Pelvic Osteosarcoma: Resection and Reconstruction Using a Customised Plate

Introduction: Primitive bone tumours of the pelvis represent a considerable challenge for carcinologic surgeons. Resections made in the acetabular zone could disrupt the continuity of the pelvic ring. The morbidity that comes after such a procedure requires a reconstruction surgery in order to improve the functional outcome. In this aim, multiple techniques have been


Introduction
Ten to 15% of primitive malignant bone tumours are localized around the acetabulum [1,2]. Their prevalence is as much as 10 new case per year per million [3]. Regardless their histological variety, these tumours raise two major technical challenges : fist, large in resection margins have to be respected while resection of a tumour that is often of considerable size because of frequent diagnosis delay [4-7]; second, a complex reconstruction is often mandatory because of the disruption of the pelvic ring. In order to improve the functional outcome after large pelvic resections of these tumours, multiple techniques have been reported such as arthrodesis, prosthetic reconstructions and different bone grafting. We report a right pelvic bone reconstruction using a vascularized fibular autologous graft and stabilized by a customized lombo-femoral plate.
rounding soft tissue calcifications ( Figure 1). ComputedTomography scan (CT scan) confirmed this aggressive lesion of the rightilium (Figure 2). Magnetic Resonance Imaging (MRI) precised that the lesion was located in Enneking zones I and II. However, this first MRI was not able to assess the integrity of the coxo-femoral and sacro-iliac joints with confidence (Figure 3). The spreading investigations were all negative. A surgical biopsy of the lesion was made and the diagnosis of osteosarcoma was histologically confirmed. The patient underwent neoadjuvant chemotherapy. A second MRI assessment was then made, showing a mild regression of the tumour with no extension to joints. A large surgical resection of the whole by a customized long lombo-femoral (Figure 4 and Figure 5). The post-surgery was simple and the wound healed at con-right pelvic bone was then performed. The reconstruction was made using a vascularised fibular graft and stabilized       Figure 6). Figure 7 shows the post-operative plain radiograph (Figure 7). A pelvi-crural cast was crafted and maintained for 6-weeks. The radiological control at 1-year follow-up showed an ongoing bone graft healing process ( Figure  8). Functional outcome was average with the patient being able to walk using 2 crutches (Figure 9).

Discussion
A large number of musculoskeletal tumors can affect the pelvis. Several studies have reported bone sarcomas as the most common lesions, followed by soft tissue sarcomas and metastatic lesions. The most frequently observed pelvic sarcoma is chondrosarcoma, followed by osteosarcoma [8]. Ten to 15% of all primary bone tumors are located in the pelvic bone of which chondrosarcoma in adults, Ewing's sarcoma in children, and osteosarcoma in adolescents represent the most common histological subtypes [9] Pelvic resections are challenging and complex. They are technically difficult due to sometimes the size of the tumor is very large, and anatomically it closes to pelvic viscera and neurovascular structure.Previously,hemipelvectomy was the standard surgical treatment for primary pelvic sarcomas. Recently, with advancements in surgical techniques and chemotherapy and ra-   custom-made endoprosthesis combined with hip arthroplasty [20], modular saddle prosthesis [21] or modular hemipelvic endoprosthesis. Each reconstruction modality has its own risks and benefits [22].
As reported in the early series of Ennekingand, et al. [23], O Connor, et al. [24], Capanna, et al. [25] and Campanacci, et al. [6], patients requiring wide muscle resection with nerve sacrifice underwent arthrodesis.Ilio-femoral, ischio-femoral, femoro-obturator and femoro-sacral arthrodesis have been used. The choice depended on the resection zone in the classification of Enneking and Dunham. In the present case, the patient underwent a lombo-femoral arthrodesis. We did not use a saddle or stemmed prostheses for reconstruction because those were very expensivein our country.
The principle of arthrodesis after pelvis resection is to achieve solid union between proximal femur and the remaining pelvis (iliofemoral, ischiofemoral, or sacrofemoral) using plate, screw, or wire. In the present case, we used a customized plate fixes proximally in the 4 th and 5 th lombar vertebral body and in the femur distally.
The treatment of this pathology is associated to a high rate of complications and a significant declining of quality of life regardless the surgical technique. A high rate of revision is observed in these patients [26]. The two most common post-operative complications are wound infection (with an incidence of 10 to 47%) and local recurrence of the tumour (with an incidence of 28 to 35%) [20,27]. Han, et al. Showed that surgical margin was the factor most closely related to the local recurrence [28]. Our case showed no local recurrence until last follow up. It was probably due to we can achieve wide margin during surgery.
Functional results depend on the extent of resection and the method of reconstruction [29]. The disadvantage of arthrodesis includes loss of the hip joint function. Fusion rates of femoropelvic arthrodesis are < 50%, in most patient, a stable and painless pseudoarthrosis develops, but with a comparable functional result to that of the alternative reconstruction options [30]. Higher non-union rates were reported with patients undergoing chemotherapy and/or radiation therapy [6,15]. Until last follow up, functional result of our patient was average with disappearance of pain and resumption of walking using 2 crutches.

Conclusion
Primitive pelvic bone tumours represent a challenging pathology for surgeons. Acetabular resections disturb the continuity of the pelvic ring and require a reconstruction. In order to improve functional outcome after this delabrating surgery, multiple techniques have been reported. Current data shows that complication rate is high and quality of life is significantly compromised regardless the reconstruction procedure used. Since complication in surgery of pelvis tumor is quite high, approach in the management of pelvis tumor needs multidiciplinary team.