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Introduction. Increasing interest developed in the use of carbon-fiber-reinforced-poly-ether-ether-ketones (CFR-PEEK) as an alternative bearing material in knee arthroplasty. The effects of CFR-PEEK wear in in vitro and animal studies are controversially discussed, as there are no data available concerning human tissue. 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. Methods and Materials. In 10 patients during knee revision surgery of a rotating-hinge-knee-implant-design, synovial tissue samples were achieved (tibial inserts: UHMWPE; bushings and flanges: CFR-PEEK). One additional patient received revision surgery without any PEEK components as a control. The tissue was paraffin-embedded, sliced into 2 μm thick sections, and stained with hematoxylin and eosin in a standard process. A modified panoptical staining was also done. Results. A “wear-type” reaction was seen in the testing and the control group. In all samples, the UHMWPE particles were scattered in the tissue or incorporated in giant cells. CFR-PEEK particles were seen as conglomerates and only could be found next to vessels. CFR-PEEK particles showed no giant-cell reactions. In conclusion, the hypothesis has to be rejected. UHMWPE and PEEK showed a different scatter-behavior in human synovial tissue. [ABSTRACT FROM AUTHOR]

Total knee arthroplasty (TKA) is a successful procedure for osteoarthritis. However, some patients (19%) do have pain after surgery. A finite element model was developed based on boundary conditions of a knee rig. A 3D-model of an anatomical full leg was generated from magnetic resonance image data and a total knee prosthesis was implanted without patella resurfacing. In the finite element model, a restarting procedure was programmed in order to hold the ground reaction force constant with an adapted quadriceps muscle force during a squat from 20° to 105° of flexion. Knee rig experimental data were used to validate the numerical model in the patellofemoral and femorotibial joint. Furthermore, sensitivity analyses of Young’s modulus of the patella cartilage, posterior cruciate ligament (PCL) stiffness, and patella tendon origin were performed. Pearson’s correlations for retropatellar contact area, pressure, patella flexion, and femorotibial ap-movement were near to 1. Lowest root mean square error for retropatellar pressure, patella flexion, and femorotibial ap-movement were found for the baseline model setup with Young’s modulus of 5 MPa for patella cartilage, a downscaled PCL stiffness of 25% compared to the literature given value and an anatomical origin of the patella tendon. The results of the conducted finite element model are comparable with the experimental results. Therefore, the finite element model developed in this study can be used for further clinical investigations and will help to better understand the clinical aspects after TKA with an unresurfaced patella. [ABSTRACT FROM PUBLISHER]

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Objectives: Cationic lipid complexes bind to angiogenic endothelial cells of solid tumours and microvessels of chronic inflammatory tissue. Methotrexate (MTX) is one of the drugs used in the therapy of rheumatoid arthritis (RA); it is applied systemically but can have serious side-effects. The aim of this study was to investigate the impact of MTX encapsulated in cationic liposomes (EndoMTX) in comparison to treatment with free MTX.Method: We used an antigen-induced arthritis (AiA) model and investigated the leucocyte- and platelet-endothelial cell interaction in arthritic female C57/Bl6 mice and in healthy controls. The arthritic animals were divided into four different groups receiving either trehalose, free MTX, EndoMTX placebo, or EndoMTX. These parameters and functional capillary density (FCD) were measured and assessed by intravital microscopy (IVM). We controlled clinical parameters such as the knee joint diameter (KJD) throughout the observation period.Results: Animals treated with EndoMTX showed a significant and superior reduction in leucocyte- and platelet-endothelial cell interaction, FCD, and KJD. Free MTX or empty liposomes also showed a reduction in these parameters but not to a significant level. FCD decreased in the EndoMTX group in comparison to using free drugs or empty carrier-like liposomes.Conclusions: This study demonstrates the advantage of using MTX encapsulated in cationic liposomes in contrast to free and generic MTX, with a higher efficacy in anti-inflammatory and anti-angiogenic abilities. Targeting with cationic liposomes may be a promising treatment option and should be elucidated in further experiments regarding dose reduction and side-effects due to MTX usage. [ABSTRACT FROM AUTHOR]

