2015 ISAKOS Biennial Congress ePoster #1111

The Anterolateral Ligament (ALL): A Comprehensive Study Encompassing Anatomic, Radiographic and Structural Properties

Mitchell I. Kennedy, Vail, CO UNITED STATES
Steven Claes, MD, PhD, Herentals BELGIUM
Fernando Fuso, MD, Sao Paulo, Sao Paulo BRAZIL
Brady Thomas Williams, BS, Vail, CO UNITED STATES
Mary T. Goldsmith, MSc, Vail, CO UNITED STATES
Travis Lee Turnbull, PhD, Vail, CO UNITED STATES
Coen Abel Wijdicks, PhD, München, Bavaria GERMANY
Robert F. LaPrade, MD, PhD, Chanhassen, MN UNITED STATES

Steadman Philippon Research Institute, Vail, Colorado, USA

FDA Status Not Applicable

Summary: This study encompasses anatomic, radiographic and structural properties of the ALL, subsequently leading to an evidence-based approach to anterolateral reconstructions.

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Abstract:

Purpose

Residual rotational instability following ACL reconstructions has drawn attention to the anterolateral ligament (ALL). The purpose of this comprehensive investigation was to provide quantitative anatomic, radiographic and structural data characterizing the ALL to lead to an evidence-based approach to anterolateral reconstructions.

Methods

Identification of the ALL was performed by an inside-out anatomic dissection of 10 cadaveric knees (males, 60.5 ± 8.6 years). Anatomic positioning of the ALL in relation to surrounding osseous landmarks and structures was obtained by a 3-dimensional coordinate measuring device (7315 Romer Absolute Arm). Digital measurements from AP and lateral radiographs were obtained with a picture archiving and communications system (PACS) program. Structural properties were determined from a pull-to-failure study using a tensile tester (Instron E10000). Fibers of the ALL were positioned to be axial and parallel to the applied vertical force vectors. Measurements are reported as average ± standard deviation.

Results

Anatomy. The ALL was identified in all specimens, as a thickening within the lateral capsule acquiring tension at 30° of flexion. From its femoral attachment, posterior to the fibular collateral ligament (FCL) attachment, it coursed antero-distally to its anterolateral tibial attachment. Every specimen displayed an attachment to the lateral meniscus. At 90° of knee flexion, the ALL length was 41.3 ± 5.1 mm. In nine of ten knees, the ALL attached posterior to the femoral FCL attachment and one knee also attached half to the lateral epicondyle. The femoral attachment area of the ALL was 68.7 ± 18.5 mm2 and was 5.7 ± 1.2 mm posterior to the lateral epicondyle. The tibial attachment was approximately mid-way between Gerdy’s tubercle and the fibular head with distances of 24.2 ± 2.6 mm and 23.9 ± 2.4 mm, respectively. The tibial attachment area measured 59.5 ± 22.0 mm2 and was 9.4 ± 2.1 mm distal to the joint line.
Radiography: Radiographic ALL distances on AP views were 28.2 ± 3.2 and 12.4 ± 2.1 to the joint line for the femoral and tibial attachments, respectively. Lateral view distances for the femoral attachment measured 9.5 ± 3.8 mm to the lateral epicondyle and 3.8 ± 1.3 mm to the lateral gastrocnemius tendon attachment. The tibial attachment measured 7.1 ± 1.3 mm to the joint line, 19.5 ± 3.0 mm to Gerdy’s Tubercle, 10.5 ± 4.6 mm to the biceps femoris tibial attachment and 20.0 ± 3.1 mm to the anterior fibular margin on the lateral view. Radiographic measurements demonstrated excellent intra-rater agreement (ICCs > 0.99).
Biomechanics: Analysis of the structural properties yielded an average maximum load-at-failure of 182 ± 73 N. Failure occurred by three distinct mechanisms: 3 had a ligamentous tear at the femoral origin, 4 tore midsubstance and 3 had a complete detachment from the tibia (Segond fracture equivalent).

Conclusions

This study defined the anatomic, radiographic and structural properties of the ALL. These defined attachment locations can be identified with intraoperative radiographs. The biomechanical analysis indicated that most traditional soft tissue grafts can reproduce the structural properties of the ALL.