Design of novel plate for fixation of anterior pelvic ring injury: a digital anatomy study and finite element analysis.

OBJECTIVE

To develop a novel internal fixation system for anterior pelvic ring injuries and to compare the biomechanical stability of this novel anatomical plate with conventional fixation devices in the management of Tile B1-type pelvic fractures using finite element analysis.

METHODS

A total of 200 pelvic thin-slice CT datasets were collected from healthy adults, comprising 100 male and 100 female subjects. The three-dimensional (3D) pelvic models were reconstructed using Mimics software. The following measurements were obtained: inter-pubic tubercle distance (ITD), inter-obturator foramen inner border distance (IOFIBD), superior-inferior distance of pubic symphysis (SIDPS), pubis superior ramus length from mid-external pubic tubercle to lateral obturator margin (PSR-LOTM), pubic symphysis gap (PSG), pubic symphysis upper plane-superior ramus angle (SPS-SRA), pubic symphysis-coronal plane angle (PS-CPA), maximum superior-inferior diameter of pubic superior ramus (SID-PSR), and anterior-posterior diameter of pubic superior ramus (APD-PSR). Standard pelvis models were selected and imported into SolidWorks software to design two novel plates. Finally, a Tile B1 pelvic finite element model was established and fixed using two novel plates, a single superior pubic symphysis plate, and a combination of anterior and superior pubic symphysis plates. A load of 500 N was applied to the model in three directions (cranial-caudal, anterior-posterior, and lateral-medial), and the stiffness was determined based on the maximum displacements.

RESULTS

The ITD was 48.93 ± 5.51 mm in males and 54.45 ± 5.15 mm in females; the IOFIBD was 46.67 ± 4.02 mm in males and 55.17 ± 4.46 mm in females; the SIDPS was 39.77 ± 4.12 mm in males and 36.76 ± 4.21 mm in females; the PSR-LOTM was 35.87 ± 4.04 mm in males and 37.62 ± 5.31 mm in females; the SPS-SRA was 135.67 ± 4.83° in males and 137.53 ± 4.46° in females; and the ITD + PSR-LOTM was 120.68 ± 10.66 mm in males and 124.70 ± 11.93 mm in females. Significant differences were observed between males and females for all these measurements (P < 0.05). These values were used as reference criteria for selecting standard pelvis models. The ITD + PSR-LOTM data were sorted in ascending order, and the medians of the 0-33%, 33-66%, and 66-100% intervals were used as references for selecting standard pelvis models. Based on the selected standard pelvis models, two designs and six length specifications (110, 115, 120, 125, 130, and 135 mm) of anatomical plates were developed. In the finite element analysis, the maximum displacements of the pelvis under three loading modes (cranial-caudal, anterior-posterior, and lateral-medial) were as follows: for Type A plate fixation, 0.357 mm, 0.192 mm, and 1.018 mm, respectively; for Type B plate fixation, 0.362 mm, 0.505 mm, and 1.133 mm, respectively; for single pubic symphysis superior plate fixation, 0.386 mm, 0.965 mm, and 1.232 mm, respectively; and for combined pubic symphysis anterior and superior plate fixation, 0.378 mm, 0.874 mm, and 1.151 mm, respectively.

CONCLUSIONS

We successfully developed two types of plates and designed different specifications to meet clinical needs. Preliminary biomechanical finite element analysis indicated promising fixation stability for Tile B1 type injuries, warranting further clinical investigation.