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Treatment of lumbar spondylolisthesis and related unstable spinal lesions:

the usefulness of PLIF with cages and dynamic interpedicular posterior fixation for circumferential arthrodesis and prevention of adjacent level degeneration.


Professor in Neurosurgery, University C. BERNARD, Lyon, FRANCE

Presented at the 3rd World Spine Meeting (Rio de Janeiro, Aug.2005)

P Treatment of lumbar spondylolisthesis and related

lumbar interbody fusion (PLIF) with cages is optimal not only for intervertebral fusion but also in restoring the weight bearing to the anterior structures and disc height as well as foraminal opening for nerve root decompression. Posterior fixation is indicated for immediate stabilization in order to enhance osteogenesis and to allow early mobilization without external brace in order to prevent muscles atrophy and spinal balance deterioration. PLIF as distractive technique and posterior interpedicular fixation in compression restores physiological lordosis and indeed protects adjacent spinal levels. Dynamic fixation with interpedicular damper significantly reduces the risk of screw breakage and enhances the bone fusion by maintaining constraints on the cages.


unstable spinal lesions:

the usefulness of PLIF with cages and dynamic interpedicular posterior fixation for circumferential arthrodesis and prevention of adjacent level degeneration.

Prevention of adjacent degenerative disease by using dynamic extension to the overlying vertebra of the posterior interpedicular fixation as a non-fusion technology is indicated for adjacent spinal level protection in case of pre-operative imaging with adjacent pathological disc to the forecasted fusion. The aims of this retrospective study were not only to assess the clinical outcome and fusion rate in the group of patients treated on with the circumferential arthrodesis achieved in one stage with posterior approach, but also to determine in the subgroup of patients with long-term follow-up over 8 years the clinical and anatomical benefits of the protection of the adjacent level with the posterior dynamic stabilization in order to prevent recurrent symptoms.

Materials and methods:

Study design: From 1978 to September 2003, PLIF was performed in a personal consecutive series of 1500 patients with clinical presentation of nerve root compression related to unstable bone or disco-ligamental lumbar lesions such as: s Isthmic spondylolisthesis: 1095 cases (73%), s Foraminal stenosis with collapsed disc and degenerative spondylolisthesis: 259 cases (17.2%), s Disco-ligamental degenerative or iatrogenic unstable lesions documented by dynamic X-rays: 148 cases (9.8%). In this series, 430 patients have been operated on between 1993 and 2000 for lumbar stabilization of isthmic spondylolisthesis with circumferential arthrodesis in one stage through posterior approach by using cages for PLIF and posterior interpedicular fixation. 290 patients were reviewed for clinical and radiological evaluation with long-term follow-up (> 4 years). Within the last group of cases, 34 patients underwent surgery for isthmic spondylolisthesis between 06/1993 and 04/1997 with PLIF and posterior fixation and dynamic protection of the pathological adjacent disc and were reviewed with a mean follow-up of 8.27 years for the assessment of the evolution of adjacent spinal levels. Surgical procedure: The intervertebral space was posteriorly approached. The mobile posterior vertebral arch is completely removed. The lateral recesses and the foramens are widely open with the articular facets total resection. Restoration of the intervertebral height in order to open the foramens and to achieve a total nerve root decompression was achieved by using distracting probes after discal resection. Such distraction with restoration of normal intervertebral discal height results in partial reduction of the horizontal slipping. This partial reduction is efficient enough for nerve root d e c o m p r e s s i o n . To t a l r e d u c t i o n o f g r a d e 3 o r 4 spondylolisthesis is not advisable because such reduction creates reactional excessive constraint to the overlying spinal segment with high risk of adjacent degeneration. Cortical bone of the vertebral endplates was carefully kept intact. Distracting PLIF was performed by using large intervertebral cages filled up with cancellous bone from the laminectomy. Cylindrical or threaded cages were implanted in 50 cases. Large parallelepipedic titanium cages were used in 290 cases and since 1997 PEEK polymer ADONYS cages were inserted for PLIF on 90 patients.


