Lateral radiographic study of the tibial sagital insertions of the anteromedial and posterolateral bundles of human anterior cruciate ligament

Recently, the femoral attachments of anteromedial and posterolateral bundles of anterior cruciate ligament (ACL) have been extensively discussed, however, few publications have mentioned radiographic measurements of the tibial insertions of two bundles. The aim of this study is to determine the radiographic measurements of the tibial sagital insertions for anteromedial (AM) and posterolateral (PL) bundles of ACL. Thirty-one cadaveric proximal tibias were used. After identification of the AM and PL bundles insertion sites on the tibia, the insertion center and the other anatomic landmarks were marked with a lead pin, and lateral radiographs were taken. Sagital percentage is a percentage of the location of the insertion point calculated from the anterior margin of the tibia in the anteroposterior direction. Anterior edge of ACL averaged 25.0%, center of AM averaged 34.6%, center of PL averaged 38.4%, posterior edge of ACL averaged 50.2%. This study defines the radiographic location of the tibial insertions of the anteromedial and posterolateral bundles of ACL. This contributes to more precise evaluation of anatomical double bundle ACL reconstruction surgery postoperatively.     

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.     

Changes in ACL length at different knee flexion angles: an in vivo biomechanical study

Recently, there has been a tremendous impetus on anatomical reconstruction of the anterior cruciate ligament (ACL), and the double-bundle reconstruction concept has been advocated by many authors. It is, therefore, important to understand how the lengths of the two bundles of the ACL vary during different knee flexion angles as this could influence the angle of graft fixation during surgery. The aim of this study is to determine the change in length of the ACL bundles during different knee flexion angles. Ten subjects with normal knees were evaluated. A high-resolution computer tomography scan was performed, and 3D knee images were obtained. These images were then imported to customized software, and digital length measurement of four virtual bundles (anatomical single bundle, AM, PL and over the top) was evaluated from fixed points on the femur and tibia. Length-versus-flexion curves were drawn, and statistical analysis was performed to evaluate changes in length for each bundle at varying angles of knee flexion (0°, 45°, 90° and 135°). All virtual bundles achieved greatest lengths at full extension. There was a significant difference between the posterolateral bundle length when compared to the other bundles at full extension. There were no significant differences between the lengths of the anteromedial and the over the top single bundles at all angles of knee flexion. Three-dimensional computer tomography can be used to assess the length changes of the virtual anterior cruciate ligament bundles, thereby allowing a better understanding of bundle function in clinical situations.     

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.     

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.     

Anterior cruciate ligament: an anatomical exploration in humans and in a selection of animal species

Purpose

Many anatomical anterior cruciate ligament (ACL) studies have indicated that the human ACL is composed of two functional bundles: the antero-medial (AM) and postero-lateral (PL). The purpose of this study is to compare the ACL anatomy among human and assorted animal species.

Methods

Twenty fresh-frozen knees specimen were used: five humans, ten porcine, one goat, one Kodiak bear, one African lion, one Diana monkey and one Gazelle antelope. All the specimens were dissected to expose the ACL and to visualize the number of bundles and attachment patterns on the tibia and femur. Following the fibre orientation of the individual bundles, a wire loop was used to bluntly separate the bundles starting from the tibial insertion site to the femoral insertion site. In the human and porcine ACL, each bundle was separated into approximately 2 mm diameter segments and then tracked in order to establish the individual bundle’s specific pattern of insertion on the femur and tibia.

Results

It appeared that all human and animal knee specimens had three bundles that made up their ACL. In addition, it was noted that among the various specimens species, all viewed with an anterior view, and at 90° knee flexion, the ACL bony insertion sites had similar attachment patterns.

Conclusion

In all the specimens, including human, the ACL had three distinct bundles: AM, intermediate (IM) and PL. The bundles were composed of multiple fascicles arranged in a definite order and similar among the different species.     

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.     

