Factors stimulating bone formation

Risk factors affecting spinal fusion: A meta-analysis of 39 cohort studies

PURPOSE

We performed a meta-analysis to identify risk factors affecting spinal fusion.

METHODS

We systematically searched PubMed, Embase, and the Cochrane Library from inception to January 6, 2023, for articles that report risk factors affecting spinal fusion. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using fixed-effects models for each factor for which the interstudy heterogeneity I2 was < 50%, while random-effects models were used when the interstudy heterogeneity I2 was ≥ 50%. Using sample size, Egger's P value, and heterogeneity across studies as criteria, we categorized the quality of evidence from observational studies as high-quality (Class I), moderate-quality (Class II or III), or low-quality (Class IV). Furthermore, the trim-and-fill procedure and leave-one-out protocol were conducted to investigate potential sources of heterogeneity and verify result stability.

RESULTS

Of the 1,257 citations screened, 39 unique cohort studies comprising 7,145 patients were included in the data synthesis. High-quality (Class I) evidence showed that patients with a smoking habit (OR, 1.57; 95% CI, 1.11 to 2.21) and without the use of bone morphogenetic protein-2 (BMP-2) (OR, 4.42; 95% CI, 3.33 to 5.86) were at higher risk for fusion failure. Moderate-quality (Class II or III) evidence showed that fusion failure was significantly associated with vitamin D deficiency (OR, 2.46; 95% CI, 1.24 to 4.90), diabetes (OR, 3.42; 95% CI, 1.59 to 7.36), allograft (OR, 1.82; 95% CI, 1.11 to 2.96), conventional pedicle screw (CPS) fixation (OR, 4.77; 95% CI, 2.23 to 10.20) and posterolateral fusion (OR, 3.63; 95% CI, 1.25 to 10.49).

CONCLUSIONS

Conspicuous risk factors affecting spinal fusion include three patient-related risk factors (smoking, vitamin D deficiency, and diabetes) and four surgery-related risk factors (without the use of BMP-2, allograft, CPS fixation, and posterolateral fusion). These findings may help clinicians strengthen awareness for early intervention in patients at high risk of developing fusion failure.

Phosphorylated heat shock protein 27 improves the bone formation ability of osteoblasts and bone marrow stem cells from patients with adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is a scoliotic deformity of unknown etiology that occurs during adolescent development. Abnormal bone metabolism is closely related to AIS, but the cause is uncertain. Recent studies have shown that heat shock protein 27 (HSP27) and its phosphorylation (pHSP27) play important roles in bone metabolism. However, whether HSP27 and pHSP27 are involved in abnormal bone metabolism in AIS is unclear.

Methods

Osteoblasts (OBs) and bone marrow stem cells (BMSCs) were extracted from the facet joints and bone marrow of AIS patients and controls who underwent posterior spinal fusion surgery. The expression levels of HSP27 and pHSP27, as well as the expression levels of bone formation markers in OBs from AIS patients and controls, were examined by quantitative real-time PCR (qRT-PCR) and Western blotting. The mineralization ability of OBs from AIS patients and controls was analyzed by alizarin red staining after osteogenic differentiation. Heat shock and thiolutin were used to increase the levels of pHSP27 in OBs, and the levels of bone formation markers were also investigated. In addition, the levels of pHSP27 and the bone formation ability of BMSCs from AIS patients and controls were investigated after heat shock treatment.

Results

Lower pHSP27 levels and impaired osteogenic differentiation abilities were observed in the OBs of AIS patients than in those of controls. Thiolutin increased HSP27 phosphorylation and increased the mRNA levels of SPP1 and ALPL in OBs from AIS patients. Heat shock treatment increased SPP1 and HSP27 mRNA expression, pHSP27 levels, OCN expression, and mineralization ability of both OBs and BMSCs from AIS patients.

Conclusion

Heat shock treatment and thiolutin can increase the levels of pHSP27 and further promote the bone formation of OBs and BMSCs from AIS patients. Therefore, decreased pHSP27 levels may be associated with abnormal bone metabolism in AIS patients.

Comparative Study of Radiological and Clinical Outcomes in Patients Undergoing Minimally Invasive Lateral Lumbar Interbody Fusion Using Demineralized Bone Matrix Alone or with Low-Dose Escherichia coli-Derived rhBMP-2

OBJECTIVE

To compare the results of interbody fusion in patients undergoing minimally invasive lateral lumbar interbody fusion (LLIF) using demineralized bone matrix (DBM) alone versus DBM+recombinant human bone morphogenetic protein-2 (rhBMP2).

METHODS

This retrospective case-controlled study was conducted in patients undergoing minimally invasive LLIF (n = 54) for lumbar interbody fusion; they were divided into 2 groups: DBM-only group and DMB+rhBMP2 group. The improvements of segmental and lumbar lordosis and restoration of disc height were measured, and the interbody fusion rates were determined using a modified Bridwell grading system. Clinical outcomes after surgery, such as visual analog scale scores of back pain and leg pain, and Oswestry disability index were compared.

RESULTS

There were no significant differences in disc height, lumbar and segmental lordosis, or interbody fusion rate between the 2 groups. However, the proportion of Bridwell grade 1 as complete interbody bridging was higher in the DBM+rhBMP2 group than in the DBM-only group at both 6 and 12 months (P < 0.001). Clinical parameters showed equally significant improvement during follow-up in both groups, with no significant differences between the groups.

CONCLUSION

In minimally invasive LLIF, adding Escherichia coli-derived rhBMP2 to DBM did not affect clinical outcomes or radiation parameters, but increased the speed of fusion and interbody bony bridging rate.

