Cadaveric knee observation study for describing anatomic femoral tunnel placement for two-bundle anterior cruciate ligament reconstruction

Arthroscopically pertinent landmarks for tunnel positioning in single-bundle and double-bundle anterior cruciate ligament reconstructions

BACKGROUND

Quantification of the overall anterior cruciate ligament (ACL) and anteromedial (AM) and posterolateral (PL) bundle centers in respect to arthroscopically pertinent bony and soft tissue landmarks has not been thoroughly assessed.

HYPOTHESIS

A standardized anatomical measurement method can quantitate the locations of the ACL and AM and PL bundle centers in reference to each other and anatomical landmarks.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Quantification of the ACL and its bundle attachments was performed on 11 cadaveric knees using a radio frequency-tracking device.

RESULTS

The tibial ACL attachment center was 7.5 mm medial to the anterior horn of the lateral meniscus, 13.0 mm anterior to the retro-eminence ridge, and 10.5 mm posterior to the ACL ridge. The femoral ACL attachment center was 1.7 mm proximal to the bifurcate ridge and 6.1 mm posterior to the lateral intercondylar ridge. The tibial AM attachment center was 8.3 mm medial to the anteromedial aspect of the lateral meniscus anterior horn, 17.8 mm anterior to the retro-eminence ridge, and 5.6 mm posterior to the ACL ridge. The femoral AM attachment center was 4.8 mm proximal to the bifurcate ridge and 7.1 mm posterior to the lateral intercondylar ridge. The tibial PL bundle attachment center was 6.6 mm medial to the posteromedial aspect of the lateral meniscus anterior horn, 10.8 mm anteromedial to the root attachment of the lateral meniscus posterior horn, and 8.4 mm anterior to the retro-eminence ridge. The femoral PL bundle attachment center was 5.2 mm distal to the bifurcate ridge and 3.6 mm posterior to the lateral intercondylar ridge.

CONCLUSION

The authors developed a comprehensive compilation of measurements of arthroscopically pertinent bony and soft tissue landmarks that quantitate the ACL and its individual bundle attachment centers on the tibia and femur.

CLINICAL RELEVANCE

These clinically relevant arthroscopic landmarks may enhance single- and double-bundle ACL reconstructions through improved tunnel placement.

ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION USING THE DOUBLE-BUNDLE TECHNIQUE – EVALUATION IN THE BIOMECHANICS LABORATORY

Objective: The objective of this study was to describe the methodology of knee rotation analysis using biomechanics laboratory instruments and to present the preliminary results from a comparative study on patients who underwent anterior cruciate ligament (ACL) reconstruction using the double-bundle technique. Methods: The protocol currently used in our laboratory was described. Three-dimensional kinematic analysis was performed and knee rotation amplitude was measured on eight normal patients (control group) and 12 patients who were operated using the double-bundle technique, by means of three tasks in the biomechanics laboratory. Results: No significant differences between operated and non-operated sides were shown in relation to the mean amplitudes of gait, gait with change in direction or gait with change in direction when going down stairs (p > 0.13). Conclusion: The preliminary results did not show any difference in the double-bundle ACL reconstruction technique in relation to the contralateral side and the control group.

ACL injury and surgical treatment options

The anterior cruciate ligament (ACL) has been the focus of a substantial amount of research. Thousands of studies have evaluated the structure and function of the intact ACL, as well as the best reconstruction techniques. Despite the amount of literature, many controversies remain regarding the ACL and its surgical reconstruction. This article reviews the anatomy and function of the native ACL, the nature of injury, and aspects of ACL reconstruction, including surgical approach, tunnel positioning, graft choice, and graft fixation.

Size variability of the human anterior cruciate ligament insertion sites

BACKGROUND

Current trends in anterior cruciate ligament reconstruction (ACLR) have been toward anatomical reconstruction that restores the normal size and location of the anterior cruciate ligament insertions and its 2 bundles, the posterolateral (PL) and anteromedial (AM) bundles. This has resulted in a more individualized approach to ACLR. Several studies have shown that the size of the anterior cruciate ligament insertion sites is variable; however, these studies are limited by use of relatively small sample sizes and cadaveric specimens.

PURPOSE

This study was undertaken to evaluate the in vivo size variability of the anterior cruciate ligament insertion sites and its AM and PL bundles during arthroscopy in a large series of patients and to correlate these findings with individuals' physical characteristics (height, weight, and body mass index).

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In 137 patients undergoing ACLR during the first 6 months after injury, the femoral and tibial anterior cruciate ligament insertion sites and the 2 bundles were identified, marked with electrocautery, and measured with an arthroscopic ruler. Additionally, physical characteristics of the patients, including self-reported height, weight, and body mass index, were recorded.

RESULTS

The tibial anterior cruciate ligament insertion site had a mean length of 17.0 ± 2.0 mm. The tibial AM bundle length was 9.1 ± 1.2 mm and the width was 9.2 ± 1.1 mm. The tibial PL bundle insertion site length averaged 7.4 ± 1.0 mm and the width averaged 7.0 ± 1.0 mm. The femoral insertion sites had a mean length of 16.5 ± 2.0 mm. The length of the femoral AM bundle insertion site averaged 9.2 ± 1.2 mm and the width averaged 8.9 ± 0.9 mm. The femoral PL bundle insertion site length averaged 7.1 ± 1.1 mm and the width averaged 6.9 ± 1.0 mm. There were significant positive correlations between patient height and weight (P < .05) with femoral and tibial anterior cruciate ligament insertion site length, tibial PL bundle insertion site length, femoral AM bundle insertion site length, and tibial AM bundle and PL bundle insertion site areas. However, the coefficients of determination values were low (1.0% to 19.4%).

CONCLUSION

There is a large variation in size of the anterior cruciate ligament insertion sites and the AM and PL bundles. Additionally, there are significant but weak correlations between the size of the insertions and height, weight, and body mass index of the individual patient.

Direct anterior cruciate ligament insertion to the femur assessed by histology and 3-dimensional volume-rendered computed tomography

PURPOSE

The purpose of this study was to histologically identify the direct and indirect insertion of the femoral anterior cruciate ligament (ACL) insertion. Furthermore, we quantitatively measured the direct femoral insertion area by use of the 3-dimensional (3D) volume-rendered (VR) computed tomography (CT) model.

METHODS

By use of 8 intact cadaveric knees, the lateral femoral condyle including the ACL attachment was sectioned for histologic examination in 3 oblique-axial planes parallel to the roof of the intercondylar notch and in the sagittal planes. Before sectioning, these knees had been subjected to CT to obtain 3D VR images of the femur. Once the direct insertion of the ACL was identified on each histologic section, the corresponding image was superimposed on the corresponding CT image.

RESULTS

The direct ACL insertion, in which dense collagen fibers were connected to the bone by the fibrocartilaginous layer, was microscopically identified at the region between the posteromedial articular cartilage margin of the lateral femoral condyle and the linear bony ridge 7 to 10 mm anterior to the articular cartilage margin. Meticulous comparison of histologic analysis and the 3D VR CT model showed that the ACL direct insertion coincided with a crescent-shaped hollow just behind the linear bony ridge. The direct insertion measured 17.4 +/- 0.9 mm (mean +/- SD) in length, 8.0 +/- 0.5 mm in width, and 128.3 +/- 10.5 mm(2) in area.

CONCLUSIONS

The direct insertion of the ACL is located in the depression between the resident's ridge and the articular cartilage margin on the lateral femoral condyle. It measured 17.4 +/- 0.9 mm in length, 8.0 +/- 0.5 mm in width, and 128.3 +/- 10.5 mm(2) in area.

CLINICAL RELEVANCE

Delineation of the ACL femoral direct insertion by 3D VR CT could be a useful tool for planning of accurate femoral tunnel positioning in anatomic ACL reconstruction.

