Mechanical strength and degradation in vivo of human hair polylactic acid composite rods

Dong YIN; Anmin JIN; Weidong ZHAO; Wenhua HUANG; Lei YU; Lin YUAN

ABSTRACT

BACKGROUND:

Biodegradable internal fixation devices have been used in clinics. However, they can only be used for internal fixation of non weight-bearing bones. A new kind of biodegradable internal fixation device with high initial strength and slow early degradation, which can be used for weight-bearing bones, is required.

OBJECTIVE:

To test the initial strength and observe the degradation of human hair polylactic acid (HHPLA) composite rods.

DESIGN:

Repeated measurement design

SETTING:

Center of Orthopaedic Department, Zhujiang Hospital, Southern Medical University; Department of Human Anatomy of Southern Medical UniversityMATERIALS The experiment was conducted in the Southern Medical University between September 2002 and October 2003. Totally 54 adult SD rats were recruited.

METHODS:

①The shear strength, the bending strength and the bending modulus of 20 HHPLA composite rods were tested with the biomechanical testing system (MTS-858 Mini Bionix) to investigate the initial nechanical feature of HHPLA composite rods. ②A total of 108 samples of HHPLA composite rods, which were developed for internal fixation of fracture, were randomly implanted in bilateral dorsal subcutaneous tissue of 54 SD rats and taken out at weeks 1, 2, 4, 8, 12, 16, 20, 24 and 28 (6 rats at each time point). The weight losses were measured to understand the degradation of HHPLA composite rods in SD rats.MAIN OUTCOME

MEASURES:

①Mechanical strength of HHPLA composite rods. ②Degradation in vivo of HHPLA composite rods.

RESULTS:

Totally 54 rats entered the result analysis. ①HHPLA composite rods has good initial mechanical strength. Its shear strength of the HHPLA rod was 241 MPa, bending strength was 358 MPa, and the bending modulus was 13 GPa. ②HHPLA was fairly degradable in SD rats.Degradation was slower in the earlier period than that in the later period.

CONCLUSION:

HHPLA composite rods have some fairly good characteristics of initial mechanical strength and degradation in vivo.