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  Introduction

Osteosarcoma is a very aggressive, common primary malignant bone tumour. It usually occurs at the metaphyseal region of long bones, with distal femur, proximal tibia and proximal humerus being the commonest sites [1]. 2% is the incidence of occurrence of osteosarcoma in proximal fibula [2]. Treatment protocol is usually pre-operative chemotherapy, wide resection/ amputation/ limb salvage and post-operative chemotherapy. The long term survival rate has improved with advances in the treatment protocols.

Patient 1

26-year-old newly married lady, a software professional, presented to orthopaedicOPD with ahistory of pain, diffuse swelling over the infero-lateral aspect of right knee (Figure1).It is of4 months duration and she is unable to bear weight onthe affected limb in the last15 days.She did not consult any doctor earlier and was managing her pain with over the counter medication. Deep peroneal nerve was intact.X-ray revealed a large, diffuse lytic lesion in the proximal fibula (Figure2), which was suggestive of osteosarcoma. MRI revealed soft tissue extension.Open biopsy confirmed a high grade osteosarcoma. CT scans of abdomen and chest revealed no metastases.As the limb could not be salvaged due to extra compartmental spread, an above knee amputation was performed. Three months later, after two cycles of chemotherapy, she presented with pain abdomen and was diagnosed to have lump in the abdomen, which was resected. Biopsy confirmed it to be metastatic deposit with divergent (myogenic) differentiation. At 30 months follow up, she is fit and healthy, leading a happy married life with no complaints and comfortably walking with her above knee prosthetic leg.

Figure 1:Clinical picture of the swelling of patient one.

Figure 2:Radiograph of patient one showing aggressive lesion of proximal fibula indication of malignancy.

Patient 2

19-year-old male student presented with a history of pain and swelling over the infero-lateral aspect of left knee of 3 months duration.X-rays revealed a lytic lesion in the proximal fibula (Figure3). MRI was suggestive of osteosarcoma withoutsoft tissue extension (Figure4). CT of abdomen and chest revealed no metastases and biopsy showed low grade osteosarcoma (Figure5). Because of the intra-compartmental nature of the lesion and low grade on histology, limb salvage was planned. Wide resection of the tumor was done after neo-adjuvant chemotherapy. Common peroneal nerve was sacrificed during resection of the tumor. Patient received post-operative chemotherapy. At 3 years follow-up the patient is leading a comfortable life, with ankle-foot orthoses for the foot drop. Presently he is being planned for reconstructive procedures for foot drop.

Figure 3:Radiograph of patient two, showing lytic lesion of proximal fibula.

Figure 4: MRI axial section of patient two, showing lesion in the proximal fibula, with soft tissue extension.

Figure 5: HPE: of case 2, showing high power microscopy showing irregular bony trabeculae separated by spindle cells seen in osteoid background.

Discussion

Osteosarcoma is one of the most common primary malignant tumours occurring duringthe second decade of life. It occurs in the metaphyseal region of long bones, commonly involving the distal femur, proximal tibia, and proximal humerus. Proximal fibula is a very rare site representing about 2% of all osteosarcomas [3]. Amputations were the treatment of choice historically, but in recent times the aim is to salvage the limbcombined with chemotherapy, to prevent metastasis. An above knee amputation is still preferable procedure to limb salvage when the following situations are encountered: Gross invasion of the tibia, extensive multi-compartment involvement especially of the posterior deep compartment, multi-compartment contamination from a previous biopsy or attempted resection, anomalous vascular patterns, especially absent posterior tibial artery, and intra-articular extension of the tumour. Long-term survival for osteosarcoma has improved dramatically during the late 20th century and approximated 68% in 2009 [2]. Limb salvage procedure might involve removing much of the lateral compartment including the common peroneal nerve resulting in foot drop and knee instability. Complete removal of the tumour should never be compromised for a better functional outcome. There are reports in the literature however where, intentional marginal resection of the osteosarcoma of the proximal patient of fibula is done,in order to preserve the limb function [4-6].

Conclusion

Utmost care should be taken in diagnosing osteosarcoma with its unusual presentation in the proximal fibula as it is uncommon. With timely diagnosis,limb salvage is an attractive option for treatment, for the young patients to get on with their daily living. On the other hand, with a high grade tumour, salvaging the limb might result in an inadequate tumour excision, in which case one should not hesitate to perform amputation. Surgery combined with chemotherapy will give good outcome with a better survival rate.

Acknowledgement

The Departments of Radiology & Imageology, and Pathology, Krishna Institute of Medical Sciences (KIMS), Secunderabad.

Conflicts of interest

Authors declare no conflicts of interest.