Femoral intramedullary nail- Synthes Expert Lateral Femoral Nail (LFN) for impending pathological fracture

Pre-operative radiographs demonstrate a lesion in the subtrochanteric region (A), eroding the cortical bone at the proximal metaphyseal-diaphyesal junction.
Using Mirel’s scoring criteria this lesion is scored as follows:
Site: peritrochanter (3)
Pain: functional (3)
Lesion: lytic (3)
Size: 1/3 – 2/3 (2)
TOTAL = 11

An MRI scan of the whole femur demonstrates no further lesions.
A T1 image (fat is white) demonstrates the ‘anatomy’ and clearly shows which tissues have been invaded by tumour. In this case there is cortical erosion of the medial subtrochanteric region. There is no extraosseous tumour and there is no fracture.
As an aide memoire, on T2 images – water is white (H2O).

Set up is key to any operation and it is of utmost importance in femoral nailing. Commonly the bracket for the ‘direct placement leg holder’ (see photo) is attached to the operating table at the end of the rail in position (B). It should however, be mounted at position (A).

With the bracket in position (A), the gas strut for the ‘direct position leg holder’ is no longer blocking the area marked (B). This area (B) is needed for the X-ray C-arm to be able to show a true lateral of the femur. Importantly, in patients’ with short femurs, you must have this area clear in order to obtain the correct alignment of the C-arm to adequately demonstrate the distal locking bolt holes.

The arc of movement of the direct position leg holder is different to the native hip / leg. I therefore recommend placing the patients’ leg in the desired position and then moving the direct position leg holder, to the patients’ leg.
If you place the leg in the leg holder and then move them both together, there is a risk that you could fracture the femur. If the hip is stiff or the bone is weakened, you have a much greater lever arm, so it is difficult to realise when too much force is being applied.

When inserting the foot into the traction boot, I would recommend changing the boot’s position to match the foot. If you rotate the foot, to match the boot, you will manipulate the fracture and possibly displace it.
Using Charnley’s principles for fracture reduction, the deformity has to be exacerbated to allow a satisfactory reduction. Therefore in displaced femoral fractures, I would mount the foot in the boot in its resting position. Traction is then applied and once the correct length has been determined on the image intensifier, then the rotation is corrected and the fracture reduced.

The middle foot strap is applied first. By applying tension here first, a vector force is applied to the foot and it pulls the heel down on to the foot plate and posteriorly into the stirrup.
A finger can be used to check that the heel is down.

There are different methods to hold the ipsilateral arm up and adducted across the chest. It is important to move the arm, as it will block the trajectory of the nail. In some centres a padded bracket can be attached to the side of the operating table, however, I still find that this can get in the way. I prefer to use a soft foam collar and cuff, that is tied to the table rail on the contralateral side. This allows the arm to be displaced and held without anything blocking the nails’ path into the proximal femur. However, be aware of how much traction is applied, as it has been reported that patients’ have been pulled / fallen off the operating table.

The patient’s arm is flexed and adducted across his chest (A). The shoulders are displaced away from the hip that is to be operated and a clear path is created that is in alignment with the anatomical axis of the femur (B). Minimal adduction is applied to the leg that is to be operated (C). In proximal fractures this often creates unwanted varus, as the traction post acts a fulcrum for fracture displacement. The contralateral leg is held out of the way for the radiographer (D).

Asking the radiographer to routinely rotate the image, so that the traction table post is vertical, is very helpful.
You can clearly see that the femoral neck / head are retroverted and hence the angle which you insert the guide wire will need to match this. This means that the wire will need to be elevated away from the operating room floor. It will also mean that as the nail rotates during insertion, you are aiming for the nail aiming arm / jig to be approximately 5-10 degrees above the horizontal plane.

I routinely use a double prep of dark pink chlorhexidine (0.5%) followed by a light pink chlorhexidine prep (0.5%). The dark pink allows me to clearly see that the whole area has been painted with prep.

Prepping with the light pink prep and using the contrast in the colours, allows me to see exactly where I have painted for a second time and also washes off the dark pink stain, so that they are not mistakenly diagnosed with cellulitis.

An image is obtained with the image intensifier to determine whether the proposed skin incision is in the correct place. The incision should be in alignment with the anatomical axis of the femur and also level with the greater trochanter in the lateral plane. Due to patients’ body habitus, this incisions’ placement is highly variable and hence having a x-ray is helpful.

