Surgical Guides for Temporomandibular Joint Ankylosis Surgery

Use of 3D printing is increasing in the field of medicine. It helps in making the surgical procedure more safe and predictable. I used 3D printing for making surgical guides for a patient with temporomandibular joint ankylosis (jaw joint ankylosis). This disease is characterised by formation of bone between the skull base and jaw joint leading to inability to open the mouth. The patient was a 20 year old female with the inability to open mouth since 5 years.

Requirements: 1.Non-contrast enhanced Computed Tomogram of the face.

2.Materialise MIMICS® medical 17.0 software

3.3D printer and ABS or PLA material

4.Petroleum Jelly

5.Self polymerising polymethyl methacrylate resin(biocompatible)

6.Sterilizer( preferably plasma based for sterilizing the guide)

Step 1: Obtain CT Scan

A non contrast enhanced computed tomogram of the face was obtained with a slice thickness of 0.6mm and inter-slice thickness of 0.6mm. The data is obtained in DICOM format.

Step 2: Creation of 3D Reformated Image

The DICOM data is imported into the Materialise MIMICS® software. The thresholding of the data is done to segment the bone tissue from the soft tissue. The lower threshold value was 1250 (Gray Value) and the higher threshold value was 4095 (Gray value).

After segmentation, a 3D image was generated by calculating 3D volume of the mask.

Step 3: Marking Cutting Planes

The cuts for the bone removal are marked on the coronal sections of the CT scan. The cuts are marked such that it is well away from the skull base and the mandibular foramen. This is to prevent any injury to the skull and brain during the surgery. The same thing is done on the left and right jaw joints.

The cutting planes are than exported as *.stl files and than imported again into the software.

Step 4: Merging the 3d Reformated Object and Imported Cutting Planes

The 3 D image and the imported cutting planes are merged together to obtain 1 single object.

Step 5: 3d Printing of Model

The merged object is than exported as *.stl file and 3D printed..

Step 6: Making Surgical Guides

The surface between the cutting planes is smeared with a layer of petroleum jelly.

The self polymerising methyl methacrylate resin is mixed in correct proportion and placed between the cutting planes and contoured with a sharp instrument (knife).