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

Clavicle 15.3 C2 Displaced lateral, CC ruptured, intra articular - Hook plate

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Glossary

1 Introduction top

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Hook plate fixation is indicated when there is insufficient bone in the distal clavicular fragment for adequate fixation with a conventional or distal clavicle plate.

This is typically the case with an intra-articular fracture. Hook plate fixation is an attractive alternative when dealing with fixation of small intra-articular fracture fragments. 

One drawback of hook plate fixation is that, following solid healing of the fracture, plate removal is generally required to optimize shoulder range of motion and eliminate residual discomfort from the hardware.

2 Verification of necessity of hook plate use top

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Following reflection of the deltoid the distal clavicle fracture site is identified and cleared of any hematoma or debris.

Typically, a displaced intra-articular fracture will result in disruption of part of or the entire acromioclavicular joint capsule and therefore the joint is usually readily apparent.

3 Direct reduction and fixation top

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Reduction

Reduction can be performed with several different methods, depending on fracture configuration and surgeon’s preference.
Make certain that downward displacement of the arm is corrected.

Conventional direct reduction can be performed using fracture clamps while applying downward and anterior pressure on the shaft and a lifting and superior force on the distal fragment and attached shoulder girdle.

Alternatively a ball spiked pusher may be utilized to align the fragments. 


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Temporary fixation

Following accurate reduction temporary fixation with a K-wire directed from anterior to posterior can be performed.


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Alternatively (and preferentially) if fracture configuration permits, a lag screw can be placed at this point.


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Incision for hook placement

A small incision is made at the posterior aspect of the acromioclavicular joint to allow sub-acromial placement of the hook.


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Plate selection

The trial hook plates are used to select the correct length of plate (to allow a minimum of 3 screws in the shaft) and to determine the correct depth of the hook.


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Plate application

At this point, the definitive hook plate is applied to the fracture.

Correct placement of the hook portion posteriorly under the acromion aids in reduction and avoids rotator cuff impingement.

The hook portion of the plate resists downward and medial translation of the arm through its tip position under the acromion.


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The hook plate is secured to the shaft fragment with cortical and cancellous screws (if possible) in the articular fragment to augment fixation.

Locking screws may be used if bone quality is poor.

K-wire is then removed.

4 Indirect reduction and fixation top

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The hook plate is a powerful tool that can be used to provide an indirect reduction of a distal clavicle fracture.

This indirect reduction technique is useful for comminuted fractures or fractures with very small distal fragments in which conventional reduction and fixation is difficult.


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Plate selection

A small incision is made at the posterior aspect of the acromioclavicular joint to allow sub-acromial placement of the hook. The hook portion of the trial hook plate trial is placed in the subacromial space at the posterior aspect of the joint, and the shaft portion of the trial hook plate is then used to lever the clavicle into place.


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At this point a trial and error method with the three different trial hook plate depths is used to determine the optimal hook depth for accurate reduction. Typically, the short four-hole hook plate will be adequate for most acromioclavicular joint dislocations.


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Pitfall: A too great hook depth will result in under-reduction, or residual superior displacement of the shaft fragment.


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Pitfall: It is important not to over-reduce the clavicle. This is the most common technical error and occurs when the hook depth chosen is too small which leads to inferior displacement of the shaft fragment. This results in an excessive pressure exerted on the acromion by the hook portion of the plate: acromial erosion or fracture can occur.


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Case: Over reduction

This is an example of an intra-articular distal clavicle fracture with significant displacement. 

Note the increased coracoclavicular distance.


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Following hook plate fixation, over reduction of the clavicle is demonstrated with a decrease of the coracoclavicular distance compared to the normal side. This puts severe pressure on the acromion from the tip of the hook plate as can be seen in this postoperative radiograph.


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Subsequent erosion of the hook through the acromion can occur as demonstrated in this illustration: acromial fracture can also occur. When hook plate mechanical failure occurs, over reduction is the most common contributing mechanism.


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Avoidance of over-reduction

There are a number of intraoperative maneuvers that will help avoid over-reduction. These include:

  1. Selecting a hook depth that is appropriate for the individual case
  2. It may be necessary to contour the shaft or hook portion of the plate with the hand held bending irons to optimize plate placement, as anatomy in this area may be quite variable. Care should be taken not to bend he plate or hook repeatedly as this might lead to material failure
  3. Excessive downward pressure on the clavicle should be avoided as this often results in over-reduction
  4. A superior bony prominence of the distal clavicle may be resected to provide a flat superior surface for plate placement: this will prevent over-reduction of the clavicle
  5. In cases where reduction is uncertain, intraoperative imaging with a trial in place will clarify the degree of clavicular reduction and can aid in correction of  any over-reduction

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Hook placement

At this point, the definitive hook plate is applied to the fracture.

Correct placement of the hook portion posteriorly under the acromion aids in reduction and avoids rotator cuff impingement.

The hook portion of the plate resists downward displacement of the arm through its position under the acromion.


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Reduction and plate application

To avoid excessive stress on any screw insert first the screw closest to the fracture and tighten until appropriate resistance is felt. This may leave the plate proud but…


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…sequential insertion of the following screws should approximate it to the shaft fragment and result in accurate fracture reduction. Note this can be done only if regular screws are used. Locking screws are contraindicated for such a maneuver.


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If feasible, the coracoclavicular ligaments can be repaired with sutures.

Alternative techniques for ligament repair can be found here:

5 Check of osteosynthesis top

At the conclusion of fixation the fracture site, plate, and screws are carefully checked to ascertain accurate reduction, correct plate placement, and avoidance of any intra-articular screw placement. If any doubt remains regarding these findings, and intraoperative radiograph should be taken for confirmation.

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