Anterior cruciate ligament reconstruction: drilling a femoral posterolateral tunnel cannot be accomplished using an over-the-top step-off drill guide

The objective of this study was to evaluate the position of a K-wire drilled into the lowest and most shallow position possible in the femoral footprint of the anterior cruciate ligament (ACL) with an over-the-top drill guide and to compare this position in relation to the total length of the femoral footprint. In eight specimens, the K-wire was drilled through the guide from the medial side to mimic the anteromedial portal used during arthroscopy. The distances between the K-wire and the farthest points of the anteromedial (AM) and posterolateral (PL) end of the ACL footprint were measured. The median ACL footprint was 15 mm (range 14-18). The median distance from the K-wire was 5 mm (range 3-8) to the AM end of the footprint and 10 mm (range 9-15) to the PL end of the footprint. The K-wire did not reach the middle of the ACL footprint length in any of the specimens. The posterior border of the articular cartilage on the lateral femoral condyle prevented the drill guide from being placed in a lower and more shallow position. The results of this study showed that a tunnel drilled using an over-the-top drill guide and placed in the lowest and most shallow position possible within the ACL footprint is almost exclusively situated in the AM bundle origin.

Anatomic double-bundle anterior cruciate ligament reconstruction

Several double-bundle anterior cruciate ligament (ACL) reconstruction procedures were reported in the 1980s and 1990s. However, no significant differences were found in the clinical results between these double-bundle procedures and single-bundle procedures because the double-bundle procedures appeared to reconstruct only the anteromedial bundle with 2 bundles. In the early 2000s, we proposed a new concept of anatomic reconstruction of the anteromedial and posterolateral bundles, in which 4 independent tunnels were created through the center of each anatomic attachment of the 2 bundles. We called it "anatomic" double-bundle ACL reconstruction. Biomechanical studies have shown that the anatomic double-bundle ACL reconstruction can restore knee stability significantly more closely to the normal level than the conventional single-bundle reconstruction. Recent intraoperative measurement studies have shown that the clinically available anatomic double-bundle procedures can reconstruct knee stability significantly better and improve knee function close to the normal level at the time immediately after surgery compared with the conventional single-bundle procedures. However, the greatest criticism of the anatomic double-bundle reconstruction is whether its clinical results are better than the results of single-bundle reconstruction. To date (January 2010), 10 prospective comparative clinical trials (Level I or II) and 1 meta-analysis have been reported comparing single-bundle and anatomic double-bundle reconstructions using hamstring tendons. In 8 of the 10 studies, the anterior and/or rotatory stability of the knee was significantly better with the anatomic double-bundle ACL reconstruction than with the conventional single-bundle reconstruction. However, 1 original trial and the meta-analysis found that there were no differences in the results between the 2 types of reconstructions. Thus the utility of the anatomic double-bundle reconstruction has not yet been established. Our review does show how much evidence exists as to the benefits of double-bundle ACL reconstruction at present.

Current knowledge in the anatomy of the human anterior cruciate ligament

The anterior cruciate ligament (ACL) is one of the most frequently studied structures of the musculoskeletal system and continues to stimulate debate and challenges among researchers and surgeons. The ultimate goal of anatomic reconstruction surgery is to restore the native anatomy as much as possible. However, this requires thorough knowledge of its anatomy. The aim of this article is to review the current knowledge of the anatomy of ACL along with its macrostructural and ultrastructural properties.

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 degrees 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 degrees 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 degrees the posterolateral bundle pin was closest to the gastrocnemius tendon (mean 4.5 +/- 3.4 mm). At 130 degrees 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 degrees the anteromedial bundle guide pin was closest to the articular cartilage (mean 2.0 +/- 2.0 mm). At 110 degrees 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 degrees 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 degrees of knee flexion in order to move guide pin exit points away from important lateral knee structures.

Oblique femoral tunnel placement can increase risks of short femoral tunnel and cross-pin protrusion in anterior cruciate ligament reconstruction

BACKGROUND

A more horizontal femoral tunnel has been emphasized for contemporary anterior cruciate ligament (ACL) reconstruction. However, lowering the femoral tunnel may result in a shorter tunnel. In addition, a more horizontally placed femoral tunnel may have inadequate bone stock at the posterior portion of the tunnel, which can lead to protrusion of the cross-pin (Rigidfix) system for femoral fixation.

HYPOTHESIS

A more horizontal femoral tunnel position, particularly via the anteromedial (AM) portal technique, will reduce femoral tunnel length, and a more horizontal femoral tunnel position and anterior-to-posterior pin insertion will increase the risk of Rigidfix pin protrusion.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 10 cadaveric knees, we measured maximum lengths of the femoral tunnels at the positions of 11:30, 10:30, and 9:30 o'clock using the transtibial technique and at the 10:30 and 9:30 o'clock using the AM portal technique. Then, for each femoral tunnel via the transtibial technique at 11:30, 10:30, and 9:30 o'clock positions, tests were performed for 3 directions of Rigidfix pin insertion using the lateral epicondyle as an anatomical landmark, namely, 15 degrees anterior to posterior (A-P), neutral, and 15 degrees posterior to anterior (P-A). It was then determined whether pins protruded from the posterior cortex.

RESULTS

The lengths of femoral tunnels produced using the transtibial technique became shorter as the femoral starting position became more horizontal (51.1 mm, 40.0 mm, and 34.2 mm on average at the 11:30, 10:30, and 9:30 o'clock position, respectively). Tunnels made using the AM portal technique were significantly shorter than those made using the transtibial technique: by 7.6 mm at the 10:30 o'clock and 4.5 mm at the 9:30 o'clock positions on average (P < .001). In addition, increasing obliquity increased the likelihood of Rigidfix pin protrusion, especially when pins were inserted in the A-P direction.

CONCLUSION

The current effort to lower the femoral tunnel position in ACL reconstruction can shorten the tunnel length and compromise the graft fixation at the femur using the Rigidfix system.

CLINICAL RELEVANCE

When an intended femoral tunnel position is more horizontal than the 10:30 o'clock position for ACL reconstruction, a surgeon needs to be cautious regarding a short femoral tunnel, particularly when using the AM portal technique, and possible protrusion of the cross-pin (Rigidfix) fixator.

The location of femoral and tibial tunnels in anatomic double-bundle anterior cruciate ligament reconstruction analyzed by three-dimensional computed tomography models

BACKGROUND

Characterization of the insertion site anatomy in anterior cruciate ligament reconstruction has recently received increased attention in the literature, coinciding with a growing interest in anatomic reconstruction. The purpose of this study was to visualize and quantify the position of anatomic anteromedial and posterolateral bone tunnels in anterior cruciate ligament reconstruction with use of novel methods applied to three-dimensional computed tomographic reconstruction images.

METHODS

Careful arthroscopic dissection and anatomic double-bundle anterior cruciate ligament tunnel drilling were performed with use of topographical landmarks in eight cadaver knees. Computed tomography scans were performed on each knee, and three-dimensional models were created and aligned into an anatomic coordinate system. Tibial tunnel aperture centers were measured in the anterior-to-posterior and medial-to-lateral directions on the tibial plateau. The femoral tunnel aperture centers were measured in anatomic posterior-to-anterior and proximal-to-distal directions and with the quadrant method (relative to the femoral notch).

RESULTS

The centers of the tunnel apertures for the anteromedial and posterolateral tunnels were located at a mean (and standard deviation) of 25% +/- 2.8% and 46.4% +/- 3.7%, respectively, of the anterior-to-posterior tibial plateau depth and at a mean of 50.5% +/- 4.2% and 52.4% +/- 2.5% of the medial-to-lateral tibial plateau width. On the medial wall of the lateral femoral condyle in the anatomic posterior-to-anterior direction, the anteromedial and posterolateral tunnels were located at 23.1% +/- 6.1% and 15.3% +/- 4.8%, respectively. The proximal-to-distal locations were at 28.2% +/- 5.4% and 58.1 +/- 7.1%, respectively. With the quadrant method, anteromedial and posterolateral tunnels were measured at 21.7% +/- 2.5% and 35.1% +/- 3.5%, respectively, from the proximal condylar surface (parallel to the Blumensaat line), and at 33.2% +/- 5.6% and 55.3% +/- 5.3% from the notch roof (perpendicular to the Blumensaat line). Intraobserver and interobserver reliability was high, with small standard errors of measurement.

CONCLUSIONS

This cadaver study provides reference data against which tunnel position in anterior cruciate ligament reconstruction can be compared in future clinical trials.

