Bone grafting alternatives in spinal surgery

Influência da decorticação vertebral na neoformação dos tecidos da interface do enxerto ósseo

OBJETIVO: Determinar a influência da decorticação dos elementos posteriores da coluna vertebral na integração do enxerto ósseo, considerando a avaliação quantitativa e qualitativa dos tecidos (ósseo, cartilaginoso e fibroso) da interface entre o leito receptor e o enxerto ósseo. MÉTODOS: Foram utilizados 24 ratos Wistar, divididos em dois grupos de acordo com a realização da decorticação do leito receptor do enxerto. Foi utilizado enxerto autólogo derivado dos processos espinhosos das duas primeiras vértebras lombares. A neoformação tecidual na interface entre o leito receptor e seu enxerto ósseo foi avaliada após três semanas por meio de análise histomorfométrica. RESULTADOS: No grupo de animais com o leito receptor decorticado a média da porcentagem de osso neoformado foi de 40%±6,1, e 7,7%± 3,5 no grupo não decorticado (p=0,0001). A média da porcentagem de formação do tecido cartilaginoso no grupo decorticado foi de 7,2%±3,5, no não decorticado de 10,9%±5,6 (p=0,1123). A formação de tecido fibroso no grupo decorticado apresentou média de 8,6%±3,9 e no não decorticado e 24%±10,1, (p=0,0002). CONCLUSÕES: A decorticação acelerou o processo histológico da integração do enxerto ósseo. Ocorrendo maior produção de tecido ósseo neoformado e predomínio da ossificação do tipo intramembranosa no grupo de animais nos quais a decorticação foi realizada.

Ultrasound enhances recombinant human BMP-2 induced ectopic bone formation in a rat model

Two methods to improve bone repair include the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) and low-intensity pulsed ultrasound (LIPUS). The present study was designed to determine if LIPUS enhances the effect of rhBMP-2-induced bone formation in a well characterized ectopic implant model. Absorbable collagen sponges loaded with 0-, 1-, 2.5- or 5-microg doses of rhBMP-2 were implanted subcutaneously in 11-week-old, male Long Evans rats, followed by daily 20-min LIPUS or sham LIPUS treatment beginning 1 d after surgery. Explanted sponges were assessed for bone volume, mineral density and mineral content by microcomputed tomography (microCT). At two weeks, LIPUS had no effect on rhBMP-2-induced bone formation, but at four weeks, LIPUS increased bone volume in the 1-microg rhBMP-2-treated implants 117.7-fold (0.02 +/- 0.04 mm(3)vs. 2.07(S.E.M.) +/- 1.67 mm(3);p = 0.028), and 2.3-fold in the 5-microg dose implants (5.96 +/- 3.68 mm(3)vs. 13.52 +/- 6.81 mm(3);p = 0.077) compared with sham LIPUS. Bone mineral density was not affected by LIPUS treatment. Total mineral content followed the same pattern as bone volume. Histologic staining for mineralized tissue was consistent with the microCT observations. The present study is the first to demonstrate that LIPUS enhances bone formation induced by rhBMP-2.

Clinical and radiological evaluation of Trabecular Metal and the Smith-Robinson technique in anterior cervical fusion for degenerative disease: a prospective, randomized, controlled study with 2-year follow-up

A prospective, randomized, controlled study was carried out to compare the radiological and clinical outcomes after anterior cervical decompression and fusion (ACDF) with Trabecular Metal (TM) to the traditional Smith-Robinson (SR) procedure with autograft. The clinical results of cervical fusion with autograft from the iliac crest are typically satisfactory, but implications from the donor site are frequently reported. Alternative materials for cervical body interfusion have shown lower fusion rates. Trabecular Metal is a porous tantalum biomaterial with structure and mechanical properties similar to that of trabecular bone and with proven osteoconductivity. As much as 80 consecutive patients planned for ACDF were randomized for fusion with either TM or tricortical autograft from the iliac crest (SR) after discectomy and decompression. Digitized plain radiographic images of 78 (98%) patients were obtained preoperatively and at 2-year follow-up and were subsequently evaluated by two senior radiologists. Fusion/non-fusion was classified by visual evaluation of the A-P and lateral views in forced flexion/extension of the cervical spine and by measuring the mobility between the fused vertebrae. MRI of 20 TM cases at 2 years was successfully used to assess the decompression of the neural structures, but was not helpful in determining fusion/non-fusion. Pain intensity in the neck, arms and pelvis/hip were rated by patients on a visual analog scale (VAS) and neck function was rated using the Neck Disability Index (NDI) the day before surgery and 4, 12 and 24 months postoperatively. Follow-ups at 12 and 24 months were performed by an unbiased observer, when patients also assessed their global outcome. Fusion rate in the SR group was 92%, and in the TM group 69% (P < 0.05). The accuracy of the measurements was calculated to be 2.4 degrees . Operating time was shorter for fusion with TM compared with autograft; mean times were 100 min (SD 18) and 123 min (SD 23), respectively (P = 0.001). The patients' global assessments of their neck and arm symptoms 2 years postoperatively for the TM group were rated as 79% much better or better after fusion with TM and 75% using autograft. Pain scores and NDI scores were significantly improved in both groups when compared with baseline at all follow-ups, except for neck pain at 1 year for the TM group. There was no statistically significant difference in clinical outcomes between fusion techniques or between patients who appeared radiologically fused or non-fused. There was no difference in pelvic/hip pain between patients operated on with or without autograft. In our study, Trabecular Metal showed a lower fusion rate than the Smith-Robinson technique with autograft after single-level anterior cervical fusion without plating. There was no difference in clinical outcomes between the groups. The operative time was shorter with Trabecular Metal implants.

From natural bone grafts to tissue engineering therapeutics: Brainstorming on pharmaceutical formulative requirements and challenges

Tissue engineering is an emerging multidisciplinary field of investigation focused on the regeneration of diseased or injured tissues through the delivery of appropriate molecular and mechanical signals. Therefore, bone tissue engineering covers all the attempts to reestablish a normal physiology or to speed up healing of bone in all musculoskeletal disorders and injuries that are lashing modern societies. This article attempts to give a pharmaceutical perspective on the production of engineered man-made bone grafts that are described as implantable tissue engineering therapeutics, and to highlight the importance of understanding bone composition and structure, as well as osteogenesis and bone healing processes, to improve the design and development of such implants. In addition, special emphasis is given to pharmaceutical aspects that are frequently minimized, but that, instead, may be useful for formulation developments and in vitro/in vivo correlations.

Regulation of mechanical signals in bone

OBJECTIVES

Response of the skeleton to application and removal of specific mechanical signals is discussed. Anabolic effects of high-frequency, low-magnitude vibrations, a mechanical intervention with a favorable safety profile, as well as the modulation of bone loss by genetic and epigenetic factors during disuse are highlighted.

METHODS

Review.

RESULTS

Bone responds to a great variety of mechanical signals and both high- and low-magnitude stimuli can be sensed by the skeleton. The ability of physical signals to influence bone morphology is strongly dependent on the signal's magnitude, frequency, and duration. Loading protocols at high signal frequencies (vibrations) allow a dramatic reduction in the magnitude of the signal. In the axial skeleton, these signals can be anabolic and anti-catabolic and increase the structural strength of the tissue. They further have shown potential in maxillofacial applications to accelerate the regeneration of bone within defects. Bone's sensitivity to the application and removal of mechanical signals is heavily under the control of the genome. Bone loss modulated by the removal of weight-bearing from the skeleton is profoundly influenced by factors such as genetics, gender, and baseline morphology.