The majority of surgeons would make a horizontal incision that is in alignment with the femoral canal in the lateral plane. I prefer to make an oblique incision that is approximately 45 degrees whose anterior aspect is distal (posterior aspect is proximal). The reason for this is that it gives you a further degree of freedom.
When using the horizontal incision, it is easy to forget to take into account the anterior bow of the femur. This means that during nail insertion, the skin is distorted posteriorly. With the oblique incision, any horizontal translation is accommodated, or can be accommodated by extending the incision.
If the nail needs to be removed or the patient requires a more formal hip approach at a later stage, then this oblique incision can be easily incorporated to give you full access to the proximal femur. Horizontal incisions are not so versatile.

This is the ideal entry point for a Lateral Femoral Nail. Other nail designs typically use the tip of the Greater Trochanter. If you have an entry point that is any further lateral, then you can inadvertently ream the inner aspect of the greater trochanter. This is because the soft tissues (particularly in obese patients) push the instrumentation laterally.

Some surgeons use an awl to open the proximal femur. I prefer to use a 3.2mm threaded guide wire because if the initial awl position is wrong, it is harder to correct without falling into the hole that has previously been created.

The tip of the wire should be carefully positioned so that it is not on either the anterior, or more commonly, posterior cortex. This prevents inadvertent reaming of the inner cortex, which can be a problem when trying to introduce the ball nosed guide wire, as it gets stuck on the notch that has been created. In the AP view, the wire tip commonly sits on the medial cortex, so again care needs to be taken to avoid this technical error.

In this case, the wire was positioned so that it avoided the tumour and the weakened medial cortical bone.
The ruler is placed overlying the tip of the greater trochanter.

The end of the ruler is marked on the skin (overlying the tip of the greater trochanter). This is a useful tip, as sometimes the ruler needs to be moved slightly when taking an image at the knee to ensure it is aligned with the femur. If you haven’t made this mark, it is easy to question whether the ruler has moved and this requires the radiographer to re-image the hip.

The tip of the nail should finish at least at the superior pole of the patella, as the metaphyseal bone in this region is an area of weakness. Whenever there is a transition from diaphyseal to metaphyseal bone, this area is vulnerable to peri-prosthetic fracture.
The bending rigidity of a solid nail is proportional to the radius of the nail to the power 4.
The bending rigidity of a cannulated / hollow nail is proportional to the radius of the nail to the power 3 (i.e. outer radius minus the inner radius)

The soft tissue protection sleeve must be used. Not only does it protect the soft tissues from the starter flexible drill, but it sets the depth that the drill should be inserted to.

The soft tissue protection sleeve must be down to the greater trochanter, so that the correct depth is drilled.

Although the drill has a flexible shaft, it is being guided by a 3.2mm wire that is straight and fairly rigid. So although it is suggested that it will take the path of least resistance, it is wise to radiographically follow its’ path, otherwise you could end up somewhere unexpected.

The starter drill has a collar (A), this should be inserted until it touches the top of the soft tissue protection sleeve (B), to ensure that you have drilled the proximal femur to the correct depth.

The ball nosed guide wire is inserted with a ‘finger reduction tool’. This allows the wire to be passed safely past the area of interest.

In this case, the finger reduction tool handle has been rotated 180 degrees, so that the wire is safely passed away from the tumour. Inadvertent penetration of the tumour, could cause bleeding or perforation through the weakened cortical bone.

The ball nosed wire should sit centrally within the distal femur.

It is important to check the lateral image, as sometimes the ball nosed wire can sit anteriorly (due to the anterior bow of the femur or displacement of the fracture). This can lead to inadvertent reaming of the anterior cortex.
To remedy this, you can try to re-insert the ball nosed guide wire however, it commonly takes the path of least resistance and follows the previous track. I therefore use a blocking wire in the lateral plane (at least a 2mm K-wire but preferably 2.5mm). This is placed slightly anteriorly to where the ball nosed wire would like to go. As the ball nosed wire is re-inserted, it will hit the blocking wire and to pass the blocking wire, it must deviate and follow a new path. Additional wires can be used and stacked if necessary, like a staircase.

When inserting the reamer, it is very difficult to hold the power tool and easily thread it over the ball nosed guide wire. I recommend uncoupling the reamer shaft from the power tool, as this can be easily held in one hand and then threaded on to the guide wire.

