vitro. An external rotation of the tibial baseplate decreased retropatellar pressure and patella kinematics tend more to the in situ situation of a natural knee. An internal alignment of the tibial baseplate seems to reconstruct natural tibiofemoral rollback in parts. However, studies (i.e. Nicoll et al.) show higher anterior knee pain by an internal alignment and a higher rollback after TKA might lead to higher wear.
To evaluate carbon-fiber-reinforced PEEK as alternative biomaterial for total disc arthroplasty a closed loop between biotribology (in vitro), application of sterile particle suspensions in the epidural space of rabbits and biological response in vivo was established. To prevent adjacent level degeneration in the cervical spine, total disc arthroplasty (TDA-C) remains an interesting surgical procedure for degenerative disc disease. Short- or midterm complications are migration, impaired post-operative neurological assessment due to artefacts in x-ray and MRI diagnosis and substantial rates of heterotopic ossification. The idea was to create a TDA-C design based on a polymer-on-polymer articulation to overcome these limitations of the clinically established metal-on-polyethylene designs. The objective of our study was to characterise the biotribological behaviour of an experimental cervical disc replacement made out of carbon-fiber-reinforced (CFR) PEEK and evaluate the biological response of particulate wear debris in the epidural space in vivo.Summary Statement
Introduction
Common cell based strategies for treating bone defects require time-consuming and expensive isolation and expansion of autologous cells. We developed a novel expedited technology creating gene activated muscle grafts. We hypothesized that BMP-2 activated muscle grafts provide healing capabilities comparable to autologous bone grafting, the clinical gold standard. Two male, syngeneic Fischer 344 rats served as tissue donors. Muscle tissue was harvested from hind limbs and incubated with an adenoviral vector carrying the cDNA encoding BMP-2. Bone tissue was harvested from the iliac crest. Segmental bone defects were created in the right femora of 12 rats and were filled with either BMP-2 activated muscle tissue or bone grafts. After 8 weeks, femora were evaluated by radiographs, microCT, and biomechanical tests. BMP-2 activated muscle grafts and autologous bone grafts resulted in complete mineralization and healing, as documented by radiographs and microCT. Bone volume in the muscle graft defects (33+/-12mm3) was similar to autologous bone graft defects (39+/-5mm3). Torque at failure of the two groups was statistically indistinguishable (240+/-115 Nmm vs. 232+/-108Nmm). In previous experiments we demonstrated that the large segmental defect model in this study will not heal with either empty defects or non-activated muscle grafts. Our findings therefore demonstrate that BMP-2 gene activation of muscle tissue effectively stimulates defect healing similar to autologous bone grafts.
Minimally invasive implanted unicompartmental knee arthroplasty (UKA) leads to excellent functional results. Due to the reduced intraoperative visibility it is difficult to remove extruded bone cement particles, as well as bone particles generated through the sawing. These loose third body particles are frequently found in minimally invasive implanted UKA. The aim of this study was to analyse the influence of bone and cement particles on the wear rate of unicompartmental knee prostheses in vitro. Fixed- bearing unicompartmental knee prostheses (n = 3; Univation F®, Aesculap, Tuttlingen) were tested with a customized four-station servo-hydraulic knee wear simulator (EndoLab GmbH, Thansau, Germany) reproducing exactly the walking cycle as specified in ISO 14243-1:2002. After 5.0 million cycles crushed cortical bone chips were added to the test fluid for 1.5 million cycles to simulate bone particles, followed by 1.5 million cycles blended with PMMA- particles (concentration of the third-body particles: 5g/l; particle diameter: 0.5- 0.7 mm). Every 500 000 cycles the volumetric wear rate was measured (ISO 14243-2) and the knee kinematics were recorded. For the interpretation of the test results we considered four different phases: breaking in- (during the first 2.0 million cycles), the steady state- (from 2.0 million to 5 million cycles), bone particle- and cement particle phase. Finally, a statistical analysis was carried out to verify the normal distribution (Kolmogorov-Smirnov test), followed by direct comparisons to differentiate the volumetric wear amount between the gliding surfaces (paired Student's t-test, p<0.05).Introduction
Material & Methods
