Does sagittal position of the CTDR-related centre of rotation influence functional outcome? Prospective 2-year follow-up analysis.

PURPOSE: Recent studies describe significant rates of heterotopic ossification (HO) after cervical total disc replacement (CTDR). Little is known about the reasons, and one aspect that requires further in vivo investigation is the biomechanical alteration after CTDR and the role of the implant-related centre of rotation (CORi) in particular. The role of the sagittal position of the CORi on functional outcome in two versions of a semi-constrained disc prosthesis with sagittally different CORi is the topic of this study. METHODS: Patients were candidates for single-level CTDR between C3 and C7 who suffered from CDDD and received a standard or flat version of activ C™ (Aesculap AG, Tuttlingen). Clinical and radiographic assessments were determined preoperatively, intraoperatively, at discharge and again at 6 weeks, 6 months, 1 and 2 years. Radiographic examinations were performed independently using specialized quantitative motion analysis software. RESULTS: Clinical outcome improved significantly regarding NDI as well as VAS on neck and arm pain with no differences in mean improvement by study group. Segmental angle measures show a significantly better lordotic alignment for both groups after surgery, but the degree of correction achieved is higher in the flat group. Correlation analysis proves that the more anterior the CORi is positioned, the higher the lordotic correction is achieved (Pearson rho -0.385). Segmental ROM decreased in the standard group but was maintained for flat implants. At present, our data do not demonstrate a correlation between CORi and ROM at 2 years. Two years after surgery, severe HO grade III-IV was present in 31.6 % standard and 13.1 % flat cases with significant differences. Grouping according to HO severity showed comparable sagittal positions of CORi for flat implants but a more posterior position in the severe HO group for standard implants. CONCLUSIONS: Our results confirm the influence of CORi location on segmental alignment, kinematics and HO for a semi-constrained CTDR, but it also indicates a multifactorial process.

Effect of degeneration on gene expression of chondrogenic and inflammatory marker genes of intervertebral disc cells: a preliminary study.

AIM: New techniques for biological repair in the treatment of degenerative disc disease (DDD) have been developed recently. The question arises whether it is possible to find a predictive marker to identify a patient population which could benefit from this new treatment option. Standard magnetic resonance imaging (MRI) fails to differentiate between pathologic painful and asymptomatic aging discs. Neurological symptoms contribute to identifying the pathological level. In this preliminary translational research study we analysed the gene expression of structure proteins and inflammatory mediators as well as histological features of lumbar intervertebral discs in symptomatic patients with various signs of degeneration in the MRI. METHODS: Specimens of intervertebral disc tissue were obtained from 20 patients undergoing lumbar nucleotomy. Preoperatively, a group selection based on four pre-defined MRI-criteria was performed: Group 1 (mild signs of degeneration), group 2 (moderate), group 3 (moderate-severe), group 4 (severe). RESULTS: An increase of the expression of structural proteins and inflammatory markers could be observed in MRI-groups 2 and 3. Gene expression of collagen type I and II and aggrecan went along with levels of cyclooxygenase-2 (COX-2) and (fibroblast growth factor-2) FGF-2 expression. Histological examination showed signs of granulation tissue in only 35% of cases, but no differences between the groups. CONCLUSION: Our findings implicate that the gene expression of structural proteins might correlate with the appearance of inflammatory mediators in symptomatic patients with moderate disc changes in the MRI in this preliminary clinical subset. The assessment of cell activity and protein expression in a larger number of patients could be next step to support and supplement the present data.

Bone grafting and substitutes in spine surgery.

