ePoster #309 - ISHA Annual Scientific Meeting 2016

Anatomic Reconstruction of the Native Ligamentum Teres

Alex W. Brady, MSc, Vail, CO UNITED STATES
Jorge Chahla, MD, Vail, CO UNITED STATES
Jacob D. Mikula, BS, Vail, CO UNITED STATES
Erik Slette, BA, Vail, CO UNITED STATES
Renato Locks, MD, Vail, CO UNITED STATES
Robert F. LaPrade, MD, PhD, Vail, CO UNITED STATES
Marc J. Philippon, MD, Vail, CO UNITED STATES

Steadman Philippon Research Institute, Vail, CO, UNITED STATES

FDA Status Not Applicable

Summary: This study provides guidelines for optimal tunnel placement in the femur and acetabulum for anatomic reconstruction of the ligamentum teres (LT).

Abstract:
Objectives: As arthroscopic reconstruction of the ligamentum teres (LT) gains acceptance among surgeons, a clear understanding of the LT anatomy is necessary to guide anatomic LT reconstructions. Current arthroscopic LT reconstructions focus on reproducing only one attachment location for both the acetabulum and femur, as it is less technically demanding than reconstructing each bundle (transverse, anterior and posterior margins of the acetabular notch and iliac, ischial and pubic attachments on the cotyloid fossa). Typically, the femoral tunnel emerges at the center of the LT attachment within the fovea capitis, and the acetabular tunnel is positioned in the posteroinferior portion of the cotyloid fossa. However, there is a paucity of published literature describing the tunnels for a safe, anatomic LT reconstruction. Therefore, the purpose of this study was to provide a quantitative description of the LT reconstruction tunnels in both the femur and the acetabulum during an anatomic reconstruction. Methods: Nine human cadaveric pelvises, complete with femurs, (mean age: 59.6, range 47-65) were studied. Prior to dissection, a 3-D coordinate measuring device was used to record the neutral orientation of the femur in the acetabulum. The specimens were then dissected free of all extra-articular soft tissue and dislocated, granting internal access to the 3-D coordinate measuring device which was used to digitize the bony anatomy and record the locations of pertinent structures. The digitized femur and pelvis were numerically aligned to neutral and then repositioned laterally and distally to approximate the clinical setting of hip distraction during an arthroscopic procedure. An axis connecting the center of the femoral LT attachment to the center of the femoral neck was defined to simulate a reconstruction tunnel of diameter 7mm, and its intersection with the lateral aspect of the femur (i.e., anatomic reconstruction tunnel entry point) was measured. Finally, the femur was digitally internally rotated up to 20 degrees, and externally up to 40 degrees as well as abducted 30 degrees and adducted 20 degrees in increments of one degree, resulting in 3000 total tested positions. For each position, the location of the tunnel in the acetabulum was measured with respect to the obturator bundle and the edge of the acetabular fossa. All results are reported as [mean +\- standard deviation]. Results: The anatomic reconstruction tunnel entry point on the lateral side of the femur was located at a mean distance of [7.0 +/- 1.9]mm distal and [5.8 +/- 4.5]mm anterior from the center of the vastus ridge. By angling the femur with 20 degrees of internal rotation and 5 degrees of abduction, the obturator bundle was avoided in 100% of specimens, and the tunnel remained within the acetabular fossa. This orientation causes the reconstruction tunnel to enter the posterior inferior wall of the acetabular fossa. Conclusion: The main finding of this study was that a ligamentum teres reconstruction tunnel of diameter 7mm can be safely reamed through the femur and acetabulum by angling the femur at 20 degrees of internal rotation and 5 degrees of abduction. These quantitative anatomic reconstruction parameters can be applied intraoperatively to guide tunnel placement during an anatomic LT reconstruction.