Acta Orthopaedica 2009; 80 (4): 445–450 the differences cannot be explained by the non-instrumented group being exceptionally poor. The randomized studies comparing fusion with and with- out additional pedicle screw fixation have mainly been per- formed in patient samples with an average age well below that of this series. One exception is the study by Fischgrund et al. (1997) in which the average ages in the instrumented and non- instrumented groups were 69 and 66 years, respectively. In the original study there was a statistically significant difference in fusion rates, but not in patient-assessed outcome. In a later long-term follow-up on this study, Kornblum et al. (2004) compared patients with solid arthrodesis to those with pseudo- arthrosis and could demonstrate better outcome in those who were solid-fused. They interpreted this in favor of instrumen- tation, although the study involved a smaller patient material than the original and the data were not analyzed according to the original assigned treatment groups. In a cohort study com- paring laminectomy alone to laminectomy with non-instru- mented or instrumented fusion, Katz et al. (1997) could not demonstrate any beneficial effect of instrumentation (relative to non-instrumented fusion) in patients older than 50 years. We observed the same tendency of better outcome in those patients who achieved a solid fusion as did Kornblum et al. We did, however, only use plain radiographs for fusion assess- ment; thus, it is likely that the fusion rate is overestimated—as it has been shown to be reduced by the use of more detailed diagnostic modalities (Brodsky et al. 1991). However, the uncertainty in determining fusion rate does not affect our main observation, which was the difference in functional out- come between the two groups. Other documentation for any relation between outcome and achievment of solid fusion has been somewhat controversial. In a meta-analysis, Mardjetko et al. (1994) could not demonstrate any relationship between fusion rates and patient satisfaction. In a historical study on pedicle screw fixation, Yuan et al. (1994) found higher fusion rates and better outcomes in patients fused with pedicle screw instrumentation than in patients with uninstrumented fusions. What argued against the use of instrumentation was the higher number of additional spine surgeries in this group, as additional spine surgery after the primary procedure was asso- ciated with poorer outcome. Several studies have investigated the rate of complications associated with spinal surgery in this age group (Deyo et al. 1992, Carreon et al. 2003, Ragab et al. 2003, Cassinelli et al. 2007), but few have related the presence of complications or additional surgeries to functional outcome. In the Maine lumbar spine study, additional spine surgery over an 8–10-year follow-up period was associated with smaller improvement and less satisfaction as compared to those who had only undergone the primary intervention, which, however, rarely involved fusion but only decompression (Atlas et al. 2005). Tokuhashi et al. (2008) reported a high degree of inde- pendence 10 years after instrumented fusion in patients over 70 years. They did not, however, report on the influence of complications on outcome. In a study similar to ours, Glass- 449 man et al. (2007) reported inferior results in patients older than 65 years who required revision surgery after a primary lumbar fusion, as compared to patients only operated once. Despite the higher number of additional spinal surgeries in the instrumented group, outcome was still better than in the non-instrumented group. Thus, the poorer results associated with additional surgery could not outweigh the better outcome achieved in the instrumented group in general. One study investigating the long-term results of decompres- sive surgery has shown a deterioration in improvement with time (Jonsson et al. 1997). In fusion surgery, the stability of the improvement in outcome achieved has varied between studies (Ekman et al. 2005, Andersen et al. 2008). In the current study, the improvement in both groups was stable and the long-term effect of the fusion procedure appears to be preserved also in this patient category. In summary, we have found that superior outcomes can be achieved in selected patients over 60 years of age who have been treated with instrumented spinal fusion using allograft, as compared to non-instrumented fusion. The study suggests that the achievement of a solid fusion was one of the explanatory factors for this finding. However, pedicle screw instrumenta- tion was associated with a larger number of additional surger- ies, which resulted in inferior outcomes. Thus, the selection of procedure for the older patient requiring spinal fusion remains a balancing act, but instrumentation should not be discarded just because of the age of the patient. Future research should concentrate on determining the most efficient fusion proce- dure in elderly patients. All authors contributed to the planning of the study, interpretation of results, and editing of the manuscript. TA and FBC performed data analysis and wrote the manuscript. BN, PH, KH, and ESH collected the data and assessed the radiographs. CB initiated the study and provided funding. An H S, Lynch K, Toth J. Prospective comparison of autograft vs. allograft for adult posterolateral lumbar spine fusion: differences among freeze-dried, frozen, and mixed grafts. J Spinal Disord 1995; 8: 131-5. 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