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Germany is among Europe’s leading nations in the field of hip arthroplasty. Patients undergo such surgeries earlier and earlier in life. At the time of surgery, 20% of the patients are younger than 60. These are more active and therefore more demanding regarding their hip joint performance. Due to increasing life expectancy at least one revision surgery is to be expected. That is why keeping the loss of bone substance as low as possible and soft tissue-saving surgical techniques are of significant importance. As a result the short-stem hip prosthesis Nanos has been developed.
Stress shielding should be extensively reduced by metaphyeal force transmission. In order to avoid the instability of the hip, the offset should not be reduced but rather extended. The variety of short-stem hips available on the market with different designs, anchorages, biomechanics as well as implantation techniques, requires a precise examination so that the appropriate implant is selected.
The aim of this thesis was to examine whether the Nanos short-stem hip prosthesis achieves comparatively as good results as the Proxy-plus standard hip stem and whether gender specific differences occur. The date was collected on the basis of HHS, radiographs as well as pre-surgery and one year post-surgery patient questionnaires.
In our research the HHS pre-surgery improved significantly as compared to the one year post-surgery in both groups: within the Nanos group from 48,16 to 82,94 and within the ProxyPlus group from 43,24 to 77,65. In a direct comparison of both groups, the Nanos group one year post-surgery performed significantly better than the ProxyPlus group regarding the HHS. However, it is not the case for every parameter of the score.
Comparing the male patients of both groups, we observed that men belonging to the Nanos group achieved a better total score in both, function and ache. Regarding the mobility, the male patients of both groups achieved equal results. Only the overall results were significant. Comparing the female patients, women belonging to the Nanos group performed better than the ProxyPlus women in the categories overall results and function. Regarding ache and mobility both groups achieved equal results. Only the total score and the mobility were significant.
The CDD angle of the Nanos group increased by +6,74° (from 128,45° to 135,19°) one year post-surgery whereas the femoral offset increased by +3,9 mm (from 41,69 mm to 45,59 mm). Post-surgery, the treated leg had extended by +2,14 (from 7,76 mm to 9,9 mm) compared to the healthy side.
In comparison, the CCD angle of the ProxyPlus group increased by +3,23°(from 130,06° to 133,29°). The femoral offset increased by +4,61 mm (from 40,39mm to 45mm). Post-surgery, the treated side had extended by +3,06 (from 5,12 mm to 8,18 mm).
Comparing to the Nanos group, the CCD angle and the femoral offset of the overall ProxyPlus patients as well as the females one year post-surgery, has changed less in relation to the initial values. Indeed the BLD (discrepancy of leg length) has extended less for both groups as well as for both of the genders one year post- surgery. In the latter case, the extension for the Nanos group was lower.
For all these radiological results and measured data a significance could not be determined.
All in all, we came to the conclusion that comparing to ProxyPlus standard hip prosthesis, the Nanos short-stem hip prosthesis is able to achieve comparably good results, hence it is a good alternative to the standard hip prosthesis. Only minimal gender-specific differences had been proved. Further studies over a longer observation period are desirable.