Correspondence:
Prof. Dr. Klaus-Peter -Schulitz
Heinrich Heine University
Dept of Orthopaedic Surgery
Moorenstr. 5
40225 Düsseldorf / Germany
E-Mail: orthopae@uni-duesseldorf.de
Key words: Spondylolisthersis, spine surgery, spinal fusion,
The current pathways of treatment for spondylolisthesis are presented and discussed on the background of our own experience and the available literature. Special consideration is given to the nescesity of a reduction.
I would like to write about instrumentation and reduction in isthmic spondylolisthesis type II a. Type II is subdivided in break, elongation and fracture. And I write only about types Meyerding I - IV.
It not have to be mentioned that the surgical treatment was
only carried out in case of problems, mostly pain which could not
be influenced by conservative treatment and / or in case of
postural hyperlordotic deformity, progression of deformity a.s.o.
In case of pain, surgery is only indicated when you can refer the
pain not only to the specific level, but if you know exactly what
the reason of pain is.
In some cases, you can solve the problem by decompression of
isthmic pseudarthrosis or removal of disc herniation without fear
of further progression.
But if we do a fusion, we have to do this consequently and under
morphological and biomechanical aspects of the deformity.
Classification of Spondylolisthesis
In connection with arthrodesis, some questions arise which are discussed controversially. Shall we do a reduction? If this question is answered positively, should this be accomplished in one or several steps, conservatively by traction or by the use of an instrumentation device? Can we use a semi-rigid or should we use a rigid fixation device? Shall we do an anterior or posterior fusion or both?
I wish to discuss these questions on the basis of two different collectives, especially under the aspect of stability after operation, because I think that this meeting is more mechanically orientated. The answers depend on the degree of deformity and/or instability.
At first, I would like to talk about the lower grade deformities. I think it should be out of question not to reduce the vertebra. So in common, in lower grade deformities we recommend fusion in-situ - no reduction device is necessary - and we prefer the posterolateral fusion, because good results with fusion in-situ are achieved in more than 90 %. So that the next question of instrumentation is necessary in as far as the situation is stable. In an unstable situation of lower degree deformity, we need instrumentation, especially if we wish to guarantee the passive reduction result, which will occur in most cases on the operation room table and perhaps to improve the fusion rate. The question of instrumentation rigidity will be discussed later on.
The last question is, which kind of fusion is necessary. If there are no risk factors as trapezoid shape of the vertebra, if you have no marked rotation of the vertebra, no dome-shaped deformity and if there is only a small disc interspace, and if the shear stresses are not too high, rigid instrumentation and a posterolateral fusion will suffice.
From time to time, in formerly unstable and reduced or partly reduced spondylolisthesis we see - in spite of internal fixation - a loss of reduction, so that we did - as you can see on this slide - an anterior fusion later on. Or we see a breakage of semi-rigid instrumentation in case of reduction. This really occurs in case of plastic deformation of the fusion mass which cannot resist the loading of the vertebra after the reduction, especially in a tender device like this one. But risk factors in lower grade deformities are not so frequent.
If we have no risk factors and nor shear-stresses, a semi-rigid instrumentation after reduction is sufficient. In case of risk factors as high disc and high instability, progression and break will occur after reduction, even with a rigid system so that anterior fusion should be done in the same step.
To sum up. In minor olistheses and stable situations, No reduction, no instrumentation, either anterior or posterior fusion.
In unstable situations and with risk factors we use rigid instrumentation and an anterior intercorporal support, if we wish to guarantee the reduction and improve fusion results.
What are we doing to do in higher grade deformities? The first
question is that of reduction.
In a symposion on spondylolistheses, Nachemson and Wiltse (1976)
underlined that "there can be little doubt that reduction is
never indicated when the olisthesis is less than 25 % and hardly
ever when less than 50 %." I think that we agree with this
opinion, but these authors underlined also that "there is
considerable question, if reduction should ever be attempted by
any, but a few on a semi-research basis, because in-situ fusion
works so well."
Wiltse believes that there is no increase of slips and that all junctions are fused and Lonstein reports on excellent and good results in 88 % without differences in reduced and unreduced groups without instrumentation. But we think that this is sometimes, but not always true, and when we go through the literature, it could be confirmed that there is a distinct rate of non-union and progression of deformity without mentioning that the gait and the aesthetics of the body shape is not influenced.
Reduction offers some advantages:Firstly, it neutralizes the shear forces under certain assumptions, i.e. it promotes union, prevents progression and limits the fusion levels.You can imagine how high the shear forces are in case of high slip angle, sacral inclination and high sacro-horizontal angle, and if you erect the sacrum by reduction, you reduce shear forces. In literature, it is proposed to fuse two levels if the slip exceeds 50 %. In case of reduction, you can reduce the operation to the specific segment of olisthesis. There are, however, some exceptions in which reduction is not absolutely advantageous, i.e. especially in stable slippages which do not coincide with pathological kyphotic angle of a slipped vertebra and if the posture and gait are not influenced negatively.
