Akira Maeyama

Biomechanical comparison of different graft positions for single-bundle anterior cruciate ligament reconstruction

PurposeRecent reports have highlighted the importance of an anatomic tunnel placement for anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle ACL reconstruction on knee biomechanics.MethodsSixteen fresh-frozen cadaver knees were used. In one group (nxa0=xa08), the following techniques were used for knee surgery: (1) anteromedial (AM) bundle reconstruction (AM–AM), (2) posterolateral (PL) bundle reconstruction (PL–PL) and (3) conventional vertical single-bundle reconstruction (PL-high AM). In the other group (nxa0=xa08), anatomic mid-position single-bundle reconstruction (MID–MID) was performed. A robotic/universal force-moment sensor system was used to test the knees. An anterior load of 89xa0N was applied for anterior tibial translation (ATT) at 0°, 15°, 30° and 60° of knee flexion. Subsequently, a combined rotatory load (5xa0Nm internal rotation and 7xa0Nm valgus moment) was applied at 0°, 15°, 30° and 45° of knee flexion. The ATT and in situ forces during the application of the external loads were measured.ResultsCompared with the intact ACL, all reconstructed knees had a higher ATT under anterior load at all flexion angles and a lower in situ force during the anterior load at 60° of knee flexion. In the case of combined rotatory loading, the highest ATT was achieved with PL-high AM; the in situ force was most closely restored with MIDMID, and the in situ force was the highest AM–AM at each knee flexion angle.ConclusionAmong the techniques, AM–AM afforded the highest in situ force and the least ATT.

Biomechanical comparison of three anatomic ACL reconstructions in a porcine model.

PurposeDifferent tunnel configurations have been used for double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. However, controversy still exists as to whether three-tunnel DB with double-femoral tunnels and single-tibial tunnel (2F-1T) or with single-femoral tunnel and double-tibial tunnels (1F-2T) better restores intact knee biomechanics than single-bundle (SB) ACL reconstruction. The purpose was to compare the knee kinematics and in situ force in the grafts among SB and two types of three-tunnel DB ACL reconstructions performed in an anatomic fashion.MethodsTwenty-four porcine knees were subjected to an 89-N anterior tibial load (simulated KT-1000 test) at 30°, 60°, and 90° of flexion and to a 4-Nm internal tibial torque and 7-Nm valgus torque (simulated pivot-shift test) at 30° and 60° of flexion. The resulting knee kinematics and in situ force in the ACL or replacement grafts were measured using a robotic system for (1) ACL-intact, (2) ACL-deficient, and (3) three ACL reconstructed knees: SB; DB 2F-1T; and DB 1F-2T.ResultsDuring the simulated pivot-shift test, the DB grafts more closely restored the in situ force in the intact ACL at low flexion angle than the SB graft. There were no significant differences in knee kinematics between SB and DB ACL reconstruction. The DB 2F-1T reconstruction did not show a significant difference in knee kinematics or in situ force when compared to the DB 1F-2T technique.ConclusionThe in situ force in the ACL is better restored with an anatomic three-tunnel DB reconstruction in response to the simulated pivot-shift test at low flexion angle when compared to an anatomic SB reconstruction. Both three-tunnel DB ACL reconstructions performed in an anatomic fashion had similar biomechanical behavior. As long as it is performed anatomically, DB ACL reconstruction could be better alternative than SB ACL reconstruction, no matter which three-tunnel procedure, 2F-1T or 1F-2T, is used.

The effect of tunnel placement on rotational stability after ACL reconstruction: evaluation with use of triaxial accelerometry in a porcine model

PurposeConventional transtibial technique fails to restore the rotational knee stability in spite of successful anterior laxity, while anatomic anterior cruciate ligament reconstruction using the anteromedial portal technique has been developed expecting better rotational kinematics because of closer reproduction of the native anterior cruciate ligament anatomy. However, the rotational instability after those two procedures has not been fully examined especially in terms of dynamic component of the rotational stability. The purpose was to assess the effect of anatomic versus non-anatomic tunnel placement on rotational knee stability after anterior cruciate ligament reconstruction using triaxial accelerometry.MethodsSixteen porcine knees underwent a manual pivot-shift test at four different conditions: (1) anterior cruciate ligament intact, (2) anterior cruciate ligament deficient, (3) non-anatomic transtibial reconstruction, and (4) anatomic anteromedial portal reconstruction. The three-dimensional acceleration of knee motion during the pivot-shift test was recorded using a triaxial accelerometer.ResultsBoth anterior cruciate ligament reconstructions decreased significantly the acceleration of the pivot-shift test from the increased level in the anterior cruciate ligament-deficient condition. However, the transtibial technique fails to reach the intact level of acceleration, while the anteromedial portal technique reduced the acceleration to even less than the intact level.ConclusionThe transtibial anterior cruciate ligament reconstruction could not restore the dynamic rotational stability of the intact knee, whereas the anteromedial portal technique restored the dynamic rotational stability closer to the intact level.Level of evidenceIII.

