From 1977 to 1989 we operated 46 patients withspondylolistheses. We only did a reduction manually by a clamp orit occurs spontaneously to a certain grade in 14 patients. As wedid only a posterolateral fusion and used semi-rigid materials,we had a stable situation only in 2 cases, i.e. in 14 % or are-slip in 86 %. There was no correlation between the grade ofolisthesis or grade of reduction. Because of these bad results,we changes our conception to 360°. We did a reduction with theSOCON device in 21 cases until 1994 We did a follow-up in 18 ofour 20 reduced cases, 2.9 years postoperatively in average. Wehad a stable situation in 13 or 14 cases with circumferentialfusion, i.e. in 92 % after reduction and ventral andposterolateral fusion. Only one with insufficient anterior fusionlead to a new slip. This was the case with an infection of theanterior fusion. But we had only a 25 % stabilization, i.e. onlyin one of our four patients where we only did a posterolateralfusion after reduction. The re-slip occurred in higherdeformities with risk factors so that I think that in highergrade deformities or in case with risk factors an anterior fusionis inevitable.
The next question was that of anterior, posterior or combinedfusion. Notwithstanding, in many cases in spite of reduction,instrumentation and posterolateral fusion could not hold thereduction result. We have often seen that - because of remainingshear forces, especially in risk factors - there was aretranslating into the initial position. We have to bear in mindthat not seldom the posterior column is destroyed bydecompression and the support of the anterior column is weakenedafter the reduction process. So I think that in order toguarantee the reduction result in all spondylolistheses withgreater deformities and succeeded reduction an intercorporalfusion should be considered. Otherwise, progression of slip andbreakage of material will occur like here (Fig), 5 and 11 monthspostoperatively.
From time to time, in formerly unstable and reduced or partlyreduced spondylolisthesis we see - in spite of internal fixation- a loss of reduction, so that we did - as you can see on thisslide - an anterior fusion later on. Or we see a breakage ofsemi-rigid instrumentation in case of reduction. This reallyoccurs in case of plastic deformation of the fusion mass whichcannot resist the loading of the vertebra after the reduction,especially in a tender device like this one. But risk factors inlower grade deformities are not so frequent.