Figure 2 The distal end of the tibia was

potted in poly(methyl methacrylate)

(PMMA; Fricke Dental International Inc)

and rigidly secured to the base of a tensile

testing machine (ElectroPuls E10000;

Instron). The vertical alignment of the

anterolateral ligament during pull-to-failure

testing (anterolateral view, left knee). The

tibia was manipulated posteriorly relative to

normal knee positioning to achieve vertical

alignment of the anterolateral ligament

(ALL). Immediately after preconditioning,

each specimen was pulled to failure at 20

mm/min.

Specimens 15 non-paired, fresh-frozen human cadaveric knees (male;

mean age, 58.2 years; range, 39-69 years). Knees with history of surgery,

ligamentous injury, and/or indications of osteoarthritis were excluded.

Tissues were kept moist with a 0.9% saline solution applied throughout all

phases of testing.

Anatomic Dissection Technique Identification of the ALL was

performed by a combined outside-in and inside-out anatomic dissection. The

ITB was inferiorly reflected to its distal aspect following a midsubstance

incision 6 cm proximal to the lateral epicondyle. Previous literature has

noted that fibers of the ALL become taut with an applied internal rotation

between 30° and 60° of knee flexion.

Anatomic Data Collection Quantitative anatomic relationships were

made using a 3-dimensional coordinate measuring device (7315 Romer

Absolute Arm; Hexagon Metrology). Measurements on anteroposterior (AP)

and lateral radiographs were obtained by use of a picture archiving and

communications system program (eFilm Workstation 3.4; Merge Healthcare

Inc).

1Department of BioMedical Engineering, Steadman Philippon Research Institute, Vail, Colorado. 2The Steadman Clinic, Vail, Colorado

Kennedy MI1; Claes S; Fernando FF2; Williams BT1; Goldsmith MT1; Turnbull TL1;Wijdicks CA1; LaPrade RF1,2

The Anterolateral LigamentAn Anatomic, Radiographic, and Biomechanical Analysis

Biomechanical Testing The distal end of the tibia was potted in

poly(methyl methacrylate) (PMMA; Fricke Dental International

Inc) and rigidly secured to the base of a tensile testing machine

(ElectroPuls E10000; Instron). The femur was rigidly secured at

30° of knee flexion via a custom fixture such that the fibers of the

ALL were oriented in line with the vertically applied force vector.

Cyclic preconditioning occurred between 10 and 25 N at 0.1 Hz for

10 cycles. Immediately after preconditioning, each specimen was

pulled to failure at 20 mm/min. Metrics of analysis included the

maximum load obtained during pull-to-failure testing; stiffness,

which was calculated between 10 N and 75% of the individual

specimen maximum load during pull-to-failure testing; and the

mechanism of failure.

The ALL was identified in all specimens as a ligamentous structure coming under

tension during internal rotation at 30° of flexion (Figure 1). Qualitatively, the ALL

originated on the femur posterior and proximal to the FCL attachment and coursed

anterodistally to its anterolateral tibial attachment (Figures 5 and 6). All specimens

had an attachment between the ALL and the lateral meniscus that needed to be

severed to completely isolate the ALL. In 14 of 15 knees, the ALL attached posterior

and proximal to the femoral FCL attachment, which was measured as an average of

2.7 mm proximal and 2.8 mm posterior to the FCL and ranging from 0.9 mm distal to

6.7 mm proximal and 0.2 mm to 7.7 mm posterior

• We observed that the capsular thickening of the lateral knee

contains a ligament, the anterolateral ligament (ALL), primarily

coursing from posterior and proximal to the lateral femoral

epicondyle to the anterolateral tibia

• The defined attachment locations can be augmented with

intraoperative radiographs for reconstruction guidance

• Failure mechanisms of the ALL included tearing at the femoral

origin, intrasubstance tears, and bony avulsions of its tibial

attachment (Segond fractures)

• The ALL was consistently found in all knees. Also, Segond

fractures appear to occur primarily from avulsion of the ALL,

which were posterior to Gerdy’s tubercle.

