Anterior cruciate ligament graft rotation. Reproduction of normal graft rotation

Editorial Commentary: The Ribbon Theory. Another Quantum Leap? The Anterior Cruciate Ligament Is Twisted and in Fact a Flat Structure. Or not?

Is the double bundle structure of the anterior cruciate ligament (ACL) a myth? Derotation untwists the ACL and results in a flat ribbon structure. However, other researchers dispute this theory and revealed 2 distinct bundles separated by a synovial septum. The answer is simple: we do not know and the evidence is conflicting.

The biomechanical effects of graft rotation on ACL reconstruction tunnel mismatch

PURPOSE

Bone block protrusion out of the tibial tunnel due to a relatively long graft is a common complication in anterior cruciate ligament surgical reconstruction with a patellar tendon. One possible solution is to shorten the patellar tendon graft already fixed in the femur by applying external rotation. This study aimed to evaluate the degree of shortening and biomechanical changes in porcine patellar grafts subjected to relatively higher degrees of rotation. Data obtained with rotations of 0°, 540°, 720°, and 900° were compared.

METHODS

Forty patellar porcine ligaments were subjected to biomechanical tests of degree of shortening, modulus of elasticity and maximum tension in the tendon before rupture. Tests were conducted using a universal mechanical testing machine and a computerized system for acquiring strength and deformation data.

RESULTS

Progressive shortening of the patellar ligament occurred with rotations of 0°, 540° and 720°. However, the degree of shortening showed no statistically significant difference as rotation increased from 720° to 900°. Decreased modulus of elasticity was observed compared with the graft rotation at 0° in all groups tested, but no statistically significant differences were observed among 540°, 720° and 900°. The maximum tension of the patellar tendon showed no change before rupture, regardless of the degree of rotation.

CONCLUSIONS

Rotating the patellar tendon is an efficient method for shortening a relatively long graft; however, more biomechanical studies are necessary to recommend this technique in clinical practice owing to the resulting decrease in graft stiffness that could compromise knee stability.

The effect of anterior cruciate ligament graft rotation on knee biomechanics

PURPOSE

The purpose of this study was to evaluate the effects on knee biomechanics of rotating the distal end of the bone-patellar tendon graft 90° in anatomic single-bundle (SB) anterior cruciate ligament (ACL) reconstruction with a porcine model.

METHODS

Twenty (n = 20) porcine knees were evaluated using a robotic testing system. Two groups and three knee states were compared: (1) intact ACL, (2) deficient ACL and (3) anatomic SB ACL reconstruction with (a) non-rotated graft or (b) rotated graft (anatomic external fibre rotation). Anterior tibial translation (ATT), internal (IR) and external rotation (ER) and the in situ tissue force were measured under an 89-N anterior tibial (AT) load and 4-N m internal and external tibial torques.

RESULTS

A significant difference from the intact ACL was found in ATT at 60° and 90° of knee flexion for rotated and non-rotated graft reconstructions (p < 0.05). There was a significant difference in the in situ force from the intact ACL with AT loading for rotated and non-rotated graft reconstructions at 60° and 90° of knee flexion (p < 0.05). Under IR loading, the in situ force was significantly different from the intact ACL at 30° and 60° of knee flexion for rotated and non-rotated graft reconstructions (p < 0.05). There were no significant differences in ATT, IR, ER and the in situ force between rotated and non-rotated reconstructions.

CONCLUSION

Graft rotation can be used with anatomic SB ACL reconstruction and not have a deleterious effect on knee anterior and rotational biomechanics. This study has clinical relevance in regard to the use of graft rotation to better reproduce the native ACL fibre orientation in ACL reconstruction.

Mid-Term Outcomes of Anterior Cruciate Ligament Reconstruction with Far Anteromedial Portal Technique

Purpose

The purpose of this study was to evaluate the mid-term outcomes of anatomic anterior cruciate ligament (ACL) reconstruction using two anteromedial (AM) portals by comparing with short-term follow-up results.

Materials and Methods

Fifty patients who were treated by ACL reconstruction using a two AM portal technique were evaluated retrospectively. The follow-up period was at least 5 years. The mean follow-up period was 68.5±13.9 months. The mid-term clinical outcomes were compared with short-term (≥12 months) results. For the assessment of knee stability, anterior tibial translation was evaluated using the Lachman test and the KT-2000. Rotational stability was evaluated using pivot shift test. For clinical assessment, the Lysholm and International Knee Documentation Committee scores were used.

Results

The average anterior translation was 2.1±1.4 mm at the short-term follow-up and 2.8±1.8 mm at the mid-term follow-up. Stability and midterm clinical outcomes were not significantly improved compared to the short-term follow-up results. At the mid-term follow-up, anteroposterior (AP) instability assessed by the KT-2000 was slightly increased, but still acceptable. On the other clinical physical evaluation, there was no statistically significant difference.

