Length Changes of the Anterolateral Ligament During Passive Knee Motion: A Human Cadaveric Study.
BACKGROUND
Persistent rotatory instability after anterior cruciate ligament (ACL) reconstruction may be a result of unaddressed insufficiency of the anterolateral structures. Recent publications about the anatomy of the anterolateral ligament (ALL) have led to a renewed interest in lateral extra-articular procedures, and several authors have proposed ALL reconstruction to supplement intra-articular ACL reconstruction. However, only limited knowledge about the biomechanical characteristics of the ALL exists.


OBJECTIVE
The purpose of this study was to analyze length changes of the ALL during passive knee motion. The study hypothesis was that the ALL lengthens with knee flexion and internal tibial rotation.


METHODS
Controlled laboratory study.


METHODS
The ALL of 6 cadaveric knees was dissected. Specimens were mounted in a specifically designed test rig that allowed unconstrained passive flexion/extension movement between 0° and 90° as well as external/internal tibial rotation of 25° at various flexion angles. Highly elastic, capacitive polydimethylsiloxane strain gauges were attached to the insertion sites of the ALL. Length changes were recorded continuously at flexion angles between 0° and 90° and during internal/external tibial rotation at 0°, 15°, 30°, 45°, 60°, 75°, and 90°. All measurements were calculated as the relative length change (%) of the ALL compared with 0° of flexion and neutral rotation.


RESULTS
The mean relative length of the ALL significantly increased with increasing knee flexion (P < .001), with an estimated mean length change of +0.15% per degree. Both internal and external tibial rotation were independent determinants for length change; internal rotation significantly increased the length of the ALL (P < .001), whereas external rotation significantly decreased its length (P < .001). The mean length change with internal rotation increased with knee flexion, with a significantly greater length change at 90° compared with 0° (P = .048), 15° (P = .033), and 30° (P = .015). The maximum mean length change was +33.77% ± 9.62%, which was observed at 25° of internal rotation and 90° of flexion.


CONCLUSIONS
The ALL is a nonisometric structure that tensions with knee flexion and internal tibial rotation. Length changes with internal rotation were greater at higher flexion angles, with the greatest length change of the ALL observed at 90° of flexion.


CONCLUSIONS
The ALL can be considered a stabilizer against internal tibial rotation, especially at deep flexion angles. With regard to ALL reconstruction procedures, tensioning and fixation of the graft should be performed near 90° of flexion because graft tensioning near extension may cause excessive ligament strain with increasing knee flexion.
Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany Department of Microsystems Engineering (IMTEK), Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
Martin
M
Zens
Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany.
Philipp
P
Niemeyer
Department of Microsystems Engineering (IMTEK), Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
Johannes
J
Ruhhammer
Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany.
Anke
A
Bernstein
Department of Microsystems Engineering (IMTEK), Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
Peter
P
Woias
Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany.
Herrmann O
HO
Mayr
Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany.
Norbert P
NP
Südkamp
Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany matthias.feucht@gmx.net.
Matthias J
MJ
Feucht
D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000473:pathology* / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001182:Arthroscopy; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D016059:Range of Motion, Articular; D012399:Rotation
anterior cruciate ligament; anterolateral ligament; anterolateral rotational instability; anterolateral structures; knee biomechanics; length changes