Periprosthetic osteolysis depends on the biological activity of wear particles, but there is little known about the distribution of polyethylene wear particles (PE) in the surrounding joint tissue. The purpose of this study was to examine the localisation of wear particles of six different PEs, including four crosslinked polyethylenes (XPE), as well as their biological activity in the murine knee. Wear particles of 4 XPE- and 2 UHMWPE-inserts were isolated (knee joint simulator). For all groups the particles were similar in size and shape (mean diameter 0.3–05μm; 20nm-nucleopore-filter; ISO; n = 100.000).56 female Balb/c mice were randomly assigned to six treatment groups and one control group: control (PBS), XPE1 (3×30 kGy Gamma, annealed/sequential irradiated), XPE2 (95 kGy E-beam, remelted), XPE3 (65 kGy E-beam, remelted), XPE 4 (50 kGy Gamma, remelted), UHMWPE 1, UHMWPE 2. 50 μl of each particle suspension [(0.1% vol/vol (particle volume/PBS volume) after removal of endotoxin] were injected into the left knee joint. After 1 week the mice were killed and a histological and immunhistochemical analysis of the knee joints was done (IL-1, TNF-, ICAM-1). For the immunhistochemistry the articular cartilage, the bone marrow and the synovial membrane were evaluated semiquantitatively (Kruskal-Wallis test; all pairwise multiple comparison procedure; Bonferoni correction; significance level: p<0.05). All groups showed a thickened synovial layer with an increased cellular infiltration. The particles of XPE 1 and 2 were localised in the bone marrow as well as in the joint space. In contrast, the particles of XPE 3 and 4 were distributed in the synovial layer and in the bone marrow as well, but not in the joint space. The UHMWPE1 particles were mainly located in the bone marrow and joint space while the UHMWPE2 particles were mainly found in the bone marrow and the synovial layer. For all PE groups there was a higher cytokine expression compaired to control (p<0.0024) without any differences between the groups (bone marrow/synovial layer). The chondrocytes in the groups with XPE 1- and XPE 2-particles expressed more TNF- than in the control group and the other treatment groups (p = 0.000).Material and Methods
Results
Unicompartmental knee arthroplasty (UKA) in patients with isolated medial osteoarthritis of the knee is nowadays a standard procedure with good results, especially with the minimally-invasive approach. However, the survival rate of the unicompartmental knee prostheses is inferior to that of total knee prostheses. Therefore, further studying of UKA is still necessary. In most mobile bearing designs the femoral component has a spherical surface and therefore its positioning is not crucial. The role of the tibial slope in UKA has not been investigated so far. The manufacturers recommend tibial slopes with values between 10° positive slope and 5° negative slope. Most surgeons try to reconstruct the anatomical slope with a high failure by measuring the slope on x-rays. The aim of this study was to investigate the influence of the tibial slope on the wear rate of a medial UKA. In vitro wear simulation of medial mobile bearing unicompartmental knee prosthesis with a spherical femoral surface (Univation ®) was performed with a customized four-station servo-hydraulic knee wear simulator (EndoLab GmbH, Thansau, Germany) reproducing exactly the walking cycle as specified in ISO 14243–1:2002(E). The tibial tray was inserted with 2 different medial tibial slopes: 0°, 8° (n=3 for each group). The lateral tibial slope of the space-holder was not changed (0° for every group). We performed a total of 5 million cycles for every different slope, the gravimetric wear rate was determined gravimetrically using an analytical balance every 500 000 cycles according to the ISO 14243–2.Introduction
Materials and methods
In recent years UHMWP sutures have gained more and more popularity in shoulder surgery. They have an increased tensile strength but were shown to have a higher rate of knot slippage due to their smooth surface. There exist different testing protocols on suture testing in dry or in wet conditions. The purpose of this study was to gain some inside as to whether or not the knot security of sliding and non-sliding knots with different suture materials is influenced by dry or wet testing conditions. We tested five common suture materials, all of them USP #2. The PDSII, the Ethibond and three ultra high molecular weight polyethylene (UHMWPE) sutures: Fiber Wire, Orthocord and Herculine. As non-sliding knots we used Square knot and Revo knot and for sliding knots we used Fisherman and Roeder knot. 10 samples of each knot type were tested. In the first group knot tying and biomechanical testing were performed under dry conditions. In the second group the sutures were soaked in saline solution for 3 min. before knot tying and afterwards