Use of a resorbable sheet in iliac crest reconstruction in a sheep model

Evaluation of perforated demineralized dentin scaffold on bone regeneration in critical-size sheep iliac defects

OBJECTIVES

Regenerating critical-size bone injury is a major problem that continues to inspire the design of new graft materials. Therefore, tissue engineering has become a novel approach for targeting bone regeneration applications. Human teeth are a rich source of stem cells, matrix, trace metal ions, and growth factors. A vital tooth-derived demineralized dentin matrix is acid-insoluble and composed of cross-linked collagen with growth factors. In this study, we recycled human non-functional tooth into a unique geometric dentin scaffold, entitled perforated root-demineralized dentin matrix (PR-DDM). The aim of this study was to evaluate the feasibility of PR-DDM as the scaffold for regenerating bone in critical-size iliac defects.

MATERIAL AND METHODS

Artificial macro-pores (1 mm in diameter) were added to human vital wisdom tooth after removing the enamel and pulp portions. The modified tooth was demineralized in 0.34 N HNO₃ for 30 min and is referred to as PR-DDM scaffold. Critical-size defect (10 mm × 15 mm × 9 mm Ø) was created in the iliac crest of six adult sheep. The in vivo bone regeneration by the scaffold was evaluated by micro-CT, 3D micro-CT, and histological examination at 2 and 4 months post-implantation.

RESULTS

PR-DDM exhibited better bone ingrowth, especially in the artificial macro-pores. The results of micro-CT and 3D micro-CT revealed good union between scaffold and native bone. New bone formation was observed in almost all portions of PR-DDM. Higher bone volume inside the scaffold was detected at 4 months compared with 2 months. New bone ingrowth was ankylosed with PR-DDM, and both osteoinduction and osteoconduction capability of PR-DDM were confirmed histologically. The ratio of new bone formation was higher at 4 months compared with 2 months by histomorphometric analysis.

CONCLUSIONS

Altogether, these results demonstrated that the human tooth-derived graft material with a unique geometric structure, PR-DDM, contributed to active bone ingrowth in critical-size bone defects. This novel scaffold may have great utility in the near-future clinical application.

Reconstruction of critical-size mandibular defects in immunoincompetent rats with human adipose-derived stromal cells

In patients with bony defects, autologous bone grafts are the "gold standard" for reconstruction. In children, autologous bone harvesting is limited but tissue engineering offers an alternative. Next to bone marrow, adipose tissue is a source of mesenchymal stromal cells, and adipose-derived stromal cells (ADSC) can differentiate into osteocytes. The aim of this study was to evaluate the efficacy of bioactive implants (ADSC in fibrin glue) for repair of critical-size mandibular defects in athymic rats. Human adult ADSC embedded in fibrin glue were implanted into a critical-size defect in the rat mandible and their efficacy was compared to those of protected bone healing (pbh), autologous bone graft, and an empty defect. The newly formed bone was quantified using high-resolution flat-panel volumetric CT (fpvCT) during different observation times. After eight weeks, the specimens were assessed histologically and by micro-computed tomography (μ-CT). The radiographic examination demonstrated a significantly higher level of ossified defect area in the ADSC side compared with the pbh side. The autologous bone graft side showed significantly enhanced bone formation compared to the empty defect. The histological findings in the specimens with ADSC showed bony bridging of the defect. ADSC were capable of defect reconstruction under our experimental conditions.

Autograft containment in posterolateral spine fusion

BACKGROUND CONTEXT

Pseudoarthrosis rates in lumbar intertransverse fusion remain high. Compression and displacement of the developing fusion mass by the paraspinal musculature may be a contributory factor. Biocontainment devices have been clinically used in the skull and mandible to guide bone regeneration. The role of a mechanical device in containing graft material in the developing posterolateral lumbar spine fusion is unclear.

PURPOSE

To determine the benefits of using a bioabsorbable graft-containment device for lumbar intertransverse fusion, and to evaluate the biocompatibility of this implant by histological analysis of the host tissue reaction.

STUDY DESIGN

A rabbit intertransverse spine fusion model was used to evaluate a bioabsorbable graft-containment implant. Study and control groups were compared with regard to the rate, volume, and quality of fusion, as well as host tissue reaction to the graft and implant.

METHODS

Fourteen adult male New Zealand White rabbits underwent bilateral posterolateral intertransverse spine arthrodesis at L3-L4. The control group (n=7) received autograft alone, and the study group received autografts placed in open meshed hemicylinders fashioned from LactoSorb sheets (LactoSorb; Biomet Orthopedics Inc., Warsaw, IN). Spines were harvested at 6 weeks and imaged. Radiographs and computed tomography (CT) images were used to calculate the rate, area, and volume of fusion mass. Sections were fixed and stained with hematoxylin-eosin and Mallory trichrome for histological analysis of fusion and host tissue response. The Mann-Whitney nonparametric statistical test was used for the radiographic and CT qualitative assessments. The CT volume quantitation was analyzed using the Student t test. A p value of <.05 was used to assign statistical significance.