Outcome of arthroscopic single-bundle versus double-bundle reconstruction of the anterior cruciate ligament: a preliminary 2-year prospective study

PURPOSE

The purpose of this study was to compare the clinical results of arthroscopic single-bundle and double-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

We designed a prospective study that included patients with an isolated ACL injury. From April 2004 to February 2007, of 147 patients who underwent ACL reconstruction, 113 were included in this study. We serially obtained clinical and radiologic data preoperatively and postoperatively. We compared preoperative data and data at 2 years postoperatively in patients who had undergone single-bundle ACL reconstruction versus patients who had undergone double-bundle ACL reconstruction. There were 50 single-bundle reconstructions and 63 double-bundle reconstructions. Anteroposterior stability was assessed objectively by anterior stress radiographs with the telos device (telos, Marburg, Germany) and the maximal manual test with the KT-2000 arthrometer (MEDmetric, San Diego, CA). Rotational stability was determined by lateral pivot-shift test. The clinical results were assessed by International Knee Documentation Committee and Orthopadische Arbeitsgruppe Knie scores and Tegner activity scale. In addition, we evaluated postoperative thigh circumference and range of motion.

RESULTS

Residual anteroposterior laxity determined at 2 years postoperatively by telos and KT-2000 was 1.74mm +/- 1.67mm and 1.79mm +/- 1.56mm, respectively, in the single-bundle reconstruction group and 1.63mm +/- 1.50mm and 1.61mm +/- 1.22mm, respectively, in the double-bundle reconstruction group. There were no statistically significant differences. For the lateral pivot-shift test done at 2 years postoperatively, there was no statistically significant difference. In addition, clinical results such as International Knee Documentation Committee score, Orthopadische Arbeitsgruppe Knie score, Tegner activity scale, thigh circumference, and range of motion showed no significant differences between the 2 groups.

CONCLUSIONS

Double-bundle reconstruction of the ACL by a method using 2 femoral tunnel and 2 tibial tunnels showed no differences in stability results or any other clinical aspects or in terms of patient satisfaction.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Effect of tibial drill angles on bone tunnel aperture during anterior cruciate ligament reconstruction

BACKGROUND

Anatomic reconstruction of the anterior cruciate ligament has received greater attention as patient outcome assessment has become increasingly sophisticated. A goal during anatomic reconstruction should be the creation of a tibial tunnel aperture that is similar in size and orientation to the native anterior cruciate ligament insertion. Aperture morphology depends primarily on three factors: (1) drill-bit diameter, (2) the angle at which the tunnel intersects the tibial plateau (drill-guide angle), and (3) the tibial tunnel orientation in the transverse plane (transverse drill angle). We evaluated the influence of the aforementioned factors on tibial bone-tunnel aperture size and orientation.

METHODS

With use of various drill-bit diameters at different drill-guide angles, tunnel aperture areas were calculated on the basis of an elliptical shape. The change in tunnel aperture orientation within the transverse plane (along the tibial plateau surface) was quantified by calculating the change in anteroposterior and mediolateral lengths of the aperture.

RESULTS

Use of a 9-mm drill-bit at a 45 degrees drill-guide angle created a 90-mm(2) bone-tunnel aperture area. Decreasing the drill-guide angle from 65 degrees to 30 degrees resulted in an increase in area of 81%. An aperture oriented 45 degrees relative to the orientation of the native insertion of the anterior cruciate ligament in the transverse plane fell short of the anatomic anteroposterior distance by 2.3 mm and exceeded the mediolateral distance by 1.4 mm on the basis of a 9-mm drill-bit at a drill-guide angle of 45 degrees.

CONCLUSIONS

During anterior cruciate ligament reconstruction, the drill-bit diameter, sagittal drill angle, and transverse drill angle can all affect tibial tunnel aperture size and orientation. An improperly sized and oriented tunnel aperture may increase the risk of damaging surrounding structures. An optimal combination of these parameters should be chosen during anatomic reconstruction of the anterior cruciate ligament.

Graft tension during active knee extension exercise in anatomic double-bundle anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to measure graft tension in vivo in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction during active knee extension, as well as to investigate the effect of loading a weight around the ankle on graft tension.

METHODS

Seven patients with chronic ACL injury underwent anatomic double-bundle ACL reconstruction. Two grafts were temporarily fixed to the 2 tension-adjustable force gauges on the anterior tibial cortex, after they were fixed on the femur. After the creep within the femur-ACL graft-tibia construct was removed, 10 N of the initial tension was applied to each graft at 20 degrees. First, tension to the anteromedial (AM) and posterolateral (PL) grafts was continuously measured during passive extension from 90 degrees to 0 degrees with the patient under general anesthesia. Then, after the patient was awoken from anesthesia, graft tension was again recorded while the knee was actively extended by the patient in the same manner. Finally, after a 2-kg weight was placed around the ankle, the tension of each graft was measured again during active knee extension by the patient himself or herself.

RESULTS

During passive extension motion, the tension of the AM graft was 19.3 +/- 4.7 N, whereas that of the PL graft was 24.5 +/- 5.9 N at 0 degrees. The tension of each graft increased when approaching full extension. During active knee extension motion, the tension of the AM graft was 24.0 +/- 6.1 N, whereas that of the PL graft was 30.8 +/- 7.3 N at 0 degrees. When the 2-kg weight was placed around the ankle during active motion, the tension was significantly higher than that with no weight at all flexion angles.

CONCLUSIONS

Graft tension was greater during active motion than that during passive motion, and graft tension during active motion increased with a weight placed around the ankle. The highest graft tension was 62.8 N at 0 degrees of flexion with a 2-kg weight placed around the ankle, when 20 N of initial tension was applied at 20 degrees of flexion in anatomic double-bundle ACL reconstruction. Thus care must be taken during active extension exercise with weights, especially in the first few weeks after ACL reconstruction, because graft tension increases with an increase in initial tension and easily reaches a critical level.

CLINICAL RELEVANCE

Our findings suggest that active knee extension exercise should be performed in moderation in the early phase after ACL reconstruction.

Comparison between single-and double-bundle anterior cruciate ligament reconstruction: a prospective, randomized, single-blinded clinical trial

BACKGROUND

Double-bundle ACL reconstruction popularity is increasing with the aim to reproduce native ACL anatomy and improve ACL reconstruction outcome. However, to date, only a few randomized clinical studies have been published.

PURPOSE

The aim of this study was to prospectively compare the clinical results of single- and double-bundle ACL reconstruction.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Seventy patients with a chronic unilateral ACL rupture who underwent arthroscopically assisted ACL reconstruction using a hamstring graft were randomized to receive a single- (SB) or double-bundle (DB) reconstruction. Both groups were comparable with regard to preoperative data. A double-incision surgical technique was adopted in both groups. The graft was fixed by looping the hamstring tendons around a bony (DB) or a metallic (SB) bridge on the tibial side and with interference screws reinforced with a staple on the femur. The same rehabilitation protocol was adopted. Outcome assessment was performed by a blinded, independent observer using the visual analog scale (VAS) score, the new International Knee Documentation Committee (IKDC) form, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and KT-1000 arthrometer evaluation.

RESULTS

All the patients reached a minimum follow-up of 2 years. No differences between the 2 groups were observed in terms of KOOS and IKDC subjective score. A statistically significant difference in favor of the DB group was found with the VAS (P < .03). The objective IKDC final scores showed statistically significantly more "normal knees" in the DB group than in the SB group (P = .03). There was 1 stability failure in the DB group and 3 in the SB group. The KT-1000 arthrometer data showed a statistically significant decrease in the average anterior tibial translation in the DB group (1.2 mm DB vs 2.1 mm SB; P < .03). The incidence of a residual pivot-shift glide was 14% in DB and 26% in SB (P = .08).

CONCLUSION

In the 2-year minimum follow-up, DB ACL reconstructions showed better VAS, anterior knee laxity, and final objective IKDC scores than SB. However, longer follow-up and accurate instrumented in vivo rotational stability assessment are needed.

Anatomy of normal human anterior cruciate ligament attachments evaluated by divided small bundles

BACKGROUND

Double-bundle anterior cruciate ligament (ACL) reconstruction has several potential advantages over single-bundle reconstruction with hamstring tendons. However, there are still controversies regarding tunnel placement in tibial and femoral attachments.

