前十字韧带重建中的移植物位置偏移

目的 计算可吸收界面螺钉导致的移植物偏离隧道位移,探讨其对前十字韧带重建产生的影响.方法 19个新鲜尸体膝关节标本,随机选取5个,采用7 mm、8 mm、9 mm界面螺钉固定自体肌腱,测定偏移距离.另外14个膝关节分为等长组和解剖组,等长组膝关节测量界面螺钉固定后及校正位置的移植物拉长距离;解剖组膝关节于膝关节生物力学测试仪上分别测定ACL完整组、ACL缺失组、偏移组和校正组在134 N前向负荷下膝关节屈曲0°、15°、30°、60°和90°位的胫骨前向位移.结果 (1)肌腱偏移:直径7mm、8 mm、9mm的界面螺钉分别使移植物偏移(2.36±0.11)mm、(2.72±0.06)mm、(3.00±0.06)mm.(2)等长性:初始拉长小于3 mm,偏移拉长大于3 mm,校正拉长小于3 mm.(3)生物力学:屈膝0°、15°位,ACL完整组与偏移组、校正组差异无统计学意义.屈膝30°、60°、90°位ACL完整组与其他各组比较差异均有统计学意义,屈膝30°、60°位偏移组与校正组比较差异有统计学意义.结论 无论等长重建还是解剖重建,界面螺钉均影响移植物的股骨隧道口位置.前十字韧带重建预先校正股骨隧道口位置,移植物基本会处于预先的理想位置.

Abstract：

Objective To investigate the impact of graft position shift on anterior cruciate ligament reconstruction induced by femoral fixation of interference screw. Methods Nineteen fresh cadaveric knees were used and assigned to three groups. 1) Study of graft position shift: 5 knees were randomly selected, interference screws of 7 mm, 8 mm and 9 mm were used in autologous tendon fixation, then the graft position shift were measured. 2) Study of isometry: 7 knees were randomly divided into the isometric reconstruction group (D group). In the D group, Retrobutton, interference screw and interference screw in location-corrected bone tunnel were used respectively as fixation. The isometry of grafts was evaluated. 3) Study of tibia anterior translation: 7 knees were randomly divided into the anatomic reconstruction group (J group). In the J group,the tibia anterior translation was measured in four different conditions in the same joint: intact knee joint,knee joint without ACL, ACL anatomic reconstruction by interference screw fixation, and ACL anatomic reconstruction by interference screw fixation with corrected bone tunnel location. Results 1) With 7 mm, 8mm and 9 mm interference screw fixation, graft position shift were (2.36±0.11) mm, (2.72±0.06) mm and (3.00±0.06) mm respectively. 2) Graft length change: graft length change in Retrobutton group and corrected bone tunnel group were less than 3 mm, while graft length change in those fixed with interference screw were stretched in more than 3 mm. 3) Study of tibia anterior translation: there was no difference among the intact group, the anatomic group and the corrected group at 0° and 15°. However, the difference was found between the intact group and other groups at 30°、60° and 90° of flexion, as well as between these two reconstructed methods at 20° joint flexion (P＜0.05). Conclusion In both isometric and anatomic ACL reconstruction with interference screw, the graft is pushed tightly toward the femoral tunnel wall, which shifts the graft away from the desired position. In our study we find out that the corrected location of the femoral bone tunnel significantly improves the isometry of ACL reconstruction and anatomic reconstruction.     

Anterior cruciate ligament reconstruction stability with continuous passive motion. The role of isometric graft placement.

A comparison was made of the stability of isometric versus nonisometric anterior cruciate ligament (ACL) reconstructions when subjected to immediate postoperative continuous passive motion (CPM). Anterior cruciate ligament reconstructions were performed on 13 anatomic specimen knees using bone/patellar tendon/bone grafts. Nine ACL substitutions were considered isometric with maximum graft length changes of less than 1 mm. Four ACL substitutions were nonisometric with graft length changes of 3 mm or greater resulting from tightening in flexion. The specimens were subjected to CPM through 0 degrees-95 degrees knee flexion. Knee stability was remeasured with a knee arthrometer at three and 14 days after beginning CPM. All four nonisometric specimens had failed within three days, with increased anterior laxity of 2-9 mm in both the Lachman (20 degrees) and anterior drawer (90 degrees) positions. All nine isometric reconstructions successfully retained pre-CPM anterior stability within 1 mm after 14 days of CPM. This investigation illustrates the importance of isometric graft placement for ACL reconstruction success. Continuous passive motion does not appear to adversely affect immediate ACL-substitute integrity or fixation if graft placement is isometric (less than 1 mm of graft excursion through 0 degrees-110 degrees of knee motion). Continuous passive motion may cause graft deformation, fixation failure, or both, with resultant loss of knee stability if the graft is not isometrically positioned (greater than 3 mm of graft excursion resulting from tightening in flexion).     

