F. Cumhur Oner

Complications of artificial disc replacement: a report of 27 patients with the SB Charité disc.

Disc prosthesis surgery is rapidly becoming an option in treating patients with symptomatic degenerative disc disease. Only short-term and midterm results are described in the literature. Most operated patients belong to the age group of 30–50 years. In these active patients, complications can be expected to increase with longer follow-up, similar to total joint replacements in the extremities. Reported here is a series of 27 patients from another institution, who presented with unsatisfactory results or complications after SB Charité disc replacement. The objective of this work was to describe the possible short- and long-term unsatisfactory results of disc prosthesis surgery. Twenty-seven patients were seen in a tertiary university referral center with persisting back and leg complaints after having received a Charité disc prosthesis. All patients were operated on in a neighboring hospital. Most patients were operated on at the L4–L5 and /or the L5–S1 vertebral levels. The patients were evaluated with plain radiography, some with flexion-extension x-rays, and most of them with computed tomography scans. The group consisted of 15 women and 12 men. Their mean age was 40 years (range 30–67 years) at the time of operation. The patients presented to us a mean of 53 months (range 11–127 months) following disc replacement surgery. In two patients, an early removal of a prosthesis was required and in two patients a late removal. In 11 patients, a second spinal reconstructive salvage procedure was performed. Mean follow-up for 26 patients with mid- and long-term evaluation was 91 months (range 15–157 months). Early complications were the following: In one patient, an anterior luxation of the prosthesis after 1 week necessitated removal and cage insertion, which failed to unite. In another patient with prostheses at L4–L5 and L5–S1, the prosthesis at L5–S1 dislocated anteriorly after 3 months and was removed after 12 months. Abdominal wall hematoma occurred in four cases. Retrograde ejaculation with loss of libido was seen in one case and erection weakness in another case. A temporary benefit was experienced by 12 patients, while 14 patients reported no benefit at all. Main causes of persistent complaints were degeneration at another level in 14, subsidence of the prosthesis in 16, and facet joint arthrosis in 11. A combination of pathologies was often present. Slow anterior migration was present in two cases, with compression on the iliac vessels in one case. Polyethylene wear was obvious in one patient 12 years after operation. In eight cases, posterior fusion with pedicle screws was required. In two cases, the prosthesis was removed and the segment was circumferentially fused. These procedures resulted in suboptimal long-term results. In this relatively small group of patients operated on with a Charité disc prosthesis, most problems arose from degeneration of other lumbar discs, facet joint arthrosis at the same or other levels, and subsidence of the prosthesis. It is to be expected that many more patients will be seen with late problems some years after this operation as the survivorship will decrease with time.

Organ printing: the future of bone regeneration?

In engineered bone grafts, the combined actions of bone-forming cells, matrix and bioactive stimuli determine the eventual performance of the implant. The current notion is that well-built 3D constructs include the biological elements that recapitulate native bone tissue structure to achieve bone formation once implanted. The relatively new technology of organ/tissue printing now enables the accurate 3D organization of the components that are important for bone formation and also addresses issues, such as graft porosity and vascularization. Bone printing is seen as a great promise, because it combines rapid prototyping technology to produce a scaffold of the desired shape and internal structure with incorporation of multiple living cell types that can form the bone tissue once implanted.

Sustained release of BMP-2 in bioprinted alginate for osteogenicity in mice and rats

The design of bioactive three-dimensional (3D) scaffolds is a major focus in bone tissue engineering. Incorporation of growth factors into bioprinted scaffolds offers many new possibilities regarding both biological and architectural properties of the scaffolds. This study investigates whether the sustained release of bone morphogenetic protein 2 (BMP-2) influences osteogenicity of tissue engineered bioprinted constructs. BMP-2 loaded on gelatin microparticles (GMPs) was used as a sustained release system, which was dispersed in hydrogel-based constructs and compared to direct inclusion of BMP-2 in alginate or control GMPs. The constructs were supplemented with goat multipotent stromal cells (gMSCs) and biphasic calcium phosphate to study osteogenic differentiation and bone formation respectively. BMP-2 release kinetics and bioactivity showed continuous release for three weeks coinciding with osteogenicity. Osteogenic differentiation and bone formation of bioprinted GMP containing constructs were investigated after subcutaneous implantation in mice or rats. BMP-2 significantly increased bone formation, which was not influenced by the release timing. We showed that 3D printing of controlled release particles is feasible and that the released BMP-2 directs osteogenic differentiation in vitro and in vivo.