An image of the femoral isthmus will help you determine the correct nail diameter. This information in combination with the audible and palpable ‘chatter’ as the reamer traverses the isthmus will help you decide.
For most nailing systems, one often reams 1.5mm greater than the diameter of the chosen femoral nail. With the LFN, I have found that over-reaming to 2mm instead, prevents the nail from getting stuck or requiring potentially excessive force to introduce it.

Once the reamer has been confirmed to be in the supra-patella region of the distal femur on the image intensifier, I recommended you note how much of the reamer shaft is still outside of the patient. In this case, the femur was the same length as the reamer shaft. Knowing how much of the reamer shaft is left, will allow you to consistently ream to the same depth, without having to take further x-rays.

More often than not, the nail packet opens at the wrong end and has to be cut open to access the threaded portion of the nail where the jig will attach. I have a strong dislike of handling the implants and treat all surgical implants like an arthroplasty surgeon would handle a joint replacement.

There are different ways to attach the nail to the jig however, the easiest method is to use the ‘rod pusher (blue handle)’. The rod pusher aligns the nail with the jig and the cannulated connecting screw. On the photo (marked A) is a notch in the nail and jig, to ensure that they are both correctly aligned with each other. Having tightened the cannulated connecting screw with the rod pusher, it is recommended to check the tightness with the hexagonal screwdriver (with a spherical head).

A: Hexagonal screw driver with a spherical head
B: Rod pusher (note the hexagonal screw driver section – just below the blue T handle)
C: Cannulated connecting screw
D: Radiolucent jig / handle
E: Intramedullary nail (note the notch in the nail corresponds with the tongue on the radiolucent jig)

The radiolucent aiming arm jig is connected and then the soft tissue protection sleeve and drill guides are inserted. The 3.2mm threaded guide wire is passed through the drill guide and it should pass concentrically through the nail hole. If it doesn’t, then the nail has to be systematically checked, to ensure that each junction is correctly seated. In other words: nail to handle; handle to radiolucent aiming arm; radiolucent aiming arm and drill sleeves. If it is still malaligned, then the jig may have become deformed from the previous operation and should be replaced. Failing this, then the nail should be replaced.

When inserting the nail, it should be prevented from making contact with the skin. Staphylococcus aureus is a common organism on the skin and routinely infects orthopaedic hardware. If the nail has not been touched and it is prevented from making contact with the patients’ skin, then I believe this reduces the risk of developing a deep infection.

There is an important difference when inserting this nail. It should be inserted with the aiming arm jig pointing vertically. As the nail is introduced, it gradually externally rotates as it advances down the femur. Do not try and rotate the nail, as it is designed to rotate by itself.

With gentle and continued blows from the hammer, the nail advances and gradually rotates. Just after the nail disappears under the patients skin, I would recommend removing the ball nosed guide wire.
If the ball nosed guide wire is embedded in the distal femur cancellous bone, there is a small risk that the wire could bend, as the nail advances. This makes wire removal through the cannulated nail very difficult. If this happens, attach the T-handle chuck to the ball nosed wire and with controlled force, it should be possible to pull the bent wire through the nail. If this fails, then the nail will have to be removed and the ball nosed wire straightened / removed from the distal end of the nail. Therefore try and avoid this situation by pulling the wire back, as the nail advances the last few centimetres.

Once the nail has been inserted to the correct depth and the holes in the nail align with the femoral neck (when using the recon mode). A single incision is made and both soft tissue protection sleeves are inserted including the drill sleeves and trochars.

Either wire can be inserted first. I prefer to have a low inferior screw that is just within the femoral neck. This means that the tip of the superior screw is closer to the centre of the femoral head and hopefully has a lower risk of superior migration / cutout.
Note where the nail is coupled to the insertion handle (A). The top of the nail should ideally not ‘stick out’ of the greater trochanter, as it can irritate the abductor muscles. If the nail is within the bone, then it can be lengthened with an end cap up to 20mm, to prevent any bone overgrowth.

The guide wire should be central within the femoral neck / head.

Both wires should be in the subchondral bone. The next step is to measure the wire length. From this image you can see that the soft tissue protection sleeve is not quite down to the bone surface and therefore 5-10mm will need to be subtracted from the measurement given by the depth gauge.

The wire length is measured remembering to account for the fact that the soft tissue sleeve wasn’t quite down to the lateral cortex.

The inferior wire has been removed because the drill is not cannulated. The superior wire maintains the position of the jig, so that the hole is drilled in the correct location. Prior to drilling, the depth is set with the drill stop (A).