tested in saline bath. Cyclic loading was performed to simulate the physiological conditions. We started with a tensile load of 25 N. After 100 cycles, the load was increased to 50 N for another 100 cycles. Until suture rupture or knot slippage of 3 mm the tensile load was gradually increased by 25 N per 100 cycles. Under dry conditions 170 suture ruptures and 30 knot slippages were recorded. Under wet testing conditions 186 suture ruptures and 14 knot slippages were seen, which tested statistically significant. Failure by knot slippage (n=44) was seen under dry and saline testing conditions mainly with UHMWPE sutures particularly with Herculine suture. Knot slippage occured only with sliding knots. With the Ethibond suture no knot slippage was found regardless of the testing conditions and applied knot type. Across all knot types the UHMPE-sutures were significantly stronger in ultimate load to failure than Ethibond and PDSII under dry and wet testing conditions. Is the information we get from testing dry suture material reliable and helpful for our daily practice? Our study clearly showed: No! The mode of failure and the number of knot-failure differs significantly in wet testing conditions compared to dry testing. We found that the number of knot-failures is higher when tested with dry sutures than in wet testing conditions. The soaking of the suture material with fluid improves its “skid-resistance”. As we expected showed the UHMWP sutures with their smooth surface a high number of knot-failures compared to polyethylen suture Ethibond, which did not show a single knot-failure in dry or wet tesing conditions. The maximum failure load showed clearly the superiority of the new UHMWP suture material, with around 300 N being double as high as for polyethylen and polydioxone sutures.
The incidence of rotator cuff tears increases with age, thus the rotator cuff tear is often associated with osteoporotic or osteopenic bone in the proximal humerus, especially with female patients. For testing of fixation devices such as suture anchors used in rotator cuff repair often animal bones are used. They are easily to obtain, inexpensive and some have been found to be similar to human bone. But can we rely on the results drawn from these studies in our daily surgical practice? The purpose of this study was to compare the trabecular bone mineral density, the trabecular bone volume fraction and the cortical layer thicknes in the greater tubercle in different species to evaluate their infiuence on primary stability of suture anchors under a cyclic loading protocol representing the physiologic forces placed on rotator cuff repairs in vivo. We hypothezised that maximum pullout forces as well as the modes of failure are different for a suture anchors in different humeri. The available three different types of anchor fixation design (screw: Spiralok 5mm, Super Revo 5mm, press-fit: Bioknotless RC, wedging: Ultrasorb) were tested. The bone mineral density (BMD) of the humeri was measured by a 64-slice-computed tomography system. Each anchor was tested individually until failure. The sutures were pulled at 135° to the axis of the humeral shaft, simulating the physiological pull of the supraspinatus tendon. Starting with 75 N the tensile load was gradually increased by 25 N after everey 50 cycles until failure of the anchor fixation system occurred. The ultimate failure load, the system displacement after the first pull with 75 N and the mode of failure were recorded. The ultimate failure loads of each anchor were different in the human osteopenic, human healthy, ovine and bovine humeri. The statistical significancies for pull out forces between the anchors varied from species to species. The biomechanical testing of suture anchors for arthroscopic rotator cuff repair in ovine and bovine humeri does not give reliable data that can be transferred to the human situation. The significances between the suture anchors found in ovine and bovine humeri are different from the results in human humeri. When taking the impaired bone quality of older patients into account the results from ovine and bovine humeri are even less predictable. We found a positive correlation between maximum failure load and cortical layer thickness for the Super Revo and the Ultrasorb anchor. The ultimate failure load seems to depend mainly on the cortical thickness and on the subcortical trabecular bone quality.
Crosslinked polyethylene (XPE) was developed to reduce wear in hip and knee arthroplasty. Periprosthetic osteolysis depends on many factors including biological activity of wear particles. This study examines the relative inflammatory effect of different crosslinked polyethylenes compared to ultra-high-molecular-weight-polyethylene (UHMWPE) particles in vivo.
