Dorothea Daentzer

Preliminary results in anterior cervical discectomy and fusion with an experimental bioabsorbable cage - clinical and radiological findings in an ovine animal model

BackgroundBioabsorbable implants are not widely used in spine surgery. This study investigated the clinical and radiological findings after anterior cervical discectomy and fusion (ACDF) in an ovine animal model with an experimental bioabsorbable cage consisting of magnesium and polymer (poly-ϵ-caprolactone, PCL) in comparison to a tricortical bone graft as the gold standard procedure.Materials and Methods24 full-grown sheep had ACDF of C3/4 and C5/6 with an experimental bioabsorbable implant (magnesium and PCL) in one level and an autologous tricortical bone graft in the second level. The sheep were divided into 4 groups (6 sheep each). After 3, 6, 12, or 24 weeks postoperatively, the cervical spines were harvested and conventional x-rays of each operated segment were conducted. The progress of interbody fusion was classified according to a three-point scoring system.ResultsThere were no operation related complications except for one intraoperative fracture of the anterior superior iliac spine and two cases of screw loosening and sinking, respectively. In particular, no vascular, neurologic, wound healing or infectious problems were observed. According to the time of follow-up, both interbody fusion devices showed similar behaviour with increasing intervertebral osseointegration and complete arthrodesis in 10 of 12 (83.3%) motion segments after 24 weeks.ConclusionsThe bioabsorbable magnesium-PCL cage used in this experimental animal study showed clinically no signs of incompatibility such as infectious or wound healing problems. The radiographic results regarding the osseointegration are comparable between the cage and the bone graft group.

Mechanical testing of an absorbable hybrid fusion cage for the cervical spine.

Abstract Conventional fusion devices (“cages”) are often used to join two vertebrae of the human spine and generally remain in the body for a lifetime and can theoretically lead to any complications. Therefore, an absorbable hybrid fusion cage consisting of a magnesium skeleton infiltrated with an absorbable polymer [poly-ε-caprolactone (PCL)] has been developed. The primary objective of the cage is to ensure an adequate stiffness of the disc space directly after the operation and to encourage the ingrowth of the new bone tissue to secure long life stability. Once a sufficiently rigid bone connection is formed, the implant should be absorbed. The purpose of this first study on the new absorbable fusion cage was to investigate the mechanical properties in vitro. Tensile tests were performed with tensile specimens type 1BA according to DIN EN ISO 527 made of PCL foamed using controlled expansion of saturated polymers (CESP). Furthermore, cyclic compression tests and compression tests with steady movement were performed with different designs of the new cage. Compression tests were also performed with vertebral endplates of ovine cadaveric spines. Foaming of PCL resulted in a modulus of elasticity of 135 MPa, which is approximately one third of unfoamed PCL. The results indicate that the initial compression strength of the implants should be adequate for the implantation in the cervical spine.

In vitro investigation of a new dynamic cervical implant: comparison to spinal fusion and total disc replacement.

Purpose and methodsFor the treatment of degenerative disc diseases of the cervical spine, anterior cervical discectomy and fusion (ACDF) still represents the standard procedure. However, long term clinical studies have shown a higher incidence of pathologies in the adjacent segments. As an alternative to spinal fusion, cervical total disc replacement (cTDR) or dynamically implants were increasingly used. This in vitro study analyzed the kinematics and intradiscal pressures in seven multi-segmental human cervical spine using hybrid multidirectional test method. The aim of our study was to compare the intact condition with a single-level dynamic stabilization with DCI®, with cTDR (activC®) and with simulated ACDF (CeSPACE® cage and CASPAR plate).ResultsNo significant changes in the kinematics and pressures were observed in all segments after arthroplasty. The DCI® significantly decreased the motion of the treated segment in flexion/extension and lateral bending with some remaining residual mobility. Thereby the motion of the upper segment was increased significantly in flexion/extension. No significant changes of the intradiscal pressures were observed. With simulated fusion the motion of the indexed level was significantly decreased in flexion/extension and axial rotation with the greatest changes in the adjacent levels and the highest pressures.ConclusionBased on our biomechanical study the DCI® can pose an alternative to fusion, which has a lesser effect on adjacent levels. This might reduce the risk of long-term degeneration in those levels. In particular, the facet joint arthritis and kyphotic deformity, as a contraindication to the arthroplasty, could be a clinical application of the dynamic implant.

