1 Principles topenlarge
Correct nail entrance point
A proper and precise entrance point of the humeral nail is crucial. An incorrect entry site results in malreduction of the metaphyseal fracture.
Preliminary reduction of the fracture helps with identification of the correct nail entry site. K-wire “joy-sticks” (as illustrated) or sutures through the rotator cuff insertions aid with reduction.
Reduction of the metaphyseal fracture component
If the entry point has been chosen correctly, insertion of the nail will help reduce the fracture.
Protection of the axillary nerve
The axillary nerve is at risk of being injured by placement of distal locking screws of some humeral nails. The screw tract should be made to the bone with blunt dissection, checked with finger palpation if necessary.
Note the danger zone for screw placement, between 5 and 7 cm distal to the lateral edge of the acromion.
An anterolateral incision is recommended for nailing of proximal humeral fractures. The need for additional access depends upon fracture type. Small separate stab incisions can be used for A2 fractures and extension (up to 6 cm) of the anterolateral incision may be needed for B- or C-type fractures.
2 Determination of entry point and opening of the canal topenlarge
Determination of entry point
The nail insertion site lies on the axis of the humeral shaft. It is located at the bone-cartilage junction of the humeral head. It is not more lateral on the greater tuberosity. Therefore, a supraspinatus split is necessary.
It is slightly anterior to the center of the greater tuberosity.
Be aware, that the correct entry point depends on the type and design of nail used.
Insert a K-wire through the correct entry point and confirm proper placement by image intensification.
Open the humerus
A cannulated awl is recommended for opening the proximal humerus. This awl can be inserted over the previously placed guide wire. It should be advanced into the proximal medullary canal.
Pitfall: hidden entry point
If the humeral head is abducted or externally rotated, the entry point is under the acromion. This is typical with varus malaligned fractures.
One has to reduce the humeral head before opening the humeral entry point. A joy-stick technique, as illustrated, is helpful. Alternatively, sutures though the rotor cuff can be used in order to manipulate the humeral head.
3 Nail insertion topenlarge
Mount nail on insertion handle
The humeral nail is mounted on an insertion handle. The nail must be rotated correctly relative to the insertion handle.
If an angled nail is used (as illustrated) ensure that the apex of the nail curvature points away form the insertion handle.
Insert nail and reduce fracture
Insert the nail with slightly rotating movements down to the metaphyseal fracture line. Pass the fracture zone under image intensification and make sure that the nail enters the distal fragment properly.
Make sure the proximal end of the nail is placed beneath the bony surface of the humeral head.
No protrusion of the nail may be tolerated. Confirm with appropriately oriented C-arm images that the nail is below the bone.
The nail illustrated has a transverse spiral blade. At the recommended depth, the spiral blade should lie between the middle and lower third of the humeral head. Depending upon the selected humeral nail, different preoperative planning is necessary for its locking devices.
Retrotorsion of spiral blade/screw
In order to lock the spiral blade, mount the aiming arm and swivel it approximately 25° anteriorly in order to follow the retroverted axis of the humeral head. (The humeral head axis is directed approximately 25° posteriorly to the condylar plane of the distal humerus.)
Within the humeral head, the spiral blade should be placed at the transition of the middle to the lower third, slightly below the equator.
Mount aiming device and insert trocar combination
Mount the aiming device in the insertion handle. Confirm that the retroversion angle is correct. Make a skin incision for the aiming device, dissect the muscles bluntly down to the bone, and fully insert the trocar.
Insert guide wire
Check once more the retrotorsion of the handle.
Remove the central trocar and drill the guide wire for the spiral blade onto the medial cortex of the humeral head.
The position of the guide wire can be checked under image intensification.
Be aware not to perforate the humeral head in order not to insert a too long spiral blade.
Determine length of spiral blade
Determine the correct length of the spiral blade with the appropriate depth gauge.
Open the lateral cortex
Perforate the lateral cortex with the appropriate cannulated drill.
Insert spiral blade
Attach the spiral blade to the inserter and introduce both over the guide wire.
Align the handle of the inserter parallel to the aiming arm.
The initial rotation of the T-handle of the spiral blade inserter relative to the aiming arm depends on patient anatomy. If the distance from the lateral cortex to the nail is less than 10 mm, start the inserter slightly clockwise from parallel. If the distance from the lateral cortex to the nail is more than 10 mm, start the T-handle slightly counter-clockwise from parallel.
By applying light controlled hammer blows to the connecting screw, advance the spiral blade to the desired depth. This causes the handle to rotate 90°.
Monitor the depth of the spiral blade with image intensification. If attaching sutures to the spiral blade, pause when the spiral blade is approximately 1.5 cm to 2.0 cm short of its intended position so that the suture ends can be placed through the appropriate holes in the base blade.
Check position of spiral blade
Check the position of the spiral blade by image intensification.
Pitfall: captured bicipital tendon
If the chosen nail has locking screws that might pass through the bicipital groove, be careful that they do not trap the bicipital tendon.
Drill and determine length of locking screw
For distal locking, insert the two-piece trocar combination (aiming arm). Through an appropriately placed trocar, drill through both humeral cortices until the bit just breaks through the medial cortex, and read the depth from the drill bit. Alternatively, a depth gauge can be used.
Insert a locking screw through the trocar. A second screw is recommended, especially in osteoporotic bone.
Pearl: make one incision large enough to allow palpation of the axillary nerve.
Insert the end cap
The end cap prevents tissue from plugging the inner thread of the nail. Furthermore it offers the option of angular stability, by compressing the spiral blade.
End caps are available in different sizes and can, if necessary, be used to extend the nail. The top of the end cap must not protrude above the surface of the bone.
Repair rotator cuff
Suture the supraspinatus split.