Customized iliac prosthesis for reconstruction in giant cell tumour: A unique treatment approach

Abstract

Giant cell tumour (GCT) of flat bones of pelvis is extremely rare. GCT of the ilium and ischium represent less than 0.05% of all GCT. Iliac bone GCT has been treated traditionally by intra-lesion curettage with bone grafting, wide resection with or without reconstruction and hemi-pelvectomy in very aggressive tumours. None of the above treatments were without morbidities. Reconstruction using bone grafts and bone cement has also been inadequate. In GCT, where life expectancy is not decreased significantly, surgical treatment should be aimed at giving optimum functional outcome. We are reporting here a rare case of giant cell tumour of ilium bone in a 25-year-old female and its unique treatment approach. We designed a computed tomography (CT) based customized iliac prosthesis using Materialise Mimics and 3-Matic software. 3D model of pelvis was generated from the CT. After deciding the extent of resection on affected side, we virtually mirrored an identical portion of opposite ilium to the affected side. Connecting plates were made over the mirrored part and merged with it. Multiple relevant holes were made to attach various muscles to the prosthesis. Prosthesis was made in medical grade titanium by using Computerized Numerical Control (CNC) machine. The method is called as computer based subtractive manufacturing. Wide resection was done and the prosthesis was placed using multiple 3.5 millimetres screws through the connecting plates. Muscles were stitched to relevant holes using ethibond suture. Post-operative course was unremarkable. Patient was made to walk with full weight bearing after 5 weeks. Powers of abductors at 6 months is 4/5 and patient walks normally without a limp.

1. Introduction

Giant cell tumour of flat bones of pelvis is extremely rare. GCT of the ilium and ischium represent less than 0.05% of all GCTs. Iliac bone tumour has been traditionally managed by wide excision without reconstruction. This is more so in malignant tumours of iliac bone. Reconstruction using bone grafts and bone cement has also been inadequate. In GCT, where life expectancy is not decreased significantly, surgical treatment should be aimed at giving optimum functional outcome. We present here a case in which the iliac bone has been virtually designed for the patient in question in order to achieve a near normal outcome.

2. Case report

A 25-year-old female presented with complaints of dull aching pain and a gradually progressive lump in right iliac fossa associated with difficulty in walking since 8 months. The pain was continuous, diffuse, dull aching with no radiation. There was no history of fever, loss of weight, loss of appetite, night cries, vomiting, loose stools, constipation or abdominal injury.

General physical examination was normal and local examination revealed a firm, tender, non-mobile swelling with smooth margins arising from anterior part of ilium bone. There was no evidence of redness, rise in temperature or dilated veins over the swelling. Systemic examination and haematological investigations were normal.

X-ray pelvis revealed a large lytic expansile lesion involving right ilium bone with evident destruction and well defined margins (Fig. 1). Rest of the pelvic bones appeared normal. The serum calcium, serum phosphorus, alkaline phosphatase and parathormone were normal. X-ray of the chest was unremarkable.

Fig. 1.

Pre-operative X-ray pelvis – antero-posterior view.

Computed tomography (CT) scan of pelvis revealed an expansile lytic lesion involving the right iliac wing. There was no matrix calcification. Magnetic resonance imaging (MRI) showed large lesion in anterior part of iliac wing which was hypointense on T1 and heterogeneously hyperintense on T2 weighted images (Fig. 2).

Fig. 2.

MRI images showing lesion in right ilium bone.

Clinico-radiological work-up was suggestive of GCT of the right iliac bone, which was confirmed on histopathology. It was further classified as type I tumour based on location according to classification system for pelvic tumours by Enneking and Dunham, further modified by Sanjay et al. and grade II according to radiographical classification system of Campanacci.

Wide resection of tumour was done and removed portion of ilium was replaced by a CT based customized patient-specific titanium iliac prosthesis designed using Materialise Mimics and 3-Matic software.

Steps of designing the customized iliac prosthesis are described below.

• 1.A non-contrast computed tomography (NCCT) scan of pelvis with 1 mm cuts was performed and obtained in a compact disc (CD).
• 2.The NCCT pelvis was imported in the Materialise MIMICS software which serves to convert DICOM images of NCCT into 3D model in STL format.
• 3.A virtual 3-D model of pelvis (STL format) was generated using thresholding, region growing and calculate 3-D commands (Fig. 3).
• 4.The STL file of 3-D model was imported to 3-Matic software which allows engineering on 3-D models.
• 5.After planning the extent of resection, appropriate cuts were made on the affected side ensuring complete removal of tumour with a safe margin. Identical portion was marked from the normal side using wave brush command. This identical normal ilium was mirrored to the affected side (Fig. 4, Fig. 5).
• 6.This normal portion was merged with the rest of pelvis. Plates were designed over it to form attachments of the prosthesis. These plates were then merged with the mirrored portion of ilium (Fig. 6, Fig. 7).
• 7.Multiple relevant holes were made on the iliac crest region, ASIS and AIIS to stitch back muscles attached to the bone normally.
• 8.This virtual Iliac prosthesis was then exported in IGS format.
• 9.Real prosthesis was made in medical grade titanium from virtual model by using computerized numerical control (CNC) machine. The method is called as computer based subtractive manufacturing. Subtractive manufacturing is a process by which 3D objects are constructed by successively cutting material away from a solid block of material (Fig. 9).
• 10.This custom-made iliac prosthesis was then autoclaved.
• 11.After performing wide resection of tumour according to the virtual plan (Fig. 8), the prosthesis was fixed to the pelvis through its attachment plates using 3.5 mm titanium screws (Fig. 10, Fig. 11).
• 12.Muscles were stitched back to the appropriate holes in prosthesis using ethibond number 5 sutures.