40 female Balb/c mice were randomly assigned to one of five treatment groups (according to the national guidelines of animal protection laws): control (n=8); XPE1 (95 kGy E-beam, remelted; n=8); XPE2 (65 kGy E-beam, remelted; n=8), XPE3 (3x30 kGy Gamma, annealed and sequential irradiated; n=8) and UHMWPE particles (n=8). 50 μl of the particle suspension were injected into the murine left knee under sterile conditions. The leukocyte–endothelial cell interactions and the synovial microcirculation were performed by intra-vital fluorescence microscopy one week after particle injection to assess the inflammatory reaction to the particles (by measuring the rolling fraction of leukocytes, the adherent cells and the functional capillary density (FCD)). Data analysis was performed using a computer-assisted microcirculation analysis system (Cap-Image). For the statistical analysis the Kruskal-Wallis test was used to determine differences within the groups, followed by an all pairwise multiple comparison procedure with a Bonferoni correction. The level of significance was set at p<
0.05.
The ultimate pull-out strenngth, the initial displacement in millimeters after the first pull with 75 N and the modes of failure were recorded.
In qRT-PCR a redifferentiation of human chondrocytes was shown by the transfer into diffusion-culture. Within passage 1 to 3 human chondrocytes which were cultured in monolayer lost the ability to express Collagen Type II but could regain it if they were transferred to diffusion-culture. At diffusion-culture chondrocytes showed the highest expression of Collagen type II at passage 1 when compared to monolayer or to pellet-culture.
Osteolsyis is one of the main reasons for revision of total joint replacements. The osteolytic reaction is influenced by dose, size (particles <
1μm are believed to be biologically more active) and shape of wear particles, so that low wear rates and biologically less active particles are required. In addition, in the knee a range of design and kinematic variables have to be considered as they can markedly influence wear regardless of the type of polyethylene used. Furthermore, UHMWPE (ultra-high-molecular-weight-polyethylene) fatigue occurs more frequently in the knee joint than in the hip joint due to its changing tribocontact areas combined with high weight bearing. This is why crosslinked polyethylene (XPE) is still controversially discussed for use in total knee prostheses.
Desmoid tumors are rare benign but aggressive lesions. They are characterized by bland-appearing fibroblasts, indistinct margins, and the ability of local invasion and recurrence. Though they are not cancer they may metastasize and can cause significant morbidity. Treatment is primarily surgical, although radiation or systemic therapy can be beneficial if surgery is not feasible. We retrospectively reviewed our patients since 1980 in respect to treatment modalities and outcome. Between 1980 and 2008 26 patients (16 m, 10 f) with desmoid tumours had been surgically treated. The mean age with diagnosis was 37 years (7 – 69 years). The mean age at surgery was 46 years (10 – 81 years). 17 of the patients had only one resection. In 6 patients two resections, in 2 three resections and in one patient four resections had to be performed. Only 7 patients achieved a R0-situation. In 9 patients adjuvant radiotherapy was used. Two patients had several courses of Vinblastine or MTX based chemotherapy, three patients had Sulindac or Tamoxifen, several other patients combinations of different NSARs. All patients were still alive, one patient developed metastatic disease from the initial lesion in the groin to the foot. After an average of 17 months (7 – 42 months) 11 patients showed recurrent disease. 13 patients are without recurrence after an average of more than 9 years. In 4 patient stable disease is seen without progression in 42 to 156 months (Ø 95 months). In conclusion desmoid tumours did show an inpredictable course of disease. Due to many alterations in treatment in the 28 years since the first patient of this study and the rareness of this disease no clear predicitve factor could be established. Remarkably no patient did need an amputation. A more detailed analysis regarding the dose effect of irradiated patients is intented.
Even though the operations are largely successful, complications after joint replacement surgery occur frequently. Approximately 10% of lower limb arthroplasties need surgical revision, of which 70% are due to loosening. The purpose of this study was to assess the feasibility of 18-fluorodeoxyglucose positron emission tomography (18FFDG–PET) in detecting septic and aseptic endoprosthetic loosening of hip and knee endoprostheses.
The sensitivity/specificity for infectious loosening in hip replacement arthroplasties was 67%/83%, in the knee 14%/89%.
Results: EndoTAG-1® treatment of AIA mice with developing or in established disease showed a strong attenuation of the course of the disease as well as a potent anti-inflammatory effect. Histological analysis of knee sections demonstrated a dramatic reduction of the pannus and infiltration of inflammatory cells. Enrichment of EndoTAG at the synovial vasculature of AIA mice was observed when compared with healthy mice. Treatment of AIA mice with EndoTAG-1® concomitant to disease induction showed a complete remission of the course of the disease as shown by a significant decrease of clinical scores compared to both control and Taxol® treated groups. A complete inhibition (98%) of neo-vascularisation was observed in the synovial vasculature of mice with AIA that were treated with EndoTAG-1® whereas Taxol® alone showed only 50% inhibitory effect. Rolling and adhesion of platelets were reduced to 53% (paclitaxel 5%) and 98% (paclitaxel 57%), respectively.
