Computer-assisted Surgery for Anterior Cruciate Ligament Reconstruction

Evaluation of the intraoperative kinematics during double-bundle anterior cruciate ligament reconstruction using a navigation system

Background/objective

There is controversy regarding the biomechanical function of the anteromedial (AM) and posterolateral (PL) bundles in isolated tibiofemoral rotation during double-bundle anterior cruciate ligament (ACL) reconstruction. This study aimed to evaluate the biomechanical function of the AM and PL bundles of the ACL using a computer navigation system.

Methods

This study involved 15 patients who underwent double-bundle ACL reconstruction. Anteroposterior and isolated rotational knee laxity were measured with a navigation system. The measurements were performed four times, namely, before fixation, after temporary PL bundle fixation, after AM bundle fixation, and after double-bundle reconstruction. With knee flexion ranging from 20° to 60°, we continuously measured the anterior tibial displacement under an anterior drawer stress (100 N using a spring balance). The total range of tibial rotation was also measured under an external and internal rotational torque of 3 Nm.

Results

Fixation of either the AM or the PL bundle significantly reduced the anteroposterior displacement at all knee flexion angles. Although the anteroposterior displacement after AM bundle fixation was relatively similar throughout the range of motion (2.4–3.2 mm), the anteroposterior displacement after PL bundle fixation increased continuously with knee flexion (2.2–4.6 mm). With respect to the total range of tibial rotation under external and internal rotational torque, there was no significant difference between AM and PL bundle fixation throughout the range of motion. The total range of tibial rotation was significantly reduced only on double-bundle reconstruction at 20° and 25° knee flexion compared to the pre-reconstruction range (P = 0.015 and 0.036, respectively).

Conclusion

The AM and PL bundles function differently for controlling anterior knee laxity throughout the range of motion. The function of the AM and PL bundles was similar for controlling isolated tibiofemoral rotation. Isolated tibiofemoral rotation was significantly controlled only on double-bundle reconstruction at knee flexion angles of 20° and 25°.

Accurate Positioning of Femoral and Tibial Tunnels in Single Bundle Anterior Cruciate Ligament Reconstruction Using the Indigenously Made Bernard and Hurtle Grid on a Transparency Sheet and C-arm

Many factors determine the outcome of the anterior cruciate ligament reconstruction surgery. The single most important factor, also well within the control of a surgeon, is tunnel placement. It is difficult to accurately determine the center of the anterior cruciate ligament foot print, and many a times it is also difficult to accurately define the intercondylar and bifurcate ridge. This makes determination of the accurate entry point of the guidewire difficult. We have printed our indigenously formed grid (equidistant boxes) on an old-fashioned transparency sheet. We use a fluoroscopy (C-arm) shot intraoperatively in the lateral position and superimpose this sheet to determine the position of the guidewire by calculating the percentage of boxes. We aim at 27.7% in proximal to distal and 37.5% in anterior to posterior on the femur side and 45% in front to back and medial to lateral on the tibial side. C-arm is freely available, but the inbuilt grid facility may be available in only the higher version of C-arms. Our indigenously designed grid can be easily used across the globe with ease to achieve accuracy in tunnel placement without violating anatomy and without any extra cost.

Current use of navigation system in ACL surgery: a historical review

PURPOSE

The present review aims to analyse the available literature regarding the use of navigation systems in ACL reconstructive surgery underling the evolution during the years.

METHODS

A research of indexed scientific papers was performed on PubMed and Cochrane Library database. The research was performed in December 2015 with no publication year restriction. Only English-written papers and related to the terms ACL, NAVIGATION, CAOS and CAS were considered. Two reviewers independently selected only those manuscripts that presented at least the application of navigation system for ACL reconstructive surgery.

