David Kubosch, Stefan Milz, Christian Lohrmann, Karsten Schwieger, Lukas Konstantinidis, Christoph M. Sprecher, Norbert P. Südkamp, Peter C. Strohm


September 2011, Volume 20, Issue 10, pp 1644 - 1649 Original Article Read Full Article 10.1007/s00586-011-1895-2

First Online: 12 July 2011

Study design

Retrospective clinical study in patients with dorso-ventral thoraco-lumbar spondylodesis.

Objective

To investigate whether the ratio between graft cross sectional area and the surface area of the adjacent endplates has any effect on the midterm stability of the spondylodesis.

Summary of background data

Dorso-ventral spondylodesis in the region of the thoraco-lumbar spine is one of the most frequent operations in orthopaedic surgery. Anterior stabilization with autologous iliac crest graft currently is a standard approach in many hospitals. Although numerous recommendations are given how to perform this technique, no clinical advice is available with regard to minimum graft size.

Methods

Sixty-four-slice CT-scans were obtained from 82 patients 4–12 months after posterior spondylodesis with anterior implantation of iliac crest graft and stabilization with an internal fixator. The scans were analyzed using image analysis software. First, the cross sectional area of the graft was calculated and then the surface area of the adjacent endplates. The ratio between graft cross sectional area and endplate surface area was then calculated from these two values. The grafts were then evaluated in sagittal reconstruction for signs of fracture.

Results

The probability for graft fracture in autologous tricortical grafts was >0.1% (p < 0.001) if the graft cross sectional area exceeded 23.9% of the surface area of the adjacent endplates. Patients with lower ratio values had a higher fracture risk and below a value of 10% all grafts fractured.

Conclusion

The relationship between graft cross sectional area and adjacent endplate area has an important effect on graft midterm stability in ventral spondylodesis of the thoraco-lumbar spine. In our opinion, the risk of graft fractures in dorso-ventral spondylodesis can be reduced by implantation of an appropriately sized graft without any additional procedures or instrumentation.


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