CORRInsights®: Is Limb Salvage With Microwave-induced Hyperthermia Better Than Amputation for Osteosarcoma of the Distal Tibia?

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Osteosarcomas at the distal tibia pose considerable challenges to limb salvage surgery. Any soft-tissue mass in the distal leg lies in close proximity to the important tendons and neuromuscular structures narrowing the sought-after wide margin for limb salvage. Though osteosarcomas at the distal tibia are rare (< 4% of all osteosarcomas), several forms of reconstruction have been described, and there are problems with each. Prosthetic reconstruction is associated with frequent complications [1, 9, 14], and allografts have high rates of nonunions and delayed unions [2, 13]. Vascularized fibular autografts (either pedicled or free) are technically demanding, lengthy procedures associated with a protracted convalescence during which weight bearing is limited [4, 8, 15, 16]. Nonvascularized fibular grafts carry the risk of stress fracture, particularly with longer segments and also take time to hypertrophy. Bone transport is satisfactory for shorter lengths but also risks junctional nonunions [8]. External fixation wires and pins can be a problem for those on chemotherapy. These complications can undermine the benefits associated with limb salvage, which has been shown to provide superior function compared to amputation [13], the historical surgical treatment for osteosarcoma.
Hyperthermia has long been used to ablate tumors. But unlike radiofrequency ablation, which requires a conductive field for heating, microwaves can heat tissues by transmitting kinetic energy to polar molecules like water. Microwaves can transfer heat through charred tissue. Tissues, like bones and lungs, are better treated with microwaves than radiofrequency ablation [12, 17] because microwaves, by using multiple antennae, can heat larger tumor volumes faster and at higher temperatures than radiofrequency ablation. Therefore, microwaves are the ideal way to generate heat for larger volumes of tumors in bone tissues.
The development of needle-like, internally-cooled antennae allows for more energy to dissipate with more uniform heating. Placing multiple antennae in specific configurations can rapidly achieve the temperatures required for tumor ablation. Monitoring the temperature within the tumor, and in vital areas like joint cartilage or neuromuscular bundles, help limit potential damage.
Building off of the results from previous studies [5, 6], Han and colleagues use an unconventional approach for limb salvage in distal tibial tumors. In order to avoid a complete bony osteotomy at the proximal site, the authors used microwave-generated hyperthermia to ablate the tumor after dissecting and isolated the tumor with margin from the surrounding tissues.
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