Incorporation of an Allogenic Cortical Bone Graft Following Arthrodesis of the First Metatarsophalangeal Joint in a Patient with Hallux Rigidus

Hallux rigidus is degenerative arthritis of the first metatarsophalangeal joint characterized by pain and stiffness in the joint with limitation of motion and functional impairment. Recently, bone grafts have been introduced in orthopedic procedures, namely osteosynthesis and arthrodesis. Allografts can induce bone formation, provide support for vascular and bone ingrowth and have a low risk of immunological rejection. A 52-year-old female patient with hallux rigidus underwent arthrodesis of the first metatarsophalangeal joint using Shark Screw^® made of allogenic cortical bone. Corrective surgery was performed after 10 weeks, and a 5 × 3 mm large part of the Shark Screw^® with the surrounding patient's bone was removed. A histological evaluation revealed a vascularized graft with the newly formed compact lamellar bone fitting exactly to the cortical graft. The bone surface was lined by plump osteoblasts with osteoid production, and osteocytes were present in the lacunae. The arthrodesis of the first metatarsophalangeal joint using an allogenic cortical bone graft results in fast, primary bone healing without immunological rejection. This case suggests that the cortical allograft is a good and safe treatment option with an excellent graft incorporation into the host bone. However, as the literature evaluating the histology of different bone grafts is scarce, further high-level evidence studies with adequate sample sizes are needed to confirm our findings.

Nanohydroxyapatite/polyamide 66 crosslinked with QK and BMP-2-derived peptide prevented femur nonunion in rats

A dual-peptide controlled released system based on nHA/PA66 scaffold for enhancing bone regeneration.

Static Versus Expandable Devices Provide Similar Clinical Outcomes Following Minimally Invasive Transforaminal Lumbar Interbody Fusion

BACKGROUND

Few studies have analyzed differences in radiographic parameters and patient-reported outcomes (PROs) between expandable and static interbody devices in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).

QUESTIONS/PURPOSES

To evaluate differences in radiographic parameters and PROs following MIS TLIF between static and expandable interbody devices.

METHODS

Patients undergoing primary, single-level MIS TLIF between 2014 and 2017 were retrospectively identified. Radiographic measurements including lumbar lordosis (LL), segmental lordosis (SL), disc height (DH), and foraminal height (FH) were performed on lateral radiographs before and after MIS TLIF with a static or expandable articulating interbody device. Radiographic outcomes and PROs were compared using paired and unpaired Student's t test.

RESULTS

Thirty patients received expandable interbody devices and 30 patients received static interbody devices. The expandable device cohort exhibited significantly greater improvement in DH and FH at final follow-up compared with those receiving a static device. Both device cohorts experienced significant improvements in PROs at 6 months post-operatively.

CONCLUSION

MIS TLIF with an expandable interbody device led to a greater increase of DH and FH than with a static interbody device. Patients undergoing MIS TLIF can expect similar improvements in PROs whether receiving a static or an expandable interbody device. Further studies are required to better understand improvements in clinical outcomes afforded by expandable interbody devices.

An effective dual-factor modified 3D-printed PCL scaffold for bone defect repair

Numerous bioactive molecules produced in cells are involved in the process of bone formation. We consider that appropriate, simultaneous application of two types of bioactive molecules would accelerate the regeneration of tissues and organs. Therefore, we combined aspirin-loaded liposomes (Asp@Lipo) and bone forming peptide-1 (BFP-1) on three dimensional-printed polycaprolactone (PCL) scaffold and determined whether this system improved bone regeneration outcomes. in vitro experiments indicated that Asp@Lipo/BFP-1at a 3:7 ratio was the best option for enhancing the osteogenic efficiency of human mesenchymal stem cells (hMSCs). This was confirmed in an in vivo cranial defect animal model. In addition, RNA-Seq was applied for preliminarily exploration of the mechanism of action of this composite scaffold system, and the results suggested that it mainly improved bone regeneration via the PI3K/AKT signaling pathway. This approach will have potential for application in bone tissue engineering and regenerative medicine.

Fusion Rates of Lateral Lumbar Interbody Fusion Using Recombinant Human Bone Morphogenetic Protein-2

STUDY DESIGN

Retrospective observational case series.

OBJECTIVES

Lateral lumbar interbody fusion (LLIF) has been widely performed with recombinant human bone morphogenetic protein-2 (rhBMP-2), but the fusion rates using this graft alternative have not been well studied. We aimed to evaluate fusion rates in 1- and 2-level LLIF with rhBMP-2 and their relationship with fixation, as well as rates of BMP-related complications.

METHODS

Institutional review board (IRB)-approved spine registry cohort of 93 patients who underwent LLIF with rhBMP-2 (71 one-level cases and 22 two-level cases). Minimum 1-year clinical follow-up and computed tomography (CT) scan for fusion assessment. Postoperative CT scans were used to evaluate the rate of fusion in all patients. Instrumentation and complications were collected from chart and imaging review.

RESULTS

Average age was 65 years (67% female). For 1-level cases, 92% (65/71) had complete fusion and 8% (6/71) had either incomplete or indeterminate fusion. Three of the 6 patients who had incomplete or indeterminate fusion had bilateral pedicle screw instrumentation, 1 patient had unilateral posterior fixation, and 2 had no fixation. In 2-level cases, 86% (19/22) had complete fusion and 14% (3/22) had either incomplete or indeterminate fusion. The 3 patients who had incomplete or indeterminate fusion did not have fixation.

CONCLUSION

Interbody fusion rates with rhBMP-2 via LLIF was 92% in 1-level cases and 86% in 2-level cases, indicating that rhBMP-2 may be used as a viable graft alternative to allograft options for LLIF. Higher rates of pseudarthrosis occurred when not using fixation.

Stacked PZT Discs Generate Necessary Power for Bone Healing through Electrical Stimulation in a Composite Spinal Fusion Implant

Electrical stimulation devices can be used as adjunct therapy to lumbar spinal fusion to promote bone healing, but their adoption has been hindered by the large battery packs necessary to provide power. Piezoelectric composite materials within a spinal interbody cage to produce power in response to physiological lumbar loads have recently been investigated. A piezoelectric macro-fiber composite spinal interbody generated sufficient power to stimulate bone growth in a pilot ovine study, despite fabrication challenges. The objective of the present study was to electromechanically evaluate three new piezoelectric disc composites, 15-disc insert, seven-disc insert, and seven-disc Compliant Layer Adaptive Composite Stack (CLACS) insert, within a spinal interbody, and validate their use for electrical stimulation and promoting bone growth. All implants were electromechanically assessed under cyclic loads of 1000 N at 2 Hz, representing physiological lumbar loading. All three configurations produced at least as much power as the piezoelectric macro-fiber composites, validating the use of piezoelectric discs for this application. Future work is needed to characterize the electromechanical performance of commercially manufactured piezoelectric stacks under physiological lumbar loads, and mechanically assess the composite implants according to FDA guidelines for lumbar interbody fusion devices.