Objectives: The use of statins in the prevention and treatment of cardiovascular diseases is well established. Their use as anti-inflammatory and immunomodulatory agents in the treatment of rheumatoid arthritis (RA) has also been investigated, with several clinical and experimental studies indicating an anti-inflammatory effect of statins for RA, but other studies showing no effect or even the opposite. The current study was designed to examine the effect of simvastatin in an in vivo murine model of arthritis using intravital microscopy. Method: We assigned four groups (n = 7, female C57Bl6 mice), two with and two without antigen-induced arthritis (AiA), from which one of the non-AiA groups and one of the AiA groups were treated with simvastatin 40 mg/kg i.p. daily for 14 consecutive days after induction of arthritis. Platelet- and leucocyte-endothelial cell interaction was assessed by measurement of rolling and adherent fluorescence-labelled platelets and leucocytes, functional capillary density (FCD) was evaluated, and knee joint diameter was determined as a clinical parameter. Results: In arthritic mice treated with simvastatin, a significant reduction in platelet- and leucocyte-endothelial cell interaction was observed in comparison to arthritic mice treated with vehicle. In addition, a significant reduction in FCD was seen in arthritic mice treated with simvastatin, along with a reduction in knee joint swelling of the AiA mice. Conclusions: Treatment of AiA mice with simvastatin showed significant reductions in platelet- and leucocyte-endothelial cell interactions, in FCD, and in the swelling of the knee joint. These results support the hypothesis of the anti-inflammatory effects of statins in the treatment of RA. [ABSTRACT FROM AUTHOR]

Wear of polyethylene causes loosening of joint prostheses because of the particle mediated activity of the host tissue. It was hypothesized that conventional and crosslinked polyethylene particles lead to similar biological effects around the knee joint in vivo as well as to a similar particle distribution in the surrounding tissues. To verify these hypotheses, particle suspensions of six different polyethylene materials were injected into knee joints of Balb/C mice and intravital microscopic, histological and immunohistochemical evaluations were done after 1 week. Whereas the biological effects on the synovial layer and the subchondral bone of femur and tibia were similar for all the polyethylenes, two crosslinked materials showed an elevated cytokine expression in the articular cartilage. Furthermore, the distribution of particles around the joint was dependent on the injected polyethylene material. Those crosslinked particles, which remained mainly in the joint space, showed an increased expression of TNF-alpha in articular cartilage. The data of this study support the use of crosslinked polyethylene in total knee arthroplasty. In contrast, the presence of certain crosslinked wear particles in the joint space can lead to an elevated inflammatory reaction in the remaining cartilage, which challenges the potential use of those crosslinked polyethylenes for unicondylar knee prostheses. [ABSTRACT FROM AUTHOR]

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A cellular and receptor mediated response to ultra-high-molecular-weight-polyethylene (UHMWPE) wear particles results in a release of proinflammatory cytokines and induces an inflammatory reaction causing osteolysis in total joint replacement. This investigation offers insight into the toll-like receptor (TLR) mediated activation by polyethylene wear particles in the synovial layer of mice. We hypothesized that, similar to recent in vitro results, UHMWPE particles lead to an upregulation of TLR 1 and 2 and TLR 4 in vivo in the synovial tissue of mice as well. Therefore, UHMWPE particles were generated in a common knee simulator according to the ISO standard, separated by acid digestion and determined by scanning electron microscopy. Endotoxin was removed using a method based on ultracentrifugation. A particle suspension (50 μl; 0.1 vol./vol.%) was injected into the left knee joint of female Balb/c mice (n = 8). In a control group, phosphate-buffered saline was injected into the left knee of Balb/c mice (n = 8). The mice were sacrificed after 7 days. Immunohistochemical staining was performed with TLR 1, 2 and 4 polyclonal antibodies for Balb/c mice and evaluated by light microscopy. The particle-stimulated group showed a thickened synovial layer, an increased cellular infiltration and a TLR 2-upregulation in the synovial layer compared to the control group. An increased expression of TLR 1 and TLR 4 could not be demonstrated. These results indicate a mainly TLR 2-induced inflammation to polyethylene wear debris in the synovial layer of mice. [ABSTRACT FROM AUTHOR]

