Lothar Wiesner

Clinical evaluation and computed tomography scan analysis of screw tracts after percutaneous insertion of pedicle screws in the lumbar spine

STUDY DESIGN An examination of the accuracy of percutaneous pedicle screw placement in the lumbar spine. Using computed tomography scan analysis after implant removal, the screw tracts could be analyzed regarding the degree and direction of screw dislocation. OBJECTIVES To investigate the misplacement rate and related clinical complications of percutaneous pedicle screw insertion in the lumbar spine. SUMMARY OF BACKGROUND DATA The feasibility of the external fixation test has been investigated in several studies. Although pedicle screw misplacement has been reported as one of the main complications, there are no reliable data on the misplacement rate for this difficult surgical procedure. METHODS In this study, 51 consecutive patients with suspected segmental instability were investigated after external transpedicular screw insertion for the external fixation test. Computed tomography scans of all instrumented pedicles from L2 to S1 were performed after screw removal. The screw tracts were analyzed, and the direction and degree of the pedicle violations were noted. In addition, the screw and pedicle angles were measured. RESULTS Of 408 percutaneously inserted pedicle screws, only 27 screws (6.6%) were misplaced. There were 19 medial pedicle violations, 6 lateral cortical defects, and only 1 cranial and 1 caudal displacement. With respect to the spinal level, S1 showed the highest misplacement rate, with 11 screw dislocations (12%). After surgery, found two nerve root injuries were found. Only one of the injuries (L4) was related to the malposition of a screw. CONCLUSIONS This study has shown that percutaneous insertion of pedicle screws in the lumbar spine is a safe and reliable technique. Despite the low misplacement rate of only 6.6%, it should be kept in mind that the surgical procedure is technically demanding and should be performed only by experienced spine surgeons.

Neural driven angiogenesis by overexpression of nerve growth factor.

Mechanisms regulating angiogenesis are crucial in adjusting tissue perfusion on metabolic demands. We demonstrate that overexpression of nerve growth factor (NGF) in brown adipose tissue (BAT) of NGF-transgenic mice elevates both mRNA and protein levels of vascular endothelial growth factor (VEGF) and VEGF-receptors. Increased vascular permeability, leukocyte–endothelial interactions (LEI), and tissue perfusion were measured using intravital microscopy. NGF-stimulation of adipocytes and endothelial cells elevates mRNA expression of VEGF and its receptors, an effect blocked by NGF neutralizing antibodies. These data suggest an activation of angiogenesis as a result of both: stimulation of adipozytes and direct mitogenic effects on endothelial cells. The increased nerve density associated with vessels strengthened our hypothesis that tissue perfusion is regulated by neural control of vessels and that the interaction between the NGF and VEGF systems is the critical driver for the activated angiogenic process. The interaction of VEGF- and NGF-systems gives new insights into neural control of organ vascularization and perfusion.

Sequential changes in vessel formation and micro-vascular function during bone repair

Background Angiogenesis, the process of new vessel formation from a pre-existing vascular network, is essential for bone development and repair. New vessel formation and microvascular functions are crucial during bone repair, not only for sufficient nutrient supply, transport of macromolecules and invading cells, but also because they govern the metabolic microenvironment. Despite its central role, very little is known about the initial processes of vessel formation and microvascular function during bone repair. Methods To visualize and quantify the process of vessel formation and microvascular function during bone repair, we transplanted neonatal femora with a substantial defect into dorsal skin-fold chambers in severe combined immunodeficient (SCID) mice for continuous noninvasive in-vivo evaluation. We employed intravital microscopic techniques to monitor effective microvascular permeability, functional vascular density, blood flow rate and leukocyte flux repeatedly over 16 days. Oxytetracyclin and v. Kossa/v. Giesson staining was performed to quantify the calcification process in vivo and in vitro. Results Development of a hematoma surrounding the defect area was the initial event, which was accompanied by a significant increase in microvascular permeability and blood flow rate. With absorption of the hematoma and vessel maturation, permeability decreased continuously, while vascular density and tissue perfusion increased. Histological evaluation revealed that the remodeling of the substantial defect prolonged the in-vivo monitored calcification process. Interpretation The size of the initial substantial defect correlated positively with increased permeability, suggesting improved release of permeability-inducing cytokines. The unchanged permeability in the control group with boiled bones and a substantial defect corroborated these findings. The adaptation to increasing metabolic demands was initially mediated by increased blood flow rate, later with increasing vascular density through increased tissue perfusion rate. These insights into the sequence of microvascular alterations may assist in the development of targeted drug delivery therapies and caution against the use of permeability-altering drugs during bone healing.

