Double-bundle anterior cruciate ligament reconstruction using two different suspensory femoral fixation: a technical note

We describe a novel double-bundle reconstruction method for ACL deficient knee. Grafts are tibialis allograft for AMB (anteromedial bundle) and semitendinosus autograft for PLB (posterolateral bundle). Femoral fixations are done by Bio-TransFix for AMB and EndoButton for PLB. Tibial fixations are done by Bio-interference screw for AMB at 60–70° knee flexion and secure the PLB and remnant AMB graft simultaneously onto anteromedial aspect of tibia at 10–20° knee flexion with spiked washer and screw. With our technique, graft lengths are not restricted and we provide strong femoral and tibial fixation if it is compared with previous techniques.     

Contribution of thin slice (1 mm) oblique coronal proton density-weighted MR images for assessment of anteromedial and posterolateral bundle damage in anterior cruciate ligament injuries

Purpose

To evaluate the diagnostic efficacy of using additional oblique coronal 1 mm proton density-weighted (PDW) MR imaging of the knee for detection and grading anterior cruciate ligament (ACL), anteromedial bundle (AMB) and posterolateral bundle (PLB) injuries.

Materials and methods

We prospectively assessed preoperative MR images of 50 patients (36 men, 14 women; age range, 18–62 years). First, we compared the diagnostic performance of routine sagittal (3 mm) and additional oblique coronal images (1 mm) for ACL tears. Then, we compared the tear types (AMB or PLB) and grade presumed from oblique coronal MR imaging with arthroscopy.

Results

Arthroscopy revealed ACL tear in 24 (48%) patients. There was significant difference between sagittal images and arthroscopy results for ACL tear recognition (p < 0.001). No significant difference was detected for oblique coronal images when compared with arthroscopy results (p = 0.180). Sensitivity and specificity values for ACL tear diagnosis were 37.04% and 95.65% for sagittal images; 74.07% and 91.30% for oblique coronal images. There was no significant difference between arthroscopy and oblique coronal MR images in grading AMB and PLB injuries (p > 0.05).

Conclusion

Addition of thin slice oblique coronal images to conventional sequences could better contribute to better verifying the presence of ACL tear and in determining its grade.     

Correlation between knee laxity and graft appearance on magnetic resonance imaging after double-bundle hamstring graft anterior cruciate ligament reconstruction

BACKGROUND: In recent years, double-bundle (anteromedial bundle [AMB], posterolateral bundle [PLB]) anterior cruciate ligament reconstruction has developed into an accepted practical surgical procedure; therefore, its efficacy needs to be established. HYPOTHESIS: Multiple-sliced 2-dimensional magnetic resonance imaging allows evaluation of each bundle separately. Both bundles are important for knee stability, and each bundle has a role in the prevention of knee instability. Knee laxity testing will correlate with the magnetic resonance imaging appearance of the individual graft bundles. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 97 double-bundle anterior cruciate ligament reconstructions were evaluated 1 year after surgery, including side-to-side difference of KT-2000 arthrometer and pivot shift test. T2-weighted 2-dimensional magnetic resonance images were captured in the middle plane of each bundle to express magnetic resonance signals of each bundle. The magnetic resonance signals were divided into 3 grades: grade I, low-intensity signal; grade II, high-intensity signal within 50%; and grade III, high-intensity signal greater than 50%. RESULTS: Anterior laxity in AMB grade II (PLB I, 3.5 +/- 1.7 mm; PLB II, 4.5 +/- 1.9 mm) was significantly larger than in AMB grade I (PLB I, 1.9 +/- 1.7 mm; PLB II, 2.1 +/- 1.7 mm) with statistical difference (P = .025 in PLB I; P = .002 in PLB II). A positive rate in pivot shift test in PLB II (48%) was significantly larger than in PLB I (21%) with statistical difference (P = .031). CONCLUSIONS: Varying magnetic resonance signals according to the bundle indicate role differences of each bundle in knee stability. These results imply that the AMB has a major role in preventing anterior translation of the tibia and the PLB has a major role in preventing anterolateral rotatory instability.     

