Advances in Tissue Engineering Techniques for Articular Cartilage Repair

Abstract

The limited repair potential of human articular cartilage contributes to development of debilitating osteoarthritis and remains a great clinical challenge. This has led to evolution of cartilage treatment strategies from palliative to either reconstructive or reparative methods in an attempt to delay or "bridge the gap" to joint replacement. Further development of tissue engineering-based cartilage repair methods have been pursued to provide a more functional biological tissue. Currently, tissue engineering of articular cartilage has three cornerstones; a cell population capable of proliferation and differentiation into mature chondrocytes, a scaffold that can host these cells, provide a suitable environment for cellular functioning and serve as a sustained-release delivery vehicle of chondrogenic growth factors and thirdly, signaling molecules and growth factors that stimulate the cellular response and the production of a hyaline extracellular matrix (ECM). The aim of this review is to summarize advances in each of these three fields of tissue engineering with specific relevance to surgical techniques and technical notes.

Figure 1. Autologous Chondrocyte Implantation (ACI)

Collagen membranes: a. Two mini anchors (dotted arrows) with absorbable sutures are placed at opposing sides of the defect and the sutures passed through the collagen membrane. The membrane is guided down the sutures through a cannula (blue tube) to the defect. b. The membrane is placed, fibrin glue is applied to the base and sutures are tied over. Hyaluronan grafts: c. Delivery device with sharp edge is placed on the cell-loaded hyaluronic acid patch embedding it into the tip. d. The delivery device is introduced to overlie the defect and the graft is pushed out and positioned within the defect. e. Patches overlapped to create a complete coverage of large defects in an overlapping “mosaic” pattern. Polymer fleece: f. The 4 corners of the defect are drilled with guide wires through the cannula in an inside-out technique. The scaffold is armed at its corners with resorbable sutures and mounted on the corresponding guide wires. g. The threads are pulled into the joint by the guide wires leading the implant through the cannula into the joint.

Figure 2. Minced Articular Cartilage

a. The harvester-disperser instrument with PCL/PGA scaffold attached to the bottom. b. Even distribution of the minced cartilage is followed by fibrin glue injection to stabilize the fragments on the scaffold. c. Minced cartilage implant is placed into the defect and fixed with PDS U-shaped staples.

Figure 3. Sandwich technique

a. An osteochondral defect extending deep into the subchondral bone b. Bone grafting to the level of the subchondral bone and placing a periosteal patch or sealant in level with the bone surface. c. A second periosteal patch or sealant layer is placed at the level of the cartilage surface with the cell/scaffold “sandwiched” in between the two layers.

Figure 4. Autologous Matrix-Induces Chondrogenesis (AMIC)

a. The microfractured defect is covered with a collagen membrane for 5 minutes. b. After bone marrow saturation, the matrix is trimmed and fixed with fibrin glue

Figure 5. Chitosan/Blood Clot

a. The cartilage defect is microfractured. b. The delivery needle is directed perpendicular and central to the lesion and the BST-CarGel/blood mixture is delivered in a drop-wise fashion into each microfracture hole c. and then onto the surrounding defect taking care not to “overfill”.

Figure 6. Bone Marrow Aspirate Concentrate (BMAC)

a. In the operating room, the mononuclear layer of the bone marrow (BMAC) is separated (middle zone) and implanted on a combined mixture of platelet gel and collagen powder or hyaluronic acid membrane. b. The cell/scaffold implant is inserted through the arthroscopic portal through a cannula with a sliding positioner or on a guide wire drilled through the centre of the defect. c. The implant is positioned with the help of a probe and adheres due to its PRP content. An additional layer of PRP is then applied to the surface for further fixation.

Figure 7. Osteochondral plug (TruFit)

a. The cylindrical osteochondral plug (brown) is preloaded on a delivery device with an outer sleeve (green cylinder) and a measuring tamp (grey). The assembly is inserted perpendicular to the lesion until the measuring tamp contacts the base of the defect. b. The outer sleeve is slid over the tamp (blue straight arrow) until it is flush against the cartilage surface. This pushes the excess portion of the osteochondral plug out of the sleeve which is subsequently cut (dashed line). c. The sleeve is reversed and the implant is inserted into the defect by manually advancing the tamp within the delivery device.