Micro-anatomical Study Of Thenar Flap

Objective:To provide a clear anatomical basis for the design and excision of the thenar skin flap in clinical practice,through microdissection targeting this area.The venous return,innervation and blood supply sources would be clarified in addition the skin in the thenar area is reasonably zoned according to different blood supply sources.Methods:Twenty fresh adult hand specimens on 20 sides,11 on the left and 9 on the right,with red latex perfused vessels.The skin and subcutaneous tissues of the thenar area were dissected under the surgical microscope to observe the venous return vessels,sensory nerves,and arterial sources of blood supply to the skin of the thenar area.The area was rationally subdivided according to the source of blood supply.Results:1.Microscopic anatomy of the perforating vessels of the skin in the thenar area:seven sources of perforating vessels of the skin in the thenar area:(i)superficial palmar branch of the radial artery:the main stem of the radial artery emanates from the radial artery and travels towards the ulnar side of the thenar,sending out a perforating branch to feed the proximal skin of the ulnar side;(ii)superficial palmar arch:the superficial palmar branch of the radial artery penetrates the thenar muscle to form a superficial palmar arch and sends out a cutaneous branch to feed the middle skin of the ulnar side;(iii)return branch of the innominate artery of the thumb:the origin of the intrinsic radial metacarpal artery of the thumb and its return branch give rise to a cutaneous branch to feed the distal ulnar skin;(iv)middle pisiform artery:the middle pisiform artery arises from the radial artery near the navicular tuberosity and emerges superficially from the medial border of the thumb’s longus adductor muscle,sending a cutaneous branch to feed the proximal radial skin;(v)dorsal radial artery of the first metacarpal:this artery arises from the radial artery in the nasal fossa and travels distally along the dorsal radial side of the first metacarpal,sending a cutaneous branch to feed the mid-radial skin;(vi)penetrating neck branch of the radial metacarpal of the first metacarpal:this artery arises from the main thumb artery and penetrates deeply;(vii)musculocutaneous or thenar perforations:this artery originates from the main thumb artery or from the superficial palmar branch of the radial artery and gives off a musculocutaneous or thenar perforation to feed the skin of the middle thenar area.There is a very rich anastomosis between the vessels of the various penetrations of the skin in the thenar area.2.Cutaneous innervation of the thenar area:five sources of cutaneous sensory nerves in the area:radial-the superficial branch of the radial nerve,the lateral cutaneous nerve of the forearm;ulnar-the palmar cutaneous branch of the median nerve,the interosseous cutaneous branch of the median nerve,and the radial intrinsic nerve branch of the thumb.In addition,these areas of sensory nerve innervation from these five sources overlap each other.3.The venous reflux pattern in the skin of the thenar area:(ⅰ)from the middle to the sides and proximally,with the radial side returning to the cephalic vein via the superficial vein at the dorsal palmar junction,and the ulnar side communicating with the vein in the middle part of the forearm palmar side via the superficial palmar vein in the middle of the palm;(ⅱ)1-2 companion veins in each of the penetrating vessels,returning to the deep veins.Conclusion:1.The skin of the thenar area has been subdivided into seven zones according to the different blood supply source:(ⅰ)proximal radial,(ⅱ)middle radial,(ⅲ)distal radial,(ⅳ)middle,(ⅴ)proximal ulnar,(ⅵ)middle ulnar,and(ⅶ)distal ulnar.2.There is a rich anastomosis between the source vessels of each zone of the skin of the thenar area,which can also feed the skin of other zones in addition to their respective skin.3.The sensory nerves of the skin in the thenar area are not in one-to-one correspondence with the source vessels of each area.