Literature Review
Pathology
Isthmic spondylolisthesis develops from defects in the pars interarticularis during adolesence. Many people do not have symptoms and are unaware of the diagnosis. However, isthmic spondylolisthesis can become symptomatic with the development of normal degenerative changes. What can cause leg pain?

21 patients with pain in one leg were reviewed with MRI scan to determine the cause of the leg pain. (#16) All patients had isthmic lumbar spondylolisthesis and no other explanation for the leg pain other than the spondylolisthesis. 18 of the patients revelaed that the exiting nerve was compressed as it exits the spine (foraminal stenosis) and 20 of 21 exhibited disc protrusion (the disc is uncovered as the upper vertebra slips foward on the lower vertebra). (#16) Foraminal stenosis develops with time and can compress the spinal nerve and produce leg pain.

Perhaps activation of the degenerative disc process at the site of the isthmic spondylolisthesis accounts for most accounts of the development of symptoms as people get older (30's, 40's, 50's). But what about progression of the slipping of the vertebra?

Approximately, 20% of individuals with isthmic spondylolisthesis will develop symptoms as an adult due to slip progression according to these studies. (#3, #17)

Other authors have reviewed patients with isthmic spondylolisthesis diagnosed before they were 20 years old and observed for an average of 15 years. (#8) This group found that the risk of further slipping of the vertebra was low but the incidence of disc degeneration at the level of the spondylolisthesis was high. (#8)

Conservative Treatment versus Surgery
A recent study compared patients with isthmic spondylolisthesis and the following criteria: minimum 1 year of back or leg pain, ages 18 to 55, severe functional limitation. (#2)

In adult patients with long-standing symptoms from isthmic spondylolisthesis, the surgical results were superior to the non-surgical exercise only group. (#2)

Surgery
In adults with isthmic spondylolisthesis, surgical concepts have included decompression and fusion. (#1, #4, #5, #7, #9, #10, #11, #12, #13, #14, #15) Decompression involves the uncovering of nerve stuctures under pressure and fusion involves uniting the bones together to stop motion in the segment with the isthmic spondylolisthesis (achieve stability). The controversies are listed in the table below:

Complications
The complications involved in surgery for isthmic spondylolisthesis are related to the exact nature of the surgery chosen: complications of surgical approach for anterior or posterior surgery; complications of fusion with. harvesting of bone or failure to fuse; complications of decompression involving the spinal nerves; complications of instrumentation which involves the insertion and maintenance of hardware in the human body; complications of closure; medical complications and anethetic complications and finally the complications associated with lying on an operating table and subsequent post operative course

Author’s Comment
Most patients undergoing surgery in the adult years for isthmic spondylolisthesis have had the structural defect for years. Superimposed degenerative changes can produce back pain or leg pain or both. Analysis of the abnormal anatomy and the components causing the patients symptoms may lead a surgeon to a particular choice among the many options listed above.

References
1. Moller, H. and R. Hedlund, Instrumented and noninstrumented posterolateral fusion in adult spondylolisthesis--a prospective randomized study: part 2. Spine, 2000. 25(13): p. 1716-21.
2. Moller, H. and R. Hedlund, Surgery versus conservative management in adult isthmic spondylolisthesis--a prospective randomized study: part 1. Spine, 2000. 25(13): p. 1711-5.
3. Floman, Y., Progression of lumbosacral isthmic spondylolisthesis in adults. Spine, 2000. 25(3): p. 342-7.
4. Nooraie, H., A. Ensafdaran, and M.M. Arasteh, Surgical management of low-grade lytic spondylolisthesis with C-D instrumentation in adult patients. Arch Orthop Trauma Surg, 1999. 119(5-6): p. 337-9.
5. Kim, N.H. and J.W. Lee, Anterior interbody fusion versus posterolateral fusion with transpedicular fixation for isthmic spondylolisthesis in adults. A comparison of clinical results. Spine, 1999. 24(8): p. 812-6; discussion 817.
6. Ishida, Y., et al., Delayed vertebral slip and adjacent disc degeneration with an isthmic defect of the fifth lumbar vertebra. J Bone Joint Surg Br, 1999. 81(2): p. 240-4.
7. Deguchi, M., A.J. Rapoff, and T.A. Zdeblick, Posterolateral fusion for isthmic spondylolisthesis in adults: analysis of fusion rate and clinical results. J Spinal Disord, 1998. 11(6): p. 459-64.
8. Seitsalo, S., et al., Disc degeneration in young patients with isthmic spondylolisthesis treated operatively or conservatively: a long-term follow-up. Eur Spine J, 1997. 6(6): p. 393-7.
9. Carragee, E.J., Single-level posterolateral arthrodesis, with or without posterior decompression, for the treatment of isthmic spondylolisthesis in adults. A prospective, randomized study. J Bone Joint Surg Am, 1997. 79(8): p. 1175-80.
10. Thalgott, J.S., et al., Adult spondylolisthesis treated with posterolateral lumbar fusion and pedicular instrumentation with AO DC plates. J Spinal Disord, 1997. 10(3): p. 204-8.
11. Schnee, C.L., A. Freese, and L.V. Ansell, Outcome analysis for adults with spondylolisthesis treated with posterolateral fusion and transpedicular screw fixation. J Neurosurg, 1997. 86(1): p. 56-63.
12. Rijk, P.C., et al., Spondylolisthesis with sciatica. Magnetic resonance findings and chemonucleolysis. Clin Orthop, 1996(326): p. 146-52.
13. de Loubresse, C.G., et al., Posterolateral fusion for radicular pain in isthmic spondylolisthesis. Clin Orthop, 1996(323): p. 194-201.
14. Christensen, F.B., et al., Radiological and functional outcome after anterior lumbar interbody spinal fusion. Eur Spine J, 1996. 5(5): p. 293-8.
15. Ricciardi, J.E., et al., Transpedicular fixation for the treatment of isthmic spondylolisthesis in adults. Spine, 1995. 20(17): p. 1917-22.
16. Deutman, R., et al., Isthmic lumbar spondylolisthesis with sciatica: the role of the disc. Eur Spine J, 1995. 4(3): p. 136-8.
17. Seitsalo, S.e.a., Progression of spondylolisthesis in children and adolescents: A long-term follow-up of 272 patients. Spine, 1991. 16: p. 417-421.