前交叉韧带部分断裂的诊治

目的 :探讨前交叉韧带 (anteriorcruciateligament,ACL)部分断裂的诊断方法和治疗方式。方法 :2 0 0 0年 3月～ 2 0 0 2年 6月收治ACL部分断裂患者 2 4例 ,其中 7例以前内束断裂为主 ,17例以后外束断裂为主。所有病例均经关节镜检查确诊 ,其中行关节镜下ACL重建者 16例。结合症状、体征和MRI进行诊断 ,并比较前内束断裂和后外束断裂临床表现的差异。术后随访 9～ 13个月 ,平均 11个月。对手术前后膝关节Lysholm评分结果进行统计分析。结果 :本组病例出现关节不稳的 ,ACL前内束断裂者占 2 8 6 % ,后外束断裂者占 98 2 % ;体检前抽屉试验 (ADT)、Lachman试验和轴移试验 (PST)阳性率 ,前内束断裂者分别为 71 4 %、14 3%和 0 ;后外束断裂者分别为 17 6 %、98 2 %和 76 5 %。ACL重建术后Lysholm评分平均为 93 4 7± 2 6 2 ,较术前 (6 3 5 3± 8 11)明显提高(P <0 0 1)。结论 :ACL部分断裂根据损伤部位的不同临床表现也存在差异。后外束断裂者出现关节不稳较前内束常见 ,前内束断裂主要表现为前抽屉试验阳性 ,而后外束断裂常表现为Lachman试验和轴移试验阳性。对于伴有关节不稳的 ,手术重建ACL效果良好。     

Anterior cruciate ligament anatomy and function relating to anatomical reconstruction

Recently, the interest in surgical techniques that reconstruct the anteromedial (AM) and the posterolateral (PL) bundles of the anterior cruciate ligament (ACL) has risen. This review focuses on the structural as well as the mechanical properties of the ACL and the anatomical details of the femoral origin, midsubstance, and tibial insertion of AM and PL bundles of the ACL. The terminology of AM and PL bundles is chosen according to the tibial insertion and determined by their functional tensioning pattern throughout knee flexion. Close to extension the AM is moderately loose and the PL is tight. As the knee is flexed, the femoral attachment of the ACL becomes more horizontally oriented, causing the AM bundle to tighten and the PM bundle to loosen up. The ACL has been described to be restraint to anterior tibial displacement and internal tibial rotation. The rotational component might be represented by the PL bundle. The femoral origin has an oval shape with the center of the AM close to over-the-top position and the center of the PL close to the anterior and inferior cartilage margin. Tibial and femoral insertions of the ACL are over 3.5 times larger when compared to the midsubstance and tunnel placement is more challenging because of the limited size of potential grafts selection of tunnel site placement. For reconstruction, both bone–patellar tendon–bone (BPTB) and quadrupled hamstring grafts are used. Structural properties of a 10 mm wide BPTB or quadrupled hamstring graft have been reported to be comparable with those of the native ACL.     

Force sharing between two grafts in the anatomical two-bundle anterior cruciate ligament reconstruction

