Periprothetische Knochendichteveränderung um den Hüftprothesenschaft Optan® Zementiert/Zementfrei im Verlauf eines Jahres

Background: Periprosthetic bone loss is a well documented problem around cemented and cementless total hip arthroplasty (THA). So far there exists no comparison of stems with the same geometrical design. Patients and methods: We studied 25 patients (group A) receiving a cementless and 18 receiving a cemented Optan femoral component over the period of one year performing DEXA to detect periprosthetic BMD changes. Results: Clinical results documented with the Harris hip score and the WOMAC were equal in both groups. Bone loss was different in all Gruen zones except region 7 with the main bone loss in both groups. Interpretation: Fixation with or without cement changes the physiological load transfer in the femur with stress shielding in the proximal part as one of the main problems of cementless THA

The epicondylar ratio can be reliably determined in both computed tomography and X-ray

Purpose!#!One of the key factors to the successful revision of total knee arthroplasty (rTKA) is the reconstruction of the joint line, which can be determined using the epicondylar ratio (ER). The measurement is established in X-ray and MRI. However, it is not known whether computed tomography (CT) allows a more reliable determination. The objective was to assess the reliability of the ER in CT and to determine the correlation between the ER in CT and a.p. X-ray of the knee.!##!Methods!#!The ER was determined on X-ray and CT images of a consecutive series of 107 patients, who underwent rTKA. Measurements were made by two blinded observes, one measured twice. The inter- and intraobserver agreement, as well as the correlation between the two methods, were quantified with the Intraclass Correlation Coefficient.!##!Results!#!The average lateral ER was 0.32 (± 0.04) in X-ray and 0.32 (± 0.04) in CT. On the medial side, the average ER was 0.34 (± 0.04) in X-ray and 0.35 (± 0.04) in CT. The interobserver agreement for the same imaging modality was lateral 0.81 and medial 0.81 in X-ray as well as lateral 0.74 and medial 0.85 in CT. The correlation between the two methods was lateral 0.81 and medial 0.79.!##!Conclusions!#!The ER can be reliably determined in X-ray and CT. Measurements of the two image modalities correlate. Prior to rTKA, the sole use of the X-ray is possible

Biomechanics of a cemented short stem: a comparative in vitro study regarding primary stability and maximum fracture load

Purpose!#!In total hip arthroplasty, uncemented short stems have been used more and more frequently in recent years. Especially for short and curved femoral implants, bone-preserving and soft tissue-sparing properties are postulated. However, indication is limited to sufficient bone quality. At present, there are no curved short stems available which are based on cemented fixation.!##!Methods!#!In this in vitro study, primary stability and maximum fracture load of a newly developed cemented short-stem implant was evaluated in comparison to an already well-established cemented conventional straight stem using six pairs of human cadaver femurs with minor bone quality. Primary stability, including reversible micromotion and irreversible migration, was assessed in a dynamic material-testing machine. Furthermore, a subsequent load-to-failure test revealed the periprosthetic fracture characteristics.!##!Results!#!Reversible and irreversible micromotions showed no statistical difference between the two investigated stems. All short stems fractured under maximum load according to Vancouver type B3, whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to Vancouver type C. Mean fracture load of the short stems was 3062 N versus 3160 N for the conventional stems (p = 0.84).!##!Conclusion!#!Primary stability of the cemented short stem was not negatively influenced compared to the cemented conventional stem and no significant difference in fracture load was observed. However, a clear difference in the fracture pattern has been identified

Mid-term migration pattern of a calcar-guided short stem: A five-year EBRA-FCA-study

