1 Principles topenlarge
Note on illustrations
Throughout this treatment option illustrations of generic fracture patterns are shown, as four different types:
A) Unreduced fracture
B) Reduced fracture
C) Fracture reduced and fixed provisionally
D) Fracture fixed definitively
Bridge plating uses the plate as an extramedullary splint, fixed to the two main fragments, leaving the intermediate fracture zone untouched. Anatomical reduction of intermediate fragments is not necessary. Furthermore, their direct manipulation would risk disturbing their blood supply. If the soft tissue attachments to the fragments are preserved, and the fragments are relatively well aligned, healing is enhanced.
Alignment of the main shaft fragments can be achieved indirectly with the use of traction and the support of indirect reduction tools, or indirectly via the implant.
Mechanical stability, provided by the bridging plate, is adequate for gentle functional rehabilitation and results in satisfactory indirect healing (callus formation). Occasionally, a larger wedge fragment might be approximated to the main fragments with a lag screw.
Bridge plate insertion
Bridge plates inserted through a minimally invasive (MIO) approach leave the soft tissues intact over the fracture site. The incisions are made proximally and distally, and the plate is inserted through a submuscular tunnel. This normally requires fluoroscopic intensifier monitoring.
It is important to restore axial alignment, length, and rotation.
Reduction can be performed with a single reduction tool (eg, large distractor), or by combining several steps (for example fracture table +/- external fixator, +/- reduction via the implant, cerclage wire etc.) to achieve the final reduction.
The preferred method depends on the fracture and soft-tissue injury pattern, the chosen stabilization device, and the experience and skills of the surgeon.
If a large fragment has separated from the fracture zone and impaled the adjacent muscle, direct reduction may be required.
2 Preoperative planning topenlarge
Generally speaking, plates for the bridging technique should be longer than for conventional open plating techniques to distribute the forces, and to provide relative stability.
The preoperative x-ray planning template is useful in determining the length of the LISS plate and the positions of the screws.
Number of screws
In healthy bone, five well placed monocortical screws are inserted to secure the LISS to the main femoral shaft fragment. As an alternative, three bicortical screws can be chosen, and these are recommended in osteoporosis.
3 Patient preparation top
The patient may be placed in one of the following positions:
5 Preliminary reduction topenlarge
Reduction by external fixator or distractor
Sometimes, manual traction is not sufficient to achieve and hold preliminary reduction.
If manual traction is not sufficient, the use of an external fixator can facilitate the reduction procedure and can provide temporary alignment and stability for the bridge plating procedure.
Proximal and distal fixator screws should be inserted carefully in order not to conflict with the later plating procedure. For this purpose, safe positions would be anterolateral or anterior on the femur.
If no traction table is used, folded linen bolsters under the fracture zone may facilitate the reduction maneuver.
AO teaching video: Application of the large distractor
6 Plate insertion topenlarge
Assembly of LISS insertion instruments
The LISS was a first generation locking plate with an external guide for locking screw placement. The LCP was the next generation, but it did not have an external guide for locking screw placement.
In this procedure we will demonstrate the insertion of the a LISS plate.
The two parts of the insertion guide are connected, and the fixation bolt is placed in hole A. Then, the insertion guide is placed on the LISS three-point locking mechanism.
The fixation bolt is inserted into the LISS and slightly tightened using the pin wrench. Next, the nut of the fixation bolt is threaded in the direction of the insertion guide and tightened slightly with the pin wrench.
For more stable fixation of the LISS to the insertion guide during insertion, a second stabilization bolt is introduced with the drill sleeve into hole B (and threaded into the LISS).
LCP or LISS insertion
The assembled insertion guide or handles are used to insert the LCP or LISS plate between the vastus lateralis muscle and the periosteum (= extraperiosteal space).
The plate is inserted through the lateral incision.
The LCP or LISS plate is advanced proximally under the vastus lateralis muscle, ensuring that its proximal end remains in constant contact with the bone. The distal end of the plate is positioned against the lateral condyle. To identify the correct position, the plates are moved proximally and then back distally until the plate fits the condyle.
Proper position check - Position on the distal femur
When the plate lies flat on the lateral surface of the condyle, it has been positioned correctly on the distal femur.
From the AP perspective, a K-wire, inserted through the sleeve of the insertion handle, must be parallel to the plane of the tibiofemoral joint (green dashed line). At that point, the preshaped plate is in the right position, presuming normal anatomy. This is beneficial to restoring the correct alignment in complex fracture patterns.
7 Inserting the proximal connecting bolt topenlarge
Through an incision over the most proximal plate hole, a connecting bolt is screwed through the insertion handle into the plate.
This creates a fixed parallelogram that facilitates further manipulation of the plate.
8 Preliminary LCP or LISS fixation topenlarge
Position on the proximal femur
It is very important to confirm the correct plate position proximally. Especially in the minimal invasive technique, this can be challenging. Even the use of an image intensifier does not guarantee an optimal position.
To overcome this problem, the proximal incision is enlarged, and the correct plate position is palpated with the index finger. The finger is placed on the anterior aspect of the femur, and the upper rim of the plate is brought into contact with the volar aspect of the finger.
Proximal guide wire insertion
If the length and rotation of the fracture fragments are correct, the proximal guide wire can be inserted after it has been verified that the fixator is on the midlateral aspect of the femur.
It is extremely important to establish correct placement of the guide wire, to ensure proper proximal insertion of the monocortical locking-head screws. After the proper length and rotation are assured, and appropriate positioning of the proximal portion of the plate on the midlateral aspect of the femur has been established, a proximal guide wire is inserted through the sleeve. It is still possible at this point to correct the sagittal plane alignment, as noted below. Small corrections of the adduction of the proximal fragment or of the varus/valgus alignment of the distal femoral condyle are possible.
Once the reduction has been successfully completed and the LCP or LISS plate has been positioned correctly, the locking-head screws can be inserted.
9 Screw insertion in the distal fragment topenlarge
Length of screws
The appropriate screw length can be determined by using a 280 mm long guide wire and an indirect measuring device, or with the help of the preoperative planning template.
The screws are inserted through the guide sleeves, which are passed through the aiming device, into the plate hole.
For the final locking of the screws, the use of the torque-limited screw driver is necessary.
10 Screw insertion into the proximal fragment topenlarge
Reduction of the proximal femoral shaft with LHS fixation
With the help of the pull reduction instrument (or a co-linear clamp), the desired position of the shaft, in relation to the plate, is secured. This is an important step because otherwise some displacement may occur during the insertion of self-drilling / self-tapping screws (note: this instrument has a 4.0 mm diameter which still allows for the insertion of a 5.0 mm locking screw into the same hole later on).
A syringe, filled with saline, can be attached to the drill sleeve to provide cooling during the bone drilling procedure.
By tightening the bolt of the pull reduction instrument, the shaft is drawn towards the plate.
11 Additional screw insertion topenlarge
Additional locking-head screws (LHS) are subsequently inserted both proximally and distally. In general, a total of five proximal and five distal LHS are placed for the LISS or 4 bicortical screws with the LCP. In case of severe osteoporosis, six proximal and six distal LHS can be used. Bicortical self-tapping LHS are recommended for shaft fixation in severe osteoporosis.
In simple fracture types, 2-3 plate holes should be left unused over the fracture zone to avoid high stress concentration of the implant.
Final screw insertion
After detachment of the insertion device, a final screw can be inserted into the distal fragment through the central hole in the distal portion of the plate.