~**~ Omentum Transposition ~**~

Omental Transposition In Chronic Spinal Cord Injury

A recent article was published in Spinal Cord titled 'Omental Transposition In Chronic Spinal Cord Injury' (Clifton, G.L. et al, Spinal Cord 34: 193 - 203, 1996). Based on their personal surgical experience the authors concluded that the operation was ineffective with 'no justification for further clinical trials for the procedure in patients who have complete or sensory incomplete lesions'. For the surgical investigators to make such a sweeping statement that would be expected to dissuade other surgeons from evaluating this procedure, it is essential that the experimental design and performance of their surgical trial be precise since these factors would directly reflect subsequent neurologic, neurophysiologic, and statistical verification of the operation.

    Clifton began his interest in using the omentum for spinal cord injuries 1989 by operating on four patients with two being available for long-term follow-up. One of these two patients had 'slight improvement for the first 12 months and then neurologically plateaued'. The second patient developed 'improved truncal control, decreased spasticity, increased sensation beginning at 8 months after surgery and normal at 2 years after surgery'. These findings were sufficiently intriguing for Clifton and his associates to embark in 1992 on a study of 11 patients to determine if omental transposition in spinal cord-injured patients is an effective treatment where evidenced by careful postoperative examinations with associated statistical analysis.

    Patients in the study were neurologically and neurophysiologically evaluated prior to surgery and at 4, 8, and 12 month intervals. The results at one year were to be compared to the patients own preoperative status and to a comparable non-operated group of spinal cord-injured patients. The article in Spinal Cord stated that in order to carry out the study, 11 patients 'underwent transposition of pedicled omentum to the area of spinal cord injury.' Unfortunately this was not accomplished since only five of the 11 patients had a pedicled omentum graft placed on their injured spinal cord while the other six patients, as stated in the paper, had 'free omental grafts taken rather than creating a pedicle for blood supply'. This free graft technique is more technically demanding than simply placing a pedicled omental graft on the spinal cord since the free omental grafts that were fashioned required microsurgical anastomoses of the gastroepiploic artery and vein to the external carotid artery and jugular vein. Creating these free omental grafts markedly changed the surgical trial since this major variation in the operation completely altered the experimental design of the study. A free omental graft is not only more technically difficult to develop than a pedicled graft, but a free graft eliminates one of the major characteristics of the omentum, namely, its enormous edema-absorptive capacity. The loss of this absorption capability is a reflection of a non-functioning omental graft probably because all lymphatic vessels are divided in taking an isolated piece of omentum and making it into a free graft. Such a critical loss of omental function may well be seen in three of Clifton's 11 patients who 'developed persistent CSF accumulations 4-8 months after surgery, with all requiring lumbo-peritoneal shunts 8 months after surgery for their problem. Performance of these L-P shunts further changed the experimental design of this surgical trial and must bring into question any critical evaluation of the effectiveness of the omental transposition of a pedicled omentum to an injured spinal cord as measured by the statistical analysis of the neurological results.

    Although Clifton's paper is long and detailed, its soundness as a scientific study is open to question. For example, it was stated that all 11 patients had an MRI at 12 months but only nine of the 11 were found to have had their omentum in contact with the dorsum of their spinal cord. One of the two patients without omental-spinal cord adherence had to have his omental graft removed 6 months after surgery at which time it 'was not found to be anatomically connected to the cord'. How could two of 11 patients (18%) in which the omentum was being evaluated for its effect on the spinal cord be studied neurologically and neurophysiologically as determinates in a group evaluation for statistical purposes one year after surgery, when the omentum was not even adjacent to the spinal cord? What would be the significance of ASIA neurological scores, MRI's, SEPS, etc. when there are such major flaws in the surgical design and performance of the study.

    Clifton and his associates are to be congratulated for searching for new procedures to help patients with spinal cord injuries since there has always been a tendency in medicine to question new ideas and techniques. The purpose of their surgical study was to learn the effectiveness of omental transposition in patients with chronic spinal cord injury using precise neurological and neurophysiological examinations with results being confirmed by sophisticated statistical analysis. Such a careful study is needed since the procedure is being performed in several countries with more than 3000 cases of omental transposition to the injured spinal cord in humans being reported from China alone.¹

    Clifton's study would be expected to reflect directly the manner in which the experimental design of the operation was carried out and the technical manner in which it was performed. He and his colleagues have reported negative clinical results which support their personal hesitation to perform additional omental operations on patients with chronic spinal cord injury. However, it is unreasonable for them to recommend to other spinal cord investigators, that based on their surgical endeavors, there be 'no further clinical trials'.

References

1 Goldsmith, HS, First International Congress on Omentum
    to the CNS. Surg. Neurol. 45: 87 - 90, 1996.

Reply from Dr Guy L. Clifton

Dr Goldsmith's argument is that the surgical procedure was flawed, not the methodology of assessing it's effect. Omental Transposition is a major procedure with major risk. Our conclusion was that further clinical trials in complete and sensory incomplete patients was not justified without compelling new laboratory data.

    We did not conclude that there should be a moratorium on further clinical trials in motor incomplete patients. We had no data to make such a statement on motor incomplete patients. If the procedure should be effective for complete or sensory incomplete patients and since it is being widely performed, then data contradicting ours should be put forward using the same methodology.

    If clinical data refuting our conclusion does not exist after the length of time the procedure has been in use then compelling animal studies should be done before any more complete or sensory incomplete patients are subjected to this procedure in our opinion. In its absence, we see no reason to alter our conclusion.

Dr Guy L. Clifton, M.D.,
Department of Neurosurgery, University of Texas,
Houston Medical School,
6431 FANNIN, Suite 7.149,
Houston, Texas 77030, U.S.A.