Anatomy
The clavicle (clavicle) forms a joint with the sternum and the upper bony prominence of the shoulder blade (acromion). The joint between the clavicle and acromion (AC joint) is reinforced with several ligaments (acromioclavicular ligaments and coracoclavicular ligaments).
The joint between shoulder blade and collarbone
A. Clavicula (Collarbone)
B. Lig. transversum scapulae
C. Scapula (Shulder blade)
D. Acromion
E. Ligamentum acromioclaviculare
F. Ligamentum coraco-acromiale
G. Lig. Trapezoideum (Lig. coracoclaviculare)
H. Lig. conoideum (Lig. coracoclaviculare)
Cause
The ligaments between the upper bony prominence of the shoulder blade (acromion) and the collarbone can break if they are subjected to a violent load, such as falling on an extended arm/elbow or shoulder.
In mild cases, there is a sprain with stretching of the ligaments (distorsio, grade-1). In severe cases, there is a partial dislocation (subluxatio, grade-2) with rupture of some of the ligaments (the acromioclavicular ligaments) that hold the collarbone in place.
The collarbone can then move slightly in relation to the acromion. In the most severe cases, a total joint dislocation (grade 3) occurs with rupture of all ligaments (including the coracoclavicular ligaments) so that the collarbone no longer has contact with the acromion (luxation).
Symptoms
Pain at the outer part of the clavicle and with movement in the shoulder joint (grade-1 and grade-2). In total joint dislocation (grade-3), the clavicle is so loose that it can prominence with visible misalignment (‘floating shoulder’) and often accompanied by audible clicks, nocturnal pain and pain on loading the joint.
Examination
In total joint dislocations (grade-3), the diagnosis is easily made by general clinical examination. In grade-1 and grade-2 lesions, there is distinct tenderness when pressure is applied to the AC joint. If there is uncertainty as to whether the pain is coming from the AC joint, a local anaesthetic can be injected into the AC joint (diagnostic blockade).
If the athlete is pain-free for the duration of the local anaesthetic, it is certain that the pain is originating from the AC joint. The degree of looseness of the joint can be assessed by ultrasound scan (or X-ray) with simultaneous pulling in the longitudinal direction of the arm while the joint is loaded.
See the ultrasound scan of the AC joint
For grade 3 lesions, an X-ray is recommended to rule out fractures and possibly to assess looseness (X-ray).
Treatment
The treatment of grade 1 and grade 2 injuries primarily involves relief from the pain-inducing activities and rehabilitation of the muscles around the shoulder within the pain threshold.
It’s not uncommon for athletes with high overhead arm loading (throwers, weightlifters, racquetball) to experience long-term discomfort that can last for many months.
For grade 3 injuries, contact sports are not recommended for 3 months, after which most people are pain-free, although the joint damage is often permanently visible. If pain persists or shoulder function is compromised after 3-6 months, surgery may be considered (de Groot C, et al. 2023).
Complications
80% become symptom-free within 3-6 months and can return to the same level of activity (Cleary BP, et al. 2023).
After grade 1 and grade 2 injuries in the AC joint, long-term inflammation can occur in the joint. This can be treated with adrenal cortex hormone. In case of insufficient effect and significant persistent discomfort due to trauma-induced osteoarthritis in the AC joint, the outer part of the clavicle can be surgically removed.
