The Sectional Imaging Anatomy Of Thumb Trapeziometacarpal Joint

Objective:To provide the sectional imaging anatomy basis for the imaging diagnosis andsurgical treatment of pathological thumb trapeziometacarpal joint and its surroundingligaments through studying the sectional imaging anatomy of thumb trapeziometacarpaljoint and its surrounding ligaments and applying operation simulation in volar and dorsalsurgical approaches.Materials and Methods:To collect8(male6, female2) hand specimens of the Chinese adults. The transversal,sagittal and coronary sectional specimens of8mm was obtained with an electric sectionalband saw according to equal distance. To collect10healthy volunteers (male8, female2).The transversal, sagittal and coronary MR images were obtained by GE Signa HDe1.5T systemic MRI scanners and AW4.4type image post-processing workstation. Thetransversal, sagittal and coronary CT images of two healthy male volunteers were obtainedby Philip Brilliance16rows spiral CT through thin layer scanning. One healthy malevolunteer was inspected by the X-ray plane film.The images were obtained inposterior-ranterior position, posterior-anterior oblique position, radial-adduction position,position and ulnar-adduction position. One hand specimens was used in thumbtrapeziometacarpal joint simulating surgery in volar and dorsal surgical approaches afterobtaining CT and MR images. To clarify complex anatomy of the thumbtrapeziometacarpal joint and its surrounding ligaments through contrasting continuoussectional specimens with CT and MRI images and combining hand specimens’s operationsimulation results.Results:The transverse sectional anatomy of the distal part of distal carpal bones and thumb trapeziometacarpal joint shows the base of the first metacarpal, the second metacarpal,the third metacarpal and distal carpal bones. From the radial to the ulnar as follows: thebase of the first metacarpal, trapezium, the base of the second metacarpal, trapezoid, thethird metacarpal, capitatum and hamate. The thumb trapeziometacarpal joint is composedof the base of the first metacarpal and the distal edge of trapezium. The radial-dorsal sideof thumb trapeziometacarpal joint shows the dorsal ligament complex and the ulnar volarside shows the volar beak ligament.The coronary sectional anatomy of the scaphoid and the anterior edge of trapeziumshows scaphoid, trapezium and the first metacarpal. The intercarpal joint is composedof the distal eage of scaphoid and the proximal edge of trapezium. The anterolateral ofthe intercarpal joint shows thumb trapeziometacarpal joint, which is composed of the baseof the first metacarpal and the distal of trapezium. The radial dorsal side of thumbtrapeziometacarpal joint shows the dorsal ligament complex and the ulnar volar side showsthe volar beak ligament.The sagittal sectional anatomy of the ulnar edge of the first metacarpal shows theulnar edge of the first metacarpal, trapezium, scaphoid and the distal radius. Thumbtrapeziometacarpal joint, which is composed of the base of the first metacarpal and thedistal of trapezium, is a saddle joint inosculated with both formation. The dorsal and volarof trapezium convex to the distal. The dorsal and volar of the base of the first metacarpalis concave, the central part convex to the proximal.The volar beak ligament is tensioned when the thumb is placed in the hitchhikerposition, and the volar beak of the thumb metacarpal disengaged from the trapezium recess,and the the dorsal ligament complex is lax. Thumb trapeziometacarpal joint is unstable inthe hitchhiker position.The volar beak ligament is lax in the screw home torque rotationopposition, and the volar beak of the thumb metacarpal engaged the trapezium recess, andthe the dorsal ligament complex is tensioned. Thumb trapeziometacarpal joint is stable inthe screw home torque rotation opposition.The operation simulation in the volar approach prompt that after incising skin andseparating subcutaneous tissue, the radial branch of the superficial radial nerve can beseparated,which is in the volar side of the abductor pollicis longus tendon, a dorsal tractionwith rubber strips to the nerve can avoid injurying the nerve. The operation simulation inthe dorsal approach prompt that after separating the abductor pollicis longus tendon, thedorsal ligament complex can be exposed, which is in the deep of the abductor pollicislongus tendon. The dorsal ligament complex arises from the radial tubercle of the trapezium and inserts at the dorsal base of the thumb metacarpal. The dorsal ligamentcomplex is the key to the screw home torque rotation phase of opposition.Conclusion:(1) The transverse section through the distal part of distal carpal bones，the coronarysection through the scaphoid and the anterior of trapezium，and the sagittal sectionthrough the ulnar base of the first metacarpal is the tipycal section to identify thumbtrapeziometacarpal joint respectively.(2) The volar beak ligament is tensioned and the the dorsal ligament complex is laxwhen the thumb is placed in the hitchhiker position. Thumb trapeziometacarpal joint isunstable in the hitchhiker position.The volar beak ligament is lax and the the dorsalligament complex is tensioned in the screw home torque rotation opposition. Thumbtrapeziometacarpal joint is stable in the screw home torque rotation opposition.(3) The operation simulation prompt that the dorsal ligament complex is the key to thescrew home torque rotation phase of opposition. Repairing the dorsal ligament complex isthe key of recoverying the function of thumb trapeziometacarpal joint.