Biomechanics of the Human Triple-Bundle Anterior Cruciate Ligament

PURPOSEnTo investigate the biomechanics of the intermediate (IM), anteromedial (AM), and posterolateral (PL) bundles in the human anterior cruciate ligament (ACL).nnnMETHODSnEighteen human cadaveric knees were tested with a robotic/universal force-moment sensor testing system. Anterior tibial translation (ATT) was determined under an 89-N anterior tibial load. Coupled ATT was determined under a combined rotatory load of 7-Nm valgus and 5-Nm internal rotation torque (pivot moment). Each bundles in situ forces were measured under identical external loading conditions.nnnRESULTSnUnder anterior load, the PL bundles in situ force was highest at 0° and decreased during flexion. Under the anterior load, the AM bundles in situ force was significantly higher than the IM and PL bundles force at 15°, 30°, and 60°. Under the pivot moment, the AM bundles in situ force was significantly higher than the PL and IM bundles force at 0° and 15°, and the IM bundle had the lowest in situ force at 0° but higher in situ force than the AM and PL bundles at 30° and 45°. IM and AM bundle removal increased ATT under the anterior load at all angles. Cutting the PL bundle after IM and AM bundle removal (whole ACL removal) significantly increased ATT under the anterior load at 0°, 15°, and 30° of knee flexion and increased coupled ATT under the pivot moment at 0° and 15°.nnnCONCLUSIONSnThe biomechanical role of each of the 3 ACL bundles (AM, IM, and PL) was measured with a robotic/universal force-moment sensor testing system. The AM bundle stabilized the knee against both the anterior and rotatory loads. The PL bundle stabilized the knee especially near full extension. The IM bundle supported the AM and PL bundles through all flexion angles, especially from 30° to 45°, against the rotatory load.nnnCLINICAL RELEVANCEnKnowledge of functions of the different ACL bundles will help improve ACL reconstruction techniques to enable restoration of normal knee function.

Measurement of the End-to-End Distances Between the Femoral and Tibial Insertion Sites of the Anterior Cruciate Ligament During Knee Flexion and With Rotational Torque

PURPOSEnThe aim of this study was to determine the end-to-end distance changes in anterior cruciate ligament (ACL) fibers during flexion/extension and internal/external rotation of the knee.nnnMETHODSnThe positional relation between the femur and tibia of 10 knees was digitized on a robotic system during flexion/extension and with an internal/external rotational torque (5 Nm). The ACL insertion site data, acquired by 3-dimensional scanning, were superimposed on the positional data. The end-to-end distances of 5 representative points on the femoral and tibial insertion sites of the ACL were calculated.nnnRESULTSnThe end-to-end distances of all representative points except the most anterior points were longest at full extension and shortest at 90°. The distances of the anteromedial (AM) and posterolateral (PL) bundles were 37.2 ± 2.1 mm and 27.5 ± 2.8 mm, respectively, at full extension and 34.7 ± 2.4 mm and 20.7 ± 2.3 mm, respectively, at 90°. Only 4 knees had an isometric point, which was 1 of the 3 anterior points. Under an internal torque, both bundles became longer with statistical meaning at all flexion angles (P = .005). The end-to-end distances of all points became longest with internal torque at full extension and shortest with an external torque at 90°.nnnCONCLUSIONSnOnly 4 of 10 specimens had an isometric point at a variable anterior point. The end-to-end distances of the AM and PL bundles were longer in extension and shorter in flexion.nnnCLINICAL RELEVANCEnThe nonisometric tendency of the ACL and the end-to-end distance change during knee flexion/extension and internal/external rotation should be considered during ACL reconstruction to avoid overconstraint of the graft.

