Commentary & Perspective on
"Failure of External Spinal Skeletal Fixation to Improve Predictability of Lumbar Arthrodesis"
By Drew A. Bednar, MD

Commentary & Perspective by
Charles R. Clark, MD*, Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA

External spinal skeletal fixation was originally developed to treat unstable spinal injuries and spinal osteomyelitis¹. More recently, this technique has been used to evaluate patients with back pain as possible candidates for surgical arthrodesis. In this application, skeletal fixation pins are inserted in segments of the lumbar spine, and those patients who subsequently experience pain relief are considered for surgical stabilization. Indeed, such an approach seems intuitive.

Axelsson et al.² conducted a roentgenogram stereophotogrammetric analysis of patients who had application of the external fixator and found that, with the external fixation-frame fixed, sagittal intervertebral translations were significantly reduced. They concluded that the properties of the external fixator provided an adequate mechanical basis so that the external fixation test could be used to predict the success of lumbar fusion. Further, Jeanneret et al.³ evaluated a group of 101 patients with disabling low-back pain in whom diagnostic external fixation was performed and concluded that positive results with external skeletal fixation may predict a successful arthrodesis with reasonable accuracy. Conversely, they pointed out that if stabilization did not relieve the patient's pain, surgical fusion was unlikely to be of benefit.

Esses et al.⁴ prospectively studied thirty-five patients with chronic low-back pain and showed that the result of temporary external spinal fixation was significantly superior as a predictor of the result of surgical fusion when compared with plain radiographs, discograms, and facet blocks. In 1996⁵, Bednar, the author of this current report, and Raducan reported a prospective, randomized clinical trial evaluating the prognostic benefit of external spinal skeletal fixation. In patients with mechanical back pain, these authors found that surgical fusion resulted in pain relief for only 61% (19 of 31) of the control group (without fixation) versus 90% (19 of 21) of the study group (with fixation).

In the current report, Bednar reviews the records of more than 100 patients in whom external fixation was performed as a prelude to proposed lumbar arthrodesis. He reports that neurological complications occurred in two procedures, infections occurred in five patients, and of sixty patients who experienced pain relief during the fixation test, only twenty-seven of the forty-nine who underwent arthrodesis were found to be doing well at a minimum follow-up of one year. Following this analysis, he concluded that external spinal skeletal fixation should not be used as a predictor of pain relief after lumbar arthrodesis.

I agree with Dr. Bednar that the problem does seem to be more one of ‘whom to fuse’ rather than ‘how to fuse.’ Dr. Bednar is to be applauded for his integrity in discontinuing a test that he had performed on a regular basis after he realized that the patients were not doing as well as he had hoped. One could hardly argue that pain relief in only twenty-seven of forty-nine patients who had had a positive response to the test and then had undergone arthrodesis is less than ideal.

The management of mechanical low-back pain is a difficult problem. Despite the more favorable outcomes of this technique reported by others, I believe that this current report by Dr. Bednar points out the continuing problem of proper patient selection for surgical stabilization. External spinal skeletal fixation may have a role as a predictor of which patients might benefit from subsequent lumbar arthrodesis, but its role, particularly on the basis of Dr. Bednar's findings, appears to be quite limited. Unfortunately, many of the other diagnostic and/or prognostic tools for predicting who may do well with arthrodesis in this setting are also less than perfect. Once again, the overall clinical judgment of the spine surgeon is of paramount importance in deciding who might benefit from a particular procedure.

*In support of his research or preparation of this manuscript, the author received grants or outside funding from The Journal of Bone and Joint Surgery. The authors did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Magerl FP. Stabilization of the lower thoracic and lumbar spine with external skeletal fixation. Clin Orthop. 1984;189:125-41.
2. Axelsson P, Johnsson R, Stromqvist B. Mechanics of the external fixation test in the lumbar spine. A roentgen stereophotogrammetric analysis. Spine. 1996;21:330-3.
3. Jeanneret B, Jovanovic M, Magerl F. Percutaneous diagnostic stabilization for low back pain. Correlation with results after fusion operations. Clin Orthop. 1994;304:130-8.
4. Esses SI, Botsford DJ, Kostuik JP. The role of external spinal skeletal fixation in the assessment of low-back disorders. Spine. 1989;14:594-601.
5. Bednar DA, Raducan V. External spinal skeletal fixation in the management of back pain. Clin Orthop. 1996;322:131-9.