Abraham J. Verbout

Three-Dimensional Fiber Deposition of Cell-Laden, Viable, Patterned Constructs for Bone Tissue Printing

Organ or tissue printing, a novel approach in tissue engineering, creates layered, cell-laden hydrogel scaffolds with a defined three-dimensional (3D) structure and organized cell placement. In applying the concept of tissue printing for the development of vascularized bone grafts, the primary focus lies on combining endothelial progenitors and bone marrow stromal cells (BMSCs). Here we characterize the applicability of 3D fiber deposition with a plotting device, Bioplotter, for the fabrication of spatially organized, cell-laden hydrogel constructs. The viability of printed BMSCs was studied in time, in several hydrogels, and extruded from different needle diameters. Our findings indicate that cells survive the extrusion and that their subsequent viability was not different from that of unprinted cells. The applied extrusion conditions did not affect cell survival, and BMSCs could subsequently differentiate along the osteoblast lineage. Furthermore, we were able to combine two distinct cell populations within a single scaffold by exchanging the printing syringe during deposition, indicating that this 3D fiber deposition system is suited for the development of bone grafts containing multiple cell types.

Patient-reported outcome in total hip replacement: A COMPARISON OF FIVE INSTRUMENTS OF HEALTH STATUS

Our aim was to define the minimum set of patient-reported outcome measures which are required to assess health status after total hip replacement (THR). In 114 patients, we compared the pre-operative characteristics and sensitivity to change of the Oxford hip score (OHS), the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), the SF-36, the SF-12 (derived from the SF-36), and the Euroqol questionnaire (EQ-5D). At one year after operation, very large effect sizes were found for the disease-specific measures, the physical domains of the SF-12, SF-36 and the EQ-5Dindex (1.3 to 3.0). Patients in Charnley class A showed more change in the OHS, WOMAC pain and function, the physical domains of the SF-36 and the EQ-5Dvas (p < 0.05) compared with those in the Charnley B and C group. In this group, the effect size for the OHS more than doubled the effect sizes of WOMAC pain and physical function. We found high correlations and correlations of change between the OHS, the WOMAC, the physical domains of the SF-12 and the SF-36 and EQ-5Dindex. The SF-36 and EQ-5D scores at one year after operation approached those of the general population. Furthermore, we found a binomial distribution of the pre-operative EQ-5Dindex score and a pre-operative discrepancy and post-operative agreement between the EQ-5Dvas and EQ-5Dindex. We recommend the use of the OHS and SF-12 in the assessment of THR. The SF-36 may be used in circumstances when smaller changes in health status are investigated, for example in the follow-up of THR. The EQ-5D is useful in situations in which utility values are needed in order to calculate cost-effectiveness or quality-adjusted life years (QALYs), such as in the assessment of new techniques in THR.

Viable osteogenic cells are obligatory for tissue-engineered ectopic bone formation in goats

In this study we investigated the bone-forming capacity of tissue-engineered (TE) constructs implanted ectopically in goats. As cell survival is questionable in large animal models, we investigated the significance of vitality, and thus whether living cells instead of only the potentially osteoinductive extracellular matrix are required to achieve bone formation. Vital TE constructs of porous hydroxyapatite (HA) covered with differentiated bone marrow stromal cells (BMSCs) within an extracellular matrix (ECM) were compared with identical constructs that were devitalized before implantation. The devitalized implants did contain the potentially osteoinductive ECM. Furthermore, we evaluated HA impregnated with fresh bone marrow and HA only. Two different types of HA granules with a volume of approximately 40 microm were investigated: HA70/800, a microporous HA with 70% interconnected macroporosity and an average pore size of 800 microm, and HA60/400, a smooth HA with 60% interconnected macropores and an average size of 400 microm. Two granules of each type were combined and then treated as a single unit for cell seeding, implantation, and histology. The tissue-engineered samples were obtained by seeding culture-expanded goat BMSCs on the HA and subsequently culturing these constructs for 6 days to allow cell differentiation and ECM formation. To devitalize, TE constructs were frozen in liquid nitrogen according to a validated protocol. Fresh bone marrow impregnation was performed perioperatively (4 mL per implant unit). All study groups were implanted in bilateral paraspinal muscles. Fluorochromes were administered at three time points to monitor bone mineralization. After 12 weeks the units were explanted and analyzed by histology of nondecalcified sections. Bone formation was present in all vital tissue-engineered implants. None of the other groups showed any bone formation. Histomorphometry indicated that microporous HA70/800 yielded more bone than did HA60/400. Within the newly formed bone, the fluorescent labels showed that mineralization had occurred before 5 weeks of implantation and was directed from the HA surface toward the center of the pores. In conclusion, tissue-engineered bone formation in goats can be achieved only with viable constructs of an appropriate scaffold and sufficient BMSCs.