HYPOTHESIS

The macroscopically normal ACL consists of small bundles about 1 mm in diameter. Detailed observation of the divided smaller bundles will achieve better understanding of the tunnel placement in anatomic ACL reconstruction.

STUDY DESIGN

Descriptive laboratory study.

METHODS

This study used 20 cadaveric knees. The ACL was divided into anteromedial and posterolateral bundles, then separated into 10 small bundles of 2-mm diameters, with preservation of their attachment sites marked with color markers. The positional relationship between the femoral and tibial attachments of each small bundle was investigated.

RESULTS

A layered positional correlation of small bundles was found between the tibial and femoral attachments. Small bundles aligned in the anterior-posterior direction in the tibia corresponded to the bundles aligned in a high-low direction in the femur in flexion. The femoral attachment pattern was relatively similar in each specimen; however, the tibial attachment showed 2 patterns: an oblique type (12 of 20) and a transverse type (8 of 20). The posterior portion of the posterolateral bundle was separately attached to the medial and lateral portions of the tibial attachment. There was no fibrous insertion in the center of the posterior portion of the ACL tibial attachment in any specimen. In this bare area, there was fat tissue and vascular bundles.

CONCLUSION

Small bundles constituting the ACL showed a relatively layered arrangement between 2 attachments. The tibial attachment showed 2 patterns of oblique and transverse types, and the vascular bundles were located in the center of the posterolateral bundle.

CLINICAL RELEVANCE

The results of this study of the normal ACL will provide insights for surgeons when placing grafts during anatomic ACL reconstruction.

Radiologic evaluation of the insertion sites of the 2 functional bundles of the anterior cruciate ligament using 3-dimensional computed tomography

BACKGROUND

Anterior cruciate ligament reconstruction with a double-bundle technique requires exact tunnel positioning. Reference values for the anatomic insertions are necessary for radiographic intra- and postoperative control and fluoroscopy-based navigation.

HYPOTHESIS

The femoral and tibial insertions of the anteromedial bundle (AMB) and posterolateral bundle (PLB) of the anterior cruciate ligament can be described using standardized computed tomography scans.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The insertion sites of the AMB and PLB were macroscopically identified and tagged by copper wire in 12 specimens. Computed tomography scans with predefined reconstructions were performed. Femorally, the geometric center of the insertions were determined in the sagittal view and described in a deep-high 10 x 10 grid. Tibially, the insertions were described as the ratio between the geometric center of the insertion sites with respect to the mediolateral and sagittal diameter of the tibia in frontal and sagittal reconstruction, respectively. The tibial insertions were described using a 10 x 10 grid in axial orientation.

RESULTS

The geometric midpoints of the insertion areas at the femur of the AMB and PLB were located on the reticule at x = 21% + or - 3% and y = 22% + or - 2% for the AMB and x = 27% + or - 3% and y = 45% + or - 3% for the PLB. In the sagittal plane, the center of the tibial insertion was located at 41% + or - 3% and 52% + or - 3% of the tibial diameter from the anterior border for the AMB and PLB, respectively. The geometric centers of the tibial insertions in axial view were x = 52% + or - 2% and y = 37% + or - 3% for the AMB and x = 50% + or - 2% and y = 48% + or - 3% for the PLB.

CONCLUSION

The insertion site characteristics of the AMB and PLB can be evaluated by predefined reconstructions of computed tomography scans. Clinical relevance These results can serve as orientation landmarks for intra- and postoperative radiographic control and fluoroscopic-based navigation.

Effect of knee flexion angle on length and orientation of posterolateral femoral tunnel drilled through anteromedial portal during anatomic double-bundle anterior cruciate ligament reconstruction

PURPOSE

Our purpose was to evaluate the radiologic orientation and length of the posterolateral (PL) femoral tunnel when drilled through the anteromedial (AM) portal at 90 degrees, 110 degrees, and 130 degrees of flexion.

METHODS

In 9 fresh cadaveric knees the anterior cruciate ligament was excised and 2.4-mm guidewires were drilled through the center of the PL bundle footprint through an accessory AM portal. Pins were advanced, in a retrograde manner, until flush with the notch wall and left in place. Outcomes were measured by use of plain anteroposterior, lateral, and tunnel radiographs to determine tunnel orientation and clock position, and direct measurement was performed to determine the intraosseous length, the shortest distance to the posterior bone cortex, and the distance to the lateral collateral ligament attachment on the lateral aspect of the femoral condyle.

RESULTS

With regard to tunnel orientation, each increase in knee flexion angle resulted in a more horizontal tunnel on both the lateral and anteroposterior views. On the tunnel view, the PL guidewire became more vertical with knee flexion. The mean clock position was 9 o'clock (standard deviation [SD], 00:12). No significant difference in the intraosseous length of the guidewires was observed. According to our hypothesis, knee flexion influenced the PL tunnel characteristics. At 90 degrees of flexion, the guidewire may blow out the posterior cortex of the lateral femoral condyle.

CONCLUSIONS

A PL femoral tunnel drilled through the AM portal becomes more horizontal with bending of the knee during drilling. At 90 degrees, the tunnel is at risk of back wall blowout.

Validation of the position of the femoral tunnels in anatomic double-bundle ACL reconstruction with 3-D CT scan

This study compares the positioning of femoral AM and PL tunnels obtained with specific ancillary instruments during anatomic double-bundle ACL reconstruction with the native ACL footprint using three-dimensional computed tomography (3-D CT). In 35 consecutive patients, anatomic double-bundle ACL reconstruction was performed with specific ancillary instruments. Three-dimensional CT reconstruction of both knees was performed using the volume rendering technique. In the controls (contralateral knee, with intact ACL), the angle between the longitudinal axis of the footprint and the axis of the femur, the "footprint angle" (FA) was measured. On the involved side, using the axis passing through the tunnel centers, FA was also measured. In both the groups, footprint's length and width, and distances to cartilage margins were measured. FA was 28.1 degrees +/- 5.0 degrees in the controls and 32.9 degrees +/- 15.8 degrees on the involved side (n.s.). There was no statistical difference between the two groups for the other morphometric parameters: footprint's length and width, and distances to cartilage margins. Using specific ancillary instruments the morphometric parameters of the reconstructed femoral ACL footprint were similar to the native ACL.

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 degrees , 90 degrees and 110 degrees 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 degrees , 4.3 +/- 2.2 mm at 90 degrees , and 6.0 +/- 2.6 mm at 110 degrees , while those of the PL bundle were 4.0 +/- 2.2 mm at 70 degrees , 3.4 +/- 1.9 mm at 90 degrees , and 4.2 +/- 2.5 mm at 110 degrees . The best results were obtained at 90 degrees 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 degrees when determining the graft placement in double-bundle reconstruction to prevent misplacement of the graft usually in a disto-proximal direction.

The effect of tunnel placement on bone-tendon healing in anterior cruciate ligament reconstruction in a goat model

BACKGROUND

Misplacement of the bone tunnels is one of the main causes of graft failure of anterior cruciate ligament surgery.

HYPOTHESIS

Anatomic tunnel placement in anterior cruciate ligament surgery reconstruction will lead to improved outcomes, including biological ingrowth and biomechanical properties, when compared with nonanatomic tunnel placement.

STUDY DESIGN

Controlled laboratory study.

METHODS

Anterior cruciate ligament surgery reconstructions were performed on 3 different groups of goats (1 anatomic tunnel placement group and 2 different nonanatomic tunnel placement groups, with 10 goats in each group). For each group of 10 knees, 3 knees were used for histologic evaluation (bone tunnel enlargement, number of osteoclasts at the bone tendon interface, and revascularization of the graft) and 7 knees were used for biomechanical testing (anterior tibial translation, in situ force, cross-sectional area, and ultimate failure load). Animals were sacrificed at 12 weeks after surgery.

RESULTS

The anatomic tunnel placement group showed less tunnel enlargement on the tibial side, fewer osteoclasts on both the tibial and femoral sides, and more vascularity in the femoral side when compared with the 2 nonanatomic reconstruction groups. Biomechanically, the anatomic tunnel placement group demonstrated less anterior tibial translation and greater in situ force than both nonanatomic tunnel placement groups.

CONCLUSION

Anatomic tunnel placement leads to superior biological healing and biomechanical properties compared with nonanatomic placement at 12 weeks after anterior cruciate ligament surgery reconstruction in a goat model.