A Biomechanical Comparison of 2 Femoral Fixation Techniques for Anterior Cruciate Ligament Reconstruction in Skeletally Immature Patients: Over-the-Top Fixation Versus Transphyseal Technique

PURPOSEnThe purpose of this study was to compare knee kinematics and in situ forces of the graft between 2 femoral fixation techniques of anterior cruciate ligament (ACL) reconstruction: the over-the-top (OTT) fixation and transphyseal (TP) techniques.nnnMETHODSnACL reconstruction in skeletally immature patients is a challenging procedure. Regarding the femoral fixation techniques, 2 methods are commonly used: the OTT fixation and TP techniques. Ten cadaveric knees (mean age, 57 years; range, 48 to 65 years) were tested with the robotic/universal force-moment sensor system by use of (1) an 89-N anterior tibial load at full extension and 15°, 30°, 60°, and 90° of knee flexion and (2) a combined 7-Nm valgus torque and 5-Nm internal tibial rotation torque at 15° and 30° of knee flexion.nnnRESULTSnBoth OTT and TP ACL reconstruction techniques closely restored the intact knee kinematics and had a significant reduction in anterior tibial translation under an anterior tibial load and in coupled anterior tibial translation under a combined rotatory load when compared with an ACL-deficient knee. When both ACL reconstruction techniques were compared, the only difference found was that the in situ force of the ACL graft reconstructed with the OTT technique in response to a combined rotatory load at 30° of flexion was significantly lower than the ACL graft reconstructed with the TP technique (5.3 ± 3.3 N and 10.7 ± 6.0 N, respectively; P = .013).nnnCONCLUSIONSnThis time 0 testing showed that both ACL reconstruction techniques, OTT and TP, can reproduce the kinematics of the intact knee in response to an anterior tibial load and a combined rotatory load.nnnCLINICAL RELEVANCEnBoth femoral fixation techniques exhibited comparable time 0 kinematics when subjected to simulated clinical examination loading conditions.

A comparison of dynamic rotational knee instability between anatomic single-bundle and over-the-top anterior cruciate ligament reconstruction using triaxial accelerometry

PurposeRecently, single-bundle (SB) anterior cruciate ligament (ACL) reconstruction has been advanced by the anatomic concept, but the biomechanical outcome of the anatomic method has not been fully investigated, especially for rotational instability. Anatomic SB and the single over-the-top procedures are the treatment of choice for primary cases and revision or skeletally immature cases, respectively. The purpose of this study was to investigate the dynamic rotational instability of anatomic SB and over-the-top reconstruction during a pivot shift test using triaxial accelerometry.MethodsEight fresh frozen human cadaveric knees were used in this study. Rotational instability measurement was conducted during a pivot shift test by the use of a triaxial accelerometer attached to the tibia. The tests were performed in the ACL-intact, ACL-deficient and ACL-reconstructed knees with two different procedures (anatomic SB and over-the-top). The acceleration in three directions and the magnitude of acceleration were measured to evaluate rotational instability and compare between four different knee states.ResultsThe overall magnitude of acceleration was significantly different (Pxa0<xa00.01) between the ACL-intact knees and the ACL-deficient knees. Both anatomic SB and over-the-top ACL reconstruction significantly reduced the overall magnitude of acceleration compared to the ACL-deficient knees, but still had larger accelerations compared to the ACL-intact knees. There was no significant difference for the overall magnitude of acceleration between anatomic SB and over-the-top reconstruction procedure.ConclusionOver-the-top reconstruction provides comparable result to anatomic SB reconstruction in terms of controlling the dynamic rotational stability. Over-the-top reconstruction might be one of the options for revision cases and in skeletally immature patients.