In vitro-analysis of kinematics and intradiscal pressures in cervical arthroplasty versus fusion – A biomechanical study in a sheep model with two semi-constrained prosthesis

BackgroundAs an alternative technique to arthrodesis of the cervical spine, total disc replacement (TDR) has increasingly been used with the aim of restoration of the physiological function of the treated and adjacent motions segments. The purpose of this experimental study was to analyze the kinematics of the target level as well as of the adjacent segments, and to measure the pressures in the proximal and distal disc after arthrodesis as well as after arthroplasty with two different semi-constrained types of prosthesis.MethodsTwelve cadaveric ovine cervical spines underwent polysegmental (C2-5) multidirectional flexibility testing with a sensor-guided industrial serial robot. Additionally, pressures were recorded in the proximal and distal disc. The following three conditions were tested: (1) intact specimen, (2) single-level arthrodesis C3/4, (3) single-level TDR C3/4 using the Discover® in the first six specimens and the activ® C in the other six cadavers. Statistical analysis was performed for the total range of motion (ROM), the intervertebral ROM (iROM) and the intradiscal pressures (IDP) to compare both the three different conditions as well as the two disc prosthesis among each other.ResultsThe relative iROM in the target level was always lowered after fusion in the three directions of motion. In almost all cases, the relative iROM of the adjacent segments was almost always higher compared to the physiologic condition. After arthroplasty, we found increased relative iROM in the treated level in comparison to intact state in almost all cases, with relative iROM in the adjacent segments observed to be lower in almost all situations. The IDP in both adjacent discs always increased in flexion and extension after arthrodesis. In all but five cases, the IDP in each of the adjacent level was decreased below the values of the intact specimens after TDR. Overall, in none of the analyzed parameters were statistically significantly differences between both types of prostheses investigated.ConclusionThe results of this biomechanical study indicate that single-level implantation of semi-constrained TDR lead to a certain hypermobility in the treated segments with lowering the ROM in the adjacent levels in almost all situations.

Bioabsorbable Interbody Magnesium-polymer Cage: Degradation Kinetics, Biomechanical Stiffness, and Histological Findings From an Ovine Cervical Spine Fusion Model

Study Design. An experimental study using a sheep cervical spine interbody fusion model. Objective. First, to compare anterior cervical discectomy and fusion of an experimental bioabsorbable cage consisting of a magnesium alloy and a polymer (poly-&egr;-caprolactone, PCL) with an autologous tricortical iliac crest bone graft. Second, to determine the degradation kinetics of the cage, assess the 2 fusion devices for biomechanical stability, and determine their histological characteristics. Summary of Background Data. Bioabsorbable cages are not routinely used in spine surgery at present, due to some undesirable effects such as cracks and foreign body reactions. This study involved the manufacture of a bioabsorbable cage from a magnesium alloy and the polymer PCL, which was then used as a device for anterior cervical discectomy and fusion in a sheep cervical spine fusion model. Methods. Twenty-four sheep had anterior cervical discectomy and fusion of C3–C4 and C5–C6 with an experimental bioabsorbable cage consisting of the magnesium alloy AZ31, which was infiltrated and covered with PCL at 1 level and with an autologous tricortical iliac crest bone graft at a second level. The sheep were divided into 4 groups. After 3, 6, 12, or 24 weeks postimplantation, the animals were killed and the cervical spines were harvested. The intervertebral spaces with the cage were investigated using &mgr;-computed tomographic images to calculate degradation kinetics. Stiffness of all monosegments was determined through biomechanical testing. Histological analysis was performed to evaluate fusion status and to detect any foreign body reactions. The results from both implants were compared. Results. The magnesium-PCL cage showed nonlinear degradation over time. Both implants demonstrated time-dependent increases in stability, with a significantly greater stiffness of the bone graft after 24 weeks in all directions of motion. Histologically, the cage showed no signs of fusion with progressive encapsulation over time. Conclusion. In comparison with the bone graft, the bioabsorbable cage showed inferior stiffness and fusion properties. Thus, further component modifications are necessary. Level of Evidence: N/A

