Anatomical And Biomechanical Studies Of The Distal Joint Of The Ruler

PART 1 ANATOMICAL STUDY OF DISTAL RADIOULNAR JOINTObjective Through dissecting the relevant bone and soft tissue structure of the distal radioulnar joint stability,to understand the anatomy of distal radioulnar joint,measure the length of the radial flexor tendon and the palm long tendon,measure the relevant data of the tfcc ligaments,which provides anatomical basis for simulating the two kinds of operation for distal radioulnar joint instability.Methods Four adult upper limb specimens were selected,and cut the skin in the middle of the forearm,find out the palm of the tendon and radial wrist flexor and free them,observe their shape and position,measure the length of the tendon part.Remove all the flexor tendon and extensor tendons,keep the specimen contains only ulnar,radius and the last row of carpal bones.Observe the beginning and end of the tfcc ligament structure and its relationship with the wrist joint disc.Take out the tfc as a whole,measure the length and thickness of the radial margin,palm margin and dorsal margin of the tfc with a vernier caliper.Results(1)Palm long tendon locate in the middle of forearm palm side,starting from the total starting point of flexor and deep fascia,over the shallow surface of wrist palms deep fascia andcontinued in the palmar aponeurosis.The length of the tendon part is(12.83 ± 1.13)cm;(2)Flexor carpi radialis start from the medial epicondyle of the humerus and the forearm palmar deep fascia,its muscle belly shift to the tendon in the middle of forearm,it go through the wrist transverse ligament deep and stop at the palm face of 2,3 metacarpal base.The length of the tendon part is(14.15 ± 1.76)cm;(3)The distal radioulnar joint is composed of elliptical cylindrical ulnar head and radial sigmoid notch,surrounded by the joint capsule and triangular fibrous cartilage and other soft tissue.The average radius of curvature of the ulnar head is 10 mm.and that of the radial sigmoid notch is 15 mm.(4)TFCC start from of the palm and dorsal edge of the radius,respectively,stop at ulnar styloid,ulnar fossa,triangular bone,lunate bone and the fifth metacarpal base.Conclusions(1)Palm long tendon and flexor carpi radialis have long tendon parts for transplantation and translocation fixed unstable distal radioulnar joint;(2)The curvature radius of the radial head exceeds the curvature radius of the ulnar head by 4-7mm,and the articular surface of the ulnar head and the radial sigmoid notch does not match.Therefore,the stability of the skeletal structure of DRUJ is poor,which leads to its dependence on soft tissue stability.PART 2 BIOMECHANICAL STUDY OF SOFT TISSUE RECONSRUCTION IN TREATMENT OF DISTAL RADIOULNAR JOINT INSTABLITYObjective By mechanical loading,evaluate the effectiveness of the two methods in reconstructing the stability of distal radioulnar and to explore the feasibility and effect of the two methods.Methods Eight adult upper limb specimens were selected and four models were prepared on the same specimen:(1)ligament complete model(normal group);(2)ligament injury model(injury group);(3)reconstruction of radioulnar ligament with palm long tendon graft model(palm long tendon group);(4)partial flexor carpi radialis translocation fixed distal radioulnar joint model(Flexor carpi radialis grop).The specimens were fixed with an external fixator to construct a multi-planar configuration,fix the external fixation on the torsion mechanical testing machine,simulate the forearm rotation activity through the machine and measure the torque changes during rotation.Results(1)There was significant difference in pronation and supination torque between normal group and injury group regardless of what kind of flexion and extension of the wrist;(2)The difference between the normal group and palm long tendon reconstruction groupwas not statistically significant.;(3)There was no statistically significant torque between normal group and flexor carpi radialis group when the wrist is located at carpal dorsiflexion 30 °and extension position,but was statistically significant at carpal flexion 30 °.Conclusions(1)After cutting the radial ulnar ligament,the rotational torque of the forearm was significantly lower than that of the normal group,indicating that the stability of the distal radioulnar joint was destroyed after cutting the radioulnar ligament;(2)There was no significant difference in the torque between the normal group and palm long tendongroup,and the kinds of operations that reconstruct radioulnar ligament in its anatomical direction was considered to restore the torque of the DRUJ;(3)After the reconstruction with transposition of the partial flexor carpi radialis,the stability of the wrist in carpal dorsiflexion 30 °and extension position was restored,but in carpal flexion 30 ° when there is still joint instability.