Traditional scoliosis surgery has undergone “innovations” through the decades, however, possibly none more profound than the introduction of spinal instrumentation by Paul Harrington in the 1960s. The iterative changes in his original technique for the correction of scoliosis have been focused on gaining improvement in the outcomes of the surgery, e.g., greater correction, increased construct stability, more predictable fusion, and less morbid surgical approaches. The three papers presented in this section explored new methods for reducing the surgical morbidity and improving the outcome with scoliosis correction.
Spinal fusion procedures, particularly those involving multiple segments, as in scoliosis, remain one of the operations with the greatest potential for blood loss performed in orthopedic and neurosurgical practices. There are several reasons to attempt to minimize operative/perioperative bleeding, and Thompson et al have presented a summary of a series of studies they have performed to evaluate the effects of the antifibrinolytic agent Amicar. They have suggested that the administration of Amicar reduces the need for autologous predonation as well as the risk of exposure to allogenic blood in adolescent idiopathic scoliosis patients. The drug is inexpensive and appears to have a very safe usage profile. The results, however, generate a number of as yet unanswered questions: Which patients other than those with adolescent idiopathic scoliosis might benefit from this treatment? Intraoperative blood loss can be life-threatening in the neuromuscular and complex revision patients, making any potential effect of Amicar of even greater significance in these patients. How does Amicar compare with Aprotinin with regards to both efficacy and safety? The efficacy of aprotinin has been demonstrated in neuromuscular scoliosis by Cole et al1; however, the cost of this drug is substantially more than Amicar.
What are the indications for each of these medications, and are the indications different? It is not unreasonable to think that these two pharmacologic means of reducing blood loss will have different cost/benefit ratios resulting in independent indications for their use. A prospective comparison of all types of spinal deformity surgery with both agents will be useful and is being initiated.
Attempting to reduce “approach related” morbidity, Newton et al reported on a minimally invasive thoracoscopic technique of scoliosis correction. Open approaches, either anteriorly or posteriorly, involve substantial muscle dissection with albeit variably documented associated “morbidity.” Thoracotomy approaches reduce pulmonary function with a small but measurable long-term deficit (approximately 10% of predicted values). Impairment of muscle function, particularly in the paraspinous muscles, is of unclear long-term consequence, given the outcome of thoracic posterior instrumentations performed over 40 years ago, many with excellent results. It may be that minimally invasive only means minimal incisions (i.e., smaller scars), as the length of the hospitalization for the thoracoscopic anterior spinal fusion is the same as that reported for open thoracotomy. Although cosmesis is important to scoliosis patients, it is secondary to the risk of neurologic injury and the need for a second procedure.2 Thus, “innovative” techniques must not sacrifice these first two patient-driven priorities. Although Newton et al have demonstrated outcomes comparable to historical literature controls of open anterior thoracic scoliosis correction, they have raised the question of whether this approach should be universally adopted as an option for scoliosis correction. As in the development of any new technology, a prospective comparison to both open anterior and posterior procedures is required. Even if this approach is proven to have some advantage in particular cases, the “cost” of each adopting surgeon’s learning curve must be factored into the analysis.
As long as instrumented fusion remains the mainstay of scoliosis surgery, no matter the surgical approach or associated blood loss, one of the primary goals is achieving a fusion. A much greater challenge in the adult deformity population, Bridwell et al report their early experience with a possible recombinant biologic solution. Obviating or reducing the need for autogenous bone graft and/or reducing the risk of pseudarthrosis has great potential to reduce the morbidity of scoliosis surgery. In some cases, this may limit the need for autologous rib or ilium harvest, while in others the autogenous sources may have been already used without further sources available due to prior procedures. The outcomes of BMP-2 use in both the anterior and posterior aspects of the spine have been critically evaluated with little apparent down-side effects. The multiple level anterior column fusions mirrored prior one-level studies with high radiographic rates of arthrodesis. The results of off-label posterior use of BMP-2 at multiple levels is more complex an issue to fully assess. The posterior usage in this series clearly resulted in bone/fusion mass formation that in at least several cases (when no additional bone was added) could only be attributable to the BMP that was used. The true state of the arthrodesis, posteriorly, is more difficult to evaluate. Confirming a solid posterior arthrodesis radiographically (even with thin sliced CT scanning) is challenging and not completely reliable. Several additional years of follow-up will be required to ensure that a solid arthrodesis has developed. In which patients will the cost/benefit analysis truly favor BMP use over autograft or some other allogenic or synthetic bone graft substitute? Almost certainly if the use of BMP can reduce the pseudarthrosis rate, it will be cost-effective. Assessment of cost/benefit ratios is very complex and must take into account long-term considerations, such as time lost for work, need for revision surgery, etc., which are often not considered in cost/benefit analyses.
Innovation takes time, and these three papers represent years of development and investigation. Even so, they seem to be generating as many questions as they have been able to answer. Much more work is required before widespread adoption of these methods. Only after careful prospective (blinded when possible) comparisons will we know if these new approaches to our spinal deformity problems actually represent “innovations.”
1.Cole JW, Murray DJ, Snider RJ, et al. Aprotinin reduces blood loss during spinal surgery in children. Spine
2.Bunch WH, Chapman RG. Patient preferences in surgery for scoliosis. J Bone Joint Surg Am