The drill is larger in diameter than the guide wire, so it is prudent to double check with an x-ray that you are not drilling the inferior neck or calcar. Also before hitting the drill stop (i.e. within 5-10mm) I would recommend taking a further x-ray to ensure that the wire length hasn’t been incorrectly measured and the drill isn’t at risk of perforating the femoral head.

When inserting the screw, there is a mark on the screwdriver shaft (A) that indicates when the screw head should be down on the lateral cortex of the femur. At this point the screw should be slowly tightened to ensure that the lateral cortex isn’t fractured and the screw embedded in the bone.

I apply the same principle in not touching any of the implants (including the locking screws). Here a swab is held underneath the screw, just in case it uncouples from the screwdriver and tries to fall on the floor.

Things to note on this image are:
The tips of the screws should be within the subchondral bone and there is no joint penetration
The heads of the screws should rest on the lateral cortex
The screws should be parallel and pass through the nail i.e. no radiolucency either side
The top of the nail should not be too proud of the tip of the greater trochanter

On the lateral image:
Both screws should not penetrate the joint
Both screws should be parallel
Both screws should go through the nail

A true lateral is essential for inserting the distal locking bolts. The hole visualised has to be perfectly round. If it is elliptical and narrower top-to-bottom, then the C-arm needs to externally or internally rotate to compensate and change its’ rotation in the vertical plane. If the hole is narrower from proximal-to-distal, then the C-arm needs to rotate in the horizontal plane to become parallel with the nail.
Finally ask the radiographer to horizontally flip or rotate the image, so that moving the drill left or right correlates your hand movements with the x-ray appearance.
Some surgeons use a ring initially (the handle of a Trethowan retractor) to identify where the skin incision should be placed. I find that using the scalpel blade is more accurate and prevents a mis-placed skin incision from pulling against the drill bit and making it difficult to maintain the drill position.
Only incise the skin and deep dermis. Deep ‘stab’ incisions frequently catch a blood vessel which is then difficult to identify and coagulate.

The McIndoe scissors are the preferred instrument to deepen the track down to the bone. They have a narrow tip that can perforate through the iliotibial band. Once down to the bone, scrape the bone to displace any muscle and open the scissors wide and pull back in one clean manoeuvre. This creates a single tract from the skin surface down to the bone.

The tip of the drill has a spike that allows it to grip the bone and limits its ability to slip. If you apply too much pressure or are either superior / inferior to the equator of the bone, then the drill bit will slip.
When the drill tip is concentric with the nail hole, then the drill and power tool are aligned with the C-arm x-ray beam and the cortices are drilled.

The depth of the hole is measured.
Leave the depth gauge in situ while the locking bolt is mounted on to the screwdriver. Only remove it when you are ready to insert the locking bolt, as this will demonstrate the position of the hole and the correct angle for insertion of the bolt.

The process is repeated for the distal hole.

Once through the first cortex and the drill bit is within the nail hole, I recommend that you check with an x-ray that you haven’t hit the nail and skived either anterior or posterior to the nail. A Kochers forceps can be used to pull the drill bit, so that it aligns with the nail and you should not see it either side of the nail.
If the drill bit hasn’t gone through the hole and is sat just on the edge, then the Kochar can be used to ‘aim’ the drill bit towards the hole and then with very gentle taps from a hammer, the drill bit can be passed through the nail. It is then re-coupled to the power tool and the far cortex is drilled.

If using the distal oblique hole, the nail has to be locked both proximally and distally first. The leg is then externally rotated by approximately 30 degrees to leave the oblique hole in the horizontal position. If the nail hasn’t been locked both proximally and distally, then there is a risk of displacing a fracture.

An AP image confirms that the locking bolts are the correct length and have been correctly inserted.
Don’t forget the shape of the distal femur is a trapezium, so sometimes the locking bolt head or tip may appear to be embedded in the bone or short but are actually exactly the right length and are not going to cause any soft tissue irritation.

The wounds are washed out. A final check of haemostasis is made and the wounds are closed in layers.

The post operative AP radiograph of the hip demonstrates that the tumour has been successfully internally splinted.
I only use an end cap when the nail is short and within the bone. This adds length and means that nail isn’t overgrown when within the bone and thus difficult to find when trying to remove it.

The AP radiograph of the distal femur demonstrates that the nail is the correct length and has spanned the whole femur. It is also an appropriate diameter with cortical contact within the isthmus.