DESIGN AND CLINICAL APPLICATION OF NITINOL PATELLAR CONCENTRATOR

摘要

In order to avoid partial and total patellectomy, an internal fixator, the Nitinol Patellar Concentrator (NT-PC) was designed for treating every type of patellar fracture, especially for severely comminuted fractures. The NT-PC is made of the biomemory material Nitinol alloy. It was designed in accordance with the anatomy and biomechanics of the patella, consisting of two basis patellae daws, three apex patellae claws, and a conjunctive waist. The NT-PC was created to have one-way shape memory effect, and the shape reversion temperature is 30 +- 2℃. Three-dimensional (3-D) photoelasticity and 3-D finite-element analysis by ANSYS were used to perform biomechanics tests. In clinical application, it was unfolded in aqua astricta, placed on a fractured patella. After body temperature effected shape reversion, the radian difference between the NT-PC and the patella made the NT-PC tightly fix the comminuted patellar until the fracture healed. Between June of 1986 and February of 1995, 4013 cases were treated by NT-PC. The follow-up time was 2 to 27 months, averaging 5.6 months. Clinical studies showed that the sidestep was smaller than 1 mm in 31 cases, 2 mm in 24 cases, 3 mm in 11 cases, and the anatomical reduction rate was 98.36%. On average, within 7.14 weeks, the function of the injured leg matched that of the healthy one. No case required a patellectomy. The design of the NT-PC is reasonable, and it is easy to use. Plaster bandaging was not necessary after operation, and there is no doubt that it is a good method for replacing partial and total patellectomy.