Introduction: We compared the discrepancies between postoperative femoral component and the preoperatively predicted postoperative femoral component anteversions from CT data in cases of cementless THA, in which custom-made femoral components prepared from CT data were inserted directly without reaming or broaching.

Materials and methods: The subjects were 44 females (51hips) and 11 males (11 hips) with an average age at surgery of 54 years (range, 21–74). The average duration of follow-up was 44 months (range, 24–75). The femoral component was designed from 2 circles showing the corner of the medial and lateral rims of the component along the medial and lateral inner cortex on each CT slice. The anterior and posterior rims of the component were designed as lines connecting the 2 circles. From a CT slice of the planned osteotomy site and a slice passing through the knee, the preoperative femoral neck anteversion was measured. The postoperative femoral component anteversion was measured from the CT slice passing through the center of the ball and the slice passing through the knee.

Results: The mean discrepancy between the postoperative femoral component anteversion and the preoperatively predicted postoperative anteversion was 1.9° (range, −29.5–38). The average preoperative Harris hip score was 44 points (range, 17–80). At the most recent follow-up, the score was 88 points (range, 51–98). Sixty-one hips were evaluated as bone-ingrown fixations and one hip was evaluated as a stable fibrous fixation. There were no loosed femoral components.

Discussion and conclusion: There were 22 hips whose discrepancy between the postoperative femoral component anteversion and the preoperatively predicted postoperative anteversion was over 10°. However, the rotational angle on insertion did not influence the stability of the custom-made femoral component in this short-term follow-up survey. This probably indicates the effectiveness of the non-reaming or non-broaching technique.