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Background: Hydroxyapatite coated (HAC) hip implants have been used in clinical practice for more than two decades. However, the majority of studies have reported only intermediate term outcomes that are not reliable for predicting long-term behavior in all implants. The aim of this study was to determine the performance of HAC total hip arthroplasty in younger patients over a 10-year follow-up period. Methods and Results:This was an observational retrospective study of a 137 consecutive hips with the ABG I prosthesis. Of these, 128 were available for the last investigation. Median duration of follow-up was 10.9 years. The mean age at time of index surgery was 46±6.7 years. Probability of implant survival was estimated using the Kaplan-Meier method. The overall 12-year cumulative survival was 0.55 (95% CI, 0.443-0.659). Periprosthetic osteolysis (57 %) was the most frequent reason for failure followed by aseptic loosening (28 %). When only aseptic loosening was included in the analysis, the same fi gures for cup and stem were 0.873 (95% CI, 0.808-0.938) and 0.992 (95% CI, 0.976-1.0), respectively. Patients with a smaller cup size were those at high risk for revision due to wear-related complications (odds ratio, OR=4.3; 95% CI, 1.734-10.555).Conclusion: This study reports one of the poorest 12-year survivorship data for cementless acetabular component in the literature. The main reason for premature failure was osteolysis, strongly related to high wear rate of polyethylene.

Background:Polyethylene wear is considered a most important part of periprosthetic osteolysis development. Thus, its measurement is central to contemporary orthopaedics.Aims: The aim of this paper was to compare the accuracy of three radiographic techniques for wear measurement. Secondly, the influence of the abduction angle of the cup on measurement accuracy was investigated.Methods: Wear was measured manually in 80 patients by a single observer according to the Livermore, Charnley, and Dorr description. A multi-component statistical analysis was used to test the hypothesis that the Livermore technique was superior. In vitro data obtained from a Universal-type measuring microscope served as a gold standard.Results: In vitro measurements showed an average linear wear of 0.363 mm per year (0.000-0.939, SD 0.241) with a corresponding volumetric wear rate of 161 mm 3 per year (0-467, SD 118.2). The Livermore technique showed the least deviation from the optical reference standard and a superior position from the viewpoint of error analysis but the correlation coefficient was slightly less (r = 0.761) than for the Dorr and Charnley techniques (r = 0.795 and r = 0.778, respectively). In addition, the mean error of the Dorr method differed significantly from zero (p = 0.036). Overall, the Livermore technique was the most accurate method for polyethylene wear measurement regardless of the abduction angle of the cup.Conclusions: The Livermore technique performed manually was more accurate than the Charnley and Dorr methods. Nevertheless, we consider the Dorr technique an adequate tool for day-to-day wear measurements, mainly due to its simplicity.

Periprosthetic osteolysis is associated with accelerated wear rates. The goal of this study was to investigate the influence of demographic and technical variables on wear rates and size of osteolytic lesions. Eighty retrieved ABG I prostheses were analyzed according to prospectively established criteria. There were 22 men and 58 women with an average age of 52 years (34-65) at the time of revision. The average time from index surgery to revision was 67 months (26 to 106). Polyethylene wear measurements were performed using a Universal-type measuring microscope. The average linear wear and volumetric wear rate was 0.363 mm per year (0-0.939, SD 0.241) and 161 mm 3 per year (0-467, SD 118.2), respectively. The wear rates were significantly higher (a) in patients with primary osteoarthritis in comparison with postdysplastic hips, (b) in hips where zirconia prosthetic heads articulated against the polyethylene liner, and (c) in cups placed laterally to Kohler's line. Risk that linear wear rate could be more than 0.2 mm per year was three times higher in patients who were operated in 1997 and later (OR 3.0, 95 % CI 1.126-7.993, p = 0.03). A strong association was revealed between magnitude of wear and size of femoral osteolysis.

Higher education institutions are continually striving to make education relevant to the working environment students will encounter upon graduation. One of the tools for enhancing an institution's quality and sufficiently informing students about their outcomes and learning opportunities is a quality assessment. Quality assessment is a long process which establishes measurable student learning outcomes, then analyses and interprets them. This enables students to receive feedback on their learning and helps them to improve their performance. The authors' objective was to gather empirical data on students´ learning in order to improve the process of learning and to refine study programmes. A longitudinal study was used to observe students' performance and outcomes from entrance exams to state exams. Statistical analysis revealed that there is a correlation between the results of the admission tests and the study results, especially the connection between the results of the entrance test and the chance of successful completion of studies. No statistically significant correlation was found between the overall results of military students' studies. An interesting issue is a comparison between military and civilian students, as well as civilian students´ results. As a continuous process, assessment of students' performance was observed up until the Final State Examination.