1 Bent vs straight nails topenlarge
Interference with the rotator cuff footprint
The entry point for a bent nail may go through the bony attachment of the rotator cuff. This bony defect in the footprint cannot be reconstructed later.
The entry point for a straight nail lies under the rotator cuff so the nail is inserted through the rotator cuff. This requires an incision, which should be made in the line of the tendon fibers which can then be closed effectively by a side to side suture.
Fixation in osteoporotic bone, fifth anchoring point
Due to the bone density in osteopenic bone straight nails provide a better fixation in the proximal humerus in the region of their entry point. Bent nails run through the greater tuberosity which has a lower bone density compared to the superior humeral head.
Interference with fracture lines
In proximal humeral fractures which consist of a fracture of the greater tuberosity the trajectory of bent nails often passes through the fracture line between the greater tuberosity and the humeral head whereas straight nails penetrate the humeral head medial to the fracture line.
Fixation pattern of screws
Straight nails run more medial in the axis of the medullary cavity. Therefore, it is possible to perform a direct fixation of the lesser tuberosity through the nail.
2 General considerations topenlarge
Correct nail entry point
A precise entry point of the humeral nail is crucial. For straight nails, the correct entry point is in line with the axis of the humeral shaft. An incorrect entry site results in malreduction of the metaphyseal fracture.
It might be difficult or even not possible to access the correct entry point if the humeral head is displaced severely into a varus position. Therefore, it is strongly recommended to expose the entry point by manipulating the humeral head. K-wire “joy-sticks” (as illustrated) or sutures through the rotator cuff insertions can be used to achieve this.
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 axillary nerve
The main structure at risk is the axillary nerve. The axillary nerve should be protected by limiting the incision to less than 5 cm distal to the acromial edge, by palpating the nerve, and by avoiding maneuvers that stretch the nerve during reduction and fixation.
In addition, any suspicious screw trajectory should be made to the bone with blunt dissection and checked with finger palpation if necessary.
Remember the course of the nerve when placing the screws depending on the chosen nail and/or position of the nail itself.
Tension band sutures in addition to nail
Sutures placed through the rotator cuff tendons and the bolts increase stability, and should be used as well as the nail and screws, particularly for more comminuted and/or osteoporotic fractures. With osteoporotic bone, the tendon insertion is often stronger than the bone itself, so that sutures placed through the insertional fibers of the tendon may hold better than screws or sutures placed through bone.
These additional sutures are typically the last step of fixation.
An anterolateral incision is recommended for nailing of proximal humeral fractures. The need for additional access depends upon fracture type.
AO teaching video: Proximal humerus – 3-part fracture – Reconstruction using the MultiLoc Proximal Humeral Nail
3 Reduction of humeral head topenlarge
Before opening the humeral entry point reduce the humeral head. A “joy-stick” technique, as illustrated, is helpful.
Alternatively, or in addition one can use stay sutures through the tendon of the rotator cuff in order to manipulate the humeral head.
4 Determination of entry point and opening of the canal topenlarge
Determination and exposure of entry point
The nail insertion site lies on the axis of the humeral shaft. It is located intraarticularly posterior to the tendon of the long head of the biceps within the cartilage. It is typically near the highest point of the humeral head. It is slightly anterior to the center of the greater tuberosity. A supraspinatus split is necessary.
Incise the supraspinatus tendon for approximately 3 cm over the foreseen entrance point posterior to the long head of the biceps. Retract the edges of the supraspinatus tendon with the help of stay sutures.
Insert a K-wire through the correct entry point and confirm proper placement by image intensification.
Open the humerus
A cannulated drill bit is recommended for opening the proximal humerus. This drill bit should be inserted over the previously placed guide wire. It should be advanced into the proximal medullary canal.
Alternatively, an awl may be used to open the humerus.
5 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.
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.
A K-wire placed through an aiming device may help to adjust the appropriate insertion depth.
Retrotorsion of locking device
In order to lock the nail in the correct trajectory, mount the aiming arm and swivel it approximately 25° anteriorly in order to follow the retroverted axis of the humeral head. (Due to the physiological retrotorsion of the humeral head, the axis of the humeral head is directed approximately 25° posteriorly to the condylar plane of the distal humerus.)
To obtain a true AP view of the proximal humerus, the forearm has to be rotated approximately 25° externally relative to the sagittal plane.
6 Proximal nail fixation topenlarge
The trocar for the planned screw fixation is placed through the aiming device, if necessary through a separate skin incision. Perform blunt dissection down to the bone so that the trocar may be placed without interposition of soft tissue.
Check once more the correct retrotorsion.
Drill with the calibrated drill bit carefully just to the level of the subchondral bone. The final position of the drill bit can be checked with the image intensifier. The screw length can be determined from the measurements of the drill bit.
Widen the screw hole in the lateral cortex
If necessary, a conical drill bit may be used to countersink the lateral cortex.
Attach the screw to the screw driver and insert the screw.
In some systems, as the one shown in this illustration, a screw-in-screw fixation is possible (see below). If so and if also intended, the plane of the handle of the screw driver should be horizontal and the arrow should point posteriorly once the final position of the screw is reached.
Using an additional trocar, K-wires can help to achieve more stability temporarily.
Insert further screws
Insert further screws using the aiming device according to the fracture pattern.
If necessary, use the screw-in-screw fixation for further stability.
Attach the centering sleeve to the already inserted screw, turn it anteriorly until it locks.
Insert the drill sleeve and predrill to the subchondral bone.
After length measurement insert the screw with the screw driver and torque limiter.
Calcar screw insertion
If necessary (such as varus fractures), insert a calcar screw through the aiming device in the way as described for the other screws.
7 Distal nail fixation topenlarge
Drill and determine length of locking screw
For distal locking, insert the trocar with the drill sleeve through one of the distal holes in the aiming device. 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.
8 Finalizing the nailing topenlarge
Insert end cap
The end cap prevents tissue from plugging the inner thread of the nail.
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.
Supplementary rotator cuff tendon sutures
Rotator cuff tension band sutures are placed through the dedicated holes of the bolts.