We reviewed twenty-nine immature participants (younger than 15 years) with high-grade osteosarcoma around knee, between January 2009 and December 2013 at one institution. This research has been approved by the Institutional Review Board (IRB) of our institutions. Principles of all research were followed and all procedures were conducted according to the guidelines established by WMA Declaration of Helsinki – Ethical Principles for Medical Research Involving Human Subjects. Informed consent was obtained from all subjects or, if subjects are under 18, from a parent and/or legal guardian.
The patients in this study underwent neoadjuvant chemotherapy and expandable prosthesis reconstruction after tumor resection. The series included nineteen male, ten female patients, with a mean age of 10.5 years(range 6 to 15 years). Twenty-six lesions were located at the distal femur, three at the proximal tibia. All patients had Stage IIB tumors according to the Ennecking staging system12.
All of the patients received neoadjuvant chemotherapy. The chemotherapy protocol consisted of ifosfamide, methotrexate and doxorubicin. Ifosfamide was given at 2 g/m2/d on days 1 to 5 while methotrexate 8 g/m2/d on day 3. Doxorubicin was administrated at 40 mg/m2/d on day 5. 3 cycles later, the eligible met the following inclusion criteria: (1) having complete fat edge surrounding tumor in MRI, (2) not invading popliteal (tibial) artery and vein, not invading tibial (peroneal) nerve, (3) without detecting metastasis, (4) without active infection. Nine individuals were added 1 course because of the broad invasion of lesion. Considering preoperative reaction and tolerance, 6–9 courses chemotherapy would be finished postoperatively.
Age and tumor extension were treated as main factors to use expandable implant reconstruction. Magnetic resonance imaging(MRI) was mandatory for excluded any joint contamination and surgical planning. Wide resection margins were attained in patients. The initial length of expandable prosthesis was 2 cm longer than resected specimens. The average length of prosthesis gained was 18 cm. The average prosthesis diameter was 1.14 cm. Stem length was 14.8cm[Table 1]. The patellar tendon was reattached in prosthesis groove in 3 patients with proximal tibia osteosarcoma. A medial gastrocnemius muscle flap was used to rebuilt soft-tissue coverage of the device in 2 patients with insufficient normal soft-tissue.
The discrepancy was defined as the different length from anterior superior spine to malleolus medialis, and pelvic incline. Patients were considered for external limb lengthening with the difference over 3 cm. Minimal invasive surgery was conducted to lengthen the implant. The expandable prosthesis had a lengthening mechanism composed of two titanium alloy tube connected with screw[Figure 1]. The titanium alloy tube was rotated and expanded, lengthening the prosthesis. It takes 360°rotation to obtain 1 mm expansion. It is locked by variable size of prolonged loop embedded in the gap between two alloy tube[Figure 2]. The length of expansion was shorter than 2 cm every time to avoid the nerve strain injured.
The early weight bearing, active and passive motion was continued postoperatively. To ensure the tension union, activity were delayed about 3 weeks in patients with patella ligament reattachment. All patients were examined limb X-ray, lung CT per 6 months in follow-up. PET was conducted every year. The purpose was to detect local control and distal metastases.
We collected clinical records( including sex, age, location of lesion, pathological fracture, resection length), the course of chemotherapy, the change of alkaline phosphatase between pre- and post-treatment13, and prosthesis characteristics( device length, stem diameter, stem length, time of lengthening, complication). We analyzed survival rate by the Kaplan-Meier method. The functional results were estimated by Musculoskeletal Tumor Society (MSTS) at 6 months postoperatively. The six items were scored on a 0(worst) to 5(best) scale, including pain, function, emotional acceptance, supports(brace, cane, crutches), walking ability and gait. Functional outcomes were ranked by score as follows: excellent(at least 23 points), good( 15 to 22 points), fair( 8 to 14 points), and poor( less than 8 points)14.