Effects of femoral tunnel placement on knee laxity and forces in an anterior cruciate ligament graft.

The purpose of this study was to measure the effects of variation in placement of the femoral tunnel upon knee laxity, graft pretension required to restore normal anterior-posterior (AP) laxity and graft forces following anterior cruciate ligament (ACL) reconstruction. Two variants in tunnel position were studied: (1) AP position along the medial border of the lateral femoral condyle (at a standard 11 o'clock notch orientation) and (2) orientation along the arc of the femoral notch (o'clock position) at a fixed distance of 6-7 mm anterior to the posterior wall. AP laxity and forces in the native ACL were measured in fresh frozen cadaveric knee specimens during passive knee flexion-extension under the following modes of tibial loading: no external tibial force, anterior tibial force, varus-valgus moment, and internal-external tibial torque. One group (15 specimens) was used to determine effects of AP tunnel placement, while a second group (14 specimens) was used to study variations in o'clock position of the femoral tunnel within the femoral notch. A bone-patellar tendon-bone graft was placed into a femoral tunnel centered at a point 6-7 mm anterior to the posterior wall at the 11 o'clock position in the femoral notch. A graft pretension was determined such that AP laxity of the knee at 30 deg of flexion was restored to within 1 mm of normal; this was termed the laxity match pretension. All tests were repeated with a graft in the standard 11 o'clock tunnel, and then with a graft in tunnels placed at other selected positions. Varying placement of the femoral tunnel 1 h clockwise or counterclockwise from the 11 o'clock position did not significantly affect any biomechanical parameter measured in this study, nor did placing the graft 2.5 mm posteriorly within the standard 11 o'clock femoral tunnel. Placing the graft in a tunnel 5.0 mm anterior to the standard 11 o'clock tunnel increased the mean laxity match pretension by 16.8 N (62%) and produced a knee which was on average 1.7 mm more lax than normal at 10 deg of flexion and 4.2 mm less lax at 90 deg. During passive knee flexion-extension testing, mean graft forces with the 5.0 mm anterior tunnel were significantly higher than corresponding means with the standard 11 o'clock tunnel between 40 and 90 deg of flexion for all modes of constant tibial loading. These results indicate that AP positioning of the femoral tunnel at the 11 o'clock position is more critical than o'clock positioning in terms of restoring normal levels of graft force and knee laxity profiles at the time of ACL reconstruction.     

Reconstructive interventions of the posterior cruciate ligament--experimental studies of isometric aspects. Part II: Studies of the posterior cruciate ligament replacement model]

Isometric positioning of the posterior cruciate ligament (PCL) graft is important for successful reconstruction of the PCL-deficient knee. This study documents the relationship between graft placement and changes in intra-articular graft length during passive range of motion of the knee. In eight cadaveric knees the PCL was identified and cut. The specimens were mounted in a stabilizing rig. PCL reconstruction was performed using a 9-mm-thick synthetic cord that was passed through tunnels 10 mm in diameter. Three different femoral graft placement sites were evaluated: (1) in four specimens the tunnel was located around the femoral isometric point, (2) in two specimens the tunnel was positioned over the guide wire 5 mm anterior to the femoral isometric point, (3) in two specimens the tunnel was positioned over the guide wire 5 mm posterior to the isometric femoral point. In all knees only one tibial tunnel was created around the isometric tibial point. The location of the isometric points was described in part I of the study. The proximal end of the cord was fixed to the lateral aspect of the femur. Distally the cord was attached to a measuring unit. The knees were flexed from 0 degree to 110 degrees, and the changes in the graft distance between the femoral attachment sites were measured in 10 degrees steps. Over the entire range of motion measured the femoral tunnels positioned around the isometric point produced femorotibial distance changes of within 2 mm. The anteriorly placed tunnels produced considerable increases in femorotibial distance with knee flexion, e.g. about 8 mm at 110 degrees of flexion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of the ACL and ACL graft forces before and after ACL reconstruction an in-vitro robotic investigation

