The stabilizing potential of anterior, posterior and combined techniques for the reconstruction of a 2-level cervical corpectomy model: biomechanical study and first results of ATPS prototyping
- 383 Downloads
Clinical studies reported frequent failure with anterior instrumented multilevel cervical corpectomies. Hence, posterior augmentation was recommended but necessitates a second approach. Thus, an author group evaluated the feasibility, pull-out characteristics, and accuracy of anterior transpedicular screw (ATPS) fixation. Although first success with clinical application of ATPS has already been reported, no data exist on biomechanical characteristics of an ATPS-plate system enabling transpedicular end-level fixation in advanced instabilities. Therefore, we evaluated biomechanical qualities of an ATPS prototype C4–C7 for reduction of range of motion (ROM) and primary stability in a non-destructive setup among five constructs: anterior plate, posterior all-lateral mass screw construct, posterior construct with lateral mass screws C5 + C6 and end-level fixation using pedicle screws unilaterally or bilaterally, and a 360° construct. 12 human spines C3–T1 were divided into two groups. Four constructs were tested in group 1 and three in group 2; the ATPS prototypes were tested in both groups. Specimens were subjected to flexibility test in a spine motion tester at intact state and after 2-level corpectomy C5–C6 with subsequent reconstruction using a distractable cage and one of the osteosynthesis mentioned above. ROM in flexion–extension, axial rotation, and lateral bending was reported as normalized values. All instrumentations but the anterior plate showed significant reduction of ROM for all directions compared to the intact state. The 360° construct outperformed all others in terms of reducing ROM. While there were no significant differences between the 360° and posterior constructs in flexion–extension and lateral bending, the 360° constructs were significantly more stable in axial rotation. Concerning primary stability of ATPS prototypes, there were no significant differences compared to posterior-only constructs in flexion–extension and axial rotation. The 360° construct showed significant differences to the ATPS prototypes in flexion–extension, while no significant differences existed in axial rotation. But in lateral bending, the ATPS prototype and the anterior plate performed significantly worse than the posterior constructs. ATPS was shown to confer increased primary stability compared to the anterior plate in flexion–extension and axial rotation with the latter yielding significance. We showed that primary stability after 2-level corpectomy reconstruction using ATPS prototypes compared favorably to posterior systems and superior to anterior plates. From the biomechanical point, the 360° instrumentation was shown the most efficient for reconstruction of 2-level corpectomies. Further studies will elucidate whether fatigue testing will enhance the benefit of transpedicular anchorage with posterior constructs and ATPS.
KeywordsCervical spine Biomechanical study Corpectomy Pedicle screw Reconstruction
The authors thank Synthes for financial support to perform the biomechanical study and for implants provided. With the ATPS concept, there is no patent closed or pending that might hinder further engineering on the issue.
- 9.Bransford RJ, Russo A, Freeborn M, Nuyen Q, Lee MJ, Chapman J, Bellabarba C (2009) Posterior C2 instrumentation: accuracy and risks associated with four techniques. In: 16th international meeting on advanced spine technologies, ViennaGoogle Scholar
- 12.Cha SH, Kim C, Choi BK, Kim HJ, Baek SY (2007) C-arm assessment of cervical pedicle screw-coaxial fluoroscopy and oblique view. Eur Spine J 32:1721–1727Google Scholar
- 15.Dailey A, Fassett D, Finn M, Bacchus K, Brodke D (2008) Do dynamic cervical plates provide adequate stability in flexion distraction injuries? In: Annual meeting of the CSRS, Austin, TXGoogle Scholar
- 29.Koller H, Acosta F, Tauber M, Fox M, Martin H, Forstner R, Augat P, Penzkofer R, Pirich C, Kässmann H, Resch H, Hitzl W (2008) Cervical anterior transpedicular screw fixation (ATPS)—Part II. Accuracy of manual insertion and pull-out strength of ATPS. Eur Spine J 17:539–555PubMedCrossRefGoogle Scholar
- 32.Koller H, Hitzl W, Acosta F, Tauber M, Zenner J, Resch H, Yukawa Y, Meier O, Schmidt R, Mayer M (2009) In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III). Eur Spine J 18(9):1300–1313Google Scholar
- 35.Kristof RA, Kiefer T, Thudium M, Ringel F, Stoffel M, Kovacs A, Mueller C-A (2009) Comparison of ventral corpectomy and plate-screw-instrumented fusion with dorsal laminectomy and rod-screw-instrumented fusion for treatment of at least two vertebral-level spondylotic cervical myelopathy. Eur Spine J 18(12):1951–1956Google Scholar
- 49.Schlenk RP, Stewart T, Benzel EC (2003) The biomechanics of iatrogenic spinal destabilization and implant failure. Neurosurg Focus 15(3):E2Google Scholar
- 53.Sembrano JN, Mehbod AA, Garvey TA, Denis F, Perra JH, Schwender JD, Transfeldt EE, Winter RB, Wroblewski M (2009) A concomitant posterior approach improves fusion rates but not overall reoperation rates in multilevel cervical fusion for spondylosis. J Spinal Disord Tech 22:162–169PubMedCrossRefGoogle Scholar
- 54.Singh K, Vaccaro AR, Kim J, Lorenz EP, Lim TH, An HS (2003) Biomechanical comparison of cervical spine reconstructive techniques after a multilevel corpectomy of the cervical spine. Spine 28:2352–2357, 2358Google Scholar
- 56.Suda K, Kajino T, Moridaira H, Limoto S, Taneichi H (2008) How to avoid fatal vascular complications caused by pedicle screws—surgical strategy for safe screw placement. Spineweek, GenevaGoogle Scholar