CLINICAL RELEVANCE

The findings of this study demonstrate the importance of anatomic tunnel placement in anterior cruciate ligament surgery reconstruction.

Replication of the range of native anterior cruciate ligament fiber length change behavior achieved by different grafts: measurement using computer-assisted navigation

BACKGROUND

The native anterior cruciate ligament (ACL) does not behave as a simple bundle of fibers with constant tension but as a continuum of ligament fibers with differential length change during knee flexion/extension. Computer-assisted navigation can be used to assess length change in different fibers within the native ACL and to evaluate how different reconstruction grafts replicate the range of native ligament fiber length change behavior.

HYPOTHESIS

Anterior cruciate ligament reconstruction graft size and configuration (single-vs double-bundle) are deciding factors as to how much of the native ACL fiber length change behavior is replicated.

STUDY DESIGN

Controlled laboratory study.

METHODS

The fiber length change behavior of the entire native ACL was assessed by measuring the length change pattern of representative anteromedial (AM) and posterolateral (PL) bundle fibers (1 at the center and 4 at the periphery of each bundle). The tibial and femoral ACL attachment areas in 5 fresh-frozen cadaveric knees were digitized, and the length change of each representative fiber was recorded during knee flexion/extension using an image-free, optical navigation system. Subsequently, single-bundle ACL reconstructions of different diameters (6, 9, and 12 mm) positioned at the center of the overall native femoral and tibial attachment sites were modeled to assess how much of the range of ligament fiber length change of the native ligament was captured. This was compared with a double-bundle graft using 6-mm-diameter AM and PL grafts positioned at the centers of the femoral and tibial attachment sites of each separate bundle.

RESULTS

The 6-, 9-, and 12-mm single-bundle grafts simulated 32%, 51%, and 66% of the ligament fiber length change behavior of the native ACL, respectively. The length change patterns in these grafts were similar to the central fibers of the native ACL: the PL fibers of the AM bundle and AM fibers of the PL bundle. However, even a 12-mm graft did not represent the most AM and PL native fibers. The 6-mm AM and PL bundle grafts (equivalent in cross-sectional area to a 9-mm single-bundle graft) simulated 71% of the native ACL and better captured the extremes of the range of native ligament fiber length change.

CONCLUSION

Increasing single-bundle graft size appears to capture more of the range of native ACL fiber length change. However, for a similar graft cross-sectional area, a 2-bundle graft simulates the length change behavior of the native ligament more precisely and thus may better emulate the synergistic actions of anisometric and isometric fibers of the native ligament in restraining knee laxity throughout the range of flexion.

CLINICAL RELEVANCE

The range of native ACL fiber length change behavior is better replicated by larger diameter grafts but may be best reproduced by double-bundle reconstruction.

In vivo anterior cruciate ligament elongation in response to axial tibial loads

BACKGROUND

The knowledge of in vivo anterior cruciate ligament (ACL) deformation is fundamental for understanding ACL injury mechanisms and for improving surgical reconstruction of the injured ACL. This study investigated the relative elongation of the ACL when the knee is subject to no load (<10 N) and then to full body weight (axial tibial load) at various flexion angles using a combined dual fluoroscopic and magnetic resonance imaging (MRI) technique.

METHODS

Nine healthy subjects were scanned with MRI and imaged when one knee was subject to no load and then to full body weight using a dual fluoroscopic system (0 degrees-45 degrees flexion angles). The ACL was analyzed using three models: a single central bundle; an anteromedial and posterolateral (double functional) bundle; and multiple (eight) surface fiber bundles.

RESULTS

The anteromedial bundle had a peak relative elongation of 4.4% +/- 3.4% at 30 degrees and that of the posterolateral bundle was 5.9% +/- 3.4% at 15 degrees. The ACL surface fiber bundles at the posterior portion of the ACL were shorter in length than those at the anterior portion. However, the peak relative elongation of one posterolateral fiber bundle reached more than 13% whereas one anteromedial fiber bundle reached a peak relative elongation of only about 3% at 30 degrees of flexion by increasing the axial tibial load from no load to full body weight.

CONCLUSIONS

The data quantitatively demonstrated that under external loading the ACL experiences nonhomogeneous elongation, with the posterior fiber bundles stretching more than the anterior fiber bundles.

A systematic review of the femoral origin and tibial insertion morphology of the ACL

Transtibial single bundle anterior cruciate ligament (ACL) reconstruction has been the gold standard for several years. This technique often fails to restore native ACL femoral origin and tibial insertion anatomy of the ACL. Recently, there is a strong trend towards a more anatomical approach in single and double bundle ACL reconstruction. Using the anatomic double bundle structure of the ACL as a principle, the entirety of both tibial insertion and femoral origin of both bundles, the posterolateral and anteromedial, may be restored. Reflected by recent publications over the past two years, there is an increasing interest in the anatomy of the ACL. In the current study, a PubMed literature search was performed looking for measurements of the ACL femoral origin and tibial insertion. These studies show a large variability in the size and the anatomy of the femoral origin and tibial ACL insertion using different methods and specimens. The diversity of reported measurements makes clinical application of these data difficult at best. Thus, it is of paramount importance to understand the individual variations in size and shape of the ACL femoral origin and tibial ACL insertion. This study is a systematic review of the morphology of the ACL femoral origin and tibial insertion as reported in the literature.

Roentgenographic measurement study for locating femoral insertion site of anterior cruciate ligament: a cadaveric study with X-Caliper

The purpose of this study was to determine the relationships of the anterior cruciate ligament (ACL) femoral insertion site with femoral bony landmarks and develop a new method of location. Sixteen unpaired normal Chinese human cadaveric knees were used. Femoral insertion sites of the ACL were marked with metal wires. Four pairs of bony landmarks were selected: anatomical axis of distal femur (A) and parallel tangent of posterior condyles (B); tangent of anterior condyles parallel to landmark A (C) and landmark B; Blumensaat's line (D) and parallel tangent of distal condyles (E); and tangent of posterior condyles (F) and parallel tangent of anterior condyles (G). The X-Caliper was used to measure the distance between the centre of the insertion site and each pair of bony landmarks. The ratio of distances to each pair of bony landmark was calculated. Clock position of the ACL femoral footprint was measured on anteroposterior (AP) roentgenograms at 90 degree flexion. The centre of the ACL footprint was found at 65.3% +/- 1.1% between A and B, 78.1% +/- 1.0% between B and C, 38.3% +/- 2.7% between D and E, and 43.1% +/- 4.6% between F and G. The distances to bony landmarks A, B, D, and E have smaller variations. Blumensaat's line and the anatomical axis of the distal femur were regarded as more useful and made location of the insertion site more precise. A parallelogram made up of these two bony landmarks can be used. On AP roentgenograms, the centre of the femoral footprint should be moved to lower than the 10:00 o'clock (2:00) position.

DARTHROSCOPIC DOUBLE- BUNDLE RECONSTRUCTION OF ANTERIOR CRUCIATE LIGAMENT USING HAMSTRING TENDON GRAFTS - FIXATION WITH TWO INTERFERENCE SCREWS

Surgical procedures for double-bundle reconstruction of anterior cruciate ligament, which currently use semitendinous and gracilis tendon grafts, have been described in the last decade. Most of the techniques utilize twice the hardware used in single-bundle reconstructions. We report an original anterior cruciate ligament double-bundle reconstruction technique using semitendinous and gracilis tendon grafts, maintaining their tibial bone insertions with two tibial and two femoral tunnels. A simplified and precise outside-in femoral drilling technique is utilized, and the graft fixation is made utilizing only two interference screws.

