Healing after retrograde nail fixation relies on maintenance of the fracture viability in the metaphyseal / diaphyseal component of the fracture. This is made possible by closed reduction techniques and results in high union rates and low infection.
Malreductions (external rotation/valgus) can be common without careful scrutiny of intraoperative technique and radiographic control. The correct entry point and positioning of the nail are crucial to avoiding intraarticular damage.
Reamed versus unreamed nailing
Reamed nailing allows the use of larger diameter implants and may therefore provide greater initial stability. It carries a greater risk of a large entry hole causing articular cartilage damage, but reduces the risk of disrupting the fixation of intraarticular fractures.
Fat embolization, or articular reaming debris, may be concerns with reaming.
In elderly patients with osteoporotic femoral canals, no, or only minimal, reaming may be required because the canal is capacious.
Anatomy of the distal femur
The distal femur has a unique anatomical shape. Seen from an end-on view,
the lateral surface has a 10° inclination from the vertical, while the medial
surface has a 20–25° slope. A line drawn from the anterior aspect of the
lateral femoral condyle to the anterior aspect of the medial femoral condyle
(patellofemoral inclination) slopes approximately 10°. These anatomical details
are important when inserting screws, or blade plates. In order to avoid joint
penetration, these devices should be placed parallel to both the patellofemoral
and femorotibial joints planes.
The muscle attachments to the distal femur are responsible for the typical
displacement of the distal articular block following a supracondylar fracture,
namely shortening with varus and extension deformity. Shortening is due to the
pull of the quadriceps and hamstring muscles, while the varus and extension
deformity is caused by the unopposed pull of the adductors and gastrocnemius,
The popliteal vessels, the tibial nerve and the common peroneal nerve lie in
close proximity to the posterior aspect of the distal femur. Because of this,
vascular injuries occur in about 3% and nerve injuries in about 1% of fractures
of the distal femur.
Muscle forces acting on the fracture fragments often determine the pattern
of displacement of a fracture. Traction alone can restore the normal length of
the bone, but may exaggerate the axial malalignment, instead of correcting
Positioning aid to assist reduction
The distal femoral fracture can be reduced by flexing the knee to reduce the
muscle force of the gastrocnemius muscle.
A supporting pad can be used to help to correct a recurvatum deformity.
It is very important to restore the biomechanical axis of the lower limb.
The normal biomechanical axis follows a line from the center of the femoral
head, through the center of the proximal tibia and then through the center of
the ankle joint. This axis can be checked intraoperatively by using a piece of
cable, such as the diathermy cord, to give an approximate estimate of the axis,
Before interlocking, the correct position of the nail and the rotation of
the femur must be verified. Not only must the biomechanical axis be restored,
but care should be taken to ensure that there is no malrotation of the distal
femur on the proximal femur.
If no traction table is used (i.e., using the freehand technique) the cable
method may be used. In this technique, the electrocautery cord is held from the
iliac spine across the patella to the cleft between the first and second toes.
If rotation is correct, this cord will pass over the midline of the patella,
and slightly medial to the tibial eminence. The radiological landmarks of the
center of the femoral head, the center of the knee and the center of the ankle
joint should all be in line if the mechanical axis of the femur is correct.
Illustration of the longitudinal axes of the lower limb.
AO teaching video: Distal femoral nail
This procedure may be performed with the patient in one of the following positions:
A variety of techniques can be used to aid the reduction of the distal femur.
For most fractures, manual traction is satisfactory. In some cases, more sophisticated reduction techniques have to be used such as:
Pointed reduction forceps
depending on the metaphyseal fracture configuration.
The fracture reduction may be achieved by longitudinal traction applied to
the upper tibia.
It is useful to have a small sandbag just behind the hip joint to prevent
external rotation. This will make subsequent alignment of the distal femoral
condyles easier to orientate.
Alternatively, a carbon triangle can be used.
Localization of entry point
It is very important to perform every step of the procedure of locating the
entry point under image intensifier guidance. On the AP view, center the guide
wire exactly in the middle of the intercondylar notch. On the lateral view it
should be located in the extension of the Blumensaat’s intercondylar roof
The entry point for the nail is in line with the axis of the medullary
canal, just below the crest of the intercondylar notch. The correct position is
therefore located anterior and lateral to the proximal attachment of the
posterior cruciate ligament.
On the lateral view, the entry point must be at the anterior tip of the
Blumensaat’s intercondylar roof line. There is no “safe zone” posterior to this
line. Take care not to start the entry point posterior to the Blumensaat’s
line, in order to avoid damage to the cruciate ligaments when reaming.
The x-ray shows the desired 30° flexion of the knee joint. With less flexion
the tibial plateau hinders the guide wire insertion. With more flexion the
articular surface is in danger and the patella is in the way.