Background?Long-term follow-up studies have indi-cated that there is an increased incidence of arthrosis following anterior cruciate ligament (ACL) reconstruc-tion, suggesting that the reconstruction may not repro-duce intact ACL biomechanics. We studied not only the magnitude but also the orientation of the ACL and ACL graft forces

Methods?10 knee specimens were tested on a robotic testing system with the ACL intact, deficient, and recon-structed (using a bone-patella tendon-bone graft). The magnitude and orientation of the ACL and ACL graft forces were determined under an anterior tibial load of 130?N at full extension, and 15, 30, 60, and 90° of flexion. Orientation was described using elevation angle (the angle formed with the tibial plateau in the sagit-tal plane) and deviation angle (the angle formed with respect to the anteroposterior direction in the transverse plane)

Results?ACL reconstruction restored anterior tibial translation to within 2.6?mm of that of the intact knee under the 130-N anterior load. Average internal tibial rotation was reduced after ACL reconstruction at all flexion angles. The force vector of the ACL graft was significantly different from the ACL force vector. The average values of the elevation and deviation angles of the ACL graft forces were higher than that of the intact ACL at all flexion angles

Interpretation?Contemporary single bundle ACL reconstruction restores anterior tibial translation under anterior tibial load with different forces (both magni-tude and orientation) in the graft compared to the intact ACL. Such graft function might alter knee kinematics in other degrees of freedom and could overly constrain the tibial rotation. An anatomic ACL reconstruction should reproduce the magnitude and orientation of the intact ACL force vector, so that the 6-degrees-of-freedom knee kinematics and joint reaction forces can be restored.     

Interaction between the ACL graft and MCL in a combined ACL+MCL knee injury using a goat model

The optimal treatment for the MCL in the combined ACL and MCL-injured knee is still controversial. Therefore, we designed this study to examine the mechanical interaction between the ACL graft and the MCL in a goat model using a robotic/universal force-moment sensor testing system. The kinematics of intact, ACL-deficient, ACL-reconstructed, and ACL-reconstructed/ MCL-deficient knees, as well as the in situ forces in the ACL, ACL graft, and MCL were determined in response to two external loading conditions: 1) anterior tibial load of 67 N and 2) valgus moment of 5 N-m. With an anterior tibial load, anterior tibial translation in the ACL-deficient knee significantly increased from 2.0 and 2.2 mm to 15.7 and 18.1 mm at 30 degrees and 60 degrees of knee flexion, respectively. The in situ forces in the MCL also increased from 8 to 27 N at 60 degrees of knee flexion. ACL reconstruction reduced the anterior tibial translation to within 2 mm of the intact knee and significantly reduced the in situ force in the MCL to 17 N. However, in response to a valgus moment, the in situ forces in the ACL graft increased significantly by 34 N after transecting the MCL. These findings show that ACL deficiency can increase the in situ forces in the MCL while ACL reconstruction can reduce the in situ forces in the MCL in response to an anterior tibial load. On the other hand, the ACL graft is subjected to significantly higher in situ forces with MCL deficiency during an applied valgus moment. Therefore, the ACL-reconstructed knee with a combined ACL and MCL injury should be protected from high valgus moments during early healing to avoid excessive loading on the graft.     

前交叉韧带股骨等距重建位置的比较

目的 :比较模拟生理负荷条件下前交叉韧带股骨重建位置的等距特性。方法 :7具新鲜冷冻尸体膝关节标本 ,在前交叉韧带胫骨附着区取 3点以及胫骨附着区取 5点分别钻骨隧道 ,通过钢丝和等距测量器施加初负荷 ,检测膝关节屈曲过程中胫骨和股骨隧道间的距离变化。结果 :膝关节从 0～ 90°屈曲过程中 ,股骨韧带附着区中点、上点和后点与胫骨附着区 5点间呈等距变化 ,但股骨韧带附着区中点、上点与胫骨附着区 5点间距离变化具有组内显著性差异。结论 :股骨韧带附着区后点是理想的等距重建点。     

Kniegelenklaxizität beim vorderen Kreuzbandersatz

Background

The use of interference screws for femoral graft fixation in anterior cruciate ligament (ACL) reconstruction with hamstring grafts can result in rotation of the graft around the screw leading to changes in the final position of the graft within the bone tunnel.