Balloon vertebroplasty in combination with pedicle screw instrumentation: a novel technique to treat thoracic and lumbar burst fractures.

Study Design. Clinical trial (phase II). Objectives. To assess the feasibility and safety of balloon vertebroplasty after posterior short-segment reduction and fixation for the treatment of traumatic burst fractures. Summary of Background Data. Hardware failure and loss of reduction after posterior short-segment instrumentation are complications caused by insufficiency of anterior column support. This is due to migration of disc tissue through the endplate into the fractured vertebral body that cannot be restored with posterior instrumentation. Methods. Patients with traumatic thoracolumbar burst fractures without neurologic deficits were included. After posterior reduction and fixation, bilateral transpedicular balloon reduction of the endplate was performed, and calcium phosphate cement was injected. Preoperative and postoperative Cobb angle and central and anterior height were assessed with radiographs and MRI. Results. Twenty patients underwent surgery without technical difficulties, and a substantial reduction of the endplates could be achieved with the technique. All patients recovered uneventfully, and the neurologic examination revealed no deficits. The postoperative radiographs and magnetic resonance images demonstrated a good fracture reduction and filling of the bone defect without unwarranted bone displacement. The central and anterior height of the vertebral body could be restored to 78 and 91% of the estimated intact height, respectively. Complications were cement leakage in five cases without clinical implications and one wound hematoma. Conclusions. Transpedicular balloon vertebroplasty for the direct restoration of burst fractures seems feasible in combination with posterior instrumentation. Cement leakage occurred but had no clinical consequences.

MRI findings of thoracolumbar spine fractures: a categorisation based on MRI examinations of 100 fractures.

Abstract  Objective. To define the state of different structures of the fractured thoracolumbar spine which may play a role in the immediate and long-term mechanical stability on MR images and to investigate the relationship of these findings with the AO classification of spinal injuries. Design. The state of the anterior longitudinal ligament, posterior longitudinal ligament, posterior ligamentous complex, cranial and caudal endplates, cranial and caudal discs and the vertebral body were defined using clinical, experimental and radiological data. The state of these structures was reported for each fracture on the MRI examinations and the different MRI features appropriate for different fracture classes were defined. Patients. MRI examinations of 70 patients with 100 fractures of the thoracolumbar spine were used for this study. Results. Wide variations were seen in the state of the structures studied. We could not find a definite pattern to relate these findings with the AO classification scheme. Conclusions. MR findings should be integrated into future classification schemes of thoracolumbar spine fractures. This would enable specific data about the structures involved in the stability of the spine to be acquired. Prospective studies using the criteria developed in this study may help resolve some of the controversies concerning the diagnosis and prognosis of these injuries as well as the development of new classification systems.

Can Ilizarov joint distraction delay the need for an arthrodesis of the ankle? A preliminary report

We applied joint distraction using an Ilizarov apparatus in 11 patients with post-traumatic osteoarthritis of the ankle to try to delay the need for an arthrodesis. Distraction for three months resulted in clinical improvement in pain and mobility for a mean of two years, with an increase in the joint space. We considered that these effects may be produced by the absence of mechanical stress on the cartilage combined with the intra-articular hydrostatic pressures during distraction. We measured these pressures during walking with distraction, and found levels very similar to those reported to improve osteoarthritic cartilage when applied in vitro.

