Ever wondered how to get rid of that low back pain?Well when HTC get this sim right you know what to do: leave the family for an hour or two ("sorry honey: doc's perscription") and fire up your puter.
*************************
Established in 1812 as the new england journal of medicine and surgery
VOLUME 337 NOVEMBER 6, 1997 NUMBER 19
CORRESPONDENCE
Positive and Negative Gravitational Forces and Herniated-Disk Sciatic Pain
For the Editor: I recently encountered a stunt pilot with an L.4-5 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 Morris' in 1964 found in vivo lumbar in-tradisk 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 hack pain and sciatica due ro 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 demon-strated 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.' Percutaneous laser disk decompression4' is based on reduction of incradisk pressure.
My patient weighed 180 Ib. A reasonable estimate is that at 1 g (normal gravity), approximately 120 Ib would be pressing on his lumbar spine in the erect position. At 5 positive g's, this weight would be increased fivefold, to 600 Ib. 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 excert a pull or tractive force ot 3x 120, or 360 Ib, 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 ot lumbar-spine dynamics.
danih- S.J. chov, M.D.
Laser Spine Center New York, NY 10021
1. Nachemson A. Morris M. In vivo measurements of intradiscal pressure:
discomctry, a method for the determination of pressure in the lower lum-bar discs I Bone loint Surg Am 1964,46:1077-92
2. Jolecz F. Presentation at the annual meeting, LANSI (Laser Association of Neurological Surgeons International), Salzburg, Austria, September 17, 1995.
3. Choy DS). MRI of the lumbar spine under compression. J Clin Laser Med Surg 1997,15:71 3.
4. Case RB, Choy DSJ. Altman MS. Change of intradisc pressure versus volume change ) Clin Laser Med Surg 1995,13:149-52.
5. Choy DSJ Percutaneous laser disc decompression: 11 year experience with 629 procedures in 452 patients. In: Sicberrt W, Knight M, eds. Lasers in orthopedic;.. New York: Springcr-Verlag (in press).
1997, Massachusetts Medical Society