Fig. 3.

Virtual 3D model of pelvis made from CT scan.

Fig. 4.

Appropriate cuts made on the affected side and identical portion marked from the normal.

Fig. 5.

Identical portion of normal ilium was mirrored to the affected side.

Fig. 6.

Plates designed to form attachments of the prosthesis.

Fig. 7.

These plates were then merged with the mirrored portion of ilium to form prosthesis.

Fig. 9.

Customized iliac prosthesis made of titanium.

Fig. 8.

Virtual plan.

Fig. 10.

Intra-operative image showing wide resection of tumour according to the virtual plan.

Fig. 11.

Prosthesis fixed to the pelvis through its attachment plates using 3.5 mm titanium screws.

Size of the excised tumour was 10 cm × 8 cm × 6 cm.

Post-operative course was unremarkable. Patient was made to walk with full weight bearing after 6 weeks. Powers of abductors at 6 months is 4/5 and patient walks normally without a limp (Fig. 12).

Fig. 12.

Post-operative X-rays.

3. Discussion

Giant cell tumour of bone is a histologically benign, locally aggressive tumour that typically affects ends of long bones, most commonly involving distal femur, proximal tibia, distal radius, and proximal humerus in order of frequency. It represents 5% of neoplasms of bones. It rarely affects the pelvis, with an incidence of only 1.5–6.1% of bone GCTs.¹ GCT of the ilium and ischium represent less than 0.05% of all GCTs.² Ilium is the most common bone involved in pelvis (excluding sacrum).³ GCT of pelvic bone mostly occurs in third or fourth decade of life with a clear female predilection.⁴ In a series of 70 giant cell tumours by Shankman et al.,³ only two occurred in ischium, two occurred in ilium and none in the pubis. Balke et al.,⁵ in their case series of 20 patients of giant cell tumours of pelvic bone over a period of 20 years found nine cases involving the ilium.

Giant cell tumour of bone is characterized radiographically as an expansile lytic lesion with well-defined margins. It may extend beyond the cortex. Most tumours demonstrate absence of a sclerotic border (unless the tumour has been presented for a long time), a lack of periosteal reaction, and the absence of calcified matrix.³ Computed tomography is the best modality to show the expansile nature of the tumour, while magnetic resonance imaging scan is superior in showing the soft tissue extension.⁶

There is still no widely held consensus on ideal treatment for pelvic giant cell tumours owing to their infrequent occurrence. Treatment options include denosumab, serial embolization, interferon, radiation therapy, and intra-lesional curettage or wide resection.⁷ Radiotherapy has high rate of recurrence (44%) and risk of soft tissue sarcomas (12%). Thus treatment is essentially surgical. Strengths of intra-lesional curettage include preservation of pelvic integrity, but it is also deemed to increase the risk of local recurrence, especially for aggressive benign tumors.⁷ The adjuvant therapy used along with curettage are cryotherapy, phenol, or polymethylmethacrylate (PMMA) to minimize the incidence of recurrence.⁶

Reconstruction of pelvic ring after iliac resection using fibular autograft and bone allograft has been described.⁸ Porsch et al.⁸ reported worst functional outcome and poor stability after pelvic resection for ewing's sarcoma in a case without reconstruction of pelvic ring in comparison to pelvic reconstruction resulting in cranial migration of acetabulum necessitating revision surgery for reconstruction of pelvic ring using fibular graft 5 years after primary surgery. Zheng et al.⁷ described wide ilium resection without reconstruction for pelvic giant cell tumour in 5 patients and with pelvic ring reconstruction using screws, titanium rods, and bone cement in 3 patients. Mathur et al.⁶ described an unusual case of histologically benign GCT of ilium distinguished by marked destructive features, necessitating hemi-pelvectomy.

Although various hip replacement prosthesis like saddle prosthesis⁹ (Kitagawa et al.) and iliac stem acetabular prosthesis¹⁰ (De Paolis et al.) are reported for reconstruction after resection involving acetabulum and peri-acetabular region, to the best of our knowledge, till date, there is no case reported where customized iliac prosthesis has been used for reconstruction in GCT of ilium.

The described configuration can be compared to a sailing ship in which there is one or several guyed masts, made of wood, aluminium or steel, staying erect near the centre of the ship with anchoring cables. A guyed mast is a tall thin vertical structure that depends on guy lines for stability. The mast itself has the compressive strength to support its own weight, but usually does not have the shear strength to stand unsupported, and requires guy lines, diagonal tensioned cables at equal angles about its base, to resist lateral forces such as wind load and keep it upright. Similarly, in our case the prosthesis was designed with appropriate holes at the site of attachments of muscles to which the muscles were anchored using ethibond no. 5.

Merits of such prosthesis are

• 1.It closely mimicked the actual anatomical configuration.
• 2.Nearly no dead space was left after reconstruction. It gave a good cosmetic results as there was no depression that could be seen or felt in the iliac region.
• 3.Muscles were sutured back to the prosthesis in relatively similar arrangement considering their anatomic origins and insertions, which provided a better stability and function of the muscles.
• 4.Since the age of patient is 25 years, there was less chance of bone grafts to remodel into near anatomic configuration if we had used bone grafts for reconstruction.

Conflicts of interest

The authors have none to declare.