In vivo evaluation of a novel nanocomposite porous 3D scaffold in a rabbit model: histological analysis

The healing of load-bearing segmental defects in long bones is a challenge due to the complex nature of the weight that affects the bone part and due to bending, shearing, axial, and torsional forces. An innovative porous 3D scaffolds implant of CaCO₃ aragonite nanocomposite derived from cockle shell was advanced for substitute bone solely for load-bearing cases. The biomechanical characteristics of such materials were designed to withstand cortical bone strength. In promoting bone growth to the implant material, an ideal surface permeability was formed by means of freeze drying and by adding copolymers to the materials. The properties of coating and copolymers supplement were also assessed for bone-implant connection resolutions. To examine the properties of the material in advanced biological system, an experimental trial in an animal model was carried out. Critical sized defect of bone was created in rabbit's radial bone to assess the material for a load-bearing application with a short and extended period assessment with histological evaluation of the incorporated implanted material to the bone of the host. Trials in animal models proved that the material has the capability of enduring load-bearing conditions for long-term use devoid of breaking or generating stress that affects the host bone. Histological examination further confirmed the improved integration of the implanted materials to the host bone with profound bone development into and also above the implanted scaffold, which was attained with negligible reaction of the tissues to a foreign implanted material.

Local delivery of strontium ranelate promotes regeneration of critical size bone defects filled with collagen sponge

The effect of local delivery of strontium ranelate (SR) on bone regeneration of critical size bone defects filled with collagen sponge was evaluated. Bone defects of 5 mm diameter created in rat calvaria were filled with collagen sponge (C); collagen sponge with 5 mM Sr²⁺ SR (C5SR) or collagen sponge with 50 mM Sr²⁺ SR (C50SR). After 2, 4, and 6 weeks, bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were evaluated by computed microtomography. At 6 weeks, histological analysis was performed. Intragroup comparisons were made by the Friedman test, while comparisons between groups were made by Kruskal-Wallis test (α = 5%). All groups showed increased BV, BS, Tb.Th, and Tb.N over time, but only C50SR promoted the reduction of Tb.Sp (p < 0.05). No significant differences between groups were detected at weeks 2 and 4. However, C50SR showed the highest values of BV, BS, and Tb.Th at 6 weeks (p < 0.05). Histological analysis revealed connective tissue in C and C5SR and immature bone tissue in C50SR. Local delivery of SR 50 mM Sr²⁺ associated with collagen sponge increased and accelerated bone regeneration in critical bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 333-341, 2018.

EFFECT OF PULSED ELECTROMAGNETIC FIELD ON THE CONSOLIDATION OF POSTEROLATERAL ARTHRODESES IN THE LUMBOSACRAL SPINE: A PROSPECTIVE, DOUBLE-BLIND, RANDOMIZED STUDY

ABSTRACT Objective: To assess the effect of pulsed electromagnetic field (PEMF) on the consolidation of instrumented lumbar posterolateral arthrodeses in patients who have been surgically treated for degenerative spine disease. Methods: Forty cases were recruited from 163 consecutive patients undergoing lumbar arthrodesis at the same center. The patients were randomized into two groups of 20 patients: Active Group, who were exposed to PEMF for 4 hours a day for 90 days after surgery, and Inactive Group, who received an identical device, with the same instructions for use but without the ability to generate PEMF. The patients underwent computed tomography scans at 45, 90, 180 and 360 days after surgery to check for the occurrence of arthrodesis at each operated spinal level. Results: In the course of the study, two patients were excluded from each group. There were no significant differences between the groups with respect to age, gender, smoking habit, or the number of vertebral levels included in the arthrodesis. The percentage of consolidation of the vertebral levels increased at 90, 180 and 360 days compared to 45 days (p<0.001) in both groups. The Active Group had a 276% greater chance of consolidation in the vertebral levels (OR = 3.76; 95% CI: 1.39-10.20), regardless of the time of evaluation. Patients in the Active Group presented 16% more consolidation than patients in the inactive group (p=0.018). Conclusions: Post-operative exposure to PEMF following instrumented arthrodesis of the lumbar spine for degenerative spine disease increased consolidation in the first year after surgery.

Demineralized Bone Matrix (DBM) as a Bone Void Filler in Lumbar Interbody Fusion: A Prospective Pilot Study of Simultaneous DBM and Autologous Bone Grafts

Objective

Solid bone fusion is an essential process in spinal stabilization surgery. Recently, as several minimally invasive spinal surgeries have developed, a need of artificial bone substitutes such as demineralized bone matrix (DBM), has arisen. We investigated the in vivo bone growth rate of DBM as a bone void filler compared to a local autologous bone grafts.

Methods

From April 2014 to August 2015, 20 patients with a one or two-level spinal stenosis were included. A posterior lumbar interbody fusion using two cages and pedicle screw fixation was performed for every patient, and each cage was packed with autologous local bone and DBM. Clinical outcomes were assessed using the Numeric Rating Scale (NRS) of leg pain and back pain and the Korean Oswestry Disability Index (K-ODI). Clinical outcome parameters and range of motion (ROM) of the operated level were collected preoperatively and at 3 months, 6 months, and 1 year postoperatively. Computed tomography was performed 1 year after fusion surgery and bone growth of the autologous bone grafts and DBM were analyzed by ImageJ software.

Results

Eighteen patients completed 1 year of follow-up, including 10 men and 8 women, and the mean age was 56.4 (32–71). The operated level ranged from L3/4 to L5/S1. Eleven patients had single level and 7 patients had two-level repairs. The mean back pain NRS improved from 4.61 to 2.78 (p=0.003) and the leg pain NRS improved from 6.89 to 2.39 (p<0.001). The mean K-ODI score also improved from 27.33 to 13.83 (p<0.001). The ROM decreased below 2.0 degrees at the 3-month assessment, and remained less than 2 degrees through the 1 year postoperative assessment. Every local autologous bone graft and DBM packed cage showed bone bridge formation. On the quantitative analysis of bone growth, the autologous bone grafts showed significantly higher bone growth compared to DBM on both coronal and sagittal images (p<0.001 and p=0.028, respectively). Osteoporotic patients showed less bone growth on sagittal images.

