The effect of entry point on malalignment and iatrogenic fracture with the Synthes lateral entry femoral nail.

PURPOSE: Multiplanar rigid femoral nails introduced through a lateral entry portal have been associated with a higher risk of iatrogenic fracture and malreduction. This study was designed to investigate if the entry point of the lateral entry femoral nail (Synthes, Paoli, PA) has an impact on alignment of the femur and the incidence of iatrogenic fracture.

MATERIALS AND

METHODS

The preoperative and postoperative radiographs of 227 femoral shaft fractures stabilized with the lateral entry femoral nail from 11 different trauma centers were retrospectively evaluated. Reviewers were blinded with respect to outcome and determined whether the starting point for the nail was anterior, middle, or posterior by dividing the greater trochanter into thirds. The corresponding alignment in both the sagittal and coronal planes was determined independently. The occurrence of iatrogenic fractures was documented as well.

RESULTS

Of the 227 radiographs reviewed, 167 had acceptable lateral radiographs of the proximal femur to determine the exact location of the entry point. There was high interobserver reliability (kappa = 0.87) with regard to the scoring of starting point for the nail. The results for the concordant pairs (n = 154) were as follows: middle third 47%, anterior third 44%, and posterior third 10%. The risk of valgus malalignment is nearly threefold (10% versus 25%) when the starting point is anterior as compared with the middle entry point (risk ratio, 2.6; 95% confidence interval, 1.2-5.9; P = 0.021). There was no association between entry site and varus or apex-anteroposterior angulation. There were a total of 16 iatrogenic fractures in the cohort. Ten of these had adequate lateral hip radiographs, and of these, nine occurred after an anterior entry site. There is strong evidence that an anterior insertion site leads to iatrogenic fracture as compared with a middle entry portal (13% versus 0%, P = 0.001).

CONCLUSIONS

Accurate entry site within the greater trochanter is essential to prevent malalignment and iatrogenic fractures when using the lateral entry femoral nail to stabilize fractures of the femoral diaphysis. The helical shape of the nail can result in valgus malalignment and fracture if the entry point is too anterior, and surgeons must recognize these consequences of insertion inaccuracy. Meticulous biplanar imaging and experience with this particular implant are important for its precise and safe insertion.