Thoracic juxtafacet cyst (JFC) as a rare cause of myelopathy - An additional reference to support the instability theory

Several causes for the development of a juxtafacet cyst (JFC) of the spine have been discussed, with a focus on instability with overload of the facet joints. In the thoracic spine, JFC is a very rare space-occupying lesion, which can lead to spinal canal stenosis with pain, myelopathic signs and neurological deficits. We report a case of a 70-year-old woman who had a posterolateral fusion of L2 to S1 and, six weeks later a L1 compression fracture. In the following period a thoracolumbar kyphosis has developed. Fourteen months after the fusion procedure a left-sided JFC T11/12 was identified on MRI and CT scans which led to myelopathic symptoms. This was not seen on former MRI scans. After surgical removal of the JFC the myelopathic symptoms were clearly reduced and the woman became pain free. This case report gives a strong support to the hypothesis that spinal instability can lead to overload of the facet joints and result in JFC.

Muskulärer Schiefhals@@@Muscular Torticollis

OBJECTIVE Correction of malalignment of the cervical spine with the head tilted to the side of the shortened muscle and rotation to the opposite side due to a contract sternocleidomastoid muscle. Attainment of an increased range of motion of the cervical spine and a better cosmetic appearance. Regression of a facial asymmetry. INDICATIONS Contract sternocleidomastoid muscle with deformity intolerable by the patients and their parents. CONTRAINDICATIONS Bony anomalies with consecutive torticollis. Torticollis caused by other muscular contractures (trapezoid muscle). Torticollis due to acute rheumatoid arthritis or other inflammation around the neck. Other forms of torticollis (psychogenic, ocular, vestibular or spasmodic torticollis). SURGICAL TECHNIQUE In younger children, subcutaneous tenotomy of the distal part of the sternocleidomastoid muscle. At preschool age, additional incision of the deep cervical fascial layer with an open tenotomy. In delayed operations, open distal and proximal tenotomy together with incision of the deep fascial layer or complete excision of the sternocleidomastoid muscle. POSTOPERATIVE MANAGEMENT Until the age of 6 years, application of a Minerva cast after surgery for 6 weeks. Subsequently, physical therapy for 6 months. In children of school age and older people, application of a soft cervical bandage for 6 weeks with functional physiotherapy. RESULTS In 83 reexamined patients with muscular torticollis, 76 biterminal and seven distal tenotomies had been performed. Regarding the age at the time of operation and the interval to follow-up, an improvement of facial symmetry could be achieved. At the control, 25 patients showed complete recovery of facial asymmetry, 43 had a slight and 15 a severe asymmetry. The complication rate was low with one injury to the external jugular vein and one transient facial nerve paresis. In two patients, passive overcorrection in the cast resulted in transient paresis. Two patients developed a recurrence of muscular torticollis.ZusammenfassungOperationszielBeseitigung einer durch einen verkürzten Musculus sternocleidomastoideus bedingten Fehlstellung der Halswirbelsäule mit Kippung des Kopfs zur Seite des verkürzten Muskels und Rotation zur Gegenseite. Erlangen einer größeren Beweglichkeit der Halswirbelsäule. Erreichen eines besseren ästhetischen Erscheinungsbilds. Rückbildung einer Gesichtsskoliose.IndikationenKontrakter Musculus sternocleidomastoideus mit von den Patienten und deren Eltern ästhetisch nicht tolerierter Deformität.KontraindikationenKnöcherne Anomalien mit der Folge eines Schiefhalses.Schiefhals durch Kontrakturen