CONCLUSIONS

Adaptation of bone to functional challenges is complex but it is clear that more is not necessarily better and that even very low-magnitude mechanical signals can be anabolic. The development of effective biomechanical interventions in areas such as orthodontics, craniofacial repair, or osteoporosis will require the identification of the specific components of bone's mechanical environment that are anabolic, catabolic, or anti-catabolic.

Evaluation of bone matrix and demineralized bone matrix incorporated PLGA matrices for bone repair

The aim of this study was to evaluate the composite matrices prepared using Poly(lactic-co-glycolic acid)- PLGA (85:15) by incorporating human bone matrix (BM) powder or demineralized bone matrix (DBM) powder with the weight ratio of polymer: BM or DBM (75:25) to apply for bone repair. Murine Bone Marrow Stromal Cell (BMSC) attachment was studied with different time points at 30 min, 1 h, 2 h, 4 h, and 6 h for BM/PLGA, DBM/PLGA and PLGA control matrices. All types of matrices were linearly increased the BMSC attachment with the increase of time. Significantly higher number of BMSCs was attached to the both BM/PLGA and DBM/PLGA matrices after 2 h compared to the controls. If BM or DBM is incorporated into biodegradable PLGA matrices and cultured with BMSCs, those composite matrices could be potentially used for bone tissue engineering applications. In addition, particle migration and handling difficulties in DBM powder in clinical applications eliminate using a PLGA matrix. Furthermore, we have observed that DBM/PLGA matrices were structurally stronger compared to the BM/PLGA or control PLGA matrices when they exposed to physiological environment for 72 days.

In vitro proliferation and osteoblastic phenotype expression of cells derived from human vertebral lamina and iliac crest

STUDY DESIGN

Osteoblastic cells derived from vertebral lamina and iliac crest were isolated and cultured under the same conditions (osteogenic medium, pH, temperature, and CO2 levels).

OBJECTIVE

To compare proliferation and expression of osteoblastic phenotype of cells derived from vertebral lamina and iliac grafting.

SUMMARY OF BACKGROUND DATA

Many factors play a role in the success of bone graft in spinal fusion including osteoblastic cell population. Two common sources of graft are vertebral lamina and iliac crest, however, differences in proliferation and osteoblastic phenotype expression between cells from these sites have not been investigated.

METHODS

Cells obtained from cancellous bone of both vertebral lamina and iliac crest were cultured and proliferation was evaluated by direct cell counting and viability detected by Trypan blue. Alkaline phosphatase (ALP) activity was evaluated by thymolphthalein release from thymolphthalein monophosphate and matrix mineralization by staining with alizarin red S. Gene expression of ALP, osteocalcin, runt-related transcription factor 2, Msh homeobox 2, bone morphogenetic protein 7, intercellular adhesion molecule 1 precursor, osteoprotegerin, and receptor activator of NF-kB ligand was analyzed by real-time PCR. All comparisons were donor-matched.

RESULTS

Proliferation was greater at days 7 and 10 in cells from vertebral lamina compared with ones from iliac crest without difference in cell viability. ALP activity was higher in cells from vertebral lamina compared with cells from iliac crest at days 7 and 10. At 21 days, mineralized matrix was higher in cells derived from vertebral lamina than from iliac crest. At day 7, gene expression of ALP, osteocalcin, runt-related transcription factor 2, Msh homeobox 2, bone morphogenetic protein 7, intercellular adhesion molecule 1 precursor, receptor activator of NF-kB ligand, and osteoprotegerin was higher in cells derived from vertebral lamina compared with iliac crest.

CONCLUSION

Cell proliferation and osteoblastic phenotype development in cells derived from cancellous bone were more exuberant in cultures of vertebral lamina than of iliac crest.

Mesenchymal stem cell and gene therapies for spinal fusion

THE IDEAL GRAFT material to promote spinal fusion should possess osteoconductive, osteoinductive, and osteogenic properties. Although autogenous bone graft has all three qualities and is the standard for comparison, research has focused on finding alternatives that have similar efficacy but not the morbidities associated with graft donor sites. Efforts have focused on various osteoconductive scaffolds and introduction of osteoinductive proteins, including bone morphogenetic protein. Recently, interest in using osteoprogenitor cells, or osteogenesis, for spinal fusion has increased. Bone marrow aspiration allows the introduction of mesenchymal stem cells and ultimately osteoblasts to promote fusion. Preclinical studies suggest that the addition of osteoprogenitor cells to various osteoconductive materials results in a fusion rate similar to that of autograft. There is growing recognition that local gene therapy has the benefit of delivering therapeutic genes that encode novel osteoinductive proteins. Gene delivery offers an alternative to local implantation of recombinant protein, which typically requires high doses of the protein to result in a sufficient osteoinductive response. The findings of animal studies demonstrate that gene therapy results in sustained and regulated production of desired osteoinductive proteins and is efficacious in promoting spinal fusion; however, before treatment in humans can be undertaken, obstacles such as the safety profile, host immune response, transfection rates with insufficient transgene expression, and imprecise control of the timing of transgene expression must be overcome. In this review, the authors summarize the latest research efforts under way to promote spinal fusion with osteoprogenitor cells and gene therapy and discuss the clinical implications of these treatments.

Healing of ungrafted bone defects of the talus after benign tumour removal

BACKGROUND

Curettage of benign tumours commonly results in significant bone defects that are reconstructed with autologous grafts, allografts, bone cement or bone substitute. We have treated such defects in the talus without reconstruction with bone or any other material. We now report the healing of these ungrafted defects in eight patients treated with curettage for benign talar tumours.

METHODS

Eight consecutive patients were reviewed retrospectively at a mean follow-up of 82 months (range: 28-180 months). Mean age was 21.7 years (range: 12.3-31.3 years) and mean defect size was 16.5 cm(3) (range: 3.5-48 cm(3)). Outcome measures included time to radiological consolidation, ankle pain and stiffness, talar collapse, and tibiotalar joint osteoarthritis.

RESULTS

Full consolidation of the defect occurred within 6-12 months in all patients. One patient had minor discomfort over the scar, but there was no ankle joint pain. Two patients had some ankle stiffness, although one had established ankle osteoarthritis prior to surgery. No talar collapse, fracture or new significant osteoarthritis of the ankle was observed.

CONCLUSIONS

We conclude that bone grafting is not a necessary adjunct to the curettage of talar lesions.

Extremely small-magnitude accelerations enhance bone regeneration: a preliminary study

High-frequency, low-magnitude accelerations can be anabolic and anticatabolic to bone. We tested the hypothesis that application of these mechanical signals can accelerate bone regeneration in scaffolded and nonscaffolded calvarial defects. The cranium of experimental rats (n = 8) in which the 5-mm bilateral defects either contained a collagen scaffold or were left empty received oscillatory accelerations (45 Hz, 0.4 g) for 20 minutes per day for 3 weeks. Compared with scaffolded defects in the untreated control group (n = 6), defects with a scaffold and subject to oscillatory accelerations had a 265% greater fractional bone defect area 4 weeks after the surgery. After 8 weeks of healing (1-week recovery, 3 weeks of stimulation, 4 weeks without stimulation), the area (181%), volume (137%), and thickness (53%) of the regenerating tissue in the scaffolded defect were greater in experimental than in control animals. In unscaffolded defects, mechanical stimulation induced an 84% greater bone volume and a 33% greater thickness in the defect. These data provide preliminary evidence that extremely low-level, high-frequency accelerations can enhance osseous regenerative processes, particularly in the presence of a supporting scaffold.

