Anatomic stem design reduces risk of thin cement mantles in primary hip replacement

To analyse the influence of femoral stem design in the lateral plane (anatomic vs. straight) on the cement mantle quality. In this consecutive multi-surgeon radiographic study we determined, Dorr grading, cement mantle quality (Barrack) and mantle thickness using Gruen zones 1-14 in 280 primary cemented total hip replacements, divided into two groups (140 anatomic Biomet Olympia, 140 straight Exeter Universal Series). Twenty-three per cent of the straight Exeter Universal stems had a cement mantle of < 2 mm thickness in Gruen zone 8 and 25% in Gruen zone 9, compared to 0.7% of the anatomical Olympia stems in Gruen zone 8 and 1.4% in Gruen zone 9. The difference between the two groups was statistically significant (P < 0.001). In all other zones no significant differences were found. This radiological study confirms that femoral stems with an anatomical curve in the lateral plane carry a lower risk of thin cement mantles (especially in Gruen zones 8 and 9) than straight stems. Cement mantle analysis in one radiographic plane only is insufficient.