Biodegradable mini plate and screw: a secure method for internal fixation of symphysis pubis in animal model of pubic diastasis

Abstract

Objectives: To investigate short-term results of symphysis pubis reapproximation in a simulated animal model of pubic diastasis using biodegradable plate and screw, in comparison with animals with no fixation, in terms of inflammatory reaction, histologic changes, and three-dimensional pelvic bone CT (3D-CT) scan.

Methods: Fifteen male goats were divided in 3 groups and underwent midline pubic symphysiotomy. In GI (n = 6), the pubes were brought together with sutures through the bone and fixed by placing a biodegradable plate and screws. In GII (n = 3), symphysis was brought together by inserting sutures. Animals' pubes received no fixation in GIII (n = 6). Three-dimensional CT scan was performed, after 3 months in GII, and at the third and sixth months in GI and GIII. Furthermore, tissue-implant interface was examined for tissue reaction and implant degradation.

Results: Pelvic bone 3D-CT scan in the biodegradable group revealed characteristic differences in pubic diastasis, iliac wing angle, and inter-triradiate distance compared with GII and GIII. Decreases of 21.8 +/- 0.7 mm, 7.28 +/- 0.4 mm, and 7.43 +/- 1.5 degrees were observed in pubic diastasis, inter-triradiate distance, and iliac wing angle, respectively, in biodegradable group in comparison with GIII in the sixth month. Neither clinical nor histologic evidence of inflammation due to insertion of biodegradable system was reported.

Conclusions: Pubic bone adaptation with biodegradable plate and screws is a safe and reliable procedure for secure anterior pubic fixation in bladder exstrophy. Easy intraoperative handling, no long-term traction, biocompatibility, and no disturbance in skeletal growth are important prerequisites for introduction of this method of pubic approximation into clinical practice.