Open reduction and internal fixation of acromion fracture with os acromiale using cannnulated screws and box suture
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I use the following technique for fixation of displaced acromion fractures that are too small to accommodate fixation using anatomic contoured plates. My first preference would be for plate fixation if the fracture pattern allows, as is also used for surgical management of a symptomatic os acromiale(where the os occurs proximal to the pre-acromion).
Numerous surgical techniques for management of acromion fractures have been described, which are rare injuries. The main considerations include the location, orientation and size of the fracture fragments, the biomechanical stability of the construct proposed and the amount of associated soft tissue and deltoid stripping. Methods include K-wire fixation, tension band fixation, cannulated screw fixation as well as using pre-contoured plates including lateral end clavicle plates as well as acromion plates.
In the case described cannulated screws were the only viable option due to the size of the fragments. However to improve the mechanical stability this fixation is augmented with a box suture through the screws to improve the ultimate failure load of the construct, as described by Speigl et al. Fibrewire rather steel wire is used as the suture material because it is less likely to cause soft tissue irritation. Shiu et al have shown there is no significant difference in ultimate load to failure between using stainless steel wire and polyethylene suture.
K-wire fixation is not recommended due the the risk of early failure and risk of K-wire migration. This is due different planes of action of the deltoid fibres that the construct is unable to counteract.
Traumatic acromion fractures
In trauma, fractures involving the scapula usually result from high energy injuries. They commonly involve the scapula body and spine (50%). Associated injuries involving the shoulder girdle have also been commonly reported, including clavicle fractures, vascular injuries, plexus injuries, cuff tear and glenohumeral joint dislocations as well as rib fractures, pulmonary contusions/pneuomothoraces and head and spine injuries. Scapula fractures have a mortality rate of 2-5%.
Acromion fractures account for 8% of all scapula fractures. They are rare with an incidence of less than 1% of all fractures. As a result, the indications for surgery are not well established. However, concerns with displaced fractures can result in painful non-union and can compromise shoulder function.
The method of fixation is usually determined by the fracture pattern, with particular reference to the location of the fracture.
When classifying scapula fractures, they can be subdivided into fractures of the glenoid, acromion and coracoid. The AO classification subdivides scapula fractures into fractures of the process, body or glenoid. Acromion fractures are described as a fracture of the acromion process (14A2), but does not subdivide them into fracture patterns.
More commonly used classifications include those described by Kuhn et al, Ogawa and Naniwa and Goss et al.
Kuhn et al. proposed a classification system of acromion fractures and divided them in:
Type I – Minimally displaced fractures
IA – avulsion type fracture
IB – minimally displaced fracture associated with direct trauma
Type II – fracture with displacement superiorly, anteriorly or laterally
Type III – fracture with displacement causing a reduction in subacromial space
Kuhn recommended that type III acromial fractures should undergo surgical fixation.
J Shoulder Elbow Surg. 2015 Apr;24(4):520-6.
J Shoulder Elbow Surg. 2016 Dec;25(12):2034-2039.
Author:Mr Sam Chan, FRCS Tr & Orth.
Institution: The Queen Elizabeth Hospital, Birmingham, UK.