1 Introduction

Bone tumors are common in the proximal tibia in immature skeleton. It includes primary malignant and benign tumors. Incidence of benign aggressive tumors in the immature skeleton, though rare has been reported in the proximal tibia (metaphyseal region included). The challenges in such patients include diagnosing the tumor, classifying/staging the disease and most importantly to decide on the treatment. Spectrum of the treatment options range between curettage, excision with reconstruction, ablative procedures including amputation. There are pros and cons for each of them. We would like to share our experience in the treatment of 2 cases of proximal tibia lesion in paediatric age group. In spite of the controversy during the planning of the treatment, we chose to proceed with limb salvage and biological reconstruction of the defect with free vascularized fibular bone grafts (FVFGs) and implants (plate and screws) (see Fig. 4) (Fig. 5).

2 Case 1

A six year old girl was brought to our OPD by her parents with complaints of pain in the right knee for the previous 15 days. She also had complaints of swelling in the right knee for the same duration, but the swelling was rapidly growing in size for previous few days. Parents attributed the pain and swelling to a trivial trauma the child had while playing at her school. On detailed history taking, the fall was determined to be insignificant. On clinical examination, we found a bony hard tender swelling in the proximal part of the tibia extending in the anterior, lateral and medial aspects. The range of movements of the right knee was about 0–80°, which was grossly restricted in comparison to the left knee and was also associated with pain.

Plain radiographs were done and revealed an osteoblastic lesion over the metaphyseal region of the right proximal tibia. Sunburst pattern of matrix mineralization was pronounced. Margins were well delineated and had wide zone of transition. Codman's triangle was also made out in the periosteal reaction. Higher radiological investigation of MRI showed an expansile mass lesion in the metaphyseal region of the right proximal tibia. Basic blood investigations were done and showed an elevated erythrocyte sedimentation rate (ESR) and alkaline phosphatase (ALP) levels. Positron emission tomograms (PET scan) showed no active uptake in any other musculoskeletal and visceral regions other than in the right proximal tibia.

Core needle biopsy was taken after following all the principles for closed biopsy (along the line of the proposed surgical incision). Histopathological examination revealed marked atypia, pleomorphism and disorganized woven bone formation in lacy pattern-indicating a conventional osteosarcoma. Thus a diagnosis of central (intramedullary) conventional osteosarcoma of the proximal tibia was made. Tumor board comprising of orthopaedicians, surgical oncologist, paediatric oncologists and pathologist was constituted.

The parents and grandparents were not willing for any form of ablative procedure. They were insisting on limb salvage. It was decided in the tumor board to start the child on neo adjuvant chemotherapy. The EURAMOS (European and American Osteosarcoma Study) protocol was followed. Pre-operative chemotherapy comprised of five cycles (weekly) of methotrexate, doxorubicin (adriamycin) and cisplatin. Two such cycles of neo adjuvant chemotherapy was given lasting for a period of 10 weeks. After completing the two cycles, a two-week period of rest was given. Repeat plain radiographs were done and it was decided that the resection of the lesion would include the entire articular (epiphyseal) part of the proximal tibia in addition to the metaphyseal part and diaphysis (shaft) to an extent of 14 cm from the articular surface.

The challenges were in deciding the management of the defect that will arise after the resection of the lesion and how to retain growth in the distal femur epiphysis after graft placement. The option of custom mega prosthesis for a child was ruled out and the parents did not entertain an ablative procedure with subsequent exoprosthesis use. Thus, FVFG was harvested from the opposite side and it was used a bridge between the distal femur and the remaining tibia. The modification, which we followed, was that, we made a opening in the distal femur intercondylar region and shoved the fibular graft into the opening, such that the fibular graft was still distal to the physis. We fixed the fibular graft with a 16 hole locking compression plate (4.5 mm – Combihole plate). The plate was fixed in such a way that it would stabilize the reconstructed joint, the position of the screws were done in a way that the distal femur physis was spared as shown in the diagram (Fig-1). This ensured continued growth of the distal femur physis in the future (see Fig. 2).

