Evaluation der Effektivität und Sicherheit der NANOS®-Kurzschaft-Hüftendoprothese mit klinischen und radiologischen Ergebnissen - mittelfristige Ergebnisse nach 3 Jahren -

Abstract Introduction: In recent years, several modifications of hip prosthesis have been made to offer them to young (<65 years) and physical active patients. One of those new bone preserving types is the NANOS short stem, which has to be analyzed in this study concerning effectivity and safety. Materials and methods: 50 patients received a NANOS short stem prosthesis in the Departement of Orthopedics of the University Hospital Marburg between January 2010 and November 2011. There were 27 male and 23 female participants with a mean age of 54.16 years. Main indication (70%) was primary osteoarthrosis. The examinations were conducted preoperatively as well as after 3 months, 1 year and 3 years. Thereby internationally accepted clinical scores were used (WOMAC, HHS, UCLA, subjective satisfaction) and X-rays of the pelvis in anterior-posterior and projection according to Lauenstein. This study deals with the medium-term results after 3 years. Results: In the 1. and 3. postoperative year 46 of the 50 patients wirh implanted NANOS prosthesis could be examined. The initial value (55.26 points; range 13-89) of the WOMAC osteoarthritis index, where 0 points represent absence of discomfort, improved significantly in the first year (15.87 points; range 0-65) and changed for the worse slightly after 3 years (20.67 points; range 0-78). The same course was registered for the Harris-Hip-Score, where 100 points represent the absence of discomfort, with 52.58 points (range 24-83) preoperatively, an increase to 94.7 points (range 67-100) after 1 year and a slight decrease until the 3- year-follow-up (91.7 points; range 66-100). Due to more physical activity the total value for the UCLA score increased constantly from the preoperative examination with 5.4 points (range 3-8) via 7.09 points (range 4-9) in after year 1 to 7.13 points (range 5-9) after 3 years. 95.7% of the patients were “satisfied“ or “very satisfied“ with the results after 1 year, whereas there were 91.3% in year 3. Leg length differences had to be registered in 13 cases (30.2%), whereby none of them was >3,2 cm. Radiological signs of loosening couldn’t be seen in a relevant dimension, heterotopic ossifications appeared after 3 years only for men (14%). Severe implant related adverse events were represented by 1 lesion of the peroneus nerve as well as an aseptic loosening of the acetabular cup leading to revision. The implant survival rate calculated was 100% after 3 years for the NANOS stem. Conclusion: The NANOS stem was presented to be save and stable at 3 years postoperatively in the own results. At the same time there was a reduction of the clinical symptoms and patient’s participation at daily and leisure time activity has increased. In occasion of this success there aren’t any objections against the use of the NANOS stem in young patients. For a clear recommendation it is necessary to wait for the long-term results. Comparisons with the literature prove to be difficult because of absence of data from studies with similar design.