Mechanical functions of the three bundles consisting of the human anterior cruciate ligament

Purpose

The reconstruction technique to individually reconstruct multi-bundles of the anterior cruciate ligament (ACL) has been improved in the last decade. For further improvement of the technique, the present study was conducted to determine the force sharing among the three bundles (the medial and lateral bundles (AMM and AML) of the anteromedial (AM) bundle and the posterlateral (PL) bundle) of the human ACL in response to hyperextension, passive flexion–extension and anterior force to the knee.

Methods

Using a 6-DOF robotic system, the human cadaveric knee specimens were subjected to hyperextension, passive flexion–extension and anterior–posterior tests, while recording the 6-DOF motion and force/moment of the knees. The intact knee motions recorded during the tests were reproduced after sequential bundle transection to determine the bundle forces.

Results

The bundle forces were around 10 N at 5 N-m of hyperextension and remained less than 5 N during passive flexion–extension. In response to 100 N of anterior force, the AMM and PL bundle forces were slightly higher than the AML bundle force at full extension. The AMM bundle force remained at a high level up to 90° of flexion, with significant differences versus the AML bundle force at 15°, 30° and 60° of flexion and the PL bundle force at 90° of flexion.

Conclusion

The AMM bundle is the primary stabilizer to tibial anterior drawer through wide range of motion, while the AML bundle is the secondary stabilizer in deep flexion angles. The PL bundle is the crucial stabilizer to hyperextension as well as tibial anterior drawer at full extension.

Level of evidence

Prognostic study, Level II.

     

Coronal tibial anteromedial tunnel location has minimal effect on knee biomechanics

Purpose

Studies 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.

Methods

Two 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.

Results

Both medial (2.6?±?1.2 mm) and lateral (1.6?±?0.9 mm) double-bundle reconstructions reduced the anterior tibial translation (ATT) to less than the intact value (3.9?±?0.7 mm) 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.

Conclusion

The 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.

     

Evaluation of the tunnel placement in the anatomical double-bundle ACL reconstruction: a cadaver study

The objective of this study was to investigate the accurate AM and PL tunnel positions in an anatomical double-bundle ACL reconstruction using human cadaver knees with an intact ACL. Fifteen fresh-frozen non-paired adult human knees with a median age of 60 were used. AM and PL bundles were identified by the difference in tension patterns. First, the center of femoral PL and AM bundles were marked with a K-wire and cut from the femoral insertion site. Next, each bundle was divided at the tibial side, and the center of each AM and PL tibial insertion was again marked with a K-wire. Tunnel placement was evaluated using a C-arm radiographic device. For the femoral side assessment, Bernard and Hertel’s technique was used. For the tibial side assessment, Staubli’s technique was used. After radiographic evaluations, all tibias’ soft tissues were removed with a 10% NaOH solution, and tunnel placements were evaluated. In the radiographic evaluation, the center of the femoral AM tunnel was placed at 15% in a shallow–deep direction and at 26% in a high–low direction. The center of the PL bundle was found at 32% in a shallow–deep direction and 52% in a high–low direction. On the tibial side, the center of the AM tunnel was placed at 31% from the anterior edge of the tibia, and the PL tunnel at 50%. The ACL tibial footprint was placed close to the center of the tibia and was oriented sagittally. AM and PL tunnels can be placed in the ACL insertions without any coalition. The native ACL insertion site has morphological variety in both the femoral and tibial sides. This study showed, anatomically and radiologically, the AM and PL tunnel positions in an anatomical ACL reconstruction. We believe that this study will contribute to an accurate tunnel placement during ACL reconstruction surgery and provide reference data for postoperative radiographic evaluation.     