Over the last 10 years ACI (Autologous Chondrocyte Implantation) has become an important surgical technique for treating large cartilage defects. The original method has been improved by using cell seeded scaffolds for implantation. The aim of our prospective study was to evaluate the efficiency of a matrix based ACI (MACI) with a collagen type I scaffold for repairing large cartilage defects of the knee. We present the clinical and radiological results of 22 pts. one year after collagen scaffold based ACI. Out of 39 pts. treated with ACI for cartilage defects of the knee 22 had reached the one year follow up. We documented preoperatively and postoperatively (3, 6 and 12 months) the clinical situation with the IKDC Knee Examination Form. MRI scans were evaluated at all time points. 41% of the pts. were female, 59% male. The average age was 33 yrs. (min:15; max:49), the average BMI 25,4 (min:19; max:36). One third of the cartilage defects were localized retropatellar, the remaining on the medial or lateral femoral condyle. The average defect size was 5.7 cm2. In about 75% of the cases an additional surgical procedure was performed (ACL-reconstruction, lateral release, meniscal surgery). One major complication (a deep wound infection) occured. The IKDC score improved over time during follow up significantly. Patients with retropatellar defects have a poorer outcome compared to femoral defects. The MRI showed an improvement of the implanted scaffold over time as well. The present study confirms the benefits of MACI in young patients with large cartilage defects of the knee. The matrix based ACI is a surgically less demanding technique then the traditional ACI. We expect a good long term outcome from MACI comparable to that of traditional ACI.
Irreparable tendon ruptures constitute a grave clinical problem. Especially for large rotator cuff tears, there often is no primary causal therapy available. As a sad result, the development of a rotator cuff tear arthropathy is more often than not inevitable. Our study investigates the effects of scaffold based tendon regeneration with special focus on mesenchymal stem cells in a rat model. We used ‘native’ bone marrow stromal cells and cultivated mesenchymal stem cells from male rats that were implanted into female rats. As scaffolds polyglycol acid (PGA) and a collagen I were used. A full-thickness-defect of 2–3 mm in the middle third of the rats achilles tendon was created, which was then filled, with either cell-seeded or not cell-seeded scaffolds and, due to the low primary stability of the scaffolds, fixed with a 4-0 suture. After 12 weeks, a DNA PCR was conducted to verify the existence of male Y-chromosomes in the female regenerated tissue. We determined the maximum tensile load of the regenerated tissue and also did a histological evaluation. Macroscopically the regenerated tendons were much bigger in diameter, much firmer and also much less elastic than a normal tendon. In the ‘mesenchymal stem cells’ group the implanted cells could be clearly identified after 12 weeks by DNA PCR. The collagen I scaffold yielded better results in the biomechanical study than the PGA scaffold. No evidence of positive influence of the cells on the mechanical stability of the regenerated tissue was found. Collagen I and the use of BMSC histologically lead to increased ossification of the regenerated tissue. In the PGA scaffold group a significant inflammatory reaction was found. Both scaffold/cell combination seem to be unsuitable for tendon replacement. in-vitro studies on the influence of scaffold material on cell differentiation needs to be done.
