Correspondence
Positive and Negative Gravitational Forces and Herniated-Disk Sciatic Pain
N Engl J Med 1997; 337:1396-1398November 6, 1997
- Article
To the Editor:
I recently encountered a stunt pilot with an L4–5 herniated disk, documented by magnetic resonance imaging (MRI), who had sciatic pain and experienced exacerbation of symptoms when pulling out of a sharp dive, at which point his body was subjected to up to 5 g's. The pilot empirically found he could alleviate this pain by climbing to 10,000 ft and performing an outside loop, experiencing as much as -3 g's. These experiences were repetitively duplicated in the course of his profession, which was performing aerobatics in high-performance fighter planes at military and civilian air shows.
The physiology underlying these phenomena is simple. Nachemson and Morris1 in 1964 found in vivo lumbar intradisk pressures to average 50 kPa in the supine position, 100 kPa in the standing position, and up to 200 kPa in the sitting position. Physicians experienced in treating low back pain and sciatica due to herniated-disk disease are familiar with the usual complaint of worsening pain when patients are seated and variable relief of pain when they assume the supine position. Indeed, Jolecz2 has demonstrated increased disk protrusion when patients are imaged in the sitting position. As of this writing, there are only two “sitting” MRI facilities available: one at Harvard and the other in Zurich. Recently, I reported increased disk protrusion when patients were imaged by MRI while the lumbar spine was compressed in an all-wood compression frame.3 A recent treatment for herniated-disk pain consists of prolonged and extreme traction, with demonstrable reduction of intradisk pressure.3 Percutaneous laser disk decompression4,5 is based on reduction of intradisk pressure.
My patient weighed 180 lb. A reasonable estimate is that at 1 g (normal gravity), approximately 120 lb would be pressing on his lumbar spine in the erect position. At 5 positive g's, this weight would be increased fivefold, to 600 lb. This would be expected to increase intradisk pressure, thus exacerbating any preexisting herniation. The -3 g's that would be encountered in an outside loop would exert a pull or tractive force of 3×120, or 360 lb, on the lumbar spine, reducing intradisk pressure.
It is interesting that the patient reported exacerbation of sciatic pain with positive g's and relief with negative g's, and that he discovered these relations empirically, without the benefit of sophisticated knowledge of lumbar-spine dynamics.
5 ReferencesDaniel S.J. Choy, M.D.
Laser Spine Center, New York, NY 100211
Nachemson A ,Morris M . In vivo measurements of intradiscal pressure: discometry, a method for the determination of pressure in the lower lumbar discs. J Bone Joint Surg Am 1964;46:1077-1092
Web of Science | Medline2
Jolecz F. Presentation at the annual meeting, LANSI (Laser Association of Neurological Surgeons International), Salzburg, Austria, September 17, 1995.
3
Choy DSJ . MRI of the lumbar spine under compression. J Clin Laser Med Surg 1997;15:71-73
Medline4
Case RB ,Choy DSJ ,Altman MS . Change of intradisc pressure versus volume change. J Clin Laser Med Surg 1995;13:149-152
Medline5
Choy DSJ. Percutaneous laser disc decompression: 11 year experience with 629 procedures in 452 patients. In: Siebert W, Knight M, eds. Lasers in orthopedics. New York: Springer-Verlag (in press).
- Citing Articles (4)
Citing Articles
1
(2007) Letter to the Editor. Photomedicine and Laser Surgery 25:3, 235-236
CrossRef2
Daniel S.J. Choy. (2004) Percutaneous Laser Disc Decompression: An Update. Photomedicine and Laser Surgery 22:5, 393-406
CrossRef3
Daniel S.J. Choy. (2004) Percutaneous Laser Disc Decompression: A 17-Year Experience. Photomedicine and Laser Surgery 22:5, 407-410
CrossRef4
Daniel S.J. Choy. (2002) Editorial Comment. Journal of Clinical Laser Medicine <html_ent glyph="@amp;" ascii="&"/> Surgery 20:1, 15-15
CrossRef
