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 monitoring under image intensification.
This technique 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, direct manipulation would risk disturbing their blood supply. If the soft-tissue attachments to these 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 with the implant.
Mechanical stability, provided by the bridging plate, is adequate for gentle functional rehabilitation and results in healing with abundant callus formation.
Note on illustrations
Throughout this section generic fracture patterns are illustrated as:
Reduced and provisionally stabilized
It is important to restore axial alignment, length, and rotation.
Reduction can be performed with a fracture table, femoral distractor, external fixator, or with the implant.
The preferred method depends on the fracture and soft-tissue injury pattern, the chosen stabilization device, and the experience and skill of the surgeon.
2. Plate selection
A small (3.5 mm) or large narrow (4.5 mm) plate is chosen.
A locking plate is a good option for fractures with a short end segment. The plate does not need to be contoured precisely to fit the bone, as it functions as an internal fixator. Attaching it to the bone does not alter fracture alignment, as locking screws do not pull the main bone fragments to the implant. If cortical screws are used contouring is important.
A radiograph of the contralateral femur can help to decide between a straight or a curved plate.
A plate with a beveled end may be easier to insert.
Plate length and number of screws
The plates for a bridging technique should be longer than for conventional “anatomical” fixation, to distribute the forces more widely, as well as to provide sufficient stability.
A minimum of two and up to four bicortical screws should be inserted into each fracture fragment.
Relative stability results from leaving plate holes empty over the fracture zone.
Up to half the screw holes need to be filled with screws and no screws are inserted into the fracture zone.
3. Patient preparation and approach
Place the patient in a supine position on a traction table or a translucent table with a bump under the ipsilateral flank.
The use of a traction table can be beneficial in adolescents especially when operating without an assistant.
For younger children manual traction is often sufficient.
If a traction table is not used, folded linen bolsters under the fracture zone may facilitate reduction.
Pearl: Use a sheet around the opposite pelvis and attached to the side of the operating table to provide countertraction in the supine position.
5. Contouring and insertion of the plate
Contouring the plate
Contouring the plate over the fracture zone is not normally required.
It is necessary to contour the ends of a conventional plate used with cortical screws to address the shape of the proximal and distal femur.
A locking plate used as an internal fixator does not have to be contoured but slight contouring may be necessary to avoid soft-tissue irritation.
Direction of plate insertion
Insert the plate from the proximal end, if the fracture is located more proximally, or from the distal end, if the fracture is located more distally.
Preparation of the plate tunnel
Options for preparation of the plate path along the distal main fragment include:
Insert the tip of the plate and slide it extraperiosteally along the distal main fragment.
Insert a long pair of scissors, spread them, and then pull backwards.
Insert a periosteal elevator and slide it extraperiosteally along the distal main fragment.
Use the MIO instruments.
6. Reduction and fixation
Further adjustment is often needed after the preliminary reduction to achieve optimal alignment. In such cases, the final reduction will be achieved using the implant and further multistep reduction techniques.
Plate fixation to first main fragment
The order of screw insertion depends on the direction of plate insertion. In the following example, the procedure for a plate inserted through a proximal approach is shown.
Place the plate on the lateral aspect of the femur and the check the position with image intensification.
Insertion of the first screw
Insert the first cortical screw into the most proximal plate hole.
Insertion of the second screw
The position of the second screw will determine the lateral alignment of the plate on the proximal fragment.
Use a K-wire or Schanz screw to push the proximal fragment into position and achieve the correct alignment between the plate and the bone.
Alternatively, this can be achieved directly through a second incision, using a periosteal elevator.
Insert the second cortical screw.
Manual traction is often sufficient to align the distal femur to the plate.
A bump placed under the fracture site helps with sagittal fracture alignment.
K-wires can be used for provisional fixation of the plate.
Assessment of rotational alignment
Confirm rotational alignment of the femur clinically and radiographically before fixing the second fragment. 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 as well)
Fluoroscopy of proximal femur (lesser trochanter profile)