Assessment and augmentation of symptomatic anteromedial or posterolateral bundle tears of the anterior cruciate ligament

The anterior cruciate ligament (ACL) consists of 2 anatomic and functional bundles, the anteromedial (AM) and posterolateral (PL) bundle. Depending on the mechanism of injury, there are different injury patterns to the AM and PL bundles, demonstrating a wide spectrum of partial ACL tears. Clinical interest has recently focused on establishing pre- and intraoperative ways of assessing the different types of symptomatic partial ACL injuries in order to perform an individual ACL augmentation according to the specific injury pattern. Theoretically, sparing the intact parts of the ACL may increase vascularization and proprioception, may optimize the accuracy of the ACL reconstruction, and may result in better stability and improved clinical outcome for the patient. However, an isolated reconstruction of the AM or PL bundle is an advanced arthroscopic procedure that requires a precise pre- and intraoperative diagnostic assessment of the injury pattern, an exact arthroscopic knowledge of the anatomic insertion sites, a careful debridement, and bone tunnel placement while preserving the intact parts of the ACL. This article will present the concept of partial ACL tears and will describe the clinical, radiologic, and arthroscopic assessment and the arthroscopic technique of isolated AM or PL bundle augmentation.

Intraoperative biomechanical evaluation of anatomic anterior cruciate ligament reconstruction using a navigation system: comparison of hamstring tendon and bone-patellar tendon-bone graft

BACKGROUND

Recently, more anatomic anterior cruciate ligament reconstructions have been developed to improve knee laxity.

PURPOSE

The objective of this study is to assess knee kinematics after double-bundle reconstruction with hamstring tendon and after anatomically oriented reconstruction with a patellar tendon using navigation during surgery.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Eighty knees received double-bundle reconstruction with a hamstring tendon graft, and 45 knees received anatomically oriented reconstruction with a patellar tendon graft. Before reconstruction, knee laxity was measured using a navigation system. After the posterolateral bundle or anteromedial bundle was temporarily fixed during double-bundle reconstruction, knee laxity was measured to assess the function of each bundle. After double-bundle reconstruction or anatomically oriented reconstruction with patellar tendon, knee laxity was measured in the same manner.

RESULTS

Both double-bundle reconstruction and anatomically oriented reconstruction similarly improved knee laxity compared with before reconstruction in all knee flexion angles. Regarding the function of the anteromedial and posterolateral bundles in double-bundle reconstruction, the 2 grafts showed contrasting behavior. The posterolateral bundle restrained tibial displacement mainly in knee extension, whereas the anteromedial bundle restrained it more in the knee flexion position. The posterolateral bundle has a more important role in controlling rotation of the tibia than the anteromedial bundle.

CONCLUSION

Although the posterolateral bundle has an important role in the extension position, the anteromedial bundle is more important in the flexion position. Therefore, both bundles should be reconstructed to improve knee laxity throughout knee range of motion. Even with single-bundle reconstruction using a patellar tendon, anatomic reconstruction might improve knee laxity similar to double-bundle reconstruction.

Anatomic double-bundle anterior cruciate ligament reconstruction with anatomic aimers

Graft positioning is a key issue in anterior cruciate ligament (ACL) reconstruction and even more sensitive in double-bundle reconstruction, where 2 tunnels have to be drilled within the ACL footprints at both the femoral and tibial insertion sites. Specific ancillary instruments have been developed to facilitate the positioning of the 4 sockets necessary when performing anatomic double-bundle ACL reconstruction. This technical note describes the rationale and the step-by-step method of using the specific aimers developed for this purpose. However, a prerequisite for successful double-bundle ACL reconstruction is a good knowledge of ACL footprint anatomy.

Double-bundle reconstruction of the anterior cruciate ligament using the transtibial technique

We present an arthroscopic surgical procedure for double-bundle transtibial anterior cruciate ligament reconstruction with 2 tibial and femoral tunnels using autologous semitendinosus and gracilis tendons. The first aim is to attempt to create the femoral tunnels correctly through the tibial tunnels. To achieve this, a new tibial guide was used that permitted the simultaneous preparation of the anteromedial and posterolateral tibial tunnels. The intra-articular landmark is the tibial spine region, whereas the extra-articular landmarks are the anterior profile of the medial collateral ligament and the anterior tibial apophysis. We also describe transverse femoral fixation with biopins (1 for each femoral tunnel) after the preparation of the 2 tibial and femoral tunnels.

Femoral insertions of the anteromedial and posterolateral bundles of the anterior cruciate ligament: morphometry and arthroscopic orientation models for double-bundle bone tunnel placement--a cadaver study

PURPOSE

The purpose of this study was to analyze the femoral insertions of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) and to develop arthroscopic orientation models for double-bundle (DB) bone tunnel placement.

METHODS

The femoral insertions of the AM and PL bundles were dissected in 50 human cadaveric knees, documented on digital photographs, and quantified with a digital image analysis system.

RESULTS

The insertion areas of both bundles were significantly larger in men (53 mm(2) for AM and 45 mm(2) for PL) than in women (39 mm(2) for AM and 39 mm(2) for PL), and the average ACL insertion area was significantly larger in left knees than in right knees. According to the "femoral center angle model," the centers of the AM and PL bundles were horizontally aligned when the femoral shaft axis was lifted 12 degrees from the horizontal plane or when the knee was flexed to 102 degrees . In this position the center of the AM bundle was 3 to 4 mm "lower" (arthroscopic terminology) to the over-the-top position, and the distance of the PL bundle to the "shallow" articular cartilage of the lateral femoral condyle was 6 mm. According to the "modified femoral clock wall model," the average centers of the AM and PL bundles were both aligned at 1 o'clock for a left knee and at 11 o'clock for a right knee in 102 degrees of knee flexion.

CONCLUSIONS

The average femoral insertion areas of the ACL and the AM and PL bundles were significantly larger in men compared with women and in left knees compared with right knees. According to the femoral center angle model, the AM and PL insertions are aligned horizontally in an average of 102 degrees of knee flexion, resulting in one commuted time for the AM and PL bundles in the modified femoral clock wall model. Both models support reproducible and reliable arthroscopic AM and PL bone tunnel placement. With regard to a mean anatomic anteroposterior length of the femoral ACL insertion of 14 to 15 mm, adequate DB bone tunnel placement should be possible in most cases.

CLINICAL RELEVANCE

This study provides an anatomic description of the femoral AM and PL insertions including gender differences, landmarks, and arthroscopic orientation models for DB bone tunnel placement.

Influence of knee flexion angle on femoral tunnel characteristics when drilled through the anteromedial portal during anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to determine the influence of knee flexion angle for drilling the femoral tunnel during anterior cruciate ligament (ACL) reconstruction via the anteromedial (AM) portal on resulting tunnel orientation and length.

METHODS

In 8 fresh cadaveric knees, the ACL was excised and 2.4-mm guidewires were drilled through the AM bundle footprint using a 5-mm endofemoral aimer via the AM portal. We compared knee flexion angles of 90 degrees , 110 degrees , 130 degrees , and maximum flexion. Anteroposterior-, lateral-, and tunnel-view radiographs were measured to determine tunnel orientation, o'clock position, and direct measurement to determine intra-osseous tunnel length.

RESULTS

With regard to tunnel orientation, each increase in knee flexion angle resulted in significantly more horizontal tunnel both on the anteroposterior view and on the lateral view. While on the tunnel view, the pin became more vertical with knee flexion. At 90 degrees , tunnel length was significantly less (27 +/- 9 mm) than at greater angles, and the guidewires were either resting against the posterior cortex or breaching it.

CONCLUSIONS

The results of this study show the knee flexion angle influences the position of the femoral drilling. It appears in the current study that 110 degrees is optimum, while the 90 degrees pin leads to short tunnel and is so close to the posterior wall there are high risks of posterior wall blow out when drilling the tunnel at its final diameter. Also, 130 degrees of knee flexion is responsible for high tunnel acuity and, finally, maximum flexion being quite variable from one specimen to another cannot be recommended.

CLINICAL RELEVANCE

Tunnels drilled through the AM portal at 90 degrees are at risk of back wall blow out.

Anatomical and nonanatomical double-bundle anterior cruciate ligament reconstruction: importance of femoral tunnel location on knee kinematics

BACKGROUND

Studies have suggested that double-bundle anterior cruciate ligament reconstruction may restore intact knee kinematics better than single-bundle anterior cruciate ligament reconstruction. Although the tunnel position of the femoral anteromedial bundle is well established, the effects of different posterolateral bundle positions on knee kinematics are unknown.

