Purpose of the study: Posterior lumbar interbody fusion (PLIF) as described by Cloward, with laminectomy of the entire separate neural arch in spondylolisthesis, is a difficult operation. The purpose of this study is to evaluate the results of PLIF with autologous bony graft, without reduction or instrumentation in grade I and II spondylolisthesis.
Material: The authors report the results of a series of 36 cases of spondylolisthesis (out of a series of 160 cases) operated on with PLIF, after a minimum of 10 years of follow-up (mean: 11.8 years, 10-16 years). 9 patients were lost for follow-up, 27 had been examined clinically and radiologically. 19 males and 8 females. Mean age 29.6 years (14 to 50). The series consisted in 24 lumbo-sacral disc and 3 L4-L5 disc fusion. Before operation, 25 patients suffered backache and 20 had sciatic. Mean preoperative listhesis according to Boxall was 29 per cent.
Methods: PLIF had been done with autologous bony graft and neural decompression without reduction. The thickness of the space had been restored with special progressive distractor. Postoperative back cast was used during 6 months.
Results: Postoperative nerve roots complications occurred in 4 cases and were regressive within 3 months. Results were excellent in 17 cases, good in 7 cases and poor in 3 cases. Patients returned to work after 9.8 months (13.6 months for heavy work). 26 patients had solid tomographic interbody fusions. No additional subluxation was noted. In 10 per cent of the cases the graft was partially crammed. In 7 cases a degenerative aspect of the upper disc was noted (symptomatic in 6 cases). The sagittal balance of the spine evaluated with a specific index showed persistent abnormality in 50 per cent of the cases but PLIF brought a significant improvement in 26 per cent.
Discussion: The rate of fusion is better than in series using bony allografts and better than in series using anterior interbody fusion. The analysis of the adjacent discs shows that it is not necessary to extend fusion to the upper disc. Instrumentation had not been used in this series but a cast seems to be indispensable. Instrumentation with plates and pedicular screws should be able to give more stability but is often responsible of iatrogenic lesions at the articular facets.
Conclusion: This study confirms the good results obtained by PLIF with nerve roots decompression in spondylolisthesis. Fusion is stable and does not accelerate degenerative lesion of the upper disc.