Parosteal Osteosarcoma Treatment & Management

Chemotherapy and radiotherapy are not very effective in parosteal osteosarcomas. ^[7]  If the tumor specimen is of a high histologic grade, then postoperative chemotherapy is usually advised. ^[8]

Because parosteal osteosarcoma can dedifferentiate and metastasize and can cause local infiltration and destruction, its presence is an indication for treatment. Wide resection with limb salvage is the surgical treatment of choice for parosteal osteosarcoma, in view of the typically low grade of the tumor and the low rate of local recurrence. Amputation is rarely indicated. Hemicortical resection with inlay allograft reconstruction may be useful for treatment of carefully selected tumors. ^[9]

The only relative contraindication for surgical treatment in parosteal osteosarcoma is the presence of multiple metastases in a patient whose general condition is poor.

In planning the wide excision, it is necessary to obtain a clear picture of the extent of the tumor. Various imaging techniques are employed. In cases involving limb salvage and custom-made prosthesis replacement, the measurements are made by means of full-length radiographs, and a hinged prosthesis is fabricated according to the individual patient’s requirements. For the majority of patients, reconstruction can be carried out with a standard off-the-shelf modular endoprosthesis.

Routine blood tests and various investigations are performed to rule out secondary metastasis. The patient’s general condition is assessed with respect to his or her fitness for anesthesia. The patient must be completely informed regarding the procedure; if needed, a tumor counselor should be involved.

Because the tumor is extracortical and is usually present in the posterior aspect of the distal femur, the important neurovascular structures within the fibrofatty tissue must be carefully dissected and preserved. Wide excision should be performed in accordance with preoperative planning on the basis of the measurements in the images. In rare cases, when there is doubt regarding the extent of the tumor at the time of surgery, tetracycline labeling has been used to determine the adequacy of the surgical margins; however, data have not established this practice as useful.

Routine mobilization and physiotherapy are provided as appropriate for a custom-made prosthetic replacement. ^[10] The main postoperative workup involves histopathologic grading of the lesion and assessment of the adequacy of the surgical margins. If the tumor turns out to be a high-grade lesion, postoperative chemotherapy must be considered. Inadequate surgical margins are associated with a high incidence of local recurrence; consequently, postoperative chemotherapy or radiotherapy may be considered in such instances.

Potential complications of tumor resection include the following:

• Impaired wound healing - Superficial wound infection, wound dehiscence, or failure of wound healing may occur
• Infection - Deep infection may be difficult to eradicate, especially in patients with a prosthesis, and repeated wound washing and appropriate antibiotics may be required; persistent infection may lead to implant removal and, in severe cases, amputation
• Hematoma - Postoperative bleeding can lead to hematoma formation in the space resulting from wide excision
• Muscle atrophy
• Neurovascular injury - Because the popliteal neurovascular tissues are closer to the tumor, they may be injured during surgery; intraoperative application of traction can result in neurapraxia
• Stiffness - Because the tumor is close to the joint, postoperative stiffness should be anticipated; regular physiotherapy is needed to overcome this complication
• Implant failure - Implant loosening, polyethylene wear, fracture of the implant, and periprosthetic fracture can result in implant failure
• Local recurrence (common in tumors with inadequate surgical margins)
• Metastasis – In rare cases, late secondary metastasis may develop after surgery, especially with dedifferentiated tumors