The Role of the Posterior Fibers of Anterior Cruciate Ligament Femoral Footprint in Ligament Failure
Author(s):
Sabzevari S. (United States of America)
,
Sabzevari S. (United States of America)
Affiliations:
Shaikh H.
,
Shaikh H.
Affiliations:
Marshall B.
,
Marshall B.
Affiliations:
Zhu J.
,
Zhu J.
Affiliations:
Linde Monica A.
,
Linde Monica A.
Affiliations:
Smolinski P.
,
Smolinski P.
Affiliations:
Fu F.
Fu F.
Affiliations:
ESSKA Academy. Sabzevari S. 05/09/18; 209381; P04-1411 Topic: Biomechanics
Dr. Soheil Sabzevari
Dr. Soheil Sabzevari
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Abstract
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Objectives: Studies of anterior cruciate ligament anatomy have found that the areas at the insertion sites are greater than the mid-substance cross-sectional area [1]. The reason for this morphology is debated and some studies have found that the additional area does not have a functional effect [2]. The purpose of this study was to evaluate the effect of the increase in insertion site area, the posterior fan-like extension of femoral footprint, on ACL failure load.

Methods: Ten fresh frozen, porcine specimens were used for constancy in age, breed and size. The knees were dissected of all tissues other than the ACL, placed in a material testing machine at 30° of flexion (full porcine extension) and subjected to anterior tibial loading (60 mm/min) until ACL failure. The knees were divided into two groups (n=5): intact femoral ACL insertion and reduced femoral ACL insertion. The flared posterior fan-like extension of femoral insertion of the ACL was identified by flexion [3]. The dense midsubstance part of the ACL was tight in flexion and extension but flexion folded the posterior fan-like extension of the footprint. The folded area of the posterior inferior fan-like extension was dissected from the femur using a number 11 blade. The original and dissected insertion sites were digitized using a probe (Faro, Inc.) and measured. Data was analyzed using an independent t-test (p < 0.05).

Results: The intact ACL had an area of 182.1 ± 17.1 mm2, the midsubstance insertion had an area of 113.3 ± 16.6 mm2, and the cut posterior fan-like extension portion had an area of 67.1 ± 8.3 mm2. The failure load of the ACL intact group was 3598.9 ± 456.5 N and was significantly higher (p<0.001) than the 392.0 ± 83.1 N failure load of the ACL cut group. The displacement at failure of the ACL intact group was 45.6 ± 5.8 mm2 and was significantly higher (p<0.001) than the 27.7 ± 7.7 mm2 of the ACL cut group.

Conclusions: This study found that the effect of the transection of the posterior fan-like extension of femoral insertion site (equal to lower part of ACL footprint in arthroscopic view) had a significant effect on ligament failure load. The effect of the fan like shape of the ligament may serve to reduce stress at the insertion site. This study found the functional benefit of ACL's morphological changes at the insertion sites. Remnant preservation in ACL reconstruction may potentially be a way to preserve this morphology.

References
1. Fujimaki et al., AJSM, 2016. 2. Yasuyuki et al., Arthroscopy, 2014. 3. Yasuyuki et al., Arthroscopy, 2014.

Keywords:
ACL failure load; Femoral insertion; Posterior fan-like extension
Objectives: Studies of anterior cruciate ligament anatomy have found that the areas at the insertion sites are greater than the mid-substance cross-sectional area [1]. The reason for this morphology is debated and some studies have found that the additional area does not have a functional effect [2]. The purpose of this study was to evaluate the effect of the increase in insertion site area, the posterior fan-like extension of femoral footprint, on ACL failure load.

Methods: Ten fresh frozen, porcine specimens were used for constancy in age, breed and size. The knees were dissected of all tissues other than the ACL, placed in a material testing machine at 30° of flexion (full porcine extension) and subjected to anterior tibial loading (60 mm/min) until ACL failure. The knees were divided into two groups (n=5): intact femoral ACL insertion and reduced femoral ACL insertion. The flared posterior fan-like extension of femoral insertion of the ACL was identified by flexion [3]. The dense midsubstance part of the ACL was tight in flexion and extension but flexion folded the posterior fan-like extension of the footprint. The folded area of the posterior inferior fan-like extension was dissected from the femur using a number 11 blade. The original and dissected insertion sites were digitized using a probe (Faro, Inc.) and measured. Data was analyzed using an independent t-test (p < 0.05).

Results: The intact ACL had an area of 182.1 ± 17.1 mm2, the midsubstance insertion had an area of 113.3 ± 16.6 mm2, and the cut posterior fan-like extension portion had an area of 67.1 ± 8.3 mm2. The failure load of the ACL intact group was 3598.9 ± 456.5 N and was significantly higher (p<0.001) than the 392.0 ± 83.1 N failure load of the ACL cut group. The displacement at failure of the ACL intact group was 45.6 ± 5.8 mm2 and was significantly higher (p<0.001) than the 27.7 ± 7.7 mm2 of the ACL cut group.

Conclusions: This study found that the effect of the transection of the posterior fan-like extension of femoral insertion site (equal to lower part of ACL footprint in arthroscopic view) had a significant effect on ligament failure load. The effect of the fan like shape of the ligament may serve to reduce stress at the insertion site. This study found the functional benefit of ACL's morphological changes at the insertion sites. Remnant preservation in ACL reconstruction may potentially be a way to preserve this morphology.

References
1. Fujimaki et al., AJSM, 2016. 2. Yasuyuki et al., Arthroscopy, 2014. 3. Yasuyuki et al., Arthroscopy, 2014.

Keywords:
ACL failure load; Femoral insertion; Posterior fan-like extension
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