Purpose

Platelet-derived growth factor-BB (PDGF-BB) is a well characterized wound healing protein known to be chemotactic and mitogenic for cells of mesenchymal origin, including osteoblasts and chondrocytes. Biocompatible scaffolds, combined with growth factors such as PDGF-BB, have potential to stimulate regeneration and repair of osseous and cartilaginous tissues. The purpose of this study was to determine the efficacy and safety of recombinant human PDGF-BB (rhPDGF-BB) combined with a collagen implant to augment healing of osteochondral defects.

Porous collagen-glycosaminoglycan (Col/GAG) scaffolds have previously been used clinically as regeneration templates for peripheral nerves and skin^[1]. For defects involving even minimal load-bearing applications however, these scaffolds do not possess the required stiffness. Calcium phosphates (CaPs) are often used as bone-graft substitutes due to their biocompatibility and direct bone-bonding ability. While CaPs have sufficient stiffness for bone-defect applications, unlike Col/GAG they lack elasticity and are very brittle. Combining these two materials produces a composite with enhanced material properties and chemical similarity to natural bone. The addition of CaP nanocrystallites into the Col/GAG matrix produces a 3-dimensional structure that maintains its structural integrity even when wet. In this study, the in vivo performance of mineralised Col/GAG composites was evaluated by implantation into a six-week ovine bone-defect model.

Four different materials were implanted; Col/GAG alone, Col/GAG with octacalcium phosphate, Col/GAG with hydroxyapatite and Col/GAG with brushite. Implants with a diameter of 9mm and length of 9mm, were placed bilaterally into the distal femoral condyle of the hind legs of thirteen sheep. This site was selected due to the large volume of load-bearing cancellous bone. Cancellous autograft was harvested from the tibial tuberosity and placed in the defect sites of two sheep as a positive control.

All animals were sacrificed after 6 weeks and tissue containing the implants was prepared for histological evaluation. Image analysis of Von Kossa stained sections showed that all mineralised Col/GAG implants had significantly more bone in the implant site than unmineralised Col/GAG but were not significantly different between CaPs. Interestingly, new bone formation often followed the structure of the porous material struts which acted as a template. The defect containing the autograft contained the greatest amount of new bone.

Introduction

The purpose of this study was to investigate whether combining PRP or concentrated bone marrow aspirate (CBMA) with a biphasic collagen/glycosaminoglycan (CG) scaffold would improve the outcome of the treatment of full thickness osteochondral defects in sheep.

Introduction: Current treatment options for small, contained articular cartilage defects include microfracture, osteochondral autograft plugs or newer synthetic plugs. Chondromimetic is a novel biphasic biological scaffold composed of collagen and glycosaminoglycan. The addition of brushite provides the scaffold with a regionally specific component mimicking both phases of the osteochondral unit. The aim of this study was to show the efficacy of Chondromimetic in repairing a surgically created osteochondral defect in a caprine model.

Methods: Osteochondral defects were made in the lateral trochlear sulcus (LTS) and medial femoral condyle (MFC) of nine goats. Chondromimetic scaffolds (6x6mm) were inserted into each defect (n=6), while three controls had defects left empty (n=3). All animals were sacrificed at 26 weeks postoperatively. Macroscopic evaluations and quantitative stiffness properties were assessed. Histological sections were taken at approximately the centre of the defect, stained with Safrinin O/Fast Green and scored using a validated quantitative assessment tool.

Results: Macroscopically, the repair tissue scored higher in the MFC and LTS (p< 0.05) compared to controls. In all defects, the mechanical stiffness was found to be within one standard deviation of native cartilage, except that of the LTS controls. Histologically, the predominant tissue in the cartilage layer was deemed to be hyaline-like in three of six MFC defects, and five of six LTS defects according to the modified Sellers score. This was compared to one in three and zero of three in the MFC and LTS controls respectively.

Discussion: These results represent the early findings from an ongoing in-vivo study in which a further group of animals will be sacrificed at one year. At six months, the histology and mechanical properties are encouraging and should continue to improve with time. These results show that Chondromimetic may represent an acceptable alternative to marrow stimulation in the treatment of osteochondral defects.

Introduction: Current treatment options for small, contained articular cartilage defects include microfracture, osteochondral autograft plugs or newer synthetic plugs. Chondromimetic is a novel biphasic biological scaffold composed of collagen and glycosaminoglycan. The addition of brushite provides the scaffold with a regionally specific component enabling the scaffold to mimic both phases of the osteochondral unit.

The aim of this study was to show the efficacy of Chondromimetic in repairing a surgically created osteochondral defect in a caprine model.

Methods: Osteochondral defects were made in the lateral trochlear sulcus (LTS) and medial femoral condyle (MFC) of nine goats. Chondromimetic scaffolds (6x6mm) were inserted into each defect (n=6), while three controls had defects left empty (n=3). All animals were sacrificed at 26 weeks postoperatively. Macroscopic evaluations and quantitative stiffness properties were assessed. Histological sections were taken at approximately the centre of the defect, stained with Safrinin O/Fast Green and scored using a validated quantitative assessment tool.

Results: Macroscopically, the repair tissue scored higher in the filled MFC and LTS (p< 0.05) compared to controls. In all defects, the mechanical stiffness was found to be within one standard deviation of native cartilage, except the LTS controls. Histologically, the predominant tissue in the cartilage layer was hyaline-like in three of six filled MFC defects, and five of six filled LTS defects according to the modified Sellers score. This was compared to one in three and zero of three in the MFC and LTS controls respectively.

Discussion: These results represent the early findings from an ongoing in-vivo study in which a further group of animals will be sacrificed at one year. At six months, the histology and mechanical properties are encouraging and should continue to improve with time. These results show that Chondromimetic may represent an acceptable alternative to marrow stimulation in the treatment of osteochondral defects.