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Alastair
06-06-2006, 02:16 AM
Strategies for revision

When faced with a failure of the implants, timing is of paramount importance in terms of the relationship to the date of the initial surgery. If it is within two to three weeks, the approach is relatively easy, as the early wound healing frequently does not prohibit going in through the same plane. From three weeks to six months is most difficult, as the tissue is friable and can be densely adherent at the same time. Retroperitoneal fibrosis around the great vessels and ureters represents a formidable technical challenge. Beyond six months it is still difficult, but not as treacherous as the intermediate period.

If there is no neural entrapment and no vascular impingement, posterior fusion in situ is a reasonable safe option, and if the timing is early, revision of the device can also be considered.

When there is neural entrapment, if this can be correctible posteriorly, this is preferable for safety reasons. Depending on the timing of the problem's occurrence, anterior revision is another option, if postoperatively early enough, and depends on the source of the neural compression.

With vascular impingement revision or removal of the implant must always be considered. If there is coronal malalignment, I personally prefer posterior reduction and subsequent anterior removal and fusion. With coronal malposition, the segment may have lost its intrinsic stability, and is therefore too unstable to revise. If there is only sagittal malalignment, then revision or fusion anteriorly done with anterior plate can be considered, or subsequent posterior pedicle fixation if a fusion is desired. Posterior fusion with subsequent anterior fusion is also a viable option.

As discussed by Dr. Bailey, if there is expulsion anteriorward, it is helpful to know as best as possible where the vein is and whether the vein is compressed. Venogram and ultrasound can be helpful in this regard.

Since we do not have good data on long-term follow-up on these cases and know some instances of expulsion and failure occur, a prophylactic approach would make sense. We use a tight-weave vascular tubular graft or a large enough piece to be folded over so that there are two layers of graft, one opposite the great vessels, one opposite the disc operative site, extending at least halfway up the vertebral bodies, cephalad and caudad. These are anchored into position to the prevertebral fascia. If revision has to occur in the future, dissection can safely be done between the layers of graft material, and the posterior layer can easily and safely be cut to expose the interspace, while the anterior vascular graft layer can be used to shield the vessels and facilitate retraction.

Susan Bailey MD Vascular Surgeon
James Zucherman Orthopedic Spine Surgeon
yaquai@aol.com
St, Mary's Spine Center #450
San Francisco, CA 94117
415-750-5825
415-750-8103 (fax)