Due to their mechanical properties, there has been growing interest in poly-ether-ether-ketone (PEEK) and its composites as bearing material in total and unicompartmental knee arthroplasty. The aim of this study was to analyze the biological activity of wear particles of two different (pitch and PAN) carbon-fiber-reinforced- (CFR-) PEEK varieties in comparison to ultra-high-molecular-weight-polyethylene (UHMWPE) in vivo. The authors hypothesized no difference between the used biomaterials. Wear particle suspensions of the particulate biomaterials were injected into knee joints of Balb/c mice, which were sacrificed after seven days. The cytokine expression (IL-1β, IL-6, TNF-α) was analyzed immunohistochemically in the synovial layer, the adjacent bone marrow and the articular cartilage. Especially in the bone marrow of the two CFR-PEEK varieties there were increased cytokine expressions compared to the control and UHMWPE group. Furthermore, in the articular cartilage the CFR-PEEK pitch group showed an enhanced cytokine expression, which could be a negative predictor for the use in unicondylar knee systems. As these data suggest an increased proinflammatory potential of CFR-PEEK and its composites in vivo, the initial hypothesis had to be refuted. Summarizing these results, CFR-PEEK seems not to be an attractive alternative to UHMWPE as a bearing material, especially in unicompartmental knee arthroplasty. [ABSTRACT FROM AUTHOR]

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Purpose: Before elective operations, particularly orthopaedic surgery, national guidelines in Germany recommend testing for human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) to reduce the risk of transmission of the virus through a needlestick or cutting injury. Such testing is expensive. The number of new and unknown diagnoses of viral infections that can be detected by routine screening has not yet been evaluated. Methods: The aim of our department of orthopaedic surgery is to screen every adult patient listed for an operation for HBV, HCV and HIV. We retrospectively analysed the number of operations in this single centre from 2001 to 2010, correlated this number with the total number of screens and calculated the number of newly diagnosed infections. An additional cost:benefit ratio was calculated. Results: A total of 20,869 operations were performed by the department between 2001 and 2010. After exclusion of all interventions in children and all patients who had multiple operations, 15,482 patients remained. Test results were found for 10,011 of these patients during this period (screening rate 65 %). Of those screened, in only four cases (0.4 ‰) was a previously unknown infection detected. Conclusions: Two-thirds of the patients included in our study actually underwent screening; this rate was lower than expected. The incidence of newly detected infections was low, putting the benefit of a routine preoperative screening for HBV, HCV and HIV into question. From an economic point of view the low detection rate is a strong argument in favour of omitting routine preoperative screening. Screening only those patients with risk factors may be as safe as screening every patient and would help reduce costs. [ABSTRACT FROM AUTHOR]

In order to investigate cell-based tendon regeneration, a tendon rupture was simulated by utilizing a critical full-size model in female rat achilles tendons. For bridging the defect, polyglycol acid (PGA) and collagen type I scaffolds were used and fixed with a frame suture to ensure postoperatively a functional continuity. Scaffolds were seeded with mesenchymal stem cells (MSC) or tenocytes derived from male animals, while control groups were left without cells. After a healing period of 16 weeks, biomechanical, PCR, histologic, and electron microscopic analyses of the regenerates were performed. Genomic PCR for male-specific gene was used to detect transplanted cells in the regenerates. After 16 weeks, central ossification and tendon-like tissue in the superficial tendon layers were observed in all study groups. Biomechanical test showed that samples loaded with tenocytes had significantly better failure strength/cross-section ratio ( P < 0.01) compared to MSC and the control groups whereas maximum failure strength was similar in all groups. Thus, we concluded that the application of tenocytes improves the outcome in this model concerning the grade of ossification and the mechanical properties in comparison to the use of MSC or just scaffold materials. [ABSTRACT FROM AUTHOR]