Material and methods

In a prospective study 107 patients (54 right and 53 left knees) underwent ACL reconstruction with a hamstring tendon autograft. Femoral fixation of the graft was performed with a standard right-thread screw in all cases. Patients were assessed at 6 months postoperatively with the international knee documentation committee (IKDC) standard evaluation including instrumented laxity measurements and the results were compared between right and left knees.

Results

A significantly higher postoperative anterior laxity was observed in left knees with a negative Lachman test in only 64 % of the cases compared with 87 % in the group of right knees. Accordingly, instrumented laxity measurements of the reconstructed knee compared with the contralateral knee revealed significant differences between left and right knees (left knees 1.8±1.2 mm and right knees 1.0±1.4 mm)

Conclusions

This study demonstrates the importance of femoral graft positioning and its sensitivity to multiple influencing factors. The use of standard right-thread interference screws for femoral graft fixation in the mirrored situation of right and left knees may produce a systematic error in ACL reconstruction. Due to a possible rotation of the graft around the screw, the final position of the transplant may vary thus leading to significant changes in anterior translation of the operated knee.     

In vitro comparison of elongation of the anterior cruciate ligament and single- and dual-tunnel anterior cruciate ligament reconstructions.

This study evaluated strain in the normal anterior cruciate ligament (ACL) and compared it to four different double-strand hamstring tendon reconstructive techniques. Seventeen fresh-frozen knees from 11 cadavers were tested. The strain in the anteromedial and posterolateral bands of the native ACL and their equivalents in four autograft techniques were measured using differential variable reluctance transducers. The anteromedial band of the intact ACL shortened from 0 degree -30 degrees of flexion, then lengthened to 120 degrees; the posterolateral band of the intact ACL shortened from 0 degree - 120 degrees of flexion. Following ACL excision, these knees underwent reconstruction with double-strand hamstring tendons with either single tibial and femoral tunnels, single tibial and dual femoral tunnels, dual tibial and single femoral tunnels, or dual tibial and dual femoral tunnels. With the exception of the dual-band, dual-tunnel technique, all of the procedures placed greater strain on the reconstructive tissues than was observed on the native ACL, after approximately 30 degrees of flexion. These results indicate that dual-band hamstring tendon reconstructions placed with single tibial and femoral tunnels do not address the complexity of the entire ACL. Rather, these procedures appear to only duplicate the effect of the anteromedial band, while perhaps overconstraining the joint as a result of its inability to reproduce the function of the posterolateral band. During rehabilitation following ACL reconstruction, therefore, only from 0 degree - 30 degrees of the graft tissues are not significantly strained. Dual tibial and femoral tunnel techniques should be evaluated further to more closely recreate knee kinematics following ACL reconstruction.     

Two-bundle posterior cruciate ligament reconstruction: how bundle tension depends on femoral placement

BACKGROUND: Clinically, one-bundle posterior cruciate ligament reconstructions frequently result in the return of abnormal posterior translation. We hypothesized that the return of posterior translation is caused by a nonuniform distribution of load among the graft fibers. The purpose of the present study was to determine how the femoral attachment location of the second bundle of a two-bundle posterior cruciate ligament reconstruction affects the anterior bundle tension and the load distribution between the graft bundles. METHODS: One and two-bundle posterior cruciate ligament reconstructions (one one-bundle type and three two-bundle types) were performed in nineteen cadaveric knees. The grafts were tensioned to restore posterior translation to within +/-1 mm of that of the intact knee at 90 degrees of flexion while a 100-N posterior force was applied to the proximal part of the tibia. For each reconstruction, the total graft tension was a minimum of 2.3 times larger than the applied posterior force. Bundle tension and knee motions were measured as the knee was cycled from 5 degrees to 120 degrees of flexion while a 100-N posterior force was applied. Analysis of variance was used to compare the four reconstructions, and post hoc testing was performed with use of Fischer's protected least significant difference method. RESULTS: Two-bundle reconstructions involving a middle-distal or middle-middle second bundle significantly reduced the tension in the anterior bundle in comparison with the tension in the one-bundle (anterior-distal) reconstruction. The peak anterior-bundle tensions with the middle-distal and middle-middle second bundles were 43% and 37% less than the peak bundle tension for the one-bundle reconstruction (p < 0.001 and p = 0.002, respectively). With the exception of the average bundle tension, the tension parameters calculated for the middle bundle decreased as the distance from the articular cartilage increased. The peak tensions for the middle-middle and middle-proximal bundles were 32% and 61% less than that for the middle-distal bundle (p = 0.028 and p = 0.001, respectively). CONCLUSIONS: The femoral position of the second bundle significantly affected the tension in the anterior bundle and the load distribution. A second bundle placed in a middle or distal position resulted in a significant reduction in anterior bundle tension and in cooperative load-sharing (with the bundles functioning together). A proximal second bundle resulted in reciprocal loading (with one bundle functioning in flexion and one in extension), but the tension in the anterior bundle was not different from the tension in the one-bundle reconstruction.     

