Objective: Treatment of tumors of the pelvic girdle by resection of part or all of the innominate bone with preservation of the extremity. Implantation and stable fixation using a custom-made megaprosthesis to restore painless joint function and loading capacity. The surgical goal is to obtain a wide surgical margin and local tumor control.
Indications: Primary bone and soft tissue sarcomas, benign or semi-malignant aggressive lesions, metastatic disease (radiation resistance and/or good prognosis).
Contraindications: Limited life expectancy and poor physical status, extensive metastatic disease, persistent deep infection or recalcitrant osteomyelitis, poor therapeutic compliance, local recurrence following a previous limb-sparing resection, extensive infiltration of the neurovascular structures and the intra- and extrapelvic soft tissues.
Surgical technique: Levels of osteotomy are defined preoperatively by a CT-controlled manufactured three-dimensional 1:1 model of the pelvis. Using these data, the custom-made prosthesis and osteotomy templates are then constructed by the manufacturer. The anterior (internal, retroperitoneal) and posterior (extrapelvic, retrogluteal) aspects of the pelvis are exposed using the utilitarian incision surgical approach. The external iliac and femoral vessels are mobilized as they cross the superior pubic ramus. The adductor muscles, the rectus femoris and sartorius muscle are released from their insertions on the pelvis and the obturator vessels and nerve are transected. If the tumor extends to the hip joint, the femur is transected at a level distal to the intertrochanteric line to ensure hip joint integrity and to prevent tumor contamination. A large myocutaneous flap with the gluteus maximus muscle is retracted posteriorly. The pelvitrochanteric and small gluteal muscles are divided near their insertion in the upper border of the femur. To release the hamstrings and the attachment of the sacrotuberous ligament, the ischial tuberosity is exposed. After osteotomy using the prefabricated templates, the pelvis is released and the specimen is removed en bloc. The custom made prosthesis can either be fixed to the remaining iliac bone or to the massa lateralis of the sacrum. The released muscles are refixated on the remaining bone or the implant.
Postoperative management: Time of mobilization and degree of weight-bearing depends on the extent of muscle resection. Usually partial loading of the operated limb with 10 kg for a period of 6-12 weeks, then increased loading with 10 kg per week. Thrombosis prophylaxis until full weight bearing. Physiotherapy and gait training. At follow-up, patients are monitored for local recurrence and metastases using history, physical examination, and radiographic studies.
Results: Between 1994 and 2008, 38 consecutive patients with periacetabular tumors were treated by resection and reconstruction with a custom-made pelvic megaprosthesis. The overall survival of the patients was 58% at 5 years and 30% at 10 years. One or more operative revisions were performed in 52.6% of the patients. The rate of local recurrence was 15.8%. Deep infection (21%) was the most common reason for revision. In two of these cases (5.3%), a secondary external hemipelvectomy had to be performed. There were four cases of aseptic loosening (10.5%) in which the prosthesis had to be revised. Six patients had recurrent hip dislocation (15.8%). In four of them a modification of the inserted inlay and an implantation of a trevira tube had to be performed respectively. Peroneal palsy occurred in 6 patients (15.8%) with recovery in only two. There were 4 operative interventions because of postoperative bleeding (10.5%). The mean MSTS score for 12 of the 18 living patients was 43.7%. In particular, gait was classified as poor and almost all patients were reliant on walking aids. However, most patients showed good emotional acceptance.