Conclusion

Though DBM alone can induce favorable bone bridging in lumbar interbody fusion, it is still inferior to autologous bone grafts. Therefore, DBM is recommended as a bone graft extender rather than bone void filler, particularly in patients with osteoporosis.

Bone repair: Effects of physical exercise and LPS systemic exposition

Bone repair can be facilitated by grafting, biochemical and physical stimulation. Conversely, it may be delayed lipopolysaccharide (LPS). Physical exercise exerts beneficial effects on the bone, but its effect on bone repair is not known. We investigated the effect of exercise on the LPS action on bone healing through bone densitometry, quantitative histological analysis for bone formation rate and immunohistochemical markers in sedentary and exercised animals. Rats ran on the treadmill for four weeks. After training the rats were submitted to a surgical procedure (bone defect in the right tibia) and 24h after the surgery LPS was administered at a dose of 100μg/kg i.p., whereas the control rats received a saline injection (1ml/kg, i.p.). Right tibias were obtained for analysis after 10days during which rats were not submitted to physical training. Physical exercise had a positive effect on bone repair, increasing bone mineral density, bone mineral content, bone formation rate, type I collagen and osteocalcin expression. These parameters were not affected by systemic administration of LPS. Our data indicate that physical exercise has an important osteogenic effect, which is maintained during acute systemic inflammation induced by exposure to a single dose of LPS.

Difference in canal encroachment by the fusion mass between anterior cervical discectomy and fusion with bone autograft and anterior plating, and stand-alone cage

We conducted a prospective randomized study comparing stand-alone cage and bone autograft and plate implants in anterior cervical discectomy and fusion (www.clinicaltrials.gov, NCT01011569). Our interim analysis showed autologous bone graft with plating was superior to a stand-alone cage for segmental lordosis. During this analysis, we noted a difference in canal encroachment by the fusion mass between the two fusion groups. A narrow cervical spinal canal is an important factor in the development of cervical spondylotic myelopathy, therefore this unexpected potential risk of spinal cord compression necessitated another interim analysis to investigate whether there was a difference in canal encroachment by the fusion mass between the two groups. Patients had a minimum 1year of follow-up. The Neck Disability Index, neck and arm pain Visual Analog Scales and lateral radiographs, including bone fusion patterns, were evaluated. Twenty-seven (16 males, 11 females, mean age 54.8years) and 31 (24 males, seven females, mean age 54.5years) patients were in the cage and plate group, respectively. Both groups improved after surgery. Fusion began at 2.6months and 1.3months and finished at 6.7months and 4.0months in 24 (88.9%) and 28 (90.3%) patients in the cage and plate group, respectively. Encroachment into the spinal canal by the fusion mass was significantly different between the fusion types, occuring in 21 (77.8%) patients in the cage group versus six (19.4%) in the plate group (p=0.003). There was a high incidence of spinal canal encroachment by the fusion mass in the stand-alone cage group, possibly limiting use in narrow spinal canals.

Dual-controlled release system of drugs for bone regeneration

Controlled release systems have been noted to allow drugs to enhance their ability for bone regeneration. To this end, various biomaterials have been used as the release carriers of drugs, such as low-molecular-weight drugs, growth factors, and others. The drugs are released from the release carriers in a controlled fashion to maintain their actions for a long time period. Most research has been focused on the controlled release of single drugs to demonstrate the therapeutic feasibility. Controlled release of two combined drugs, so-called dual release systems, are promising and important for tissue regeneration. This is because the tissue regeneration process of bone formation is generally achieved by multiple bioactive molecules, which are produced from cells by other molecules. If two types of bioactive molecules, (i.e., drugs), are supplied in an appropriate fashion, the regeneration process of living bodies will be efficiently promoted. This review focuses on the bone regeneration induced by dual-controlled release of drugs. In this paper, various dual-controlled release systems of drugs aiming at bone regeneration are overviewed explaining the type of drugs and their release materials.

Contribuição da aplicação do ultrassom de baixa potência na prevenção de osteopenia em tíbias de ratos sob ausência de carga

Este trabalho objetivou verificar se o ultrassom de baixa potência (US) previne a ocorrência de osteopenia em tíbias de ratos sob ausência de carga. Foram utilizados 45 Rattus novergicus albinus, Wistar adultos, machos, distribuídos em cinco grupos iguais: C - animais-controle livres em gaiolas por 21 dias; S - animais suspensos pela cauda por 21 dias; ST - suspensos pela cauda por 21 dias e concomitantemente tratados com US; S→C - suspensos por 21 dias e depois permanecendo livres em gaiolas por mais 21 dias; S→CT - suspensos por 21 dias e depois permanecendo livres em gaiolas por mais 21 dias e concomitantemente tratados com US. O tratamento foi realizado com US de 1,5MHz, ciclo de trabalho 1:4, 30mW/cm², na tíbia direita, por 15 sessões de 20 minutos cada, cinco sessões por semana. Ainda vivos, os animais foram submetidos a exame de densitometria óssea para verificação da densidade mineral óssea (DMO) e do conteúdo mineral ósseo (CMO). Após a eutanásia dos animais, as tíbias foram desarticuladas, dissecadas e submetidas a ensaio mecânico destrutivo para análise da força máxima (Fmáx) e da rigidez (R). Foram avaliados também o comprimento (L) e o diâmetro (D) no ponto médio da tíbia. O grupo S apresentou valores de DMO, CMO, Fmáx, R, L e D menores em relação ao grupo C, demonstrando que a suspensão pela cauda é prejudicial a estas variáveis. O tratamento dos animais suspensos com o US, grupo ST, elevou os valores de CMO e DMO em relação aos do grupo S, igualando-os aos do grupo C. A Fmáx, R e L do grupo ST aumentou em relação ao grupo S e também em relação ao grupo C (p<0,05). Nenhuma diferença significativa foi encontrada entre as variáveis analisadas para os grupos S→CT e S→C (p>0,05). Os resultados obtidos neste estudo permitem concluir que o US de baixa potência contribuiu na prevenção e reversão da ocorrência da osteopenia nos animais submetidos à suspensão pela cauda, demonstrando que a ausência do estímulo mecânico causada pela impossibilidade da deambulação pode ser minimizada pela ação mecânica deste.

