The ESIN method involves closed reduction and internal fixation with elastic nails.
It is difficult to treat shaft fractures of the distal third with retrograde nail insertion as the nail entry sites are too close to the fracture and the configuration of the nails does not produce sufficient stability.
Using an antegrade nail construct will provide sufficient stability in these fractures.
2. Instruments and implants
Instrument set for ESIN
2.5–4.0 mm elastic nails
Awl or drill
End caps and insertion device
The end cutter is useful to avoid sharp ends and soft-tissue irritation.
For optimal stability, the nail diameter should be between 33% and 40% of the narrowest part (isthmus) of the medullary canal.
Both nails need to be of the same diameter.
Pearl: To estimate the optimal nail diameter place the selected nail on the leg parallel to the bone and check with an image intensifier (as shown in the illustration). For later precontouring mark the level of the fracture site on the nail.
3. Patient preparation and approach
Place the patient in a supine position on a traction table or radiolucent fracture table.
The radiolucent fracture table has the advantage that the leg can be freely manipulated during the procedure. Muscle forces can be neutralized by flexing the knee with a support underneath.
When positioning the patient check the rotational alignment of the uninjured femur.
The usual entry points are 0.5–1 cm distal to the greater trochanteric growth plate.
Entry points should be at least 2 cm apart in the axial plane and at least 1 cm apart in the lateral plane. If they are too close, the cortex may split during the insertion of the nails.
There is a lower risk of iatrogenic fracture if both entry points are made in the metaphyseal bone proximal to the lesser trochanter. Alternatives include entry points in the lateral aspect of the greater trochanter.
Proximal entry point
Place the awl or drill directly onto the bone and perforate the near cortex, under direct vision, perpendicular to the bone.
Do not hammer the awl to avoid perforation of the far cortex.
When the medullary canal is entered, lower the awl or drill 45° to the shaft axis. Advance it with oscillating movements to produce an oblique canal.
Second entry point
Enter the medullary canal at the distal entry point with an identical technique.
5. Nail insertion
Decide whether the crossing point of the nails is to be proximal or distal to the fracture site.
Crossing the nails at the level of the fracture must be avoided.
Precontour both nails in the distal third with the apex at the predetermined level.
The maximum nail bend should be at the level of the fracture about three times the diameter of the medullary canal.
Insert the nail through the proximal entry point into the intramedullary canal and advance it towards the fracture site with an oscillating maneuver.
Pearl: Insert the nail with the tip perpendicular to the shaft axis until the far cortex is felt. Rotate the nail 180° and advance it using the curved side of the tip.
If the tip is stuck in the far cortex and cannot be advanced, remove the nail and bend the tip to give a slightly more pronounced curvature.
Pearl: A short working length (3–5 cm) between the entry point and the inserter improves control of the nail during insertion.
Insert the second nail into the distal entry point and advance it towards the fracture zone.
Once it has good contact with the opposite cortex, with the tip having advanced about two-thirds distally in the medullary canal, the contour of the nail is changed to an S-shape with the following maneuver:
Rotate the nail 180°.
Bend the proximal portion of the nail, which is outside the bone, in the opposite direction to the previous bend.
Apply a constant bending force whilst inserting the nail.
This produces an S-shape, which will provide contact with the lateral cortex at the fracture site and with the medial cortex of the proximal third of the femoral shaft.
Pitfall: Make sure that the second nail has not crossed the first more than once to avoid the corkscrew phenomenon.
If this happens reinsert a new nail.
6. Distal fragment advancement
Advance the first nail past the fracture zone and into the distal fragment with an oscillating maneuver.
Advance the second nail in a similar manner.
If it is difficult to advance either nail while it is positioned against the cortex, rotate the tip towards the center of the bone and advance it across the fracture zone.
If this is unsuccessful use a bone hook or Steinmann pin through a small incision.
Open reduction (through a limited lateral approach) may be necessary if closed reduction cannot be achieved.
Advancing the nails through a floating segment
Advance the first nail past the fracture site through the floating segment and into the distal fragment with gentle hammer blows.
This avoids rotation and splitting of the middle segment.
Advance the second nail in an identical manner.
Pitfall: Iatrogenic fractures of a floating segment reduce axial stability and end caps are recommended if this occurs.
Once the nail has crossed the fracture, rotate the nail tip to return to the initial position to achieve satisfactory reduction.
If necessary other reduction tools may also be used.
A wedge fragment does not need to be reduced anatomically.
If the fracture is axially unstable, end caps are recommended.
Assessment of rotational alignment
Confirm rotational alignment of the femur clinically and radiographically. This can be done by:
Fluoroscopy of the fracture site (matching shaft diameters)
Comparing internal and external rotation to the contralateral side (consider preparing and draping the uninjured side)
Fluoroscopy of proximal femur (lesser trochanter profile)