There is thickening (up to 1.3 mm) of the extensor retinaculum involving abductor pollicis longus and extensor pollicis brevis tendons.
There is no vertical septum between two tendons of 1st extensor compartment. Both tendons are intact. There is local hypervascularity. There is fluid in tendon sheath proximal and distal to sheath thickening.
There are two slips of abductor pollicis longus tendon (a normal variant).