Severe fractures of the femur can be divided into those fractures which must be reconstructed directly and those that can
(and should) be reconstructed indirectly. The former include both intra-articular and periarticular fractures of the femoral
head and femoral condyles, and diaphysis in the latter.
Comminuted diaphyseal femoral fractures
Despite their initial outward appearance, these fractures are very straight-forward to address. The basic principle is bridging
fixation whereby there is sufficient bone stock available at either bone end to purchase the implants, thus providing the
requisite stability across the fractures for bone healing. These fractures can be handled with any number of fixation devices:
IM pin and external skeletal fixator (ESF), interlocking nail (IN), bridging plate (spanning, standard or locking plate),
bridging plate/rod (standard or locking), orthogonal or opposite double plate (standard or locking).
IM pin /ESF
In this fixation, the IM pin bridges the fracture and is of sufficient size to neutralize the bending forces at the fracture
(pin size approximately ≥ 2/3 of the medullary canal diameter). The IM pin acts to bring the fracture back out to length
and simultaneously re-establish axial alignment. Because of the nature of the comminuted fracture, there is no provision
for maintaining length (collapse of the fracture can occur along the pin), nor is there neutralization of rotation. In addition,
because the IM pin does not fill the entire medullary cavity at the level of the fracture there is no neutralization of shear
forces. The addition of an ESF satisfactorily address all of these forces; however, a minimum of a 4-pin ESF is necessary
with 2 pins in each major bone fragment on either side of the comminution. The ESF can be applied as a Type-1a or 1b device.
The advantage of the latter is additional strength to the fixation, but at the cost of placing additional fixation pins; furthermore,
none of these pins are in the frontal plane, thus they penetrate more soft-tissue as compared to a Type 1a ESF applied parallel
to the frontal plane. In the femur, another issue is the position of the connecting bar relative to the distance of the fixation
pin insertion into the bone; this length is large due to the anatomic configuration of the abundant soft-tissues present (quadriceps
and biceps femoris mm.). This increased length also will decrease the strength of the fixation. One method to overcome some
of these strength issues is to use a "tie-in" configuration of the IM pin with the ESF, where the proximal extent of the IM
pin is left long and incorporated into the ESF.
The largest disadvantage an ESF is the amount of soft-tissue penetration of the fixation pins through the musculature of the
femur, and issues with the pin/soft-tissue interface. Large wounds are not uncommon around the fixation pin(s) despite attempting
to place them in areas of minimal soft-tissue coverage over the bone. This is especially true in high motion areas, such
as the lateral side of the stifle (distal femur) and proximally with an IM pin that exits to be incorporated into the ESF.
The result is development of a large open granulating wound around these pins. More problematic, however, is the degree of
patient discomfort from these pins. They also inhibit adequate physical therapy and function; therefore, they can retard
or prevent full functional outcomes.