Comparison of the ACL and ACL graft forces before and after ACL reconstruction: an in-vitro robotic investigation

Background Long-term follow-up studies have indi-cated that there is an increased incidence of arthrosis following anterior cruciate ligament (ACL) reconstruc-tion, suggesting that the reconstruction may not repro-duce intact ACL biomechanics. We studied not only the magnitude but also the orientation of the ACL and ACL graft forces

Methods 10 knee specimens were tested on a robotic testing system with the ACL intact, deficient, and recon-structed (using a bone-patella tendon-bone graft). The magnitude and orientation of the ACL and ACL graft forces were determined under an anterior tibial load of 130 N at full extension, and 15, 30, 60, and 90° of flexion. Orientation was described using elevation angle (the angle formed with the tibial plateau in the sagit-tal plane) and deviation angle (the angle formed with respect to the anteroposterior direction in the transverse plane)

Results ACL reconstruction restored anterior tibial translation to within 2.6 mm of that of the intact knee under the 130-N anterior load. Average internal tibial rotation was reduced after ACL reconstruction at all flexion angles. The force vector of the ACL graft was significantly different from the ACL force vector. The average values of the elevation and deviation angles of the ACL graft forces were higher than that of the intact ACL at all flexion angles

Interpretation Contemporary single bundle ACL reconstruction restores anterior tibial translation under anterior tibial load with different forces (both magni-tude and orientation) in the graft compared to the intact ACL. Such graft function might alter knee kinematics in other degrees of freedom and could overly constrain the tibial rotation. An anatomic ACL reconstruction should reproduce the magnitude and orientation of the intact ACL force vector, so that the 6-degrees-of-freedom knee kinematics and joint reaction forces can be restored.     

Method for setting total graft force and load sharing in augmented ACL grafts

The objective of this study was to develop a method for obtaining a controllable and reproducible immediate postoperative mechanical state in a knee with an anterior cruciate ligament (ACL) reconstruction. This method, called the force-setting technique, was demonstrated using a composite graft consisting of the middle third of the patellar tendon with bone blocks (PT) and the ligament augmentation device (LAD). The total graft force was set to match the force in the intact ACL at 30 degrees flexion with the knee under the same standardized external load, while at the same time the load sharing between the biologic and augmentation components was controlled. The total graft force was set to match the ACL force three separate times in each knee, with ratios of load sharing set at the following levels: 50% PT-50% LAD, 25% PT-75% LAD, and 75% PT-25% LAD. ACL, PT, LAD, and collateral forces were measured using buckle transducers, and three-dimensional knee motion was measured using an instrumented spatial linkage as 90 N anteriorly directed tibial loads were applied to eight specimens at 0 degree, 30 degrees, 60 degrees, and 90 degrees flexion with an intact ACL, an excised ACL, and the three load-sharing reconstruction states. The total graft force could be consistently set to within an average of 2% of the intact ACL force at 30 degrees flexion, and load sharing between the graft segments could be set to within an average of 5.1% of the desired ratio at 30 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of the iliotibial band on knee biomechanics during a simulated pivot shift test.

