Dynamic External Fixation In The Management Of Intraarticular Phalangeal Fracture Dislocation Of The Hand And Coherent Research Of Biomechanics

【Objective】Now with regard to the management of intraarticular fracture-dislocation of the finger, some disputation may be existed. Someinvestigators emphasize that anatomical reduction of the fracturedarticular surface must be obtained, but the others in order to acquireearly-motions of the articulation, adopt external fixation to maintaindistraction of injured joint, intraarticular fracture-dislocation may bereduced by ligamentotaxis. Early motion should be instituted to minimizearticular adhesions and contractures. With this method we designedunilateral combined dynamic external fixation which combined withexamples of phalangeal articulation to make living models. The coherentresearch of biomechanics was progressed to acknowledge the confidenceinterval of traction force and elastic modulus of the external fixator.We evaluate the therapeutic efficacy of the dynamic external fixation withlimited internal fixation in the management of intraarticular phalangealfracture-dislocation of the hand.【Methods】Three springs of two type is assembled to organize the fixatorpartition of the oneself-designed component dynamic external fixation.12 fingers of the hand were obtained which comprise of 3 examples for index,middle, ring and little. The examples of 12 proximal interphalangeal jointwere acquired by removing the skin, soft tissue, tendon of the fingersand preserving palmar plate, ligaments, capsule and the partition ofcentral tendon which located dorsally of proximal interphalangeal joint.The two K-wires are inserted separatively into either side of proximalinterphalangeal joint from the dorsal cortical bone vertically. EachK-wire sheathed with one coil spring and steel-wire is bent palmarly.And then the digit partition of dynamic external fixation is accomplished. The living model consists of the fixator partition and digit partitionwhich are assembled. The 12 living models were located into the test systemto complete tensile test. We can record the data of force and displacementby MAX software, and calculate the confidence interval of traction forceand elastic modulus by utilizing these data. During the progress ofclinical application, we used oneself-designed component dynamicexternal fixation combined with limited internal fixation in thetreatment of 16 patients. The injured joint with the external fixator wasalways flexed passively to acquire 1cm longitudinal slit in the extensortendon in operation. The slit can avoid adhesion of tendon and convenientthe early postoperative motions.【Results】The force of traction is comparative permanent and there is negativecorrelation between the variation of stress and the variation ofdisplacement. The 10 examples of 12 are accord with the regulation ofbiomechanics, and the other 2 examples are not. It is confirmed that theforce of traction correspond to normal distribution and 95% confidenceinterval is (3.43N, 8.40N). Interclass comparison of 10 living models haveno significant difference on statistics with ANOVA byα=0.05 standard.After 2-12 weeks average 7.4 weeks follow-up, the result was affirmativeby X-ray, pain, swelling, complications and active range of motion.【Conclusion】The mean of traction force is 5.104N. It is well tolerable bypatients. Although the dynamic external fixation is oneself-designed,there is no significant difference on statistics into the 10 externalfixators which can be generalized in clinical application. With cheap,simple performance and low tissue injured, the dynamic external fixationis an ideal device which can obtain the effective immobilization, maintain the traction and permit early joint mobilization. By the postoperativeX-rays, it is identified that this dynamic external fixation can correctthe subluxation or dislocation, maintain the concentric reduction andobtain good congruency of the injured joint. It also prevents fibrousthickening of collateral ligaments contractures of the capsule withpersistent distraction. Early joint motion reduces swelling and pain,facilitates joint nutrition and surface remodeling and preventspathological changes in the cartilage. Combined with limited internalfixation, it can promote stability of the joint and acquire anatomyreduction of articular surface which would be possible. Moreover it canbe removed at an earlier time with the pedestal of internal fixation. Inaddition, the dynamic external fixation combined with limited internalfixation is an ideal method in the management of intraarticular phalangealfracture-dislocation.