I.Bone cement filling technique
The bone cement filling method is suitable for patients with smaller AORI type I bone defects and less active activities.
Simple bone cement technology technically requires thorough cleaning of the bone defect, and bone cement fills the bone defect during the dough stage, so that it can be stuffed into the gaps in the corners of the defect as much as possible, thereby achieving a tight fit with the host bone interface.
The specific method of Bone Cement + Screw technology is to thoroughly clean the bone defect, then fix the screw on the host bone, and be careful not to let the screw cap exceed the bone surface of the joint platform after osteotomy; then mix the bone cement, fill the bone defect in the dough stage, and wrap the screw. Ritter MA et al. used this method to reconstruct the tibial plateau bone defect, and the defect thickness reached 9mm, and there was no loosening 3 years after the operation. Bone cement filling technology removes less bone, and then uses conventional prosthesis revision, thereby reducing the treatment costs due to the use of revision prostheses, which has certain practical value.
The specific method of bone cement + screw technology is to thoroughly clean the bone defect, fix the screw on the host bone, and pay attention that the screw cap should not exceed the bone surface of the joint platform after osteotomy; then mix the bone cement, fill the bone defect in the dough stage, and wrap the screw. Ritter MA et al. used this method to reconstruct the tibial plateau bone defect, and the defect thickness reached 9mm, and there was no loosening 3 years after surgery. Bone cement filling technology removes less bone, and then uses conventional prosthesis revision, thereby reducing the treatment cost due to the use of revision prosthesis, which has certain practical value (Figure I-1).
Figure I-1 Bone cement filling and screw reinforcement
II. Bone grafting techniques
Compression bone grafting can be used to repair inclusive or non-inclusive bone defects in knee revision surgery. It is mainly suitable for the reconstruction of AROI type I to III bone defects. In revision surgery, since the scope and degree of bone defects are generally severe, the amount of autologous bone obtained is small and mostly sclerotic bone when the prosthesis and bone cement are removed during surgery to preserve bone mass. Therefore, granular allogeneic bone is often used for compression bone grafting during revision surgery.
The advantages of compression bone grafting are: retaining the bone mass of the host bone; repairing large simple or complex bone defects.
The disadvantages of this technology are: the operation is time-consuming; the reconstruction technology is demanding (especially when using large MESH cages); there is a potential for disease transmission.
Simple compression bone grafting: Simple compression bone grafting is often used for inclusive bone defects. The difference between compression bone grafting and structural bone grafting is that the granular bone graft material made by compression bone grafting can be quickly and completely revascularized.
Mesh metal cage + compression bone grafting: Non-inclusive bone defects usually require reconstruction using mesh metal cages to implant cancellous bone. Reconstruction of the femur is usually more difficult than reconstruction of the tibia. X-rays show that bone integration and bone shaping of the graft material are gradually completed (Figure II-1-1, Figure II-1-2).
Figure II-1-1 Mesh cage internal compression bone grafting to repair tibial bone defect. A Intraoperative; B Postoperative X-ray
Figure II-1-2 Repair of femoral and tibia bone defects with titanium mesh internal compression bone grafting. A Intraoperative; B Postoperative X-ray
During revision knee arthroplasty, allogeneic structural bone is mainly used to reconstruct AORI type II or III bone defects. In addition to having superb surgical skills and rich experience in complex knee replacement, the surgeon should also make careful and detailed preoperative plans. Structural bone grafting can be used to repair cortical bone defects and increase bone mass.
Advantages of this technology include:It can be made into any size and shape to adapt to bone defects of different geometric shapes; it has a good supporting effect on revision prostheses; and long-term biological integration can be achieved between allogeneic bone and host bone.
Disadvantages include: prolonged operation time when cutting allogeneic bone; limited sources of allogeneic bone; risk of nonunion and delayed union due to factors such as bone resorption and fatigue fracture before the bone integration process is completed; problems with absorption and infection of transplanted materials; potential for disease transmission; and insufficient initial stability of allogeneic bone. Allogeneic structural bone is harvested from the distal femur, proximal tibia, or femoral head. If the transplant material is large, complete revascularization usually does not occur. Allogeneic femoral heads can be used to repair femoral condyle and tibial plateau bone defects, mainly for the repair of huge cavity-type bone defects, and are fixed by press-fitting after trimming and shaping. Early clinical results of using allogeneic structural bone to repair bone defects showed a high healing rate of transplanted bone (Figure II-1-3, Figure II-1-4).
Figure II-1-3 Repair of femoral bone defect with allogeneic femoral head structure bone graft
Figure II-1-4 Repair of tibial bone defect with allogeneic femoral head bone graft
III. Metal filling technology
Modular technology Modular technology means that metal fillers can be assembled with prostheses and intramedullary stems. The fillers include various models to facilitate the reconstruction of bone defects of different sizes.
Metallic Prosthetic Augments：The modular metal spacer is mainly suitable for AORI type II non-containment bone defects with a thickness of up to 2 cm.The use of metal components to repair bone defects is convenient, simple, and has reliable clinical effects.
Metal spacers can be porous or solid, and their shapes include wedges or blocks. The metal spacers can be connected to the joint prosthesis by screws or fixed by bone cement. Some scholars believe that bone cement fixation can avoid wear between metals and recommend bone cement fixation. Some scholars also advocate the method of using bone cement first and then reinforcing with screws between the spacer and the prosthesis. Femoral defects often occur in the posterior and distal parts of the femoral condyle, so metal spacers are usually placed in the posterior and distal parts of the femoral condyle. For tibial bone defects, wedges or blocks can be selected for reconstruction to adapt to different defect shapes. Literature reports that the excellent and good rates are as high as 84% to 98%.
Wedge-shaped blocks are used when the bone defect is wedge-shaped, which can preserve more host bone. This method requires precise osteotomy so that the osteotomy surface matches the block. In addition to compressive stress, there is also shear force between the contact interfaces. Therefore, the angle of the wedge should not exceed 15°. Compared with wedge-shaped blocks, cylindrical metal blocks have the disadvantage of increasing the amount of osteotomy, but the surgical operation is convenient and simple, and the mechanical effect is close to normal (III-1-1A, B).
Figure III-1-1 Metal spacers: A wedge-shaped spacer to repair tibial defects; B column-shaped spacer to repair tibial defects
Because metal spacers are designed in various shapes and sizes, they are widely used in non-contained bone defects and bone defects of various shapes, and provide good initial mechanical stability. However, long-term studies have found that metal spacers fail due to stress shielding. Compared with bone grafts, if metal spacers fail and need to be revised, they will cause larger bone defects.
Post time: Oct-28-2024
