Othmar Schwarzenbach

The dynamic neutralization system for the spine: a multi-center study of a novel non-fusion system

Abstract. Various forms of lumbar instability require a surgical stabilization. As an alternative to fusion, a mobile, dynamic stabilization restricting segmental motion would be advantageous in various indications, allowing greater physiological function and reducing the inherent disadvantages of rigid instrumentation and fusion. The dynamic neutralization system for the spine (Dynesys) is a pedicle screw system for mobile stabilization, consisting of titanium alloy screws connected by an elastic synthetic compound, controlling motion in any plane (non-fusion system). This prospective, multi-center study evaluated the safety and efficacy of Dynesys in the treatment of lumbar instability conditions, evaluating pre- and post-operative pain, function, and radiological data on a consecutive series of 83 patients. Indications consisted of unstable segmental conditions, mainly combined with spinal stenosis (60.2%) and with degenerative discopathy (24.1%), in some cases with disc herniation (8.4%), and with revision surgery (6.0%). Thirty-nine patients additionally had degenerative spondylolisthesis, and 30 patients had undergone previous lumbar surgery. In 56 patients instrumentation was combined with direct decompression. The mean age at operation was 58.2 (range 26.8–85.3) years; the mean follow-up time was 38.1 months (range 11.2–79.1 months). There were nine complications unrelated to the implant, and one due to a screw malplacement. Four of them required an early surgical reintervention. Additional lumbar surgery in the follow-up period included: implant removal and conversion into spinal fusion with rigid instrumentation for persisting pain in three cases, laminectomy of an index segment in one case and screw removal due to loosening in one case. In seven cases, radiological signs of screw loosening were observed. In seven cases, adjacent segment degeneration necessitated further surgery. Mean pain and function scores improved significantly from baseline to follow-up, as follows: back pain scale from 7.4 to 3.1, leg pain scale from 6.9 to 2.4, and Oswestry Disability Index from 55.4% to 22.9%. These study results compare well with those obtained by conventional procedures; in addition to which, mobile stabilization is less invasive than fusion. Long-term screw fixation is dependent on correct screw dimension and proper screw positioning. The natural course of polysegmental disease in some cases necessitates further surgery as the disease progresses. Dynamic neutralization proved to be a safe and effective alternative in the treatment of unstable lumbar conditions.

Accuracy of computer-assisted pedicle screw placement : an in-vivo computed tomography analysis

Study Design. A computer‐assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo. Objectives. To evaluate the systems applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo. Summary of Background Data. Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex. Methods. The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm. Results. The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed. Conclusions. The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.

Computer-Aided Fixation of Spinal Implants

Medical imaging provides an important basis for modern diagnosis as well as for preoperative planning of surgical procedures. However, information gained cannot be transferred directly into the operating room. Furthermore, the safety and accuracy of the surgical intervention would be improved by interactive navigation of surgical instruments. These features are provided by the system for computer-aided fixation of spinal implants described in this paper.

Treatment of thoracolumbar burst fractures without neurologic deficit by indirect reduction and posterior instrumentation: bisegmental stabilization with monosegmental fusion

Abstract This study retrospectively reviews 20 sequential patients with thoracolumbar burst fractures without neurologic deficit. All patients were treated by indirect reduction, bisegmental posterior transpedicular instrumentation and monosegmental fusion. Clinical and radiological outcome was analyzed after an average follow-up of 6.4 years. Re-kyphosis of the entire segment including the cephaled disc was significant with loss of the entire postoperative correction over time. This did not influence the generally benign clinical outcome. Compared to its normal height the fused cephalad disc was reduced by 70% and the temporarily spanned caudal disc by 40%. Motion at the temporarily spanned segment could be detected in 11 patients at follow-up, with no relation to the clinical result. Posterior instrumentation of thoracolumbar burst fractures can initially reduce the segmental kyphosis completely. The loss of correction within the fractured vertebral body is small. However, disc space collapse leads to eventual complete loss of segmental reduction. Therefore, posterolateral fusion alone does not prevent disc space collapse. Nevertheless, clinical long-term results are favorable. However, if disc space collapse has to prevented, an interbody disc clearance and fusion is recommended.

