AC joint capsule sprain and synovitis

Clinical information

Three weeks ago, the patient fell on his left shoulder during mountain-biking in the woods. The patient experienced an immediate pain. This pain increased over a few days to a continuous VAS 8, but has decreased since then to a VAS 4 when provoking the AC joint. Provoking occurs for example with palpation, or end range adduction or anteflexion movements. At inspection a swelling can be seen at the location of the AC-joint. Is it a soft tissue swelling? Or the result of a higher clavicular position potentially indicating a coracoclavicular ligament pathology?

Brief description

The transducer was placed longitudinally (long-axis) over the clavicula and acromion; the AC joint was visualized. Images were analyzed by using the SonoSkills pathology checklist.

• SHAPE: The AC joint capsule appears to be thickened, and more convex. The cortex of the bones (acromion and clavicula) is smooth and looks normal. The height difference between acromion/clavicula appears to be the same on the right (asymptomatic) side leading to the assumption that the left clavicula has not changed in position. This is corraborated by measuring the distance from the coracoid process to the clavicula: no difference in distance (of the coracoacromial ligaments) in a left/right comparison. The joint space appears not be be widened. 
• ECHOGENICITY: The AC joint capsule appears to be more hypoechoic due to swelling. The capsule shows signs of a proliferating capsule: more hyperechoic parts can be seen amidts the anechoic joint fluid. 
• CONTINUITY: the coracoclavicular ligaments could have been affected, but appear not affected, judging the position of the clavicula, the joint space width and the distance between coracoid process/clavicula, and the functional assessment. 
• DOPPLER: severe signs of neovascularization can be seen in the left AC capsule. 
• FUNCTIONAL: when performing a dynamic cross-arm manoeuvre (Petroons et al. 2007), no instability of the AC joint can be observed. 
• LEFT/RIGHT COMPARISON: has been done to double check the above mentioned findings. X-RAY: no ossal changes

Conclusion

Based on the ultrasound findings and SonoSkills pathology checklist analysis we conclude:

• Synovitis AC joint with severe neovascularization
• Most likely there is a sprain of the AC joint capsule
• No signs of tearing the coracoclavicular ligaments