Abstract: To the Editor: Re: Mardjetko S, Albert T, Andersson G, et al. Spine/SRS Spondylolisthesis Summary Statement. Spine 2005;30:S3. We read this article with great interest. However, we would like to question the summary statement: “Reduction should be given strong consideration in pediatric patients with high-grade developmental spondylolisthesis and significant lumbosacral kyphosis.” There are no randomized controlled trials comparing outcomes of reduction versus in situ fusion in high-grade developmental spondylolisthesis. To the authors' knowledge, no other study has thus far shown that clinical outcome would be better after reduction than in situ fusion of pediatric high-grade spondylolisthesis.1,2 In contrast, our retrospective comparative, matched, long-term study (after a mean follow-up of 14.5 years in both groups) suggested that clinical outcome (i.e., Oswestry Disability Index, Scoliosis Research Society [SRS] total score, back and leg pain on visual analogue scale) was statistically significantly worse after reduction compared to circumferential in situ fusion for high-grade isthmic spondylolisthesis in adolescents.3 SRS cosmetic questions did not differ between study groups. The radiographic and magnetic resonance imaging outcomes (slip, lumbosacral kyphosis, nerve root stenosis) were somewhat better in the reduction group, but disc degeneration was significantly more common in the reduction group. Our study group recently compared clinical and radiographic outcomes of posterolateral, anterior, and circumferential fusion without instrumentation in situ for high-grade spondylolisthesis in children and adolescents.4 After a mean follow-up 17.2 of years, the 26 patients in the circumferential fusion group did best for most outcome parameters. Most patients were totally pain free (mean Oswestry Disability Index 3.0) and were extremely satisfied with their back treatment (mean SRS 24 total score 100.0 points). Pseudarthrosis developed in only one patient in that group. The reasons for worse outcomes with reduction than with in situ fusion are still obscure. Reduction is always potentially dangerous. According to the 2003 Mortality and Morbidity report of the SRS,5 there has been an increase in the percentage of lytic spondylolisthesis undergoing reduction from 22% to 44% during 1996−2002. The incidence of neurologic complications with lytic spondylolisthesis surgery has increased from 1.3% to 3.1% during the reporting period. Using a cadaver model, Petraco et al6 has shown large increases in L5 nerve root tension, with reductions higher than 50% of the width of the L5 vertebral body. The posterior approach for instrumentation and reduction is much wider than the Wiltse paraspinal muscle split approach for posterolateral fusions.3 Residual deformity appears to improve even after solid in situ fusion because bone remodeling occurs, and muscle spasms and tight hamstrings improve.7 Cauda equinae syndrome has been described after posterolateral in situ fusion for high-grade spondylolisthesis.8 In our recent long-term clinical and magnetic resonance imaging study,3 there were no signs of central lumbar spinal stenosis after in situ fusion. However, all our patients had isthmic defect of the pars interarticularis, and we do advocate decompression of the cauda equinae in patients with true dysplastic (elongated and intact posterior arch) high-grade spondylolisthesis. Concerning the aforementioned excellent clinical results and high fusion rate after noninstrumented circumferential fusion, it remains unclear if the use of transpedicular instrumentation or intercorporeal devices could improve these results. Molinari et al9 compared 3 different treatment options for this condition: 1) posterolateral fusion in situ without instrumentation, 2) reduction with posterior instrumented fusion, and 3) reduction with instrumented circumferential fusion. In their study, circumferential instrumented fusion gave the lowest pseudarthrosis rate, but functional outcomes did not differ among the 3 groups studied. The lower pseudarthrosis rate is more likely to be related to the circumferential fusion than to instrumentation. Thus, instrumentation should be reserved for very special cases, and the gold standard for pediatric high-grade spondylolisthesis should be noninstrumented circumferential in situ fusion. Ilkka Helenius, MD, PhD Hospital for Children and Adolescents Helsinki University Central Hospital and ORTON Orthopaedic Hospital Ville Remes, MD, PhD Surgical Hospital Helsinki University Central Hospital and ORTON Orthopaedic Hospital Mikko Poussa, MD, PhD ORTON Orthopaedic Hospital Helsinki, Finland