1 Principles topenlarge
Bridge plating uses the plate as an extramedullary splint, fixed to the two main fragments, while the intermediate fracture zone is left untouched. Anatomical reduction of the shaft fragments is not necessary. Furthermore, direct manipulation risks disturbing their blood supply. If the soft tissue attachments are preserved, and the fragments are relatively well aligned, healing is predictable.
Alignment of the main shaft fragments can usually be achieved indirectly utilizing traction and soft tissue tension.
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 are multiple fragments.
Bridge plate insertion
Bridge plates can be inserted either with an open exposure that respects soft tissue attachments to the fractures, or through a minimally invasive (MIO) approach that leaves soft tissues intact over the fracture site. In this case, incisions are made proximally and distally, and the plate is inserted through an extraperiosteal tunnel. This should be done with fluoroscopic monitoring.
It is important to restore axial alignment and rotation. A little shortening of 1 or 2 cm can be accepted in the humerus, and in complex multifragmentary fractures may improve bone contact.
Exceptionally, a large fragment has been separated from the fracture with a sharp end impaled in the adjacent muscle. This may need to be repositioned directly with protection of soft tissue attachments.
2 Plate position topenlarge
The humerus 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. For minimally invasive osteosynthesis (MIO) only the anterolateral surface is applicable.
The location should allow sufficient plate length in the proximal and distal segments, generally a minimum of 4 holes each. An anterolateral plate may be less well suited for the very distal humeral shaft.
3 Plate selection and preparation topenlarge
Choice of implant
As bridge plating should span a long section of the bone, the length of the implant has to be chosen accordingly. Usually a narrow large fragment plate is chosen.
An angular stable (locking) plate is a good option in osteoporotic bone and for fractures with a short end segment. Such a plate need not be contoured precisely to fit the bone since it functions as an internal fixator. Attaching it to the bone does not alter fracture alignment, since the screws do not pull the main bone fragments to the plate.
Contouring the plate
Minimal contouring will be necessary over the fracture site. However, it may be helpful to contour the ends to fit the bone where the plate will be affixed.
Sometimes, the use of a helical plate is helpful for the proximal humerus. The plate can be spiralled around the proximal humerus from laterally under the deltoid to anteriorly under the brachialis.
Twisting the plate can also be useful distally. 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 using the large distractor or an external fixator. A malleable template is helpful for matching contours of proximal and distal segments.
Plate contouring for proximal humerus
To provide maximal fixation proximally, a helical plate configuration should be used. The plate can be precontoured on a plastic model, adjusting for patient’s size if necessary. The proximal end of the plate fits on the lateral surface of the greater tuberosity, and the twist in the plate allows it to come to lie on the anterior surface of the humerus, distal to the deltoid insertion.
4 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, preserving 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. For this intraoperative purpose, careful positioning of the pins outside the safe zones is acceptable.
Complete reduction may require additional correction of angulation or rotation.
Folded linen “bolsters” 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 positions as the proximal and distal portions of the humerus are brought into correct alignment and fixed.
Occasionally, a lag screw may be used through the plate to capture a large fracture fragment and improve its reduction.
5 Percutaneous (MIO) plate insertion topenlarge
In this illustration, the large distractor is used for intraoperative stabilization. Its pins were placed percutaneously under direct vision through the adjacent incisions.
Slide the plate along the bone through the prepared extraperiosteal tunnel, and deep to the overlying soft tissues. Stay anterior or even anteromedial on the humerus in order to avoid the radial nerve.
Confirm plate position using image intensification.
Here an LCP, with 2 attached drill guides as handles, is used to create a submuscular tunnel from distal to proximal.
Plate insertion for proximal fractures
This plate is passed from proximally to distally underneath the axillary nerve, with careful retraction.
In the illustrated case, the limited deltopectoral incision has been used to secure the distal end of the plate.
6 Plate fixation topenlarge
When the plate fits satisfactorily against the proximal segment, it can be attached provisionally with a single bicortical screw or push-pull reduction device.
Confirm reduction and plate position with image intensification. Remember to check external appearance for alignment, particularly rotation.
If reduction and plate position are satisfactory, insert the remaining proximal and distal screws, using at least two or three screws in each end. More screws may be safer with osteoporosis or unreliable patients.
Sometimes percutaneous insertion of an additional screw may enhance stability.
7 Plate fixation - a further example top
Provisional plate application
In this example, a plate is inserted minimally invasively from distal to proximal, attached first to the proximal segment, and then finally to the distal.
When the plate fits satisfactorily against the proximal segment, it can be attached provisionally with a single bicortical screw or a push-pull reduction device.
Confirm reduction and plate position with image intensification. Remember to check the external appearance for alignment, particularly rotation.
Proximal bone and plate alignment and fixation
Once the plate has been attached to the proximal fragment, it should be checked with the fluoroscope to see that it is properly aligned. In the lateral view the plate must be parallel to the longitudinal axis of the humerus. If alignment is satisfactory, insert a second screw to secure the plate proximally in this correct position.
Distal bone and plate alignment and provisional fixation
Once the plate is satisfactorily fixed proximally, the distal fragment is brought into alignment against the plate.
Applying the plate to the distal fragment should correct rotation and axial alignment. This must be confirmed with a fluoroscope.
Through the distal incision, the plate is attached, first provisionally, and then definitively. Often the plate can be held manually against the bone, and one screw inserted. If the alignment is satisfactory, add a second screw, and reconfirm alignment.
Sometimes it is helpful to clamp the plate to the humerus with a bone forceps as shown. Carefully pass the forceps close against the bone during application in order to avoid injury to adjacent nerves.
Another option is the use of the push-pull reduction device, from the LCP set, as shown here.
At least two or three screws should be inserted at each end. More screws may be safer with osteoporosis or unreliable patients. For both major fragments, one screw should be placed as close as practicable to the fracture, and the second at the end of the plate. Bicortical screws can be placed in any additional holes as desired. Percutaneous screw placement will avoid additional exposure.
Final fluoroscopic examination in two planes for alignment and screw length is recommended.