This post is for orthopaedic surgeons who run a practice, and for the marketing or video teams that work with them. It walks through the production of a knee replacement explainer from a CT scan to a vertical reel: what to export, how to remove identifying data, how to build the bone models, how to animate, and where the surgeon must sign off. It also deals with the question that decides whether you should use a real scan at all, which is consent under India's Digital Personal Data Protection Act, 2023.
Surgical animation is one of the few formats where a clinician can explain a procedure visually without showing an operating theatre. It suits the questions patients ask before an operation: what is being replaced, what happens during surgery, and what recovery involves. It is also easy to get wrong, in clinical accuracy, in privacy and in promotional tone. The steps below are designed to keep all three under control. Nothing here is clinical advice; the surgeon must review every frame and every line of narration.
Step 0: Decide whether you need a real patient's scan
A bone model for a marketing explainer does not need to be a specific person's knee. The video is illustrative. Using a real scan adds personal data, consent obligations and a withdrawal risk for no educational gain in most cases.
You have three options:
- A licensed or purchased anatomical model. Lowest risk. The detail is generic, which is appropriate for an explainer.
- A model built from a scan of a consenting adult who is not a patient of the practice, such as a volunteer. Consent still applies.
- A model built from a patient's scan. Highest risk and highest effort. Use it only when the case is the point of the video.
Choose option 1 unless there is a clear reason not to. The rest of this post covers option 3 because it has the most steps, and the steps up to segmentation apply to option 2 as well.
Consent under the DPDP Act
A scan is personal data, and health data is exactly what patients expect to be handled carefully. The Act, which you can read through MeitY's data protection framework page, requires consent that is free, specific, informed, unconditional and unambiguous, given by a clear affirmative action, and withdrawable as easily as it was given. Several of the Rules that operationalise this phase in over time, so confirm current commencement with your counsel; design to the standard anyway.
For a marketing animation, that means:
- Separate the consent from treatment. Care must not depend on the patient agreeing to appear in marketing. Bundling it into the admission form fails the "free" and "unconditional" tests.
- Be specific about use. Say that the scan will be used to build an illustrative 3D model for educational videos on the practice's channels, and for how long the source data will be kept.
- Explain withdrawal. A model already published in a video cannot be un-published from the internet. Tell the patient what you can do (remove it from your channels, stop further use) and what you cannot.
- Keep a record. Store the consent, its date and wording against a pseudonymous reference, not the name.
- Minimise. Delete the original DICOM copy from the production workspace once the meshes are approved, if the patient's consent says so.
The doctors' advertising rules are a separate layer. The National Medical Commission's rules on professional conduct and advertising affect how a surgeon may present themselves and the practice; our 2026 compliance handbook explains them. Have compliance read the final cut.
Step 1: Export from the PACS
Ask radiology to export the knee CT as DICOM files in a folder or on media, with the thin-slice bone series if the protocol has one. Request only the series you need: not the localiser images, not the dose report, not any secondary captures. Every extra object is another place where a name or number can hide.
Step 2: De-identify the DICOM
The DICOM standard describes de-identification in PS3.15, Annex E, with a basic profile and options. You do not need to read all of it, but your tool and your checklist should cover the following.
Header attributes to remove or replace:
| Attribute | Tag |
|---|---|
| Patient's Name | (0010,0010) |
| Patient ID | (0010,0020) |
| Patient's Birth Date | (0010,0030) |
| Institution Name | (0008,0080) |
| Referring Physician's Name | (0008,0090) |
| Accession Number | (0008,0050) |
| Study, series and acquisition dates | (0008,0020) and related |
| Private tags and UIDs | Remove or regenerate |
Pixel data: Identifying text can be burned into the image itself. The standard expects the de-identifier to ensure that no identifying information is burned into the pixels, either because the modality never does it or by removing it using the Clean Pixel Data option, and it sets the Burned In Annotation attribute (0028,0301) to NO afterwards. CT knee series rarely carry burned-in text, but scouts and secondary captures sometimes do. Open a sample of images, including the first and last of each series, and look.
Check the output, not just the settings: dump the headers of the de-identified files and search for the patient's name, hospital name and ID. Two people should sign the check, one from the clinic and one from production. Keep a log of who handled the files and when.
If the model is of a head or face, surface reconstructions can identify a person. This is not a concern for a knee, but it is for any other region you may animate later.
Step 3: Segment the bones
Load the cleaned series into an open-source segmentation tool such as 3D Slicer. Bone is dense on CT, so a threshold on Hounsfield units separates it from soft tissue. In practice:
- Threshold the volume to isolate bone.
- Split the result into femur, tibia, patella and fibula using region-growing or paint-and-erase tools. Joint surfaces are close together, and automatic splits often merge them.
- Smooth lightly to reduce staircase artefacts from the slice thickness, but keep the joint surface shape.
- Export each bone as a mesh file.
- Reduce polygon counts so the animation software can handle the scene.
CT does not show cartilage, ligaments or tendons well. These must be modelled by an artist from anatomical references, or taken from a licensed model. Say in the video that the visual is illustrative.
Step 4: Implants and instruments
Show a generic implant unless the practice has permission to depict a specific manufacturer's design. Manufacturer CAD files usually come with licence terms, and showing a brand in a promotional video may create claims you cannot support. If your surgeon uses a particular system and wants to show it, get written permission and have compliance review how the brand appears.