The normal anterior cruciate ligament (ACL) can be generally divided into two main bundles, anteromedial bundle (AMB) and posterolateral bundle (PLB), and each bundle shared its function in response to external loads including anterior tibial drawer force. While we developed the anatomically oriented ACL reconstruction technique via two femoral tunnels and two parallel tibial tunnels (the “anatomical” two-bundle ACL reconstruction), there were few biomechanical studies about this technique. The purpose of this study was to investigate the force sharing between two separate grafts (anteromedial graft, AMG; posterolateral graft, PLG) in this anatomical two-bundle technique by measuring the force of each bundle in response to anterior tibial load. The anatomical two-bundle technique was performed on 11 patients via two tunnels at the supero-posterior portion of the AMB footprint and the supero-posterior portion of the PLB footprint on the posterior margin of the lateral femoral condyle and two tunnels created in the center of the AMB and the PLB tibial footprints. After two doubled semitendinosus grafts were fixed with two EndoButton-CL^®s on the femur, they were temporarily fixed to the tension-adjustable force gauge on the tibial cortex. After each bundle of the graft was settled at the tension of 25 N at 20°, the force exerted on the two bundles was measured with the force gauge during applied anterior tibial force of 134 N at 0°, 30°, 60° and 90° of flexion. While the AMG carried 42.3±5.7% of and the PLG shared 57.7±5.7% of the total force at 0°, the former took 64.1±11.1% and the latter was assigned 33.9±11.1% at 90°. This study has demonstrated that the force distribution between the two grafts in the anatomical two-bundle technique was similar to that between the two bundles in the normal ACL.     

3DCubeT2WIMRI测量前交叉韧带双束结构的研究

目的:应用3D Cube T2WI核磁共振成像斜冠状位重建图像显示前交叉韧带(anterior cruciate ligament,ACL)双束结构,并测量其解剖指标.方法:19例经临床确诊的健康志愿者行双膝关节3D Cube T2加权MRI检查.分别在斜冠状位重建图像测量前内侧束(anteromedial bundle,AMB)和后外侧束(posterolateral bundle,PLB)的股骨止点、胫骨止点宽度、韧带长度及走行角度.应用Mann-Whitney test比较AMB和PLB的长度,止点宽度和走行角度在不同性别间的差异,并进一步对测量所产生的差异进行Logistic回归分析.结果:AMB和PLB的平均长度分别为31.01mm和25.38mm;股骨止点平均宽度为10.6mm和9.47mm;胫骨止点平均宽度为11.28mm和8.49 mm;走行角度平均为72.01°和64.97°.AMB、PLB的股骨止点、胫骨止点宽度及走行角度在不同性别间无显著性差异(P＞0.05).然而,男性AMB和PLB韧带长度大于女性(P＜0.05);经Logistic回归分析显示这种差异与身高成正相关(P＜0.05).结论:各向同性3D Cube T2加权序列及其重建图像所显示的ACL双束结构;以及股骨止点宽度、胫骨止点宽度、长度及走行角度的精确测量结果,可为个性化制定ACL双束重建术方案提供有价值的依据.     

The functions of the fibre bundles of the anterior cruciate ligament in anterior drawer,rotational laxity and the pivot shift

This paper reviews the functional anatomy of the anterior cruciate ligament (ACL), which has a parallel array of collagen fascicles that have usually been divided into two ‘fibre bundles’: anteromedial (AM) and posterolateral (PL), according to their tibial attachment sites. The PL bundle has shorter fibres, and so it is subjected to greater tensile strains than the AM bundle when the whole ACL is stretched; its oblique orientation in the coronal plane imbues it with greater ability to resist tibial rotation than the more vertical AM fibre bundle. Most studies have found that the AM bundle is close to isometric when the knee flexes, while the PL bundle slackens approximately 6 mm. There is little evidence of significant fibre bundle elongation in response to tibial rotation. Selective bundle cutting studies have been performed, allowing both the bundle tensions and their contributions to resisting tibial anterior translation and tibial rotation to be calculated. These show that the function of the PL bundle was dominant near knee extension in some studies, particularly when resisting anterior drawer and that its contribution reduced rapidly with knee flexion through 30 degrees. There has been little study of the contributions of the fibre bundles in control of tibial internal–external rotation or the pivot shift: one study found that the AM bundle had larger tensions than the PL bundle during a simulated pivot shift, but another study found that cutting the PL bundle allowed a larger increase in coupled tibial anterior translation than cutting the AM bundle. It was concluded that the AM bundle is most important for resisting tibial anterior drawer—the primary function of the ACL—while the PL bundle is tight near knee extension, when it has a role in control of tibial rotational laxity. There is a clear need for further study of dynamic knee instability, to gain better understanding of how best to reconstruct the ACL and associated tissues.     