Insert the guide wire into the medullary canal, as far as approximately
12-14 cm proximal to the fracture zone.
Opening of the canal
To open the medullary canal, push the protection sleeve and drill sleeve
over the guide wire into the notch.
Open the medullary canal to a depth of approximately 30 mm using the
cannulated drill bit.
Then remove the drill bit, protection sleeve, and guide wire.
Irrigate the knee joint carefully to remove all drilling debris.
The concept of a poller screw is based on the principle that the
malalignment induced by oblique, proximal and distal fractures can be
counteracted by the nail-directing effect of the screw. Therefore, its position
should aim to counteract the anticipated displacement of the fracture. Most
often, it is therefore inserted in the short side in the distal fragment. If
there is a wide canal, two screws can be inserted, one on either side of the
path of the nail. It is technically challenging to insert the poller screw in
the exactly correct position. On one hand, the screw should prevent reaming in
the undesired location. On the other hand, it should not impede the reaming
process, or nail insertion.
It is better to insert the poller screw prior to reaming and, in cases of
unreamed nailing, prior to nail insertion, in order to provide adequate contact
between the nail and the screw. If the poller screw is inserted after reaming,
the path of the nail is already set and the poller screw may not function. A
small fracture screw, or a locking screw, can be used as a poller screw,
depending on the local anatomy.
The reaming process in the presence of the poller screw must be performed
very carefully in order not to damage the reamer tip.
The most frequent indication for poller screws is an oblique fracture which
would tend to shift when the axial knee blow technique is used to close any
fracture gap, or when the patient is mobilized.
See also: Stedtfeld HW, Mittlmeier T, Landgraf P et al (2004) The
Logic and Clinical Applications of Blocking Screws. J. Bone Joint Surg.
Am. 86:17-25, 2004.
Insertion of poller screw
The poller screw should be located according to the direction of the initial
fracture displacement. Therefore, in a medial displacement, the fracture will
try to displace medially even after the reduction and a poller should be placed
lateral to the proposed nail track.
If there is a wide canal, or a very unstable situation, a blocking screw can
be placed on each side of the proposed nail path.
For retrograde femoral nailing to achieve adequate fracture stabilization,
the fracture should be at least 6 cm from the joint line to achieve distal
locking with two transverse screws or a screw and a spiral blade. In contrast,
more distal fixation can be achieved with plates, or locked fixators. For
example the distal most screws in a LISS plate, or a condylar plate, may be
The distal-most fixation for various implants are:
- LISS plate: subchondral
- Condylar plate: subchondral
- 95° angled blade plate: 1.5 – 2 cm
- 95° dynamic condylar screws: 2 cm
- Retrograde intramedullary nail: 6 cm (for 2 locking screws, or one locking
screw and a spiral blade)
The spiral blade can be used with the retrograde femoral nail. The spiral
blade can be locked as an angular stable implant. This will give rigidity to
the fixation construct by virtue of increased surface area of the spiral
The spiral blade may be particular useful in osteoporotic bone.
Additional locking screws may still be used with the spiral blade.
Variations in surgical preferences exist with regard to the optimal length
of a retrograde nail for treatment of a distal femoral fracture.
Determine nail length using a guide wire
If reaming was performed, the maximal length of the nail is determined by
comparing a second identical length guide wire to the one that has been
inserted. The correct placement of the tip of the guide wire in the proximal
canal should be assessed using an image intensifier. A second guide wire must
be positioned in contact with the articular surface of the distal femur. This
must also be verified by image intensifier.
It is desirable to use the longest nail possible in the femur to prevent
latent risk of periimplant fractures.
A radiographic ruler may also be used to determine the length of the femoral
The ruler should lie in the center of the distal end of the femur at the
roof of the intercondylar notch and along the center of the medullary
It is important to measure the medullary diameter at the mid portion of the
femur, which represents the narrowest segment of the medullary canal
The inner cortical edge should touch the inner numbered disk of a ruler
aperture. In the illustration an inner cortical diameter of 14 mm is shown.
Consideration for special situations
Multifragmentary fractures, or open fractures with bone loss
In multifragmentary fractures, or in open fractures with bone loss, it is safer
to perform preoperative planning on the uninjured leg.
Narrow medullary canal
In some cases, when the medullary is very narrow, it might be necessary to
Sequential reamer size increase
After the tissue protector has been introduced, the reamer shaft, fitted
with the initial reamer head is inserted over the guide wire. Usually, reaming
begins with a nine-millimeter, end-cutting medullary reamer.
Sequential reaming is performed with increments of 0.5 mm each.
As soon as “chatter” can be felt and heard, the inner cortex has been
Reaming must be performed to one or two increments above the planned nail
diameter, in order to allow a smooth nail insertion. For example, for a nail
diameter of 10 millimeters, reamer heads of up to 10.5, or 11, millimeters
diameter are used. If a very tight fit of the reamer can be felt before the
desired reaming size is reached, consider a smaller diameter nail than
Pitfalls: eccentric and overaggressive reaming
Eccentric reaming can cause weakening of the adjacent cortex, which may
interfere with healing, or even cause a fatigue fracture.