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Purpose: In the last 15 years, vertebroplasty and kyphoplasty have become established operative procedures for treating osteoporotic vertebral-body fractures and vertebral bodies afflicted with metastases. These procedures are quickly performed with few personnel and material resources and have a low rate of complications. However, cases of neurological impairment are reported in the scientific literature. We analysed whether potentially harmful heat is radiated/conducted by the polymerisation temperature of polymethylmethacrylate (PMMA) bone cement in the spinal canal.Methods: We performed vertebroplasty on 25 vertebral bodies and measured the temperature distribution during polymerisation of bone cement within the spinal canal using heat probes placed in the respective areas. The vertebral bodies were located in a circulating water bath at 37°C.Results: During polymerisation of the bone cement, a temperature rise was measured. The peak temperature was reached after few minutes. Temperature curves differed; a maximum temperature of up to 43.16°C was detected for a few seconds only.Conclusion: When vertebroplasty is performed correctly, there is no temperature development that could eventually damage the spinal cord or spinal nerves. [ABSTRACT FROM AUTHOR]

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Copyright of Der Orthopäde is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The posterior tibial slope has a huge influence on the kinematics of the knee. In several orthopedic interventions such as high tibial osteotomy and unicondylar or bicondylar knee replacement changing, the tibial slope can result in altered knee mechanics. Therefore, an exact preoperative measurement of the posterior tibial slope is mandatory. Several methods are used on conventional radiographs and CT scans, but until now there is no standard validated method. The aim of this study was to compare several methods and imaging techniques to measure the posterior tibial slope and to establish a standard and reliable measurement method by radiography. Methods: Fourteen knees (seven cadavers) were scanned by a 64-slice CT, a 3T-MRI, and true lateral radiographs were performed. The anatomical references (TPAA = tibial proximal anatomical axis; ATC = anterior tibial cortex; PTC = posterior tibial cortex) and the new computed reference (MPA = mean of PTA and ATC) were compared by short as well as long radiographs, CT scan and MRI. The influence of a malrotation in radiographs of the knees was also analyzed. Results: CT scan and MRI are suitable for the measurement of the medial and lateral posterior tibial slopes, the results of the radiographs varied depending on the method used. The new method (MPA) showed the best correlation to the CT scan ( r = 0.997), even on short radiographs (10 cm distal the joint line). Conclusion: The measurement of the posterior tibial slope on a short lateral radiograph using the MPA is a reliable method and should be established as a standard. Level of evidence: Diagnostic study, Level II. [ABSTRACT FROM AUTHOR]

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Patients with multiple myeloma are often treated surgically as though they have bone metastases. Due to major differences in oncological therapy and comparatively long survival times these patients should be considered separately. Seventy-five multiple myeloma patients were treated surgically (83 interventions) for skeletal complications of the disease. Location and dissemination, symptoms, method of surgery, complications, recurrence and survival time were evaluated retrospectively. Most of the lesions were in the axial skeleton or the proximal extremities apart from one distal lesion of the fibula, and most surgery was performed in the spine (35 patients). The mean follow-up of patients was 5.4 years (range 1-25 years). Survival proved to be very favourable (37% at five years). Patients with a single bone lesion, a negative bone marrow biopsy, no paraproteinaemia in serum or a Salmon-Durie-stage I had a better survival probability. Surgical treatment in patients with multiple myeloma was mostly limited to a palliative approach but survival time was better (37% at five years) than in patients with metastatic bone disease which has to be considered in their surgical treatment. [ABSTRACT FROM AUTHOR]