The effect of intra-operative knee flexion angle on determination of graft location in the anatomic double-bundle anterior cruciate ligament reconstruction

Graft tunnel placement is the factor with most influence on the outcome of double-bundle anterior cruciate ligament (ACL) reconstruction. However the final decision for the graft location has to be decided subjectively under arthroscopy, and can be misplaced due to the effect of the knee flexion angle. The displacement of the estimated placement by surgeons from the ACL anatomical attachment is due to the knee’s differing knee flexion angle. Eight cadaveric knees and an electromagnetic position recording system were employed. After digitizing the anatomical location of AM and PL bundle center, four experienced surgeons estimated the graft placement repeatedly at 70°, 90° and 110° of knee flexion. The displacements between these two positions were calculated and analyzed separately in antero-posterior and disto-proximal directions. The displacements of the estimated AM bundle placements were 4.7 ± 3.4 mm at 70°, 4.3 ± 2.2 mm at 90°, and 6.0 ± 2.6 mm at 110°, while those of the PL bundle were 4.0 ± 2.2 mm at 70°, 3.4 ± 1.9 mm at 90°, and 4.2 ± 2.5 mm at 110°. The best results were obtained at 90° of knee flexion. Additionally, the estimated placements for both AM and PL bundle were located more distally as the flexion angle increased. Our results imply that the knee should be set at 90° when determining the graft placement in double-bundle reconstruction to prevent misplacement of the graft usually in a disto-proximal direction.     

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

Purpose

Recent 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.

Methods

Sixteen fresh-frozen cadaver knees were used. In one group (n = 8), 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 (n = 8), 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 89 N was applied for anterior tibial translation (ATT) at 0°, 15°, 30° and 60° of knee flexion. Subsequently, a combined rotatory load (5 Nm internal rotation and 7 Nm 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.

Results

Compared 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.

Conclusion

Among the techniques, AM–AM afforded the highest in situ force and the least ATT.     

Analysis of the graft bending angle at the femoral tunnel aperture in anatomic double bundle anterior cruciate ligament reconstruction: a comparison of the transtibial and the far anteromedial portal technique

The aim of this study is to investigate and compare the three dimensional bending angle of the graft at the femoral tunnel aperture in the transtibial and the far anteromedial portal technique. Seven fresh-frozen human cadaveric knees were used. Six degrees-of-freedom of knee kinematics and knee position data were measured using an electromagnetic device and the three dimensional bending angles of the each graft at the femoral tunnel aperture were calculated by computer simulation. Additionally, in order to assess the stress on the graft, the length change between the femoral and tibial attachment sites of the AM and PL bundle were calculated. The maximum length of each bundle was detected at full extension of the knee. The relative change of the length of the PL bundle in the range of 70°–0° of knee flexion was significantly larger than that of the AM bundle. (P < 0.05) Maximum graft bending angles in both techniques were obtained at full extension where the graft was fully stretched. The AM and PL graft bending angles in the transtibial technique were significantly larger than in the far anteromedial portal technique at low flexion angle (AM: 0°–10°, PL: 0°–50°) (P < 0.01). This suggests use of the far anteromedial portal technique might result in lower stress on the graft at the femoral tunnel aperture and therefore might reduce graft damage.     

The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament

The aim of this study was to describe the anatomical locations of the femoral attachments of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL). Twenty-two human cadaver knees with intact ACLs were used. The femoral attachments of the two bundles were identified, marked and photographed. They were measured and described in terms of the o’clock positions parallel to the femoral long axis and parallel to the roof of the intercondylar notch. The centres of the bundles were also measured in a high–low and a superficial-deep manner referencing from the centre of the posterior femoral condyle, and with respect to their positions within a measurement grid defined in this study. The bulk of the AM bundle was attached between the 9.30 and 11.30 o’clock positions and the PL bundle between the 8.30 and 10 o’clock positions. The AM and PL bundles were consistently found in specific zones of the measurement grid. Using the posterior condyle reference method, the centre of the AM bundle was at 68 ± 7% (range 57–78) in a shallow–deep direction and 55 ± 5% (44–62) in a high–low direction. The PL bundle was found at 56 ± 8% (40–73) in a shallow–deep direction, and 62 ± 7.0% (40–70) in a high–low direction. The attachment was oriented at 37° to the femoral long axis. The results from this study could be used to guide ACL reconstruction techniques.     