Histologic evaluation of high speed burr shavings collected during spinal decompression surgery

In spinal decompression and fusion surgery, a high speed burr is often used to remove bony material. The generated bone shavings are typically washed away and discarded. This study histologically examined the content of burr shavings to determine whether the collected tissue has the potential to augment local autograft. Our findings verified that burr shavings collected during spinal decompression are primarily composed of bone (65%) with blood product (32%). The bone shavings appear to remain viable after burring, as there was no microscopic evidence of damage to the cells. These findings indicate that bone shavings can be easily collected and could be added to local laminectomy bone with minimal cost. This technique is also beneficial given that it does not increase morbidity, as does iliac crest bone graft harvesting. Furthermore, the putty-like consistency of the bone shavings may facilitate the placement of morselized autograft bone. Despite these advantages, collected bone shavings are by no means a substitute for autograft or allograft bone. Their osteogenic potential is not comparable to that of iliac crest bone and the shavings lack the structural scaffolding of allograft bone. This technique, however, provides a resource for augmenting local autograft during spinal fusion, and is not associated with any significant cost or effort. Future studies should compare the clinical and radiographic fusion outcomes of high speed burr bony shavings combined with local laminectomy bone versus either iliac crest autograft or local laminectomy bone used with other bone graft extenders.

Comparing various off-the-shelf methods for bone tissue engineering in a large-animal ectopic implantation model: bone marrow, allogeneic bone marrow stromal cells, and platelet gel

Construction of bone grafts for regenerative medicine would highly benefit from off-the-shelf components, such as allogeneic bone marrow stromal cells (BMSCs) and blood-derived growth factors from platelet concentrate. Although allogeneic BMSCs are considered immunosuppressive, their use in transplantation studies is still cautioned. In this study, we used off-the-shelf goat allogeneic BMSCs, per-operatively aspirated bone marrow (BM) and platelet gel (PLG). Ten goats received six different hybrid constructs consisting of biphasic calcium phosphate scaffolds seeded with PLG or plasma that were mixed with BM, allogeneic BMSCs or left without cells. All constructs were implanted in the paraspinal muscles for 9 weeks. Fluorochromes were administered at 2, 3, and 5 weeks to assess onset of bone formation. Analysis revealed that the scaffolds without cells yielded small amounts of bone. Allogeneic BMSCs had a positive effect on the amount and early onset of bone formation. Fresh BM did not enhance ectopic bone formation. The PLG, which contained higher levels of transforming growth factor beta than plasma, did not result in more bone either. Fluorochrome incorporation results indicate that the presence of seeded cells in the constructs accelerates bone formation. This study shows a potential role of allogeneic BMSCs in bone tissue-engineering research.

Autograft versus allograft with or without demineralized bone matrix in posterolateral lumbar fusion in rabbits

Object

Posterolateral spinal fusions are performed to treat different spinal disorders. Autograft continues to be the gold standard; it is, however, associated with donor site morbidity and limited sources. Allograft has been used, but has been reported to result in lower fusion rates. Demineralized bone matrix (DBM) has also been used and reportedly increases the fusion rate in a variety of critical defect models. Different forms of DBM are available, not all have been independently studied. To evaluate the effect of a xenogenic DBM added to allograft on the fusion rate of posterolateral lumbar spine arthrodesis the authors designed an experimental study comparing posterolateral fusion rate using autograft, allograft, and allograft plus a xenogenic DBM in a validated animal model.

Methods

A bilateral, 1-level (L4–5) intertransverse process fusion was performed in 45 male New Zealand rabbits. Iliac crest bone graft was harvested bilaterally from each rabbit. The rabbits were randomly assigned to 3 groups: Group I, Autograft, 15 rabbits; Group II, Allograft, 15 rabbits; and Group III, Allograft plus DBM in a paste form (Dynagraft). The animals were killed 8 weeks after surgery. Fusion was assessed radiographically and by manual palpation by 2 independent observers. The results were analyzed using the Fisher exact test and chi-square test.

Results

The fusion rate was 46.6% (7 of 15 rabbits) in the autograft group, 33.3% (5 of 15 rabbits) in the allograft group, and 33.3% (5 of 15 rabbits) in the allograft plus DBM group (p > 0.05).

Conclusions

Autograft produced a higher fusion rate than allograft in this spinal fusion rabbit model, but the difference was not statistically significant. Allograft plus xenogenic DBM showed the same fusion rate as allograft alone.

Early and intermediate follow-up results after treatment of degenerative disc disease with the Bryan cervical disc prosthesis: single- and multiple-level

STUDY DESIGN

Our clinical study design was prospective, concurrently enrolled and single-center trial of the new functional intervertebral cervical disc prosthesis (Medtronic Sofamor Danek, Memphis, TN) in the treatment of patients with single-level and multiple-level degenerative disc disease of the cervical spine.

OBJECTIVE

The study was designed to investigate the surgical technology skills and clinical effects of Bryan cervical disc prosthesis in Chinese, and to observe the stability and range of movement in the early and immediate postoperative period.

SUMMARY OF BACKGROUND DATA

Recently, motion preservation has come to the forefront of emerging technologies in spine surgery. This is the important background information of the emergence of cervical arthroplasty as an alternative to arthrodesis that offers the promise of restoring normal spinal movement and reduces a kinematic strain on adjacent segments.

METHODS

Nineteen patients (23 discs) had spinal arthroplasty with placement of the Bryan cervical artificial disc prosthesis in our hospital. Clinical and radiologic follow-up was performed. The radiographic parameters evaluated included the treated segments and the overall curvature of the cervical spine.

RESULTS

All the patients were observed up from 8 months to 42 months (average 24 months). According to Odom's scale, all of 19 patients (23 levels) had excellent to good outcome. The range of movement recovered to the preoperative value during the follow up. The treated segment ultimately showed preservation of movement when compared with preoperative levels. No prosthesis subsidence or excursion was identified.

CONCLUSION

Arthroplasty using the Bryan disc seemed to be safe and provided encouraging clinical and radiologic outcome in our study. Although early and intermediate results are promising, this is also a relatively new approach, long-term follow up studies are required to prove its efficacy and its ability to prevent adjacent segment disease.

The use of bone morphogenetic protein in spine fusion

BACKGROUND CONTEXT

Because pseudarthrosis remains a clinically significant complication after spinal arthrodesis, the role of recombinant bone morphogenetic proteins (BMPs) is continually evaluated in spine surgery.

PURPOSE

This article reviews the important literature in clinical research involving the use of BMPs in the augmentation of spinal fusion.

STUDY DESIGN/SETTING

Review article.

METHODS

A literature search was performed via MEDLINE through PubMed with the dates January 1960 to July 2007 using the keywords "bone morphogenetic protein, BMP, spinal arthrodesis, and/or bone healing." Pertinent preclinical and clinical publications were chosen based on relevance and quality for inclusion in this study.

RESULTS

Publications focused on the historical context and potential clinical applications using BMP were selected to delineate the risks, benefits, and current indications for the augmentation of spinal arthrodesis.