Compression and contact area of anterior strut grafts in spinal instrumentation: a biomechanical study

Background

Anterior bone grafts are used as struts to reconstruct the anterior column of the spine in kyphosis or following injury. An incomplete fusion can lead to later correction losses and compromise further healing. Despite the different stabilizing techniques that have evolved, from posterior or anterior fixating implants to combined anterior/posterior instrumentation, graft pseudarthrosis rates remain an important concern. Furthermore, the need for additional anterior implant fixation is still controversial. In this bench-top study, we focused on the graft-bone interface under various conditions, using two simulated spinal injury models and common surgical fixation techniques to investigate the effect of implant-mediated compression and contact on the anterior graft.

Methods

Calf spines were stabilised with posterior internal fixators. The wooden blocks as substitutes for strut grafts were impacted using a “pressfit” technique and pressure-sensitive films placed at the interface between the vertebral bone and the graft to record the compression force and the contact area with various stabilization techniques. Compression was achieved either with posterior internal fixator alone or with an additional anterior implant. The importance of concomitant ligament damage was also considered using two simulated injury models: pure compression Magerl/AO fracture type A or rotation/translation fracture type C models.

Results

In type A injury models, 1 mm-oversized grafts for impaction grafting provided good compression and fair contact areas that were both markedly increased by the use of additional compressing anterior rods or by shortening the posterior fixator construct. Anterior instrumentation by itself had similar effects. For type C injuries, dramatic differences were observed between the techniques, as there was a net decrease in compression and an inadequate contact on the graft occurred in this model. Under these circumstances, both compression and the contact area on graft could only be maintained at high levels with the use of additional anterior rods.

Conclusions

Under experimental conditions, we observed that ligamentous injury following type C fracture has a negative influence on the compression and contact area of anterior interbody bone grafts when only an internal fixator is used for stabilization. Because of the loss of tension banding effects in type C injuries, an additional anterior compressing implant can be beneficial to restore both compression to and contact on the strut graft.

Efeito do exercício físico e da administração de testosterona na consolidação de fraturas de tíbia em ratos

INTRODUÇÃO: Vários estudos têm sido realizados visando identificar um medicamento que acelere a consolidação de fraturas. OBJETIVO: Avaliar o efeito do exercício físico e da administração de testosterona no processo de consolidação de fratura de tíbia e fíbula de ratos. MATERIAIS E MÉTODOS: Rattus norvegicus (250 a 300 g) foram distribuídos aleatoriamente em quatro grupos de oito animais: Controle- fratura e imobilização; G1- fratura, imobilização e propionato de testosterona; G2- fratura, imobilização e treinamento físico de natação; G3- fratura, imobilização, treinamento físico de natação e propionato de testosterona. Os tratamentos foram iniciados imediatamente após a realização de fraturas fechadas no terço médio da tíbia direita. O programa de treinamento físico consistiu em 50 minutos de natação durante quatro semanas, cinco vezes por semana. O propionato de testosterona 3 mg/kg foi administrado por via subcutânea cinco vezes na semana durante quatro semanas. As variáveis analisadas incluíram evolução ponderal, tamanho do calo ósseo, níveis séricos de fósforo, cálcio, albumina, proteínas totais e atividade da fosfatase alcalina. RESULTADOS: O tamanho do calo ósseo foi maior no grupo submetido a tratamento combinando imobilização, exercício físico e testosterona. Os grupos tratados com testosterona combinada ou não a programa de natação apresentaram maiores níveis de fósforo e de fosfatase alcalina, além de menores níveis de proteínas totais e albumina. CONCLUSÃO: O grupo submetido ao programa de treinamento físico de natação combinado com a administração de testosterona obteve melhor consolidação óssea evidenciada pelo maior calo ósseo e atividade aumentada da fosfatase alcalina, sugerindo maior rapidez no processo de consolidação óssea.

Administration of growth factors for bone regeneration

Growth factors (GFs) such as BMPs, FGFs, VEGFs and IGFs have significant impacts on osteoblast behavior, and thus have been widely utilized for bone tissue regeneration. Recently, securing biological stability for a sustainable and controllable release to the target tissue has been a challenge to practical applications. This challenge has been addressed to some degree with the development of appropriate carrier materials and delivery systems. This review highlights the importance and roles of those GFs, as well as their proper administration for targeting bone regeneration. Additionally, the in vitro and in vivo performance of those GFs with or without the use of carrier systems in the repair and regeneration of bone tissue is systematically addressed. Moreover, some recent advances in the utility of the GFs, such as using fusion technology, are also reviewed.

Osteopenic bone cell response to strontium-substituted hydroxyapatite

Ionic substitution is a powerful tool to improve the biological performance of calcium phosphate based materials. In this work, we investigated the response of primary cultures of rat osteoblasts derived from osteopenic (O-OB) bone to strontium substituted hydroxyapatite (SrHA), and to hydroxyapatite (HA) as reference material, compared to normal (N-OB) bone cells. Strontium (Sr) and calcium (Ca) cumulative releases in physiological solution are in agreement with the greater solubility of SrHA than HA, whereas the differences between the two materials are levelled off in DMEM, which significantly reduced ion release. O-OB cells grown on SrHA exhibited higher proliferation and increased values of the differentiation parameters. In particular, Sr substitution increased the levels of proliferation, alkaline phosphatase, and collagen type I, and down-regulated the production of interleukin-6 of O-OB cells, demonstrating a promising future of SrHA in the treatment of bone lesions and defects in the presence of osteoporotic bone.

Comparison of the effects of electrical field stimulation and low-level laser therapy on bone loss in spinal cord-injured rats

OBJECTIVE

This study investigated the effects of low-level laser therapy (LLLT) and electrical stimulation (ES) on bone loss in spinal cord-injured rats.

