Revision strategies for lumbar pseudarthrosis.
Review
Overview
abstract
Revision surgery for pseudarthrosis remains costly and complicated. Local and systemic factors should be corrected or improved before further surgery is performed. Careful evaluation is mandatory, and patients' expectations should be addressed fully by the surgeon before undertaking any surgical procedure. The single most important factor in achieving a successful clinical outcome in revision spine surgery is patient selection. Pseudarthrosis is still one of the most difficult conditions to assess as a source of symptoms, and not surprisingly the outcome from repair of pseudarthrosis is the most difficult to predict. In evaluation of a solid fusion, the preliminary test includes plain radiographs that include flexion and extension films. More definitive evaluation of pseudarthrosis usually requires CT with two-dimensional and possibly three-dimensional reconstruction. Adjacent levels and the status of neural structures may be evaluated via MRI scanning, discography, and myelography. After determining the presence of pseudarthrosis and ascertaining through clinical examination and evaluation the level of symptomatic pseudarthrosis, operative intervention may be considered once conservative management has failed. Posterior procedures for revision of a failed lumbar fusion have not yielded reliably successful results; however, this approach does have a significant role in the appropriately selected candidate. A combined anteroposterior approach may be more effective in restoring sagittal balance and enhancing fusion rates. The use of posterior instrumentation in light of an anterior pseudarthrosis or anterior support in light of a posterior pseudarthrosis is a viable option for treatment in these circumstances. Several osteoinductive growth factors, referred to as bone morphogenetic proteins, have been shown to induce transformation of undifferentiated mesenchymal cells into chondroblasts and osteoblasts, which results in the formation of de novo bone. Numerous animal studies have demonstrated the superiority of bone morphogenetic proteins over autogenous bone grafts in various orthopedic settings. Bone morphogenetic protein (by itself or in conjunction with autogenous bone) has been shown repeatedly to produce a better quality of spine fusion in a decreased interval of time when compared with the use of autogenous bone alone. These materials, however, remain investigational and currently are not widely used. Prevention of pseudarthrosis is the most successful treatment, although this is not always possible. Appropriate patient selection, surgical techniques, and the use of biologic implants and gene therapy in the near future will make spinal fusion a more predictable procedure to perform. Undoubtedly there is great difficulty in performing satisfactory and statistically verifiable conclusions from the available published studies. Better prospective outcomes studies are needed to improve our knowledge regarding overall patient satisfaction, function, residual pain, and health impact of the treatment of lumbar spine pseudarthrosis.