Biomechanics of the goat three bundle anterior cruciate ligament

The goat is a widely used animal model for basic research on the anterior cruciate ligament (ACL), but the biomechanical role of the different bundles [intermediate (IM), anteromedial (AM), posterolateral (PL)] of the ACL is unclear. Therefore, the aim of this study is to describe the biomechanical function of the different bundles and evaluate its use for a double bundle ACL reconstruction model. A CASPAR Stäubli RX90 robot with a six degree-of-freedom load cell was used for measurement of anterior tibial translation (ATT) (mm) and in situ forces (N) at 30° (full extension), 60°, 90° as well as rotational testing at 30° in 14 paired goat knees before and after each bundle was cut. When the AM-bundle was cut, the ATT increased significantly at 60° and 90° of flexion (p < 0.05). When the PL-bundle was cut, the ATT increased only at 30°. However, most load was transferred through the big AM-bundle while the PL-bundle shared significant load only at 30°, with only minimal contribution from the IM-bundle at all flexion degrees. The observed biomechanical results in this study are similar to the human ACL observed previously in the literature. Though anatomically discernible, the IM-bundle plays only an inferior role in ATT and might be neglected as a separate bundle during reconstruction. The goat ACL shows some differences to the human ACL, whereas the main functions of the ACL bundles are similar.     

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 knee flexion on the in situ force distribution in the human anterior cruciate ligament

This study was conducted to evaluate the effect of applied load on the magnitude, direction, and point of tibial intersection of the in situ forces of the anteromedial (AM) and posterolateral (PL) bands of the human anterior cruciate ligament (ACL) at 30° and 90° of knee flexion. An Instron was used to apply a 100 N anterior shear force to 11 human cadaver knees, 6 at 30° of knee flexion and 5 at 90° of knee flexion. A Universal Force Sensor (UFS) recorded the resultant 6 degree-of freedom (DOF) forces/moments. Each specimen then underwent serial removal of the AM and PL bands. With the knee limited to 1 DOF (anteroposterior), tests were performed before and after each structure was removed. Because the path was identical in each test, the principle of superposition was applied. Thus, the difference between the resultant forces could be attributed to the force carried by the structure just removed. The magnitudes of force in the ACL at 30° and 90° of knee flexion were 114.1±7.4 N and 90.8±8.3 N, respectively (P<0.05). At 30°, the AM and PL bundles carried 95% and 4% of the total ACL force, respectively. At 90°, the AM and PL bands carried 85% and 13%, respectively (P<0.05). The direction of the in situ force in the whole ACL as well as its two bands correlated with the anatomic orientation of the ligament. The resultant total ACL force intersected the tibial plateau at the posterolateral aspect of the AM band's insertion at 30° of knee flexion, while at 90°, the force intersection moved posteriorly to the AM/PL border. This research provides new insight into the fundamental force relationships of the ACL and its bundles. In response to an anterior tibial shear force, the AM band of the ACL was the predominant load carrier at both 30° and 90° of knee flexion. However, contrary to carlier reports, the in situ force carried in the PL band increased as knee flexion increased. Further, the tibial intersection of the resultant ACL force moved laterally with knee flexion. These findings confirm the dynamic structure of the ACL that in itself has no isometricity and may also indicate that there is no ideal location in which to position a replacement graft. The use of this methodology with more physiologically unconstrained motion should lead to more definitive clinical conclusions.     