The purpose of this study was to evaluate the effect of the iliotibial band (ITB) on the kinematics of anterior cruciate ligament (ACL) intact and deficient knees and also on the in situ force in the ACL during a simulated pivot shift test. A combination of 10 N-m valgus and 5 N-m internal tibial torques was applied to 10 human cadaveric knees at 15 degrees, 30 degrees, 45 degrees, and 60 degrees of flexion using a robotic/universal force-moment sensor testing system. ITB forces of 0, 22, 44, and 88 N were also applied. An 88 N ITB force significantly decreased coupled anterior tibial translation of ACL deficient knees by 32%-45% at high flexion angles, but did not have a significant effect at low flexion angles. Further, an 88 N ITB force significantly decreased in situ forces in the ACL at all flexion angles by 23%-40%. These results indicate that during the pivot shift test, the ITB can improve tibial reduction at high flexion angles while not affecting subluxation at low flexion angles. Additionally, the action of the ITB as an ACL agonist suggests that its use as an ACL graft might hinder knee stability in response to rotatory load.     

负荷条件下前交叉韧带的股骨重建位置

目的　探讨模拟生理负荷条件下前交叉韧带股骨等距重建位置。方法　 7具新鲜冷冻膝关节标本 ,在前交叉韧带股骨附着区取 5点以及胫骨附着区中点分别钻骨隧道 ,通过钢丝和等距测量器施加初负荷 ,检测膝关节屈曲过程中胫骨和股骨隧道间的距离变化。结果　膝关节 0°～ 90°屈曲过程中 ,股骨韧带附着区中点、后点和下点与胫骨附着区中点间呈等距变化 ,而股骨韧带附着区前点和上点与胫骨附着区中点间距离变化超过生理等距界限。结论　股骨韧带附着区后点和下点是理想的前交叉韧带股骨等距重建点。股骨韧带附着区中点、后点和下点的连线构成了前交叉韧带的股骨等距重建区。     

Revision anterior cruciate ligament reconstruction using the lateral third of the ipsilateral patellar tendon after failure of a central-third graft: a preliminary report on 10 patients

Long-term outcomes were reported for 10 (77%) of 13 cases of revision anterior cruciate ligament (ACL) reconstruction using the lateral third of the ipsilateral patellar tendon as a graft. All primary ACL reconstructions were ipsilateral central-third bone-patellar tendon-bone graft procedures. Mean age at follow-up was 30.7 years, and mean time from revision ACL surgery to follow-up was 42.9 months. At follow-up, average KT-1000 difference between knees was 2.4 mm. All patients had a negative pivot shift, extension within 5 degrees of the contralateral knee, and flexion within 15 degrees. Mean bilateral comparison ratios for isokinetic strength and hop testing were: extension, 83.5%; flexion, 96%; and single-leg hop 96.9%. No patella fractures or tendon ruptures had occurred. All patients had returned to their previous work level, and 8 of the 10 patients could participate in at least "moderate" sports activities (e.g., skiing and tennis). The results were comparable to published outcome reports for both primary and revision ACL reconstruction. The lateral third of the ipsilateral patellar tendon is a good graft option for revision ACL reconstruction.     

Single– versus two–femoral socket anterior cruciate ligament reconstruction technique: Biomechanical analysis using a robotic simulator

Purpose: Although anterior cruciate ligament (ACL) reconstruction with multistrand autogenous hamstring tendons has been widely performed using a single femoral socket (SS), it is currently advocated to individually reconstruct 2 bundles of the ACL using 2 femoral sockets (TS). However, the difference in biomechanical characteristics between them is unknown. The objective of this study was to clarify their biomechanical differences. Type of Study: This is a cross-over trial using cadaveric knees. Methods: Seven intact human cadaveric knees were mounted in a robotic simulator developed in our laboratory. By applying anterior and posterior tibial load up to ± 100 N at 0°, 15°, 30°, 60°, and 90° of flexion, tibial displacement and load were recorded. After cutting the ACL, the knees underwent ACL reconstruction using TS, followed by that using SS, with 44 or 88 N of initial grafts tension at 20° of flexion. The above-mentioned tests were performed on each reconstructed knee. Results: The tibial displacement in the TS technique was significantly smaller than that in the SS at smaller flexion angles in response to anterior and posterior tibial load of ± 100 N, and the in situ force in the former was significantly greater than that in the latter at smaller flexion angles. Furthermore, in the TS technique, the posterolateral graft acted dominantly in extension, while the anteromedial graft mainly resisted against anterior tibial load in flexion. However, in the SS technique, the anteriorly located graft functioned more predominantly than the posteriorly located graft at all flexion angles. Conclusions: The ACL reconstruction via TS using quadrupled hamstring tendons provides better anterior-posterior stability compared with the conventional reconstruction using a single socket.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 7 (September), 2001: pp 708–716     

