[Primary stability of cementless implanted hip stems made of titanium alloy with metaphyseal fixation. A prospective clinical Roentgen-Stereometry-Analysis (RSA) study].

Aim: Under early mobilisation and full weightbearing the primary stability of two different cementless hip stems should be examined by using Roentgen Stereometric Analysis (RSA).

Method: 26 patients (slashed circle 60.8+/-7.5 J., 16 m, 10 w, BMI 27.7+/-3.9 kg/m2) received a total hip arthroplasty with an anatomical designed image-stem (IS) (Smith & Nephew, Schenefeld, Germany), 20 patients (slashed circle 60.0+/-10.9 J., 12 m, 8 w, BMI 27.5+/-3 .7 kg/m2) the Bicontact-stem (BS) (Aesculap, Tuttllingen, Germany). RSA measurements were done before mobilizing, 3 and 6 weeks, 3, 6, 12 and 24 months postoperatively. Furthermore the patients had to estimate their pain on a visually scale (VAS). We registrated the Harris-Hip-Score (HHS) and the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC).

Results: Both stems showed the maximum of subsidence in the first 3 months (IS 0.647 mm, BS 0.54 mm). 6 months postoperative the measured migrations were in the range of the accuracy. After 2 years the subsidence was 1.07 mm+/-0.07 mm for the IS-group, 0.97 mm+/-0.18 mm for the BS-group. There were no significant differences in the examined parameters between the both groups. An excellent prostheses function and high activity grade with a high WOMAC score, a high HHS and a low VAS was founded for both groups.

Conclusion: Both cementless implanted titanium hip stems showed a sufficient primary and midterm stability with excellent clinical results. The measured migrations do not differ from those given in literature for cemented stems.