Prior to undertaking internal fixation of a distal femoral fracture, it is
important to make sure that the patient is adequately resuscitated and that
the surgeon has a good understanding of the fracture pattern. Good-quality
anteroposterior and lateral radiographs and a computed tomographic scan of the
distal part of the femur are essential for an understanding of all
intra-articular fracture planes, if any. Specific attention should be placed
on locating coronal plane (so-called Hoffa) fractures that would require
unique lag-screw trajectories. The basic design rationale of the polyaxial
plate (POLYAX; DePuy Trauma, Warsaw, Indiana) is a hybrid model of fixation,
with a fixed-angle large central distal screw
(Fig. 1) providing a 5°
valgus angle between the distal fragment and the femoral shaft and peripheral
polyaxial screws allowing optimal distal fixation even in the presence of lag
screws, knee arthroplasty components, or complex fracture planes
(Fig. 2).
The patient is positioned supine on a radiolucent table, and intravenous
antibiotics are given. The image intensifier (c-arm) is positioned on the side
of the table opposite from the operating surgeon. The senior author (G.H.)
prefers to have both lower extremities prepared and draped into the surgical
field for several reasons. First, this positioning allows the surgeon to
compare limb length, rotation, and alignment with those of the contralateral,
normal limb. In addition, this positioning allows a lateral radiograph of the
fractured limb to be easily made by simply lifting the normal limb out of the
way of the c-arm (Fig. 3)
instead of lifting the fractured limb, which could result in a loss of
reduction or slippage of reduction clamps and wires. Before the incision is
made, it is wise to learn the personality of the fracture, that is, to learn
what maneuvers are necessary to achieve a reasonable reduction of the limb.
Typically, some gentle traction and correction of coronal alignment are
required. This is facilitated by complete muscle paralysis. We have found that
a "bump" made of rolled towels is useful to assist in obtaining
sagittal plane alignment. We start with a small stack of operative towels and,
once the correct height has been determined by gradually adding towels until
the desired reduction has been obtained, the stack is wrapped with a Coban
wrap or an Ace bandage so that the stack height is maintained. Typically, the
bump must be slid proximal to the knee
(Fig. 4) to cause the distal
fragment to flex downward from its typically hyperextended position.
Obviously, determining the size and the position of the bump and the amount
and direction of traction needed to achieve biplanar reduction before an
incision is made is much easier than going through the same learning process
after multiple clamps and pins have been applied.
Various incisions can be used for the percutaneous internal fixation of
distal femoral fractures. The choice of incision length and location is
dictated by the complexity of the intra-articular fractures, if any, and the
size of the patient. For extra-articular, periprosthetic, and very simple
intra-articular patterns, we prefer an anterolateral incision along the flare
of the lateral femoral condyle. It is important not to make this incision too
far posteriorly because articular visualization and plate-seating will be
difficult (Fig. 5). For
fractures with extensive articular fracture lines or displacements, a lateral
peripatellar arthrotomy is recommended. This is essentially a lateral
subvastus approach that allows a full view of both femoral condyles by
subluxing the extensor mechanism medially and making a formal arthrotomy
(Fig. 6). It is important to
understand that, regardless of the approach, metaphyseal dissection should not
take place because this is the area that requires the preservation of
soft-tissue attachments, and thereby vascularity, the most. However, it is
also important to understand that anatomic articular reduction is paramount to
the long-term function of the knee joint.
The first step in the internal fixation of these injuries is anatomic
reduction of the articular injury and temporary Kirschner wire fixation.
Direct visual and fluoroscopic evaluation of the accuracy of reduction is
essential. The fragments are then stabilized with individual lag screws
(Fig. 7). We prefer
small-fragment screws placed along the periphery of the distal part of the
femur to avoid interference with the lateral plate and to secure fixation into
the very dense subchondral bone of the distal part of the femur. Although the
POLYAX plate will allow locking screws to miss obstacles such as lag screws if
necessary, lag screws obviously should not be placed in a haphazard fashion,
but in the best orientation to achieve stable fixation of the articular
surface. For fractures associated with wide intra-articular displacement,
Kirschner-wire or Shantz-pin joysticks can be used to help to manipulate the
condyles, and a large reduction tenaculum can be useful. Careful attention to
the rotational relationship of the condyles is important. The subchondral bone
of the intercondylar notch can be a useful guide to determining rotation,
especially when trochlear comminution is present. A lateral fluoroscopic
radiograph also can help to achieve the correct sagittal plane rotational
relationship of the condyles.