• For surgical reference: the ALL originated on the femur posterior

and proximal to the FCL attachment and coursed anterodistally to

its anterolateral tibial attachment. All specimens had an

attachment between the ALL and the lateral meniscus.

• If necessary, the ALL can be adequately reconstructed using most

soft tissue grafts.

Objectives

Materials & Methods

BackgroundRecent publications have described significant variability in the femoral

attachment and overall anatomy of the anterolateral ligament (ALL).

Additionally, there is a paucity of data on its structural properties.

PurposeTo provide quantitative data characterizing the anatomic and radiographic

locations and the structural properties of the ALL to guide graft selection

and placement and to facilitate future the development of an evidence-based

approach to ALL reconstructions.

Conclusions

References

Clinical Significance

Acknowledgements

Results

Figure 1.

The Steadman Philippon Research Institute is a 501(c)(3) non-profit

institution supported financially by private donations and corporate support

from the following entities: Smith & Nephew Endoscopy, Inc., Arthrex, Inc.,

Siemens Medical Solutions USA, Inc., ConMed Linvatec, Inc., Össur

Americas, Inc., Small Bone Innovations, Inc., Opedix, Inc., and Sonoma

Orthopedics, Inc.

Statistical AnalysisAll anatomic and radiographic measurements were reported as mean values and 95% confidence

intervals. stiffness, which was calculated between 10 N and 75% of the individual specimen

maximum load during pull-to-failure testing; and the mechanism of failure. The biomechanical

testing results were reported as averages with the 95% CI. On the anteroposterior view (Figure

2), a reference line tangent to the most distal extents of the medial and lateral femoral condyles

established the proximal joint line.

Figure 3 Results from biomechanical tensile testing (testing machine:ElectroPuls

E10000; Instron) of ALL (n = 15)

The average maximum load during pull-to-failure testing was 175 N (95% CI,

139-211 N). The average stiffness was 20 N/mm (95% CI, 16-25 N/mm). The

most frequent detachments were complete detachments from the tibia

accompanied by bony avulsions (n = 6) (Segond-type avulsion fracture).

Figure 4 Representative

photograph displaying a

Segond fracture from the tibia

after pull-to-failure testing of

the anterolateral ligament

(ALL) (anterolateral view, left

knee). Failure occurred by a

variety of mechanisms

including ligamentous tear at

the femoral origin (n = 4),

midsubstance tear (n = 4),

ligamentous tear at its tibial

origin (n = 1), and complete

detachments from the tibia

accompanied by bony

avulsions (n = 6) (Segond-

type avulsion fracture).

Figure 1 The attachments of the main lateral knee structures relative to the anterolateral ligament

(lateral view, left knee). The anterolateral ligament courses superior to the fibular collateral ligament.

ALL, anterolateral ligament; FCL, fibular collateral ligament; GT, Gerdy tubercle; IT, iliotibial; LGT,

lateral gastrocnemius tendon. The combined outside-in and inside-out dissection allowed for palpation

of the ALL capsular thickening, from both an extra-articular and an intra-articular approach. This was

facilitated through the removal of the patellar tendon, related anterior capsule, and ITB. Tissues

lacking tension were then dissected out, leaving the ligamentous structure of the ALL intact.

Figure 5 The osseous landmarks

and attachment sites of the main

structures of the lateral knee

(iliotibial band and non-ALL

related capsule removed) (lateral

view, right knee). The ALL

attaches posterior and proximal to

the FCL femoral attachment and

courses anterodistal to its

anterolateral tibial attachment

between the center of the Gerdy

tubercle and the anterior margin

of the fibular head. The short

head of the biceps femoris tendon

has a direct arm that attaches to

the fibular head and an anterior

arm that attaches to the antero-

lateral tibia. ALL, anterolateral

ligament; FCL, fibular collateral

ligament; LE, lateral epicondyle.

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• Terry GC, LaPrade RF. The biceps femoris muscle complex at the knee. Its

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anteromedial rotatory instability. Am J Sports Med. 1996; 24(1):2-8.

• Claes S, Luckyx T, Vereecke E, Bellemans J. The Segond fracture: a bony

injury of the anterolateral ligament of the knee. Arthroscopy.

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