Figure 1 HJ needle (hybrid-J shield needle). A is the appearance of stylet and cannula with magnified view of blunt and sharp stylets, the white circle shows the blunt-tip stylet used for passing the needle over the tendon surface, and the black circle shows the sharp-tip stylet used for skin penetration; B is the appearance of stylet and outer cannula with magnified view of cannula, the white circle shows the entrance of cannula into which the stylet can be inserted with the suture

Figure 2 Process of modified ultrasound-guided curved-needle loop tendon sheath release. A is sharp stylet punctures the skin proximal to the release zone; B shows that blunt stylet is introduced through the same skin incision; C shows that under ultrasound guidance the blunt stylet is brought beneath the tendon sheath, the sharp stylet then punctures the skin distal to the release zone; D shows that blunt stylet is brought out through the distal skin incision; E shows cannula is mounted over the blunt stylet; F shows that under the guidance of blunt stylet, the cannula is passing from distal to proximal incisionwith suture through the trocar; G shows that the blunt stylet is passing above the tendon sheath under ultrasound guidance and the cannula is used to complete the procedure by putting the suture into the entrance of cannula; H shows that the loop surrounding the tendon sheath is completed, pulling the loop back and forth to cut the tendon sheath; I shows that the tendon sheath release is completed

Figure 3 Ultrasound anatomy of the metacarpophalangeal joint. A is proximal metacarpophalangeal joint, showing clearly the joint structure; B shows needle appearance under ultrasound view (white arrow)Note: MC-metacarpal；FT-flexor tendon；AP-A1 pulley

Figure 4 Threading process beneath the tendon sheath at the proximal metacarpophalangeal joint of the right fifth finger. A is sharp stylet puncturing the skin proximally; B shows that blunt stylet is brought under ultrasound guidance through the puncture site into the subsheath space, white arrow pointing at stylet position; C shows that cannula is inserted distally and coupled to the blunt stylet; D is ultrasound image showing the cannula and blunt stylet passing beneath the tendon sheath (white arrow); E shows that subsheath threading is completed. F shows that ultrasound confirms the suture (white arrow) lies beneath the tendon sheathNote: MC-metacarpal；FT-flexor tendon；AP-A1 pulley

Figure 5 Ultrasound images of threading process above the tendon sheath at the proximal metacarpophalangeal joint of the right fifth finger. A is blunt stylet inserting above the tendon sheath; B shows that cannula is brought over the blunt stylet; C is longitudinal view and D is transverse view of metacarpophalangeal joint under ultrasound, showing the stylet (yellow arrow) passing above the tendon sheath; white arrow showing the suture; E shows ultrasound confirming that the suture loop (white arrow) has successfully encircled the tendon sheathNote: FT-flexor tendon；AP-A1 pulley

Figure 6 Confirmation of tendon sheath release in the right fifth finger metacarpophalangeal joint using the cannula with ultrasound images. A~B is longitudinal ultrasound view, showing the cannula (white arrows) moving freely in the tendon sheath; C~D is transverse ultrasound view, showing the cannula (white arrows) moving freely in the tendon sheath, confirming complete release of the tendon sheathNote: FT-flexor tendon