Preoperative Templating in Orthopaedics

Introduction

• Rockwood and Green's Fractures in Adults, 10th Ed 2025, p. 510
• Campbell's Operative Orthopaedics, 15th Ed 2026, p. 253

Objectives / Importance of Preoperative Templating

1. Implant selection - Determines the correct size, type, and configuration of the implant in advance.
2. Predicting bone cuts - Establishes the level of osteotomy or bone resection preoperatively.
3. Restoring anatomy - Facilitates restoration of limb length, offset, and joint mechanics.
4. Instrument preparation - Allows the scrub team and OT to stock specific implants and instruments.
5. Reduces operative time - Less intraoperative trial-and-error.
6. Cost efficiency - Minimises waste of unused implant inventory.
7. Training tool - Comparing the preoperative template with postoperative radiographs is a valuable learning exercise throughout a surgical career.
8. Patient safety - Anticipates challenges (e.g., poor bone stock, deformity) that might change the surgical approach.

Radiographic Prerequisites

• True AP and lateral views of the affected region; in hip surgery - a full AP pelvis including both hips and upper femora.
• 15 degrees of internal rotation of the hip to accurately display femoral geometry and offset (external rotation underestimates offset).
• Calibration/magnification marker - A lead sphere marker (spheres 100 mm apart) is taped to the thigh at the same depth as the bone and imaged alongside it. The measured distance between sphere centres allows calculation of magnification (typically ~20% on a standard pelvic radiograph).
• Contralateral limb - The uninjured side serves as the anatomical template for the injured side; imaging both sides is recommended.
• For complex fractures: thin-cut CT with coronal/sagittal reconstructions and 3D rendering are invaluable.

Types of Templating

1. Conventional (Acetate) Templating

1. Trace the outline of the uninjured (contralateral) bone in the chosen plane of reference.
2. Trace the injured side separately.
3. Invert the intact-side outline and superimpose it over the fracture outline; move it to sequentially position each fracture fragment where it should ultimately lie.
4. The complete tracing includes all fracture pieces assembled in the desired final result.
5. Working backward ("reverse planning"), superimpose K-wire and final implant outlines to develop the fixation plan.
6. Record the level of planned bone cuts and distances from bony landmarks (e.g., distance of neck cut above lesser trochanter).

1. Template the acetabular component first - the medial border sits at the radiographic teardrop; inferior border at the obturator foramen. Select the size that matches acetabular contour without excessive subchondral bone removal. Mark the new centre of rotation.
2. Template the femoral component - select the size that most completely fills the proximal femoral canal, with allowance for desired cement mantle thickness.
3. Select neck length to restore limb length and femoral offset. If limb shortening exists, the head-to-acetabular centre distance on the template should equal the measured shortening.
4. Mark the planned neck resection level and measure its distance above the lesser trochanter for intraoperative reference.
5. Confirm the plan on the lateral view.

2. Digital Templating

• Specialised software - commercially available packages that may be integrated into a PACS (Picture Archiving and Communication System) or acquired as a separate module.
• A digital library of implant templates supplied by the manufacturer at precise magnification levels.
• Calibration: a magnification marker of known size placed at the level of the joint during imaging. The software calibrates the image, and digital templates are scaled accordingly. Standard magnification of 20% may be assumed; studies show this does not reduce accuracy compared to using a physical marker.

• Eliminates cost of printing films
• Permanent, accessible archive of the preoperative plan
• Templates can be rescaled instantly
• Accuracy not affected by patient BMI for either femoral or acetabular sizing
• Facilitates communication (can be shared electronically with the team)

3. 3D Model-Based Templating (Additive Manufacturing / 3D Printing)

• A 3D-printed model is fabricated from the patient's CT data using additive manufacturing techniques.
• The model is placed in a sterile transparent bag and studied intraoperatively.
• "Practice surgery" can be performed on the model preoperatively to establish reduction and fixation sequences, determine plate and screw lengths and trajectories, and pre-contour implants.
• Pre-bent or pre-contoured plates from the practice surgery are then sterilised for use in the actual procedure.
• Liu et al. described its use in complex T-type acetabular fractures; You et al. demonstrated reduced surgical time, blood loss, and fluoroscopy time in proximal humeral fractures using 3D-printed models vs. CT-only planning.

4. Plastic Model Templating (Pelvis Model Technique)

• Fracture lines (black)
• Planned plate placement (blue)
• Posterior column screws (green)
• Sacroiliac screws (orange)
• Proposed clamp placement sites (red dots)

Measuring Limb Length Discrepancy During Templating

• Draw a horizontal reference line at the level of the ischial tuberosities or the inferior edge of the acetabular teardrops (interteardrop line - more accurate per Meerman et al.).
• Draw perpendicular lines to the proximal corner of each lesser trochanter.
• The difference between the two perpendicular measurements = limb length discrepancy.
• The neck length of the femoral prosthesis is then chosen to correct this discrepancy.

Applications of Preoperative Templating

Pitfalls and Errors in Templating

1. Magnification error - Failure to apply/use a magnification marker leads to size miscalculation; always calibrate.
2. Rotation error - Hip not in standard internal rotation: offset underestimated; flexion/extension errors on lateral view.
3. Poor-quality radiographs - Motion blur, inadequate exposure, or non-standard positioning invalidate the template.
4. Ignoring soft tissue defects - Templating purely bony anatomy may underestimate the need for alternative approaches.
5. Overlooking contralateral pathology - Degenerative changes on the "reference" side may distort measurements.
6. Failure to compare template with postoperative XR - Misses opportunity for learning and quality improvement.

Preoperative Plan Components (Comprehensive)

1. Patient optimisation (medical comorbidities, bone quality, nutritional status)
2. Soft tissue assessment (wound status, vascular injury, contamination)
3. Surgical approach choice
4. Reduction strategy (direct vs. indirect; absolute vs. relative stability)
5. Templating for implant selection and sizing
6. Instrument checklist
7. Contingency planning (if primary plan fails intraoperatively)
8. Postoperative rehabilitation protocol

Summary

• Rockwood and Green's Fractures in Adults, 10th Ed 2025 - Chapter 13: Templating in Preoperative Planning (pp. 510-517)
• Campbell's Operative Orthopaedics, 15th Ed 2026 - Technique 4.1 (Capello), preoperative radiographic evaluation and templating (pp. 250-254)