HYPOTHESIS

Double-bundle anterior cruciate ligament reconstruction with an anatomical (shallow) femoral posterolateral bundle tunnel placement will restore knee kinematics more closely than will a nonanatomical (deep) femoral posterolateral bundle tunnel position.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 12 human cadaveric knees, the kinematics of the intact knee, anterior cruciate ligament-deficient knee, and double-bundle anterior cruciate ligament-reconstructed knees with nonanatomical femoral posterolateral tunnel placement and anatomical posterolateral bundle placement were determined in response to a 134-N anterior tibial load and a combined rotatory load of 10 N x m valgus and 4 N x m internal tibial rotation using a robotic/universal force moment sensor testing system. Statistical analyses were performed using a 2-way analysis of variance test.

RESULTS

Double-bundle anterior cruciate ligament reconstruction with nonanatomical posterolateral bundle placement showed significantly higher anterior tibial translation under anterior tibial and combined rotatory load than did the intact knee at 0 degrees and 30 degrees of knee flexion (P < .05). Reconstruction with an anatomical posterolateral tunnel placement restored the intact knee kinematics and showed significantly lower anterior tibial translation under anterior tibial and combined rotatory load when compared with reconstruction with nonanatomical posterolateral placement (P < .05).

CONCLUSION

Double-bundle anterior cruciate ligament reconstruction using the anatomical posterolateral bundle tunnel position restores the intact knee kinematics. A nonanatomical posterolateral bundle position results in rotatory instability.

CLINICAL RELEVANCE

Double-bundle anterior cruciate ligament reconstruction should be performed using anatomical tunnel placement of the anteromedial and posterolateral bundles. Nonanatomical double-bundle reconstruction may fail to show any clinical superiority to single-bundle reconstruction and should be avoided.

Anatomical analysis of the anterior cruciate ligament femoral and tibial footprints

BACKGROUND

The current trend in anterior cruciate ligament (ACL) reconstruction has shifted to anatomical double-bundle (DB) reconstruction, which reproduces both the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of the ACL. Navigation systems have also been recently introduced to orthopedic surgical procedures, including ACL reconstruction. In DB-ACL reconstruction, the femoral and tibial tunnel positions are very important, but a representation of the ACL footprint under an arthroscopic view has not been established even though navigation systems have been introduced. The purpose of this study was to evaluate the anatomical footprints of both the AMB and the PLB using the representation method for application to arthroscopic DB-ACL reconstruction using a navigation system, and to evaluate the validity of the currently determined footprint position compared with other representation methods.

METHODS

Thirty-six cadaveric knees were used for an anatomical evaluation of footprints of the AMB and PLB. On the tibial side, the ACL footprints were evaluated using an original method. On the femoral side, the ACL footprints were evaluated using Watanabe's method and three other methods: (1) the quadrant method, (2) Mochizuki's method, and (3) Takahashi's method.

RESULTS

The central points of the ACL footprints were represented almost constantly. The present data is in accordance with previous measurement data.

CONCLUSION

This study showed that the anatomical data of the ACL femoral and tibial footprints determined with Watanabe's method at the femoral side and our original method at the tibial side were both applicable to arthroscopic surgery with a navigation system.

Strategies to improve anterior cruciate ligament healing and graft placement

Recent improvements in anterior cruciate ligament (ACL) reconstruction have been notable for strategies to improve ACL healing and to improve graft placements. The controversial choice of 1-bundle or 2-bundle grafts requires an advanced knowledge of native ACL insertional anatomy and an appreciation for the kinematic effects of graft placements. Understanding the limitations of surgical techniques to place tunnels is important. Once grafts are placed, new biologic strategies to promote intra-articular and intraosseous healing are evolving. Although these biologic engineering strategies are currently experimental, they are projected for clinical application in the near future.

The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament. Part 2: femoral attachment

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 degrees to the femoral long axis. The results from this study could be used to guide ACL reconstruction techniques.

Femoral tunnel placement in single-bundle anterior cruciate ligament reconstruction: a cadaveric study relating transtibial lateralized femoral tunnel position to the anteromedial and posterolateral bundle femoral origins of the anterior cruciate ligament

BACKGROUND

There is controversy regarding the necessity of reconstructing both the posterolateral and anteromedial bundles of the anterior cruciate ligament.

HYPOTHESIS

A laterally oriented transtibial drilled femoral tunnel replaces portions of the femoral footprints of the anteromedial and posterolateral bundles of the anterior cruciate ligament.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Footprints of the anteromedial and posterolateral bundles of the anterior cruciate ligament were preserved on 7 matched pairs (5 female, 2 male) of fresh-frozen human cadaveric femurs (14 femurs total). Each femur was anatomically oriented and secured in a custom size-appropriate, side-matched replica tibia model to simulate transtibial retrograde drilling of a 10-mm femoral tunnel in each specimen. The relationship of the tunnel relative to footprints of both bundles of the anterior cruciate ligament was recorded using a Microscribe MX digitizer. The angle of the femoral tunnel relative to the vertical 12-o'clock position was recorded for all 14 specimens; only 10 specimens were used for footprint measurements.

RESULTS

On average, the 10-mm femoral tunnel overlapped 50% of the anteromedial bundle (range, 2%-83%) and 51% of the posterolateral bundle (range, 16%-97%). The footprint of the anteromedial bundle occupied 32% (range, 3%-49%) of the area of the tunnel; the footprint of the posterolateral bundle contributed 26% (range, 7%-41%). The remainder of the area of the 10-mm tunnel did not overlap with the anterior cruciate ligament footprint. The mean absolute angle of the femoral tunnel as measured directly on the specimen was 48 degrees (range, 42 degrees-53 degrees) from vertical, corresponding to approximately a 10:30 clock face position on a right knee.

CONCLUSION

Anterior cruciate ligament reconstruction using a laterally oriented transtibial drilled femoral tunnel incorporates portions of the anteromedial and posterolateral bundle origins of the native anterior cruciate ligament.

CLINICAL RELEVANCE

A laterally oriented transtibial drilled femoral tunnel placed at the 10:30 position (1:30 for left knees) reconstructs portions of the anteromedial and posterolateral bundles of the anterior cruciate ligament.

The effects of different tensioning strategies on knee laxity and graft tension after double-bundle anterior cruciate ligament reconstruction

BACKGROUND

Double-bundle anterior cruciate ligament reconstruction replicates the 2 functional bundles of the native ligament, the posterolateral and the anteromedial, to control anteroposterior and rotational laxity.

HYPOTHESIS

Double-bundle anterior cruciate ligament reconstruction laxity should be affected by the way grafts are tensioned.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fourteen intact cadaveric knees were instrumented in a 6 degree of freedom rig, and kinematics throughout flexion-extension were recorded with an electromagnetic system under a 90-N anterior force or a 5-N.m internal rotation torque. Anteromedial and posterolateral bundle bovine extensor tendon grafts were fixed to load cells on the tibia, and tension was adjusted to match the intact knee anteroposterior laxity with 3 different protocols: (1) anteromedial bundle first and then posterolateral bundle at 90 degrees and 20 degrees of flexion, respectively; (2) posterolateral bundle first and then anteromedial bundle at 20 degrees and 90 degrees of flexion, respectively; and (3) both bundles together at 20 degrees of flexion. Finally, a single-bundle graft positioned at 10 o'clock was tensioned at 20 degrees of flexion.

RESULTS

Lower graft tensions were required to match intact knee laxity in double-bundle anterior cruciate ligament reconstruction. Tension patterns with knee flexion were independent from the tensioning protocol. Protocols 1 and 2 overconstrained anteroposterior laxity, whereas protocol 3 matched intact knee anteroposterior laxity throughout the range of motion. The single-bundle reconstructions had excess anteroposterior laxity in flexion. Rotations were better restored with double-bundle protocols 2 and 3.

CONCLUSION

Knee laxity after double-bundle anterior cruciate ligament reconstruction is affected by the sequence in which the grafts are tensioned.

CLINICAL RELEVANCE

Double-bundle anterior cruciate ligament reconstruction ensures better laxity restoration than does single bundle when both bundles are fixed together.

