AIM To evaluate the clinical and radiological outcome nineand ten years after short-stemmed, bone preserving and anatomical hip arthroplasty with the MiniHip^(TM) system. METHODS In a prospective study, 186 patients u...AIM To evaluate the clinical and radiological outcome nineand ten years after short-stemmed, bone preserving and anatomical hip arthroplasty with the MiniHip^(TM) system. METHODS In a prospective study, 186 patients underwent hip arthroplasty with a partial neck preserving short stem(MiniHip^(TM), Corin). Elderly patients were not excluded from this study, thus the mean age at the time of surgery was 59.3 years(range 32 to 82 years). Surgery and the follow-up assessments were performed at two Centers. Up until now, the mean follow-up was 112.5 ± 8.2 mo. The Oxford Hip Score(OHS) and the Hip Dysfunction Osteoarthritis and Outcome Score(HOOS) was assessed pre-and each year after surgery. The clinical follow-up was accompanied by standardized a.p. and axial radiological examinations. Periprosthetic lucencies, hypertrophies within the Gruen zones one to fourteen were assessed. A subsidence of the stem was investigated according to Morray and heterotopic ossifications were assessed according to Brooker.RESULTS The OHS and HOOS improved from 18 ± 3.3 to 46 ± 2.0 and from 30 ± 8.3 to 95 ± 4.6 points, P < 0.001 respectively. There were no differences regarding age, etiology, friction pairings, etc.,(P > 0.05). Two stems were revised due to a symptomatic subsidence four and twelve months postoperatively. Thus, the survivorship for aseptic loosening at nine to ten years was 98.66%. Including one stem revision due to a symptomatic exostosis, bursitis and thigh pain as well as one revision because of a septic stem loosening, the overall survival for the stem with revision for any reason was 97.32%. Besides one asymptomatic patient, radiological signs of a proximal stress-shielding, such as bone resorptions within the proximal Gruen zones, were not noticed. Findings suggesting a distal loading, e.g., bony hypertrophies or bone appositions of more than 2 mm, were also not detected. CONCLUSION Regarding these first long-term results on the MiniHip^(TM), the implant performed exceedingly well with a high rate of survivorship for aseptic loosening. Our radiological results within the Gruen zones support the design rationale of the Minihip to provide a reliable metaphyseal anchoring with the expected proximal, more physiological load transfer. This might minimize or exclude a stress shielding which might be associated with thigh pain, proximal bone loss and an increased risk of aseptic loosening. The MiniHip^(TM) is a reliable partial-neck retaining prosthesis with good a clinical long-term outcome in younger as well as elderly patients.展开更多
Current literature shows that short sellers earn positive returns on their trades and that the superior performance of short sellers is due to their better analytic skills. In this paper, we investigate, if it is poss...Current literature shows that short sellers earn positive returns on their trades and that the superior performance of short sellers is due to their better analytic skills. In this paper, we investigate, if it is possible for a short seller to make profits even if he does not have insider information or is not sophisticated. We use a one period model and assume that stock price follows a random walk with a positive drift to show that the＇ expected return for an uninformed short seller is always negative and his risks are always greater than the risks of a stock buyer. Hence a short seller would not trade unless he has superior trading skills and/or information. We also show that the market conditions when the stock＇s dividend yield is greater than the risk free rate gives the shortsellers advantage over stock buyers.展开更多
基金Supported by A sponsorship from Corin (Corin Group,Cirencest,United Kingdom)
文摘AIM To evaluate the clinical and radiological outcome nineand ten years after short-stemmed, bone preserving and anatomical hip arthroplasty with the MiniHip^(TM) system. METHODS In a prospective study, 186 patients underwent hip arthroplasty with a partial neck preserving short stem(MiniHip^(TM), Corin). Elderly patients were not excluded from this study, thus the mean age at the time of surgery was 59.3 years(range 32 to 82 years). Surgery and the follow-up assessments were performed at two Centers. Up until now, the mean follow-up was 112.5 ± 8.2 mo. The Oxford Hip Score(OHS) and the Hip Dysfunction Osteoarthritis and Outcome Score(HOOS) was assessed pre-and each year after surgery. The clinical follow-up was accompanied by standardized a.p. and axial radiological examinations. Periprosthetic lucencies, hypertrophies within the Gruen zones one to fourteen were assessed. A subsidence of the stem was investigated according to Morray and heterotopic ossifications were assessed according to Brooker.RESULTS The OHS and HOOS improved from 18 ± 3.3 to 46 ± 2.0 and from 30 ± 8.3 to 95 ± 4.6 points, P < 0.001 respectively. There were no differences regarding age, etiology, friction pairings, etc.,(P > 0.05). Two stems were revised due to a symptomatic subsidence four and twelve months postoperatively. Thus, the survivorship for aseptic loosening at nine to ten years was 98.66%. Including one stem revision due to a symptomatic exostosis, bursitis and thigh pain as well as one revision because of a septic stem loosening, the overall survival for the stem with revision for any reason was 97.32%. Besides one asymptomatic patient, radiological signs of a proximal stress-shielding, such as bone resorptions within the proximal Gruen zones, were not noticed. Findings suggesting a distal loading, e.g., bony hypertrophies or bone appositions of more than 2 mm, were also not detected. CONCLUSION Regarding these first long-term results on the MiniHip^(TM), the implant performed exceedingly well with a high rate of survivorship for aseptic loosening. Our radiological results within the Gruen zones support the design rationale of the Minihip to provide a reliable metaphyseal anchoring with the expected proximal, more physiological load transfer. This might minimize or exclude a stress shielding which might be associated with thigh pain, proximal bone loss and an increased risk of aseptic loosening. The MiniHip^(TM) is a reliable partial-neck retaining prosthesis with good a clinical long-term outcome in younger as well as elderly patients.
文摘Current literature shows that short sellers earn positive returns on their trades and that the superior performance of short sellers is due to their better analytic skills. In this paper, we investigate, if it is possible for a short seller to make profits even if he does not have insider information or is not sophisticated. We use a one period model and assume that stock price follows a random walk with a positive drift to show that the＇ expected return for an uninformed short seller is always negative and his risks are always greater than the risks of a stock buyer. Hence a short seller would not trade unless he has superior trading skills and/or information. We also show that the market conditions when the stock＇s dividend yield is greater than the risk free rate gives the shortsellers advantage over stock buyers.