CONCLUSIONS

Although multiple commercially available recombinant BMPs have demonstrated clinical success in interbody and posterolateral fusions, the associated costs preclude its routine use in spinal arthrodesis. The spine surgeon must assess each patient individually based on age, bone quality, diagnosis, comorbidities, and risks of nonunion to determine the cost effectiveness of the use of BMP to augment spinal fusion.

An Alternative Source of Autograft Bone for Spinal Fusion: the Femur: Technical Case Report

Objective:

Autograft bone obtained from the iliac crest remains the “gold standard” for spinal fusion. For various reasons, including previous harvesting or pelvic dysmorphism, the iliac crest bone graft may not be available to the spinal surgeon. We present a novel use of a common orthopedic procedure, intramedullary reaming, for obtaining autograft for revision spinal fusion.

Methods:

A 47-year-old woman presented with failed back syndrome after multiple lumbar surgeries with previous bilateral iliac crest bone harvest. A commercially available reaming system (Synthes Reamer-Irrigator-Aspirator; Synthes USA, West Chester, PA) was introduced into the left intramedullary canal of the femur while the patient remained in the prone position. Using continuous irrigation and aspiration, the reaming debris was collected and used as autograft for the subsequent spinal fusion.

Results:

The patient underwent a successful L4–L5, L5–S1 transforaminal lumbar inter-body fusion with L3–S1 pedicle screw fixation. No complications from the femoral reaming were observed, and 6-month follow-up x-rays demonstrated osseous fusion.

Conclusion:

Femoral reaming provides an alternative source of autograft bone when other sources are unavailable.

Influence of decortication of the recipient graft bed on graft integration and tissue neoformation in the graft-recipient bed interface

The objective of the present study was to assess the influence of decortication of the posterior elements of the vertebra (recipient bed) and the nature of the bone graft (cortical or cancellous bone) on graft integration and bone, cartilage and fiber neoformation in the interface between the vertebral recipient bed and the bone graft. Seventy-two male Wistar rats were divided into four experimental groups according to the presence or absence of decortication of the posterior vertebral elements and the use of a cortical or cancellous bone graft. Group I--the posterior elements were decorticated and cancellous bone used. Group II--the posterior elements were decorticated and cortical graft was used. Group III--the posterior elements were not decorticated and cancellous graft was used. Group IV--the posterior elements were not decorticated and cortical graft was used. The animals were killed 3, 6 and 9 weeks after surgery and the interface between the posterior elements and the bone graft was subjected to histomorphometric evaluation. Mean percent neoformed bone was 40.8% in group I (decortication and cancellous graft), 39.13% in group II (decortication and cortical graft), 6.13% in group III (non-decorticated and cancellous graft), and 9.27% in group IV (non-decorticated and cortical graft) for animals killed at 3 weeks (P = 0.0005). For animals killed at 6 weeks, the mean percent was 38.53% for group I, 40.40% for group II, 10.27% for group III, and 7.6% for group IV (P = 0.0005), and for animals killed at 9 weeks, the mean was 25.93% for group I, 30.6% for group II, 16.4% for group III, and 18.73% for group IV (P = 0.0026). The mean percent neoformed cartilage tissue was 8.36% for group I, 7.46% for group II, 11.1% for group III, and 9.13% for group IV for the animals killed at 3 weeks (P = 0.6544); 6.6% for group I, 8.07% for group, 7.47% for group III and 6.13% for group IV (P = 0.4889) for animals killed at 6 weeks, and 3.13% for group I, 4.06% for group II, 10.53% for group III and 12.07% for group IV (P = 0.0006) for animals killed at 9 weeks. Mean percent neoformed fibrous tissue was 11% for group I, 6.13% for group II, 26.27% for group III and 21.87% for group IV for animals killed at 3 weeks (P = 0.0008); 7.67% for group I, 7.1% for group II, 9.8% for group III and 10.4% for group IV (P = 0.7880) for animals killed at 6 weeks, and 3.73% for group I, 4.4% for group II, 6.67% for group III and 6.8% for group IV (P = 0.0214) for animals killed at 9 weeks. The statistically significant differences in percent tissue formation were related to decortication of the posterior elements. The use of a cortical or cancellous graft did not influence tissue neoformation. Ossification in the interface of the recipient graft bed was of the intramembranous type in the decorticated animals and endochondral type in the non-decorticated animals.

Enhancement of graft bone healing by intermittent administration of human parathyroid hormone (1-34) in a rat spinal arthrodesis model

Bone grafting is commonly used to treat skeletal disorders associated with large bone defect or unstable joint. It can take several months, however, to achieve a solid union and bony fusion sometimes delays or fails especially in osteoporosis patients. Therefore, we used a rat spinal arthrodesis model to examine whether intermittent administration of human PTH(1-34) accelerates bone graft healing. Eighty-two male Sprague-Dawley rats underwent posterolateral spinal arthrodesis surgery using autologous bone grafts. Animals were given daily subcutaneous injections of hPTH(1-34) (40 microg/kg/day PTH group) or 0.9% saline vehicle (control group) from immediately after surgery till death. Five rats each were killed 2, 4, 7, and 14 days after the surgery, and mRNA expression analysis was performed on harvested grafted bone. Seven rats each were killed 14, 28, and 42 days after the surgery, and the lumbar spine, which contained the grafted spinal segment, was subjected to fusion assessment, microstructural analysis using three-dimensional micro-computed tomography, and histologic examination. Serum bone metabolism markers were analyzed. The results indicated that PTH administration decreased the time required for graft bone healing and provided a structurally superior fusion mass in the rat spinal arthrodesis model. PTH administration increased the fusion rate on day 14 (14% in the control group and 57% in the PTH group), accelerated grafted bone resorption, and produced a larger and denser fusion mass compared to control. mRNA expression of both osteoblast- and osteoclast-related genes was upregulated by PTH treatment, and serum bone formation and resorption marker levels were higher in the PTH group than in the control group. Histologically calculated mineral apposition rate, mineralized surface and osteoclast surface were also higher in the PTH group than in the control group. These findings suggest that intermittent administration of PTH(1-34) enhanced bone turn over dominantly on bone formation at the graft site, leading to the acceleration of the spinal fusion. Based on the results of this study, intermittent injection of hPTH(1-34) might be an efficient adjuvant intervention in spinal arthrodesis surgery and all other skeletal reconstruction surgeries requiring bone grafts.

Clinical applications of BMP-7/OP-1 in fractures, nonunions and spinal fusion

Since the identification of the osteogenic protein-1 (OP-1) gene, also called bone morphogenetic protein-7 (BMP-7), almost 20 years ago, OP-1 has become one of the most characteristic members of the BMP family. The biological activity of recombinant human OP-1 has been defined using a variety of animal models. These studies have demonstrated that local implantation of OP-1 in combination with a collagen matrix results in the repair of critical size defects in long bones and in craniofacial bones and the formation of bony fusion masses in spinal fusions. Clinical trials investigating long bone applications have provided supportive evidence for the use of OP-1 in the treatment of open tibial fractures, distal tibial fractures, tibial nonunions, scaphoid nonunions and atrophic long bone nonunions. Clinical studies investigating spinal fusion applications have provided supportive evidence for the use of OP-1 in posterolateral lumbar models and compromised patients as an adjunct or as a replacement for autograft. Both long bone repair and spinal fusion studies have demonstrated the efficacy and safety of OP-1 by clinical outcomes and radiographic measures. Future clinical investigations will be needed to better define variables, such as dose, scaffold and route of administration. Clearly the use of BMPs in orthopaedics is still in its formative stage, but the data suggest an exciting and promising future for the development of new therapeutic applications.

