Executive Editor: Joseph Schatzker General Editor: Jonas Andermahr, Michael McKee, Diane Nam

Scapula 14.2 Body and processes, acromion - lag screw fixation

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Glossary

1 Introduction top

Introduction enlarge

The majority of isolated acromial factures can be managed non-operatively.

However, typically most acromial fractures are associated with more complex fractures of the scapula, and/or clavicle, and may also involve the suspensory ligament complex.

Any disruption of the ligament complex is treated as described in the section of LSSS.

Most of the acromion is cancellous bone and provided poor fixation for screws.


Lag Screw enlarge

Lag Screw

Lag screws are used to achieve compression and can be used alon or in combination.

The following screws are useful:

  • Conventional 3.5 screws
  • Cancellous 4.0 screws (partial or fully threaded)
  • Cannulated cortical 3.5 screws

2 Approach top

Approach enlarge

For simple fractures of the acromion, a superior approach is recommended. For complex injuries a modified deltopectoral approach is preferred.

For associated complex injuries requiring an anterior approach, an extended delta pectoral approach may be used (eg. coracoid, glenoid, proximal humerus fractures).

3 Reduction and fixation top

Reduction enlarge

Reduction

Reduction is best achieved using a reduction clamp.


Guide wire insertion/Temporary fixation enlarge

Guide wire insertion/Temporary fixation

At least two screws should be inserted to fix the fracture. These screws should be positioned parallel to each other to optimize the compression.

Insert the first guide wire at the desired cannulated screw positions. The second guide wire is inserted with the use of the parallel drill guide. The positions of the wires are checked with image intensifier to make certain that they are in bone and have not exited subacromially and entered the rotator cuff, the supraspinous fossa or the shoulder joint.


Cannulated screw insertion enlarge

Cannulated screw insertion

Use the 3.5 mm fully treaded cannulated screws of correct length and insert them as lag screws over their respective guide wires. This requires that you predrill the acromion to create two gliding holes before you insert the screws. Washers may be used under the screw head in osteoporotic bone.

Remove the guide wires.


enlarge

Since the superior cortex of the acromion is under tension, one can supplement the fixation by the insertion of wire through the two cannulated screws. If these are then crossed, and tied under tension they act as tension bands. 

A loop is made in the middle of the wire passing from the tip of screw A to the head of screw B to allow for later symmetrical tightening.


enlarge

Check the reduction and fixation with an image intensifier.

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