In-vivo and in-vitro histological evaluation of two commercially available acellular dermal matrices.

PURPOSE: Post-herniation abdominal wall repair can be performed with synthetic or biologic meshes. Synthetics have been associated with complications, so biologics are promising alternatives. The methods used to decellularize biological matrices may affect the extracellular components. This study evaluated the post-implantation biological response of two allogenic acellular dermal matrices (ADMs) in a hernia model. METHODS: Testing was conducted with two ADMs from different manufacturers: RTI Biologics (ADM-R) and LifeCell (ADM-L). Samples were evaluated for collagen IV, glycosaminoglycans (GAGs), and elastin before implantation. Samples were also used to repair bilateral full-thickness defects in rat abdominal walls. Pathologist evaluations included explant dimensions, inflammation, neovascularization, mature implant tissue, fibrosis, encapsulation, necrosis, mineralization, adhesions, granulomas, and hemorrhages at four and eight weeks post-implantation. RESULTS: GAG distribution in ADM-R samples was more consistent with native dermis than that in ADM-L samples. Collagen IV was visible in ADM-R, but not in ADM-L. The four-week ADM-R explants showed primarily lymphocytic infiltrates, and less inflammation at eight weeks. The four-week ADM-L explants showed primarily lymphocytic infiltrates, and sustained inflammation at eight weeks. Fibroplasia at four and eight weeks was higher in ADM-L than in ADM-R. Encapsulation, mature connective tissue, and vascular profile scores were comparable between groups. Picrosirius red image analysis showed no significant differences between groups. CONCLUSIONS: The post-processing matrix characterization and in-vivo response showed notable differences in these ADMs, despite similar allogenic origin. Future investigations into the different matrix composition with regard to fibrosis and inflammation are warranted.

Differential effects of bone graft substitutes on regeneration of bone marrow.

BACKGROUND: This study used a rat tibial marrow ablation model to test the hypothesis that bone remodeling within the medullary canal varies with bone graft materials of different chemical compositions and structural properties, impacting marrow cavity restoration. Bone graft materials were selected based on their relative resorption or degradation in vivo and their osteogenic properties. METHODS: Following ablation of the right tibial marrow in male Sabra-strain rats, materials were implanted in the proximal marrow cavity: poly-D,L-lactide-co-glycolide 75 : 25 (PLGA); coralline-hydroxyapatite (HA), calcium-sulfate (CaSO4), collagen-HA-tricalcium phosphate granules, anorganic bovine bone mineral, demineralized bone matrix (DBM), 45S5 Bioglass (BG), PLGA with BG 50 : 50, PLGA : BG 80 : 20, and PLGA and PLGA:BG 50 : 50 plus bone marrow (BM). Control tibias were ablated but received no implants. At 2 (endosteal bone healing), 4 (marrow cavity remodeling) and 8 weeks (marrow restoration), six to eight animals per group were euthanized and tibias processed for histomorphometry of proximal and distal medullary canals. RESULTS: Control tibias showed primary bone in proximal and distal medullary canals at 2 weeks, with trabeculae surrounded by cellular marrow. At 4 and 8 weeks, control trabeculae were thinned and marrow had more fat cells. In the treated tibias, trabecular bone volume (TBV) varied with time and was material specific. Most implants supported comparable TBV at 2 weeks. Sites with CaSO4 or DBM exhibited decreased TBV with time whereas trabecular bone was retained in proximal tibias containing other materials, closely juxtaposed to the implants. TBV did not always correlate directly with implant volume, but changes in BM volume were correlated inversely with TBV. Addition of BM increased marrow restoration in sites containing PLGA; however, BM reduced restoration of marrow when added to PLGA : BG. Although the presence of implants in the proximal tibia resulted in retention of trabecular bone, there was a time-dependent reduction in TBV in distal canals; the rate and extent of the distal TBV reduction were implant dependent. CONCLUSIONS: Thus, although many materials can support bone formation in the marrow cavity, bone quality, quantity, and physical relationship to the implant, and its rate of resorption differ in a material-dependent manner, resulting in differences in the restoration of marrow. CLINICAL RELEVANCE: Bone graft materials should be selected not only for their ability to support new bone formation but also for their impact on the remodeling phase of bone healing.

Evaluation of a bioglass-coated Al2O3 total hip prosthesis in sheep.

A bioglass-coated fully dense alumina total hip was evaluated in sheep without using polymer bone "cement." After 3 months following surgery, both the acetabular cup and femoral stem component were firmly attached to bone. Histologic and radiographic analysis of the bone-implant interface showed regions of woven and even lamellar bone formation where high load transmission occurred. In regions of low loading or poor fit, a pseudosynovial fibrous lining was present.