To sum up the question of reduction, we think that reduction
should only be attempted in unstable situations with high shear
forces and pathological posture and in stable situation should
only be tried if the pathological body shape is the predominant
indication for operation.
The next question is if we shall perform it conservatively or use
an instrumentation. "The reduction technique is highly
demanding as you know. The surgical reduction with posterior
instrumentation can result in improvement, but the procedure is
technically difficult and is associated with a major risk of
neurological complications. "(Hensinger, 1989).
If we have decided to make a reduction of the slipped vertebra, we should know what happens morphologically when the vertebra slips. We know that a rotation of the vertebra goes ahead with the slippage which could be very important in high grade deformity and lead to a lumbo-sacral kyphosis and consecutively to a hyperlordosis of the lumbar spine as you can see here on a redrawn X-ray of a patient in supine and standing position from Boxall / Bradford.
Therefore, the key point of reduction is, above all, to lordose the slipped vertebra and not only to distract and draw back. And this can be managed by the SOCON device which has a three-dimensional adjustability between the screws and the linking members. Each distraction alone can only lead to an increase of the vertebra rotation as this was the case with the Harrington rod and is the case with other reduction devices. This lead to problems in the adjacent level, besides that you stabilize more than the one level as you can see on this slide, and above all there will be an lengthening of the distance and with that a distraction of the nerve root can occur. If you use an internal device which has only the possibility to carry out a translational force backwards, you would not use it as correction of the translation alone is not necessary for functional results in correction of body shape. Besides that you will not succeed if you only pull the vertebra back over the dome, as this deformity is a roll-glide-deformity. You have to decompose the reduction to the different steps of its specific morphological components to which belongs - above all - in high grade deformity- the rotation of the vertebra. With the help of such a device, a slipped vertebra has to be brought into the safe zone as Bradford called it.
Only if the kyphotic slipped vertebra could not be corrected sufficiently, then L4 should be included to restore the alignment - i.e. it has to be realigned with the sacrum. We could accomplish a 100 % reduction in 9 cases, 90 % in six patients and a 70 % reduction in 1 case. Gudeilines to operation in higher grade deformities
The next question was that of anterior, posterior or combined fusion. Notwithstanding, in many cases in spite of reduction, instrumentation and posterolateral fusion could not hold the reduction result. We have often seen that - because of remaining shear forces, especially in risk factors - there was a retranslating into the initial position. We have to bear in mind that not seldom the posterior column is destroyed by decompression and the support of the anterior column is weakened after the reduction process. So I think that in order to guarantee the reduction result in all spondylolistheses with greater deformities and succeeded reduction an intercorporal fusion should be considered. Otherwise, progression of slip and breakage of material will occur like here (Fig), 5 and 11 months postoperatively.
From 1977 to 1989 we operated 46 patients with spondylolistheses. We only did a reduction manually by a clamp or it occurs spontaneously to a certain grade in 14 patients. As we did only a posterolateral fusion and used semi-rigid materials, we had a stable situation only in 2 cases, i.e. in 14 % or a re-slip in 86 %. There was no correlation between the grade of olisthesis or grade of reduction. Because of these bad results, we changes our conception to 360°. We did a reduction with the SOCON device in 21 cases until 1994 We did a follow-up in 18 of our 20 reduced cases, 2.9 years postoperatively in average. We had a stable situation in 13 or 14 cases with circumferential fusion, i.e. in 92 % after reduction and ventral and posterolateral fusion. Only one with insufficient anterior fusion lead to a new slip. This was the case with an infection of the anterior fusion. But we had only a 25 % stabilization, i.e. only in one of our four patients where we only did a posterolateral fusion after reduction. The re-slip occurred in higher deformities with risk factors so that I think that in higher grade deformities or in case with risk factors an anterior fusion is inevitable.
If we compare the stability with rigid and with semi-rigid hardware in case of postero-lateral fusion, we had a stable situation in 25 % versus 14 %, i.e. that even rigid hardware cannot hold reduction if we only do posterolateral fusion. But maybe that we overtreat the patients if we fuse them circumferentially, and perhaps we can give up the posterolateral part of the fusion, as the posterolateral fusion alone does not contribute safely to stabilization.
Many authors came to the same conclusion, as e.g. the group around Steffee in 20 reduced cases, Dick and Schnebel in 15 higher grade deformities or Fabris in 15 cases. Biomechanically, the best fusion is an interbody fusion which allows the spine to load share with a fixation device. The S1-screw is not strong enough to hold the weight of the entire spine, so that the hardware will rotate, loosen or break.
I would like to mention that as a rule we do not perform a decompression in case of reduction. Nevertheless, we can show that the neurological impairment rate in the second series was not at all higher or less than related in literature when even a decompression had been performed. One patient complained about sciatica with a questionable transient sensory L5 syndrome in a higher grade deformity which was reduced. Therefore, up to now, we did not change our reduction and fusion procedure in one session without decompression.
If you think you must reduce the vertebra, you have to perform it consequently. But the question still remains, if reduction is necessary. This permanent discussion should also be carried out under the aspect of the surgeon's basis principle of primum non nocere in the treatment of patients.
