Ultrasound-guided thread versus ultrasound-guided needle release of the A1 pulley: a cadaveric study

Abstract

Purpose: To assess and compare two ultrasound-guided, minimally invasive procedures to release the A1-pulley (needle release and thread release) regarding efficacy and safety in an anatomical specimen model.

Materials and methods: Twenty-one ultrasound-guided needle releases and 20 ultrasound-guided thread releases were performed on digits of Thiel-embalmed anatomical specimens. A scoring system was developed to assess ultrasound visibility, intervention outcome (incomplete, almost complete, or full transection of the A1 pulley), and injury to adjacent structures (neurovascular structures, tendons, A2 pulley). Statistical analysis was performed to compare the score of the two groups (group 1: needle release,group 2: thread release). A P-value of ≤ 0.05 was considered significant.

Results: Needle release was completely successful in 15 cases (71.5%), almost complete release was achieved in four cases (19%), and incomplete transection occurred in two cases (9.5%). Thread release was completely successful in 17 cases (85%), and almost complete transection was observed in the remaining three cases (15%). In both procedures no neurovascular structures were harmed. Slight injury of flexor tendons occurred in two cases (9.5%) in needle release and in five cases (25%) in thread release. There were no significant statistical differences between the groups regarding ultrasound visibility, intervention safety and outcome, (P > 0.05).

Conclusion: Ultrasound-guided needle release and ultrasound-guided thread release have similar success of release, both being effective and safe techniques for the release of the A1 pulley.

Keywords: Cadavers; Decompression; Fingers; Ligaments; Ultrasonography.

Fig. 1

Schematic drawing of the NR (edited with Adobe Photoshop),the needle was inserted distal to the A1P (a) and used as a knife (b) until complete transection was achieved (c)

Fig. 2

HRUS images during NR in the short axis (a,b) and in the long axis (c,d),the needle is in its final position and ready to transect the A1 pulley (image edited with Microsoft PowerPoint) | Blue: flexor tendo,green: A1 pulley,white: needle,PP: proximal phalanx,MCP: metacarpal bone

Fig. 3

Schematic drawing of the TR (edited with Adobe Photoshop),the spinal needle is inserted distally and beneath the A1P (a),the thread is forwarded through the needle (b),the needle is inserted through the same skin incisions, but this time superficial to the A1P (c),the loop is created by reinsertion of the thread (d),the thread is uses as a saw to transect the A1P (e, f)

Fig. 4

HRUS images during TR in the short axis (a,b) and in the long axis (c,d),the thread is already placed in its final position ready to transect the A1 pulley (image edited with Microsoft PowerPoint) | Blue: flexor tendon,green: A1 pulley,white: thread loop,PP: proximal phalanx,MCP: metacarpal bone

Fig. 5

Anatomic dissections of two fully transected A1 pulleys (image edited with Microsoft PowerPoint),The flexor tendon of the finger in the top of the image shows slight irritations due to TR (notice the purple stain highlighting the thread pathway), whereas the flexor tendon of the finger in the bottom of the image shows no sign of damage | White arrowheads: cutting edges after release of the A1P