Anatomical Basis Of The Greater Thenar Flap And Its Clinical Application Study

BACKGROUNDHands are the unique working organs for human beings.None of the inventions created during the development of human civilization is not through the work of hands.Especially in twenty-first century,Human beings' demand for the functions of hands increases with the increased pressure for survival and the widely uses of computers.But with the rapid development of economics,the rate of mechanization getting higher,and safety education lags behind,thus hand injuries happen quite often.Among the hand injury cases,thumb injuries occur most commonly.Thumb takes 40%of hands' functions,thumb plays the roles of grasping,holding,niping and catching.If thumb soft tissue defect can't get high quality repairing treatment,the functions of hands will be affected.Improving the life quality of the patients with injured hands is not only necessary but also very urgent.Among the repairing methods for thumb soft tissue damages,the index finger dorsal island flap is poorly recovered in its sense,thus not good for repairing thumb soft tissue damages,the lateral digital island flap will cause more severe damages,and sacrifice one side of the finger's sensation ability,besides this method is easy to cause scar tissue contracture in palm of finger。The greater thenar skin is most similar with the thumb palmar skin in terms of color and texture, when it is used to repair the damages of thumb soft tissue,the cperation is easier to perform because the close distance between the donating and receiving section, which fits the local repairing principle of skin damage.The greater thenar skin is very important,it is easy to be destroyed if the design method is improper.How to balance the conflict of the two factors and design a reasonable and usable flap is worth of intensive research.Taking a panoramic view of the worldwide publications about the greater thenar flap,there is no elaborate anatomic report,there are many descriptions about the operation methods of the flap,utilization of nerves and vessels.For example, Chen Maosong et al reported the greater thenar flap pedicled with thumb radial-palmar digital artery to repair thumb soft tissue defect,they suggested that the proximal end of flap should not go beyond the middle part of the greater thenar,and the distal end of flap don't exceed the thumb palmar flexion crease,and its application was confined because it has not sense nerve.Liu Zhenhua et al consider the flap can be taken according to the area of soft tissue defect,the proximal end of flap can get to the wrist transverse crease,the distal end of flap can get to the thumb palmar flexion crease.Obvious differences can be seen from the above two opinions. In addition,Wang Youhua and Omokawa reported respectively they used the proximal greater thenar flap to repair the thumb pulp defect.They considered that the reverse island flap pedicled with the superficial palmar arch could be designed only when the typical superficial palmar arch existed,and palmar branch of median nerve might be carried,but this method will do severe damage to the skin of palm.When we anatomised cadaveric hand specimens and treated hand injuries,we found that the thumb radial-palmar digital artery sent several cutaneous branches toward upside and outside when it came out from the thenar muscles terminal to supply the distal skin of radial-dorsal greater thenar,so we could design a kind of great thenar flap to do less injuries to palmar skin.But so far there is no report about this kind of perforator artery,thus it is necessary to perform intensive research on the blood supply of great thenar skin,so as to standardize and summarize this kind of operation method,which is also the significance of this research project.OBJECTIVE1.Through anatomy study,to understand the anatomic characteristics of the blood supply in greater thenar skin,especially the origin,course,caliber,branches and anastomosis of the greater thenar vessels,and distribution of never branches,in order to provide anatomic basis for designing suitably greater thenar flap.2.To design the great thenar flap to repair the thumb soft tissue defect on the base of anatomy study,to observe its area and clinical effect,in order to introduce a new method to repair thumb soft tissue defect,to summarize operation adaptability and its advantage and disadvantage.METHODS1.The origin,course,caliber,branches and anastomosis of the greater thenar vessels were studied on 20 formaldehyde-fixed adult cadaveric hand specimens perfused with red gelatin in the artery.The course,anastomosis of blood vessels were observed on 2 casting specimens.The operation design was mimiced on 2 hand specimens.2.On the base of anatomy study,appropriate cases with thumb skin and soft tissue defect were treated by great thenar flaps.The clinical effect was understood after 6 to 24 months follow-up,including subjective opinion and objective opinion.RESULTSApplication anatomy: 1.According to the origin of the thumb radial-palmar digital artery,the blood vessel in greater thenar skin was divided into three models:â… .The superficial palmar branch(arch) model(25.0%):thumb radial-palmar digital artery just came from the superficial palmar branch(arch) of radial artery,Ia model was from the superficial palmar branch,Ib model was from the superficial palmar arch.