Once the articular surface is reduced and stabilized with individual lag
screws, the next step is to connect the epiphysis to the metadiaphysis while
correcting biplanar alignment, limb length, and rotation while avoiding
fracture distraction. Additionally, the metaphyseal comminution should remain
undisturbed to preserve the vascularity of the fracture fragments. Obviously,
this is the most challenging portion of the procedure. The appropriate plate
length can be determined by preoperative templating, or, more commonly, by
placing gentle traction on the limb and using the available metal plate
template intraoperatively. We routinely choose a plate that leaves a minimum
of five screw-holes available proximal to the most proximal extent of the
fracture (usually a nine or twelve-hole side-plate). If there is any doubt, it
is best to have more fixation available than to have less; therefore, when
between sizes, we tend to choose the longer plate. The plate is attached to
the screw-targeting jig with a threaded bolt. Typically, the fast guide for
the 8.0-mm screw is screwed into the head of the plate at this point as well.
The plate is then slid along the lateral cortex of the femur in a submuscular
but extraperiosteal fashion proximally until it has reached its desired
position on the distal fragment. Tactile feedback should be present as the
plate slides along the lateral part of the femur
(Fig. 8). We recommend slow
insertion in order to allow the surgeon to appreciate this tactile feedback of
the plate tip gently scraping the lateral femoral cortex. One can feel the
plate slip off the femur anteriorly or posteriorly, and this can be corrected
if the plate insertion is slow and careful. The c-arm can be used to guide
this step as well. Gross alignment and correct limb length are then obtained
(duplicating the fracture reduction maneuvers learned at the beginning of the
procedure). The plate is seated on the lateral aspect of the distal fragment
as distally as possible without overhang of the articular surface
(Figs. 9-A and 9-B).
At this point, a large reduction clamp can be used to temporarily clamp the
plate to the distal fragment (Fig.
10). An incision is made medially to allow the medial tine of the
clamp to seat on bone. The guide-pin for the blue 8.0-mm fixed-angle central
locking screw is then inserted into the distal fragment. It is absolutely
critical that this pin be parallel to the joint line of the distal part of the
femur (Fig. 11). Any deviation
will result in malalignment. The senior author (G.H.) prefers to advance the
pin under live fluoroscopy because minor changes in trajectory can be made
without passing the pin deep into the medial condyle. Alignment can be
corrected with the assistant holding the limb at the foot of the table and
adding varus or valgus and gentle traction as indicated. At this time, a
lateral fluoroscopic image of the distal fragment is made. If any residual
hyperextension exists at the fracture site, the distal fragment can be rotated
into flexion (on the axis of the single guidewire) and can be held reduced
with another Kirschner wire placed through the available Kirschner wire-holes
in the head of the plate.
At this point, we have found two useful strategies for completing the
reduction and fixation. It is critical to note that both methods rely on
absolutely accurate positioning of the plate on the distal fragment and
absolutely accurate insertion of the distal guide-pin parallel to the joint
line of the distal part of the femur.
The first method involves complete fracture reduction before any screws are
placed and is recommended for surgeons who are less familiar with percutaneous
plating techniques. After confirmation of distal guide-pin and plate placement
on the distal fragment, hyperextension of the distal fragment is corrected and
the fragment is secured with a Kirschner wire, thereby stabilizing sagittal
alignment with this second point of fixation, as stated above. At this point,
the assistant can match the limb length and alignment with those of the
contralateral, normal limb. The rotational relationships of the anterior
superior iliac spine, the patella, and the second toe can be used as a gross
guide to rotation. A proximal threaded anchor bolt can then be inserted to
stabilize the construct and to effectively "close the box,"
facilitating screw targeting through the jig
(Figs. 12-A and 12-B). To
further refine the reduction and plate position on the lateral aspect of the
femur, a small incision is then made laterally along the femoral shaft and
either a threaded reduction bolt (Figs.
13-A and 13-B) or the reduction clamp
(Figs. 14-A and 14-B) is
inserted submuscularly in order to secure the side-plate to the femoral shaft.
Dissection in this area is biologically benign, as it is remote from the
metaphyseal fracture or fractures (Figs.
