▼Created by Medical Makers for the Global Surgical Training Challenge.

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This skills module allows medical officers and surgeons who are not orthopedic specialists to become confident and competent in performing bicortical drilling as part of modular external fixation procedures for open tibial shaft fractures performed in regions without specialist coverage.

Learning Objectives

By the end of this module, learners will be able to:

1. Direct an assistant to perform irrigation while the learner is drilling to prevent thermal osteonecrosis
2. Perform bicortical drilling with drill trajectory angles relative to the saggital plane (tibial crest) between 30-60 degrees into the safe zones of the tibia
3. Drill by sound and feel to identify when the drill bit penetrates the near cortex, cancellous bone, far cortex, and the outer layer of the far cortex
4. Adjust drilling direction, speed, and applied force to minimize plunge

To overcome the drawbacks of 3D printed plastic melting at high drilling temperatures, this module trains the learner to irrigate during bicortical drilling, which is a standard orthopedic surgical practice to reduce the risk of thermal osteonecrosis.^[1][2] This provides continuous cooling to prevent melting of the 3D printed plastic bone model.

Materials and Equipment

Tibial Shaft Simulator

The Tibial Shaft Simulator and Clay Backstop for Plunge Depth Measurement will be used in this module.

This Tibial Shaft Simulator uses the 3D Printed Adult Tibial Bone Model #3 which accurately simulates bone length and diameter, external contour, cross-sectional shape, bicortical anatomy, cortical hardness, cancellous bone porosity, and microstructure, and far cortex thickness for non-obese adults at left tibial shaft fracture pin drilling sites for modular external fixation.^{[3][4][5][6][7][8][9][10][11][12]}

• This model features a semi-engraved model number, gender symbol, and drilling direction arrow on the base of the model to assist with model identification and proper orientation.
• The model has a vise attachment to allow the user to secure the model inside a standard vise clamp to maximize safety during simulation training. When a model is placed inside a standard vise clamp, the bone model will be properly positioned to simulate a patient in the supine position.

The Tibial Shaft Simulator teaches bicortical drilling skills useful for modular external fixation and that are transferable to the performance of other limb-saving and life-saving surgeries that require hardware stabilization and fixation.

Learning Bicortical Drilling Step-By-Step

• Irrigation is performed using sterile normal saline during drilling to reduce thermal osteonecrosis.^[2]
• For this simulation training module, the learner will use water as simulated sterile normal saline to perform external irrigation and to also provide continuous cooling to prevent melting of the 3D printed plastic bone models.
• IMPORTANT: Surgical gloves should be worn by the learner during bicortical drilling skills training to simulate intraoperative tactile feedback.^[13]

• Check that the drill bit is sharp before use.^[14][15]
• Adjust operating room table to be at elbow level.
• Direct an assistant to perform irrigation to reduce thermal osteonecrosis.^[16]
• Maintain the drill parallel with your forearm to maintain better control of the drill.
• Hold the drill with your dominant hand and position the drill sleeve with your non-dominant hand. IMPORTANT: Normally, the drill sleeve is positioned directly on the bone. When training on the Tibial Shaft Simulator, hold the drill sleeve 3.0 mm above the bone model to avoid having plastic stands entangled in the drill sleeve.
• Start drilling the hole perpendicular to the bone surface.
• Once penetration starts, re-insert the drill into the initial entry point and adjust to the desired direction.^[14]
• IMPORTANT: The drill trajectory angle relative to the saggital plane (tibial crest) should be between 30-60 degrees to ensure proper insertion of the modular external fixation pin into the safe zones of the tibia.

Oscillogram of Bicortical Drilling of a Tibial Fracture

Play this audio file to identify the acoustic changes of the drill as it progresses through the near cortex, cancellous bone, and the outer layer of the far cortex, and is backed out of the drilled hole.

• The tactile feel of the drill changes as it progresses through the near cortex, cancellous bone, and the outer layer of the far cortex.
• The operator will feel a "give" when the drill passes through the near cortex into the cancellous bone and again when the drill exits the outer layer of the far cortex.

Now it's time to put these two sensory inputs (sound and tactile feedback) together during bicortical drilling training!

2D and 3D Spectrograms of Bicortical Drilling of a Tibial Fracture

Play the video and audio files simultaneously to identify the acoustic changes of the drill as it progresses through the near cortex, cancellous bone, and the outer layer of the far cortex, and is backed out of the drilled hole.

• Remove the clay backstop from the Tibial Shaft Simulator and use the depth gauge to measure the plunge depths.
• Record the plunge depths and calculate the average plunge depth values in the Training Logbook.

Self assessment

Self-assessment

Please fill out the printed Training Logbook for your records.

Acknowledgements

This work is funded by a grant from the Intuitive Foundation. Any research, findings, conclusions, or recommendations expressed in this work are those of the author(s), and not of the Intuitive Foundation.

References