Dens fractures in the elderly. Results of anterior screw fixation in 19 elderly patients.

Type 2 dens fractures in the elderly may be regarded as fragility fractures due to osteoporosis and are prone to nonunion with closed treatment. We investigated the outcome of direct anterior screw fixation of these fractures in 19 patients over 65 years of age. The type of injury, radiological appearance over time and the clinical outcome were analyzed, with an average follow-up of 4.5 years. Surgery and postoperative treatment were tolerated well in all patients. In 16 cases, bony union was achieved after 3-6 months. 2 pseudarthroses, which required no treatment, occurred. At follow-up, 15 patients had no symptoms. 10 of the patients had diminished rotation. We conclude that anterior screw fixation is a successful therapy in most cases of type 2 dens fractures in the elderly.

Image-Guided Computer-Assisted Spine Surgery: A Pilot Study on Pedicle Screw Fixation

As the pedicle offers a strong point of attachment to the spine, several instrumentation systems using screws that go through the pedicle into the vertebral body have been developed to provide internal stability. All pedicle screw systems share the risk of damage to adjacent neural structures as a result of improper screw placement. A computer-assisted system allowing precise preoperative planning and real-time intraoperative interactive image localization has been implemented for spine instrumentation to optimize transpedicular spine fixation. A validation study was performed in an in vitro set-up drilling 20 pedicle pilot holes in lumbar vertebrae. An analysis in 77 histological cuts showed an ideal location in 70 with no case of injury to the pedicle cortex. We discuss initial clinical experience on cases of posterior lumbar stabilization. Interactive computer-assisted spine surgery provides an accurate and safe approach for transpedicular screw fixation and may provide a useful tool for optimization of spine surgery.

Long-Term Outcome After Monosegmental L4/5 Stabilization for Degenerative Spondylolisthesis With the Dynesys Device

Study Design:Retrospective analysis of prospectively collected clinical data. Objective:To assess the long-term outcome of patients with monosegmental L4/5 degenerative spondylolisthesis treated with the dynamic Dynesys device. Summary of Background Data:The Dynesys system has been used as a semirigid, lumbar dorsal pedicular stabilization device since 1994. Good short-term results have been reported, but little is known about the long-term outcome after treatment for degenerative spondylolisthesis at the L4/5 level. Methods:A total of 39 consecutive patients with symptomatic degenerative lumbar spondylolisthesis at the L4/5 level were treated with bilateral decompression and Dynesys instrumentation. At a mean follow-up of 7.2 years (range, 5.0–11.2 y), they underwent clinical and radiographic evaluation and quality of life assessment. Results:At final follow-up, back pain improved in 89% and leg pain improved in 86% of patients compared with preoperative status. Eighty-three percent of patients reported global subjective improvement. Ninety-two percent would undergo the surgery again. Eight patients (21%) required further surgery because of symptomatic adjacent segment disease (6 cases), late-onset infection (1 case), and screw breakage (1 case). In 9 cases, radiologic progression of spondylolisthesis at the operated segment was found. Seventy-four percent of operated segments showed limited flexion-extension range of <4 degrees. Adjacent segment pathology, although without clinical correlation, was diagnosed at the L5/S1 (17.9%) and L3/4 (28.2%) segments. In 4 cases, asymptomatic screw loosening was observed. Conclusions:Monosegmental Dynesys instrumentation of degenerative spondylolisthesis at L4/5 shows good long-term results. The rate of secondary surgeries is comparable to other dorsal instrumentation devices. Residual range of motion in the stabilized segment is reduced, and the rate of radiologic and symptomatic adjacent segment degeneration is low. Patient satisfaction is high. Dynesys stabilization of symptomatic L4/5 degenerative spondylolisthesis is a possible alternative to other stabilization devices.

