RESULTS OF POSTERIOR LUMBAR INTERBODY FUS ION IN THE TREATMENT OF SPONDYLOLISTHESIS (27 CASES - 10 TO 16 YEAR FOLLOW-UP)

Purpose of the study Posterior lumbar interbody fusion (PLIF) as descr ibed by Cloward, with laminectomy of the entire separate neural arch i n spondylolisthesis, is a difficult operation. The purpose of this stu dy is to evaluate the results of PLIF with autologous bony graft, with out reduction or instrumentation in grade I and II spondylolisthesis. Material The authors report the results of a series of 36 cases of spo ndylolisthesis (out of a series of 160 cases) operated on with PLIF, a fter 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 clinicaly and radiologicaly. 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 fus ion. Before operation, 25 patients suffered backache and 20 had sciati c. Mean preoperative listhesis according to Boxall was 29 per cent. Me thods PLIF had been done with autologous bony graft and neural decompr ession without reduction. The thickness of the space had been restored with special progressive distracter. Postoperative back cast was used during 6 months. Results Postoperative nerve roots complications occu rred in 4 cases and were regressive within 3 months.Results were excel lent in 17 cases, good in 7 cases and poor in 3 cases. Patients return ed to work after 9.8 months (13.6 months for heavy work). 26 patients had solid tomographic interbody fusions. No additionnal subluxation wa s 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 (symptoma tic in 6 cases). The sagittal balance of the spine evaluated with a sp ecific index showed persistant 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 o f the adjacent discs shows that it is not necessary to extend fusion t o the upper disc. Instrumentation had not been used in this series but a cast seems to be indispensable. Instrumentation with plates and ped icular screws should be able to give more stability but is often respo nsable of iatrogenic lesions at the articular facets. Conclusion This study confirms the good results obtained by PLIF with nerve roots deco mpression in spondylolisthesis. Fusion is stable and does not accelera te degenerative lesion of the upper disc.