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Fig. 1 (A) Presenting radiograph showing metaphyseal obsteoblastic lesion. (B and C) MRI confirming the sunburst pattern and Codman's triangle. (D) Post-chemotherapy radiographs.

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Fig. 2 (A) and (B) Intra-operative photos showing the level of skin incision and the extent of the excised lesion.(B) Immediate post-operative radiograph showing the fibular graft shoved into the distal femur.(C) 1 year follow up radiograph showing satisfactory uptake.

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Histopathology of the resected specimen confirmed the diagnosis of conventional osteosarcoma with 15 % tumor necrosis and margins to be free of malignancy. Nine cycles of chemotherapy was given over a period of 40 weeks. She was not allowed to walk for a period of 2 months, after which protected weight bearing was given for a period of up to 6 months. She was followed up for a period of 5 and half years post the surgery and radiologically, the graft incorporation was 100 %. The presence of Harris growth arrest lines indicated that the growth continued to occur. There is at present a limb length discrepancy of 7 cm in comparison to the opposite normal leg. There is, however, scope of lengthening in the femur segment by means of corticotomy and transfer once the child completes the second growth spurt.

3 Case 2

16 years old adolescent girl presented to our OPD with complaints of pain and swelling of the left knee and proximal aspect of the leg following a trivial fall associated with difficulty in walking for the past 5 months. Clinical examination revealed swelling over the proximal third of left leg with tenderness and broadening on palpation of proximal tibial metaphysis with painful terminal flexion of knee movement and intact distal neurovascular status. No swellings were noted elsewhere in the body. Routine blood parameters were normal except for insufficient vitamin-D level of 20.4 IU and elevated serum phosphorus of 5.2. Plain radiograph showed an osteolytic lesion of the proximal tibial metaphysis involving 90 % of the diameter of the bone with bony expansion and pathological fracture without any skip lesions. MRI evaluation showed a circumscribed lobulated lesion of size 7 × 4.3 × 4.6cm below the physeal line till metadiaphyseal junction. Tumour was heterogeneously hypointense on T1 and T2 (Fig. 1). MR Angiogram revealed normal vascular status of left lower limb. Patient had Campanacci grade III and Enneking grade II-B GCT radiologically. Core needle biopsy was done from the anteromedial side (with multiple samples) and Histopathological examination revealed mitotically active Giant cell tumor of left proximal tibia. Patient was provisionally diagnosed as Left proximal tibia GCT.

Tumor panel was constituted in view of a) the tumor involving the entire metaphysis which requires wide local excision or extended curettage involving the articular surface with arthrodesis of knee joint b) skeletally immature (16 yrs) patient - as the role of endoprosthesis is questionable in view of revision surgeries c) GCT in immature skeleton itself being rare and d) GCT uncommon in metaphysis. After serious deliberation, she was treated by en-bloc resection of the tumor with extended curettage with burr followed by FVFG from the contralateral side and proximal tibia plating with extensor mechanism reconstruction using a mesh of the residual tibia. Intra-operative histopathology confirmed GCT of immature skeleton. Patient was immobilised with above knee slab during immediate postoperative period. Simultaneous in-bed mobilization and quadriceps, hamstring strengthening for the contralateral leg was started. 3 months later, iatrogenic proximal tibiofibular synostotic bone grafting from right iliac crest was done for the ipsilateral side. Periodic wound assessment was done. Patient was started on non-weight-bearing mobilisation with walker support and extension brace/orthosis for the left lower limb by 3rd month. By the end of one year patient was started on partial weight bearing with walker support and tolerable knee range of movement exercises.

By one and half years, satisfactory radiographic proximal tibiofibular synostosis was achieved (Fig. 3). By the end of 2 years, adequate proximal tibiofibular synostosis was achieved without any signs of recurrence with adequate graft uptake (Fig. 3). Patient was started on full weight-bearing mobilisation by 2 years with walker support. By two years and three months, patient started full weight-bearing mobilisation without support and has obtained knee flexion from 0 to 90°.

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Fig. 3 (A) Presenting radiograph showing osteolytic lesion with pathological fracture. (B) Coronal T1 and STIR images showing large intrameduyllary infiltrating lesion in metaphyseal-diaphseal region. (C) Axial T1, T2 and STIR images showing central necrosis and haemorrhagic degradation products.