Prolonged presence of VEGF promotes vascularization in 3D bioprinted scaffolds with defined architecture

Timely vascularization is essential for optimal performance of bone regenerative constructs. Vascularization is efficiently stimulated by vascular endothelial growth factor (VEGF), a substance with a short half-life time. This study investigates the controlled release of VEGF from gelatin microparticles (GMPs) as a means to prolong VEGF activity at the preferred location within 3D bioprinted scaffolds, and the effects on subsequent vascularization. The release of VEGF from GMPs was continuous for 3 weeks during in vitro studies, and bioactivity was confirmed using human endothelial progenitor cells (EPCs) in migration assays. Traditional and real-time migration assays showed immediate and efficient EPC migration in the presence of GMP-released VEGF, indistinguishable from VEGF-solution that was added to the medium. Matrigel scaffolds containing EPCs and VEGF, which was released either in a fast or sustained fashion by application of GMPs, were investigated for their in vivo vasculogenic capacity. Implantation in subcutaneous pockets in nude mice for one week demonstrated that vessel formation was significantly higher in the VEGF sustained-release group compared to the fast release group. In addition, regional differences with respect to VEGF release were introduced in 3D bioprinted EPC-laden scaffolds and their influence on vasculogenesis was investigated in vivo. The different regions were retained and vessel formation occurred analogous with the results seen in the Matrigel plugs. We conclude that GMPs are suitable to generate sustained release profiles of bioactive VEGF, and that they can be used to create defined differentiation regions in 3D bioprinted heterogeneous constructs, allowing a new generation of smart scaffold design. The prolonged presence of VEGF led to a significant increase in scaffold vascularization when applied in vivo.

Recurrent kyphosis after posterior stabilization of thoracolumbar fractures: 24 cases treated with a Dick internal fixator followed for 1.5-4 years

24 patients with Th12-L1 fractures treated with a Dick internal fixator were analyzed to assess predictors of poor outcome. 4 patients had fixation without bone transplantation, 20 patients had a posterior fusion, and 12 of them had additional transpedicular spongioplasty. There were fractures of the transpedicular screws in 4 and screw migration in 2 cases. The increase in the local kyphosis angle was greater than the increase in the anterior compression angle and this did not correlate with spongioplasty or fusion. Fixation failure was in all cases related to a disproportionate increase in the local kyphosis angle. There was no difference between the patients with transpedicular spongioplasty and posterior fusion and the other patients with respect to results and complications. Bony collapse was not the major cause of failure and consequently there was no measureable contribution of transpedicular spongioplasty. We found that the Dick internal fixator for unstable fractures was associated with a higher complication rate than earlier reported.

The incidence of donor site pain after bone graft harvesting from the posterior iliac crest may be overestimated : A study on spine fracture patients

Study Design. A retrospective cohort study on patients with traumatic vertebral fractures who underwent fusion with iliac crest bone. Objective. To evaluate the influence of low back surgery on donor site attributed pain, we compared donor site pain between patients who underwent high and low level fusions. Summary of Background Data. The most common complication of posterior iliac crest bone graft harvesting is postoperative pain at the donor site. The incidence of donor site pain after bone graft harvesting from the posterior iliac crest is mainly reported from studies in patients who underwent low lumbar or lumbosacral surgery. The close proximity of the primary surgery to the iliac crest could interfere with the reported incidence of donor site pain. Methods. Questionnaires regarding the iliac crest morbidity were sent to patients who underwent instrumented posterolateral fusion after traumatic spinal fractures. The incidence of donor site attributed pain was compared between patients whose fusion was between T2 and L2, with patients whose fusion extended to L3 or more caudally. Results. In patients with a fusion of high levels, the donor site pain was significantly lower compared with patients with fusion of low levels (14.3% vs. 40.9%). Conclusion. Patients probably cannot differentiate between donor site pain and residual low back pain. The reported incidence of pain related to posterior iliac crest bone graft harvesting may therefore be overestimated.

Therapeutic decision making in thoracolumbar spine trauma.

Study Design. Systematic literature review. Objective. A systematic review was designed to answer 3 primary research questions: (1) What is the most useful classification system for surgical and nonsurgical decision-making with regard to thoracolumbar (TL) spine injuries? (2) For a TL burst fracture with incomplete neurologic deficit, what is the optimal surgical approach and stabilization technique? (3) Is complete disruption of the posterior ligamentous complex an indication for surgical intervention for TL burst fractures? Summary of Background Data. Despite a long history of descriptive and clinical series, there remains considerable controversy and wide variation in the treatment of traumatic TL spine injuries. Methods. A comprehensive search of the English literature was conducted using Medline and the Cochrane Database of Systematic Reviews. Standardized grading systems were used to assess the level of evidence and quality of articles impacting the research questions. Results. Recommendations for the primary research questions were as follows: (1) Thoracolumbar Injury Classification System seems to be the best system available for therapeutic decision-making for TL spine injuries (strength of recommendation: weak; quality of evidence: low). (2) There is no specific surgical approach in the case of a TL burst fracture with incomplete neurologic deficit that has any advantage with regard to neurologic recovery (strength of recommendation: weak; quality of evidence: low). (3) Complete disruption of the posterior ligamentous complex as determined collectively by morphologic criteria using plain radiographs and computed tomography is an indication for surgical intervention in TL burst fractures (strength of recommendation: strong; quality of evidence: low). Conclusion. Based on this systematic review of the literature only very low to moderate quality studies could be identified to address clinical questions related to TL spine trauma. These findings suggest the need for further study, including emphasis on higher quality studies.

