KNEE EXTENSOR MECHANISM RECONSTRUCTION IN TUMOR SURGERY AFTER ISOLATED EXCISION OF EXTENSOR APPARATUS OR EXTRARTICULAR TOTAL KNEE RESECTION

Abstract

Knee extensor mechanism reconstruction after excision for bone or soft tissue tumors is a challenging procedure. When a resection of the patellar bone-tendon apparatus is required, an omologous graft can be used for its reconstruction to avoid knee arthrodesis and preserve a functional knee. Since 1996 we performed such a procedure in 15 cases in 14 patients. In 4 cases (Group 1) excision and reconstruction involved only the patella and the attached tendons together with the involved soft tissues. In the remaining 11 cases (Group 2) an extrarticular en-bloc knee resection was accomplished and reconstruction was obtained by a megaprosthesis to replace the distal femur and a composite allograft-prosthesis to replace proximal tibia and the extensor apparatus. One of the en-bloc knee resections was performed in a patient who had previously had an isolated extensor apparatus replacement, which was later converted to a complete knee resection and substitution after a local relapse.

A free flap (anterolateral thigh) was used in 4 patients.

Histotypes were as follows:

• Group 1: pleomorphic sarcoma 2, synovial sarcoma 1, myxofibrosarcoma 1.

• Group 2: osteosarcoma 3 (distal femur 2, proximal tibia 1), Ewing sarcoma 2 (proximal tibia 1, patella 1), giant cell tumor 1 (proximal tibia), chondroblastoma 1 (distal femur) synovial sarcoma 3, pleomorphic sarcoma 1.

One patient in group 2 was lost at follow-up after a few months. In the remaining patients follow-up ranged from 7 to 132 months.

In Group 1 two local and one distant (groin lymphnodes in one of the two patients affected by local recurrence) relapses occurred, in Group 2 one local and 4 distant relapses (lung) occurred. One of these latter distant relapses affected the patient at the beginning in Group 1 and later converted to Group 2.

Besides recurrences, 4 patients in Group 2 were affected by local complications:

• one deep infection;

• one extended resorption of the tibial allograft, which required a two-stage revision (extensor apparatus allograft could be saved);

• one rupture of the patellar tendon allograft after almost 9 years after the first procedure. The ruptured allograft was replaced by an achilles tendon allograft;

• one deep vein thrombosis.

Active extension was initially obtained in all patients and, when local complications did not occur, it was stable with time. Extension lag ranged from 0 to 30°. Maximum flexion ranged from 80 to 110°. Patients could walk without brace nor aids.

Allograft reconstruction after extensor apparatus excision, either alone or combined to a total knee resection, can be an efficacious option in the treatment of sarcomas of the knee.