RESULTS

The fusion rates on radiographs and CT imaging did not show a significant difference (p>.05) between the biocontainment and control groups. The volume of fusion revealed a significant increase with biocontainment (mean+/-standard error; total left+right fusion sides=2.88+/-0.30 cc) compared with controls (2.12+/-0.15 cc) (p<.05). Histology revealed no difference in the maturity or the quality of the fusion mass between the two groups. Inflammatory response around the developing fusion mass and muscle necrosis were slightly increased in the study group. The LactoSorb biocontainment material led to variable inflammatory reaction, with some areas showing little or no response and other showing an inflammatory response with fibrous connective tissue, lymphocyte infiltration, and focal foreign body giant cell reaction.

CONCLUSIONS

The incidence of fusion was similar with or without a containment device for onlay bone graft. A significant increase in the volume of the fusion suggests that a biocontainment device does play a role in protecting the developing fusion mass from the mechanical effects of the paraspinal musculature. The clinical use of this device cannot be justified at this time, and further studies will determine whether this increase in fusion volume will translate into a better incidence and volume of fusion in primate and human models.

Absorbable self-reinforced polylactide (SR-PLLA) rods vs rigid rods (K-wire) in spinal fusion: an experimental study in rabbits

Several clinical and experimental reports have evaluated the spinal application of bioabsorbable material for plating the anterior lumbar and cervical spine, and in anterior and posterior lumbar interbody spinal fusion. Nevertheless, the use of these materials in posterolateral interlaminar fusion has yet to be elucidated in the literature. The effects of bioabsorbable self-reinforced polylactide rod (SR-PLLA) implantation, rigid fixation (K-wire) and non-implantation with posterior interlaminar fusion were compared using a rabbit model. Twenty-four mature domestic rabbits were divided into three groups. Eight received implantation with SR-PLLA, eight with K-wire, and eight were fused without instrumentation. The animals were killed at 12 weeks and evaluated by posteroanterior radiography, manual palpation and histological examination for the presence of fusion. Successful fusion was achieved in all of the animals in both implanted groups (SR-PLLA and K-wire), whereas solid fusion was not detected in any of the specimens in the non-implanted group. Computed tomography (CT) scans were used to detect fusion mass volume. The fusion mass in the SR-PLLA implanted group had a mean volume of 1,196 mm3 +/- 167 mm3 vs 1,061 mm3 +/- 181 mm3 for the K-wire implanted group (not significant) and 711 mm3 +/- 407 mm3 (p<0.05) for the non-implanted group. The results of this study suggest that the stabilization properties of both SR-PLLA rods and K-wire seem to be sufficient for spinal fusion, but using SR-PLLA is especially advantageous, since they do not require a removal operation and do not interfere with magnetic resonance imaging (MRI).

The use of bioabsorbable implants in the spine

BACKGROUND CONTEXT

Bioabsorbable implants are commonplace in sports medicine surgeries, especially in shoulder and knee ligamentous reconstruction. Their use is now expanding to the realm of spinal reconstructive surgery. Newer polymers offer reduced incidence of the side effects of aseptic sterile sinus formation and have appropriate resorption time parameters for spine use. These new bioabsorbable materials confer initial and intermediate-term stability that is adequate for stable bony healing in various applications. The majority of human clinical applications in the spine that have been documented involve bone graft harvest site reconstruction, posterior spinal graft containment, anterior interbody reconstruction and anterior cervical and lumbar spine tension band plating.

PURPOSE

The purpose of this review article is to highlight the indications and outcomes of the use of bioabsorbable implants in specific spinal applications.

STUDY DESIGN

A comprehensive literature review of the English and non-English literature on bioabsorbable implant technology.

METHODS

A comprehensive literature review was performed to gather basic science, animal and human data on the use of bioabsorbable implants in spinal surgery.

RESULTS

Bioabsorbable implants have demonstrated strength and resorption characteristics commensurate with the physiologic and biomechanical requirements of the human spinal axis. Histologic sampling has demonstrated successful time-patterned resorption accompanied by bony replacement and remodeling of intervertebral cage devices in the animal model.

CONCLUSION

Bioresorbable compounds appear to have a role in specific spinal reconstructive procedures. Their radiolucent nature improves image assessment of fusion healing, and their time-engineered resorption characteristics allow controlled dynamization in interbody and plate applications. Their widespread use and acceptance may increase dramatically as further research and clinical studies report on their safety and efficacy.