Washing the Femoral Canal Results in More Predictable Seating of a Short, Tapered Femoral Stem

It is critical that a femoral rasp be effective in preparing the proximal femur to accept the size and the geometry of the femoral implant at the time of total hip arthroplasty. Short, tapered femoral stems may be at greater risk because they require the preparation of a short femoral region without any reaming. We undertook a study to determine the effect on implant seating in femora that were prepared by rasping alone with those that were rasped and the canal was washed with saline at the time of cementless THA with a short, tapered femoral implant.

We retrospectively analyzed the preoperative, intraoperative, and radiographic data on 170 consecutive patients undergoing a primary THA using a short, taper, uncemented metaphyseal-filling stem. The femur was prepared using a rasp-only technique. In the initial 99 patients, the canal was rasped, but not washed (group 1). In the subsequent 71 patients, the canal was rasped and before implant insertion the canal was washed with 100 cc of normal saline to remove all loose cancellous bone (group 2). Intraoperatively, the distance between the calcar cut and the rasp and subsequently, the calcar cut and the implant was measured. We defined a difference of more than 2 mm between the seating of the rasp and the final implant as a clinically significant mismatch.

Overall, a clinically significant mismatch occurred in 50% (49/99) of cases in group 1 and 15% (11/71) in group 2. Multivariate logistic regression analysis corrected for preoperative, intraoperative, and radiographic measurements showed that washing significantly decreased the mismatch between the rasp and the implant (odds ratio, 5.32; confidence interval, 2.10-13.73; P < .001).

Although the present rasp design is sufficient to create the geometric space for this short, metaphyseal stem, it does not adequately remove the bone debris to ensure reproducible seating of the implant. Washing the femoral metaphysis with saline to remove bone debris, after rasping and before inserting the final implant, significantly decreased the mismatch between seating of the final rasp and the implant in this cementless short, metaphyseal-filling, taper design stem. Level of Evidence III.