Preoperative Planning

Preoperative Planning

Prepared by Dr. Kayahan KARAYTUG

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.

Total Knee Arthroplasty (TKA)

Overview

Digital templating for TKA assists in predicting implant sizes and alignment, aiming to optimize motion and minimize stiffness or loosening. However, its impact on postoperative function and alignment remains limited.

Spot Knowledge

AspectKey Findings

Accuracy :  Predicts component size within one size of the final implant in most cases.

Alignment & Function:  No consistent effect on postoperative alignment, ROM, or PROMs.

Efficiency:  Adds cost and time (software, licensing, training).

Alternatives:  Demographic-based models (height, sex, BMI) predict size equally well.

Clinical Use:  Best suited for inventory and surgical planning, not for outcome prediction.

💡 Tip: Use templating as a preoperative checklist tool, not as a strict sizing determinant.

Clinical Implications

• Digital templating is a useful planning adjunct but not an outcome determinant.
• Demographic prediction models may replace templating in routine TKA workflows.
• Integration with AI-based morphometrics could improve predictive precision.

Clinical Relevance

• Standardized imaging protocols (AP pelvis with centered scaling ball) are essential for reproducible THA planning.
• Digital templating reduces operative time, implant mismatch, and intraoperative guesswork.
• TKA templating, while less predictive of functional outcome, assists in logistics and implant preparation.
• In both THA and TKA, templating accuracy improves with experience, consistent magnification calibration, and software familiarity.
• Emerging AI-assisted 3D templating is likely to redefine precision planning and patient-specific arthroplasty.

💡 Clinical Pearl:
Calibration marker placed at hip joint level (not on the table) prevents oversizing — a small detail that avoids major intraoperative complications.

Common Pitfalls

⚠️ Oversized components due to miscalibrated images → higher fracture risk.
⚠️ Ignoring 3D bone morphology in dysplastic or post-traumatic hips → malposition risk.
⚠️ Excessive reliance on digital software without radiographic standardization → poor reproducibility.

References

1. Kothari M, et al. Digital Templating for Total Hip Arthroplasty: Accuracy and Clinical Relevance. J Arthroplasty. 2023.
2. O’Neill S, et al. Evaluation of Calibration Marker Position in THA Templating. Bone Joint J. 2022;104-B(6):742–749.
3. Sunil T, et al. Digital Templating Accuracy in Total Knee Arthroplasty. Cureus. 2024;16:e48720.
4. MacDessi SJ, et al. 2D vs 3D Preoperative Planning in Arthroplasty. Bone Joint J. 2024.
5. Guyen O, et al. Calibration and Digital Planning in Modern Hip Surgery. J Arthroplasty. 2023.