Computer navigation of parapedicular screw fixation in the thoracic spine: a cadaver study.

Study Design. An in vitro study to investigate the advantages of computer assistance for the purpose of parapedicular screw fixation in the upper and middle thoracic spine. Objectives. To evaluate the feasibility and application accuracy of parapedicuar screw insertion with the assistance of an optoelectronic navigation system. Summary of Background Data. Because of anatomic limitations, thoracic pedicle screw insertion in the upper and middle thoracic spine remains a matter of controversy. The technique of parapedicular screw insertion has been described as an alternative, although the exact screw position is difficult to control. With the assistance of computer navigation for the screw placement, it might become possible to overcome these challenges. Methods. Four human specimens were harvested for this study; 6-mm screws were inserted from T2 to T8 with the assistance of a CT-based optoelectronic navigation system. During surgery virtual images of the screw position were documented and compared with postoperative contact radiographs to determine the application accuracy. The following measurements were obtained: axial and sagittal screw angles as well as the screw distances to the anterior vertebral cortex and the medial pedicle wall. Results. All 54 screws were inserted in a parapedicular technique without violation of the medial pedicle wall or the anterior or lateral vertebral cortex. The mean ± standard deviation difference between the virtual images and the radiographs was 1.0 ± 0.94 mm for the distance to the medial pedicle wall and 1.9 ± 1.44 mm for the distance to the anterior cortex. The angular measurements showed a difference of 1.6 ± 1.1° for the transverse screw angle and 2.1 ± 1.6° for the sagittal screw orientation. Conclusion. With the assistance of computer navigation it is possible to achieve a safe and reliable parapedicular screw insertion in the upper and middle thoracic spine in vitro. The application accuracy varies for the linear and angular measurements and is higher in the axial than in the sagittal plane. It is important for the surgeon to understand these limitations when using computer navigation in spinal surgery.

Chemokine profile of disc degeneration with acute or chronic pain

OBJECT Disc-related disorders such as herniation and chronic degenerative disc disease (DDD) are often accompanied by acute or chronic pain. Different mediators have been identified in the development of radicular pain and DDD. Previous studies have not analyzed individual cytokine profiles discriminating between acute sciatic and chronic painful conditions, nor have they distinguished between different anatomical locations within the disc. The aim of this study was to elucidate the protein biochemical mechanisms in DDD. METHODS The authors determined expression levels of matrix metalloproteinase-3, transforming growth factor-β (TGF-β), tumor necrosis factor-α, interleukin-1α, and pro-substance P using enzyme-linked immunosorbent assay and Western blot analyses in patients suffering from DDD (n = 7), acute back pain due to herniated discs with radiculopathy (n = 7), and a control group (n = 7). Disc tissue samples from the anulus fibrosus (AF) and nucleus pulposus (NP) were analyzed. Statistical analysis was performed using nonparametric tests. RESULTS A distinct distribution of cytokines was found in different anatomical regions of intervertebral discs in patients with DDD and herniated NP. Increased TGF-β levels were predominantly found in DDD. Matrix metalloproteinase-3 was increased in acute herniated disc material. Increased levels of substance P were found in patients suffering from DDD but not in patients with disc herniation. The data showed significantly higher levels of proinflammatory cytokines in the AF and NP of patients with DDD, and the expression levels in the AF were even higher than in the NP, suggesting that the inflammatory response initiates from the AF. CONCLUSIONS These results highlight the complex mechanisms involved during disc degeneration and the need to distinguish between acute and chronic processes as well as different anatomical regions, namely the AF and NP. They also highlight potential problems in disc nucleus replacement therapies because the results suggest a biochemical link between AF and NP cytokine expression.

