1 Principles topenlarge
Important module-wide statement
Where appropriate, a “generic” fracture zone will be illustrated and not necessarily the specific fracture morphology under consideration. Where the fracture morphology determines the fixation technique, the specific morphology will be shown.
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 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.
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, 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 Preliminary reduction topenlarge
Reduction by external fixator or distractor
Sometimes, manual traction is not sufficient to achieve and control preliminary reduction.
Then the use of an external fixator facilitates the reduction procedure and provides alignment and temporary stability for the bridge plating procedure.
Proximal and distal pins should be inserted carefully in order not to conflict with the later plating procedure. For this purpose, anterolateral or anterior positions on the femur are safe.
If no traction table is used, folded linen bolsters under the fracture zone may facilitate the reduction maneuver.
3 Plate fixation to distal fragment topenlarge
Guide wire insertion
As a first step, a guide wire for the condylar screw is inserted into the distal femur.
This is an extremely important step, because it determines the later plate positioning in two planes.
The guide wire for the cannulated condylar screw is inserted into the condylar mass from laterally. The entry point lies anterior to the midpoint between the anterior and posterior edges of the lateral femoral condyle, in line with the femoral shaft axis, and 2 cm proximal to the knee joint.
The guide wire must be parallel to the plane of the tibio-femoral joint (line A) and, at the same time, parallel to the plane of the patello-femoral joint (line B).
Checking correct position of the guide wire
The correct positioning of the guide wire must be checked using image intensifier fluoroscopy. The depth of guide wire insertion is crucial. Remember that the cross-section of the distal femoral condylar mass is trapezoidal and slopes markedly on the medial side. The tip of the guide wire should just engage the medial cortex, and so will appear short of the medial condylar cortex on the AP intensifier image.
Screw length measurement
Next, the surgeon slides the direct measuring device over the guide wire and determines guide wire insertion depth and, thereby, the length of condylar screw required.
After assembling the DCS triple reamer and setting the reamer to the correct depth, the hole for the condylar screw is reamed over the guide wire.
Condylar screw insertion
First, the condylar screw is inserted to its final position. The T-handle is lined up parallel to the femoral shaft axis in order to ensure an adequate plate placement.
Now the T-handle is detached and the plate barrel is placed over the screw shank. Afterwards, the T-handle is reconnected to the screw.
4 Plate fixation to proximal fragment topenlarge
Verification of reduction
The preliminary reduction is checked with respect to axial alignment and length, and to a degree rotation. Before fixation to the proximal fragment, it is often advisable to insert a cancellous screw into the most distal plate hole to prevent rotation of the plate about the axis of the condylar screw.
Insertion of first screw into proximal fragment
Two blunt Hohmann retractors placed ventrally and dorsally around the femoral shaft can be helpful to control the lateral position of the plate.
If the overall reduction is found to be adequate, the first cortical screw in the proximal fragment is inserted without being fully tightened. This still allows for the plate position to be fine tuned.
Pearl: final reduction
In case the lateral position prior to the placement of the second screw is inadequate, the use of sterile bolsters is recommended.
Insertion of second screw into proximal fragment
The lateral plate position can be confirmed by palpation.
Once the most proximal screw has been inserted, the first screw in the proximal fragment is fully tightened.