RESULTS

One hundred and forty-six of 394 articles were finally selected. In this analysis, it was possible to review the main uses of navigation system in ACL surgery including tunnel positioning for primary and revision surgery and kinematic assessment of knee laxity before and after different surgical procedures. In the early years, until 2006, navigation system was mainly used to improve tunnel positioning, but since the last decade, this tool has been principally used for kinematics evaluation. Increased accuracy of tunnel placement was observed using navigation surgery, especially, regarding femoral, 42 of 146 articles used navigation to guide tunnel positioning. During the following years, 82 of 146 articles have used navigation system to evaluate intraoperative knee kinematic. In particular, the importance of controlling rotatory laxity to achieve better surgical outcomes has been underlined.

CONLUSIONS

Several applications have been described and despite the contribution of navigation systems, its potential uses and theoretical advantages, there are still controversies about its clinical benefit. The present papers summarize the most relevant studies that have used navigation system in ACL reconstruction. In particular, the analysis identified four main applications of the navigation systems during ACL reconstructive surgery have been identified: (1) technical assistance for tunnel placement; (2) improvement in knowledge of the kinematic behaviour of ACL and other structures; (3) comparison of effectiveness of different surgical techniques in controlling laxities; (4) navigation system performance to improve the outcomes of ACL reconstruction and cost-effectiveness.

LEVEL OF EVIDENCE

IV.

Clinical advantages of image-free navigation system using surface-based registration in anatomical anterior cruciate ligament reconstruction

PURPOSE

To evaluate the clinical advantages of a navigation system developed with an emphasis on attaining an appropriate femoral tunnel length and posterior wall margin with no posterior wall blowout, as well as having accurate tunnel positioning, in anatomical anterior cruciate ligament reconstruction (ACLR).

METHODS

Ten freshly frozen human knees were transected at mid-femur and mid-tibia. Each knee specimen underwent arthroscopic single-bundle anterior cruciate ligament reconstruction using the outside-in technique, with two knees by manual ACLR (control group) and another eight knees by only the navigational ACLR without arthroscopic assistance (experimental group). The position/orientation information of tunnel entry point, tunnel length, and posterior wall distance of pre-, intra-, and postoperative tunnel were recorded, and the reliability and errors among them were evaluated.

RESULTS

From comparison of the 3D models for preoperative planning and postoperative reconstruction, the mean differences for navigational femoral tunnelling and arthroscopic-assisted femoral tunnelling were recorded, respectively: (1) tunnel entry position, 1.4 mm (SD 0.3) versus 4.9 mm; (2) tunnel length, 0.7 mm (SD 0.2), similar to 0.6 mm in arthroscopic-assisted femoral tunnelling, and (3) posterior wall distance, 0.5 mm (SD 0.2), much smaller than 4.7 mm for arthroscopic-assisted femoral tunnelling. The intraclass correlation coefficients, calculated to determine the accuracy and reliability of navigational femoral tunnelling, showed excellent internal consistency that ranged from 0.965 to 0.989 for tunnel length and from 0.810 to 0.953 for posterior wall distance.

CONCLUSION

Navigation systems with enhancement of the registration accuracy by the developed system are feasible in anatomical ACLR, in reducing surgical failures such as short tunnel length or posterior wall breakage of distal femur. The present study revealed that computer navigation could aid in avoiding major mistakes in exact positioning and posterior wall blowout and help in attaining appropriate length for femoral tunnelling in anatomical ACLR.

Variability of tunnel positioning in fluoroscopic-assisted ACL reconstruction

PURPOSE

Intraoperative fluoroscopy has been proposed as a feasible method to improve the accuracy of anatomical tunnel positioning. However, it has so far not been determined, whether this technique reduces the variability of tunnel positioning in a clinical set-up. Therefore, the purpose of this study was to determine the variability of tunnel positions applying intraoperative fluoroscopy.

METHODS

Femoral and tibial tunnel positions of 112 fluoroscopic ACL reconstruction cases were determined according to validated radiological measurement methods. Mean positions, standard deviations and ranges were calculated to determine the variability of the tunnel positions. Subgroup variability analysis was performed to analyse cases in which tunnel positions were corrected.