One of the recently introduced anchors is the absorbable suture anchor BIOKNOTLESS-RC, a press-fit anchor whose special feature is the knotless reconstruction of the ruptured rotator cuff. We compared the new knotless anchor BIOKNOTLESS-RC with established anchors. The absorbable pressfit anchor BIOKNOTLESS-RC (DePuyMitek, Raynham, MA, USA), the titanium screw anchor SUPER-REVO 5mm and the tilting anchor ULTRASORB (both ConmedLinvatec, Largo, FL, USA) were tested 12 times in the greater tuberosity of human cadaveric humeri (mean age: 74 years). They were inserted according to the manufacturers instructions with the supplied suture material. An incremental cyclic loading was performed, starting with 75N. Until failure the tensile load was increased by 25N after every 50 cycles. The ultimate failure loads, the anchor displacements and the modes of failure were recorded. The anchor displacement of the BIOKNOTLESS-RC (15.3mm) after the first cycle with 75N was significantly higher than with the two others (SUPER-REVO 2.1mm, ULTRASORB: 2.7mm). The ultimate failure loads of the tested anchors were comparable: BIOKNOTLESS-RC 150N, SUPER-REVO 150N, ULTRASORB 151N (p>
0,05). Rupture of the suture material at the eyelet occurred more frequently with the SUPER-REVO. BIOKNOTLESS-RC and ULTRASORB showed a tendency towards anchor pullout. Our results do not confirm the higher pullout strength of metal anchors, which was found in other studies. Knotless anchors facilitate surgery by eliminating the technically challenging step of arthroscopic knot tying. The disadvantage of the BIOKNOTLESS-RC is its unsatisfactory primary stability. Its initial displacement of a mean of 15.3 mm is clinically significant and jeopardizes the rotator cuff repair. Because of the high initial displacement and the possible gap formation between tendon and bone, the use of the BIOKNOTLESS-RC in a zone of minor tension, for instance as a second-row anchor in double row technique only is recommend.
Periprosthetic osteolysis, caused in a chronic inflammatory adverse reaction to wear particles in the surrounding tissues, is one of the major reasons for revision arthroplasty so that articulating surfaces with low wear rates are required. Compared with conventional ultra high molecular weight polyethylene (UHMWPE), highly crosslinked polyethylene (HXLPE) shows a reduced wear rate in a hip simulator. The crosslinking process which is achieved by gamma or electronic radiation, followed by heat treatment either above the melting point (remelting) or below (annealing), reduces the mechanical properties of UHMWPE, particularly its fatigue strength. UHMWPE fatigue occurs more frequently in the knee than in the hip due to its higher contact stresses. This is why HXLPE is still controversially discussed for use in total knee prostheses. We have examined the wear behaviour of different HXLPEs [one cruciate-retaining (CR; sequential irradiation and annealing), one ultra-congruent (remelting), one CR (remelting)], compared with conventional UHMWPE in a knee simulator (Stallforth-Ungethuem). In the fixed bearing knee recommended from the manufacturer the wear rates [gravimetric (mg/year); volumetric (mm3/year)] were determined according to the ISO standard and the wear mechanism was analysed by means of a scanning electron microscope. All insert showed signs of abrasion, scratching and wear polishing, but no traces of fatigue reactions. All HXLPEs produced lower (p<
0.05) wear rates (0.47–3.3 mg/year; 0.5–3.5 mm3/year) than the UHMWPE (8.1–9.1 mg/year; 8.6–9.7 mm3/year), the inserts of HXLPE manufactured by sequential irradiation and annealing showed the lowest wear rates (p<
0.05) overall. Due to the reduced wear rates without any fatigue symptoms, we conclude that HXLPE is suitable for total knee prostheses and a monitored clinical investigation can be recommended. HXLPE manufactured by sequential irradiation and annealing seems to produce still lower wear rates than those manufactured by remelting, at least when used in total knee prostheses.
Absorbable suture anchors have become more and more important in rotator cuff surgery due to their easy revisability. In osteoporotic bone however they are thought to be of minor primary stability. Purpose of the present study was to compare different absorbable and non-absorbable suture anchors in their pullout strength depending on bone density The absorbable screw-anchor SPIRALOK5mm (DePuyMitek, Raynham, MA, USA), the titanium screw-anchor SUPER-REVO5mm and the tilting-anchor ULTRASORB (both ConmedLinvatec, Largo, FL, USA) were tested, each anchor representing a different material and design. On the basis of bone density measurement by CT-scans a healthy (mean-age. 42 years) and a osteopenic (mean-age: 74 years) group of cadaveric human humeri were formed. Each anchor was inserted in the greater tuberosity six times. They were inserted according to the manufacturers instructions with the supplied suture material. An incremental cyclic loading was performed, starting with 75N. Until failure the tensile load was increased by 25N after every 50 cycles. The ultimate failure loads, the anchor displacements and the modes of failure were recorded. In the non-osteopenic bone group, the absorbable SPIRALOK achieved a significantly better pullout strength (mean: 274N) than the titanium screw-anchor SUPER-REVO (mean: 188N) and the tilting-anchor ULTRASORB (mean: 192N). In the osteopenic bone group no significant difference in the pullout strength was found. The failure mechanisms, such as anchor pullout, rupture at eyelet, suture breakage and breakage of eyelet, varied between the anchors. In the osteopenic group the number of anchor pullouts clearly increased. The present study demonstrates that absorbable suture anchors do not have lower pullout strengths than metal anchors. Depending on their design they can even outmatch metal anchor systems. The results of our study suggest that the anchor design has a crucial influence on primary stability, whereas the anchor material is less important.
