FEMUR TUNNEL CALCULATIONS IN ACL SURGERY

Summary

This detailed video script covers the key aspects of femoral tunnel length and loop size calculations during ACL surgeries. It discusses the importance of accurate measurement using a retrorog system (retro B pin), proper tunnel length for different button sizes (15mm, 20mm, and 25mm), and the critical 7mm flipping distance required for optimal button placement. The script also compares fixed, adjustable, and hybrid loops (EOB button Flex), highlighting their advantages in achieving better graft tunnel filling. A strong emphasis is placed on precise pre-surgical planning to avoid complications like soft tissue flipping and tunnel underfilling.

Takeaways

• 😀 **Femoral Tunnel Measurement**: The retrograde pin system is recommended for measuring the femoral tunnel length accurately, ensuring it aligns with the anatomical origin or insertion of the ACL.
• 😀 **Minimum Tunnel Length**: A femoral tunnel length of at least 30 mm is required for proper graft fixation. Anything less may compromise the procedure.
• 😀 **Button Size Selection**: Button sizes should be chosen based on the femoral tunnel length: 15 mm for 30-35 mm tunnels, 15 or 20 mm for 35-40 mm tunnels, and 20 or 25 mm for tunnels longer than 40 mm.
• 😀 **Flipping Distance**: A flipping distance of 7 mm must be deducted from the total length when calculating drill depth to ensure the button sits securely in bone, not soft tissue.
• 😀 **Adjustable Loops**: Adjustable loops offer flexibility in tunnel graft placement. The exact length of the graft inside the tunnel should be calculated, but retrograde measurement is still essential for accuracy.
• 😀 **EOB Button Flex**: The hybrid EOB button combines features of both fixed and adjustable loops, allowing further graft adjustment after flipping, which leads to more complete tunnel filling.
• 😀 **Drilling Guidelines**: When using a 15 mm button in a 33 mm femoral tunnel, the drilling should be done to 25 mm (33 mm - 7 mm flipping distance). Similarly, for a 39 mm tunnel with a 20 mm button, drill to 26 mm.
• 😀 **Adjustable Loop Lengthening**: While adjustable loops allow for a tighter graft fit, they may also introduce some loop lengthening (2-3 mm), though this is minimal in the EOB Button Flex device.
• 😀 **Retrograde Pin vs. AR Measurement**: Retrograde pin measurement is preferred over AR measurement as it provides more accuracy early in the process, avoiding complications later in surgery.
• 😀 **Button Placement and Adjustments**: For adjustable loops, it’s critical to mark the button location accurately (e.g., marking 4 cm for a 40 cm tunnel) to ensure proper flipping and avoid misplacement in soft tissue.

Q & A

What is the purpose of the retrograde pin in ACL surgery?

The retrograde pin, marked with a pointer, is used to measure the femoral tunnel length during ACL surgery. It helps ensure the tunnel is drilled at the correct anatomical location and provides an accurate measurement of the tunnel length before proceeding with the graft placement.

What is the minimum femoral tunnel length required for an ACL surgery, and why is this important?

The minimum femoral tunnel length required is 30mm. This ensures that there is sufficient space for the graft to be placed inside the tunnel. The graft should ideally be at least 15mm within the tunnel, and anything shorter could lead to complications with graft fixation or improper tunnel filling.

How do you calculate the appropriate button size for the femoral tunnel?

The button size is chosen based on the tunnel length. If the tunnel length is between 30-35mm, a 15mm button is used; for 35-40mm, a 15mm or 20mm button can be used; and for lengths over 40mm, a 20mm or 25mm button is recommended. A 7mm flipping distance is also subtracted from the tunnel length when determining the drill depth.

Why is a 7mm flipping distance important in ACL surgery?

The 7mm flipping distance ensures that the button can flip correctly inside the tunnel without being too tight or causing damage to surrounding tissues. It is subtracted from the tunnel length to determine the correct drill depth, ensuring proper graft fixation and tunnel filling.

What is the primary advantage of using an adjustable loop in ACL surgery?

The primary advantage of using an adjustable loop is that it allows for more precise control over the graft length inside the femoral tunnel. The loop can be shortened or adjusted after flipping, helping achieve better graft tension and more complete filling of the tunnel.

What is the role of the EOB Button Flex, and how does it differ from fixed and adjustable loops?

The EOB Button Flex is a hybrid device that combines features of both fixed and adjustable loops. It offers the same tunnel calculations as a fixed loop, but after flipping, it allows for further tensioning of the graft, resulting in better tunnel filling compared to a fixed loop. This makes it more adaptable to different tunnel sizes.

How does the tunnel length affect graft fixation in ACL surgery?

The tunnel length directly influences graft fixation because a shorter tunnel may not provide enough space for the graft to be securely positioned inside the tunnel. A longer tunnel allows for better fixation, with the graft properly anchored and tensioned within the femoral tunnel.

What are the potential risks of having a tunnel length shorter than the required 30mm?

If the tunnel length is shorter than 30mm, there may not be enough space to accommodate the graft securely. This could lead to complications such as graft failure, improper tunnel filling, or difficulty in flipping the button, ultimately compromising the success of the ACL reconstruction.

In ACL surgery, when is it recommended to revise the femoral tunnel?

If the femoral tunnel length is less than 30mm, it is recommended to revise the tunnel. This ensures there is enough space for the graft, reducing the risk of failure and ensuring a better surgical outcome.

Why is retrograde measurement preferred over an anterior-to-posterior (ANR) measurement method?

Retrograde measurement is preferred because it allows for an immediate, accurate assessment of the tunnel length right after drilling, helping guide the procedure more effectively. With ANR measurement, the length must be measured after drilling, which can introduce inaccuracies if the tunnel length is too short.