Conclusions

The short-term and mid-term outcomes of ACL reconstruction using the two AM portal technique were not significantly different except for AP stability although the value was less than 3 mm at both follow-ups. Therefore, this operative technique could be considered a satisfactory alternative for ACL reconstruction.

Anatomic single bundle anterior cruciate ligament reconstruction by the two anteromedial portal method: the comparison of transportal and transtibial techniques

Purpose

The purpose of this study was to report the results of anatomic single bundle anterior cruciate ligament (ACL) reconstruction by the two anteromedial portal method.

Materials and Methods

We evaluated the clinical results in 33 patients with ACL rupture who were treated by anatomic ACL reconstruction using the two anteromedial portal technique. The control group included 33 patients with ACL rupture who were treated with the conventional transtibial non-anatomic method. We performed an objective instability test, both preoperatively and at the final follow-up. We also compared the clinical results of both groups using International Knee Documentation Committee and Lysholm scores as a subjective test.

Results

At the final follow up, the study showed that in the control group, the Lachman test was negative in 27 cases (81.8%), the pivot shift test was negative in 26 cases (78.8%), and the average anterior translocation was 3.1 mm on a KT-2000 arthrometer. In the group of patients who underwent anatomic reconstruction by the two anteromedial portal method, the Lachman test was negative in 28 cases (84.8%), the pivot shift test was negative in 30 cases (90.9%), and the average anterior translocation was 2.8 mm on the KT-2000 arthrometer. Results in the pivot shift showed statistically significant improvement compared to the control group.

Conclusions

Anatomic ACL reconstruction by two anteromedial portals is an effective surgical technique that restores the rotational stability with excellent clinical results.

The effect of cyclic loading on rotated bone-tendon-bone anterior cruciate ligament graft constructs

BACKGROUND

Single-incision anterior cruciate ligament reconstruction with a bone-patellar tendon-bone construct is commonly performed with 180 degrees rotation of the graft. It has been hypothesized that further rotation of the graft to 540 degrees can effectively shorten the graft to address graft length-tunnel mismatch. Initial biomechanical failure characteristics of rotated constructs have been reported, but cyclic loading of tendons has not been performed.

HYPOTHESIS

Graft rotation affects the biomechanical properties of the construct.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-five bone-patellar tendon-bone composite porcine right knee specimens were randomized into 3 groups and were externally rotated to 0 degrees , 180 degrees , or 540 degrees . Each group was then cyclically loaded in an artificial synovial fluid medium between 50 and 250 N for 5,000 cycles, loaded between 50 and 500 N for an additional 5,000 cycles, and finally subjected to load-to-failure testing.

RESULTS

Graft rotation shortened constructs by 1.7 +/- 0.8 mm at 180 degrees of rotation and 7.6 +/- 2.0 mm at 540 degrees of rotation (P < .01). There was a statistically significant increase in strain during cyclic loading at 540 degrees . No significant differences in maximum load, yield stress, yield strain, or modulus of elasticity were detected in single-cycle load-to-failure testing after cyclic loading.

CONCLUSION

Rotation of bone-patellar tendon-bone constructs to 540 degrees predictably shortens the effective graft length at the expense of increased strain with cyclic loading at stresses equivalent to walking and running.

CLINICAL RELEVANCE

Although rotation to 540 degrees potentially addresses graft length-tunnel mismatch, further clinical evaluation is required to evaluate the impact of increased strain on knee laxity and to determine the effects of physiologic loading of rotated bone-patellar tendon-bone constructs in vivo.

Twist and its effect on ACL graft forces

Graft tension is a controversial topic in anterior cruciate ligament (ACL) surgery. Evidence suggests a narrow range of graft tensions, which allow the graft to remodel to a stable and mature neoligament. In previous cadaver experiments, we showed that twisting the graft could modulate the graft forces. In this study we hypothesized that the same phenomena would be found in patients, and that twisting the graft intraoperatively can reduce peak forces in the graft. The effects of twist on graft forces in bone-patellar tendon-bone grafts were measured during anterior cruciate ligament surgery on 15 consecutive patients using a custom-made tension-measurement device. Variations in surgical procedure that could potentially affect the graft force patterns were quantified. Graft force as a function of knee-flexion angle was measured with the graft in the neutral, untwisted position and repeated with the tibial bone block rotated externally or internally by 180 degrees. In eight of the 15 knees, external twisting of the graft reduced the maximal graft force to 50%. However, in five knees the forces in extension increased by twisting to a maximum of 300%. Of the surgical variables, only the femoral tunnel position appeared to have a consistent effect on the graft force pattern. Due to the unpredictable effect of graft twisting, a general recommendation on whether the graft should be twisted, and if so, in which direction, cannot be given. Intraoperatively, graft twisting may however be considered in every individual knee to modulate the graft force as a function of flexion angle.