Effect of femoral tunnel position on graft tension curves and knee stability in anatomic double-bundle anterior cruciate ligament reconstruction

Purpose

To evaluate the effect of the femoral tunnel position of the anteromedial bundle (AMB) and the posterolateral bundle (PLB) on the graft tension curves and knee stability in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

Methods

Forty-five patients who underwent anatomic double-bundle ACL reconstruction were included. AMB and PLB were provisionally fixed to a graft tensioning system in the following settings during surgery: (1) AMB at 20° and PLB at 0° (A20P0), (2) AMB at 20° and PLB at 20° (A20P20), and (3) AMB at 20° and PLB at 45° (A20P45). Bundle tension was recorded during knee flexion–extension. A pivot shift test was also evaluated. Femoral tunnel positions of the AMB and PLB were then assessed by three-dimensional computed tomography, and the correlation between femoral tunnel position and tension change pattern or residual pivot shift was evaluated.

Results

The depth of the PLB tunnel position was correlated with the extent of tension reduction in the PLB between 0° and 30° irrespective of graft fixation settings, while neither the AMB tunnel position nor the height of the PLB tunnel position affected the tension change pattern. Ten cases showed grade 1 pivot shift only in the A20P0 setting. The PLB tunnel position in the pivot shift-positive cases was significantly deeper than that in the pivot shift-negative cases (27.5 ± 6.2 and 34.1 ± 5.5 %, respectively, P = 0.002).

Conclusions

In anatomic double-bundle reconstruction, deeper PLB tunnel position was correlated with the larger tension reduction in the PLB between 0° and 30°. Fixation of the AMB at 20° and the PLB at 0° resulted in residual pivot shift phenomenon in 10/45 cases, and the PLB tunnel position in the pivot shift-positive cases was significantly deeper than that in the pivot shift-negative cases. In anatomic double-bundle reconstruction, the placement of PLB femoral tunnel must not be too deep, as it might lead to significant tension reduction in the PLB near extension and thus insufficient tension in the PLB, resulting in residual pivot shift phenomenon.

Level of evidence

IV.     

MRI analysis of the attachment of the anteromedial and posterolateral bundles of anterior cruciate ligament using coronal oblique images

Purpose

The purpose of this study was to evaluate the course of the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of the anterior cruciate ligament (ACL) with magnetic resonance imaging (MRI) in order to clarify the relationship between the bundles and surrounding anatomic landmarks.

Methods

Eighty-eight knees with intact ACLs were included in this study. MRI coronal oblique images were obtained with the knee in extension and used to assess the following characteristics of the AMB and PLB: (1) course of the ligament, (2) location of the tibial attachment, and (3) femoral attachment and geometry of the lateral femoral condyle inner wall.

Results

In terms of the tibial attachment, the AMB was confluent with the apex of the medial intercondylar ridge (MIR) in all cases. Sixty-five PLBs (74%) inserted into the region between the apex and the slope of the MIR. The resident’s ridge was detected in 91% of the knees in the AMB image, whereas the ridge was clearly visualized in only 17% of the knees in the PLB image. A bony eminence was observed at the inner articular margin of the lateral femoral condyle in the PLB image.

Conclusion

In terms of the tibial attachment, the AMB was confluent with the apex of the medial intercondylar ridge in all cases. Most of the PLBs attached to the region between the apex and the slope of the MIR. Because the bone tunnel location influences clearance between the grafts and the surrounding tissues, these results should be considered during anatomic double-bundle ACL reconstruction.

Level of evidence

Study of nonconsecutive patients without a universally applied gold standard, Level III.

