The cartilage-covered head fragment is fixed by two K-wires which are held by the humerus block. This block, in the form of a cylinder (Fig. 3.2) is fixed onto the shaft of the humerus by a cannulated screw while it is held by the guiding instrument (Fig. 3.3). The block holds two K-wires of up to 2.5 mm in diameter. These intersect at an angle of 25° proximal to the block and run through the block at an angle of 35° to the base of the cylinder. After the K-wires are positioned, they are locked inside the block with a grub screw to prevent migration. In this way, a three-point support of the K-wires is granted: within the block, at the lateral cortex of the humeral shaft and in the subchondral bone of the humeral head. This allows for both rotational and axial stability.

In cases of three- or four-segment fractures, with displaced tuberosities, they are reduced and fixed percutaneously by cannulated screws of 3 mm in diameter. The main tool here is a cannulated drill which basically looks like a cannulated K-wire. It holds a guide wire of 1.1 mm diameter, which completes its tip. This way, it can be used for fragment’s reduction and fixation just like a regular K-wire. Once, a satisfactory reduction is achieved, the drill is removed while the guide wire remains in place. Then, a cannulated screw of desired length is slid over the guide wire which can be removed when the screw is in place (Fig. 3.3).

The patient is placed in a beach-chair position with the upper body elevated at 30°. The affected shoulder must slightly overlap the edge of the table and the lower arm should be flexibly covered so that it can be moved freely during surgery.

When one image intensifier is used, it should be placed behind the head of the patient, just next to the operating table, thus also allowing for an axial view by tilting the device.

If, as an alternative, two image intensifiers are used, one is positioned as described above (for the axial view) and a similar device is placed on the opposite side of the patient for the a.p. view, similar to the arrangement for, e.g., a femoral neck screw.

In the first step, the humerus block is placed 5 cm below the subcapital fracture (Fig. 3.5). Through a 3 cm skin incision and sharp dissection of the subcutaneous tissue, the deltoid fibers are split by blunt dissection. The block then has to be fixed in the middle of the lateral face of to the humeral shaft. In order to ensure correct lateral positioning, an assistant must hold the arm in neutral rotation. After checking the position with the image intensifier, a 1.2 mm K-wire is introduced through the center hole of the block and drilled though both the lateral and medial cortex of the humeral shaft. Now, before placing the cannulated center screw, the position of this guide wire should be checked in axial view to ensure that it is positioned in the middle of the shaft (Fig. 3.6). If the block was placed too far anterior or posterior, it could happen that one of the two K-wires would not run intramedullary, but tangential to the outer cortex of the shaft and miss the head fragment. So when the guide wire for the center screw is placed correctly, the lateral cortex of the shaft is perforated by a cannulated drill, while the inner cortex is not completely perforated, so the guide wire won’t be lost while retracting the drill. As the next step, the block is fixed to the humeral shaft by a cannulated cortical screw.

However, this central screw, which is available in various lengths, will not be firmly tightened initially. Because the angle at which the 2.5 mm K-wires run through the block is set at 35° in the coronal plane, the point that can be reached by the tips of the K-wires is more or less preset. In cases where the block was positioned a bit too far distal to the fracture level, they would not reach the cranial part of the humeral head. Therefore, the center screw of the block is initially not tightened for maximum purchase, so the block can be tilt in the coronar plane. Thereby the aiming point of the K-wires can be adjusted.

The guide sleeves for the K-wires are placed in the setting instrument. Via two stab incisions at the lateral upper arm, they are pushed forward to touch the humerus shaft. Now two K-wires of 2.5 mm diameter are inserted and driven into the shaft just below the fracture. In case the two K-wires reach the lateral cortex of the humeral shaft at a very flat angle, as an alternative, the cortex of the shaft can be perforated with a 2.5 mm drill in order to prevent the K-wire tips from sliding cranially along the shaft, which avoids multiple drilling attempts.

Already at this point of the procedure, the target direction of both the K-wires must be correctly set: first in the coronal plane, then in the sagittal plane. The latter position of the K-wire tips in the coronal plane is determined by tilting the setting instrument that holds the block (as described above). The tips of the K-wires must not point towards the glenoid, but be positioned in the middle, between the cranial pole of the humeral head and the top edge of the glenoid. Otherwise, the glenoid may be endangered by perforating K-wires, once the head fragment settles to gain contact to the humeral shaft. This could cause glenoid abrasion when passive or active motion is allowed.

For orientation in the sagittal plane, as above mentioned it is most important that the center screw that holds the block was positioned in the middle of the humeral shaft. When correctly positioned, the lateral humeral epicondyle as the reference point shall lie in the middle of the lateral ends of the K-wires that outstand their guiding sleeves.

After both K-wire tips are inserted just below the level of the fracture (Fig. 3.7), the precise reduction is done. Based on the author’s experience, like other fractures, proximal humerus fractures can practically be classified as varus and valgus types which are determined by the position of the head fragment. Additionally, impacted fracture types can be differentiated from avulsed ones. In the following section, four of the most common fracture types [10] based on these considerations are outlined, and the need for miscellaneous techniques of reduction and fixation are explained. Hereby, practically all relevant steps of percutaneous reduction maneuvers to treat proximal humerus fractures will be described. If needed, they can be combined with fracture types that differ from those outlined below.