MRI proves accurate for pre-operative limb salvage procedure assessment

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MRI should be considered as a part of the pre-operative assessment of osteosarcomas, particularly when a limb-salvage procedure is contemplated, with attention given to the long-term quality of life for patients, according to a study published in the June issue of Orthopedics.

Currently, in most cases, limb-salvage surgery offers an improved functional outcome without compromising survival and avoids the need for amputation and external prosthetic devices, which have secondary complications. The techniques have been made possible with the introduction of effective neoadjuvant chemotherapy and the high degree of accuracy in local staging.

Researchers from the hospitals within Shandong University of Traditional Chinese Medicine in Jinan, China, sought to evaluate the accuracy of T1-weighted MRI in determining the osteotomy plane in 21 patients with osteosarcoma undergoing limb-salvage surgery.

Twelve cases involved the distal femur and nine cases involved the proximal tibia. Mean patient age was 16.3 years (range, 12-24 years). None of the patients presented with evidence of metastasis. After being placed on neoadjuvant chemotherapy, all patients were treated with en bloc resection and a custom prosthesis. Intramedullary extension was measured on preoperative MRI and radiographs, and also on postoperative specimen by gross and histopathological evaluation.

The study investigators found that MRI could be used safely to plan resection margins without the need for intraoperative frozen section assessment. “We were able to define the osteotomy plane at 30 mm distal from the primary tumor based on MRI. The average rate of functional recovery was 70 percent, with excellent function and joint stability achieved in 16 patients. The relatively high rate of distant metastasis (14 percent), and thus the high rate of mortality, may be related to a resistant tumor. The possibility of resistant disease and inefficiency of chemotherapy are important factors that may influence the outcome of limb-salvage surgery,” the authors wrote.

The results showed that MRI is accurate in determining the transphyseal spread of tumor into the epiphysis and is sensitive for detecting intra-articular involvement. However, MRI is not specific for joint involvement, and peritumoral inflammatory changes may cause a false-positive diagnosis that can lead to unnecessary radical surgery, according to the investigators.

“Our findings indicate using 30 mm distal from the primary tumor as the osteotomy plane based on T1-weighted MRI is safe. Hence, MRI should be considered as a part of the preoperative assessment of osteosarcomas, particularly when a limb-salvage procedure is contemplated. Ultimately, attention should be given to the long-term quality of life for patients,” the authors concluded.