Integration of press-fit implants in cortical bone : A study on interface kinetics

The early healing phase of hard tissue implants is important to their long-term success. Problems during this phase can result in a so-called primary biological failure. In 24 New Zealand white rabbits, the healing in cortical bone of noncoated TiAlV and cpTi cylinders and of TiAlV cylinders plasma-spray-coated with hydroxyapatite (HA) of fluorapatite (FA) was investigated histologically and histomorphometrically after 3, 7, 14, and 28 days. Histomorphometry consisted of bone contact measurements and the use of a new semi quantitative scoring system that discriminated various tissues in contact with the implant. The results demonstrated that the most important parameter in initial implant healing is the bone itself and not the characteristics of the implanted material. For all implants, healing was characterized by a sequence of hematoma formation, bone resorption, and new bone formation where the initial press-fit situation revealed more bone-implant contact than after 7 and 14 days. There were only minor differences between the implant types: the new bone formation directly on the implant surface was qualitatively histologically superior to the CaP-coated implants, but this could be confirmed with the scoring method only for the HA-coated implants. It is concluded that initial press-fit fixation in cortical bones is not an end situation; rather, what happens is that as a result of interface remodeling, early postoperatively implant integration in the bone will decrease temporarily prior to a subsequent phase of new bone formation.

Growth factor interactions in bone regeneration

Bone regeneration is a complex process regulated by a large number of bioactive molecules. Many growth factors and cytokines involved in the natural process of bone healing have been identified and tested as potential therapeutic candidates to enhance the regeneration process. Although many of these studies show an enhancement of the bone regeneration process by a single drug therapy, in vivo bone regeneration is the result of a complex interplay between the applied growth factor and various endogenous produced growth factors. To investigate these growth factor interactions, various studies have investigated the effect of growth factor combinations on bone regeneration. This review provides an overview of the growth factor and cytokine combinations tested in translational bone regeneration studies and shows that their interaction may result in an enhancement or inhibition of bone formation.

Critical size defect in the goat's os ilium. A model to evaluate bone grafts and substitutes.

Bone defects and their treatment are a well known problem in orthopaedic surgery. A critical size defect is a suitable model to study bone replacement materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate allograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect. The goat allows for implantation of large implants and has a metabolic rate more comparable with that of humans than small animals. The critical size defect, located in the goats iliac wing, is easily reproducible and allows qualitative and quantitative evaluation of bone grafts and bone graft substitutes. After 3 months of healing, the unfilled defects showed 13.5% bone in the defect, the autografted defects 36.3%, and the allografted 18.5%. The copolymer gave only 1.5% bone in the defect; this is in contrast to previous reports. The described model allows for the evaluation of bone graft substitutes before introduction into clinical practice.

The epidemiology of total hip replacement in the Netherlands and Sweden - Present status and future needs

By combining data from the Discharge registers and the census bureaus in The Netherlands and Sweden, we calculated the age-specific incidences of primary total hip replacement (THR), studied the demographic profile of the population receiving THR and predicted demands. In the period 1986-1997, the number of THRs increased by 20% in Sweden to 10,000 operations (113/100,000 inhabitants) and by 68% to 17,400 operations (112/100,000 inhabitants) in The Netherlands. Of this increase 3% and 15% could be explained by changes in the age-profile and size of the population, respectively. Although the overall incidence of THR was similar in both countries in 1997, we found that, after correction for differences in population structure, the incidence of THR was 20% higher in The Netherlands. In Sweden, relatively more men were operated on than in The Netherlands. We also found that in Sweden, but not in the Netherlands, relatively more older people were operated on in 1997 than in 1987. Assuming no further change in the age- and sex-specific arthroplasty rates, the predicted annual number of total hip replacements by the year 2020 will increase by at least one fourth in Sweden and almost one half in The Netherlands.