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Fig. 4 (A) and (B) Intra-operative photos showing the extent of the excised lesion. (C) Immediate post-operative radiograph showing the fibular graft and the fixation (D) 6 months follow up radiograph showing satisfactory uptake.

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Fig. 5 (A) and (B) Latest X-rays and clinical photos of Case 1 and Case 2 respectively.

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4 Discussion

For a major part of the 19th century, the treatment of choice of musculoskeletal tumors was ablative procedures like amputation or disarticulation owing to high rates of recurrence or/and mortality. It was only after the Second World War that limb salvage procedures like megaprostheses were developed, thanks to pioneering work done by John Scales and Merle d’Aubigne.^1,2 Advancements in the form of angiography, CT, MRI and bone scintigraphy further fuelled the success of reconstruction procedures.

In musculoskeletal oncology, the primary aim of salvage procedures is to restore the functional length and facilitate early return of the patient to their normalcy. It usually involves complete resection of the tumor and reconstruction of the limb. Such procedures should ideally yield a good surgical, functional and psychological outcome without compromising on the complete abolishment of the tumor. The indications for salvage procedure include but not limited to – 1) tumors in axial or appendicular skeleton, 2) tumors amenable to resection with safe surgical margins, 3) minimal soft tissue extension, 4) no signs of neurovascular compromise or 5) of infection, 6) good compliance.¹ Nevertheless, the decision between ablative and salvage procedures is usually dependent on the type, size, location and extent of the tumor.²

Musculoskeletal sarcomas account for about 1–10 % of all malignant tumors.³ Following the advent of adjuvant chemotherapeutic agents (like Methotrexate, Adriamycin)⁴ and radiotherapy, survival rates improved from 20 % to 60–80 %.^3,5 Reconstruction with endoprosthesis is common owing to its optimum functional outcomes and early weight bearing. However, the major disadvantages include financial burden, loosening and infections.³ On the other hand, biological reconstruction alleviates such problems as it involves the use of vascularized (viable) and devitalized or non-vascularized (non-viable) autograft or allograft.

Microvascular free fibula transfer is considered an optimum autograft due to its strong cylindrical construct with the potential to hypertrophy.⁵ They offer both physiological viability and mechanical stability but the scarcity of donors, the need for adaptation at the recipient site and demand for high level of surgical expertise limit their use.⁶ Innocenti et al.⁷ observed good mean “musculoskeletal tumor society (MSTS)” scores following the use of free vascularized fibular graft after excision of proximal tibia bone tumors.⁸ Similarly, in a retrospective study done by Leilei Xu et al.,⁷ 18 patients with osteosarcoma managed with vascularized fibular graft with neo-adjuvant and adjuvant chemotherapy showed an excellent function outcome and MSTS scores.^7,9 Moreover, the long-time survival rates of musculoskeletal sarcomas managed with limb salvage procedures is comparable to that with amputations.^10,11

Despite the obvious advantages they offer, salvage procedures do tend to cause infection, thrombosis, neuro-vascular deficit, stress fractures and knee or ankle pain.^12,13 The viability of the graft highly depends on the integrity of the anastomosis. The incidence of stress fractures is 7.7–22.2 %.¹⁰ Delayed weight bearing can prevent/lower the risk but the native healing potential of the vascularized fibula alleviates the need for any further intervention.

5 Conclusion

Benign aggressive and primary malignant tumors of the lower limb pose a great challenge to orthopedic surgeons. Contrary to the earlier trend of amputation, tumor resection and reconstruction with endoprostheses or free vascularized fibula transfer are more popular nowadays owing to the myriad of benefits they offer providing consistently good biomechanical and biological outcomes. Moreover, the native anatomical structure of the bone and joint can be well preserved. Meticulous planning and careful execution of the procedure usually lowers the risk of complications.

Conflict of interest

All authors declare that they have no conflict of interest.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial or not for profit sectors.

Authors’ contribution

All authors read and approved the final manuscript.

Ethical approval

Local ethical committee approval has been taken before surgery.

Guardian consent

Written informed consent from parents has been taken before surgery.