Effects of graft rotation on initial biomechanical failure characteristics of bone-patellar tendon-bone constructs

BACKGROUND

Graft-tunnel mismatch is a potential problem during single-incision technique for anterior cruciate ligament reconstruction with the central third of the patellar tendon. Mismatch is present when the graft is too long to fit appropriately in the tunnels that have been created. Graft rotation is one method for addressing this problem.

PURPOSE

To determine the results of graft rotation up to 540 degrees on initial graft biomechanical properties and graft length.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty porcine bone-patellar tendon-bone constructs were divided into four groups and constructs were rotated to 0 degrees, 90 degrees, 180 degrees, and 540 degrees, respectively, for each group. Biomechanical testing to failure was performed with the constructs under tension at an elongation rate of 5 cm/sec. Lengths were measured after a 1-kg load was applied to the grafts.

RESULTS

No statistical difference in ultimate failure strength was encountered between any of the groups (P = 0.915). The grafts that were twisted to 540 degrees shortened an average of 5.41 mm, which represented an average shortening of 10% of the initial tendon length.

CLINICAL RELEVANCE

Graft rotation up to 540 degrees does not result in loss of initial graft strength, and may be a solution for graft-tunnel mismatch.

Effects of twisting of the graft in anterior cruciate ligament reconstruction

In an in vitro study on six knees from cadavers, the effect of bone-patellar tendon-bone graft twist on anterior knee laxity was measured at different knee flexion angles. A motion and loading rig was used to prescribe the flexion angle, to restrain axial rotation, and to apply 100 N anterior force to the tibia. Roentgen stereophotogrammetric analysis was used to measure the relative anteroposterior position of the tibia and femur. The tibial bone block was cemented in a cylinder that allowed rotation in the bone tunnel. The anterior cruciate ligament was transected and reconstructed with neutral, 90 degrees, and 150 degrees internal twists and 90 degrees and 150 degrees external twists. External and internal graft twists in the reconstruction resulted in significant reductions of anterior laxity, however, at the cost of a more posterior position of the unloaded tibia relative to the femur (anteroposterior-error). The results are explained by the anterior relocation of the graft insertion by twisting the tibial bone block. The inclination angle of the graft in the anteroposterior direction flattens, which could improve the anterior laxity. A consequent side effect is the increase of posterior shift of the tibia relative to the femur.

Complications in anterior cruciate ligament surgery

There are many potential problems associated with ACL surgery; however, careful attention to detail can prevent problems from occurring or provide corrective options in the event they do occur. Multiple backup options are not only desirable but also essential to a successful outcome. By following these guidelines, ACL surgery can have good long-term results and return the recreational or higher-level athlete to sports participation.

The position of the tibia during graft fixation affects knee kinematics and graft forces for anterior cruciate ligament reconstruction

Ten cadaveric knees (donor ages, 36 to 66 years) were tested at full extension, 15 degrees, 30 degrees, and 90 degrees of flexion under a 134-N anterior tibial load. In each knee, the kinematics as well as in situ force in the graft were compared when the graft was fixed with the tibia in four different positions: full knee extension while the surgeon applied a posterior tibial load (Position 1), 30 degrees of flexion with the tibia at the neutral position of the intact knee (Position 2), 30 degrees of flexion with a 67-N posterior tibial load (Position 3), and 30 degrees of flexion with a 134-N posterior tibial load (Position 4). For Positions 1 and 2, the anterior tibial translation and the in situ forces were up to 60% greater and 36% smaller, respectively, than that of the intact knee. For Position 3, knee kinematics and in situ forces were closest to those observed in the intact knee. For Position 4, anterior tibial translation was significantly decreased by up to 2 mm and the in situ force increased up to 31 N. These results suggest that the position of the tibia during graft fixation is an important consideration for the biomechanical performance of an anterior cruciate ligament-reconstructed knee.

A technique for resolution of graft-tunnel length mismatch in central third bone-patellar tendon-bone anterior cruciate ligament reconstruction

The existence of graft-tunnel length mismatch in correctly reconstructed anterior cruciate ligament (ACL)-deficient patients can occur due to both anatomic variation and compromised tunnel placement encountered during revision, despite attempts at prevention with accurate measurement techniques. This study reports a method for resolution of graft-tunnel length mismatch during central third bone-patellar tendon-bone ACL reconstruction. The technique involves rotation of the graft to shorten its length. Variation in graft shortening occurs depending on the direction of rotation, with external rotation achieving greater shortening. At 630 degrees of external rotation, approximately 25% shortening of the collagenous portion of the graft can be achieved, which allows for adequate bitunnel interference fixation in most instances. This technique can be used during difficult ACL reconstructions, both primary and revision, and may also have uses in routine reconstructions. Early clinical results are presented.