Intersection syndrome is a friction / overuse tenosynovitis affecting the crossover point of the 1st and 2nd extensor compartments on the dorsum of the distal, radial aspect of the forearm.
It is an often confused diagnosis because the palpable lump and pain is more proximal to the expected site in De Quervain's tenosynovitis. This makes it an important differential diagnostic consideration when carrying out a wrist ultrasound.
The condition is best appreciated in the transverse plane by sweeping a high resolution linear probe back and forth across the intersection site. It is always advised that comparison is made with the asymptomatic side.
Signs of intersection syndrome on ultrasound are:
- thickening of either or both of the 1st/2nd extensor tendon compartments (tendinitis)
- thickening of the surrounding tendon sheaths with oedema (tenosynovitis)
- hypervascularity on power Doppler assessment (hyperaemia)
Ultrasound can be effectively used in the diagnosis of intersection syndrome.
Ultrasound guided injection of steroid / local anaesthetic into the inflamed tendon sheaths at the level of the intersection provides effective relief for this condition. Wrist splinting is recommended after injection, followed by specialist physiotherapy.