Memory of DL-polylactic acid biodegradable plates.

Biodegradable plates and screws have many advantages over metal plates and screws. Plates were injection-molded and made of DL-polylactic acid. Four-hole plates were bent with the use of a heated tip to angles of 30, 45, and 60 degrees. They were inserted in the subcutaneous space in the back of rabbits. After 2 weeks, the plates straightened, suggesting that the plates had a memory. The results were confirmed by similar in vitro investigations. The in vitro experiment was repeated with tempering of the plates. The plates were heated to a temperature of 200 degrees C for 45 seconds, cooled, and then again heated to 200 degrees C for 40 seconds. This process resulted in loss of memory of the plates. After 4 weeks, there was a change of the bending angle of less than 2.5 degrees.