Description of the attachment geometry of the anteromedial and posterolateral bundles of the ACL from arthroscopic perspective for anatomical tunnel placement

The anterior cruciate ligament (ACL) consists of an anteromedial bundle (AMB) and a posterolateral bundle (PLB). A reconstruction restoring the functional two-bundled nature should be able to approximate normal ACL function better than the most commonly used single-bundle reconstructions. Accurate tunnel positioning is important, but difficult. The purpose of this study was to provide a geometric description of the centre of the attachments relative to arthroscopically visible landmarks. The AMB and PLB attachment sites in 35 dissected cadaver knees were measured with a 3D system, as were anatomical landmarks of femur and tibia. At the femur, the mean ACL centre is positioned 7.9 +/- 1.4 mm (mean +/- 1 SD) shallow, along the notch roof, from the most lateral over-the-top position at the posterior edge of the intercondylar notch and from that point 4.0 +/- 1.3 mm from the notch roof, low on the surface of the lateral condyle wall. The mean AMB centre is at 7.2 +/- 1.8 and 1.4 +/- 1.7 mm, and the mean PLB centre at 8.8 +/- 1.6 and 6.7 +/- 2.0 mm. At the tibia, the mean ACL centre is positioned 5.1 +/- 1.7 mm lateral of the medial tibial spine and from that point 9.8 +/- 2.1 mm anterior. The mean AMB centre is at 3.0 +/- 1.6 and 9.4 +/- 2.2 mm, and the mean PLB centre at 7.2 +/- 1.8 and 10.1 +/- 2.1 mm. The ACL attachment geometry is well defined relative to arthroscopically visible landmarks with respect to the AMB and PLB. With simple guidelines for the surgeon, the attachments centres can be found during arthroscopic single-bundle or double-bundle reconstructions.

Osseous landmarks of the femoral attachment of the anterior cruciate ligament: an anatomic study

PURPOSE

Anatomic tunnel placement is critical to the success of anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to determine qualitatively and quantitatively the osseous landmarks of femoral attachment of the ACL.

METHODS

The femoral attachment of the ACL was studied histologically in seven human fetuses, arthroscopically in 60 patients who underwent ACL surgery, and grossly in 16 cadaveric knees. Three-dimensional laser digitizer pictures of the cadaveric specimens were taken to quantify length, area, and angulations of the femoral attachment of the ACL.

RESULTS

Two different osseous landmarks were detected. An osseous ridge that runs from proximal to distal ends was present in all the arthroscopic patients and cadaveric knees. It was named "lateral intercondylar ridge." Another osseous landmark between the femoral attachment of the anteromedial (AM) and posterolateral (PL) bundles running from anterior to posterior was observed in 6 out of 7 fetuses, 49 out of 60 arthroscopic patients, and 13 out of 16 cadaveric knees. It was named "lateral bifurcate ridge." A change of slope between the femoral attachment of the AM and PL bundles was observed in all specimens studied. The femoral attachment of the AM bundle formed an angle with the PL bundle of 27.6 degrees +/- 8.8 degrees and a radius of curvature of 25.7 +/- 12 mm. The area of the entire ACL footprint, AM, and PL bundle was 196.8 +/- 23.1 mm(2), 120 +/- 19 mm(2), and 76.8 +/- 15 mm(2), respectively.

CONCLUSIONS

The ACL femoral attachment has a unique topography with a constant presence of the lateral intercondylar ridge and often an osseous ridge between AM and PL femoral attachment, the lateral bifurcate ridge.

CLINICAL RELEVANCE

These findings may assist surgeons to perform ACL surgery in a more anatomic fashion.

Second-look arthroscopic evaluations of anatomic double-bundle anterior cruciate ligament reconstruction: relation with postoperative knee stability

PURPOSE

The purpose of this study was to test the hypothesis that both the anteromedial and posterolateral bundles may be clearly visible after anatomic double-bundle reconstruction, as well as that a strong relation may exist between the appearance of the 2 bundles and the clinical evaluation.

METHODS

A prospective study was performed based on 178 consecutive patients who underwent anatomic double-bundle anterior cruciate ligament reconstruction with 2 hamstring tendon autografts in the unilateral knee. To develop arthroscopic diagnostic criteria, clinical evaluations were carried out at 1 to 2 years concerning the anterior laxity, the pivot-shift test, the Lysholm knee score, and the International Knee Documentation Committee evaluation, and 136 of the 178 patients underwent second-look arthroscopy shortly before or after the clinical examinations that are the basis of this study. The focus of the second-look arthroscopy was on graft thickness, apparent tension, and synovium coverage of the bundle.

RESULTS

Second-look arthroscopy showed that the anteromedial bundle was evaluated as excellent in 79.5% of the knees, fair in 16.7%, and poor in 3.8% and the posterolateral bundle was evaluated as excellent in 75.8%, fair in 21.2%, and poor in 3.0%. There was a significant difference in the anterior laxity and the pivot-shift test among the arthroscopically observed categories. Between the knees with second-look arthroscopy and those without it, there were no significant differences in all clinical evaluations.

CONCLUSIONS

Both the anteromedial and posterolateral bundles were clearly visible after the anatomic double-bundle anterior cruciate ligament reconstruction at 1 to 2 years after surgery. There was a significant difference in the anterior laxity and pivot-shift test in patients in category I, which comprised those who had excellent anteromedial and posterolateral bundles, compared with those in category II or III, which comprised those in whom either 1 or both of the bundles was scored as less than excellent.

LEVEL OF EVIDENCE

Level II, development of diagnostic criteria on the basis of consecutive patients with universally applied reference gold standard.

Anatomical limitations of transtibial drilling in anterior cruciate ligament reconstruction

BACKGROUND

Recommended techniques for transtibial drilling in anterior cruciate ligament reconstruction are based on strategies to prevent graft impingement and preserve tibial tunnel length. The limitations of this drilling technique may restrict the ability to centralize tunnels in the anterior cruciate ligament footprints.

HYPOTHESIS

A transtibial drilling starting point to centralize the tibial and femoral tunnels in their respective footprints can be identified, but it will result in a short tibial tunnel.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The femoral and tibial attachments of the anterior cruciate ligament were characterized in 12 fresh-frozen cadaveric knees. Knees were secured in 70 degrees and 90 degrees of flexion. A guide pin was drilled antegrade through the central femoral and proximal anterior cruciate ligament attachment sites through the central tibial anterior cruciate ligament attachment site to exit on the anterior tibia.

RESULTS

In 90 degrees of flexion using the central femoral and tibial attachment sites, the exit point of the pin on the anterior tibia was 14.1 mm from the tibial joint line and 20.9 mm anterior to the superficial medial collateral ligament. The length of the pin in the tibia was 30.6 mm. Extending the knee to 70 degrees or directing the pin through the proximal femoral anterior cruciate ligament attachment moved the starting point less than 4 mm from this point.

CONCLUSION

The transtibial technique can produce tunnels centered in the anterior cruciate ligament footprints, but a starting point close to the tibial joint line is required. This will result in a relatively short tibial tunnel.

CLINICAL RELEVANCE

If tunnels centered in the anterior cruciate ligament attachment sites are desired with the transtibial drilling technique, then a short tibial tunnel is necessary. A short tibial tunnel may compromise graft fixation and graft incorporation, or it may result in a tunnel length-graft length mismatch. An alternative drilling strategy might be employed.

Arthroscopic identification of the anterior cruciate ligament posterolateral bundle: the figure-of-four position

Anatomic double-bundle reconstruction in anterior cruciate ligament (ACL) tears has been developed during the last few years. Although anteromedial (AM) bundle reconstruction is routinely performed, finding the femoral attachment of the posterolateral (PL) bundle remains a problem. We describe how a classic arthroscopic position, the figure-of-4 position, allows the PL bundle to be easily recognized. During flexion, the femoral attachment of the PL bundle describes an arc around the AM femoral attachment. The femoral attachment of the AM bundle is the center of rotation of the ACL, which explains the isometric behavior of this bundle. After 45 degrees of flexion, the PL femoral attachment becomes anterior to the AM femoral attachment. The AM bundle is tight during flexion, whereas the PL bundle is under tension when the knee is extended and becomes lax with knee flexion. At 90 degrees of flexion, the PL bundle is difficult to identify because it is lax; only its femoral insertion lies anterior to the AM bundle close to the articular cartilage of the lateral condyle. The use of an additional tibial varus torque and internal rotation (i.e., the figure-of-4 position) tightens the PL bundle and enhances the visualization of its insertion, allowing for easy identification of this bundle.