     

前交叉韧带股骨后外束足迹解剖变异与双束重建骨道定位的对策

目的:研究前交叉韧带(ACL)股骨侧后外侧束(PLB)在股骨足迹的解剖变异范围、参考标记和关节镜下定位方法。方法:采用30侧人膝关节标本,解剖ACL的PLB在股骨髁间窝外侧壁(Lateral Intercondylar Wall,LIW)的足迹。观察髁间窝外侧壁的形态、住院医师脊(Resident Ridge)与ACL足迹关系、测量ACL长轴与股骨干夹角(AA)、PLB中心距离髁间窝外侧壁下缘软骨的垂直高度(PD)。采用数字影像学方法对足迹进行图像分析。结果:(1)住院医师脊为ACL足迹的上界(屈膝90°),紧靠住院医师脊下方为ACL纤维最集中的部位。(2)AA=18.7±15.25°,范围在-18°与56°之间;PD=7.02±1.47mm,范围在11 mm与3.75 mm之间,二者组数据离散程度均较大。(3)髁间窝外侧壁有2种类型,梯形8侧,三角形22侧,两种髁ACL的AA、PD均有明显差异(P=0.00)。结论:(1)AA、PD因人而异,数值差异较大,必须在术中测量进行个体化PLB定位。(2)虽然由于个体化的解剖变异,关节镜下难以采用通用的指引,但新鲜损伤,可根据明确的残端足迹术中定位;陈旧损伤住院医师脊可见时,PLB中心位置可参考在住院医师脊下方、前内束骨道前方予以定位;另外,3D-CT显示的髁间窝外侧壁形态也可以作为参考,梯形者PLB中心点较高、AA角较平,三角形者PLB中心点较低、AA角较倾斜。(3)如陈旧损伤住院医师脊无法辨认,难以明确PLB高度和AA角,建议进行双束个体化原位解剖重建时需谨慎。     

Comparative risk of common peroneal nerve injury in far anteromedial portal drilling and transtibial drilling in anatomical double-bundle ACL reconstruction

Purpose

The purpose of this study was to investigate the risk of common peroneal nerve injury in FM drilling as compared to transtibial drilling in anatomical double-bundle ACL reconstruction.

Methods

Ten cadaveric knees without ligament injury or significant arthritis were used for this study. Knees were secured at 90° and 120° of flexion. In transtibial drilling groups, a guide pin was drilled through either the anteromedial bundle (AMB) or posterolateral bundle (PLB) tibial insertion site to either the AMB or PLB femoral insertion site (tibial insertion site–femoral insertion site: AM–AM, PL–PL, PL-AM and AM–PL). In FM drilling groups (FM-AM and FM-PL),the pin was drilled at the AMB or PLB femoral insertion site through the FM. We measured the shortest distance between the point at which the pin ran through the lateral cortex of the femur and the ipsilateral common peroneal nerve at a knee flexion of 90° and 120°.

Results

At a knee flexion of 90°, the shortest mean distance to the common peroneal nerve was 15.3?mm in the FM-PL group, 13.4?mm in the FM-AM group, 27.9?mm in the PL–PL group, 30.8?mm in the AM–AM group, 37.8?mm in the PL–AM group and 29.5?mm in the AM–PL group. At a knee of flexion 120°, the mean distance was 17.3?mm in the FM-PL group, 18.1?mm in the FM-AM group, 32.2?mm in the PL–PL group, 36.6?mm in the AM–AM group, 38.0?mm in the PL–AM group and 35.2?mm in the AM–PL group. Significant differences were observed between 90° and 120° of knee flexion in the FM-AM, PL–PL, AM–AM and AM–PL groups (P?<?0.05).Significant differences were observed at flex 90° between the FM-AM group and AM–AM group, and between the FM-AM group and PL–AM group. Significant differences were observed at flex 120° between the FM-AM group and AM–AM group, between the FM-AM group and PL–AM group and between the FM-PL group and AM–PL group.

