With the help of a clinical and radiological follow-up evaluation 8 years after implantation of the femoral neck prosthesis CUT (ESKA Implants, Lübeck Germany), the question of whether this metaphyseal anchoring implant is recommendable in young patients will be answered.
Between 2000 and 2001 82 CUT-prosthesis procedures were performed in 79 patients (38 female, 41 male patients; average age 51.3 years) and evaluated prospectively. The clinical investigation was carried out according to the criteria of the Harris Hip and Merle d'Aubigné scores. Radiological periprosthetic bone changes were registered and a measurement of the CCD angle and femoral offset was performed. The survival rate was calculated according to both the Kaplan-Meier and the life-table analyses.
During the 12-month follow-up examination the HHS (48.4 preop.) as well as the Merle d'Aubigné score (10 preop.) increased significantly to an average value of 85.1 and 15.8, respectively (p < 0.000). Cumulative survival with replacement of the prosthesis as an end point at 8 years was 49.6 %. Due to 25 aseptic loosenings, three periprosthetic infections and three cases of persisting thigh pains, 31 replacements of the femoral neck prosthesis became necessary up to June 2008. The implantation of the CUT prosthesis led to a significant valgisation (p < 0.001) of 17.4 degrees degrees with a consecutive reduction of the femoral offset of 5 mm. Radiologically periprosthetic progressive radiolucencies, hypertrophic cortical bone changes as well as atrophy of the calcar femoris were often evaluated and interpretated as a sign of a stress shielding and migration process.
The analysis of the eight-year follow-up of 82 CUT prostheses shows that the implant does not fulfil our expectations of a femoral neck prosthesis, in spite of the possibility of a less invasive and bone-saving implantation technique. In view of unacceptable survival rates, valgisation changes of the joint geometry and critical changing procedures, from our point of view the femoral neck prosthesis CUT does not represent a recommendable alternative implant in young, active patients.