1 Principles top
Minimally invasive plate osteosynthesis can be reasonably considered for non-impacted surgical neck fractures.
A satisfactory reduction should be stabilized with K-wires before the plate is applied. Comminuted metaphyseal fractures may not be stable with K-wires. Using the plate as a reduction aid, perhaps adding a distractor as well, may be more effective.
Unless a satisfactory closed or minimally open reduction can be achieved, an open reduction should be employed.
Choose the approach best suited for planned reduction maneuvers or plate position.
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 area to determine the location of the nerve, and by avoiding maneuvers that stretch the nerve during reduction and fixation. Remember the course of the nerve when placing K-wires.
Tension band sutures in addition to plate and screws
Sutures placed through the insertions of each rotator cuff tendon increase stability, and should be used as well as the plate 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.
Angular stable versus standard plates
This procedure describes proximal humeral fracture fixation with an angular stable plate (A). Sometimes, these implants are not available. Standard plates provide an alternative option, for example the modified cloverleaf plate (B). Presently, the specific indications, advantages, and disadvantages of angular stable and standard plates are being clarified. There is some evidence that angular stable plate provide better outcomes. In addition to type and technique of fixation, the quality of reduction, the soft-tissue handling, and the characteristics of the injury and patient significantly influence the results. There is no evidence that the use of angular stable plates will overcome these other factors.
2 Reduction and preliminary fixation topenlarge
Since the fracture is not exposed, the surgeon should be skilled at closed reduction maneuvers before considering minimally invasive plate osteosynthesis MIPO.
Traction applied to the limb helps to realign the proximal fragment as well as the distal.
Threaded pins or K-wires may be inserted into the proximal and distal fragments and used as joy sticks for fracture reduction. However, this technique may be less effective in osteoporotic bone.
Pearl: use of retractors
Use of blunt, curved Hohmann retractors underneath the deltoid muscle can be helpful to expose the humeral head.
Similarly, a so-called delta retractor may improve deltoid retraction.
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 plate position.
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.
3 Plate position topenlarge
Correct plate position
The correct plate position is:
- about 5-8 mm distal to the top of the greater tuberosity
- aligned properly along the axis of the humeral shaft
- slightly posterior to the bicipital grove (2-4 mm)
Pitfall 1: plate too close to the bicipital groove
The bicipital tendon and the ascending branch of the anterior humeral circumflex artery are at risk if the plate is positioned too close to the bicipital groove. (The illustration shows the plate in correct position, posterior to the bicipital groove).
Pitfall 2: plate too proximal
A plate positioned too proximal carries two risks:
- The plate can impinge the acromion
- The most proximal screws might penetrate or fail to securely engage the humeral head
4 Plate fixation topenlarge
Positioning wires (for plate location)
To ensure appropriate plate position, somewhat obscured by a small incision, it helps to place temporary K-wires that can be used for radiographically controlled guidance.
Insert 2 positioning K-wires, one at the lateral border the bicipital groove and the other at the tip of the greater tuberosity.
The anterior positioning K-wire sets the location for the anterior edge of the plate, 2-4 mm lateral to the bicipital groove.
The proximal positioning K-wire determines the proximal edge of the plate, 5-8 mm distal to the tip of the greater tuberosity.
Identify the axillary nerve by palpating on the undersurface of the deltoid muscle. This helps protect it during plate insertion.
Insert the plate, assembled on an aiming device, under the deltoid muscle, and slide it distally under the deltoid and along the humerus. Always keep the plate in contact with bone.
Pearl: suturing the deltoid muscle To prevent extending the deltoid muscle split and increasing risk of axillary nerve injury, place a suture at the distal end of the split.
Attach plate to humerus
Position the plate in the planned and marked location on the proximal humerus. Fix it temporarily to the bone with K-wires. Proximally, two wires are placed through specific holes in the aiming device. Distally, use a percutaneously placed K-wire sleeve.
Confirm correct plate position with x-ray.
Fix plate to the humeral head
Use the aiming device with drill sleeves to drill holes for the proximal screws. Do not drill through the subchondral bone and into the shoulder joint.
Follow the manufacturers technique guide.
Avoiding intraarticular screw placement
Screws that penetrate the humeral head may significantly damage the glenoid cartilage. Primary penetration occurs when the screws are initially placed. Secondary penetration is the result of subsequent fracture collapse. Drilling into the joint increases the risk of screws becoming intraarticular.
Two drilling techniques help to avoid drilling into the joint.
Pearl 1: “Woodpecker”-drilling technique (as illustrated)
In the woodpecker-drilling technique, advance the drill bit only for a short distance, then pull the drill back before advancing again. Keep repeating this procedure until subchondral bone contact can be felt. Take great care to avoid penetration of the humeral head.
Pearl 2: Drilling near cortex only
Particular in osteoporotic bone, one can drill only through the near cortex. Push the depth gauge through the remaining bone until subchondral resistance is felt.
Determine screw length
The intact subchondral bone should be felt with an appropriate depth gauge or blunt pin to ensure that the screw stays within the humeral head. The integrity of the subchondral bone can be confirmed by palpation or the sound of the instrument tapping against it. Typically, choose a screw slightly shorter than the measured length.
Insert a locking-head screw through the screw sleeve into the humeral head. The sleeve aims the screw correctly. Particularly in osteoporotic bone, a screw may not follow the hole that has been drilled.
Number of screws and location
Place a sufficient number of screws into the humeral head. The optimal number and location of screws has not been determined. Bone quality and fracture morphology should be considered. In osteoporotic bone a higher number of screws may be required.
Insert screws into humeral shaft
Insert two to three screws into the humeral shaft, below the danger zone, with aiming device and appropriate, percutaneously placed screw insertion sleeves.
The illustration shows the completed osteosynthesis.
Tension band sutures in addition to plate and screws
Supplementary rotator cuff tendon sutures provide additional stability. Varying the arm position helps to place them through such a small incision. The sutures should be inserted close to the bony insertion sites of subscapularis, supraspinatus, and infraspinatus tendons. They are tied to the plate to resist muscle forces and improve plate anchorage.