Masayoshi Yagi

Biomechanical Analysis of an Anatomic Anterior Cruciate Ligament Reconstruction

Background: The focus of most anterior cruciate ligament reconstructions has been on replacing the anteromedial bundle and not the posterolateral bundle. Hypothesis: Anatomic two-bundle reconstruction restores knee kinematics more closely to normal than does single-bundle reconstruction. Study Design: Controlled laboratory study. Methods: Ten cadaveric knees were subjected to external loading conditions: 1) a 134-N anterior tibial load and 2) a combined rotatory load of 5-N·m internal tibial torque and 10-N·m valgus torque. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for 1) intact, 2) anterior cruciate ligament deficient, 3) single-bundle reconstructed, and 4) anatomically reconstructed knees. Results: Anterior tibial translation for the anatomic reconstruction was significantly closer to that of the intact knee than was the single-bundle reconstruction. The in situ force normalized to the intact anterior cruciate ligament for the anatomic reconstruction was 97% ± 9%, whereas the single-bundle reconstruction was only 89% ± 13%. With a combined rotatory load, the normalized in situ force for the single-bundle and anatomic reconstructions at 30° of flexion was 66% ± 40% and 91% ± 35%, respectively. Conclusions: Anatomic reconstruction may produce a better biomechanical outcome, especially during rotatory loads. Clinical Relevance: Results may lead to the use of a two-bundle technique.

Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads

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 forcemoment sensor (UFS) testing system. Two external loading conditions were applied: a 134 N anterior tibial load at full knee extension and 15°, 30°, 60°, and 90° of flexion and a combined rotatory load of 10 N m valgus and 5 N m internal tibial torque at 15° and 30° 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° of flexion and then decreasing at 90°. Under a combined rotatory load, the in situ force of the PL bundle was higher at 15° (21 ± 11 N) and lower at 30° of flexion (14 ± 6 N). The in situ force in the AM bundle was similar at 15° and 30° 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.

The effectiveness of reconstruction of the anterior cruciate ligament with hamstrings and patellar tendon . A cadaveric study comparing anterior tibial and rotational loads.

Background: The objective of this study was to evaluate the effectiveness of reconstructions of the anterior cruciate ligament to resist anterior tibial and rotational loads. We hypothesized that current reconstruction techniques, which are designed mainly to provide resistance to anterior tibial loads, are less effective in limiting knee instability in response to combined rotational loads. Methods: Twelve fresh-frozen young human cadaveric knees (from individuals with a mean age [and standard deviation] of 37 ± 13 years at the time of death) were tested with use of a robotic/universal force-moment sensor testing system. The loading conditions included (1) a 134-N anterior tibial load with the knee at full extension and at 15°, 30°, and 90° of flexion, and (2) a combined rotational load of 10 N-m of valgus torque and 10 N-m of internal tibial torque with the knee at 15° and 30° of flexion. The kinematics of the knees with an intact and a deficient anterior cruciate ligament, as well as the in situ force in the intact anterior cruciate ligament, were determined in response to both loads. Each knee then underwent reconstruction of the anterior cruciate ligament with use of a quadruple semitendinosus-gracilis tendon graft and was tested. A second reconstruction was performed with a bone-patellar tendon-bone graft, and the same knee was tested again. The kinematics of the reconstructed knees and the in situ forces in both grafts were determined. Results: The results demonstrated that both reconstructions were successful in limiting anterior tibial translation under anterior tibial loads. Furthermore, the mean in situ forces in the grafts under a 134-N anterior tibial load were restored to within 78% to 100% of that in the intact knee. However, in response to a combined rotational load, reconstruction with either of the two grafts was not as effective in reducing anterior tibial translation. This insufficiency was further revealed by the lower in situ forces in the grafts, which ranged from 45% to 65% of that in the intact knee. Conclusions: In current reconstruction procedures, the graft is placed close to the central axis of the tibia and femur, which makes it inadequate for resisting rotational loads. Our findings suggest that improved reconstruction procedures that restore the anatomy of the anterior cruciate ligament may be needed.

Double-bundle ACL reconstruction can improve rotational stability.

Double-bundle anterior cruciate ligament (ACL) reconstruction reproduces anteromedial and posterolateral bundles, and thus has theoretical advantages over conventional single-bundle reconstruction in controlling rotational torque in vitro. However, its superiority in clinical practice has not been proven. We analyzed rotational stability with three reconstruction techniques in 60 consecutive patients who were randomly divided into three groups (double-bundle, anteromedial single-bundle, posterolateral single-bundle). In the reconstructive procedure, the hamstring tendon was harvested and used as a free tendon graft. Followup examinations were performed 1 year after surgery. Anteroposterior laxity of the knee was examined with a KT-1000 arthrometer, whereas rotatory instability, as elicited by the pivot shift test, was assessed using a new measurement system incorporating three-dimensional electromagnetic sensors. Routine clinical evaluations, including KT examination, demonstrated no differences among the three groups. However, using the new measurement system, patients with double-bundle ACL reconstruction showed better pivot shift control of complex instability than patients with anteromedial and posterolateral single-bundle reconstruction.Level of Evidence: Level II, therapeutic study. See the Guideline for Authors for a complete description of levels of evidence.

