Biomechanical comparison of a new minimally invasive technique versus conventional plating for the treatment of open book symphyseal injuries in osteoporotic human pelvises

Abstract

Purpose: Traumatic open book injuries of the pubic symphysis require stable fixation while minimizing surgical morbidity. Traditional symphyseal plating is associated with complications such as implant failure and infections. This study aims to evaluate the biomechanical performance of a novel minimally invasive technique using an internal fixator (IF) compared to conventional plating (symphyseal locking dynamic compression plate [SLDCP]) in human cadaveric pelvises.

Methods: Ten human cadaveric pelvises were assigned to two groups (n = 5 each). After anatomical reduction, either SLDCP or IF stabilization was applied. Intrasymphyseal compression forces, contact area and interfragmentary motion were assessed using pressure-sensitive sensor films and an optical tracking system under incrementally applied axial loads up to 600 N. Bone density and symphyseal dimensions were measured and were comparable across both groups.

Results: At key loading stages (400 and 600 N), the IF group demonstrated significantly higher intrasymphyseal compression forces (IF 61.78 ± 31.98 N vs. SLDCP 15.98 ± 8.2 N at 400 N and IF 42.82 ± 25.2 N vs. SLDCP 9.42 ± 5.81 N at 600 N) and larger contact areas (IF 453 ± 137.6 mm² vs. SLDCP 216 ± 135 mm² at 400 N and IF 337.6 ± 168.45 mm² vs. SLDCP 154 ± 59.73 mm² at 600 N), with more homogeneous segmental force and area distributions. Higher compression forces, particularly in the caudal symphyseal region (IF 23.68 ± 18.69 N vs. SLDCP 13.78 ± 10.1 N), were achieved. Three-dimensional analysis showed reduced fragment displacement in the IF group under load.

Conclusion: The proposed technique using an internal fixator provided superior biomechanical stability compared to standard plating, offering a promising minimally invasive alternative for managing open book injuries. The technique facilitates uniform force transmission and improved contact conditions, which may enhance healing and reduce complications.

Level of evidence: N/A.

Keywords: biomechanical analysis; internal fixator; open book injuries; pelvic ring fractures; pubic symphysis.

Figure 1

Reduction using a pointed forceps and fixation with a 3.5 SLDCP. SLDCP, symphyseal locking dynamic compression plate.

Figure 2

Reduction using a pointed forceps and (a) insertion of Schanz screws on either side of the symphysis, (b) creating caudal compression using socket wrenches and (c) cranial compression.

Figure 3

(a) Mean of the pubic symphysis size in the sagittal plane of the CT analysis. (b) Mean of the HU at S1 in sagittal and axial CT analysis. CT, computed tomography; HU, Hounsfield units; SLDCP, symphyseal locking dynamic compression plate.

Figure 4

Intrasymphyseal compression forces (a) and contact area (b) (mean ± SEM). *Asterix mark statistical significance. SEM, standard error of the mean; SLDCP, symphyseal locking dynamic compression plate.

Figure 5

Segmental compression force distribution (mean ± SEM). SEM, standard error of the mean; SLDCP, symphyseal locking dynamic compression plate.

Figure 6

Segmental area distribution (mean ± SEM). SEM, standard error of the mean; SLDCP, symphyseal locking dynamic compression plate. *p < 0.05 versus final stabilization.