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Comparative Study
. 2012 Sep 27:7:31.
doi: 10.1186/1749-799X-7-31.

Biomechanical stability of a supra-acetabular pedicle screw internal fixation device (INFIX) vs external fixation and plates for vertically unstable pelvic fractures

Jonathan M Vigdorchik  1 , Amanda O Esquivel, Xin Jin, King H Yang, Ndidi A Onwudiwe, Rahul Vaidya
Affiliations
Comparative Study

Biomechanical stability of a supra-acetabular pedicle screw internal fixation device (INFIX) vs external fixation and plates for vertically unstable pelvic fractures

Jonathan M Vigdorchik et al. J Orthop Surg Res. .

Abstract

Background: We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model.

Methods: Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons

Results: The mean displacement at the pubic symphysis was 20, 9 and 0.8 mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P = 0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P = 0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups.

Conclusions: Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used.

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Figures

Figure 1
Figure 1
Case Example a) Xray APC 3 Pelvic injury b) CT scan showing opening of Right SI joint c) Fixation with posterior SI screws and INFIX anteriorly d) Incisions for insertion of INFIX before closure.
Figure 2
Figure 2
The APC III pelvis model with complete disruption of the right SI joint and Symphysis pubis.
Figure 3
Figure 3
The pelvis mounted on the apparatus with the INFIX Apparatus. The sacrum is attached to the Instron Device and the separated hemi pelvis is fixed with wire cables to simulate the abductor muscles with the Hip prosthesis potted to simulate the single stance gait.
Figure 4
Figure 4
Loading of the construct with the INSTRON 200N or 15 mm.
Figure 5
Figure 5
Picture of the testing apparatus.
Figure 6
Figure 6
Mean displacement of each construct under axial loading.
Figure 7
Figure 7
Comparison of mean stiffness of the INFIX and external fixation to internal fixation.
See this image and copyright information in PMC

References

    1. Gardner MJ, Kendoff D, Ostermeier S, Citak M, Hüfner T, Krettek C, Nork SE. Sacroiliac joint compression using an anterior pelvic compressor: a mechanical study in synthetic bone. J Orthop Trauma. 2007;21(7):435–441. doi: 10.1097/BOT.0b013e318126bb8e. - DOI - PubMed
    1. Gardner MJ, Nork SE. Stabilization of unstable pelvic fractures with supraacetabular compression external fixation. J Orthop Trauma. 2007;21(4):269273. - PubMed
    1. Grimm MR, Vrahas MS, Thomas KA. Pressure-volume characteristics of the intact and disrupted pelvic retroperitoneum. J Trauma. 1998;44(3):454–459. doi: 10.1097/00005373-199803000-00006. - DOI - PubMed
    1. Kregor PJ, Routt ML Jr. Unstable pelvic ring disruptions in unstable patients. Injury. 1999;30(Suppl 2):B19–B28. - PubMed
    1. Riemer BL, Butterfield SL, Diamond DL, Young JC, Raves JJ, Cottington E, Kislan K. Acute mortality associated with injuries to the pelvic ring: the role of early patient mobilization and external fixation. J Trauma. 1993;35(5):671–675. doi: 10.1097/00005373-199311000-00003. discussion 676–677. - DOI - PubMed

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