Fracture neck of femur - Still an unsolved issue

Medial Plating of Pauwels Type III Femoral Neck Fractures Decreases Shear and Angular Displacement Compared with a Derotational Screw

OBJECTIVES

The purpose of this mechanical study was to compare 2 methods of augmented stabilization of Pauwels type III femoral neck fractures.

METHODS

Ten matched pairs of young cadaveric femurs were cut 22 cm distal to the lesser trochanter. All specimens received a 70-degree osteotomy, which was stabilized with a 135-degree sliding hip screw. One of each pair received augmented fixation with a 6.5 mm fully threaded cannulated screw. The other specimen in the matched pair had additional fixation with a 3.5 mm 5-hole tubular plate placed at the inferior-medial femoral neck. Each specimen was tested under cyclic axial loading conditions (5000 cycles between 200 and 1400 N at 2 cycles/sec) and subsequently loaded to failure. The angular displacement (varus), interfragmentary (shear) displacement, and failure loads were calculated.

RESULTS

In the augmented plate group, 7 specimens failed by angular displacement and 3 failed by shear displacement. In the augmented screw group, 8 specimens failed by angular displacement and 2 by shear displacement. The plate group was found to have significantly less angular displacement, regardless of completed cycles, than the augmented screw group (0.75 ± 0.35 degrees vs. 2.15 ± 1.99 degrees averaged across completed cycles, P < 0.01). Similarly, the plate group was found to have significantly less shear displacement, regardless of completed cycles, than the augmented screw group (0.77 ± 0.70 mm vs. 1.22 ± 0.92 mm averaged across completed cycles, P = 0.01). The average failure load of the plate group (4930 ± 1578 N) was also larger but not significantly different from the screw group (3824 ± 2140 N), P = 0.12.

CONCLUSIONS

Augmenting sliding hip screw stabilization of a Pauwels type III fracture with a medial plate applied to the femoral neck significantly decreases angular displacement and shear displacement compared with augmentation with a derotational screw.