Hybrid stabilization with ALIF L5/S1 and total disc replacement L4/L5

Introduction Spinal fusion in the treatment of chronic painful lumbar degenerative disc disease (DDD) has proven to be effective [1]. Posterior instrumentation with the addition of either anterior or posterior interbody fusion lead to significantly higher fusion rates, but are also associated with higher costs, increased operative morbidity and complications. The lack of expected clinical success of these demanding surgical techniques led to the development of stand-alone anterior lumbar fusion devices that allow for a less invasive surgical approach, which should improve the postoperative outcome. Biomechanically, these devices compare favourably to the techniques of combined anterior–posterior instrumentation. Recently, total disc replacement (TDR) has also proven to be effective in the treatment of discogenic low back pain [2]. Patients with multisegmental DDD resistant to conservative therapy are typically treated with either fusion or non-fusion surgical technique. Anterior lumbar interbody fusion (ALIF) and total disc replacement (TDR) are widely accepted methods for the treatment of DDD [3, 4]. Depending on the stage of the degenerative process either a fusion or a motion preserving technique can be applied.

Short segment treatment of adult degenerative scoliosis with TLIF L3/L4.

Case description A 67 year old female suffering from permanent severe attacks of back pain and radiating pain to the left leg since about 2 years. She has a limited walking distance due to the leg pain. Physical exercises increase the back pain. She has had different conservative treatments without lasting pain reduction. Physical examination shows a slightly dysbalanced lumbar right convex scoliosis with tenderness over the mid lumbar spinous processes. No neurological deficit. The plain X-rays show a multisegmental degeneration of the lumbar spine. Right convex lumbar scoliosis with apex at L3/L4. L3/L4 shows a lateral sliding L3 over L4. The MRI shows Modic Type I and II changes at L3/L4. Left dominant recessal and foraminal stenosis at L3/L4. Preoperative Oswestry 46.6%, VAS back pain 6/10, VAS leg pain 6/10. Epidural and facet joint injection at L3/L4 level temporary improved the leg and back pain.

