A Belgian girl suffered from hemifacial microsomia, a birth defect usually affecting the development of one half of the face and the second most common birth deformity in the craniofacial area. Professor Mommaerts from the European Face Centre was involved since the early stages of her treatment. After a series of corrective surgeries, a complex jaw angle reconstruction was planned with Materialise’s PROPLAN CMF and 3-matic software.

A History of Pre-Planned Corrective Surgeries

L-10193 revision 1 ProPlan 3-matic Mommaerts

Hemifacial microsomia is characterized by abnormal development in structures derived from the first and second branchial arches. This results in unilateral hypoplasia and asymmetry of the orbit, mandible, ear, facial nerve and overlying tissue with variable degrees of clinical manifestation. In this case, the girl’s right ear was also missing. At the age of four she received a costochondral graft to create a functional and abutting joint to prepare her for a facial rotation procedure 10 years later. The doctors used a calvarial graft to reconstruct the zygomatic arch and repositioned the fossa to align with the contralateral joint position. This may stimulate some growth, but a facial rotation is always necessary and planned at the end of the secondary growth spurt. Therefore, at the age of 15, the patient underwent “trimaxillary” orthofacial surgery to rotate and advance the facial complex.

Reconstructing the Jaw Angle Defect with PROPLAN CMF® and 3-matic®

The remaining jaw angle defect could not be addressed by skeletal surgery. Therefore, the surgical team considered to reconstruct the bony jaw angle using a CAD-CAM patient- specific implant or to augment it with hydroxyapatite/fibrin glue or an onlay with a silicone or polyethylene implant. The angle needed significant posterior augmentation, which is not possible with a hydroxyapatite/fibrin glue mixture. Polyethylene has a reputation of infectious complications and detachment of the pterygomasseteric sling.

L-10193 revision 1 ProPlan 3-maticMommaerts_Page_1_Image_0002_0.jpg

First, the team created a 3D model of the skull from a CT scan in Materialise’s PROPLAN CMF software and segmented it in the Segmentation Wizard. Second, they exported the 3D STL file of the skull into Materialise’s 3-matic software package. To rapidly gain insight in the extent of the defect, the team mirrored the healthy side which provided a basis for the implant design. Due to asymmetrical growth of the unaffected side, it was not straightforward to determine the midline. Using the Global Registration tool, the software determined the best overlapping fit of the mirrored and original side of the skull. With a Boolean Union, the mirrored and original part were merged into one object. Subsequently, the gap between the mirrored and original skull was filled with the Push and Pull tool and a wrap was performed. In addition, a trimming operation was carried out to proceed towards shaping the implant.

 

“The software opens up a whole new world of infinite possibilities where you can reconstruct and build a face like never before. Having a predictable outcome is most desirable when aiming for an aesthetically-pleasing result.”
Lauri Wauters, MSc, European Face Centre

L-10193 revision 1 ProPlan 3-maticMommaerts_Page_2_Image_0001.jpg

Surgical Planning for an Unambiguous Fit

Even when you’re planning a surgery in 3D, surgical insight in the procedure remains crucial to foresee potential pitfalls. In this case, the scarred fibrous tissue was not as elastic as unscathed soft tissue, which could make inserting the voluminous implant very difficult. Reducing the implant volume would imply losing the symmetry that was created during the mirroring exercise. An even bigger problem was the aberrant anatomy of the patient’s facial nerve. To tackle these problems, the team rounded the implant to slightly reduce the volume in the upper mandibular ramus area, using 3-matic’s Trimming and Local Smoothing tool. Next, they virtually fitted the implant on the skull and positioned screw holes, taking into account the inferior alveolar nerve position.

 

L-10193 revision 1 ProPlan 3-maticMommaerts

The final STL files of the implant were exported for 3D Printing in implantable titanium and transorally inserted for an unambiguous fit, greatly saving operation time. Thanks to the pre-planned placement of screws, nerve damage was avoided.

The bone defect was surgically reconstructed. Follow-up sugery on the now-16-year-old girl is still required to reconstruct the missing ear and soft tissue touch-ups (correction of microstomia and microlipofilling of the temporolateral fat pad) are needed, but the end of her long journey of reconstructive surgeries is in sight.

The Standard in ‘Engineering on AnatomyTM

The Mimics Innovation Suite turns 3D image data into high quality digital models in an accurate and efficient way. Starting from CT, MRI or 3D ultrasound images, the Mimics Innovation Suite offers the most advanced image segmentation, the broadest anatomical measurement options, powerful CAD tools for Engineering on Anatomy and 3D Printing, and accurate model preparation for FEA and CFD. In this case, PROPLAN CMF and the medical edition of the Mimics Innovation Suite were used to:

  • Create an accurate 3D reconstruction of the defect
  • Mirror the healthy side of the patient’s anatomy and use it as a reference for reconstructive surgery
  • Design an implant directly on the patient’s anatomy, ensuring an optimal fit
  • Export the design for 3D Printing in titanium

Regulatory Information:

The Medical edition of the Mimics® Innovation Suite currently consists of the following software components: Mimics® Medical version 18.0 and 3-matic® Medical version 10.0 (released 2015). Mimics® Medical is intended for use as a software interface and image segmentation system for the transfer of imaging information from a medical scanner such as a CT scanner or a Magnetic Resonance Imaging scanner. It is also used as pre-operative software for simulating / evaluating surgical treatment options. 3-matic® Medical is intended for use as software for computer assisted design and manufacturing of medical exo- and endo-prostheses, patient-specific medical and dental/orthodontic accessories and dental restorations.

PROPLAN CMF Software is intended for use as a software interface and image segmentation system for the transfer of imaging information from a medical scanner such as a CT or MRI scanner.  It is also used as pre-operative software for simulating/evaluating implant placement and surgical treatment options.

Materialise Belgium – Technologielaan 15 – 3000 Leuven – Belgium

jpg_CE-0120.jpgMimics Medical, 3-matic Medical and PROPLAN CMF are CE-marked products. Copyright 2015 Materialise N.V. – L-10193 revision 3, 05/2015

Contact: mimics@materialise.be or materialise.com