[Revision total hip arthroplasty: how do metaphyseal onset, diaphyseal fill and a three-point-stem-fixation influence the postoperative subsidence of a revision straight-stem?].

AIM

It was the purpose of this study to determine the postoperative subsidence of a cementless hip revision stem in regard to the degree of metaphyseal onset, diaphyseal fit and a three-point contact of the stem in the femur.

METHODS

Data of 50 revision total hip replacements using a cementless revision straight stem (PFM-R) could be investigated. The degree of subsidence was measured on pelvic X-rays 6 and 12 months postoperatively. The degree of metaphyseal onset, diaphyseal fit and a three-point contact of the stem in the femur was determined on the immediate postoperative X-rays.

RESULTS

The amount of subsidence was strongly related to the degree of metaphyseal onset. With minor onset (up to 25 % of the possible) stems subsided 9.4 (6 months), respectively, 13.2 millimeters (12 months) in average within the investigation periods. If there was a large degree of metaphyseal onset (more than 75 % of the possible) the average subsidence was only 1.6 (6 months) or 0.9 millimeters, respectively (12 months). Neither the amount of diaphyseal fit nor the presence of three-point contact of the stem in the femur influenced the subsidence significantly. Conclusion The amount of the postoperative subsidence of stems in cementless revision total hip arthroplasty is predominantly influenced by the degree of the metaphyseal onset of the prosthesis.