The increase of spinal procedures over the last decades has made the long-term problems, such as pseudarthrosis, apparent. This demands optimized strategies, techniques and technologies. Modern fixation systems have been developed as an adjunct to spinal fusion, and several generations of different synthetic cages have proved to be reasonable alternatives to autologous bone or allografts. The development of recombinant bone morphogenetic proteins (BMPs) is of promise, because of their great osteoinductive capabilities. While spine surgeons are familiar with autologous and synthetic grafts as well as allografts, these comparably new evolving growth-factor-based technologies are of high interest. This was a selective literature review. Alternatives to autologous grafts include allograft bone, synthetic cages and growth-factor based bone substitutes, BMPs being the most-studied among them. Autologous iliac crest alone provides all of the required capabilities of an ideal bone graft, i.e. osteoconduction, osteoinduction, osteogenesis, but each of the alternatives can produce excellent results in a number of indications. If combined, these alternatives can cumulatively provide all required graft capabilities. Nevertheless, all of the available grafts have specific characteristics and can feature certain complications. Alternatives to autologous grafts circumvent donor-site morbidity and are available in a larger amount than autologous bone for extensive surgery. New technologies offer excellent possibilities of new bone formation, but there are also severe risks and high costs to be considered. The indication for bone grafting must be clearly defined, the graft selection should be individually adapted, and the risks, efforts and costs of the selected fusion procedure should be carefully considered.

Cages with fixation wings versus cages plus plating for cervical reconstruction after corpectomy - is there any difference?

AIM: Different expandable and non-expandable fusion cages have gained acceptance in spinal surgery. We compared the radiological outcome of titanium cages with mounted wings to cages with additional anterior plating. METHODS: We performed a retrospective study of 44 patients after single or two-level cervical corpectomy. For reconstruction of the anterior column two different anterior distraction devices (ADD) were used: cage plus ventral plating (16 cases, ADD group) or cage with fixation wings (28 cases, ADDplus group). Clinical and radiological evaluations were performed after 1 week, 6 months and 12 months. Cervical lordosis, the angle between the adjacent vertebral bodies, the settling ratio, fusion rates, stability, neurological outcome and complications were assessed to compare both groups. RESULTS: Both groups had similar final clinical but different radiological outcomes. The fusion rate was 100% in the ADD group and 89% in the ADDplus group. Furthermore, the relative loss of cervical lordosis after 12 months was higher in the ADDplus group (-6.9% vs. -1.6%). The loss of correction of the relative rotation angle of the operated segment was also higher in the ADDplus group (-4.3 degrees vs. -1.7 degrees). Additional surgery was necessary in three cases in the ADDplus group. CONCLUSIONS: This study demonstrates that expandable cages are useful vertebral body replacements, because they can be adjusted to the size of the corpectomy in situ and provide immediate strong anterior column support avoiding bone graft site morbidity. The direct attachment of fixation wings to the cage simplifies the operative procedure but carries a significantly higher risk of non-fusion, loss of lordotic correction and height.

[Spinal disorders and associated CNS anomalies - tethered cord and Arnold-Chiari malformation]. / Wirbelsäulenerkrankungen und assoziierte ZNS-Fehlbildungen - Tethered-Cord und Arnold-Chiari-Fehlbildung.

Tethered cord syndrome (TCS) and the Chiari malformation (CM) are generally related to congenital malformations, but both entities can be acquired.TCS often presents with progressing sensory and motor symptoms that can be attributed to increased tension of the spinal cord. Fixation of the spinal cord can occur congenitally (primary TCS) or in association with other intraspinal pathologies or postoperative scarring (secondary TCS). Exact diagnosis in the adult can be difficult if symptoms are interpreted as being related to degenerative disorders of the spine. In the presence of neurological symptoms, surgery is indicated. A preventive surgical procedure in asymptomatic patients is discussed controversially in the literature and is established in TCS patients only with correction of a scoliosis. However, most patients suffering from TCS benefit from surgical treatment.CM can be divided into four abnormal alterations of the posterior fossa, with most cases being of types I and II. In adults, Chiari type I is most common. Chiari I may present congenitally; however, it is also secondarily observed following lumboperitoneal shunting or in association with hydrocephalus. Surgical intervention is recommended depending on the extent of herniated tissue and the neurological symptoms. The optimal surgical procedure is still controversial. Most centers recommend bony decompression with dural graft extension for Chiari I.The appropriate treatment of both complex disorders requires a close and critical interdisciplinary approach in order to offer patients an individually adapted therapy.