1 Principles topenlarge
Bridge plating (or biological plating) uses the plate as an extramedullary splint fixed to the two main fragments while the complex fracture zone is left untouched. Anatomical reduction of the shaft fragments is not necessary. Furthermore, it risks disturbing the blood supply. If the soft tissue attachments are preserved, and the fragments are relatively well aligned, healing is predictable.
Reduction can usually be achieved indirectly utilizing distraction.
Mechanical stability, provided by the bridging plate, is adequate for indirect healing (callus formation). Occasionally, a larger wedge fragment might be approximated to the main fragments with a lag screw.
Lag screws should be avoided when there is significant comminution.
Bridge plate insertion
Bridge plates can be inserted either with an open exposure, or through a minimally invasive (MIO) approach, which leaves soft tissues intact over the fracture site. The latter requires fluoroscopic monitoring. With open bridge plating, it is important to preserve soft-tissue attachments to the fracture fragments. To do this, stable provisional reduction (with external fixation, large distractor, or maintained manual traction), and minimal exposure and manipulation of the fracture zone are important. The bridge plate is applied through an incision just wide enough for the plate.
It is important to restore axis alignment and rotation. A little shortening of 1 or 2 cm can be accepted, and with extreme comminution may improve bone contact.
Exceptionally, a large fragment has been separated from the fracture with its sharp end impaled in the adjacent muscle. This may need to be repositioned with protection of soft tissue attachments.
2 Plate position topenlarge
The humeral shaft has an anterolateral, a posterior, and a medial surface to each of which a plate can be applied. The location of the fracture will determine where the surgeon chooses to apply a plate to the humerus. The position of the plate is selected according to fracture location, and the length of proximal and distal main segments.
The location should allow sufficient plate length on both proximal and distal segments, with a minimum of 4 holes for each.
An anterolateral plate fits well from very proximally to the distal fifth of the humerus.
The posterior surface is difficult to access proximally and is best suited for middle and distal third fractures. Once a location for the plate has been selected, the surgical approach is determined by that location. For proximal fractures, an anterolateral plate location and anterolateral surgical exposure are usual. For distal fractures, a posterior plate location is preferred. This area can be accessed with either a posterolateral, or a posterior, approach. In the central portion of the humerus, the plate can be applied to the anterolateral, lateral, or posterior surfaces, with the approach dependent on the preferred plate location.
The medial surface is generally only used for complex reconstructive procedures, ie vascular repair in complex fractures.
An anterolateral approach is chosen for proximal and middle third fractures, and allows supine patient positioning.
The lateral approach may also be used, particularly if the most proximal part of the humerus need not be exposed.
Distally, the plate may lie deep to the radial nerve.
A posterior approach will generally be chosen for more distal fractures.
It is important to protect the radial nerve and its accompanying vessels in the spiral groove. Typically, a posterior plate must be placed underneath the radial nerve, to gain proximal bone anchorage.
(a) It is possible to extend an anterolateral approach to access the posterior surface of the distal humerus.
(b) It is mandatory to record accurately in the operation record the exact relationship of the radial nerve to the plate - either by a precise drawing, or by recording the plate hole numbers (counted from proximal to distal) where the nerve lies. This will reduce the risk of accidental nerve damage if the plate should ever need to be removed.
3 Reduction topenlarge
Reduction should begin with limb realignment. This manipulative reduction takes advantage of soft tissue tension. Traction on the distal humerus restores bone length and tension in the soft tissues, and realigns the axis. Rotation must also be corrected.
Interposed soft tissue may interfere with bone contact. If so, this will need to be cleared by direct exposure. Preserve as much soft tissue attachment as possible.
Reduction by external fixator or distractor
Particularly with comminuted fractures, use of an external fixator or distractor can provide alignment and stability for bridge plating without disturbing the soft tissues at the fracture site.
Proximal and distal pins should be inserted outside the planned plate location, through small open wounds to protect nerves and vessels.
Complete reduction may require additional correction of angulation or rotation.
Folded linen “bumps” under the fracture often help.
Remember that alignment of comminuted fragments need not be anatomical, and that efforts to manipulate them often injure their blood supply.
Generally, soft tissue attachments will bring these fragments into appropriate position as the proximal and distal portions of the humerus are brought into appropriate alignment and fixed.
Occasionally, a lag screw through a plate or major humeral segment can be used to improve fracture fragment approximation.
4 Plate fixation topenlarge
Choice of implant
As bridge plating spans a long part of the bone, the length of the implant has to be chosen accordingly. Usually a narrow large fragment plate is chosen.
The thin cortex of the humerus compromises screw fixation. Particularly with osteoporosis, it is safer to fill all the screw holes. Multiple screws add torsional stability and decrease the risk of failure.
An angular stable plate is a good option in osteoporotic bone. Also, with short proximal segments, consideration should be given to angular stable plating with a long blade plate or locking compression plate, with screws in the humeral head.
In the past, the broad plate has been advised to allow staggered screw holes. This is not necessary, but the screws may be inserted divergently to achieve this effect on the far cortex.
Contouring the plate
Depending upon the planned plate location, some contouring of the plate may be necessary. This is true distally on the posterior surface, and also centrally on the anterolateral surface.
Sometimes twisting the plate around the shaft of the humerus provides better fit and allows a longer plate.
To match the orientation of the anterolateral surface of the distal humerus, the distal end of the plate will need to be twisted internally.
Contouring is aided by first achieving a provisional reduction with the large distractor or external fixator. A malleable template is helpful for matching contours of proximal and distal segments.
Apply the properly contoured plate to the proximal fragment, so that it is properly aligned with the humeral axis.
Applying the plate to the distal fragment will correct rotation and axial
In the lateral view the plate must be parallel to the longitudinal axis of the humerus.
Often the plate can be held manually against the bone, and the screw inserted.
Sometimes it is helpful to clamp the plate to proximal or distal portions of the humerus with a bone forceps as shown.
Another option is the use of the push-pull reduction device from the LCP set as shown here.
If fragment length permits, use four screws in each main fragment. For both major fragments, place one screw as close as practicable to the fracture, and the second at the end of the plate.
Confirm the reduction and plate position under image intensification after inserting two screws in each fragment. Fill in the remaining holes with bicortical screws.
Check rotational alignment by physical exam.