Arthroscopic evaluation of the ACL double bundle structure

In order to describe the arthroscopic presence of the double bundle structure and to evaluate the value of different portals in knee arthroscopy, we assessed the AM and PL bundle anatomy. We prospectively examined the knees of 60 patients undergoing arthroscopic surgery for pathology unrelated to the ACL. Arthroscopy was performed in a two portal technique using an anterolateral (ALP) and an anteromedial (AMP) portal. With the arthroscope in the ALP, we could distinguish an AM and PL bundle in 28%. Switching the arthroscope to the AMP, differentiation of the bundles was possible in 67%. In all remaining cases visualization of the PL bundle was possible after retraction of the AM bundle. Use of AMP increased visualization of the PL bundle. It seems reasonable to perform arthroscopy for ACL reconstruction with the arthroscope in the AMP and to establish an additional medial working portal to increase the visualization of the femoral ACL insertion sites for optimal femoral tunnel placement.     

The relationship of lateral anatomic structures to exiting guide pins during femoral tunnel preparation utilizing an accessory medial portal

Anatomic reconstruction of the anterior cruciate ligament through an accessory medial portal has become increasingly popular. The purpose of this study is to describe the relationship of guide pin exit points to the lateral anatomic structures when preparing the anterior cruciate ligament femoral tunnel through an accessory medial portal. We utilized seven fresh frozen cadaveric knees. Utilizing an anteromedial approach, a guide wire was placed into the center of each bundle’s footprint. Each guide wire was advanced through the lateral femoral cortex. The guide pins were passed at 90, 110, and 130° of knee flexion. The distances from each guide pin to the closest relevant structures on the lateral side of the knee were measured. At 90° the posterolateral bundle guide pin was closest to the lateral condyle articular cartilage (mean 5.4 ± 2.2 mm) and gastrocnemius tendon (mean 5.7 ± 2.1 mm). At 110° the posterolateral bundle pin was closest to the gastrocnemius tendon (mean 4.5 ± 3.4 mm). At 130° the posterolateral bundle pin was closest to the gastrocnemius tendon (mean 7.2 ± 5.5 mm) and lateral collateral ligament (mean 6.8 ± 2.1 mm). At 90° the anteromedial bundle guide pin was closest to the articular cartilage (mean 2.0 ± 2.0 mm). At 110° the anteromedial bundle pin was closest to the articular cartilage (mean 7.4 ± 3.5 mm) and gastrocnemius tendon (mean 12.3 ± 3.1 mm). At 130° the AM bundle pin was closest to the gastrocnemius tendon (mean 8.2 ± 3.2 mm) and LCL (mean 15.1 ± 2.9 mm). Neither guide pin (anteromedial or posterolateral bundle) put the peroneal nerve at risk at any knee flexion angle. At low knee flexion angles the anteromedial and posterolateral bundle guide pins closely approximated multiple lateral structures when using an accessory medial arthroscopic portal. Utilizing higher flexion angles increases the margin of error when preparing both femoral tunnels. During preparation of the anterior cruciate ligament femoral tunnel through an accessory anteromedial portal the tunnels should be drilled in at least 110° of knee flexion in order to move guide pin exit points away from important lateral knee structures.     

Anatomic double-bundle ACL reconstruction using a bone–patellar tendon–bone autograft: a technical note

This article describes an original arthroscopic double-bundle anterior cruciate ligament (ACL) reconstruction technique using a bone–patellar tendon–bone autograft. A rectangular patellar bone block, with a double strand patellar tendon, and a double tibial bone block is harvested. The femoral anteromedial tunnel is made using an all-inside technique by the anteromedial portal. The femoral posterolateral (PL) tunnel is created with an outside-in technique, with a 30° divergence between both tunnels. A single tibial tunnel is drilled, the graft is then passed through the tibial tunnel, and the bundles are separately tensioned and fixed with three bioabsorbable interference screws. The femoral AM bone block is fixed by the anteromedial portal, the tibial bone block is then fixed in an oblique manner in order to mimic the ACL orientation with the knee at 30° of flexion. The femoral PL bone block is fixed at the end with the knee in full extension.