Background: Crosslinked polyethylene (XPE) was developed to reduce the wear rate in hip as well as knee arthroplasty. The crosslinking process reduces the mechanical properties of ultra-high-molecular-weight polyethylene (UHMWPE), particularly its fatigue strength. UHMWPE fatigue occurs more frequently in the knee than in the hip joint due to its changing tribocontact areas (TCAs) combined with high weight bearing. This is why XPE is still controversially discussed for use in total knee arthroplasty. Therefore, the potential advantage of using XPE in the knee was analysed in a simulator study with a focus on potential fatigue wear mechanisms. Methods: Three different kinds of XPE and one conventional UHMWPE were tested over 5 million cycles in fixed-bearing knee designs. The TCAs were examined by replicas, and their extent was measured. The wear mechanism was analysed by scanning electron microscopy. Results: The extent of the TCAs was less than 5% for all XPEs, whereas 35% for the conventional UHMWPE. Fatigue wear mechanisms were not observed. Conclusion: The measured small extent of the TCAs as a predictor of a low wear rate without any fatigue wear mechanism shows a possible advantage for the use of XPE even in knee arthroplasty. [ABSTRACT FROM AUTHOR]

Helium (He) is present in fusion reactor wall materials, and its effect on radiation damage must be taken into account. The effect of He on displacement cascades in tungsten (W) has been studied using molecular dynamics simulations. Three different W-W potentials were compared and found to differ, especially for the clustering of the vacancies formed in the cascades. While there are differences in the amounts of damage depending on the potential, the overall effect of He in interstitial positions was to increase the amount of damage, while He in substitutional positions reduces it, due to the effect He has on the recombination of tungsten interstititals. [ABSTRACT FROM AUTHOR]

In revision hip arthroplasty with bone defects of the proximal femur, a wellestablished treatment method is reconstruction with impacted allograft spongiosa chips and cemented implantation of a polished stem. Building on this principle of impacted bone grafting, a femoral implant, which is suited to uncemented hip arthroplasty as well as for uncemented revisions, was designed. This so-called compression-rotation stem (CR stem) is collarless and has flanks which compress the impacted bone chips during implantation and thereby increase the rotational stability. To evaluate the primary stability of this new shaft after impaction grafting, the micromotion was determined using six motion transducers. Under physiological loading conditions with simulation of the muscle activities at the proximal femur the application was dynamically loaded for 15 000 cycles with 1000±500N and afterwards for 5000 cycles with 1300±1000 N. Uncemented CR stems and the control Exeter stems were implanted in a standardized manner according to the X-Change method. Therefore they were implanted into artificial femora that had been previously resected, hollowed, and filled with impacted human spongeous bone allograft to simulate bone defects. Subsequently, the femora were loaded under identical conditions and the micromotions measured. In the majority of the implantations, no significant differences could be found. In conclusion, similar clinical results for the two stems should be expected. [ABSTRACT FROM AUTHOR]

The minimally invasive implantation of unicompartmental knee arthroplasty (UKA) leads to excellent functional results, but due to the reduced intraoperative visibility the removal of excessive cement may be difficult. In a retrospective study we assessed radiologically the incidence of loose and excess bone cement in 120 UKAs and correlated it to the thickness of the tibial cement layer. In 25 cases loose or attached excess cement was seen. Two of these patients with loose cement bodies required revision surgery. An additional 2 patients not operated at our institution required revision because of pain and loss of motion. The average thickness of the tibial cement layer was 3.1 (1.7–5.0) mm in all the patients. But it was significantly higher in the group with excess cement bodies [3.3 (2.3–5.0) mm] compared to the group without excess cement [3.0 (1.7–4.1) mm] ( P < 0.05). Symptomatic free cement bodies need to be removed immediately, if necessary arthroscopically, in order to avoid damage to the implants. To avoid this problem in minimally invasive UKA, intraoperative fluoroscopy, a dental mirror or a nerve hook seem to be useful tools to identify and remove loose or excess cement. [ABSTRACT FROM AUTHOR]

