MIO - Bridge plating (Locking plate)

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 result in satisfactory indirect healing (callus formation). Occasionally, a larger wedge fragment might be approximated to the main fragments with a lag screw.

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, +/- circlage 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.

The patient may be placed in one of the following positions:

• Supine position with manual traction
• Lateral decubitus position
• Supine knee flexed 30°
• Scissor position

For this procedure a MIO approach is used.

Subtrochanteric fractures present a particular problem in terms of fracture reduction and alignment. Due to the strong pull of the iliopsoas muscle, the proximal fragment is flexed and externally rotated and therefore difficult to control. This may even require open reduction maneuvers to ensure a proper alignment.

If a closed plating technique is used, a preliminary reduction should be undertaken before plate insertion. Once the plate is attached to the proximal fragment, the definitive reduction with respect to length, rotation and axis can be achieved.

For the preliminary reduction several options are available:

• Lowering the proximal fragment by using external pressure with a mallet.
• A Schanz screw inserted into one of the main fragments.
• Use of a distractor / external fixator.
• Use of cerclage wiring

A mallet may be used, but this will be difficult if the proximal fragment is short.

A crutch can be used under the proximal end of the distal fragment.

A monocortical Schanz screw can be helpful in providing direct control of the displaced main fragments. It is advantageous when compared with reduction maneuvers through the skin.

After placement of two pins - one in the greater trochanter and the other in the shaft - the large distractor is attached. Attention must be paid so that the pins do not conflict with the later plate position.

In case of a closed procedure, every step of the reduction should be verified by image intensifier control.

The preliminary reduction is held by tightening the clamps of the large distractor.

To supplement a reduction of an intact wedge fracture, a cerclage wire may be very complimentary through a minimal incision.

AO teaching video: Application of the large distractor

A dedicated locking plate, pre-shaped for the proximal femur, is the implant of choice for this technique.

Depending on the extent of the fracture comminution and underlying bone stock (osteoporosis), the appropriate plate length is chosen. Sufficient bicortical screws (a minimum of three up to six) should be inserted in each main fracture fragment as necessary. Relative stability results from leaving plate holes empty over the fracture zone.

After the approach to the proximal femur has been performed, the plate is placed submuscular from proximal to distal. The attached wire guides facilitate this procedure. During this procedure, the surgeon should maintain contact between the plate tip and the bone. This ensures that the plate is in the correct lateral position with respect to the lateral aspect of the femur.

Three options are in use for preparation of the plate path in 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. (The tip of the plate can be used in a same manner).
• A soft-tissue retractor is available which serves the same purpose (pictured).

The proximal femoral plate is anatomically shaped to match the profile of the upper femur. First, the plate is adjusted optimally to fit the proximal fragment. Through the two attached wire guides, the proximal 2.5 mm guide wires are inserted into the proximal fragment.

The positions of the guide wires are verified under image intensification in both planes (AP and lateral).

The correct screw lengths are determined by measuring the remaining guide wire length, using the dedicated measuring device.

Cannulated 7.3 mm screws (locking or non-locking) are inserted over the guide wires into the proximal fragment.

Under image intensifier control the preliminary reduction is again checked in respect to axial alignment, length and, to a degree, the rotation (in more complex fractures the clinical judgment of the rotation becomes more important while the radiological findings in that respect is challenging to interpret).

This illustration shows the fracture incompletely reduced.

The approaches / stab incisions over the distal fragment are made according to the planned final screw placement.

Two blunt Hohmann retractors placed ventrally and dorsally around the femoral shaft can help to control the lateral position of the plate.

If the overall reduction is found to be satisfactory, the first conventional cortical screw in the distal fragment is inserted. This screw helps to reduce the bone to the anatomically shaped implant. Nevertheless, this screw should not fully be tightened, still allowing fine tuning of the plate position on the lateral aspect of the femur.

Once the most distal screw has been inserted, the first screw is fully tightened.

If the lateral position, prior to the placement of the second screw, is not correct the use of sterile bolsters is recommended.

In osteoporotic bone, the use of locking screws is advantageous.

According to preoperative planning, additional screws are inserted into the proximal and distal main fragments.

Close monitoring of the femoral muscle compartments should be carried out especially during the first 48 hours, in order to rule out compartment syndrome.

In all cases in which radiological control has not been used during the procedure, a check x-ray to determine the correct placement of the implant and fracture reduction should be taken within 24 hours.

Unless there are other injuries or complications, mobilization may be started on postoperative day 1. Static quadriceps exercises with passive range of motion of the knee should be encouraged. If a continuous passive motion device is used, this must be discontinued at regular intervals for the essential static muscle exercises. Afterwards special emphasis should be placed on active knee and hip movement.

Full weight bearing may be performed with crutches or a walker.

Wound healing should be assessed regularly within the first two weeks. Subsequently a 6 and 12 week clinical and radiological follow-up is usually made. A longer period may be required if the fracture healing is delayed.

Implant removal is not mandatory and should be discussed with the patient, if there are implant-related symptoms after consolidated fracture healing.