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Unilateral Superiomedial Avulsion Fracture of the  Scapula: A Case Report

Kevin Kulendra*, Jai Relwani**, Keith Borowsky***

*Orthopaedic SHO
**Orthopaedic SPR
***Consultant Orthopaedic Surgeon
Medway Maritime Hospital, UK

Address for Correspondence
Dr. Kevin Kulendra  
25 Buxton Drive, New Malden, Surrey, KT3 3UX 
Tel: 07737 352 954
Fax: 020 8395 0117


We present the case of a 36-year-old gentleman who suffered a scapular fracture following an unusual indirect injury. Scapular fractures may be indirect or direct, which may be high or low energy injuries. This paper comments on the unusual mechanism of injury leading to a scapular fracture, which was misdiagnosed in the Accident and Emergency department as a subluxation of the left acromioclavicular joint. The postulated mechanism of injury is an avulsion fracture, as a result of the action of serratus interior and levator scapulae.
Keywords: Scapula
; Fracture; Avulsion; Mechanism; Serratus Anterior; Levator Scapulae.

J.Orthopaedics 2007;4(2)e6

Case Report:

A 36 year old gentleman was standing on his haunches and slipped backwards, stretching out his left hand to prevent him falling. He felt a twist in his scapula region, but there was no actual impact. He heard something go and had pain in his shoulder following the incident. 

Fig.1 Initial fracture sustained at the 
superiomedial angle of scapula

He had a background history of epilepsy for which he was taking Sodium Valproate, but this was ruled out as a contributing factor to his current injury. He was a left hand dominant builder who was a smoker and lived with his brother. 

On examination there was diffuse fullness around the medial border of the scapula. In elevation, he had altered scapula thoracic rhythm; however he had a full range of active movement in both shoulders. He was extremely tender over the superior medial angle of the scapula and there was palpable crepitus in this area.  Radiographs of the left shoulder revealed a fracture of the superomedial
 angle of the left dominant scapula (Figure 1). He was advised to use a sling to ease his symptoms until his shoulder felt more comfortable. The radiographs were repeated 8 and 12 weeks later and the fracture was noted to be healing (Figure 2).

Fig.2 Healed scapular fracture 
12 weeks later

 He did not require any specialised physiotherapy regime, and regained full function at 12 weeks post injury. He remained asymptomatic at a 2 year follow up.

Discussion :

Scapular fractures are relatively rare, constituting only 1% of all fractures and 5% of those involving the shoulder, as the scapula is well protected by overlying muscles (2). Since the scapula does not support heavy loads, the functional repercussions are not serious unless the glenoid is involved. 

Among scapular fractures, those of the superior portion are rare and an avulsion fracture of the superomedial angle, as in this case has not been described with this mechanism of injury. Due to their rare nature, these types of fractures have not been included in recent proposed classification of scapular fractures (1,7). 

The most common mechanisms of scapular fractures are high-energy motor vehicle collisions and direct violent trauma (2, 7), often associated with other injuries. In this case however the most likely mechanism is avulsion in the absence of violent direct trauma. The anatomical location of the fracture in relation to muscular attachments supports this mechanism.           

Three indirect mechanisms of scapular fractures have been described. Uncoordinated muscle contracture due to electroconvulsive therapy, electric shock (2, 4, 5) and more rarely epileptic seizures (7) is one postulated mechanism. This particular patient was epileptic, but there was no history of fitting. Another mechanism is resisted muscle pull as a result of trauma or unusual exertion (4). Supporting evidence lies in the fact that this mechanism is thought to correlate with fractures of the superior border of the scapula (4). The final mechanism is avulsion of ligamentous attachment (4). This information suggests that it is important to consider scapular fractures in the differential diagnosis of shoulder pain depending on the mechanism of injury.

If we consider the anatomy of the muscular attachments of the scapula in relation to this injury, the serratus anterior and levator scapulae were the most likely culprits. Serratus anterior is attached to the anterior surface of the medial border of the scapula and extends to the medial potion of the superior border. It protracts the scapula holding it against the thoracic border as well as rotating the scapula. It has been suggested that avulsion fractures of the inferior border of the scapula are associated with serratus anterior (4). Serratus anterior avulsion fracture may also be associated with winging of the scapula due to loss of function (3, 4), which was not noted in this case. Levator scapulae is attached to the posterior surface of the superior part of the medial border of the scapular. It elevates the scapula and tilts its glenoid cavity inferiorly by rotating the scapula. We postulate that the fracture occurred due to a strong contraction of these two muscle groups acting on the superomedial angle of the scapula. Despite being an avulsion injury, the fracture fragment was only marginally displaced due to the superior fibres of the subscapularis, which extend just onto the thoracic aspect of the superomedial angle of the scapula. Similar avulsion fractures have been described involving the omohyoid muscle (2, 4, 9), however all these reports have included traumatic incidents in the history.  

This fracture was successfully treated conservatively as illustrated in the X-rays initially and 12 weeks later. Most scapular fractures may be successfully treated conservatively, however instances of non-union have been described (1, 3). These cases occurred with fractures of the spine and body of the scapula with the latter being partly due to ribs and muscle lodging between bone. However this case was free of complications such as non-union and snapping syndrome, which were also absent at a 2 year follow up. 

Reference : 

  1. Ada JR, Miller ME. Scapular Fractures: Analysis of 113 Cases. Clinical Orthopaedics and Related Research 1991; 269 174-80
  2. Arenas AJ, Pampliega T. An unusual kind of fracture. Acta Orthop Belg 1993; 59(4) 398-400
  3. Gupta R, Sher J, Williams G et al. Non-Union of the Scapular Body: A Case Report. J Bone and Joint Surg 1998; 80-A(3) 428-30
  4. Heyse-Moore GH, Stoker DJ. Avulsion fractures of the scapula. Skeletal Radiol 1982; 9(1) 27-32
  5. Kotak BP, Haddo O, Iqbal M, Chissell H. Bilateral scapular fractures after electrocution. J R Soc Med 2000; 93 143-4
  6. Marra G, Stover M. Glenoid and scapular body fractures. Current Opinion in Orthopaedics 1999; 10 283-8
  7. McAtee SJ. Low-energy scapular body fracture: a case report. Am J Orthop 1999; 28(8) 68-72
  8. Moore KL, Agur AMR. Essential Clinical Anatomy. Baltimore:Williams & Wilkins 1995
  9. Williamson DM, Wilson-MacDonald J. Bilateral avulsion fractures of the cranial the scapula. J Trauma 1988; 28(5) 713-4


This is a peer reviewed paper 

Please cite as :Kevin Kulendra: Unilateral Superiomedial Avulsion Fracture of the  Scapula - A Case Report

J.Orthopaedics 2007;4(2)e6





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