Vertical bone augmentation with granulated brushite cement set in glycolic acid

Brushite cements are a biocompatible materials that are resorbed in vivo. A new cement composed of a mixture of monocalcium phosphate (MCP) and beta-tricalcium phosphate (beta-TCP) that sets using glycolic acid (GA) was synthesized and characterized. After setting, the cement composition, derived from X-ray diffraction, was 83 wt % brushite and 17 wt % beta-TCP with an average brushite crystal size of about 2.6 +/- 1.4 microm. The cement has a diametral tensile strength of 2.9 +/- 0.7 MPa. Granules prepared from the set-cement were used as grafting material in bone defects on rabbit calvaria for evaluating in vivo its bone regeneration capacity. Considerable cement resorption, improvement in the bone mineral density, and bone neoformation was observed after 4 weeks of the granules' implantation.

Taking tissue-engineering principles into theater: augmentation of impacted allograft with human bone marrow stromal cells

Human bone marrow contains bone progenitor cells that arise from multipotent mesenchymal stem cells. Seeding bone progenitor cells onto a scaffold can produce a 3D living composite with significant mechanical and biological potential. This article details laboratory and clinical findings from two clinical cases, where different proximal femoral conditions were treated using impacted allograft augmented with marrow-derived autogenous progenitor cells. Autologous bone marrow was seeded onto highly washed morselized allograft and impacted. Samples of the impacted graft were also taken for ex vivo analysis. Both patients made an uncomplicated clinical recovery. Imaging confirmed defect filling with encouraging initial graft incorporation. Histochemical and alkaline phosphatase staining demonstrated that a live composite graft with osteogenic activity had been introduced into the defects. These studies demonstrate that marrow-derived cells can adhere to highly washed morselized allograft, survive the impaction process and proliferate with an osteoblastic phenotype, thus creating a living composite.

Prefabrication of Vascularized Bone Flap by Demineralized Bone Matrix

Demineralized bone matrix (DBM) has been reported to have osteoconductive and osteoinductive properties and has been clinically used as a bone graft alternative. In the present study we attempted to generate a vascularized bone flap by subcutaneous implantation of DBM with a vascular loop to provide blood supply in a rat model. Thirty male Sprague-Dawley rats were divided into two groups according to the presence or absence of blood supply. In the experimental group, the bone flap was created by application of 0.4 mL of DBM onto two pieces of gelatin sponge sheets between which a vascular loop was sandwiched. A prefabricated flap without a vascular loop served as the control. The flaps were biopsied at three different time intervals postoperatively (2, 4, and 6 weeks). The results showed that DBM induced subcutaneous bone formation in both of the groups. However, in the nonvascularized group, the amount of bony tissue had decreased at four postoperative weeks and continued to do so afterwards. In contrast, bone formation was active at four weeks in the vascularized group. Our study indicated that implantation of DBM can prefabricate a bone flap. Blood supply to the flap is considered a key factor of the success of this prefabrication.

Arthroscopic ankle arthrodesis: factors influencing union in 39 consecutive patients

BACKGROUND

Arthroscopic ankle arthrodesis is an effective alternative to open techniques with established advantages in select patient populations. The purpose of this study was to evaluate patients who had arthroscopic ankle arthrodesis for end-stage arthritis with minimal to no deformity of the ankle and to report factors influencing union.

METHODS

Thirty-nine consecutive patients had arthroscopic ankle arthrodesis between 1994 and 2003. Clinical records and radiographs were retrospectively reviewed to evaluate variables that could predispose patients to nonunion. Union outcomes were correlated with etiology of arthritis, ankle deformity, medical co-morbidities, and the use of demineralized bone matrix or platelet-rich plasma. Arthroscopic ankle arthrodesis was accomplished with a consistent technique using crossed transmalleolar cannulated screw fixation.

RESULTS

Thirty-four of 39 patients (87.2%) achieved radiographic and clinical union. The average time to fusion was 47 (range 37 to 70) days. Poor bone quality and inherent positional ankle deformity were identified as risk factors for nonunion. Patients who smoked, had diabetes mellitus, peripheral neuropathy, or other medical co-morbidities attained ankle union in nearly all cases. In obese patients, there was an observed trend towards ankle nonunion (relative risk 5.81, p = 0.049, Fisher's Exact test). The addition of demineralized bone matrix or platelet-rich plasma did not improve the rate of ankle union. Aside from nonunion, 10 patients developed minor complications.

CONCLUSION

Arthroscopic ankle arthrodesis achieves high union rates, facilitates short time to union, and permits rapid patient mobility. Careful patient selection is important for the procedure. Synthetic allograft or platelet-rich plasma did not enhance the fusion rate. Obese patients showed a trend towards nonunion in this series.

Evaluation of donor site pain after anterior iliac crest harvesting for cervical fusion: a prospective study on 50 patients

BACKGROUND

Autologous anterior iliac crest bone graft is still widely considered the gold standard for anterior cervical fusion after discectomy or corporectomy. Postoperative pain at the donor site is one of the main disadvantages to this technique. This prospective study aimed to evaluate pain at the donor site, after careful, standardised bone harvesting.

METHODS

From March 2003 to March 2004, a prospective study was performed in a single neurosurgical department on 50 patients who underwent anterior iliac crest bone harvesting using a standard and careful surgical technique. During a one year follow-up, patient donor site pain was assessed with a Visual Analogous Scale (VAS) at 2, 7 and 60 days from surgery and finally, by a telephone interview, at one year.

FINDINGS

The duration of time in hospital ranged from 4 to 9 days. On the 2(nd) day after surgery, pain, according to the VAS score, was recorded as being >7 by 4 patients (8%), 5-7/10 by 27 patients and >5/10 in 19 cases. On the 7(th) day after surgery, none of the patients reported any VAS > 7, 1 patient's VAS score was 6/10 and 49 patients had a VAS < 5. At 2 month follow-up, 45 patients were completely without pain (VAS 0) and the remaining 5 had a VAS < 5. At one year, 46 patients reported no pain (one patient was lost to follow-up); three continued to have pain <5 in VAS scale.

CONCLUSIONS

After harvesting of bone from the iliac crest, using a standardised approach based on anatomised principles, most patients do not experience persisting pain at the donor site.

Recombinant human BMP-2 and allograft compared with autogenous bone graft for reconstruction of diaphyseal tibial fractures with cortical defects. A randomized, controlled trial

BACKGROUND

Currently, the treatment of diaphyseal tibial fractures associated with substantial bone loss often involves autogenous bone-grafting as part of a staged reconstruction. Although this technique results in high healing rates, the donor-site morbidity and potentially limited supply of suitable autogenous bone in some patients are commonly recognized drawbacks. The purpose of the present study was to investigate the benefit and safety of the osteoinductive protein recombinant human bone morphogenetic protein-2 (rhBMP-2) when implanted on an absorbable collagen sponge in combination with freeze-dried cancellous allograft.

METHODS

Adult patients with a tibial diaphyseal fracture and a residual cortical defect were randomly assigned to receive either autogenous bone graft or allograft (cancellous bone chips) for staged reconstruction of the tibial defect. Patients in the allograft group also received an onlay application of rhBMP-2 on an absorbable collagen sponge. The clinical evaluation of fracture-healing included an assessment of pain with full weight-bearing and fracture-site tenderness. The Short Musculoskeletal Function Assessment (SMFA) was administered before and after treatment. Radiographs were used to document union, the presence of extracortical bridging callus, and incorporation of the bone-graft material.

