Osseous reconstruction of complex defects of the lumbar spine.

Sir:

Complex defects of the lumbar spine present significant challenges for the reconstructive surgeon due to the lack of local reconstructive options, the need for immediate postoperative rigidity, and long-term resistance to axial compression forces. With recent studies showing significant improvements in quality of life from operative management of neoplastic disease of the spine, this rare clinical entity is likely to become more common.[1] The growing trend for reconstruction of defects of the axial skeleton is toward vascularized bone grafting (VBG).[2,3] For large, complex defects, a combination of anterior and posterior approaches are required to prevent damage to the great vessels.[4] The literature is unclear whether it is optimal to utilize VBG for the anterior or posterior column reconstruction or both. The aim of this article is to illustrate the important decision-making steps in reconstruction of complex defects of the lumbar spine. An illustrative case is presented, the oncological details of which have been reported elsewhere[5] (Fig. 1).

Fig. 1.

Illustrative case depiction of a 2-stage reconstructive program following extensive lumbar tumor resection with excision of lumbar vertebrae L3–L5 and paraspinous soft tissue. A, Stage 1: posterior approach, posterior instrumentation, bilateral vascularized pedicled 10th rib grafts, and latissimus dorsi turn-over muscle flap to provide vascularized soft-tissue coverage. Stage 2: anterior approach, insertion of an anterior cage for immediate construct rigidity, and free fibular flap reconstruction for long-term stability of the anterior spinal column. The fibula was fixed into the body of L2 superiorly and S1 inferiorly. Microanastomosis was performed end-to-end with branches of the aorta and inferior vena cava. The patient was able to mobilize independently 2 days after both procedures. B, Computed tomography imaging depicting the bone grafts in situ and the anterior and posterior instrumentation at 8 weeks postoperatively.

CHOICE OF DONOR TISSUE AND RECIPIENT VESSELS

Despite theoretical objection to its use in neoplastic settings, VBG is superior to nonvascularized strut grafting as it affords greater stability of the spine from primary bone healing and avoids the pitfalls of nonvascularized bone healing, characterized histologically by creeping substitution. These include high fracture rate, failure of union, prolonged construct settling, pseudoarthrosis, graft resorption, and subsequent neurological deficits.[2] Vascularized bone is also indicated in the context of wide resection of paraspinous soft tissues, multilevel corpectomy, and radiotherapy. Pedicled rib grafts and free fibular flaps have become the mainstays of treatment in spinal reconstruction.[3] Soft-tissue reconstruction in the lumbar region is difficult due to the dense fascial connections to the underlying thoracolumbar fascia and a lack of axial blood vessels. Transposition of the paraspinous musculature as a bipedicled flap may be an option for small defects.[1] Other options include latissimus dorsi turn-over flap, gluteal flap, lumbar perforator flap, and free latissimus dorsi or rectus abdominis flap.

Identification and protection of recipient vessels in the field of tumor extirpation requires considerable communication and cooperation between oncological and reconstructive teams. Reliable options include intercostal vessels, lumbar vessels, common iliac vessels, or segmental branches of the aorta and inferior vena cava.

STAGING OF THE OPERATIVE PROCEDURE

Following spinal tumor resection with radiotherapy, studies have shown improvements in wound-related complications after early reconstruction with vascularized muscle flaps.[1] We suggest that early vascularized reconstruction of the soft tissue and both anterior and posterior columns is likely to provide the most effective reconstruction for complex defects of the lumbar spine. Pedicled rib grafting is most appropriately used as a tension band reconstruction of the absent posterior elements.[2] Free fibular flap transfer is optimal for anterior column reconstruction due to its superior axial strength. In order for optimal access in the lumbar region permitting en bloc vertebral resection, safety of the great vessels and exposition of recipient vessels, a posterior and an anterior approach, or a combined lateral approach are required.[3,4]

CONCLUSION

Complex defects of the lumbar spine are challenging cases which are likely to increase in frequency. Reasoned application of reconstructive principles allied with an understanding of the biomechanics of spinal fixation will equip surgeons with the keys to management of this difficult problem.

ACKNOWLEDGMENT

We thank Veneliza Salcedo from the Mayo Clinic, Rochester, for production of the medical illustration.