Dynamische dorsale Stabilisierung mithilfe des Pedikelschrauben-Systems DYNESYS®

OBJECTIVE The dynamic neutralization system for the spine (DYNESYS®) is a pedicle screw based system intending mobile restabilization substituting physiological tissue restraints and thus approximating the unstable motion pattern to a normal pattern. It consists of titanium alloy screws, connected by an elastic synthetic compound (PET band and PCU spacer) controlling motion in any plane. DYNESYS® can be used for mono- or multilevel stabilizations in the lumbar spine. INDICATIONS DYNESYS® is indicated in the treatment of degenerative disease of the lumbar motion segment with instability and most often in combination with functional or structural spinal canal stenosis. CONTRAINDICATIONS Primary and secondary bone tumors of the spine. Spinal fractures. Infections. Lytic/isthmic spondylolisthesis. Degenerative spondylolisthesis > I°-II°. Facetectomy. Stabilization of thoracic and cervical spine. Allergies to components of DYNESYS®. Pregnancy. SURGICAL TECHNIQUE Standard midline approach. Decompression of the segment by laminotomy if indicated. Place the screws lateral to the facet joints. Measure the distance between the screw heads. Cut the spacers. Introduce spacer and cord on both sides. The length of the PCU spacer is determined by the distance of the pedicle screws and depends on the pathology of the lumbar motion segment. Tighten set screws under correct compression of the system. POSTOPERATIVE MANAGEMENT Mobilisation at the first day after surgery. No bracing necessary if there is no doubt about primary fixation of the screws. Physical strenuous work not earlier than 8 weeks postoperatively. RESULTS DYNESYS® is a reliable dynamic stabilization system with good clinical results if used in correct indications.ZusammenfassungOperationszielDas dynamische Neutralisationssystem DYNESYS® dient der pedikulären Stabilisation der lumbalen Wirbelsäule. Das System unterstützt eine kontrollierte Restbewegung des instrumentierten lumbalen Bewegungssegments mit der Unterdrückung der diskovertebralen Dyskinesie (Instabilität, Dysstabilität). Seine Pedikelschrauben bestehen aus Titan, die elastisch mittels PET-Band und PCU-Kissen verbunden sind. Es wird für mono- und multisegmentale Stabilisierungen der Lendenwirbelsäule eingesetzt.IndikationenDYNESYS® ist indiziert bei degenerativen Erkrankungen des lumbalen Bewegungssegments (Diskopathie) mit Zeichen der Instabilität (Antero-/Retrolisthesis). Meistens liegen zusätzlich funktionelle oder etablierte Spinalkanalstenosen vor.KontraindikationenLokale, primäre und sekundäre Knochentumoren. Wirbelfrakturen. Infektionen. Lytische/isthmische Spondylolisthesen, degenerative Spondylolisthesen > I°–II°. Fazettektomie. Therapie der Brust- und Halswirbelsäule. Allergien gegen Implantatkomponenten. Schwangerschaft.OperationstechnikDYNESYS® wird meist über einen dorsalen medianen Zugang eingesetzt. Wenn nötig wird das Bewegungssegment dekomprimiert (Laminotomie). Die Pedikelschrauben werden lateral der Gelenke leicht konvergierend in die Pedikel eingeschraubt. Die PCU-Kissen werden ausgemessen und zurechtgeschnitten. Die Kissenlänge wird durch den Abstand der Schraubenköpfe determiniert und ist abhängig von der zu behandelnden Segmentpathologie. Die PET-Bänder werden nun durch die Schraubenköpfe und durch das Kissen eingefädelt. Festziehen der Stiftschrauben unter Kompression des Kissens mit dem Bandspanner.WeiterbehandlungMobilisation am ersten postoperativen Tag. Tragen eines Lendenmieders je nach Abhängigkeit der initialen Verankerung der Schrauben und den postoperativen Schmerzen. Aufnahme von körperlich belastenden Tätigkeiten frühestens 8 Wochen nach der Operation.ErgebnisseBei korrekter Indikationsstellung ist DYNESYS® ein sicheres Stabilisationssystem mit guten klinischen Ergebnissen.AbstractObjectiveThe dynamic neutralization system for the spine (DYNESYS®) is a pedicle screw based system intending mobile restabilization substituting physiological tissue restraints and thus approximating the unstable motion pattern to a normal pattern. It consists of titanium alloy screws, connected by an elastic synthetic compound (PET band and PCU spacer) controlling motion in any plane. DYNESYS® can be used for mono- or multilevel stabilizations in the lumbar spine.IndicationsDYNESYS® is indicated in the treatment of degenerative disease of the lumbar motion segment with instability and most often in combination with functional or structural spinal canal stenosis.ContraindicationsPrimary and secondary bone tumors of the spine. Spinal fractures. Infections. Lytic/isthmic spondylolisthesis. Degenerative spondylolisthesis > I°–II°. Facetectomy. Stabilization of thoracic and cervical spine. Allergies to components of DYNESYS®. Pregnancy.Surgical TechniqueStandard midline approach. Decompression of the segment by laminotomy if indicated. Place the screws lateral to the facet joints. Measure the distance between the screw heads. Cut the spacers. Introduce spacer and cord on both sides. The length of the PCU spacer is determined by the distance of the pedicle screws and depends on the pathology of the lumbar motion segment. Tighten set screws under correct compression of the system.Postoperative ManagementMobilisation at the first day after surgery. No bracing necessary if there is no doubt about primary fixation of the screws. Physical strenuous work not earlier than 8 weeks postoperatively.ResultsDYNESYS® is a reliable dynamic stabilization system with good clinical results if used in correct indications.