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A new femoral stem was developed with a design that leads to compression of cancellous bone in the calcar region which results in proximal loading. The cross-sectional design of the implant provides rotational stability. In the first clinical investigation ten patients underwent uncemented total hip arthroplasty between January 1999 and May 1999 using the CR-stem® (Implantcast GmbH, Buxtehude, Germany). Results were investigated using the Harris-hip-score (HHS) and antero-posterior and lateral radiographs. Migration was evaluated with the EBRA-FCA-method with a follow-up of 7 years. We demonstrated a mean subsidence rate of 2.23 ± 1.13 mm 7 years after implantation thus providing basic data for extensive testing in a clinical environment. As small subsidence rates are regarded as predictor for superior long-term results in uncemented total hip arthroplasty according to the literature, the CR-stem shows promise for excellent long-term results. [ABSTRACT FROM AUTHOR]

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Objective: Platelets are thought to participate in the pathogenesis of chronic inflammatory diseases such as rheumatoid arthritis (RA). We showed recently an in vivo increase in platelet-endothelial cell interactions in mice with antigen-induced arthritis (AiA). The underlying mechanisms are not yet clear. The aim of this study was to investigate the impact of P-selectin in AiA by means of intravital fluorescence microscopy (IVM). Methods: C57/Bl6 mice and P-selectin-deficient mice were divided into four groups (n = 7; control/AiA per strain). The extent of AiA was assessed by measuring knee joint swelling and by histological scoring. Rolling and adherent fluorescence-labelled platelets and leucocytes were investigated by IVM. Results: In arthritic P-selectin-deficient mice (rolling: 0.05±0.01; adherent: 130±20 mm-2), compared to arthritic C57/Bl6 mice (rolling: 0.20±0.04; adherent: 1910±200 mm-2), platelet interaction was significantly reduced (p<0.05) and reached the level of both control groups without AiA. In addition, interaction of leucocytes in P-selectin-deficient arthritic animals (rolling: 0.12±0.06; adherent: 387±37 mm-2) was significantly decreased in comparison to arthritic C57/Bl6 animals (rolling: 0.21±0.06; adherent: 1492±284 mm-2; p<0.05). Swelling of the knee joint and histological scoring were reduced in arthritic P-selectin-deficient mice compared to arthritic C57/Bl6 mice. Conclusion: We have demonstrated for the first time in vivo a significant decrease in the interaction of platelets and leucocytes with the endothelium in P-selectin-deficient mice with AiA and a reduction in clinical and histological symptoms of arthritis. These findings suggest that leucocyte-endothelial cell interactions depend at least partially on platelet P-selectin and therefore platelets may be responsible for the leucocyte tissue damage in AiA. [ABSTRACT FROM AUTHOR]

There is growing evidence that platelets play an important role in the development and maintenance of rheumatoid arthritis. Activation and adherence of platelets in the synovial microcirculation might be in part responsible for endothelial damage and activation of leukocytes. Recent findings show a direct influence of P-selectin on platelet- and leukocyte-endothelial cell interaction in mice with Antigen-induced Arthritis (AiA). P-selectin is only expressed by platelets and endothelial cells, not by leukocytes. Therefore, the aim of the present study was to investigate the differential influence of platelet and endothelial P-selectin on the extent of inflammation in AiA. AiA was induced in wild-type mice and in P-selectin-deficient mice from the same genetic background (four groups: each n = 7). Intravital fluorescence microscopy (IVM) was used to visualize platelets and leukocytes in the synovial microcirculation at day 8 after AiA. Platelets from either strain were fluorescence-labelled ex vivo and transferred into either strain. We were able to demonstrate a significant decrease of platelet- and leukocyte-endothelial cell interaction in P-selectin-deficient mice with AiA in comparison to wild-type mice with AiA. When wild-type platelets were donated into P-selectin-deficient AiA recipients, the leukocyte-endothelial cell interaction was significantly increased compared to the group consisting of P-selectin-deficient recipient and donor mice. These are the first in vivo results showing that the P-selectin stored in platelets is at least partly responsible for the leukocyte-endothelial cell interaction and the resulting tissue damage in AiA. In the future, a suppression of platelet P-selectin could potentially become a treatment option for reducing the effects of rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