Loss of knee extension after anterior cruciate ligament reconstruction: effects of knee position and graft tensioning

BACKGROUND: Loss of knee extension has been reported by many authors to be the most common complication following anterior cruciate ligament reconstruction. The objective of this in vitro study was to determine the effect, on loss of knee extension, of the knee flexion angle and the tension of the bone-patellar tendon-bone graft during graft fixation in a reconstruction of an anterior cruciate ligament. METHODS: The anterior cruciate ligament was reconstructed with use of tibial and femoral bone tunnels placed in the footprint of the native anterior cruciate ligament in ten cadavers. The graft was secured with an initial tension of either 44 N (10 lb) or 89 N (20 lb) applied with the knee at 0 degrees or 30 degrees of flexion. The knee flexion angle was measured with use of digital images following graft fixation. RESULTS: Tensioning of the graft at 30 degrees of knee flexion was associated with loss of knee extension in this cadaver model. Graft tension did not affect knee extension under the conditions tested. CONCLUSIONS: The results suggest that one of the common causes of the loss of full knee extension may be diminished if the graft is secured in full knee extension when the tibial and femoral tunnels are placed in the footprint of the native anterior cruciate ligament. More importantly, even when the femoral and tibial tunnels are placed in the femoral and tibial footprints of the native anterior cruciate ligament, fixing a graft in knee flexion can result in the loss of knee extension.     

MRI analysis of in vivo meniscal and tibiofemoral kinematics in ACL-deficient and normal knees.

The objectives of this study were to analyze simultaneously meniscal and tibiofemoral kinematics in healthy volunteers and anterior cruciate ligament (ACL)-deficient patients under axial load-bearing conditions using magnetic resonance imaging (MRI). Ten healthy volunteers and eight ACL-deficient patients were examined with a high-field, closed MRI system. For each group, both knees were imaged at full extension and partial flexion ( approximately 45 degrees ) with a 125N compressive load applied to the foot. Anteroposterior and medial/lateral femoral and meniscal translations were analyzed following three-dimensional, landmark-matching registration. Interobserver and intraobserver reproducibilities were less than 0.8 mm for femoral translation for image processing and data analysis. The position of the femur relative to the tibia in the ACL-deficient knee was 2.6 mm posterior to that of the contralateral, normal knee at extension. During flexion from 0 degrees to 45 degrees , the femur in ACL-deficient knees translated 4.3 mm anteriorly, whereas no significant translation occurred in uninjured knees. The contact area centroid on the tibia in ACL-deficient knees at extension was posterior to that of uninjured knees. Consequently, significantly less posterior translation of the contact centroid occurred in the medial tibial condyle in ACL-deficient knees during flexion. Meniscal translation, however, was nearly the same in both groups. Axial load-bearing MRI is a noninvasive and reproducible method for evaluating tibiofemoral and meniscal kinematics. The results demonstrated that ACL deficiency led to significant changes in bone kinematics, but negligible changes in the movement of the menisci. These results help explain the increased risk of meniscal tears and osteoarthritis in chronic ACL deficient knees.     

One- and two-strand posterior cruciate ligament reconstructions: cyclic fatigue testing.

This study examined how one- and two-strand posterior cruciate ligament (PCL) reconstructions resist the return of posterior translation during repetitive knee cycling. The femoral attachment of the one-strand graft and the anterior strand of the two-strand (AD2) grafts were located within the anterior one-third of the femoral PCL footprint. The second strand was placed within the middle third of the femoral footprint in one of three locations: middle-distal (MD), middle-middle (MM), or middle-proximal (MP). During repetitive knee cycling from 5 degrees to 120 degrees flexion with a 100 N posterior force, the intact knee had less than 1mm of residual posterior translation after 2048 flexion-extension cycles. Under similar cyclic conditions, the AD2-MM reconstruction achieved the most cycles before failure; however, this two-strand configuration failed in less than 700 cycles. The other reconstructions, either one strand or two strand, failed in less than 350 cycles. The surface failure location for 19 of 25 graft strands was within the femoral one-third of the strand. We concluded that one- and two-strand reconstructions under moderate loading and a range of motion from 5 degrees to 120 degrees flexion have an unacceptably high cyclic failure rate suggesting modifications of the allowable postoperative knee flexion and loading.