MATERIALS AND METHODS

Thirty-seven male Wistar rats were divided into four groups: standard control group (CG); spinal cord-injured control (SC); spinal cord-injured treated with laser (SCL; GaAlAs, 830 nm, CW, 30 mW/cm, 250 J/cm(2)); and spinal cord-injured treated with electrical field stimulation (SCE; 1.5 MHz, 1:4 duty cycles, 30 mW, 20 min). Biomechanical, densitometric, and morphometric analyses were performed.

RESULTS

SC rats showed a significant decrease in bone mass, biomechanical properties, and morphometric parameters (versus CG). SCE rats showed significantly higher values of inner diameter and internal and external areas of tibia diaphyses; and the SCL group showed a trend toward the same result (versus SC). No increase was found in either mechanical or densitometric parameters.

CONCLUSION

We conclude that the mentioned treatments were able to initiate a positive bone-tissue response, maybe through stimulation of osteoblasts, which was able to determine the observed morphometric modifications. However, the evoked tissue response could not determine either biomechanical or densitometric modifications.

Pulsed electromagnetic fields stimulation affects BMD and local factor production of rats with disuse osteoporosis

Pulsed electromagnetic fields (PEMF) have been used widely to treat nonunion fractures and related problems in bone healing, as a biological and physical method. With the use of Helmholtz coils and PEMF stimulators to generate uniform time-varying electromagnetic fields, the effects of extremely low frequency electromagnetic fields on bone mineral density (BMD) and local factor production in disuse osteoporosis (DOP) rats were investigated. Eighty 4-month-old female Sprague Dawley (SD) rats were randomly divided into intact (INT) group, DOP group, calcitonin-treated (CT) group, and PEMF stimulation group. The right hindlimbs of all the rats were immobilized by tibia-tail fixation except for those rats in the INT group. Rats in the CT group were injected with calcitonin (2 IU/kg, i.p., once a day) and rats in the PEMF group were irradiated with PEMF immediately postoperative. The BMD, serum transforming growth factor-beta 1 (TGF-beta1), and interleukin-6 (IL-6) concentration of the proximal femur were measured 1, 2, 4, and 8 weeks after treatment. Compared with the CT and DOP groups, the BMD and serum TGF-beta1 concentration in the PEMF group increased significantly after 8 weeks. The IL-6 concentration in the DOP group was elevated significantly after operation. The PEMF group showed significantly lower IL-6 level than the DOP group. The results found demonstrate that PEMF stimulation can efficiently suppress bone mass loss. We, therefore, conclude that PEMF may affect bone remodeling process through promoting TGF-beta1 secretion and inhibiting IL-6 expression.

Physical approach for prevention and treatment of osteoporosis

Osteoporosis and its consequent fractures are a major problem in public health. To complement the conventional pharmacological treatment for this metabolic disease, non-pharmacological treatment options have been developed in the last decades. Several studies demonstrate that physical exercise programs including impact exercises, specific strength training, balance and coordination training may maintain or increase spine and hip bone mineral density as well as decrease the frequency of falls among osteoporotic and osteopenic patients. Furthermore, some physical agents such as vibratory platforms, low intensity electrical stimulation, laser therapy and ultrasound show positive effects on osteoporotic tissue as well. Consequently, while planning treatment for an osteoporotic patient, non-pharmacological management options should be considered and integrated to the conventional treatment in order to maximize its effects and improve the quality of life of these patients.

Impact of freezing on bone graft incorporation biomechanical evaluations in rats

BACKGROUND

With an increasing clinical application of grafting for bone reconstruction, it is important to understand the physiological and biological events of graft incorporation. In this study, we have investigated the impact of deep freezing on the biopotency for incorporation of bone grafts.

METHODS

Fresh and deep-frozen autogenous bone grafts were implanted in an 8-mm segmental defect in the tibia. The construct was stabilized with intramedullary nailing. Incorporation of the graft was assessed with use of conventional radiography, biomechanical testing and measurements of bone mineral content and density after 2 and 4 months, respectively.

FINDINGS

Frozen grafts were significantly less integrated after 2 months as compared to fresh grafts. After 4 months, however, the frozen grafts showed an overall reconstruction that was not significantly different from the fresh grafts. Both frozen and fresh grafted segments had only reached 70% strength of intact bone at 4 months.

INTERPRETATION

This study indicates that in the long run there are no significant consequences, radiologically or biomechanically, of deep freezing as compared to fresh bone grafts.

Treatment of osteoporosis by long-term magnetic field with extremely low frequency in rats

BACKGROUND

Osteoporosis is characterised by low bone mass and structural deterioration of bone tissue. In this study, the role of long-term extremely low frequency magnetic field (ELFMF) on osteoporosis was evaluated.

METHODS

The experiments were performed on 45 female Sprague-Dawley rats. The rats were divided into three groups (n = 15): Group I (ovariectomy (OVX) + ELFMF exposure), Group II (ovariectomised rats did not receive any treatment) and Group III (cage-control). Six months, 50 Hz, 1.5 mT magnetic field (MF) was used on Group I and Group II. Total body images of the animals were obtained with dual-energy X-ray absorptiometry.

RESULTS

Bone mineral content (BMC) and bone mineral density values were increased significantly in ELFMF group, decreased in the group of OVX and not changed in cage-control. At the end of the 6 months after exposure with ELFMF, alteration in studied biochemical markers were detected significant. Bone specific alkaline phosphatase (BAP) levels were increased in ELFMF and decreased in OVX groups when compared with cage-control group. N-telopeptide levels in OVX group were significantly higher than other groups. Testosterone and cortisol levels in OVX group were significantly higher and estradiol was lower than other groups.

CONCLUSIONS

Our study suggests that ELFMF may be useful in the prevention and treatment of osteoporosis.

