Motion preservation for open book injuries of the pubic symphysis -a biomechanical cadaver study

Abstract

Introduction: Open book injuries are challenging injuries that oftentimes require surgical treatment. Currently, treatment is performed with symphyseal plating requiring extensive surgery and entirely limiting physiological movement of the symphyseal joint, frequently resulting in implant failure. Therefore, we investigated the biomechanical properties of a minimally invasive tape suture construct (modified SpeedBridge™) as an alternative stabilization technique for the treatment of open book injuries in human cadaver pelvic rings.

Materials and methods: The symphysis of 9 human cadaver pelvises was dissected and dilated to 3 cm creating an open book injury. Next, the two osteosynthesis methods (plating, modified SpeedBridge™) were applied. All specimens then underwent cyclic horizontal and vertical loading, simulating biomechanical forces while sitting, standing and walking. For statistical analysis, 3D dislocation (mm) was calculated.

Results: Total displacement (mm) of the pubic symphysis displayed the following means and standard deviations: native group 1.34 ± 0.62 mm, open book group 3.01 ± 1.26 mm, tape group 1.94 ± 0.59 mm and plate group 1.37 ± 0.41 mm. Comparison between native and open book (p = 0.029), open book and plate (p = 0.004), open book and tape (p = 0.031), as well as tape and plate group (p = 0.002) showed significant differences. No significant differences were found when comparing the native and tape (p = 0.059), as well as the native and plate (p = 0.999) group.

Conclusion: While both osteosynthesis techniques sufficiently stabilized the injury, symphyseal plating displayed the highest rigidity. The modified SpeedBridge™ as a tape suture construct provided statistically sufficient biomechanical stability while maintaining symphyseal micro mobility, consequently allowing ligamental healing of the injured joint without iatrogenic arthrodesis.

Keywords: Biomechanics; Flexible osteosynthesis; Minimally invasive; Pelvic instability; Pubic symphysis; SpeedBridge™.

Fig. 1

Experimental set-up with a specimen after simulation of an open book injury

Fig. 2

(a): Tape suture construct using a modified Speed Bridge™, (b): Symphyseal plating

Fig. 3

Graphical illustration of the biomechanical loading protocol

Fig. 4

Total symphyseal displacement (mm). Box and whiskers error bars indicate minimum and maximum values of mean symphyseal displacement with non-significant (ns) or significant results at a significance level of p < 0.05 (*) or p < 0.005 (**). GraphPad Prism (version 10.1.0 for macOS, GraphPad Software, Boston, Massachusetts USA)

Fig. 5

Incipiently screw loosening in anterior plating