RESULTS

Fifteen patients were enrolled in each group. The mean length of the defect was 4 cm (range, 1 to 7 cm). Ten patients in the autograft group and thirteen patients in the rhBMP-2/allograft group had healing without further intervention. The mean estimated blood loss was significantly less in the rhBMP-2/allograft group. Improvement in the SMFA scores was comparable between the groups. No patient in the rhBMP-2/allograft group had development of antibodies to BMP-2; one patient had development of transient antibodies to bovine type-I collagen.

CONCLUSIONS

The present study suggests that rhBMP-2/allograft is safe and as effective as traditional autogenous bone-grafting for the treatment of tibial fractures associated with extensive traumatic diaphyseal bone loss.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence.

Accelerated repair of cortical bone defects using a synthetic extracellular matrix to deliver human demineralized bone matrix

Injectable hydrogel and porous sponge formulations of Carbylan-GSX, a crosslinked synthetic extracellular matrix (ECM), were used to deliver human demineralized bone matrix (DBM) in a rat femoral defect model. A cortical, full-thickness 5-mm defect was created in two femurs of each rat. Six rats were assigned to each of five experimental groups (thus, 12 defects per group). The defects were either untreated or filled with Carbylan-GSX hydrogel or sponges with or without 20% (w/v) DBM. Radiographs were obtained on day 1 and at weeks 2, 4, 6, and 8 postsurgery of each femur. Animals were sacrificed at week 8 postsurgery and each femur was fixed, embedded, sectioned, and processed for Masson's Trichrome staining. The bone defects were measured from radiographs and the fraction of bone healing was calculated. The average fractions of bone healing for each group were statistically different among all groups, and all treatment groups were significantly better than the control group. The Carbylan-GSX sponge with DBM was superior to the sponge without DBM and to the hydrogel with DBM. Histology showed that defects treated with the Carbylan-GSX sponge plus DBM were completely filled with newly generated bone tissue with a thickness comparable to native bone. Carbylan-GSX sponge was an optimal delivery vehicle for human DBM to accelerate bone healing.

Iatrogenic Cervical Deformity

Iatrogenic cervical deformity can develop after anterior or posterior procedures. Careful attention to detail can minimize the likelihood of creating a sagittal or coronal plane deformity. Strategies for the prevention and correction of postoperative cervical deformity are presented.

Intervariability and intravariability of bone morphogenetic proteins in commercially available demineralized bone matrix products

STUDY DESIGN

Enzyme-linked immunosorbent assay was used to detect bone morphogenetic proteins (BMPs) 2, 4, and 7 in 9 commercially available ("off the shelf") demineralized bone matrix (DBM) product formulations using 3 different manufacturer's production lots of each DBM formulation.

OBJECTIVES

To evaluate and compare the quantity of BMPs among several different DBM formulations (inter-product variability), as well as examine the variability of these proteins in different production lots within the same DBM formulation (intra-product variability).

SUMMARY OF BACKGROUND DATA

DBMs are commonly used to augment available bone graft in spinal fusion procedures. Surgeons are presented with an ever-increasing variety of commercially available human DBMs from which to choose. Yet, there is limited information on a specific DBM product's osteoinductive efficacy, potency, and constancy.

METHODS

There were protein extracts from each DBM sample separately dialyzed 4 times against distilled water at 4 degrees C for 48 hours. The amount of BMP-2, BMP-4, and BMP-7 was determined using enzyme-linked immunosorbent assay. RESULTS.: The concentrations of detected BMP-2 and BMP-7 were low for all DBM formulations, only nanograms of BMP were extracted from each gram of DBM (20.2-120.6 ng BMP-2/g DBM product; 54.2-226.8 ng BMP-7/g DBM). The variability of BMP concentrations among different lots of the same DBM formulation, intra-product variability, was higher than the variability of concentrations among different DBM formulations, inter-product variability (coefficient of variation range BMP-2 [16.34% to 76.01%], P < 0.01; BMP-7 [3.71% to 82.08%], P < 0.001). BMP-4 was undetectable.

CONCLUSIONS

The relative quantities of BMPs in DBMs are low, in the order of 1 x 10(-9) g of BMP/g of DBM. There is higher variability in concentration of BMPs among 3 different lots of the same DBM formulation than among different DBM formulations. This variability questions DBM products' reliability and, possibly, efficacy in providing consistent osteoinduction.

Paraspinal muscle vasculature contributes to posterolateral spinal fusion

STUDY DESIGN

Study of posterolateral fusions in a rabbit model.

OBJECTIVES

To characterize the contribution of paraspinal musculature to the healing of posterolateral spinal fusions in a rabbit model.

SUMMARY OF BACKGROUND DATA

Previous studies have demonstrated that successful spinal arthrodesis requires vascular ingrowth from adjacent decorticated bone. In other areas of the body, such as the tibia, vascular ingrowth from the surrounding musculature has also been shown to be important. The role of the surrounding paraspinal musculature in spinal fusions has yet to be assessed.

METHODS

Twenty-five New Zealand white rabbits underwent posterolateral spinal fusion. One side of the animals was treated with autograft alone and served as the control group. On the contralateral side, the autograft was contained within porous or nonporous barrier sheets. Following euthanization, high-resolution radiographs, CT scans, and histologic analyses were performed to assess fusion and characterize vascular ingrowth.

RESULTS

Using histologic evaluation, the fusion rate in the porous group was 90%, in the nonporous group 40%, and in the control group 55%. Vascular ingrowth was evident from the muscle through the porous sheet into the fusion mass.

CONCLUSIONS

These results support our hypothesis that the paraspinal musculature provides important vascular ingrowth into the fusion site. Use of a porous barrier sheet appears to improve fusion by preventing muscle interposition while allowing vascular ingrowth from surrounding muscle.

Influence of three currently used bone replacing materials on the in vitro proliferation of human peripheral blood mononuclear cells

OBJECTIVES

A cell culture system for biocompatibility testing of bone grafting materials is described. We investigated the in vitro viability and proliferative response of peripheral blood mononuclear cells (PBMC) from 10 healthy donors in the presence of three materials currently used for bone grafting: Algipore, Bio-Oss and Bone Source, for immunologic biocompatibility testing.

MATERIAL AND METHODS

PBMC isolated from venous blood from 10 healthy donors were incubated for 4 days with each bone replacing material, in the presence and absence of interleukin-2 (IL-2). After 4 days, H3-thymidine was added for 18 h and the incorporated radioactivity was measured with a beta-plate counter.

RESULTS

Basal PBMC counts were 152.9+/-66.2 counts per minute (c.p.m.) (mean+/-SD), in the presence of 0.4 U IL-2/well 206.5+/-83 c.p.m. were measured. With Algipore and Bio-Oss, which are deproteinized bone replacing materials, the proliferation rate of PBMC with IL-2 was not significantly modified: for Algipore 151+/-51 c.p.m./+IL-2 188.8+/-62 c.p.m., for Bio-Oss 144.5+/-64.9 c.p.m./+IL-2 176.3+/-71.23 c.p.m. For Bone Source 164.2+/-80.4/+IL-2 188.3+/-81 c.p.m. were measured.

CONCLUSION

This in vitro experiment indicates, that the investigated bone replacing materials are not acting as specific antigens/haptens and are not generating increased proliferative responses of human PBMC from healthy donors. Even with IL-2, that induces proliferation of T lymphocytes, which encountered their specific antigen, the proliferation rate of PBMC from healthy donors was not increased after incubation with this bone grafting materials.

