四角融合术对桡腕关节内应力的影响

The effect of four-corner arthrodesis on the stress in the radiocarpal joint

目的比较四角融合前后桡腕关节内应力值、受力面积和平均压强的变化，研究四角融合术对桡腕关节内应力的影响。方法8例新鲜正常腕关节标本通过夹具固定于支架上，将150N负荷按比例加载于经过腕关节的各肌腱上，调节腕关节于不同位置，测量桡舟、桡月关节内的应力大小、受力面积和平均压强，测量结束后对标本行四角融合术，以同样方法进行测量，比较四角融合前后数据，分析四角融合对桡腕关节的影响。结果正常时，桡舟关节内受力面积占其关节面的3％～43％，桡月关节为6％～30％；四角融合后，桡舟关节为0％～30％，桡月关节为7％～32％。正常时和四角融合后，桡腕关节内的应力值、受力面积和平均压强随腕关节位置的变化而呈现相似的变化趋势，但正常时应力柔和渐变，四角融合后明显剧烈而僵硬。结论正常桡舟、桡月关节内有各自独立的应力承受区，其面积不等于实际的关节面积，根据腕关节的位置不同而有变化；四角融合后桡腕关节内的应力变化较正常时剧烈、僵硬，长期作用可能使腕关节内软骨发生退行性变化。

Objective To compare the stress, contact area and pressure change between pre- and post four-comer arthredesis. To study the effect of four-comer arthrodesis to the stress in radiocarpal joint. Methods Eight fresh-frozen forearm specimens were used in this investigation. The specimen were placed in a special jig, 150 N load was distributed to tendons passing through the wrist according to a certain proportion. Place and maintain the wrist in different positions, the prescale film was encapsulated and inserted into the radiocarpal joint. Then performed a simulated four-comer arthrodesis, did the same process and gained the corresponding results. Compare the three indexes between pre-and post four-comer arthrodesis. Results In normal radiocarpal joint, the contact area is 3% to 43% in scaphoid fossa and 6% to 30% in lunate fossa, after four-comer arthrodesis, it change to 0% to 30% in scaphoid fossa and 7% to 32% in lunate fossa, all the three indexes were changed according to the position of the wrist. In the normal joint, the stress change mild and gradually, post four-comer arthrodesis, the stress change is intense and rigid. Conclusion The stress, contact area and pressure in the scaphoid and lunate fossa are different and change according to the position of the wrist. The change in the radiocarpal joint after four-comer arthrodesis is acute and hard, which will perhaps interfere the cartilage in the long run.