1 Principles top
A2 fractures are impacted surgical neck fractures without comminution. If the fracture plane is oblique and long enough, they may often be fixed satisfactorily with lag screws after closed reduction.
Disimpaction is the key to successful reduction of A2 fractures.
After reduction, alignment should be correct in both sagittal and coronal planes. Rotational alignment must also be correct.
Risk of axillary nerve injury
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. Remember the course of the nerve when placing K-wires.
2 Reduction and preliminary fixation topenlarge
Since the fracture is not exposed, the surgeon should be skilled at closed reduction maneuvers.
Distal traction, perhaps augmented with increased angulation, will help to disimpact the fracture.
Use of an elevator
A small incision allows incision allows insertion of an elevator to disimpact the fracture. This also helps to correct inclination/torsion and to restore a normal relationship of the medial fracture surface. The proximal fragment should be reduced anatomically to the shaft.
The actual process of reduction is done with image intensifier control.
Threaded pins or K-wires may be inserted into the proximal fragment and used as joy sticks for fracture reduction. However, this technique may be less effective in osteoporotic bone.
The reduction of the humeral head is temporarily secured using 2 to 3 K-wires. Make sure to place the K-wires such that they will not interfere with the later screw positions.
Confirm the reduction by image intensification in two planes.
Attention should be paid on the correct alignment of the proximal humerus in all planes. Particularly varus malposition has to be corrected. The medial “calcar” region should be well opposed.
A slight impaction can be tolerated in the elderly, and it may increase stability.
3 Fixation topenlarge
We illustrate the use of 3.5 mm cannulated screws. A larger diameter screw may be preferred for larger bone fragments, particularly in the surgical neck region. Since interfragmentary compression is desired, use a lag screw technique, with partially threaded screws inserted so screw threads do not cross the fracture line.
Guide wire insertion
At least two screws should be inserted to fix the fracture. Therefore, insert guide wires at the foreseen cannulated screw positions. Make stab incisions and use blunt dissections to spread the muscles. Check the position of the guide wires by image intensification.
Note: axillary nerve
Beware the axillary nerve and the bicipital tendon.
Cannulated screw insertion
Insert partially threaded cannulated screws of correct length over the guide wires. The screw must not perforate the articular cartilage. Use washers only in osteoporotic bone.
Check of osteosynthesis
Using image intensification, carefully check for correct reduction and fixation (including proper implant position and length) at various arm positions. Ensure that screw tips are not intraarticular.
After confirming reduction and fixation, remove any guide and K-wires. Close wounds as needed.