Biomechanical evaluation contribution of the acetabular labrum to hip stability

AbstractPurposenKnowledge of the effect of hip pathologies on hip biomechanics is important to the understanding of the development of osteoarthritis, and the contribution of the labrum to hip joint stability has had limited study. The purpose of this study was to evaluate the effect of labral injury to stability of the femoral head in the acetabular socket.MethodsTen cadaver hip specimens were tested using a robotic system under four different loading conditions: axial loading (80xa0N) along the femoral axis and axial loading (80xa0N) combined with either anterior, posterior or lateral loading (60xa0N). The hip states were examined were intact, with a 1.5xa0cm capsulotomy and with a 1xa0cm resection of the anterosuperior labrum.ResultsAt 30° of flexion, under axial load, the displacement of the hip with capsulotomy and labral resection (9.6xa0±xa02.5xa0mm) was significantly larger then the hip with capsulotomy alone (5.6xa0±xa04.1xa0mm, pxa0=xa00.005) and the intact hip (5.2xa0±xa03.8xa0mm, pxa0=xa00.005). Also, at 30° of flexion, the displacement under combined axial and anterior/posterior load was increased with capsulotomy and labral resection.ConclusionThe acetabular labrum provides stability to the hip joint in response to a distraction force and combined distraction and translation forces. One centimetre of labral resection caused significant displacement (“wobbling” effect) of the femoral head within the acetabulum with normal range of motion. Successful labral repair could be crucial for restoration of the hip biomechanics and prevention of coxarthrosis.

The Influence of Knee Flexion Angle for Graft Fixation on Rotational Knee Stability During Anterior Cruciate Ligament Reconstruction: A Biomechanical Study

PURPOSEnTo evaluate the effect of knee flexion angle for hamstring graft fixation, full extension (FE), or 30°, on acceleration of the knee motion during pivot-shift testing after either anatomic or nonanatomic anterior cruciate ligament (ACL) reconstruction using triaxial accelerometry.nnnMETHODSnTwo types of ACL reconstructions (anatomic and nonanatomic) using 2 different angles of knee flexion during graft fixation (FE and 30°) were performed on 12 fresh-frozen human knees making 4 groups: anatomic-FE, anatomic-30°, nonanatomic-FE, and nonanatomic-30°. Manual pivot-shift testing was performed at ACL-intact, ACL-deficient, and ACL-reconstructed conditions. Three-dimensional acceleration of knee motion was recorded using a triaxial accelerometer.nnnRESULTSnThe anatomic-30° group showed the smallest overall magnitude of acceleration among the ACL-reconstructed groups (Pxa0= .0039). There were no significant differences among the anatomic-FE group, the nonanatomic-FE group, and the nonantomic-30° group (anatomic-FE vs nonanatomic-FE, Pxa0= .1093; anatomic-FE vs nonanatomic-30°, Pxa0= .8728; and nonanatomic-FE vs nonanatomic-30°, Pxa0= .1093). After ACL transection, acceleration was reduced by ACL reconstruction with the exception of the nonanatomic-FE group that did not show a significant difference when compared with the ACL-deficient (Pxa0=xa0.4537).nnnCONCLUSIONSnThe anatomic ACL reconstruction with the graft fixed at 30° of knee flexion better restored rotational knee stability compared with FE. An ACL graft fixed with the knee at FE in anatomic position did not show a significant difference compared with the nonanatomic ACL reconstructions.nnnCLINICAL RELEVANCEnKnee flexion angle at the time of graft fixation for ACL reconstruction can be considered to maximize the rotational knee stability.

Coronal tibial anteromedial tunnel location has minimal effect on knee biomechanics

PurposeStudies have found anatomic variation in the coronal position of the insertion site of anteromedial (AM) bundle of the anterior cruciate ligament (ACL) on the tibia, which can lead to questions about tunnel placement during ACL reconstruction. The purpose of this study was to determine how mediolateral placement of the tibial AM graft tunnel in double-bundle ACL reconstructions affects knee biomechanics.MethodsTwo different types of double-bundle ACL reconstructions were performed. The AM tibial tunnel was placed at either the medial or lateral portion of tibial AM footprint. Nine cadaveric knees were tested with the robotic/universal force-moment sensor system with the use of (1) an 89.0-N anterior tibial load at full extension (FE), 30°, 60° and 90° of knee flexion and (2) a combined 7.0-Nm valgus torque and 5.0-Nm internal tibial rotation torque at FE, 15°, 30°and 45° of knee flexion.ResultsBoth medial (2.6u2009±u20091.2xa0mm) and lateral (1.6u2009±u20090.9xa0mm) double-bundle reconstructions reduced the anterior tibial translation (ATT) to less than the intact value (3.9u2009±u20090.7xa0mm) at FE. At all other flexion angles, there was no significant different in ATT between the intact knee and the reconstructions. At FE, the ATT for the medial AM reconstruction was different from that of the lateral AM construction and closer to the intact ACL value.ConclusionThe coronal tibial placement of the AM tunnel had only a slight effect on knee biomechanics. In patients with differing AM bundle coronal positions, the AM tibial tunnel can be placed anatomically at the native insertion site.