anderer Muskeln (Musculus trapezius).Schiefhals aufgrund akuter rheumatischer Arthritis oder anderer Entzündungen im Bereich des Halses.Andere Formen eines Schiefhalses (psychogener, okulärer, vestibulärer oder spastischer Tortikollis).OperationstechnikIn der Kindheit subkutane Tenotomie des distalen Ansatzes des Musculus sternocleidomastoideus. Im Vorschulalter zusätzliche Durchtrennung der tiefen Halsfaszie gemeinsam mit einer offenen Tenotomie. Bei verzögerten Operationen offene distale und proximale Tenotomie zusammen mit einer Durchtrennung der tiefen Faszie oder vollständige Entfernung des Kopfwendermuskels.WeiterbehandlungBis zum Alter von 6 Jahren nach dem Eingriff Anlegen eines Diademgipsverbands für 6 Wochen. Danach 6-monatige Physiotherapie. Ab dem Schulalter postoperativ Anlegen einer gepolsterten Halsbandage für 6 Wochen sowie frühfunktionelle Nachbehandlung.ErgebnisseBei 83 nachuntersuchten Patienten mit einem muskulären Schiefhals waren 76 biterminale und sieben distale Tenotomien durchgeführt worden. In Abhängigkeit vom Alter zum Zeitpunkt der Operation und vom Intervall bis zur Nachuntersuchung konnte eine Rückbildung der Gesichtsasymmetrie erzielt werden, so dass 25 Patienten bei der Kontrolle keine Gesichtsasymmetrie mehr aufwiesen, 43 noch eine leichte und 15 eine schwere Asymmetrie zeigten. Die Komplikationsrate war mit jeweils einer Verletzung der Vena jugularis externa und vorübergehenden Fazialisparese gering. Zweimal traten passagere Lähmungen durch einen in überkorrigierter Stellung angelegten Diademgipsverband auf. Zwei Patienten entwickelten ein Rezidiv des Schiefhalses.AbstractObjectiveCorrection of malalignment of the cervical spine with the head tilted to the side of the shortened muscle and rotation to the opposite side due to a contract sternocleidomastoid muscle. Attainment of an increased range of motion of the cervical spine and a better cosmetic appearance. Regression of a facial asymmetry.IndicationsContract sternocleidomastoid muscle with deformity intolerable by the patients and their parents.ContraindicationsBony anomalies with consecutive torticollis.Torticollis caused by other muscular contractures (trapezoid muscle).Torticollis due to acute rheumatoid arthritis or other inflammation around the neck.Other forms of torticollis (psychogenic, ocular, vestibular or spasmodic torticollis).Surgical TechniqueIn younger children, subcutaneous tenotomy of the distal part of the sternocleidomastoid muscle. At preschool age, additional incision of the deep cervical fascial layer with an open tenotomy. In delayed operations, open distal and proximal tenotomy together with incision of the deep fascial layer or complete excision of the sternocleidomastoid muscle.Postoperative ManagementUntil the age of 6 years, application of a Minerva cast after surgery for 6 weeks. Subsequently, physical therapy for 6 months. In children of school age and older people, application of a soft cervical bandage for 6 weeks with functional physiotherapy.ResultsIn 83 reexamined patients with muscular torticollis, 76 biterminal and seven distal tenotomies had been performed. Regarding the age at the time of operation and the interval to follow-up, an improvement of facial symmetry could be achieved. At the control, 25 patients showed complete recovery of facial asymmetry, 43 had a slight and 15 a severe asymmetry. The complication rate was low with one injury to the external jugular vein and one transient facial nerve paresis. In two patients, passive overcorrection in the cast resulted in transient paresis. Two patients developed a recurrence of muscular torticollis.

Influence of proprioceptive insoles on spinal curvature in patients with slight idiopathic scoliosis.

