Limb-sparing techniques, also known as limb-saving or limb-salvage surgery, are performed in order to preserve the appearance and function of limbs. Limb-sparing techniques are used to preserve limbs affected by trauma, arthritis, cancers such as high-grade bone sarcomas, and vascular conditions such as diabetic foot ulcers. As the techniques in chemotherapy, radiation, and diagnostic modalities improve, there has been a trend toward limb-sparing procedures to avoid amputation, which has been associated with a lower 5-year survival rate and cost-effectiveness compared to limb salvage. There are many different types of limb-sparing techniques focusing on the preservation or reconstruction of soft tissue, bone, or other vital functional structures.
Bone reconstruction
In bone cancers of the long bones, such as osteosarcoma and Ewing sarcoma, the priority for treatment is complete removal of the cancer with negative margins. In such cases, limb-sparing surgery is preferred when neurovascular structures are not involved. Limb sparing procedures that may be considered include endoprostheses, autograft, and allograft.
Endoprostheses Endoprosthesis refers to metal prosthesis that are used to replace the resected bone.Prosthetic implants are often used when sections of bone must be replaced and no further growth is expected. In children, expandable prostheses may provide a prosthetic reconstruction option. Although these are a versatile solution, endoprosthesis have a high failure rate, often requiring reoperation. Infection, loosening of the hardware, implant wear, and soft tissue dehicense all threaten the long term viability of this reconstruction. There are many prosthetics available, depending on the bone or joint that requires reconstruction and can be temporary or permanent.
Autograft An autograft utilizes a patient's own bone to fill in the area of missing bone. In autografting, a piece of bone that is expendable from another part of the body is moved in order to fill the area with a defect, or missing bone. Both cancellous and cortical bone may be harvested depending on several factors, such as the need of mechanical support and size of the defect. Cancellous bone does not provide mechanical support for a defect but rather provides a scaffold for new bone to grow in due to its osteoinductive nature and high number of osteogenic factors and cells. Cortical bone grafts provide much better mechanical support for a defect, but have very little of the osteoinductive properties found in cancellous bone. Cortical bone grafts can either be taken with associate vascular supply, referred to as a vascularized bone graft, or without. The most common vascularized bone graft is a free fibula graft, where a piece of the fibula is taken along with the peroneal artery and reconnected at the site of the bone defect. Particularly in growing children, the success of reconstructive procedures following cancer surgery is dependent on the location of the tumor and necessary resection. In cases of diaphyseal tumors, biologic replacements, such as allograft is ideal. In tumors involving the metaphyseal region, the growth plate may be affected by the surgery to remove the tumor. In such cases, there is concern for limb-growth disparities due to the disturbed growth plate. When the growth plate of the fibula is included in the graft, it can allow for continued growth of the transplanted bone. Due to this it is often used in cases of proximal humerus sarcoma in young patients and diaphysial reconstruction.
Allograft Allografting refers to the transfer of cadaveric bone to fill in the defect. Typically these procedures are performed in conjunction with metal supports, like plates or rods, as allografts tend to weaken over time and have a higher rate of structural failure. Allografting is the treatment of choice for diaphyseal tumors, small defects, and when the patient is awaiting a custom endoprosthesis. Allografts can be divided into several overarching categories: structural allografts where an intact piece of bone is utilized; non-structural particulate allografts where bone pieces are utilized to fill a small defect; and demineralized bone matrix which extracts only protein, collagen and growth factors from the cadaveric bone with the goal of providing a scaffold for bone growth.
Alloprosthetic composites Alloprosthetic composites are a combination of multiple limb-sparing techniques, namely allografts and prosthesis. Allografts are used to replace the bone that has been resected and then prosthesis is used to support and strengthen the allografts. Alloprosthetic composites are flexible in that surgeons can adapt the implants for any situation.
Soft tissue reconstruction Both trauma and oncologic resection can cause a large defect where removal of enough soft tissue, such as skin, muscle, and fat, leads to the limb being threatened. In the case of insufficient soft tissue to cover the bone or vital structures such as vasculature, tendons and nerves, several techniques can be employed to cover the tissue, including local flaps and free tissue transfer. Furthermore, these strategies can be considered in oncologic cases where there is neurovascular involvement.
Local flap When possible, local tissue may be rearranged to cover the defect. Examples of this type of procedure involve a rotational flap, where tissue with corresponding vasculature is rotated into place to cover the missing soft tissue, and advancement flaps, where the surrounding tissue is freed such that it can be advanced to cover the defect. These methods can be used when a limb is threatened by exposed structures. In a rotational or propeller flap, a specific artery, or perforator, is identified for blood supply of the flap and soft tissue is rotated between 90 and 180 degrees axially in order to cover a specific defect. In the lower extremity, the peroneal, posterior tibial, and anterior tibial arteries have all been described as successful sources of propeller flap blood supply. The flap, composed of skin and fascia, is used to cover any exposed vital structures, like nerves or bone.
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