Geometrical relationships between bone plug configuration and patellar tendon graft width

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Anterior cruciate ligament (ACL) reconstruction

Background:

• Optimal bone plug shape for patellar tendon grafts in ACL reconstruction is not well-defined in orthopedic literature.
• Clinical observation indicates bone plugs are often narrower than intended after contouring to fit bone tunnels.

Purpose of the Study:

• To mathematically evaluate the relationship between bone plug cross-sectional shape and its impact on osseous area and graft width.
• To determine the optimal bone plug shape for maximizing graft width and minimizing bone tunnel size discrepancies.

Main Methods:

• A mathematical study using trigonometric and geometric methods.
• Comparison of cross-sectional areas for triangular, rectangular, trapezoidal, and square bone plugs (8-11 mm graft widths).
• Calculation of minimum bone tunnel diameter required for each shape and maximum bone plug width within a given tunnel diameter.

Main Results:

• Square bone plugs filled the most area (64%) but required significantly larger tunnel diameters (4-5 mm larger than graft width).
• Trapezoidal (59%) and rectangular (51%) plugs offered a better balance of area fill and tunnel accommodation.
• Trapezoidal, rectangular, and triangular plugs resulted in less than 14% width reduction, while square plugs had a 29% reduction.

Conclusions:

• Harvesting trapezoidal or rectangular bone plugs is recommended for ACL reconstruction using the central one-third patellar tendon graft.
• These shapes provide satisfactory bone area while minimizing the difference between bone plug width and bone tunnel diameter.
• This approach addresses the clinical observation of narrower-than-intended grafts due to bone plug contouring.