Biomechanical Analysis of a Double-Bundle Posterior Cruciate Ligament Reconstruction

The objective of this study was to experimentally evaluate a single-bundle versus a double-bundle posterior cruciate ligament reconstruction by comparing the resulting knee biomechanics with those of the intact knee. Ten human cadaveric knees were tested using a robotic/universal force-moment sensor testing system. The knees were subjected to a 134-N posterior tibial load at five flexion angles. Three knee conditions were tested: 1) intact knee, 2) single-bundle reconstruction, and 3) double-bundle reconstruction. Posterior tibial translation of the intact knee ranged from 4.9 2.7 mm at 90° to 7.2 1.5 mm at full extension. After the single-bundle reconstruction, posterior tibial translation increased to 7.3 3.9 mm and 9.2 2.8 mm at 90° and full extension, respectively, while the corresponding in situ forces in the graft were up to 44 19 N lower than those in the intact ligament. Conversely, with double-bundle reconstruction, the posterior tibial translation did not differ significantly from the intact knee at any flexion angle tested. This reconstruction also restored in situ forces more closely than did the single-bundle reconstruction. These data suggest that a double-bundle posterior cruciate ligament reconstruction can more closely restore the biomechanics of the intact knee than can the single-bundle reconstruction throughout the range of knee flexion.

In Vivo Measurement of the Pivot-Shift Test in the Anterior Cruciate Ligament–Deficient Knee Using an Electromagnetic Device

Background The pivot-shift test is commonly used for assessing dynamic instability in anterior cruciate ligament—insufficient knees, which is related to subjective knee function, unlike static load-displacement measurement. Conventional measurements of 3-dimensional position displacement cannot assess such dynamic instability in vivo and produce comparable parameters. Not only 3-dimensional position displacement but also its 3-dimensional acceleration should be measured for quantitative evaluation of the pivot-shift test. Hypothesis Knees with a positive pivot-shift test result have increased tibial anterior translation and acceleration of its subsequent posterior translation, and they are correlated with clinical grading. Study Design Controlled laboratory study. Materials and Methods Thirty patients with isolated anterior cruciate ligament injury were included. Pivot-shift tests were evaluated under anesthesia manually and experimentally using an electromagnetic knee 6 degrees of freedom measurement system. From 60 Hz of 6 degrees of freedom data, coupled tibial anterior translation was calculated, and acceleration of posterior translation was computed by secondary derivative. Results All anterior cruciate ligament—deficient knees demonstrated a positive pivot-shift test result. The coupled tibial anterior translation was 7.7 and 15.6 mm in anterior cruciate ligament—intact and —deficient knees, respectively. The acceleration of posterior translation was —797 and —2001 mm/s 2, respectively. These differences were significant (P < .01). The coupled tibial anterior translation and acceleration of posterior translation in the anterior cruciate ligament—deficient knee were larger in correlation with clinical grading (P = .03 and P < .01, respectively). Conclusion The increase of tibial anterior translation and acceleration of subsequent posterior translation could be detected in knees with a positive pivot-shift result, and this increase was correlated to clinical grading. Clinical Relevance These measurements can be used for quantified evaluation of dynamic instability demonstrated by the pivot-shift test.

Evaluation of Hamstring Strength and Tendon Regrowth After Harvesting for Anterior Cruciate Ligament Reconstruction

Background It is generally thought that tissue regeneration and good functional recovery can be expected after anterior cruciate ligament reconstruction using the hamstring tendons. However, persistent strength deficit in deep knee flexion has also been reported. Hypothesis Morphologic regeneration of the harvested hamstring tendon is not necessarily associated with its functional recovery. Study Design Retrospective follow-up study. Method Twenty-eight patients who underwent anterior cruciate ligament reconstruction with hamstring graft were evaluated after a minimum period of 2 years. Status of tendon regrowth was assessed by magnetic resonance imaging. To specifically analyze the functional deficit after graft harvest, the isometric hamstring strength was examined in a sitting position at 90° of flexion and a prone position at 90° and 110° of flexion. Then, the strength data were correlated with the extent of tendon regeneration. Results In 22 of the 28 patients, a regrowth of the semitendinosus tendon was found, whereas regeneration of the gracilis tendon was observed in 13 patients. In the evaluation of hamstring strength, the isometric peak torque was reduced to 86.2%, 54.6%, and 49.1%, respectively, in the aforementioned 3 postures as compared with the contralateral side. Conclusions Significant functional deficit of hamstring strength remains regardless of morphologic regeneration.