Dynamic IsobarTM TTL rod and AladynTM plate - postoperative X-rays control of Aladyn plate


Posterior interpedicular fixation in compression was performed for immediate stabilization and restoration of lordosis. Rigid plates or rods were used in 98 cases. Dynamic ISOLOCK or ALADYN plates or dynamic TTL rods with interpedicular damper have been used since 1993 for posterior fixation in 332 cases. In case of low-grade 0, 1 or 2 spondylolisthesis and pre-operatively normal adjacent disc, monosegmental PLIF and short posterior fixation were performed. In case of severely slipped spondylolisthesis and/or adjacent pathological but not compressive disc, the circumferential arthrodesis performed at

the level of the severe unstable lesion was completed with adjacent dynamic interpedicular stabilization. In case of adjacent compressive prolapsed or excluded disc, adjacent discectomy with second PLIF was performed. Getting up and walking without any external contention was allowed the day after the surgical procedure. The patient was discharged after five days and rehabilitation was immediately set out with the main purpose of restoration of posterior muscles and well-balanced lumbar lordosis. The patient was ergonomically trained to prevent excessive flexion and axial rotation.


Fusion rate: 290 patients who were operated on between 1993 and 2000 for lumbar stabilization of isthmic spondylolisthesis with cages for PLIF and posterior interpedicular fixation (dynamic posterior fixation in 332 cases), .were reviewed for clinical and radiological evaluation with longterm follow-up ( > 4 years). No local infection was observed. No patient required second surgery for clinical complication or for removal of dismantled or broken fixation system.

Isthmic L5-S1 spondylolisthesis with adjacent L4-L5 pathological disc treated on with circumferential arthrodesis L5-S1 (PLIF with PEEK polymer cages + posterior fixation) and adjacent protection of the L4-L5 disc with a posterior interpedicular dynamic element.

In these 290 reviewed cases, 285 patients (98.3%) demonstrated bone fusion with radiological documentation of new intervertebral bone bridges, with increased bone density within the cages, without osteolysis or bone lucencies at the interface with the implants and without intervertebral motion on the dynamic X-rays. In only two cases the postoperative

X-rays control documented bone subsidence with intracorporeal penetration of the cages. This complication induces loss of the intervertebral height restoration without any incidence on the fusion. In 5 cases it was not possible to document bone growth, but dynamic X-rays showed no intervertebral motion.

PLIF for grade II L5-S1 isthmic spondylolisthesis: note the restoration of L5-S1 intervertebral height and foraminal opening. Fusion is well documented with the intervertebral bone bridges.

No radicular complication or iatrogenic clinical complication due to the posterior fixation or the intervertebral implants were experienced in this series. The clinical outcome assessed by the degree of persistent radicular pain, the consumption of analgesics, the evaluation of walking distance and the working ability was excellent (Ie. improvement of the functional score >50%) in .245 patients

Clinical outcome:


(84.5%). The clinical outcome assessed by using the StaufferCoventry criteria, was evaluated as excellent in 221 cases (76.2%), fair in 61 cases (21%) and poor in 8 patients (2.7%). By using the modified Prolo score, the clinical outcome was excellent in 109 patients (37.6%), good in 121 patients (41.7%), fair in 53 patients (18.3%) and poor in 7 patients (2.4%).


Isthmic spondylolisthesis L5-S1: Documentation of intervertebral fusion 7 years after surgery

In order to assess the long-term benefits of the dynamic Intervertebral stabilization as a protective non-fusion technique for pathological adjacent disc a specific retrospective study was carried out in a subgroup of 34 patients operated on between 06/93 and 04/97 for isthmic spondylolisthesis L4-L5 or L5-S1 by PLIF and posterior bisegmental fixation for radicular decompression, stabilization and protection of the adjacent pathological disc by using a dynamic interpedicular damper without grafting. 22 were reviewed with clinical evaluation and radiological assessment after a mean long-term follow-up of 8.27 years:

Evolution of the adjacent disc:

motion on dynamic X-rays was evident in 15 cases (68.2%) with important motion over 4° in 3 cases and within the range of 4° in 12 cases. Conservation of the discal intervertebral height was well documented in 18 cases (82%).

