Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads.
ABSTRACT The anterior cruciate ligament (ACL) can be anatomically divided into anteromedial (AM) and posterolateral (PL) bundles. Current ACL reconstruction techniques focus primarily on reproducing the AM bundle, but are insufficient in response to rotatory loads. The objective of this study was to determine the distribution of in situ force between the two bundles when the knee is subjected to anterior tibial and rotatory loads. Ten cadaveric knees (50+/-10 years) were tested using a robotic/universal force-moment sensor (UFS) testing system. Two external loading conditions were applied: a 134 N anterior tibial load at full knee extension and 15 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion and a combined rotatory load of 10 Nm valgus and 5 Nm internal tibial torque at 15 degrees and 30 degrees of flexion. The resulting 6 degrees of freedom kinematics of the knee and the in situ forces in the ACL and its two bundles were determined. Under an anterior tibial load, the in situ force in the PL bundle was the highest at full extension (67+/-30 N) and decreased with increasing flexion. The in situ force in the AM bundle was lower than in the PL bundle at full extension, but increased with increasing flexion, reaching a maximum (90+/-17 N) at 60 degrees of flexion and then decreasing at 90 degrees. Under a combined rotatory load, the in situ force of the PL bundle was higher at 15 degrees (21+/-11 N) and lower at 30 degrees of flexion (14+/-6 N). The in situ force in the AM bundle was similar at 15 degrees and 30 degrees of knee flexion (30+/-15 vs. 35+/-16 N, respectively). Comparing these two external loading conditions demonstrated the importance of the PL bundle, especially when the knee is near full extension. These findings provide a better understanding of the function of the two bundles of the ACL and could serve as a basis for future considerations of surgical reconstruction in the replacement of the ACL.
Dataset: Barriers to Predicting the Mechanisms and Risk Factors of Non-Contact Anterior Cruciate Ligament Injury[show abstract] [hide abstract]
ABSTRACT: High incidences of non-contact anterior cruciate ligament (ACL) injury, frequent requirements for ACL reconstruction, and limited understanding of ACL mechanics have engendered considerable interest in quantifying the ACL loading mechanisms. Although some progress has been made to better understand non-contact ACL injuries, information on how and why non-contact ACL injuries occur is still largely unavailable. In other words, research is yet to yield consensus on injury mechanisms and risk factors. Biomechanics, video analysis, and related study approaches have elucidated to some extent how ACL injuries occur. However, these approaches are limited because they provide estimates, rather than precise measurements of knee -and more specifically ACL -kinematics at the time of injury. These study approaches are also limited in their inability to simultaneously capture many of the contributing factors to injury. This paper aims at elucidating and summarizing the key challenges that confound our understanding in predicting the mechanisms and subsequently identifying risk factors of non-contact ACL injury. This work also appraise the methodological rigor of existing study approaches, review testing protocols employed in published studies, as well as presents a possible coupled approach to better understand injury mechanisms and risk factors of non-contact ACL injury. Three comprehensive electronic databases and hand search of journal papers, covering numerous full text published English articles were utilized to find studies on the association between ACL and injury mechanisms, ACL and risk factors, as well as, ACL and investigative approaches. This review unveils that new research modalities and/or coupled research methods are required to better understand how and why the ACL gets injured. Only by achieving a better understanding of ACL loading mechanisms and the associated contributing factors, one will be able to develop robust prevention strategies and exercise regimens to mitigate non-contact ACL injuries.
Article: Computer-assisted anatomically placed double-bundle ACL reconstruction: an in vitro experiment with different tension angles for the AM and the PL graft.[show abstract] [hide abstract]
ABSTRACT: Anterior cruciate ligament reconstruction techniques are evolving with innovations like double-bundle (DB) grafts and computer assistance. The current DB techniques do not appear to make the clinical difference yet. Insight in various techniques may lead to better results. In this study, the anterior laxity of a DB reconstruction with an anteromedial (AM) graft fixated in 90° of flexion and a posterolateral (PL) graft fixated in 20° and computer-assisted anatomically placed femoral attachments was compared to normal values and single-bundle grafts. In 8 fresh-frozen human cadaveric knees, the anterior laxity was tested from 0° to 90° flexion, with a 100 Newton (N) anterior tibial load in joints with (1) intact ACL, (2) torn ACL, (3) single-bundle (SB) graft tensed with 15 N in 20°, (4) anatomic AM graft tensed with 15 N in 90°, (5) anatomic PL graft tensed with 15 N in 20°, and (6) anatomic DB graft (4+5). All reconstructions caused a posterior position of the tibia. Relative to the normal anterior laxity, the single-bundle techniques showed significantly increased laxities: The SB technique in 0° (+1.1 mm) and 15° (+1.7 mm); The AM reconstructions in 45° (+1.6 mm) and 90° (+1.5 mm); The PL reconstructions in all angles (from +1.4 to +2.3 mm), except in 0°. The anatomic DB technique showed no significantly increased laxities and restored normal laxity in all angles.Medical Engineering & Physics 11/2011; 34(8):1031-6. · 1.62 Impact Factor
Article: Anatomic Double Bundle single tunnel Foreign Material Free ACL-Reconstruction – a technical note[show abstract] [hide abstract]
ABSTRACT: The anterior cruciate ligament (ACL) consists of two bundles, the anteromedial (AM) and posterolateral bundle (PM). Double bundle reconstructions appear to give better rotational stability. The usual technique is to make two tunnels in the femur and two in the tibia. This is difficult and in small knees may not even be possible. We have developed a foreign material free press fit fixation for double bundle ACL reconstruction using a single femoral tunnel (R) . This is based on the ALL PRESS FIT ACL reconstruction. It is suitable for the most common medium and, otherwise difficult, small sizes of knees. Method: Using diamond edged wet grinding hollow reamers, bone cylinders in different diameters are har-vested from the implantation tunnels of the tibia and fe-mur and used for the press fit fixation. Using the press fit technique the graft is first fixed in tibia. It is then sim-ilarly fixed under tension in the femoral side with the knee in 120 degree flexion. This is called Bottom To Top Fixation (BTT). On extending the knee the graft tension is self adapting. Depending on the size of the individual knee, the diameter of the femoral bone plug is varied from 8 to 13 mm to achieve an anatomic spread with a double bundle-like insertion. The tibia tunnel can be ap-plied with two 7 or 8 mm diameter tunnels overlapping to a semi oval tunnel between 10 to 13 mm. Results: Since May 2003 we have carried out ACL-re-constructions with Hamstring grafts without foreign material using the ALL PRESS FIT technique. Initially, an 8 mm press fit fixation was used proximally with good results. Since April 2008, the range of diameters was increased up to 13 mm. The results of the Lachman tests have been good to excellent. Results of the Pivot shift test suggested more stability with femoral broader diameters of 9,5 to 13 mm. Conclusions: The foreign material free fixation of ham-string in the ALL PRESS FIT Bottom To Top Fixation is a successful method for ACL Reconstruction. The Diamond Instruments and tubed guiding devices are precise, reliable and easy to manage. On this basis a double bundle reconstruction is achieved using a sin-gle tunnel. A broad anatomic femoral insertion with au-togenous bone plugs inserted near the cortex seems to improve rotational stability.Muscle, Ligaments and Tendons Journal. 01/2012; 1Vol. I (No. 4) - 2011 October/December(4):147-151.