BACKGROUND Short-term results of several short-stem designs have indicated early axial migration. Mid- and long-term results for most designs are lacking. The objective of this study was to evaluate the mid-term migration pattern of a calcar-guided short stem five years postoperative. METHODS Implant migration of 191 calcar-guided short stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component- Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analyzed and compared to the migration pattern of implants potentially being "at hazard" with a subsidence of more than 1.5 mm at 2 years postoperatively. Influence of preoperative Dorr types (A vs. B vs. C), age (70 years), gender (female vs. male), weight (90 kg), BMI (30) and uni-vs. bilateral procedures on mid-term migration pattern was analyzed. Additionally outcome of varus- and valgus stem alignment was assessed. RESULTS Mean axial subsidence was 1.5 mm (SD 1.48 mm) at final follow-up. Two years after surgery 73 short stems were classified "at hazard". Of these stems, 69 cases showed secondary stabilisation in the following period, whereas 4 cases presented unstable with more than 1 mm of further subsidence. Stem revision was not required neither in the group of implants with early stabilisation nor the group with pronounced early onset migration. Male gender and heavy-weight patients had a significant higher risk for axial migration, as well as extensive valgus stem alignment, whereas for Dorr type B, compared to A, no statistical difference could be observed. CONCLUSIONS In most cases, even in the group of stems being "at hazard", settling could be documented. While different Dorr types did not show a statistically significant impact on axial migration, particularly in male and heavy-weight patients the risk of continuous subsidence is increased. In those 4 cases with further migration, undersizing of the stem could be recognized. At present, clinical consequences are still uncertain

Biomechanics of a calcar loading and a shortened tapered femoral stem: Comparative in-vitro testing of primary stability and strain distribution

Purpose!#!The most common femoral short stems available on the market can, in principle, be divided with regard to their anchoring concepts into a calcar loading and a shortened tapered design. The purpose of this study was to compare the primary stability and stress-shielding of two short stems, which correspond to these two different anchoring concepts.!##!Methods!#!Using seven paired fresh frozen human cadaver femurs, primary axial and rotational stabilities under dynamic load (100-1600 N) were evaluated by miniature displacement transducers after 100,000 load cycles. Changes in cortical strains were measured before and after implantation of both stem types to detect implant-specific load transmission and possible stress-shielding effects.!##!Results!#!Reversible and irreversible micromotions under dynamic load displayed no significant differences between the two implants. Implantation of either stem types resulted in a reduction of cortical strains in the proximal femur, which was less pronounced for the calcar loading implant.!##!Conclusions!#!Both short stems displayed comparable micromotions far below the critical threshold above which osseointegration may disturbed. Neither short stem could avoid proximal stress-shielding. This effect was less pronounced for the calcar loading short stem, which corresponds to a more physiological load transmission

Tissue distribution of quercetin in pigs after long-term dietary supplementation

Although the flavonol quercetin is intensively investigated, our knowledge about its bioavailability and possible target organs is far from being complete. The aim of this study was to check the potential of quercetin to accumulate in various tissues after long-term dietary treatment compared with a single treatment with flavonol. Pigs ingested either a single dose of quercetin aglycone (25 mg/kg body weight; Expt. 1) or received the flavonol twice a day at the same dose mixed into their regular meals (i.e 50 mg.kg(-1).d(-1)) for 4 wk (Expt. 2). In both experiments, we took plasma and tissue samples 90 min after the final meal and analyzed them using HPLC. Additionally, the specific activity of the enzyme beta-glucuronidase was measured in selected tissues. Higher flavonol concentrations than in plasma were found in only the liver (Expt. 1) or the intestinal wall and kidneys (Expt. 2). All tissues except blood plasma contained a variable amount of deconjugated quercetin in the range of 30-100% of total flavonols. However, the specific beta-glucuronidase activity was not correlated with the proportions of deconjugated flavonols in the various tissues. Long-term dietary intake of the flavonol did not lead to a greater accumulation in any tissue compared with the single treatment. Flavonol concentrations only exceeded the plasma concentration within organs involved in its metabolism and excretion, including liver, small intestine, and kidney

Konzeption einer Methode zur Geschäftsmodellentwicklung und Implementierung am Beispiel der Berufsbildungsdienstleistung

Ziel des Beitrags ist die Entwicklung und Beschreibung einer strukturierten Methode für die systematische Geschäftsmodellentwicklung. Zunächst werden die Grundlagen der Geschäftsmodellinnovation und -entwicklung dargestellt. Dann wird die Methode ausführlich beschrieben. Sie besteht aus vier Phasen: Geschäftsmodellaudit, Ideengenerierung, Konkretisierung und Vorbereitung der Implementierung. Zum Schluss wird die Umsetzung der Methode am Beispiel eines Dienstleistungsunternehmens aus dem Bereich der Berufsbildung, das internationale Märkte erschließen will, demonstriert