Trapping of reamer by slow spinning
If the reamer gets trapped while reaming, it must be gently removed by the most
senior surgeon because breakage of the reamer tip in this situation can be a
Heat necrosis by over-forceful reaming
Reaming with excessive force should be avoided because it is likely to
cause heat necrosis of the femoral cortex. This applies especially for narrow
midshaft canals (9 mm or less in diameter).
Rapid thrusting/systemic fat embolization
Care should be taken only to use sharp reamers, to advance the reamers slowly
and to allow sufficient time between reaming steps for the intramedullary
pressure to normalize. Rapid thrusting of the reamer may increase further the
intramedullary pressure. The image demonstrates fat extrusion during reaming in
a human cadaver specimen with a window in the proximal section.
High intramedullary pressures may cause pulmonary embolization of medullary
fat, which in turn may lead to pulmonary dysfunction (images show
echocardiographic examples of fat embolization through the right atrium).
During nail insertion, it is important that the assistant apply traction to
the lower extremity, in order to prevent shortening and/or angulation of the
distal main fragment. In order to prevent this complication, which is very
difficult to correct later, repeated image intensifier assessments are
Drive the nail gently into the distal fragment. This can often be performed
manually. If required, gentle hammer taps are usually sufficient to ensure
proper advancement. Insert the nail until it just passes deep to the cartilage
Take care in osteoporotic oblique and multifragmentary distal femoral
fractures not to shorten the femur by impacting the bone ends too firmly
It is important to perform the distal locking first. If proximal locking is
done first, the surgeon will no longer be able to perform final corrections to
Distal locking can be performed with either:
- Spiral blade
- Combination of screws and the spiral blade
Distal locking is performed by using the appropriate aiming device attached
to the insertion handle.
It is preferable to use at least two distal locking options for all distal
femoral fracture types. When two distal locking options are used it is not
possible to perform dynamic distal locking. Dynamic locking can only be
achieved by using the proximal dynamic locking hole.
Distal aiming device
After verifying the correct position of the distal end of the nail under
image intensifier control, the distal aiming device may be attached to the
Pearl: use of guide wire to determine position of nail end
Insert a guide wire through the small hole of the aiming device to
determine the position of the nail end.
For correct measurements of locking screw length the drill sleeve must be
pressed onto the bone surface at all times.
Gentle pressure can be applied to the tip of the drill sleeve to maintain
its correct position.
The sites of the skin and fascial incisions for the drill bit and the distal
locking screws may be determined after the drill sleeve assembly has been
inserted into the holes of the aiming device. The length of each locking screw
is read from the calibrated drill bit. The correct length is confirmed using
image intensifier control.
Verification of locking screw placement
In all cases, obtain final x-rays in two planes in order to check the exact
locking screw placement. If the normal tight coupling between the nail and the
insertion guide has been altered, the screws might have been placed either
anterior or posterior to the nail.
Pitfall: too long a locking screw
It is important to remember that the distal femur tapers from the posterior
to the anterior. Therefore, if a straight AP view is obtained, the locking
screws appear to be inside the bone. If they appear to be outside the bone,
they are most likely too long and will invariably cause pain and possibly
heterotopic ossification. In order to assess the exact length of the locking
screws an AP view can be obtained with 30° internal rotation of the lower
Internal rotation by 30° reveals that an inappropriate screw length was
Principles of spiral blade insertion
It is important to confirm fracture reduction with AP and lateral
The aiming arm for the retrograde spiral locking blade is attached to the
standard insertion handle.
The proximal locking screw must have been inserted before the spiral
Applying the spiral blade jig
Make an incision through the skin to allow the spiral blade locking sleeve
to be inserted through the jig and pushed down onto the bone.
Insert a 3.2 mm guide wire through the 13 mm/3.2 mm wire guide into the
femoral condyles until the tip is flush with the medial cortex. Confirm wire
position by x-ray, bearing in mind the trapezoidal cross section of the distal
femur at this level.
Insert guide wire and measure for spiral blade
Remove the 13.0 mm/3.2 mm wire guide. Place the spiral blade measuring
device over the guide wire and advance it to the bone. Read the number on the
measuring device at the end of the guide wire. This measurement is the length
of the spiral blade.
Open the lateral cortex
Insert the 13.0 mm cannulated drill bit over the guide wire and through the
protection sleeve to perforate the lateral cortex. An automatic stop prevents
the drill bit from penetrating too far. Remove the drill bit and protection
Insert the spiral blade
Attach the appropriate length spiral blade to the spiral blade inserter.