Rheumatoid arthritis of the cervical spine. Current concepts for diagnosis and therapy

The involvement of the cervical spine in patients with rheumatoid arthritis (RA) is common,and has recently received growing attention. In the early stage of the disease, there is an isolated atlantoaxial subluxation (AAS). With further progression, osseous destruction of the joints can lead to vertical instability. While the involvement of the middle and lower cervical spine can cause a subaxial instability, neurological deficits can occur at any time. The onset of cervical myelopathy in patients with RA is often missed because of additional problems related to the hands and feet. If patients show clear symptoms of cervical myelopathy, the progression of the disease cannot be stopped by conservative treatment. Other indications for operative treatment are severe pain and radiological evidence of progressive instability. In the case of an isolated AAS, fusion can be restricted to the C1/C2 segment. If there is evidence for vertical or subaxial instability, an occipitocervical fusion has to be performed. To avoid instability adjacent to the fusion, the surgeon must check for signs of potential subaxial instability. If this is the case, fusion should include the entire cervical spine. Additional transoral decompression may be necessary when there is persistent retrodental pannus or osseous compression by an irreducible transverse dislocation or cranial migration of the dens. Non-ambulatory myelopathic patients are more likely to present severe surgical complications with limited prospects of functional recovery. Therefore, it is important to avoid the development of severe cervical myelopathy by early surgical intervention.ZusammenfassungDie Beteiligung der Halswirbelsäule (HWS) im Rahmen der rheumatoiden Arthritis (RA) ist häufig und hat zunehmend an Bedeutung gewonnen. Am Anfang steht dabei meist die isolierte atlantoaxiale Subluxation. Durch eine knöcherne Destruktion der Gelenke kann es zu einer vertikalen Instabilität kommen. Eine Beteiligung der mittleren und unteren HWS wird als subaxiale Instabilität bezeichnet. Neurologische Störungen können zu jedem Zeitpunkt der Erkrankung auftreten. Der Beginn der zervikalen Myelopathie wird beim Rheumatiker aufgrund der zusätzlichen Manifestationen an Händen und Füßen leider häufig übersehen.Hat sich eine Myelopathie bereits klinisch eindeutig manifestiert, so ist der weitere progressive Verlauf mit konservativen Mitteln nicht mehr aufzuhalten.Eine Operationsindikation besteht neben der beginnenden Myelopathie auch bei therapierefraktären Schmerzzuständen, sowie dem radiologischen Nachweis einer progredienten Instabilität. Im Falle einer isolierten atlantoaxialen Subluxation kann die Fusion auf dieses Segment beschränkt werden,was häufig einer weiteren rheumatischen Destruktion der HWS vorbeugt.Im Falle einer vertikalen Instabilität oder einer subaxialen Beteiligung ist eine kraniozervikale Fusion notwendig.Dabei sollte präoperativ sorgfältig nach einer potentiellen subaxialen Instabilität gefahndet werden. Lässt sich eine solche nachweisen, ist die Fusion auf die gesamte HWS auszudehnen. Im Falle einer anhaltenden Weichteilkompression oder knöchernen ventralen Raumforderung ist gelegentlich eine zusätzliche transorale Dekompression notwendig. Besteht bereits eine fortgeschrittene neurologische Schädigung mit Verlust der Gehfähigkeit erhöhen sich die perioperative Morbidität und Mortalität erheblich.Das vorrangige Ziel des betreuenden Arztes sollte deshalb die Vermeidung solcher fortgeschrittenen zervikalen Destruktionen sein. Dies ist jedoch nur durch eine rechtzeitige und konsequente operative Behandlung möglich.AbstractThe involvement of the cervical spine in patients with rheumatoid arthritis (RA) is common,and has recently received growing attention. In the early stage of the disease, there is an isolated atlantoaxial subluxation (AAS). With further progression, osseous destruction of the joints can lead to vertical instability. While the involvement of the middle and lower cervical spine can cause a subaxial instability, neurological deficits can occur at any time. The onset of cervical myelopathy in patients with RA is often missed because of additional problems related to the hands and feet. If patients show clear symptoms of cervical myelopathy, the progression of the disease cannot be stopped by conservative treatment.Other indications for operative treatment are severe pain and radiological evidence of progressive instability. In the case of an isolated AAS, fusion can be restricted to the C1/C2 segment. If there is evidence for vertical or subaxial instability, an occipitocervical fusion has to be performed.To avoid instability adjacent to the fusion, the surgeon must check for signs of potential subaxial instability. If this is the case, fusion should include the entire cervical spine. Additional transoral decompression may be necessary when there is persistent retrodental pannus or osseous compression by an irreducible transverse dislocation or cranial migration of the dens. Non-ambulatory myelopathic patients are more likely to present severe surgical complications with limited prospects of functional recovery. Therefore, it is important to avoid the development of severe cervical myelopathy by early surgical intervention.

