2D Templating vs 3D AI Planning: When Each Wins
A practical comparison of 2D digital templating and 3D AI-based preoperative planning in orthopaedics, accuracy, speed, cost, imaging dose, and the cases where each is the right choice.
TL;DR
2D templating is fast, cheap, low-dose (radiograph-based), and adequate for straightforward primary cases. 3D AI planning, from CT, is more accurate for sizing, alignment, and complex anatomy, at the cost of CT dose and a heavier workflow. The right answer is not one or the other: use 2D as the everyday gateway and escalate to 3D when case complexity or sizing stakes justify it. The mistake is forcing every case into one approach.
Two Tools, Different Jobs
Digital 2D templating overlays a calibrated template on a radiograph to estimate implant size and position. It is quick and inexpensive, and for a clean primary hip or knee with good films, it is often enough.
3D AI planning starts from CT, builds a patient-specific 3D model, and plans sizing, alignment, and positioning in three dimensions. It captures what 2D cannot: version, true offset, and complex deformity.
The Comparison
| Dimension | 2D templating | 3D AI planning |
|---|---|---|
| Imaging | Radiograph | CT |
| Dose | Low | Higher (CT) |
| Speed | Fast | Minutes (AI) + review |
| Cost | Low | Moderate |
| Sizing accuracy | Good for simple cases | Higher, especially complex |
| Captures version/3D offset | No | Yes |
| Best for | Straightforward primaries | Complex, revision, deformity |
Where 2D Still Wins
- Routine primaries with good-quality radiographs.
- Dose-sensitive patients where avoiding CT matters.
- Speed and cost when 3D adds little for a simple case.
2D templating is not obsolete. For a large share of everyday cases it is the proportionate tool, and it remains the practical gateway most surgeons reach for first.
Where 3D AI Earns the CT
- Sizing certainty. For hip, AI 3D planning predicts implant size markedly better than 2D.
- Alignment and deformity. Osteotomy planning needs precise mechanical-axis angles, which 3D measures reproducibly.
- Complex and revision cases. Where anatomy is distorted or bone stock is in question, 3D removes guesswork.
- Version-sensitive joints (hip, shoulder) where 2D simply cannot see the third dimension.
The Gateway Model
The most workable strategy treats 2D templating as the entry point and 3D AI planning as the escalation: start 2D, move to 3D when the case earns it. AI is what makes that escalation affordable, by collapsing the hours of manual 3D segmentation into minutes, it removes the cost barrier that used to make 3D a specialist-only tool.
FAQ
Is 3D planning always better than 2D? No. For straightforward primaries with good radiographs, 2D is faster, cheaper, and lower-dose. 3D wins on complex, revision, deformity, and version-sensitive cases.
Does 3D planning always need a CT? Yes, 3D AI planning is CT-based. That dose is the main reason to reserve it for cases where the added accuracy matters.
What makes 3D planning affordable now? AI segmentation. It turns hours of manual 3D modelling into minutes, removing the cost barrier.
The Takeaway
Match the tool to the case: 2D for the everyday gateway, 3D AI when complexity or sizing stakes justify the CT. The smartest workflow uses both, and lets AI make the 3D step cheap enough to escalate without hesitation.
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Disclaimer: This article is for educational and research purposes only. Salnus tools are designated for Research Use Only (RUO) and are not cleared medical devices. Clinical decisions should be made by qualified physicians.
References:
- Reliable prediction of implant size in AI-based 3D preoperative planning. PMC, 2024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11266554/
- 3D preoperative planning improves precision of orthopaedic surgeries. Int J Surg, 2023.
Reviewed by the Salnus biomedical engineering team.