All Title Author
Keywords Abstract


Monoaxial Pedicle Screws Are Superior to Polyaxial Pedicle Screws and the Two Pin External Fixator for Subcutaneous Anterior Pelvic Fixation in a Biomechanical Analysis

DOI: 10.1155/2013/683120

Full-Text   Cite this paper   Add to My Lib

Abstract:

Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 ± 0.113?Nmm monoaxial, 3.638 ± 0.108?Nmm Click-x; 3.634 ± 0.147?Nmm Pangea) than the exfix system (2.882 ± 0.054?Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360?N) than exfixes (160?N) and polyaxial devices which failed if distracted greater than 4?cm (157?N Click-x or 138?N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360?N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems. 1. Introduction A technique of subcutaneous anterior pelvic fixation for anterior pelvic ring fractures has been recently reported and has been termed “infix” [1]. It involves two supra-acetabular pins [2–5] and a subcutaneous rod, tunneled under the skin, at the top of the “bikini area” [6, 7]. In a multicenter study, infix has been shown to be effective in the treatment of pelvic fractures when combined with the appropriate posterior fixation. It has good patient tolerance, avoids the traditional complications of external fixation [8], and is useful to reduce pelvic injuries [9, 10]. When constructed with traditional polyaxial pedicle screws, infix is biomechanically as effective at posterior SI compression as a femoral distracter [11] and stiffer than a traditional 2 pin anterior external fixator in single stance gait testing in synthetic pelvic models [11, 12]. Pedicle screw implants use a rod screw construct which can be made with monoaxial screws where the head of the pedicle screw is immobile or polyaxial screws where the head of the pedicle screw can rotate in several directions. Polyaxial screws allow surgeons maneuverability when applying these devices, so that the screw heads do not have to line up exactly to attach the rod. The maneuverability of these screws is at the expense of some strengths of the

References

[1]  R. Vaidya, R. Colen, J. Vigdorchik, F. Tonnos, and A. Sethi, “Treatment of unstable pelvic ring injuries with an internal anterior fixator and posterior fixation: initial clinical series,” Journal of Orthopaedic Trauma, vol. 26, no. 1, pp. 1–8, 2012.
[2]  G. J. Haidukewych, S. Kumar, and B. Prpa, “Placement of half-pins for supra-acetabular external fixation: an anatomic study,” Clinical Orthopaedics and Related Research, no. 411, pp. 269–273, 2003.
[3]  W.-Y. Kirn, T. C. Hearn, O. Seleem, E. Mahalingam, D. Stephen, and M. Tile, “Effect of pin location on stability of pelvic external fixation,” Clinical Orthopaedics and Related Research, no. 361, pp. 237–244, 1999.
[4]  K. Abumi, M. Saita, T. Iida, and K. Kaneda, “Reduction and fixation of sacroiliac joint dislocation by the combined use of S1 pedicle screws and the Galveston technique,” Spine, vol. 25, no. 15, pp. 1977–1983, 2000.
[5]  K.-J. Ponsen, P. Joosse, G. A. H. van Dijke, and C. J. Snijders, “External fixation of the pelvic ring: an experimental study on the role of pin diameter, pin position, and parasymphyseal fixator pins,” Acta Orthopaedica, vol. 78, no. 5, pp. 648–653, 2007.
[6]  R. Vaidya, B. Oliphant, R. Jain et al., “The bikini area and bikini line as a location for anterior subcutaneous pelvic fixation: an anatomic and clinical investigation,” Clinical Anatomy, vol. 26, no. 3, pp. 392–399, 2013.
[7]  D. J. Merriman, W. M. Ricci, C. M. McAndrew, and M. J. Gardner, “Is application of an internal anterior pelvic fixator anatomically feasible?” Clinical Orthopaedics and Related Research, vol. 470, no. 8, pp. 2111–2115, 2012.
[8]  R. Vaidya, E. N. Kubiak, P. F. Bergin et al., “Complications of anterior subcutaneous internal fixation for unstable pelvis fractures: a multicenter study,” Clinical Orthopaedics and Related Research, vol. 470, no. 8, pp. 2124–2131, 2012.
[9]  M. J. Gardner, S. Mehta, A. Mirza, and W. M. Ricci, “Anterior pelvic reduction and fixation using a subcutaneous internal fixator,” Journal of Orthopaedic Trauma, vol. 26, no. 5, pp. 314–321, 2012.
[10]  R. Vaidya, B. W. Oliphant, I. Hudson, M. Herrema, and D. Knesek, “Sequential reduction and fixation for windswept pelvic ring injuries (LC3) corrects the deformity until healed,” International Orthopaedics, vol. 37, no. 8, pp. 1555–1560, 2013.
[11]  J. M. Vigdorchik, A. O. Esquivel, X. Jin, K. H. Yang, and R. Vaidya, “Anterior internal fixator versus a femoral distractor and external fixation for sacroiliac joint compression and single stance gait testing: a mechanical study in synthetic bone,” International Orthopaedics, vol. 37, no. 7, pp. 1341–1346, 2013.
[12]  J. M. Vigdorchik, A. O. Esquivel, X. Jin, K. H. Yang, N. A. Onwudiwe, and R. Vaidya, “Biomechanical stability of a supra-acetabular pedicle screw Internal Fixation device (INFIX) vs External Fixation and plates for vertically unstable pelvic fractures,” Journal of Orthopaedic Surgery and Research, vol. 7, no. 1, article 31, 2012.
[13]  M. T. Owen, B. Tinkler, and R. Stewart, “Failure and aalvage of “INFIX” instrumentation for pelvic ring disruption in a morbidly obese patient,” Journal of Orthopaedic Trauma, vol. 27, no. 10, pp. e243–e246, 2013.
[14]  M. Tile, “The management unstable injuries of the pelvic ring,” Journal of Bone and Joint Surgery B, vol. 81, no. 6, pp. 941–943, 1999.
[15]  E. W. Van den Bosch, R. van der Kleyn, M. Hogervorst, and A. B. van Vugt, “Functional outcome of internal fixation for pelvic ring fractures,” Journal of Trauma, vol. 47, no. 2, pp. 365–371, 1999.
[16]  W. T. M. Mason, S. N. Khan, C. L. James, T. J. S. Chesser, and A. J. Ward, “Complications of temporary and definitive external fixation of pelvic ring injuries,” Injury, vol. 36, no. 5, pp. 599–604, 2005.
[17]  K. Abumi, M. Saita, T. Iida, and K. Kaneda, “Reduction and fixation of sacroiliac joint dislocation by the combined use of S1 pedicle screws and the Galveston technique,” Spine, vol. 25, no. 15, pp. 1977–1983, 2000.

Full-Text

comments powered by Disqus