1. The radiological evidence of fusion of the disc treated on by

PLIF was documented in aIl the patients (22/22) with new intervertebral bone bridges and absence of intervertebral motion on dynamic X-rays. No vertebral endplate subsidence and fracture or dismantling of the fixation system were noted. Loss of the restored intervertebral height was observed in 1 case (4.5%).

3. Severe new degenerative lesions with significant discal collapsus, sagital mobility and horizontal slipping or new arthrotic conditions of the neo-hinge "free" disc adjacent to the instrumented bisegmental vertebral segment was observed in only 1 case (4.6%). No spontaneous fusion of this neo-hinge disc was documented. Persistence of intervertebral motion of this disc was evident in 21 cases (95.4%) with a normal range of motion over 40 in 10 cases and within 40 in 11 cases. The total balance of the overlying spine was assessed with a physiological harmonious lordosis in 16 cases ( 72.7%). 4. In this subgroup of patients the clinical outcome after longterm follow-up was evaluated by using a low back pain visual analogue scale for self-rated assessment. ln 18 cases (81.5%) pain was rated under 4/10. The mean evaluation of low back pain was for all the patients at the pre-operative period at 8.36, after one year follow-up at 5.12 and after 8.27 years follow-up at 3.4. Radicular leg pain was rated as inferior to 1/10 in 15 cases (68.2%). The mean evaluation of radicular leg pain was for all the patients at the pre-operative period at 6.23, after one year follow-up at 3.2 and after 8.27 years follow-up at 2.1 The patient's satisfaction index was assessed by using the SF36 scale from 1: strongly agree to 5: strongly disagree. In 21 patients (91%) the satisfaction index was rated at grade I and the patient's comment was agreement for second similar surgery if it would be necessary .

2. The radiological assessment after long-term follow-up of the adjacent pathological disc protected by the dynamic interpedicular element documented spontaneous interarticular .facets fusion in 4 cases (18.5%). Persistence of Intervertebral


X-rays control of a spondylolisthesis grade I L5-S1 8 years after surgery. Note evidence of fusion L5-S1 with bone bridges back to the titanium cages. The intervertebral L4-L5 discal height is well maintained and no new degenerative lesion is documented at the "free" L3-L4 level




rate of fusion and the absence of failure of the fixation system emphasize the efficiency of using both intervertebral cages and posterior fixation for lumbar stabilization. Radiolucent PEEK cages allow easy X-rays controls and improve bone fusion through their own resilience close to the physiological cortical bone elasticity in comparison with the stiffness of titanium alloys. Dynamic fixation significantly reduces the risk of screw breakage by the absorption of the stress on the interpedicular damper and enhances bone fusion by maintaining constraints on the cages which remain under compressive load (Wolff's law). This dynamic fixation system prevents the stress-shielding phenomenon. Fusion with polymer cages and dynamic fixation, avoidance of postoperative corset, early rehabilitation for restoring lordosis and powerful posterior muscles, collectively meet aIl the requirements not only for


pain relief but also for definitive stabilization without iatrogenic spinal complication or further destabilisation of spine at the adjacent level to the arthrodesis. Preventive protection of the intervertebral level adjacent to the fused segment is indicated in case of adjacent degenerative disc or adjacent arthritic conditions. Dynamic fixation which allows controlled intervertebral motion for this adjacent level seems to create the mechanical conditions for a transitional intervertebral zone between the rigid fused segment and the "free" adjacent hypersollicitated level above the spinal instrumentation. This biomechanical intermediate zone seems to be very important before the restoration of physiological lordosis achieved by recovery of efficient posterior muscles. Such dynamic fixation seems to be an efficient measure to prevent adjacent level degeneration and recurrence of symptoms.


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