Cement augmentation techniques in traumatic thoracolumbar spine fractures

Study Design. Review of human cadaveric and in vivo animal studies and clinical trial. Objective. To develop less invasive surgical techniques for reconstruction of the anterior column in thoracolumbar fractures. Summary of Background Data. Persistent central endplate depression can cause anterior column insufficiency after posterior surgery for traumatic thoracolumbar fractures. Reduction of the central endplate followed by intravertebral cement augmentation could restore weight-bearing capacity. Materials and Methods. In human cadaveric burst fracture models, balloon-assisted endplate reduction (BAER) and vertebroplasty techniques have been investigated in terms of their safety and biomechanical properties. The histologic properties of different cement polymers were studied in an animal vertebral body and endplate defect model. In addition, the clinical outcome of percutaneous cement augmentation in the setting of a burst fracture examining the BAER technique and vertebroplasty with adjunctive posterior pedicle screw fixation is reviewed. Results. These techniques have proven to be safe and effective, although cement leakage outside the confines of the vertebral body may occur. Calcium phosphate cements are preferable over methylmethacrylate because of their in vivo histologic properties. Using the BAER technique and posterior pedicular fixation, anterior vertebral height restoration is possible. Following balloon removal, some loss of fracture height restoration is observed. Further loss of vertebral height reduction was not observed following cement curing clinically. Conclusions. These studies show that less invasive anterior vertebral reconstruction using percutaneous cement augmentation techniques is feasible following traumatic vertebral fractures.

Optimization of bone tissue engineering in goats: A peroperative seeding method using cryopreserved cells and localized bone formation in calcium phosphate scaffolds

Background. Bone tissue engineering by combining cultured bone marrow stromal cells with a porous scaffold is a promising alternative for the autologous bone graft. Drawbacks of the technique include the delay necessary for cell culture and the complicated logistics. We investigated methods to bypass these drawbacks. Furthermore, we investigated the localization of bone formation inside the scaffold. Methods. Bone marrow stromal cells from seven goats were culture expanded and cryopreserved. One week before surgery, some of the cells were thawed, cultured, and seeded on porous calcium phosphate scaffolds. The constructs were cultured for another week until implantation. The remaining cryopreserved cells were thawed just before implantation and peroperatively resuspended in plasma before combining with the scaffold. Scaffolds impregnated with fresh bone marrow, devitalized cultured constructs, and empty scaffolds served as controls. All samples were implanted in the back muscles of the goats for 9 weeks. Results. Histologic examination showed minimal (<1%) bone in the empty and devitalized scaffolds, 4.2±5.1 bone area percent in the bone marrow samples, and significantly more bone in both the cultured and peroperatively seeded constructs (11.7±2.5 and 14.0±2.0%). The peripheral 350 &mgr;m of the implants contained significantly less bone. Conclusion. Peroperative preparation of osteogenic constructs with cryopreserved cells is feasible. These constructs yield substantially more bone than the scaffolds alone or scaffolds impregnated with fresh bone marrow. Bone deposition is much less on the scaffold periphery.

Diffuse idiopathic skeletal hyperostosis of the cervical spine: an underestimated cause of dysphagia and airway obstruction

BACKGROUND CONTEXT Diffuse idiopathic skeletal hyperostosis (DISH) is a common but underdiagnosed condition relating to ossification of spinal ligaments that can cause compression of the esophagus and trachea. According to case reports, dysphagia or airway obstruction resulting from DISH is a rare occurrence. PURPOSE This study was intended to identify all published cases of dysphagia and/or airway obstruction resulting from DISH to increase the epidemiologic/clinical knowledge of these related conditions. STUDY DESIGN A systematic review of the literature was performed. METHODS The articles resulting from the systematic PubMed/EMBASE search of the literature were closely read, and predefined parameters were scored. RESULTS The search yielded a total of 118 articles (95 case reports and 23 case series) describing 204 patients with dysphagia and/or airway obstruction resulting from DISH. The number of cases demonstrated a steady increase from 1980 to 2009. This might be a real effect not ascribable to publication bias or expansion of the medical literature alone. CONCLUSIONS Diffuse idiopathic skeletal hyperostosis as a cause of dysphagia and/or airway obstruction may be an increasing and underappreciated phenomenon. Diffuse idiopathic skeletal hyperostosis should be included in the differential diagnosis of dysphagia and airway obstruction.