FAILURE OF A MODIFIED POSTERIOR LUMBAR INTERBODY FUSION TECHNIQUE TO PRODUCE ADEQUATE PAIN RELIEF IN ISTHMIC SPONDYLOLYTIC GRADE-1 SPONDYLOLISTHESIS PATIENTS - A PROSPECTIVE-STUDY OF 20 PATIENTS

A modified posterior lumbar interbody fusion procedure is described: t his technique basically uses only two tricortical bone grafts and does not produce a distraction at the interspace while inserting the bone grafts. Twenty patients with intractable back and leg pain due to an i sthmic spondylolysis and a grade 1 spondylolisthesis were operated usi ng this technique and a prospective study with a mean follow-up of 41 months was conducted to evaluate the results. The final evaluation inv olved a questionnaire, a clinical examination, and a lumbar spine radi ographic series. Fourty-five percent of the patients had good or excel lent results whereas 55%. had fair or poor results. The possible reaso ns for these unfavorable results are discussed.