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We studied 10 patients by means of pre- and postoperative CT who underwent computer-assisted total hip replacement using the CASPAR-system (OrthoMaquet GmbH, Rastatt, Germany). The anteversion angles of the stem and translational deviations measured after surgery were compared to the preoperatively planned ones as a quality control. We found an average difference of 7.80 (SD 6.3; 95% CI 3.3°-12.3°) in the angles and an average difference of 1.8 (SD 1.7; 95% CI 0.6-3.0) mm and 1.2 (SD 1.4: 95% CI 0.25-2.2), respectively, in the medial and lateral deviation. In conclusion, we could not confirm the same accuracy of implant position as that claimed by the manufacturer. [ABSTRACT FROM AUTHOR]

Background. The problem of metal sensitivity (Ni, Cr, and Co) in arthroplasty is still unsolved. To prevent the risk of allergy in cases with proved metal allergy in an epicutaneous test, a Natural Knee total knee arthroplasty, made totally from titanium (Ti-6Al-4V) and polyethylene, can be implanted. The results of this device have to be compared to the results of normal knee arthroplasty designed with a femoral component out of CrCoNi alloy. The mechanical resistance of this alloy is much higher than that of titanium, and therefore it is the standard for the femoral components of most knee-resurfacing devices. Methods. Thirty-five patients with a titanium Natural Knee were examined retrospectively after a mean follow-up of 2 years and 5 months (range 6 months to 5 years and 4 months). In comparison, 36 patients with a Genesis-I knee with a CrCoNi alloy femoral component were studied after a mean follow-up of 2 years and 4 months (range 8 months to 6 years and 2 months). Results. In spite of the lower mechanical resistance of titanium, the Natural Knee showed better results (knee score 84.1 points, function score 77.7 points, HSS score 80.1 points, 82.9% excellent and good results) than the Genesis-I knee (knee score 80.6 points, function score 76.4 points, HSS score 76.4 points, 68.5% excellent and good results), although these differences had no statistical significance. Conclusions. The titanium Natural Knee prosthesis has proven to be a reliable knee joint replacement in the medium term. [ABSTRACT FROM AUTHOR]

Introduction. The two available computer-assisted surgery robotic systems consist of a preoperative planning computer workstation and an industrial robot with a high speed milling device. During the computed tomography (CT) scan of the hip and the ipsilateral knee for planning the hip arthroplasty, the patient's movements are registered by a bar that is fixed at the patient's leg along its axis. Despite the companies' claim that a high accuracy of implant position can be achieved by this method, misplacements of implants are reported in the literature. Materials and methods. In an experimental study, a cadaver femoral bone was rotated during the CT scan strictly around this bar to simulate a rotational movement of the patient. Using the CT data, the planning of the hip stem and the following preparation of the femur by the robot was possible without detection of the patient's movements by the system. According to the system manual, the computer should stop the planning or give a warning in case of patient movement during the CT scan. Results. The postoperative CT scan of the cadaver femoral bone revealed a rotary deviation and a shift of the stem compared with the original planning, caused by the rotation during the CT scan. Conclusion. We propose using a second bar during the CT scan to detect these movements and thus avoiding misplacement of the implant. [ABSTRACT FROM AUTHOR]

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Copyright of International Orthopaedics is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)