Demineralized bone matrix and spinal arthrodesis

Spinal fusion is a gold-standard treatment for many disorders of the spine with autogenous bone graft as the gold-standard source for augmenting fusion. However, the morbidity and limitations of autogenous bone grafting has motivated the search for bone graft alternatives. One such alternative is demineralized bone matrix (DBM). The purpose of this paper is to describe and characterize the properties of DBM in addition to reviewing the results of its use in animal and human studies of spinal fusion. A thorough and critical review of the English-language literature was conducted. DBM is both osteoconductive and osteoinductive. Studies have produced variable results with respect to spinal fusion rates. Various studies have demonstrated inferior, equal, or enhanced fusion rates. Some of the differences in these studies include the animal models used, the manner in which DBM was prepared, and the carrier with which DBM was combined. These differences may account for the dissimilar results. DBM is able to function as a graft extender in the human species.

Surgical treatment of the painful motion segment: matching technology with indications

STUDY DESIGN

Literature review of current bone graft technology and bone graft substitutes used in spinal fusion applications.

OBJECTIVE

We reviewed current bone graft technologies and identified the range of bioactive properties that each possesses, such as osteoconductivity, osteoinductivity, and structural, load-bearing capabilities that can be used to either augment or replace autogenous bone graft in spinal fusions.

SUMMARY OF BACKGROUND DATA

Bioactive materials are used in spinal fusion applications to encourage bone formation across an intervertebral motion segment. To be an effective replacement for autogenous bone grafts, a bioactive material must possess the properties of osteoinduction and osteoconduction.

METHODS

Literature review.

RESULTS

Platelet gel concentrates deliver nonspecific cytokines that influence local cells at the implantation site. Demineralized bone matrix acts as a bone graft enhancer that excludes fibrous tissue of muscle interposition in a fusion mass and is a mildly osteoinductive material. Bone morphogenetic proteins are an integral part of natural bone formation response. They function as differentiation factors that act on mesenchymal stem cells to induce bone formation.

CONCLUSIONS

Patient-derived therapies such as platelet gel concentrates contain cytokines that play a role in bone formation; however, none of them is capable of inducing the entire bone formation cascade. Clinical use of these concentrates could possibly interfere with new bone formation. The use of bone marrow aspiration and concentration techniques has not been convincingly studied in spinal fusions in lower order animal or human clinical studies. Demineralized bone matrix contains small and variable amounts of naturally occurring bone morphogenetic proteins. These products can only function as bone graft extenders. Recombinant bone morphogenetic protein products contain much more highly concentrated and focused amounts of bone morphogenetic proteins, and some have been shown to be clinically effective bone graft replacements.

Initial fusion rates with recombinant human bone morphogenetic protein-2/compression resistant matrix and a hydroxyapatite and tricalcium phosphate/collagen carrier in posterolateral spinal fusion

STUDY DESIGN

Prospective, randomized, unblinded study of iliac crest bone graft (ICBG) versus recombinant human bone morphogenetic protein-2/compression resistant matrix (rhBMP-2/CRM)in a posterolateral instrumented fusion procedure.

OBJECTIVES

Document initial radiographic characteristics, based on computed tomography, with rhBMP-2/CRM for posterolateral fusion at 6 and 12-month intervals.

SUMMARY OF BACKGROUND DATA

As the acceptance of INFUSE bone graft as an ICBG replacement becomes more widespread, surgeons have begun to study applications for rhBMP-2 in posterior spinal fusion. Preclinical studies have examined variables including carrier composition, rhBMP-2 concentration, and rhBMP-2 dose. Pilot studies have been performed with encouraging initial results.

METHODS

Patients with single level lumbar degenerative disease were enrolled in a randomized study of ICBG versus rhBMP-2/CRM in a posterolateral instrumented fusion procedure. Computed tomography scans at 6 and 12 months were graded as demonstrating no fusion (grade 1), partial or limited unilateral fusion (grade 2), partial or limited bilateral fusion (grade 3), solid unilateral fusion (grade 4), or solid bilateral fusion (grade 5).

RESULTS

At our institution, 74 patients (38 rhBMP-2/CRM, 36 ICBG) reached minimum 1-year follow-up and were included in this analysis. Mean fusion grade (scale1-5) at 6 months after surgery was 4.35 in the rhBMP-2/CRM group versus 3.09 in the ICBG group (P < 0.0001). At 1 year after surgery mean fusion grade was 4.62 in the rhBMP-2/CRM group versus 3.77 in the ICBG group (P < 0.0023).

CONCLUSIONS

These early results are encouraging and suggest a more rapid incorporation and development of the fusion mass with rhBMP-2/CRM than iliac crest autograft in a single level posterior instrumented fusion.

Use of rhBMP-2 in combination with structural cortical allografts: clinical and radiographic outcomes in anterior lumbar spinal surgery

BACKGROUND

Recombinant human bone morphogenetic protein-2 soaked into an absorbable collagen sponge (rhBMP-2/ACS) has been shown in a nonhuman primate study and in a pilot study in humans to promote new bone formation and incorporation of an allograft device when implanted in patients undergoing anterior lumbar interbody arthrodesis. However, a larger series with longer follow-up is needed to demonstrate its superiority to autogenous iliac crest bone graft.

METHODS

Between 1998 and 2001, a two-part, prospective, randomized, multicenter study of 131 patients was conducted to determine the safety and efficacy of the use of rhBMP-2/ACS as a replacement for autogenous iliac crest bone graft in anterior lumbar spinal arthrodesis with threaded cortical allograft dowels. Patients were randomly assigned to a study group that received rhBMP-2/ACS or to a control group that received autograft. The clinical and radiographic outcomes were determined with use of well-established instruments and radiographic assessments.

RESULTS

The patients in the study group had significantly better outcomes than the control group with regard to the average length of surgery (p < 0.001), blood loss (p < 0.001), and hospital stay (p = 0.020). Fusion rates were significantly better in the study group (p < 0.001). The average Oswestry Disability Index scores, Short-Form-36 physical component summary scores, and low-back and leg-pain scores were significantly better in the study group (p < 0.05).

CONCLUSIONS

In patients undergoing anterior lumbar interbody arthrodesis with threaded allograft cortical bone dowels, rhBMP-2/ACS was an effective replacement for autogenous bone graft and eliminated the morbidity associated with graft harvesting.

Mechanisms of action of demineralized bone matrix in the repair of cortical bone defects

Demineralized bone matrix commonly is used to enhance and to facilitate bone grafting after skeletal injury or disease; however, the biologic bases for its bone-inducing abilities remain obscure. We have taken advantage of a mouse model of cortical bone defect healing to elucidate its mechanisms of action in vivo. Demineralized bone matrix combined with hyaluronan improved skeletal healing by inducing early deposition of an osteoid matrix. Demineralized bone matrix combined with hyaluronan might accelerate bone formation because it serves as a scaffold on which osteoprogenitor cells attach. We tested this possibility by comparing demineralized bone matrix combined with hyaluronan with heat-inactivated demineralized bone matrix combined with hyaluronan and found that the intact material was superior in terms of its ability to stimulate new bone formation. We also compared the bone inducing capacity of demineralized bone matrix combined with hyaluronan with a synthetic collagen sponge and found that not only the synthetic collagen scaffold delayed bone healing but also impaired bony bridging at later stages of repair. Another important property of demineralized bone matrix combined with hyaluronan was its ability to become actively degraded by osteoclasts during healing. Therefore, demineralized bone matrix combined with hyaluronan may not only attract osteoblasts and stimulate their differentiation, but also induce bone matrix resorption, which is a critically important regulator of bone formation and mineralization.