Conclusion

The distance to the peroneal nerve in FM drilling was significantly longer at 120° than at 90° of knee flexion. Therefore, the risk of peroneal injury using FM drilling should decrease at a higher angle of knee flexion.     

Relationship between thickness of the anteromedial bundle and thickness of the posterolateral bundle in the normal ACL

Purpose  

Since the development of the anatomic double-bundle anterior cruciate ligament (ACL) reconstruction, many studies have focused on excursion and/or tension of each graft. However, no studies to date have adequately investigated thickness of the graft in anatomic double-bundle ACL reconstruction. To obtain basic knowledge from which an ideal graft thickness can be inferred, thicknesses of the anteromedial bundle (AMB) and posterolateral bundle (PLB) was measured in the normal ACL.     

Intercondylar roof impingement pressure after anterior cruciate ligament reconstruction in a porcine model

Anterior cruciate ligament (ACL) graft impingement against the intercondylar roof has been postulated, but not thoroughly investigated. The roof impingement pressure changes with different tibial and femoral tunnel positions in ACL reconstruction. Anterior tibial translation is also affected by the tunnel positions of ACL reconstruction. The study design included a controlled laboratory study. In 15 pig knees, the impingement pressure between ACL and intercondylar roof was measured using pressure sensitive film before and after ACL single bundle reconstruction. ACL reconstructions were performed in each knee with two different tibial and femoral tunnel position combinations: (1) tibial antero-medial (AM) tunnel to femoral AM tunnel (AM to AM) and (2) tibial postero-lateral (PL) tunnel to femoral High-AM tunnel (PL to High-AM). Anterior tibial translation (ATT) was evaluated after each ACL reconstruction using robotic/universal force-moment sensor testing system. Neither the AM to AM nor the PL to High-AM ACL reconstruction groups showed significant difference when compared with intact ACL in roof impingement pressure. The AM to AM group had a significantly higher failure load than PL to High-AM group. This study showed how different tunnel placements affect the ACL-roof impingement pressure and anterior-posterior laxity in ACL reconstruction. Anatomical ACL reconstruction does not cause roof impingement and it has a biomechanical advantage in ATT when compared with non-anatomical ACL reconstructions in the pig knee. There is no intercondylar roof impingement after anatomical single bundle ACL reconstruction.     

Anatomical study of the human anterior cruciate ligament stump’s tibial insertion footprint

The aim of this study is to define the topographical relationship of the anatomical bundles of the human anterior cruciate ligament's (ACL) stump over the tibial insertion site. Between January and April 2007, a total of 36 resected tibial plateaus were retrieved from patients who underwent total knee replacements. These samples had intact cruciate ligaments with no major osteophyte around the ACL tibial insertion footprint. The anatomical bundles of the ACL were identified and mapped, based on the topographical relationship over the tibial insertion footprint. Measurements of the dimensions of the ACL tibial footprint and tibial plateau were performed. The mean width and midsagittal depth of the tibia plateau was 78.7 +/- 6.5 and 46.4 +/- 5.0 mm, respectively. The mean width and midsagittal depth of the ACL tibial footprint was 10.3 +/- 1.9 and 19.5 +/- 2.6 mm, respectively. Out of the 36 freshly dissected ACL stumps, it was not possible to distinguish separate bundles in 14 (38.9%) cases. The average distance between the centers of the two bundles was 9.3 +/- 1.8 mm. The mean AP alignment of the tibial footprint was 89.6 degrees +/- 26.4 degrees , with a very wide range of 23 degrees -158 degrees . Of the 22 specimens with separate anatomical bundles, the alignment of the tibial footprint was AM-PL in six (27.3%), sagittal (85 degrees -95 degrees ) in five (22.7), AL-PM in nine (40.9%), and lateral-medial (L-M) in two (9.1%) cases. This study provides new information about the topographical anatomy of the ACL tibial insertion footprint. Based on gross anatomy, separate anatomical bundles of the ACL can be distinguished in 61.1% [22] of the specimens. The topographical alignment of the separate bundles is varied on a very wide range.     

