Cementless total hip replacement: a prospective clinical study of the early functional and radiological outcomes of three different hip stems

Optimal fixation of cementless total hip stems is essential for long-term survival rates. The purpose of this prospective study was to evaluate the early clinical and radiological outcomes of two new total hip stems with metaphyseal (Symax(A (R))) and predominantly diaphyseal (Hipstar(A (R))) anchoring principles in comparison to the well-established straight Zweymueller (SL-Plus(A (R))) stem. Clinical and radiological evaluations of 74 patients were undertaken preoperatively as well as at 6 and 12 months postoperatively using the Harris Hip Score (HHS) and Western Ontario and McMaster Universities-Score. During follow-up no stem had to be revised. The mean preoperative HHS of the three study groups amounted to 54.6 +/- A 15.7 points. At the 12 months follow-up the mean HHS in the SL-Plus group (n = 22) was 88.3 +/- A 10.5 points, in the Hipstar group (n = 25) 83.3 +/- A 15.0 and the in Symax group (n = 27) 83.6 +/- A 15.1. Due to stress shielding the straight Hipstar stem revealed radiolucent lines in the proximal Gruen zones of about 60%, whereas the SL-Plus stem showed significantly more radiolucent lines (87%). However, subsequent long-term studies must be carried out in order to clarify if the progression of radiolucent lines may influence the clinical result and implant longevity.