Femoral component positioning in hip resurfacing with and without navigation

Abstract

Early failures after hip resurfacing often are the result of technical errors in placing the femoral component. We asked whether image-free computer navigation decreased the number of outliers compared with the conventional nonnavigated technique. We retrospectively compared 51 consecutive hip resurfacings performed using image-free computer navigation with 88 consecutive hip resurfacings performed without navigation. Patient demographics were similar. There were no differences in the average native femoral neck-shaft angles, planned stem-shaft angles, or postoperative stem-shaft angles. However, when the postoperative stem-shaft angle was compared with the planned stem-shaft angle, there were 33 patients (38%) in the nonnavigated group with a deviation greater than 5 degrees in contrast to none in the navigated group. Notching was present in four patients in the nonnavigated group and none in the navigated group. The average operative time was 111 minutes for the navigated group and 105 minutes for the nonnavigated group. Image-free navigation decreased the number of patients with potentially undesirable implant placements.

Level of evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Fig. 1

A conventional Durom jig is shown with the alignment guide wire.

Fig. 2

A conventional Durom jig is shown with the notch-checking device.

Fig. 3

A box plot shows the postoperative stem-shaft angles for the navigated and nonnavigated groups. Box lengths represent the interquartile range (first to third quartiles). The line in the center of the boxes represents the median value. Data represented by “o” are outliers (greater than 1.5 to 3.0 times the interquartile range over the third quartile) and data represented by the asterisks are extreme values (greater than three times the interquartile range over the third quartile).

Fig. 4

The box plot shows the difference between the planned stem-shaft angle and the postoperative stem-shaft angle for the navigated and nonnavigated groups. Box lengths represent the interquartile range (first to third quartiles). The line in the center of the boxes represents the median value. Data represented by “o” are outliers (greater than 1.5 to 3.0 times the interquartile range over the third quartile) and data represented by the asterisks are extreme values (greater than three times the interquartile range over the third quartile).

Fig. 5

The box plot shows the absolute error (difference) between the postoperative stem-shaft angle and the planned stem-shaft angle for the navigated and nonnavigated groups. Box lengths represent the interquartile range (first to third quartiles). The line in the center of the boxes represents the median value. Data represented by “o” are outliers (greater than 1.5 to 3.0 times the interquartile range over the third quartile) and data represented by the asterisks are extreme values (greater than three times the interquartile range over the third quartile).

Fig. 6

The error (postoperative stem-shaft angle minus planned stem-shaft angle) for each postoperative stem-shaft angle achieved in the navigated and nonnavigated groups is shown.