The effectiveness of rhBMP-2 in replacing autograft: an integrated analysis of three human spine studies

In anterior lumbar spinal fusion, patients treated with rhBMP-2 on a collagen sponge carrier had statistically superior outcomes compared to patients treated with autogenous bone graft. A collagen sponge carrier should replace autogenous bone graft for this patient population.

Lumbar stenosis: a personal record

✓ Although its management continues to evolve, lumbar stenosis remains a common societal problem. The present article is based on an invited lecture at the 2004 Annual Meeting of the Congress of Neurological Surgeons/American Association of Neurological Surgeons Joint Section on Disorders of the Spine and Peripheral Nerves. In it the authors provide a historical overview of lumbar stenosis and describe how the senior author's treatment of this condition has evolved over the past four decades. Within each era of treatment, the reasons for modification of treatment methods and relevant outcome measures are outlined. Additionally, specific subsets of patients with lumbar stenosis are also discussed to emphasize unique characteristics that affect treatment strategies. The authors' present technique for management of lumbar stenosis is also illustrated.

Disc chondrocyte transplantation in a canine model: a treatment for degenerated or damaged intervertebral disc

STUDY DESIGN

Disc degeneration and osteoarthritis are diseases of the matrix. Chondrocytes that have been removed from damaged cartilaginous tissues maintain a capacity to proliferate, produce, and secrete matrix components, and respond to physical stimuli such as dynamic loading. A dog model was used to investigate the hypothesis that autologous disc chondrocytes can be used to repair damaged intervertebral disc.

OBJECTIVES

Given the capacity for the cells in vitro to produce matrix molecules that would be appropriate for disc chondrocytes, the focus of the experiment was to investigate whether the cells would continue to sustain metabolic function after transplantation.

SUMMARY OF THE BACKGROUND DATA

No evidence for long-term integration exists for cell transplantation in species other than rats and rabbits. Furthermore, no controlled studies of 1-year duration have been published.

MATERIALS AND METHODS

Disc chondrocytes were harvested and expanded in culture under controlled and defined conditions, returned to the same animals from which they had been sampled (autologous transplantation) via percutaneous delivery. The animals were analyzed at specific times after transplantation by several methods to examine whether disc chondrocytes integrated with the surrounding tissue, produced the appropriate intervertebral disc extracellular matrix, and might provide a formative solution to disc repair.

RESULTS

In the context of degenerative changes in an injury model: (1) autologous disc chondrocytes were expanded in culture and returned to the disc by a minimally invasive procedure after 12 weeks; (2) disc chondrocytes remained viable after transplantation as shown by Bromodeoxyuridine incorporation and maintained a capacity for proliferation after transplantation as depicted by histology; (3) transplanted disc chondrocytes produced an extracellular matrix that displayed composition similar to normal intervertebral disc tissue. Positive evidence of proteoglycan content was supported by accepted histochemical staining techniques such as Safranin O-Fast Green; (4) both type II and type I collagens were demonstrated in the regenerated intervertebral disc matrix by immunohistochemistry after chondrocyte transplantation; and (5) when the disc heights were analyzed for variance according to treatment, a statistically significantcorrelation between transplanting cells and retention of disc height was achieved.

CONCLUSIONS

Autologous chondrocyte transplantation is technically feasible and biologically relevant to repairing disc damage and retarding disc degeneration.

Do autologous growth factors enhance transforaminal lumbar interbody fusion?

Pseudarthrosis remains a significant problem in spinal fusion. The objective of our study was to investigate the effects of autologous growth factors (AGF) in instrumented transforaminal lumbar interbody spinal fusion (TLIF). A prospective review was carried out of 23 patients who underwent TLIF with application of AGF, with a minimum 2-year follow-up. Comparison with our historical cohort (without AGF application) was performed. Mean age at surgery was 44.3 years in the AGF treatment group. Twelve had a positive smoking history. Fourteen had undergone previous spinal surgeries. Thirteen received one-level fusions and ten received two-level fusions. The radiographic results showed a fusion rate of 100% in one-level fusions and 90% in two-level fusions. There was no significant difference in pseudarthrosis rates between the AGF treatment group and historical cohort. Excluding the cases with pseudarthrosis, there was faster bony healing in patients who had been treated with AGF application. This study indicates that although AGF may demonstrate faster fusions, it does not result in an overall increase in spinal fusion rates. Further studies are needed before AGF can routinely be used as an adjunct in spinal fusion.

Is INFUSE bone graft superior to autograft bone? An integrated analysis of clinical trials using the LT-CAGE lumbar tapered fusion device

Multicenter human clinical studies of patients undergoing anterior lumbar fusion have been conducted using recombinant bone morphogenetic protein or rhBMP-2 on an absorbable collagen sponge, marketed as INFUSE Bone Graft, or autograft implanted in the LT-CAGE Lumbar Tapered Fusion device. An integrated analysis of multiple clinical studies was performed using an analysis of covariance to adjust for preoperative variables in a total of 679 patients. Of these patients, 277 had their cages implanted with rhBMP-2 on an absorbable collagen sponge and 402 received autograft transferred from the iliac crest. The patients treated with rhBMP-2 had statistically superior outcomes with regard to length of surgery, blood loss, hospital stay, reoperation rate, median time to return to work, and fusion rates at 6, 12, and 24 months. Oswestry Disability Index scores and the Physical Component Scores and Pain Index of the SF-36 scale at 3, 6, 12, and 24 months showed statistically superior outcomes in the rhBMP-2 group.

Use of osteogenic protein–1 in spinal fusion: literature review and preliminary results in a prospective series of high-risk cases

Object

The safety and effectiveness of osteogenic protein (OP)–1 putty (recombinant human bone morphogenetic protein–7) in promoting fusion in complex spinal cases was studied in nine cases.

Methods

The authors prospectively evaluated nine patients requiring spinal fusion in whom there were medical risk factors that would inhibit osseous fusion. Intraoperatively the OP-1 putty mixed with autologous bone was placed at the fusion site. Outcome measurement instruments were used to provide information on patient demographics, comorbidities, and pain. The Short Form (SF)–36 questionnaire and Oswestry Disability Index (ODI) were administered pre- and postoperatively. All patients underwent routine radiography of the surgery site during follow-up examination.

The age of the five women and four men ranged from 21 to 74 years (mean height 1.6 m, mean weight 76.7 kg). Risk factors included mucopolysaccharide syndrome, adrenal insufficiency, rheumatoid arthritis with chronic corticosteroid use, morbid obesity, and heavy smoking. Surgery, which consisted of five cervical and four lumbar procedures, including intradural surgery in three patients, was uneventful in all cases without perioperative complication. The follow-up period ranged from 1 to 15 months (mean 5.22 months). The ODI score changed from severe disability (mean 46.89) pre-operatively to minimal and moderate disability (mean 34.56) postoperatively. The SF-36 survey showed overall improved mental and physical health scores. Fusion was present in all patients with greater than 3 months follow up.

Conclusions

The OP-1 putty appears to be safe and effective in promoting spinal arthrodesis in patients in whom adverse medical risk factors exist.