Study design: Long-term retrospective study of the low grade isthmic Spondylolisthesis treated by means of instrumented posterolateral fixation in adults.

Objective: To evaluate clinical and functional survival of surgical treatment of the espondylolisthesis after minimum 10 years of follow-up. To study the radiologic behaviour of the fused and the adjacent level.

Summary of background: It’s been suggested in many different series that posterolateral instrumented fusion is not always capable to improve the lumbar pain neither to stabilize a vertebral segment if the anterior column is not supported. The need to perform and interbody fusion in the surgical treatment of isthmic spondilolysthesis is still unknown.

Material and method: From a total of 42 patients operated by low grade isthmic espondylolisthesis, it’s been obtained a clinic and radiological follow up in 31 patients, 19 females and 12 males. The average age at the moment of surgery was 34.9 years and in the last review was 46.5 years. The average follow up has been 11.8 years. Pain and functional disability was quantified by a visual analogical Scale (VAS) and the Oswestry Disability Index (ODI). Quality of life was assessed by the SF-36. The preoperative and postoperative percentage of slip and lumbosacral kyphosis was evaluated in serial radiographs at the fused level. The intervertebral disc height and dynamic behaviour was evaluated at the adjacent level.

Results: Spondylolisthesis was present at L5 in 24 patients, L4 in 6 patients and at L3 in 1 patient. In the 87% of cases the fusion was one level and the 3% was two levels. The mean (range) anterior slip at postoperative was 21.9%, and 23.1% at the final follow up. The average angle for the lumbosacral kyphosis was 19.4° in the postoperative and 19.5° in the follow up. The Oswestry Disability Index scores average at follow up was 13,6. 75.8% of patients were considered with a minimum disability and 17.2% with a moderate disability. The 67.7% of the patients develop rewarded activities, the 25.6% develop domestic tasks and the 6.45% are in a disability situation. There was no statistically significant difference between the study population SF-36 scores and those of the general population, same age and gender, in any of the eight domains.

Conclusions: Long-term clinical and radiographic outcomes after “in situ” posterolateral instrumented fusion of adult low-grade Spondylolisthesis were satisfactory. This study further confirms that such surgery is appropriate for these selected patients.