Minimal-invasive stabilization and circumferential spinal cord decompression in metastatic epidural spinal cord compression (MESCC)

Surgery with instrumentation to the spine has been shown to provide excellent pain relief, stabilization and quality of life in patients with spinal metastasis [1, 4, 12, 13, 15]. Surgery may also offer superior outcomes to other treatments, such as radiation in cases of acute spinal cord compression and neurological deficits [7, 11]. In comparison to degenerative spinal disorders [5], there is little data on the use of minimally invasive surgery (MIS) as an alternative to open approaches for spinal metastatic surgery [9]. The benefits of MIS in spinal surgery compared to open approaches include reduction in muscular trauma, blood loss, cost and hospital stay [3, 6, 10, 14]. Here we present a surgical technique of posterior percutaneous instrumentation with minimal-invasive circumferential spinal cord decompression and subsequent thoracoscopically reconstruction of the anterior vertebral column with an expandable titanium cage.

Percutaneous scoliosis surgery

The development and use of percutaneous or minimalinvasive surgical techniques seems to be a natural course that arises from the desire to avoid unnecessary insult to structures not involved in the pathology. In spinal surgery these techniques have been mostly limited to decompression procedures of neural structures by the use of tubular retractors. Because of this limited indication spectrum, minimal-invasive techniques have been considered to ignore the overlying deformity. Further to the development of new implants, posterior minimal-invasive instrumentation has become available for the treatment of lumbar instabilities. However, the treatment of deformities requiring multisegmental instrumentation for the deformity correction and the correction manoeuvre itself, along with the fusion technique are associated with a different approach to the pathology [1–5]. The present article describes the technique and the rational of combining a concave side anterior release with interbody fusion and indirect neuroforaminal decompression, together with a percutaneous posterior instrumentation and deformity correction in patients with rigid adult scoliosis. This type of technique may also be used for the treatment of idiopathic scoliosis.

