Preoperative templating is a cornerstone of modern arthroplasty planning. It helps anticipate anatomical variation, guides implant selection and positioning, and prevents intraoperative surprises such as limb length discrepancy, instability, or cortical perforation.
Traditional acetate templating with preset magnification (commonly 120%) often leads to magnification errors (actual 109–128%), while digital templating has improved precision and reproducibility.
However, digital 2D methods still rely on accurate radiographic calibration and cannot fully account for 3D bone geometry—especially in complex or dysplastic anatomy.
3D CT-based templating offers superior accuracy and spatial understanding but remains limited by cost, radiation exposure, and logistics. Thus, digital 2D templating remains the gold standard in daily arthroplasty practice, complemented by emerging AI-assisted tools.
Total Hip Arthroplasty (THA)
Preoperative templating in THA is essential for anticipating anatomic and technical challenges such as center of rotation, limb length discrepancy, offset, and acetabular or femoral geometry. Accurate templating guides neck resection level, predicts implant size, and minimizes complications like dislocation, limb inequality, and periprosthetic fracture.
Spot Knowledge
AspectKey PointsTraditional (Acetate) Templating Performed with 120% preset magnification; error-prone (true magnification 109–128%).
Digital 2D Templating More precise, faster, permanent record; depends on proper calibration.
3D CT-Based Templating Offers superior anatomical visualization and 86–94% implant prediction accuracy but limited by cost, radiation, and logistics.
Calibration Marker (ECM)Must be placed at hip center level; misplacement (too anterior/lateral) distorts scaling.Institutional ProtocolsStandardized ECM use improves accuracy and reproducibility in templating results.
Common error: placing the calibration ball on the table or thigh — leads to magnification mismatch and oversizing.
Clinical Implications
Standardized radiographic protocols (scaling ball at hip center) enhance reproducibility.
Digital 2D templating remains the current gold standard in daily practice.
3D methods may become routine as low-dose CT and AI-based segmentation evolve.