Stress fractures in the gapped area of a two implant construct: a case report

Biomechanical Testing of a 3-Hole Versus a 4-Hole Sliding Hip Screw in the Presence of a Retrograde Intramedullary Nail for Ipsilateral Intertrochanteric and Femur Shaft Fractures

OBJECTIVE

The goal of this study was to compare a 3-hole versus a 4-hole sliding hip screw (SHS) in the presence of a retrograde intramedullary (RIM) nail for fixing intertrochanteric and comminuted midshaft femur fractures.

METHODS

Mechanical tests were performed on 10 matched pairs of human cadaveric femurs that were osteotomized and then fixed using a 3-hole SHS versus the traditional "gold standard" 4-hole SHS in the presence of an RIM nail.

RESULTS

Data showed no differences between the 3-hole SHS with RIM nail versus 4-hole SHS with RIM nail for stiffness (281 ± 127 vs. 260 ± 118 N/mm, P = 0.76), clinical failure at 10 mm of hip displacement (2014 ± 363 vs. 2134 ± 614 N, P = 0.52), or ultimate mechanical failure (3476 ± 776 vs. 3669 ± 755 N, P = 0.12).

CONCLUSIONS

For this fracture pattern, a 3-hole SHS with RIM nail may be a suitable surgical alternative to the traditional "gold standard" method because it provides the same biomechanical properties while potentially reducing surgical time, blood loss, and hardware used.

Biomechanical effects of hardware configuration after union of proximal femoral and shaft fractures

OBJECTIVES

The use of two implants to manage concomitant ipsilateral femoral shaft and proximal femoral fractures has been indicated, but no studies address the relationship of dynamic hip screw (DHS) side plate screws and the intramedullary nail where failure might occur after union. This study compares different implant configurations in order to investigate bridging the gap between the distal DHS and tip of the intramedullary nail.

METHODS

A total of 29 left synthetic femora were tested in three groups: 1) gapped short nail (GSN); 2) unicortical short nail (USN), differing from GSN by the use of two unicortical bridging screws; and 3) bicortical long nail (BLN), with two angled bicortical and one unicortical bridging screws. With these findings, five matched-pairs of cadaveric femora were tested in two groups: 1) unicortical long nail (ULN), with a longer nail than USN and three bridging unicortical screws; and 2) BLN. Specimens were axially loaded to 22.7 kg (50 lb), and internally rotated 90°/sec until failure.

RESULTS

For synthetic femora, a difference was detected between GSN and BLN in energy to failure (p = 0.04) and torque at failure (p = 0.02), but not between USN and other groups for energy to failure (vs GSN, p = 0.71; vs BLN, p = 0.19) and torque at failure (vs GSN, p = 0.55; vs BLN, p = 0.15). For cadaveric femora, ULN and BLN performed similarly because of the improvement provided by the bridging screws.

CONCLUSIONS

Our study shows that bicortical angled screws in the DHS side plate are superior to no screws at all in this model and loading scenario, and suggests that adding unicortical screws to a gapped construct is probably beneficial.