Cyclic loading was performed, as it was considered the best way to simulate the postoperative conditions. The maximum tensile strength, the failure mode, and the displacement of the fixation device (system displacement) under load at the first cycle of 75 N and at the maximum tensile strength were recorded.
The absorbable Spiralok 5 mm screw anchor showed the highest failure load with a mean of 223 N. The failure loads of the remaining anchors were similar and ranged from a mean of 169 N for the Super Revo 5 mm, over a mean of 173 N for the Ultrasorb RC anchor to a mean of 188 N for the Bioknotless anchor. Among these anchors the differences were not significant. Only the Spiralok 5 mm screw showed a significantly higher failure load when compared with the Super Revo 5 mm screw. The displacement of the various systems showed significant differences. The displacement of the Bioknotless anchor showed after the cycle with a tensile strength of 75 N a mean displacement of 13.8 mm, which was significant when compared with the remaining anchors.
Even though the operations are largely successful, complications after joint replacement surgery occur frequently. Approximately 10% of lower limb arthroplasties need surgical revision, of which 70% are due to loosening. The purpose of this study was to assess the feasibility of 18-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) in detecting septic and aseptic endoprosthetic loosening of hip and knee endoprostheses.
The sensitivity/specificity for infectious loosening in hip replacement arthroplasties was 67%/83%, in the knee 14%/89%.
Many pateints showed an extented survival despite disseminated disease with a high and quality of life. Radical resection as tried in a few patients did not proof to be beneficial regarding the prognsotic effect.
In an experimental study in rabbits, bone and cartilage regeneration could be achieved with a new class of resorbable bio-implants. These implants consist of an open porous structure made from polylacitdes and an open porous fleece made from polyglactin/polydioxanon. Both layers were not separated from each other, thus allowing mesenchymal cells to penetrate freely from bone into both the bone substitute and the cartilage substitute layer. It could be shown that ostochondral defects of 4mm diameter and 6mm depth in the condyle of the knee of rabbits healed by the process of mesenchymal cell differentiation into osteocytes and chondrocytes triggered by mechanical load induction only. Evaluation of the newly formed cartilage by light microscopy and immunohistology showed hyaline like features. However, in many clinical cases chondral defects occur without substantial accompanying bone loss. In these situations, reconstruction of the cartilage defects only seems to be sufficient. However, fixation of such fleeces onto the bone is difficult. On one hand, adherence of the fleece to the underlying bone is crucial, on the other hand an open connection from the bone to the fleece must be accomplished in order to allow mesenchymal cells to penetrate the fleece. Therefor, any kind of glue fixation is not appropriate. To overcome this problem, a new fixation method was developed which allows a safe connection of the fleece onto the bone while providing an open contact of the fleece to the bone marrow for unhampered migration of mesenchymal cells. The new “Cartilage patches” consist of a fleece (serving as the cartilage substitute layer) made from polyglactin/polydioxanon which had proven its applicability in the above mentioned experiments. Fixation of fleece was achieved by “darts” which were glued onto the fleece. The darts were made from polylacitdes, thus providing sufficient mechanical stability in the bone. During operation, small holes are cut into the bone by a special instrument. The holes are located in such a way that the darts of the cartilage patch fit into them, such resulting in a stable fixation of the fleece onto the underlying bone. Blood containing mesenchymal cells from the bone marrow is able to flow from the holes into the fleece. In a biomechanical analysis the adherence of the cartilage patches were tested with respect to shear resistance and pull-out stabillity. The results of the tests show that the new cartilage patches withstand the mechanical stress exerted onto articular surfaces and can serve as a new class of cartilage substitute layers. In an animal experiment the applicability of the cartilage patches in reconstruction of cartilage defects in the knee joint of sheep will be proven.