RECENT TRENDS IN MANAGEMENT OF POST-LAMINECTOMY LUMBAR INSTABILITY

Abstract

In 1934, Mixter and Barr introduced laminectomy; an operation, which is now being extensively, performed either alone or simultaneously with spinal fusion (Lee CK, 1993). Wide laminectomy of the lumbar spine in which there is partial resection of the

medial one third to one half of the fucet joint is a destructive surgery of the posterior spinal elements. Therefore, it is thought that wide laminectomy tends to result in lumbar instability. (Lida et aL, 1990).

It is inevitable with such maJor surgical procedure to have some failures or unsatisfactory results. A significant incidence rate of post-decompression lumbar instability has been reported- (Lee CK, 1993). Spinal instability is reported to be 3'd most common source of late failures after lumbar decompression (I'' is epidural fibrosis at arachnoiditis and 2"d is recurrence of stenosis at the operated level and/or new stenosis as adjacent levels). It has also been reported to account for 18% to the overall failures (Mark W. Fox eta/, 1996).

The spme is a mechanical structure. The vertebrae articulate with each other in a controlled manner through a complex of levers (vertebrae), pivots (facets & discs), passive restraints (ligaments) and activators (muscles) (wlzite and Panjabi, 1990). The iatrogenic osseous and ligament disruption induced by laminectomy may result in alteration ofthe strength and stability of the vertebral column (Joseph F., eta!, 1995).

Simply, instability is lack of stability, which in mechanical terms means decreased stiffness of the functional spinal unit, increased mobility, or abnormal motions (Boden and Frynwyer, 1997).

Mechanical back pam, which is best, .characterized by exacerbation with activity and relief with bed rest or sitting is the characteristic symptom of instability.