e22012 Background: Primary Extremity Bone Sarcomas (PEBS) were historically managed by upfront amputation. Early success rates utilizing neoadjuvant chemotherapy followed by LSS showed promise in halting disease progression and achieving local control. This prompted surgical oncologists to consider LSS in more patients. In anatomic locations for which no functional reconstruction exists, amputation is still considered the best option. Oncologic control, patient satisfaction and improved function are the primary goals of LSS. Three Dimensional CT and MRI have made for more accurate surgical planning, ensuring adequate margins and improved local control. Methods: Between January 1983 and December 2019 the senior author (BNR) has performed, or mentored over 590 LSS worldwide.Improvement in imaging modalities has been the most important advancement contributing to decreasing tumor margins. Initially bone scans determined the margins at 7cm. In the 1970s CT became the modality used to determine local tumor extent. The resection margins were reduced to 5 cm. The early 90’s saw MRI as the main imaging modality. Margins are now set at 1-2cm.LSS was initiated in the mid 80’s using the strict criteria of age > 13, no metastasis, intramedullary extension less than 50%, and small extraosseus extent. Results: Of the 134 cases enrolled through 1990, the local control rate was 90%. Between July 1991 through December 2019, 388 patients enrolled in bone sarcoma protocols, 354 patients underwent LSS ( > 95%). The primary site was the femur (171 cases, 43%) Histological Diagnosis was OS in 93%. Ages ranged from 3-25 years (median 10.8 years) The average length of tumor resection was 7cms(range 1-38cms). 5 patients presented with pathological fracture. All successfully underwent LSS without an increase in local recurrence. Intraoperative complications included, excessive hemorrhage defined as > 10%of blood volume in 88 patients, 25%, Vascular injuries requiring repair in 9 patients, post operative neuropraxia in 28 patients. Mid and late term complications included, Superficial wound infection in 45 patients (19 requiring some surgical intervention), Deep wound problems were identified in 11 patients ( 3 required subsequent amputation), 9 patients had their prosthesis revised due to refractory infection, Local relapse in 5 patients , < 1%. Long term implant related complications, loosening of the prosthesis in 16 , Stem fracture in 13, nonunion of the allograft in 3 patients. Conclusions: Disadvantages are the need for repeat surgeries consequent to either growth discrepancy, loosening, or implant fracture.LSS is feasible in over 95% of patients, complications are generally manageable. Successful oncologic results, satisfaction and function are readily obtained. Early rehabilitation is key to functional success.