Pass the spiral blade assembly over the guide wire. Advance the spiral blade
inserter through the aiming arm, ensuring engagement of the inserter’s helical
grooves with the mating pins of the aiming arm. Manually advance the spiral
blade to the bone. Use light, controlled blows of the slide hammer to seat the
spiral blade. Advancement should be monitored radiographically. The correct
insertion depth is reached when the spiral blade head is flush with the lateral
Assessment of rotation
Compare the profile of the lesser trochanter with that of the contralateral
leg (lesser trochanter shape sign), holding the leg so that the patella faces
anteriorly on both sides.
Before positioning the patient, store the profile of the lesser trochanter
of the intact opposite leg (patella facing anteriorly) in the image
The illustration shows the lesser trochanteric profile of the intact
In cases of malrotation, the lesser trochanter is of a different profile
when compared to that of the contralateral leg.
Take care to assess rotation with the patella facing directly
Matching of the lesser-trochanter shape
After distal locking, achieve correction by using the handle of the nail
insertion device. The distal main fragment can be rotated in relation to the
proximal main fragment.
The first proximal locking screw is inserted in the anteroposterior plane. A
radiolucent x-ray table is essential. Care must be taken in preoperative
planning so that adequate image intensifier views of the proximal femur can be
obtained in both the AP and the lateral planes before the operation begins.
The thickness of the subcutaneous tissue, especially in obese patients, can
make this procedure technically demanding.
It is extremely difficult to perform lateral to medial proximal locking with
a long retrograde femoral nail. This is due to the difficulty in positioning
the image intensifier around the proximal femur.
Drilling of screw hole
Proximal AP locking has to be performed by the freehand method. After you
have verified the correct position of the distal end of the nail under the
image intensifier, visualize the shape of the proximal locking hole.
Then, bring the image intensifier into a strict AP position at 90° to the
nail. The proximal static holes must project a perfect circle and the tip of a
scalpel is projected into the center of the hole.
Make a skin incision and bluntly dissect the muscle.
Place the radiographic projection of the tip of the drill bit as centered as
possible into the hole image. Start drilling but assess the position of the tip
of the drill bit repeatedly, with the drill temporarily uncoupled.
Maintaining lower extremity position
While drilling the locking hole, the assisting surgeon must prevent the leg
from moving, in order not to miss the target hole.
Pearl: radiolucent drill
If available, a radiolucent angled drill can be used as described in distal
locking of antegrade nailing for femoral shaft fractures (click
for the description).
Determine the appropriate screw length with a depth gauge and insert the AP
locking screw. Take care to prevent an oblique insertion of a locking screw
because it can become trapped between the firm cortex of the proximal femur and
Second locking screw
Depending on the fracture pattern, use either one or two proximal locking
The question as to whether a second locking screw in the long nail should be
used must be decided by the surgeon on a case-to-case basis.
In a short nail and a very wide medullary canals a second locking screw
should be used. In this case the second screw should be inserted perpendicular
to the first one.
Pearl: secure screw using a suture
If the contact between the screw driver and the locking screw is lost, the
screw may move within the soft tissue and become extremely hard to capture. To
prevent this time-consuming complication, lasso the locking screw with a strong
Insertion of the end cap with double screw distal locking
An end cap must be used. The length of the head of the end cap depends on
the final relationship of the nail end to the intercondylar notch of the distal
In distal femoral fractures, the nail just passes the condylar surface
resulting in the need for a 0 mm end cap. By no means should the end cap
project distal to the subchondral region.
Introduce the end cap using a hexagonal screwdriver.
Insert the end cap with spiral blade locking
It is very important to secure the spiral blade with the dedicated end cap
to create a fixed-angled device.
The end cap fulfills two functions: it prevents bony ingrowth into the nail
and it locks the spiral blade, providing a stable, fixed-angle construct.
To minimize the chance of cross threading, turn the end cap counterclockwise
until the threads of the end cap align with the threads of the nail. Insert the
end cap by turning clockwise until it is fully seated.
Note: there is a difference in end-cap design. Use the color-coded end
cap for the spiral blade.
Verification of end cap placement
Tighten the end cap with the screw driver. Verify using image intensifier
control and palpation that the end cap has been fully inserted into the nail
and does not project from the bone.
Before the wound closure, perform thorough irrigation of the knee wound in
order to minimize the risk of infection and to remove any debris from the
End the procedure with the closure of the tendon (as necessary), the deep
tissues and the skin.
A suction drain may be inserted intraarticularly, when indicated.
Assessment of alignment and knee stability
Before the patient is moved from the fracture table, observe rotation of the
leg clinically and compared it to the contralateral side.
Pearl: post-ORIF examination of knee joint stability under
With the femur now stable, it is possible to perform a thorough, but
gentle, examination of the knee joint to determine any associated ligamentous