In 12 limbs, we noticed that the branch of the PL muscle was long enough to reach the PIN, distal to the branches to the supinator muscle, free of tension even with the movements of the forearm and elbow (Figs.
In PIN palsy, a bulging mass due to chronic proliferative synovitis or acute/subacute synovial effusion of the elbow joint may cause compression of the PIN against the fibrous edge of the supinator muscle. (8) Therefore, close monitorization of the inflammation and the clinical picture of RA patients is crucial so as to prevent complications like PIN palsy.
However, we have been able to visualise it by placing the ultrasound probe at the proximal part of the posterolateral compartment of the forearm, 5 to 7 cm away from the elbow, exactly at the point where the nerve plunges into supinator muscle (Figure 1d).
The first PTM branch of the median nerve had enough length to be transferred to the AIN in 23 (76%) limbs, while they could reach the radial nerve branches to the ECRL, ERCB and PIN distal to branches for the supinator muscle in all members.