There are four types of scapular dyskinesis according to Kliber classification (Fig.7):
- Type I - inferiormedial scapular border prominence: This type is most commonly found in patients with rotator cuff dysfunction.
- Type II - medial border prominence: it is caused by weakness of stabilizing muscles
- Type III - superiormedial border prominence: it is often associated with impingement and rotator cuff injury.
- Type IV - symmetric scapulohumeral.
The term SICK scapula is used to describe the pathological state of the scapula.
It is characterised by:
- Scapula malposition consisting of forward tilting and protraction
- Inferior medial border prominence
- Coracoid pain and malposition
- Kinesis abnormalities of the scapula
Additionally,
scapular winging is one of the manifestations of scapular dyskinesis that leads to limited functional activity in the upper extremity.
This debilitating condition could be due to several causes.
The most common cause is the injury of long thoracic nerve resulting paralysis and dystrophy of serratus anterior muscle attributed to traumatic,
iatrogenic or idiopathic processes (Fig.8-10)
Fig. 8: Winged scapula due to long thoracic nerve palsy. The long thoracic nerve passes between the clavicle and first rib and then down along the lateral chest vall giving innervation to serratus anterior muscle.
References: Ryan M. Martin and David E. Fish Scapular winging: anatomical review, diagnosis, and treatments Curr Rev Musculoskelet Med. 2008 Mar; 1(1): 1–11
MR features are denervation changes in the serratus anterior muscle.
In the very early stage muscle signal might be normal.
Increased T2 signal is the earliest change.
Fast saturated T2 or STIR sequences are very useful for this stage.
Chronic changes are characterized by muscle atrophy and fatty infiltration with increased signal in T1 images (Fig.11-13)
Fig. 12: Axial STIR image reveals high intensity of the serratus anterior muscle. This feature is indicative of early denervation changes.
References: Courtesy of Dr. Beltrán. Department of Radiology, Maimonides Medical Center. Brooklyn
Other etiologies could be viral illness,
spinal accessory nerve paralysis,
fascioscapulohumeral dystrophy,
obstetrical brachial plexus palsy,
Greenstick scapula fracture during childhood,
exostosis or deltoid contracture.
The diagnosis of scapular dyskinesia and its subsequent entities is typically made by evaluation of clinical presentation,
patient history,
static and dynamic evaluations and electromyography studies.
Conventional MR imaging is not the principal diagnostic technique,
but it can provide additional information about pathologies,
problems and impairments that may result from abnormal scapular control and motion.
Those pathologies are (Fig.
14-15):
- Shoulder impingement syndrome
- Bicipital or rotator cuff tendinopathy
- Glenohumeral instability
- Rotator cuff tears
- Adhesive Capsulitis
- S.L.A.P.
lesion
- Hill-Sach Lesion
- Bankart Lesion