Use of robotic technology for diathrodial joint research

Knowledge of diarthrodial joint mechanics and specific function of the ligaments are needed in order to understand injury mechanisms, improve surgical procedures and design better post-surgical rehabilitation protocols. To facilitate these needs, a robotic/universal force-moment sensor (UFS) testing system was developed to measure joint kinematics in multiple degree-of-freedom and the in situ forces in the ligaments. When operated in the position control mode, the testing system applies a known load to the intact joint while the motion and force data are recorded. After transection of a ligament, the recorded motion for the intact joint is repeated and new force and moment data is recorded by the UFS. Since the robot reproduces the identical initial position as well as path of joint motion before and after a ligament is transected, the in situ force in the ligament is the difference between the two sets of force and moment data. In force control mode, a known force is applied to the intact knee while the kinematics are recorded. After ligament transection, the same force is applied while the changes in kinematics are again recorded. Testing in this mode is similar to a clinical examination that diagnoses ligament injury. To date, this testing system has been used for experimental studies that examine the anterior cruciate ligament & posterior cruciate ligament of the knee and ligaments of the shoulder. A three-dimensional finite element model has also been constructed based on CT/MRI scans of a knee specimen and validated using data obtained with the testing system. Once in vivo kinematics (such as during gait analysis or throwing activities) are available, the robotic/UFS testing system can be programmed to reproduce these joint kinematics on young human cadaveric specimens in order to generate a database for in situ forces in the ligaments, or Ligament replacement grafts. With appropriate computational models, the stresses and strains in these tissues in vivo can also be determined. Potential applications of this combined approach include pre-operative surgical planning, improvement of surgical procedures as well as development of appropriate post-operative rehabilitation protocols.

A Comparison of Bone–Patellar Tendon–Bone and Bone–Hamstring Tendon–Bone Autografts for Anterior Cruciate Ligament Reconstruction

Background Most of the previous comparative studies between patellar tendon and hamstring tendon anterior cruciate ligament grafts compared grafts of different constructs fixed with different methods. Purpose To compare patellar tendon and hamstring tendon grafts with the same fixation method used to reconstruct the anterior cruciate ligament. Study Design Randomized controlled trial; Level of evidence, 1. Methods During the reconstructive procedure, the hamstring tendon graft was prepared as a bone-hamstring-bone graft; both bone-patellar tendon-bone and bone-hamstring-bone grafts were fixed with interference screws. Eighty consecutive patients who underwent anterior cruciate ligament reconstruction were randomly assigned to either bone-patellar tendon-bone or bone-hamstring-bone groups. Follow-up examinations were performed for at least 5 years postoperatively. Seventy-two of the 80 patients (37 patients in the bone-patellar tendon-bone group and 35 in the bone-hamstring-bone group) were evaluated, with a mean follow-up period of 87.0 and 80.8 months, respectively. Follow-up examinations were performed using the International Knee Documentation Committee knee ligament standard and subjective knee forms. Results The mean KT-1000 arthrometer evaluation results showed no significant difference between the bone-patellar tendon-bone and bone-hamstring-bone groups (1.2 ± 2.1 mm and 1.7 ± 1.4 mm, respectively; P =. 24). However, symptoms related to graft harvest (anterior kneeling pain) were more frequently observed in the bone-patellar tendon-bone group, and unsatisfactory results were correlated with severe kneeling pain in 3 patients from this group (P =. 0056). Significant hamstring muscle weakness without complaint of functional deficit was found in the bone-hamstring-bone group (P =. 0045). Conclusion Bone-hamstring-bone grafts were shown to reduce the risk of problems at the graft harvest site compared to bone-patellar tendon-bone grafts, with comparable results in the remaining clinical parameters tested.

The healing medial collateral ligament following a combined anterior cruciate and medial collateral ligament injury—a biomechanical study in a goat model

The ideal treatment of a combined anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injury to the knee is still debated. In particular, the question of whether reconstruction of the ACL can provide the knee with sufficient multidirectional stability to allow for effective MCL healing needs to be better elucidated. Therefore, the first objective of this study was to quantify the changes in the function of goat knees between time‐zero and 6 weeks following a combined ACL/MCL injury treated with ACL reconstruction. Using a robotic/universal force–moment sensor testing system, the kinematics of the knee and in situ forces in the ACL/ACL graft as well as in the sham‐operated and healing MCL were evaluated in response to (1) a 67 N anterior–posterior (A–P) tibial load and (2) a 5 N m varus–valgus (V–V) moment. The second objective was to evaluate the structural properties of the healing femur–MCL–tibia complex (FMTC) and the mechanical properties of the healing MCL at 6 weeks under uniaxial tension.