Keywords calcaneum - giant cell tumors - oncology - printing, three-dimensional
Palavras-chave calcâneo - impressão tridimensional - oncologia - tumores de células gigantes
Introduction
Advances in image processing have led to an increasing clinical usage of 3D printing
technology. The CT or MR images can be converted to 3D format files, giving a perfect
anatomical model. This technology allows versatility in the design process and enables
efficient production of both off-the-shelf and personalized anatomy that tailors to
specificity.[1 ] In the field of orthopaedic oncology surgery, 3D-printed molds and instrumentation
can be used to address bony restoration after a wide resection as part of tumor resection
protocol. Although conventional metal implant replacements are available, costs can
be exorbitant. In our case, the 3D anatomical shell is printed at minimal cost, and
the bone cement used to fill it is also low in cost. This paper reviews the surgical
technique and outlines the basics of 3D printing technology and its possible applications
in orthopaedic surgery with its potential future impact.
Case Report
This innovative surgical treatment was performed on a patient who presented to our
institution with a recurrent GCT of the calcaneum. The patient was initially treated
18 months prior with a series of Denosumab and an extended curettage. He presented
with symptoms of swelling and pain over the left heel ([Figs. 1 ] and [2 ]).
Fig. 1 Radiograph imaging of the L pathological calcaneum in (A ) AP view (B ) axial (C ) lateral.
Fig. 2 Clinical picture of the left pathological foot.
Technique Description 3D Printing
Various methods of 3D printing exists, however all of them share the same principles
and step-wise process.[1 ] Although 3D printing has gained traction over the years, it is not widespread given
its steep learning curve and limited knowledge.[2 ] As the case was an oncological pathology – it is crucial that the high standards
of oncological resection principles are upheld. Patient will have to go through the
same standard clinical assessment with proper imaging: A CT scan and an MRI of the
foot to delineate the soft tissue extension and neurovascular involvement. Once the
diagnosis is established the surgical resection margins are determined: an anticipation
of a significant void as a total calcanectomy was planned. The resected calcaneum
will need to be replaced or reconstructed to facilitate weight bearing. A CT of the
normal contralateral calcaneum was needed for the mold creation.
A standard 3D printer was required. Examples were by Kokoni Smart, Bambulab, Creality
and etc. A prior CT scan and MRI was required to obtain the 3D models. These 3D models
were generated from Slicer (slicer.org) and then imported into a 3D modeling software
(Fusion 360) ([Fig. 3 ]). The final designs can be printed using several printer-specific software. The
model of the anatomical printing needs to be prepared prior to surgery and sterilized
– the 3D model was sterilized with gas sterilisation as the PLA (Polylactic Acid)
material used was heat labile.
Fig. 3 (A ) The creation of the 3D model from existing 3D reconstruction of the CT (B ) superior view of the created halve of the calcaneum (C ) the sagittal view of the created half of the calcaneum (D ) creating a mirror image for printing (E ) the final designs for printing in a 3D printer platform.
This method of replacement follows a wide local excision of the underlying tumor avoiding
the need for an amputation. Limb salvage surgery comprises surgical techniques designed
to resect musculoskeletal extremity tumors and subsequently reconstruct a limb with
an acceptable oncologic, functional, and cosmetic result.[3 ] Relative contraindications are pathologic fractures, neurovascular encasement, and
a poorly placed biopsy tract. Limb salvage surgery is the preferred treatment of musculoskeletal
extremity tumors in the modern era because limb salvage surgery has proven not to
compromise survival or recurrence when compared with amputation.[3 ]
The calcaneus is an irregular, roughly cuboidal bone situated below the talus forming
the core of the heel ([Fig. 4 ]).[4 ] The posterior part of the calcaneus is circular, with three facets. The superior
facet is separated from the calcaneal tendon by the retrocalcaneal bursa. The middle
facet provides the attachment site for the Achilles tendon. The inferior facet is
continuous with calcaneal tuberosity on the plantar surface. Superiorly is a cartilage-covered
facet (middle talar articular facet) for the corresponding middle facet of the head
of talus as part of the subtalar joint. The anterior surface has a convex articular
facet for the cuboid bone articulation.
Fig. 4 Anatomy of calcaneum (A ) medial (B ) lateral (C ) inferior. Source: Luijkx T, Elthokapy M, Gregory L, et al. Calcaneus. Reference
article, Radiopaedia.org.
All patients will adhere to strict oncological resection principle of an en bloc resection
with a clear resection margin. Surgical resection is crucial in the treatment of primary
solid tumors, resection at tumor margins remains a concern, inadequately resected
margins facilitating tumor recurrence.[5 ] Post excision of the tumor – ensure no macroscopic retainment of tumor. The operation
was performed in the prone position using a Cincinnati incision[6 ] ([Fig. 5 ]). The total calcanectomy was performed, via en bloc resection ([Fig. 5 ]). The triceps surae were tagged for reconstruction later.
Fig. 5 Total calcanectomy with Cincinati approach to the calcaneum (A ) Cincincati approach incision over the heel (B ) Wide resection of the pathological calcaneum (C ) sagittal view of the pathological calcaneum (D ) Voided space post total calcanectomy (E ) Excised recurrent Giant Cell Tumour of the calcaneus.
The sterilized printed mold is prepared for molding of the calcaneus for implantation.