15-A and 15-B). Accurate plate positioning on the lateral side of
the femur is confirmed on a lateral radiograph or with a palpating finger
through the incision that was used to insert the clamp. We recommend a full
c-arm survey of the entire reduction and plate position in both planes. Limb
length, alignment, and rotation can then be compared with those on the
contralateral side. At this point, the distal 8.0-mm fixed-angle locking screw
is inserted over the guide-wire, locking the alignment of the distal fragment.
Shaft screws can be placed in various sequences, but we have found a
"hybridization" of shaft screws to be advantageous. A nonlocking
bicortical screw is inserted in one of the middle available holes in the plate
proximally. This effectively pulls the plate to the bone and makes further use
of secondary clamps or compression devices unnecessary. The holes near and far
from the fracture site proximally are typically filled with bicortical locking
screws. It is important to understand that nonlocking screws are inserted
first. Locking screws cannot pull the plate to the bone or afford any axial
compression, if needed. The use of nonlocking screws first to facilitate
reduction and plate apposition to the lateral femoral cortex can be useful
because, as these screws are tightened, they will compress the plate to the
lateral cortex. Locking screws are then inserted afterward to further
stabilize the construct (Fig.
16). Calibrated drills and soft-tissue sleeves are used for screw
insertion to prevent soft-tissue injury. Torque-limiting drivers are used for
final screw seating in order to prevent cold welding or head-stripping. A
minimum of four bicortical screws proximally are recommended as a general
rule. Unicortical locking screws are only used when necessary, such as when
working around the stem of a femoral component of a total hip
arthroplasty.
The distal polyaxial screws are typically inserted at this point. All
screw-holes are usually filled with locking screws in the distal fragment. The
goal is to disperse, not to converge, the screws to provide improved distal
fixation far into the medial femoral condyle. The fast guides are threaded
into the bushing, and drilling is commenced. If an obstacle is encountered,
one simply changes the drilling trajectory until the far medial cortex is
reached. Measurements are taken from the calibrated drill-bit. The fast guide
is removed, and the screw is inserted. We prefer to advance screws under
power, but slowly, until near final seating. Final seating is done with use of
the torque-limiting screwdriver. The real advantage of polyaxial screws is the
fact that long distal screws can be inserted and locked. With fixed trajectory
plates, if an obstacle is encountered, all the surgeon can do is to choose a
shorter locked screw or use a nonlocked screw, both of which are undesirable
options for maximizing distal fixation. The ability to avoid obstacles to long
locking screw fixation is particularly obvious for periprosthetic fractures
proximal to a total knee arthroplasty or an intra-articular fracture with
independent lag screws (Figs.
17,
18,
19,
20).
All clamps, pins, and jigs are then removed, and the entire construct,
reduction, plate position, limb length, rotation, and alignment are confirmed.
If necessary, the electrocautery cord can be used as an alignment check by
centering the wire on the femoral head proximally and on the middle of the
talus distally. The cord should pass through the center of the intercondylar
eminence of the tibia. The wounds are irrigated and closed in a layered
fashion. A soft dressing and a knee immobilizer or similar brace are
applied.
A second variation of the technique can be useful. Of course, all of the
reduction steps, the fluoroscopic vigilance of reduction and plate position,
and the absolute requirement of accurate distal guide-pin placement remain.
The alternate technique involves the placement of screws prior to complete
reduction of the fracture. The distal 8.0-mm screw is inserted, and a
secondary polyaxial screw is placed into the distal fragment. This effectively
locks the relationship of the plate and the distal fragment in two planes. One
then has a good "handle" on the distal fragment and, by simply
manipulating it and using the limb-manipulation techniques described above,
one can position the distal fragment in the appropriate relationship to the
proximal fragment. This technique is advantageous during the management of
osteopenic patients as better capture of the distal fragment is possible prior
to final fracture reduction than is possible with guide-pins and clamps. Limb
length, alignment, and rotation are obtained as previously described, and the
femoral plate clamp is used to pull the plate to bone. Two bicortical
nonlocking screws are inserted to stabilize the plate to the shaft proximally,
and then the clamp can be removed. Additional locking screws and polyaxial
locking screws are then inserted as previously described.