PURPOSE Proprioceptive insoles are known to influence the functions of posture and gait by modulations of the sensory structures at the sole of the foot. Literature has shown that they could improve the position of the upper-body in patients with postural complaints of the musculoskeletal system. The aim of this study was to evaluate the influence of proprioceptive insoles on the spinal curvature in patients with slight idiopathic scoliosis. PATIENTS AND METHODS Eighteen patients were included in this prospective, single-centre, randomized study. All patients needed to have a relevant growth potential and suffered from a slight idiopathic scoliosis. Two groups were used, where group 1 performed physiotherapy twice a week, whereas group 2 was additionally supplied with proprioceptive insoles. Patients underwent three-dimensional rasterstereography for back-shape analysis. Furthermore, a conventional x-ray imaging of the spine was performed at the beginning and 1 year later to document the curvatures. RESULTS There was no statistical difference in the Cobb angles, and in almost all parameters of the rasterstereography, there was no statistically significant change between and within both groups. CONCLUSION According to the results of this study, there was no evidence of any statistical significant effect of proprioceptive insoles on spinal curvature in patients with slight idiopathic scoliosis.

A customized modular reference array clamp for navigated spine surgery.

IntroductionThe current authors have developed a modular system of reference array fixation which is tailored specifically to the spinal level being operated upon. They believe that this system may further increase the precision and accuracy of pedicle screw placement.Materials and methodsTwo formalin-fixed whole body cadavers were used for this study. For cervical spine evaluation of the reference clamp, four odontoid screws (two per cadaver) for C1/C2-fusion and four lateral mass screws (two per cadaver) were implanted. Following navigated screw placement with 2D and 3D fluoroscopic verification, insertion of two lateral mass screws was performed. In the same way, lumbar and thoracic pedicle screws were implanted. Two pedicle screws were placed at two levels of the lumbar and two levels of the thoracic areas giving an overall of 16 screws implanted (8 cervical, 4 thoracic, and 4 lumbar). Postoperative evaluation involved comparison of postoperative 3D scans and preoperative planning images. A simple classification system was used for evaluation of any deviation from the planned trajectory.ResultsAll pedicle screw placements were performed as planned without any technical problems. The reference array clamps remained in position at all the spinal levels at which they were employed with no loosening or displacement and no secondary damage to any of the spinous processes. Manual manipulation was performed but no displacement or slippage was observed. Image artefacts caused by the reference clamp were not significant as to obscure the area of interest. Both imaging modalities (Iso-C 3D and Vario 3D) generated sufficiently precise 3D images. There was no substantial difference in quality when those two systems were compared.DiscussionInsufficient fixation of the reference clamp can lead to failure and complications. To date, no reference clamp systems have been developed specifically for navigated spine surgery.ConclusionsStable reference array fixation is a critical step in navigated surgery. To date, the same reference clamps have been applied to the spinal anatomy as have been developed originally for the appendicular skeleton. The current investigators have developed a novel modular clamp and have demonstrated its efficacy in a cadaveric model.

Clinical outcome and complication rate after posterior arthrodesis of the lumbar spine: Are there age-related differences? A comparative study

OBJECTIVES Lumbar arthrodesis is a frequently performed intervention to treat several spinal disorders like degenerative or instable conditions. According to the demographic trend, more and more elderly patients are expected to become candidates for any kind of surgical procedures including operations of the spine. In case of more complex operations like fusion a higher risk potential in older persons could be assumed. The goal of our study was to analyze the clinical results after lumbar fusion and to find out, if there are differences in the outcome and complication rate in patients divided in two age groups. METHODS 100 patients who consecutively had lumbar arthrodesis because of degenerative or instable conditions were retrospectively studied after a minimum of 12 months with regard to their clinical outcome and the complication rate. Statistical analysis was performed to find out any significant differences in patients younger and older than 65 years. RESULTS In both patient groups we found neither any statistically significant difference in all clinical outcome scores except for two items of the SF-36 nor in the complication rate. CONCLUSION Older age should not be the only criterion for exclusion for more extensive surgical procedures of the lumbar spine like arthrodesis.