Anatomy of the anterior cruciate ligament double bundle structure: a macroscopic evaluation

INTRODUCTION: Traditional anterior cruciate ligament (ACL) surgery has demonstrated good results, but there is still a subset of unsatisfactory outcomes. Trends in reconstruction technique have changed from bone-patella-tendon-bone to hamstring refixation, and the next step appears to be the double bundle concept. METHODS: We examined six fresh-frozen cadaver knees to evaluate the double bundle structure, dynamic motion characteristics and the relationship of knee flexion and relative position of the femoral insertion sites of the ACL. RESULTS: In all knees, we identified an anteromedial (AM) and posterolateral (PL) bundle. The motion pattern demonstrated that the AM and PL bundles are oriented near parallel with the knee extended, and twist around each other as the knee is flexed. The visualization of the femoral footprint anatomy differs with knee flexion. DISCUSSION: The double bundle model facilitates restoration of the original footprint anatomy and biomechanics more easily than the concept of the ACL as a one-bundle structure and the use of the o'clock position. It is essential to be aware of the degree of knee flexion when drilling the femoral tunnels. PERSPECTIVE: Anatomic ACL reconstruction is a concept, not a technique, and allows a more refined surgical approach to ACL reconstruction including revision cases and partial ACL tears.     

Two-bundle, four-tunnel anterior cruciate ligament reconstruction

We reviewed 33 patients who underwent anterior cruciate ligament (ACL) reconstruction using a two-bundle, four-tunnel technique. The posterolateral bundle (PLB) and anteromedial bundle (AMB) were individually reconstructed with gracilis and semitendinosus tendon auto-grafts, respectively, using separate tibial and femoral tunnels. At final follow-up (24 months post surgery, range 18–31) the International Knee Documentation Committee’s (IKDC) objective final evaluation scores were 69 A, 19 B, 12% C. The mean global subjective IKDC score was 86±12 points. Ninety-four percent of the patients had returned to sport after an average of 9 months following surgery and 75% returned to their preinjury sporting level. One patient had suffered a graft rupture as a result of a further sports injury. Eighty-four percent of the patients had a negative pivot shift (IKDC A), 9% a glide (IKDC B), and 6% a “clunk” (IKDC C). The mean postoperative side-to-side laxity, measured with KT1000 arthrometry at manual maximum, was 0.9 mm (SD 1.9). Eighty-one percent of the patients had less than 3 mm difference, with only one patient having greater than 5 mm. Our early experience with this new technique appears to demonstrate satisfactory results that are at least equivalent to other techniques and show an apparent trend towards improved control of anterior laxity.     

Biomechanics of the porcine triple bundle anterior cruciate ligament

Several species of animals are used as a model to study human anterior cruciate ligament (ACL) reconstruction. In many animals, three bundles were clearly discernible during dissection in the ACL. However, there are few reports about the biomechanical role of each bundle in the porcine knee. The purpose of this study is to investigate the role of each of the three bundles in the porcine knee, especially the intermediate bundle. Ten porcine knees were tested using a robotic/universal forcemoment sensor system. This system applied anterior loading of 89 N at 30°, 60° and 90° of flexion, and a combined 7 Nm valgus and 4 Nm internal tibial torque at 30° and 60° of flexion before and after each bundle was selectively cut. The in situ force (N) for each bundle of the ACL was measured. Both intermediate (IM) bundle and postero-lateral (PL) bundle had significantly lower in situ force than the antero-medial (AM) bundle in anterior loading. The IM and PL bundles carried a larger proportion of the force under the torsional loads than the anterior loads. But IM bundle had a significant lower in situ force during the combined torque at 60° of knee flexion, when compared intact ACL. In summary, IM bundle has a subordinate role to the AM and PL bundles. AM bundle is more dominant than IM and PL bundles. The porcine knee is a suitable model for ACL studies, especially for AP stability.