Low-intensity electrical stimulation counteracts the effects of ovariectomy on bone tissue of rats: effects on bone microarchitecture, viability of osteocytes, and nitric oxide expression

Low Intensity Electrical Stimulation (LIES) has been used for bone repair, but little is known about its effects on bone after menopause. Osteocytes probably play a role in mediating this physical stimulus and they could act as transducers through the release of biochemical signals, such as nitric oxide (NO). The aim of the present study was to investigate the effects of LIES on bone structure and remodeling, NOS expression and osteocyte viability in ovariectomized (OVX) rats. Thirty rats (200-220 g) were divided into 3 groups: SHAM, OVX, and OVX subjected to LIES (OVX + LIES) for 12 weeks. Following the protocol, rats were sacrificed and tibias were collected for histomorphometric analysis and immunohistochemical detection of endothelial NO synthase (eNOS), inducible NOS (iNOS), and osteocyte apoptosis (caspase-3 and TUNEL). OVX rats showed significant (p < 0.05 vs. SHAM) decreased bone volume (10% vs. 25%) and trabecular number (1.7 vs. 3.9), and increased eroded surfaces (4.7% vs. 3.2%) and mineralization surfaces (15.9% vs. 7.7%). In contrast, after LIES, all these parameters were significantly different from OVX but not different from SHAM. eNOS and iNOS were similarly expressed in subperiosteal regions of tibiae cortices of SHAM, not expressed in OVX, and similarly expressed in OVX + LIES when compared to SHAM. In OVX, the percentage of apoptotic osteocytes (24%) was significantly increased when compared to SHAM (11%) and OVX + LIES (8%). Our results suggest that LIES counteracts some effects of OVX on bone tissue preserving bone structure and microarchitecture, iNOS and eNOS expression, and osteocyte viability.

Adhesion, proliferation, and osteogenic differentiation of a mouse mesenchymal stem cell line (BMC9) seeded on novel melt-based chitosan/polyester 3D porous scaffolds

The aim of the present work was to study the biological behavior of a mouse mesenchymal stem cell line when seeded and cultured under osteogenic conditions onto novel processed melt-based chitosan scaffolds. Scaffolds were produced by compression molding, followed by salt leaching. Scanning electron microscopy (SEM) observations and microCT analysis showed the pore sizes ranging between 250 and 500 microm and the interconnectivity of the porous structure. The chitosan-poly(butylenes succinate) scaffolds presented high mechanical properties, similar to the ones of trabecular bone (E1% approximately 75 MPa). Cytotoxicity assays were carried out using standard tests (accordingly to ISO/EN 10993 part 5 guidelines), namely, MTS test with a 24 h extraction period, revealing that L929 cells had similar metabolic activities to that obtained for the negative control. Cell culture studies were conducted using a mouse mesenchymal stem cell line (BMC9). Cells were seeded onto the scaffold and allowed to proliferate for 3 weeks under osteogenic conditions. SEM observations demonstrated that cells were able to proliferate and massively colonize the scaffolds structure. The cell viability assay MTS demonstrated that BMC9 cells were viable after 3 weeks of culture. The cells clearly evidenced a positive differentiation toward the osteogenic lineage, as confirmed by the high ALP activity levels. Moreover, energy dispersive spectroscopy (EDS) analysis revealed the presence of Ca and P in the elaborated extracellular matrix (ECM). These combined results indicate that the novel melt-based chitosan/polyester scaffolds support the adhesion, proliferation, and osteogenic differentiation of the mouse MSCs and shows adequate physicochemical and biological properties for being used as scaffolds in bone tissue engineering-related strategies.

Fresh cortical autograft versus fresh cortical allograft effects on experimental bone healing in rabbits: radiological, histopathological and biomechanical evaluation

Bone grafting is used to enhance healing in osteotomies, arthrodesis, and multifragmentary fractures and to replace bony loss resulting from neoplasia or cysts. They are source of osteoprogenitor cells and induce bone formation and provide mechanical support for vascular and bone ingrowth. Autografts are used commonly but quantity of harvested bone is limit. This study was designed to evaluate fresh cortical autograft and allograft effects on bone healing process. Twenty male White New Zealand rabbits were used in this study. In autograft group the defect was filled by fresh autogenous cortical graft, in allograft group the defect was filled by a segment of fresh allogenous cortical bone which was harvested at the time of surgery during the creation of radius bone defect. Then all surface soft tissue, such as muscle attachments, were removed from the harvested bone and changed between rabbits as a fresh allogenous cortical bone graft and was fixed by cercelage wire. Radiological, histopathological and biomechanical evaluations were performed blindly and results scored and analyzed statistically. Statistical tests did not support significant differences between two groups at the 14th and 56th postoperative day radiographically (P > 0.05). There was a significant difference radiologically for the 28th and the 42nd postoperative (P < 0.05). Autograft was superior to allograft at the 28th and 42nd postoperative day in radiological evaluation (P < 0.03). Histopathological and biomechanical evaluation revealed no significant differences between two groups.

Use of bone morphogenetic proteins for treatment of non-unions and future perspectives

Still a major problem in orthopedic and trauma surgery is the delayed healing or the non-union of long bone fractures. Demographic data reveal that due to the steadily rising age of the population, complications with the musculoskeletal system will increase during the next years. Bone morphogenetic proteins (BMPs) have successfully been applied in clinic for the treatment of delayed healing and non-unions. The broad difference concerning the indication, timing of treatment, dosage and application technique of BMPs calls for the need to perform further prospective studies in order to standardize the treatment and furthermore optimize the procedures or even develop new therapeutic strategies. For example, the application technique may be improved and in some cases injectable BMP preparations could be of use. Also the coating of implants with growth factors might be valuable in order to stimulate bone healing and to prevent delayed healing or non-union. This article tries to discuss some of the open questions, however can and will not reflect the absolute standard of care. To make the BMP treatment a standard of care, more clinical data and long time experiences are necessary. The intramedullary application of BMP in combination with autologous or allogenic bone grafts or bone substitutes after debridement and stabilization with implants seems to be an adequate procedure for treatment of atrophic non-unions. However, the total number of patients is too small to draw final conclusions. Further clinical studies need to be performed in the future.

Quantification of growth factors in allogenic bone grafts extracted with three different methods

BACKGROUND

Bony allografts are used for defect filling. A reliable sterilization method is the peracetic acid-ethanol sterilization procedure (PES). Several studies showed the antimicrobiological efficacy of this method. Aim of this study was the quantification of growth factors necessary for bone formation in PES sterilized allografts (n = 9).

