Compiled by Dr S Selvaganesh Hand Surgery Fellow KTPH Triceps to axillary nerve transfer is used in partial plexus injuries where the C5/6 component is damaged and the C7/8 and T1 are intact. The typical indication is in the C5 or C5/6 avulsion injury but it may also be used in cases of C5/6 rupture where presentation is delayed, grafting of the upper trunk has not been successful or in continuity lesions of the upper trunk that failed to reinnervate. It may also be used to salvage the axillary nerve rupture at the quadrilateral space associated with high energy shoulder dislocation or the rare non-recovering isolated lesion in continuity of the axillary nerve following a low energy shoulder dislocation.

1. Instructions for Somsak
Nerve transfer
N to long head of triceps to
anterior division of the
axillary nerve
Compiled by Dr S Selvaganesh
Hand Surgery Fellow KTPH

2. Cadaveric dissection
First Nerve transfer workshop,
KTPH, Singapore
Practical 4

7. Incision
• Specimen in prone position
• Make a 10cm longitudinal curvilinear incision on the posterior arm.
• From the level of the quadrilateral space following the posterior order
of deltoid and continuing distally along the midpoint of triceps.

11. Superficial dissection
• Lift up the skin flaps - look for the upper lateral cutaneous nerve of
the arm (ULCNA) – will guide to the posterior division
• This branch can be confirmed by gentle traction, which dimples the
skin

16. Deep dissection
• Split the fascia at the point where the ULCNA pierces - trace this back
to the posterior division of the axillary nerve - loop
• Follow the posterior division deep until the anterior division is
identified - trace distally to the deltoid muscle
• (The anatomy in the space may be difficult to define and axillary
vessels may cross the nerve branches)

17. Upper Lateral Cutaneous
Nerve of Arm

24. Deep dissection
• If ULCNA unidentified, identify the anterior division
• Anterior division – passes deep to the posterior border of the deltoid
muscle - 5cm distal to the postero-lateral corner of the acromion
• There are usually two main branches and lifting the deltoid using a
retractor placed more proximally facilitates this exposure without
risking damage to the nerve branches
• Use a rubber surgical loop to tag the anterior and posterior divisions
of the axillary nerve

28. Posterior branch

29. Deep dissection – between long & lateral
heads of triceps
• Identify a fat streak on the triceps
• Develop the plane between the long and lateral heads of triceps -
gentle finger dissection
• Carefully place a self-retaining retractor in this interval – avoid
damage to the triceps branches
• The white tendon of latissimus dorsi – between quadranqular (axillary
nerve) & triangular spaces (RN & Branches)
• Tag each nerve with surgical loops

37. Recipient Division
• Divide the axillary nerve as proximally as possible – gentle loop
surgical traction
• Separation of the anterior and posterior divisions by endoneurolysis
• (Avoid injury to the axillary artery or vein branches in the
quadrilateral space)
• Select a donor muscle branch from triceps long head (Somsak) or
medial head branch

41. Donor Division
• The posterior cutaneous nerve of the arm lies on top of the main
radial nerve – can confuse
• Trace the branch distally to see where the motor branch enters the
muscle & confirm with the faculty
• Divide donor distally – external neurolysis using gentle surgical loop
retraction

44. Coaptation
• Coapt using 9’0 nylon 2 - 3 sutures - use microscope
• (May be supported with Tisseel fibrin glue)
• Ensure tension free and remain tension free throughout a full passive
range of shoulder motion

46. Thank you