Each halves of the printed mold was lined with ioban and coated with liquid paraffin
([Fig. 6 ]). Both the molds are then filled with one packet of standard bone cement each. The
2 molds are then clasped together with proline mesh in between. The prolene mesh serves
to function as an anchor for the soft tissue reconstruction. The extruded cement upon
clasping is removed while in liquid form before hardening ([Fig. 6 ]).
Fig. 6 Molding of the prototype calcaneal bone cement model (A ) Mold lining with ioban and liquid paraffin (B ) Both molds are then filled with a packet of standard bone cement each (C ) A sheath of prolene mesh is placed between before clasping both together awaiting
consolidation. (D ) Clasping of both molds with cement and proline mesh while the assistant clears off
the extruded cement. (E ) Peeling the printed mold off the calcaneal cement (F ) The cement calcaneum with the proline mesh incorporated in the center for soft tissue
attachment.
Due to the physical properties of the polylactic acid, the hardened mold shell softens
during the exothermic phase of the cement setting, enabling it to be peeled off easily
([Fig. 6 ]). This molded calcaneum is then inserted to the resected calcaneal space. The Tricep
surae was sutured to the posterior calcaneal aspect of the proline mesh. The proline
mesh was trimmed to areas that required attachments. The Talocalcaneal joint is stabilized
with the insertion of a partially treaded cancellous screws ([Fig. 7 ]). Serial drill bits of increasing sizes were used to gradually dilate the tract
to prevent cement from cracking.
Fig. 7 The calcaneal cement inserted into the resected calcaneal space for reconstruction.
(A ) Posterior view (B ) lateral view Intraoperative Image Intensifier images of both inserted cancellous
screws. (C ) Lateral view (D ) AP view.
Subsequently, after the insertion of the screws, the Tendon Achilles was sutured to
the mesh over the posterior part of the calcaneum with a size 2 Ethibond. The calcaneo-cuboid
joint was reconstructed with the mesh around the joint with its surrounding ligament.
Alternatively – another screw from posteriorly could be inserted across the calcaneocuboid
joint ([Fig. 7 ]).
A drain was applied and the subcutaneous tissue was closed with Vicryl 1 and skin
with Dafilon 3/0. The wound is dressed with antibiotic cream and plaster and supplemented
with fluffed gauze and bandaged.
The drainage tube is kept for 3–5 days till the wound was epithelised. Sutures were
removed 2 weeks post-surgery. A postoperative below-knee dorsal slab was applied for
8 weeks. Subsequently, a progressive passive and active movement of the ankle without
weight for an additional 6 weeks to allow Tendon Achilles to incorporate. Partial
weight-bearing with crutches was allowed at 6 weeks after surgery and full weight-bearing
at 3 months. This patient will be followed up with periodic clinical and radiological
examinations. Functional results were evaluated according to the system proposed by
the International Society of Limb Salvage and approved by the Musculoskeletal Tumor
Society.[7 ]
Patient was followed up post operatively in 2 weeks, 6 weeks, 3 months and 6 months
after. The wound healed well without dehiscence or fat pad necrosis and patient started
full ambulation after 3 months. Patient was able to walk with a fairly balanced gait
and radiograph showed intact printed implant and screws ([Fig. 8 ]). Patient was very satisfied with the result and rehabilitation.
Fig. 8 Clinical picture of (A ) bilateral foot from plantar (B ) lateral view of foot and radiograph of (C ) axial view of calcaneum and (D ) lateral foot radiograph – at 9 months follow up post surgery.
This method of indirect 3D printing can be reproduced and its cost is significantly
less than that of direct metal 3D printing. The printing cost of the mold is minimal.
The bulk of the cost is the bone cement used. This method enables an anatomical fit
with near-physiological force distribution during load bearing, rather than just an
odd shaped cement spacer.
Discussion
A recurrence of a previously treated tumor, being malignant or an aggressive benign
will necessitate a wider and more extensive resection – leaving behind a significant
void. These voids will need to be filled to allow the distribution of forces for load
bearing. The reconstruction requires a thorough 3D preoperative analysis for deformity
or structural replacement, with the aim of restoring the hindfoot alignment allowing
eventual ambulation via full load bearing. This complex void presents significant
challenges, therefore the option of utilizing a 3D printing technology for the replacement
aspect of the surgery. As replacement of the resected calcaneum is secondary, the
primary importance is still maintaining clear margin resection of the recurrent tumor.
Medical 3D printing was first introduced for an evaluation of intraarticular calcaneal
fracture in 1997 by Kacl et al.[8 ] Despite the lapse of many years and the cost of production did reduce, however,
the total cost in printing the entire calcaneum in titanium is still a significant
financial burden to this age.[9 ] 3D printing has evolved over the years enabling pre-operative planning, pre-contouring
plates, pre-shape plates, fabricating patient-specific guides etc.[9 ] Given the complexity of the foot and ankle – this method definitely helped in establishing
a stable fixation and anatomical replacement without significant economical strain.
Final Considerations
This innovative approach not only promises functional recovery but also emphasizes
patient comfort through reduced recovery times and enhanced anatomical fit. This is
an efficient, economical and reproducible method for bony reconstruction after a complete
or partial bony tumor resection. The evidence from a single case may not suffice to
generate a conclusion – requires a series of cases, but this case throws light on
a new novelty method that can be practiced effectively & economically. As this will
set a precedent for future advancements in Orthopedic oncology worldwide especially
in nations with financial constrain over health care.
Bibliographical Record