Therapie der zervikalen rheumatoiden Arthritis

Zusammenfassung.Der rheumatische Befall der Halswirbelsäule kann in drei Stadien eingeteilt werden. Am Anfang steht zumeist die isolierte atlantoaxiale Subluxation (AAS), gefolgt von der vertikalen Instabilität und der subaxialen Instabilität. Eine zervikale Myelopathie kann dabei in jedem Stadium der rheumatischen Destruktion auftreten. Bei klinisch manifester Myelopathie ist der weitere progressive Verlauf ohne Operation nicht mehr aufzuhalten. Insbesondere zu Beginn der Erkrankung hat die konservative Therapie einen hohen Stellenwert. Neben der Patientenaufklärung ist durch die Ruhigstellung mittels Halskrawatte, sowie eine gezielte Physiotherapie eine Besserung der Schmerzsymptomatik zu erwarten. Eine frühzeitige und effektive DMARD-Medikation kann zu einer positiven Beeinflussung des natürlichen Krankheitsverlaufes führen. Bei progredienter Instabilität, beginnender Myelopathie oder therapierefraktären Beschwerden ist eine operative Behandlung indiziert. Eine atlantoaxiale Fusion sollte bei isolierter AAS durchgeführt werden. Operationsmethode der Wahl ist die transartikuläre Verschraubung nach Magerl. Bei Nachweis einer vertikalen Instabilität oder fortgeschrittener Destruktion der C0/C1-Gelenke ist eine kraniozervikale Fusion notwendig. Dabei sollte präoperativ nach einer potentiellen subaxialen Instabilität gesucht werden. Bei positivem Nachweis ist die Fusion auf die gesamte HWS auszudehnen. Eine transorale Dekompression ist nur bei anhaltender ventraler Myelonkompression notwendig, was typischerweise bei der fixierten AAS der Fall ist. Besteht bereits eine fortgeschrittene neurologische Schädigung mit Verlust der Gehfähigkeit erhöhen sich die perioperative Morbidität und Mortalität erheblich. Solche fortgeschritten Stadien der komplexen zervikalen Destruktion sollten deshalb durch eine frühzeitige operative Behandlung vermieden werden. Die Wahl des richtigen Operationszeitpunktes ist allerdings weiterhin umstritten. Zukünftige prospektiv, randomisierte Studien müssen deshalb diese Fragestellung aufgreifen, damit die Therapiekonzepte für die rheumatische HWS verbessert werden können.Summary.The rheumatoid involvement of the cervical spine can be divided into three phases. In the early stage of the disease there is an isolated atlantoaxial subluxation (AAS), followed by vertical instability and subaxial instability. If patients show clear symptoms of cervical myelopathy, which can occur during any stage of the disease, the progression cannot be stopped by conservative treatment, which is of great importance at the beginning of the cervical manifestation. Patient education, physiotherapy and immobilization with a stiff collar can significantly reduce pain. Early and effective DMARD therapy can have a positive effect on the natural history of the disease. In case of progressive instability, cervical myelopathy or severe pain operative treatment is indicated. If there is an isolated AAS, fusion can be restricted to the C1/C2 segment. The Magerl transarticular screw fixation is the preferred technique for stabilization. If there is evidence for vertical instability or severe destruction of the C0/C1 joints, occipital cervical fusion has to be performed. Durin the preoperative planning it is necessary to look for signs of subaxial instability. If this is the case, fusion should include the entire cervical spine. Transoral decompression may be necessary when there is persistent anterior compression of the myelon, typically seen in fixed AAS. Non-ambulatory myelopathic patients are more likely to develop severe surgical complications. Therefore, it is important to avoid the development of severe cervical instability by early surgical intervention. The right timing for surgery is still a matter of controversy. Future prospective randomized trials should address this topic to improve the treatment concept for the rheumatoid patient.

Percutaneous multilevel reconstruction in revision surgery.

Minimal-invasive spine surgery has become a widely accepted surgical technique not only for decompression procedures but also for stabilisation of the spinal column. Percutaneous stabilisation techniques are either used to achieve fusion, e.g. in degenerative spine surgery when combined with fusion techniques, or in stabilisation only procedures in patients suffering from tumor or infection associated instability. While initial MIS procedures proved their feasibility, safety and benefit, strategies for revision surgery are still lacking. Yet with an increasing number of MIS procedures performed, revision strategies become more significant. Not only because the natural course involves additional segments but also because of potential implant failure and adjacent level disease [1–4]. Case description