Limb preservation therapy has become the standard of care for most osteosarcomas. Surgery requires removal of the tumor tissue as well as the normal bone and soft tissue adjacent to it in order to obtain adequate surgical margins. Removal of the tumor often results in the surgeon being faced with a large deficit, thus requiring a multifaceted effort to reconstruct the function of the limb. Biological reconstructive modalities including allogeneic or autologous bone grafting have a long history in this type of surgery. Although, these modalities are still the dominant treatment modality, there are still complications such as: bone discontinuity, fractures, donor disability, fixation failure, graft resorption, and prolonged braking time. When complications occur, multiple surgical procedures are often required to manage them. To avoid the complications associated with grafting, metal endoprostheses have become the treatment modality of choice in many cases. These large metal implants are not suitable for adhesion to the muscles or ligaments of the limb. There have been studies on the use of biomaterials to improve the biological fixation of existing implants as well as to resist the increased cyclic loading that results from limb preservation surgery leading to prolonged limb survival. These biomaterials include cobalt-chromium alloys as well as titanium. The use of these built-in prostheses has faced complex complications such as periprosthetic loosening, wear, metal fatigue and failure, and infection. This study introduces a new biomaterial in trabecular metal (porous tantalum, Zimmer Corporation) as a reconstructive built-in prosthesis material. Earlier laboratory studies comparing porous tantalum to other porous materials confirmed that porous tantalum allows soft tissue attachment and strength, with bone growing-in properties compared to other conventional porous materials while remaining biologically inert. In this study, arthroplasty was performed with seven custom-made porous tantalum built-in prostheses/large prostheses after limb-sparing surgery in seven patients with osteosarcoma. The group retrospectively summarized whether the use of porous tantalum-built prostheses had potential benefits over conventionally designed prostheses, as well as evaluated the durability of porous tantalum after limb preservation and described the use of porous tantalum custom-made prostheses to fill large skeletal voids after early limb preservation surgery. Although porous tantalum endosseous implants have been routinely used in initial and revision arthroplasty, the use of porous tantalum in combination with oncologic prostheses has not been reported. Although limb-preserving surgery is effective and an accepted local treatment for musculoskeletal tumors, there remains the difficulty of reconstructing the defect created if large bone and soft tissue are adequately removed. As patients survive longer, the implant used to reconstruct the defect must be durable and tolerated. In this study, porous tantalum demonstrated success in early reconstruction of a large defect, integration of bone with the implant, and soft tissue adhesion by providing initial stability. There is one case report of the use of a porous tantalum cuff to aid in the reconstruction of the abductor muscle during post-traumatic hip arthroplasty. Although similar to the muscle and soft tissue growth into the situation in this case, no large prosthesis was used in this patient. The biomechanical properties of porous tantalum are well suited to the use of large prostheses. The stiffness of porous tantalum is close to that of bone trabeculae, however, its stress-strain properties are close to those of metals. In contrast, titanium and nickel-cobalt alloys are approximately 100 times stiffer than porous tantalum and cancellous bone. The biocompatibility of porous tantalum facilitates osseointegration at the bone-implant interface and maintains its physical properties to withstand cyclic loading. However, the porous structure of the component requires that the extension rod, articular surfaces and shaft made of metal alloy be surrounded by porous tantalum for fixation. As demonstrated in 2 patients, perhaps the most beneficial feature is the exposed 3-dimensional structure to allow soft tissue and blood vessels to grow in. Tantalum has properties suitable for implant use, is located in the Vb group of metals on the periodic table, has high density properties, a very high melting point and, most importantly, excellent corrosion resistance. Currently, it is used in electrolytic capacitors and corrosion-resistant chemical equipment. In biological research, tantalum is used in coronal stents, oral implants, and as a biological marker in a variety of studies in vivo. Porous tantalum built-in prostheses are formed by infiltrating tantalum gas into a fabricated carbon skeleton of defined morphological dimensions. Porous tantalum has a porosity of 70-80%, forming interconnected pores in a 12-sided shape. Its porosity is 2-3 times higher than the 25-30% porosity found in porous coatings, where the original coating was formed by sintering. The pore structure of porous tantalum is a homogeneous three-dimensional structure. These interconnected voids have an influence on the long entry of soft tissue and bone by about 400-500 μg. Initial laboratory studies comparing porous tantalum with other porous substances confirmed the characteristics of bone ingrowth and enhanced attachment of soft tissue. the prospective study by Jacobs et al. on the application of porous tantalum in arthroplasty concluded that both the original clinical data and the underlying findings support further porous tantalum as an alternative to conventional implant materials. Cortical external bone bridges may be a theoretical advantage in enhancing prosthesis survival in large prosthetic arthroplasty. the Mayo Center 2000 reported on 15 lower extremity implants since 1976 to 1990, they collected beaded porous titanium fiber surfaces applied to autogenous bone grafts in 10 hips and 5 knees, with a 5-year survival rate of 80% and 10-year survival rate for large prosthetic implants in the proximal femur Unwin et al. reported 1001 cases with the largest non-beaded large prosthesis such implants. The UK reported 94% 10-year survival for proximal femoral prostheses and 60% survival for large knee prostheses. Cortical external bone bridges appeared to contribute little to the survival of the prosthesis. The minimum survival time for patients 5 and 6 implanted with porous tantalum large prostheses reported by this group was at 6 years (83%). However, bone ingrowth is perhaps not the most important advantage of porous tantalum compared to soft tissue ingrowth. The authors concluded that distal femoral replacement with a histoplasmic tumor hinge prosthesis has excellent outcomes and that most patients in this group would have been similarly managed with a conventional histoplasmic tumor prosthesis, but soft tissue integration is very difficult and the ability of porous tantalum to provide a tissue-to-metal bridge is perhaps the greatest available point. Porous tantalum facilitates soft tissue ingrowth compared to other alloys. We found that limb muscle adhesion to a large proximal femoral prosthesis was a potential functional advantage over the currently available prostheses and techniques in this group. Patient 1’s knee fibrosis may manifest as excessive soft tissue growth from the extensor device into the porous tantalum. The use of porous tantalum reconstruction in large bone defects around the hip and shoulder has shown to optimize implant performance. The design and implantation of the seven implants in this group was performed prior to the mass production of porous tantalum implants. The authors concluded that porous tantalum implants are undergoing innovation and that an existing porous tantalum prosthesis contains small areas of porous tantalum that are planned to facilitate bone and soft tissue ingrowth. This study exemplifies the versatility of porous tantalum, particularly as a custom prosthesis used in the reconstruction of a large number of bone defects. The need for porous tantalum is growing not only for oncologic prostheses, but also when large bone defects are left behind during revision, as the demand for prostheses that can provide greater functionality increases. Large samples of studies comparing the versatility of porous tantalum with other prostheses are still needed.