METHODS

To extract the growth factors from the tissue three different methods were used: (a) use of collagenase 1 for extraction, (b) incubation of the material in a proteinase inhibitor cocktail (Complete), and (c) extraction with guanidine HCl. The supernatants from the different methods were analyzed for the total protein concentration and different growth factors.

RESULTS

The extraction with guanidine HCl resulted in the highest amount of protein measurable in the supernatants of the samples. For comparison of the individual growth factor values the results were normalized to the protein content. The highest growth factor amount/protein was detectable for BMP-2 using the GndHCL method followed by FGFa, IGF-I, TGF-beta1, VEGF, and PDGF. Comparing the three extraction methods, significant differences were measured for the individual growth factor content.

CONCLUSION

PES sterilized bony allografts contain several growth factors. Depending on the extraction method, the quantity of the analyzed growth factors varies.

Evidências da ação de agentes físicos sobre o metabolismo do tecido ósseo e seus potenciais usos clínicos

A ação de agentes físicos como o laser, o ultra-som pulsado e campos elétrico e eletromagnético (todos de baixa intensidade) no tecido ósseo tem sido muito estudada, revelando que estes são capazes de estimular a osteogênese, acelerar a consolidação de fraturas e aumentar a massa óssea. O uso destas modalidades terapêuticas foi primeiramente baseado na descoberta de que o tecido ósseo é um material piezoelétrico, isto é, que quando deformado torna-se capaz de gerar uma polarização e transformar energia mecânica em elétrica, o que ampliou as possibilidades terapêuticas sobre este tecido. O presente trabalho tem por objetivo apresentar as evidências dos efeitos fisiológicos e discorrer sobre os mecanismos de ação destes agentes físicos sobre o metabolismo ósseo, com base em artigos publicados na literatura científica internacional.

Autologous versus allogenic bone grafts in instrumented anterior cervical discectomy and fusion: a prospective study with respect to bone union pattern

BACKGROUND

The purpose of this prospective semi-randomised comparative study was to compare fusion rates, course of fusion, and occurrence of collapse and subsidence of autologous and allogenic bone grafts in instrumented anterior cervical fusion. The number of fused levels and the smoking status were investigated as potential factors influencing the bone-healing process. No similar prospective study on instrumented anterior cervical discectomy and fusion was found in the literature.

METHODS

Seventy-nine consecutive patients were operated on using the Smith-Robinson technique with a single instrumentation system at one or two levels. Seventy-six cadaverous fibular bone grafts and 37 autologous iliac-crest bone grafts were inserted. All patients were followed up for at least 2 years.

RESULTS

The radiographs obtained during the follow-up were analysed, and showed no statistical difference in fusion and collapse rate between autografts and allografts. Allografts showed significantly longer time to union. No case of graft migration was observed. No difference was found between fusion and collapse rate with respect to the number of fused levels in general, but greater time to union was seen in two-level fusions. When one- and two-level subgroups were compared, there was no evidence of any significant difference in fusion or collapse rates between autografts and allografts, and the healing process took longer in allogenic grafts. Smoking status did not alter any of the fusion or collapse rates, or the course of bone fusion.

CONCLUSIONS

This study demonstrates that allografts are suitable substitutes for autografts in instrumented ACDF. Prolonged time to union observed in allogenic bone grafts does not seem to be an important factor in instrumented procedures. Two-level grafting does not imply a significantly lower fusion rate, but longer time to union can be expected than with single-level instrumented procedures in both allograft and autograft subgroups. Our relatively small number of patients may not have been sufficient to decipher significant differences between smokers and non-smokers in the rate or course of fusion as previously reported.

Modification of gene expression induced in human osteogenic and osteosarcoma cells by culture on a biphasic calcium phosphate bone substitute

Bone hybrids made of bioceramics seeded with mesenchymal or osteoblastic cells are very promising alternatives to autologous bone graft. Along this line, the development of in vitro models, dedicated to analyze the influence of these biomaterials on osteogenic cells, will help to improve the performance of these bone substitutes. In the present work we analyzed the effects of a macroporous biphasic calcium phosphate ceramic (BCP, Triosite) on three different human osteosarcoma cell lines and on human primary osteogenic cells and compared this culture substratum to traditional culture on plastic. We showed that all these osteoblastic cells adhere and proliferate on the trabecular BCP blocks, with a different spatial organization for osteosarcoma cells compared to normal osteogenic cells. We also demonstrated that osteoblastic marker genes such as Cbfa1, type I collagen, osteonectin, osteopontin, and osteocalcin were expressed at similar levels by these cells cultured on either substratum, suggesting that adhesion to BCP does maintain the osteoblastic phenotype of these cells. Next, we provided the first evidence of differences of cytokine expression profiles revealed on this Ca-P ceramic as compared to expression in classical culture. These modifications affected the expression of cytokines such as TGF-beta1, G-CSF, and IL-3 and were quantitatively different between osteosarcoma cells and normal osteogenic cells. Given the role of these cytokines in bone biology and in hematopoiesis, these results obtained in vitro suggest that the BCP ceramic studied here could stimulate osteogenesis in vivo by activating cellular processes during bone formation and healing. This study highlights the notion that the nature of the culture substratum must be taken into account when studying bone cell biology in vitro. Owing to the nature and spatial organization of the BCP, our hypothesis is that culture on BCP is closer to the physiological situation than culture on plastic.

Interpositional arthroplasty (Jones technique) for the treatment of herniated lumbar disks: a modification of the soft posterior lumbar interbody fusion

Sixty-six patients underwent posterior lumbar interpositional arthroplasty using a combination of calcium sulfate pellets, decompression bone, and autologous growth factors. Patients who underwent this modification of the soft posterior lumbar interbody fusion (PLIF) (Jones technique) were evaluated using clinical and radiographic ratings. The Jones technique produced significantly improved clinical pain scores in all patients, reducing back pain by 71% and leg pain by 90%. Furthermore, 93% of patients achieved at least 50% opacity of the disk space area. The Jones technique for the soft PLIF provided reduction of pain and stabilized the disk space height in addition to decreasing morbidity and cost.