Femoral alignment of the Charnley stem: a randomized trial comparing the original with the new instrumentation in 123 hips.
Deficient cement mantles are associated with aseptic loosening of the stem component of total hip replacement. In a former study of 206 Charnley stems, we found high frequencies of stem malalignment, especially on the lateral view, consequently resulting in a high percentage of low cement mantle grading. If the "true" lateral radiographic projection is not used, there is a risk that the frequency of mantle defects is underestimated. A logistic regression analysis showed a high correlation between low cement mantle grading and stem loosening after a mean follow-up of 10 years. The new Charnley instrumentation was introduced in 1994 and we started a randomized trial including 123 prostheses to determine whether the new instrumentation improved the position of the stem in both the AP and lateral planes. Postoperative radiographs revealed a significant change in AP positioning-i.e., from a high percentage of varus with the original method to valgus with the new instrumentation. However, there was no difference on the lateral view, with a persisting high frequency of stems with implant-inner cortex contact resulting in high percentages of low cement-mantle grading in both systems. If this deficiency, in a long-term perspective, is associated with aseptic loosening, as many authors have claimed, the manufacturers should address the problem.
Ostgaard
H C
HC
Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, Göteborg University, Sweden.
Helger
L
L
Regnér
H
H
Garellick
G
G
D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D005260:Female; D005500:Follow-Up Studies; D006615:Hip / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011859:Radiography; D012044:Regression Analysis