The aim of the study was to assess the results of posterolateral fusion (PLF) of L5/S1 level spondylolisthesis.

Materials 19 children (5 girls, 14 boys) aged 10–18 years (average 14) were treated surgically PLF in years 1985–2002. 18 cases before surgery were classified as grade I and II, 1 as grade III according to Meyerding classification. Long lasted low back pain, progression of the slippage was the main indication for operative treatment.

In every case suspension in prone position were applied before surgery.

Methods The Denis clinical classification was used to evaluate results. On radiographs we evaluated the verticalisation of the sacrum, lordosis at lumbosacral area by drawing Whitman-Ferguson, Boxall, Fernand-Fox angles. The mobility of the fused segment was estimated on the functional radiographs.

Results In clinical evaluation improvement was achieved in 18 cases, in 1 no improvement was achieved. In radiological estimation the slippage decreased in 17 cases varying from 1 grade to 39 grades (average 10 grades). In 1 case no improvment was achieved and in 1 the slippage increased (8 grades). The value of Fernand-Fox angle increased from 1 grade to 35 grades in 16 cases; in 1 no improvement was achieved and in 2 cases the value decreased. In every patient the posterior segmental union was achieved.

On MRI scans disc degeneration was observed in 2 patients.

Conlusions Our results confirm the existence of the remodeling process in the lumbo-sacral area of the spine.

We think that PLF in painful grade I and II spondylolisthesis is adequate method of treatment.