Knee reconstruction with endoprosthesis after extra-articular and intra-articular resection of osteosarcoma.

Objective: Extra-articular resection is necessary to obtain a wide margin for primary osteosarcomas invading the knee joint, and the limb is often reconstructed using a prosthesis. Here, outcomes of extra-articular and intra-articular procedures were compared.

Methods: Between 1999 and 2012, 14 patients with osteosarcoma underwent extra-articular excision (n = 6; ages 23-65 years; mean follow-up 82.8 months) or intra-articular excision (n = 8; ages 8-58 years; mean follow-up 96.4 months). In the extra-articular group, there was one Enneking Stage IIA case and five Enneking Stage IIB cases. No local recurrences were noted in either group.

Results: Patient outcomes were as follows (extra-articular cases vs. intra-articular cases): continuous disease-free (2 vs. 7), alive with disease (2 vs. 0) and death from disease (1 vs. 1). Average Musculoskeletal Tumor Society functional scores were 69.4% (range 63.3-83.3%) and 88.3% (range 70.0-96.7%) in the extra-articular and intra-articular groups, respectively, constituting a significant difference (P < 0.05). The 5-year oncological overall survival exceeded 80% in both groups. Amputation was necessary for one patient in the extra-articular group. The 5-year event-free prosthesis survival rates in the extra-articular and intra-articular groups were 33.3 and 75.0%, respectively (P < 0.05).

Conclusion: The extra-articular excision group developed more complications than the intra-articular excision group, as a result of extensive bone and muscle excision. The limb survival rates were similar in both groups. Our results suggest that extra-articular resection was a necessary and clinically acceptable procedure.