Patients are given prophylactic antibiotics and thromboembolism
prophylaxis. Gentle knee range of motion can commence on the first
postoperative day. The patient is initially restricted to touch-down
weight-bearing only with a walker or crutches. For patients with
extra-articular fractures, progressive weight-bearing can commence at six to
eight weeks on the basis of radiographic evidence of progressive healing. For
patients with intra-articular fractures, weight-bearing is delayed for twelve
weeks to avoid articular displacement.
CRITICAL CONCEPTSINDICATIONS:Our current indications for polyaxial locking plates include the
following.Intra-articular and extra-articular fractures of the distal part of the
femurIntra-articular and extra-articular fractures of the proximal part of the
tibiaPeriprosthetic fractures of the distal part of the femur and proximal part
of the tibiaNonunions of the distal part of the femur and proximal part of the tibia
that are amenable to plating techniquesCONTRAINDICATIONS:Active infectionMassive bone loss due to neoplasmFractures around open physesPITFALLS:Articular malreductionCoronal and sagittal plane malalignment—typically valgus angulation
and hyperextension of the distal femoral fragmentLimb-length discrepancy or malrotationDistraction of the fracturePlate malpositioning—typically too anterior on the femoral shaftFailure to understand the mechanical consequences of shaft screw insertion
sequences—one must remember that non-locking screws are inserted first
in the shaft, and then locking screws are inserted afterward.Failure to use torque-limiting screwdrivers, resulting in screw cold
welding or head-strippingAUTHOR UPDATE:Because of concerns with potential screw cold welding or head-stripping
noted in association with first-generation titanium locking plates, we always
use torque-limiting screwdrivers when final screw seating is performed.
Anecdotally, we have not found cold welding, head-stripping, or difficulty
with screw removal to be a problem when the correct technique and instruments
are used. Additionally, we have found that the use of the percutaneous clamp
to stabilize the plate to the lateral part of the femur is very helpful, and
we generally prefer this method to drilled-in compression devices because the
clamp is easily repositioned and does not require additional drill-holes.
CRITICAL CONCEPTS
INDICATIONS:
Our current indications for polyaxial locking plates include the
following.Intra-articular and extra-articular fractures of the distal part of the
femurIntra-articular and extra-articular fractures of the proximal part of the
tibiaPeriprosthetic fractures of the distal part of the femur and proximal part
of the tibiaNonunions of the distal part of the femur and proximal part of the tibia
that are amenable to plating techniques
Our current indications for polyaxial locking plates include the
following.
Intra-articular and extra-articular fractures of the distal part of the
femur
Intra-articular and extra-articular fractures of the proximal part of the
tibia
Periprosthetic fractures of the distal part of the femur and proximal part
of the tibia
Nonunions of the distal part of the femur and proximal part of the tibia
that are amenable to plating techniques
CONTRAINDICATIONS:
Active infectionMassive bone loss due to neoplasmFractures around open physes
Active infection
Massive bone loss due to neoplasm
Fractures around open physes
PITFALLS:
Articular malreductionCoronal and sagittal plane malalignment—typically valgus angulation
and hyperextension of the distal femoral fragmentLimb-length discrepancy or malrotationDistraction of the fracturePlate malpositioning—typically too anterior on the femoral shaftFailure to understand the mechanical consequences of shaft screw insertion
sequences—one must remember that non-locking screws are inserted first
in the shaft, and then locking screws are inserted afterward.Failure to use torque-limiting screwdrivers, resulting in screw cold
welding or head-stripping
Articular malreduction
Coronal and sagittal plane malalignment—typically valgus angulation
and hyperextension of the distal femoral fragment
Limb-length discrepancy or malrotation
Distraction of the fracture
Plate malpositioning—typically too anterior on the femoral shaft
Failure to understand the mechanical consequences of shaft screw insertion
sequences—one must remember that non-locking screws are inserted first
in the shaft, and then locking screws are inserted afterward.
Failure to use torque-limiting screwdrivers, resulting in screw cold
welding or head-stripping
AUTHOR UPDATE:
Because of concerns with potential screw cold welding or head-stripping
noted in association with first-generation titanium locking plates, we always
use torque-limiting screwdrivers when final screw seating is performed.
Anecdotally, we have not found cold welding, head-stripping, or difficulty
with screw removal to be a problem when the correct technique and instruments
are used. Additionally, we have found that the use of the percutaneous clamp
to stabilize the plate to the lateral part of the femur is very helpful, and
we generally prefer this method to drilled-in compression devices because the
clamp is easily repositioned and does not require additional drill-holes.