â…¡.the thumb principal artery model(20.0%):thumb radial-palmar digital artery only came from the thumb principal artery.â…¢.the traffic model(55.0%):thumb radial-palmar digital artery came from two branches of the superficial palmar branch of radial artery and the thumb principal artery.2.According to the origin of the thumb radial-palmar digital artery,the blood vessel in greater thenar skin was divided into three models:â… .the superficial palmar branch model,â…¡.the thumb principal artery model,â…¢.the traffic model.The origin of the greater thenar vessels was as four aspects:(1) The cutaneous branches came from the superficial palmar branch of radial artery or its thumb radial-palmar digital artery, the external diameter was about 0.3～1.0mm.(2) The cutaneous branches came from the thumb radial-palmar digital artery which was from the thumb principal artery,the external diameter was about 0.4～0.8mm.(3) The cutaneous branches came from the thumb radial-dorsal artery,which distributed on the radial thenar.(4) The musculocutaneous perforators were from the deep vessel in thenar.These vessels originated from above four aspects formed a vessel net to supply thenar nutrition. According to the anatomic characteristics of the blood supply in greater thenar skin, three kinds of flap with pedicle were designed:(1) The thenar flap pedicled with thumb radial-palmar digital artery originated from the superficial palmar branch of radial artery,(2) The thumb radial-palmar digital artery perforator flap,(3) The radial-dorsal thenar fasciocutaneous flap.Clinical application: In clinic,5 cases used the thenar flap pedicled with thumb radial-palmar digital artery originated from the superficial palmar branch of radial artery,8 cases used the thumb radial-palmar digital artery perforator flap,5 cases used the radial-dorsal thenar fasciocutaneous flap.All flaps survived in 18 cases,4mm margin skin was necrosis in 1 case,which healed after decrustation.After 6 to 24 months postoperative follow-up,with an average of 10 months,the blood supply and texture of the flaps were excellent,their appearance and function were satisfactory.1 case of the thumb interphalangeal joint had hallux flexus because the flap was a little small.1 case of metacarpophalangeal joint had extension injury because of cicatricial contracture.The function of palmar opposition and digital opposition in all the thumbs was excellent except a case of thumb nub.Of 7 cases of flaps with reconnected nerves,the average of the two-point discrimination was 7-11 mm.Of 11 cases that the nerves were not connected,the sense only recovered to S₂～S₃ in 8 cases,and S₁ in 3 cases.CONCLUSIONFour kinds of the artery origin formed blood supply in the greater thenar,the branches which came from the superficial palmar branch(arch) of radial artery was the most important blood supply.5～8 cutaneous branches of the thumb radial-palmar digital artery across the thenar supplied thenar nutrition when blood vessel type wasâ… model orâ…¢model,and most branches were from radial side of the thumb radial-palmar digital artery.The small branches came from the superficial palmar branch supplied proximal thenar nutrition,and 2～4 cutaneous branches of the thumb radial-palmar digital artery which came out from the thenar muscles terminal supplied the distal or radial-dorsal skin of greater thenar,these cutaneous branches were at an angle of 120°～180°to the thumb radial-palmar digital artery,and formed vessel net with the branches of the superficial palmar branch at proximal thenar,and formed vessel net with the branches of thumb radial-dorsal artery at radial-dorsal thenar.The thumb radial-dorsal artery was smaller,its branches formed vessel net with the branches of the thumb radial-palmar digital artery at the course.The thenar blood supply followed the principle of pressure balance,that was to say,a local vessel was thicker,distribution area was bigger,and another local vessel was thiner,distribution area was smaller.These vessels originated from above four aspects formed a vessel net to supply thenar nutrition.According to the anatomic characteristics of the blood supply in greater thenar skin,three kinds of flap with pedicle were designed:(1) The thenar flap pedicled with thumb radial-palmar digital artery originated from the superficial palmar branch of radial artery,(2) The thumb radial-palmar digital artery perforator flap,(3) The radial-dorsal thenar fasciocutaneous flap.Above three kinds of thenar flap are safe and reliable,they are ideal methods for repairing thumb soft tissue defect,but each method has its advantages and disadvantages.Of three kinds of flaps,the thenar flap pedicled with thumb radial-palmar digital artery originated from the superficial palmar branch of radial artery has rich blood supply,the flap area is bigger enough to repair the thumb larger defect,but this method maybe cause palmar skin damage,and its application was confined.The thumb radial-palmar digital artery perforator flap causes the smallest damage to palmar skin,and blood supply is reliable,this kind of flap has the highest clinic application value.The radial-dorsal thenar fasciocutaneous flap is a little worse in blood supply than the others,and adapt to repair the small area damage.Different method could be choosed according to the situation of tissue defect in clinic.