RESULTS

Applying intraoperative fluoroscopy, the variability of tunnel positions was found to be 3 % at the femur (range 15.4 %) and 2.3 % at the tibia (9.7 %). In 34 cases (30.0 %), non-satisfactory tunnel positions were identified and could be corrected achieving more accurate positions regarding to radiological parameters (14× femur, 16× tibia, 4× femur and tibia).

CONCLUSIONS

The results of the presented study indicate that intraoperative fluoroscopy allows to identify non-accurate tunnel positions regarding to radiological criteria. The determined low variability indicates that fluoroscopic-based ACL reconstruction can be recommended as a feasible, easy and effective adjunct that enables surgeons to create more consistent and reliable tunnel positions in ACL reconstruction.

LEVEL OF EVIDENCE

IV.

Accuracy of a computer-assisted planning and placement system for anatomical femoral tunnel positioning in anterior cruciate ligament reconstruction

BACKGROUND

Femoral tunnel positioning is a difficult, but important factor in successful anterior cruciate ligament (ACL) reconstruction. Computer navigation can improve the anatomical planning procedure besides the tunnel placement procedure.

METHODS

The accuracy of the computer-assisted femoral tunnel positioning method for anatomical double bundle ACL-reconstruction with a three-dimensional template was determined with respect to both aspects for AM and PL bundles in 12 cadaveric knees.

RESULTS

The accuracy of the total tunnel positioning procedure was 2.7 mm (AM) and 3.2 mm (PL). These values consisted of the accuracies for planning (AM:2.9 mm; PL:3.2 mm) and for placement (about 0.4 mm). The template showed a systematic bias for the PL-position.

CONCLUSIONS

The computer-assisted templating method showed high accuracy for tunnel placement and has promising capacity for application in anatomical tunnel planning. Improvement of the template will result in an accurate and robust navigation system for femoral tunnel positioning in ACL-reconstruction.

Use of a fluoroscopic overlay to assist arthroscopic anterior cruciate ligament reconstruction

BACKGROUND

A growing body of evidence supports the importance of anatomic tunnel positioning in the success of anterior cruciate ligament (ACL) reconstruction, which stimulates the need for technologies to aid surgeons in achieving accurate anatomic tunnel placement. Intraoperative fluoroscopy is potentially one such technology, while its efficacy and usability have yet to be established.

PURPOSE

To investigate the performance of an intraoperative fluoroscopic overlay in guiding tunnel placement during ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty cadaveric knees underwent computed tomography (CT) scans and arthroscopic digitization of ACL insertion sites. The outlines of the digitized insertion sites were mapped to the corresponding CT-acquired bone models through a co-registration procedure. Twenty orthopaedic surgeons performed simulated ACL reconstructions, each on a randomly assigned cadaveric knee, first without and then with the aid of a fluoroscopic overlay system. The overlay system displayed on a lateral fluoroscopic image targets points representing the locations of the ACL insertion sites estimated from the literature data. Surgeons were allowed to adjust their tunnel positions under the guidance of the fluoroscopic image. Their initial, intermediate, and final positions were documented and compared with the target points as well as the native insertion sites.

RESULTS

Surgeons demonstrated significant (P < .01) improvements in femoral and tibial tunnel placements relative to the target points from an average distance of 3.9 mm to 1.6 mm on the femur and 2.1 mm to 0.9 mm on the tibia. The improvements toward the knee-specific actual insertion sites were significant on the tibial side but not on the femoral side.

CONCLUSION

Surgeons can be successfully guided with fluoroscopy to create more consistent femoral and tibial tunnels during ACL reconstruction. More research is warranted to develop better population representations of the locations of natural insertion sites.

CLINICAL RELEVANCE

Intraoperative fluoroscopy can be an effective, easy, and safe method for improving tunnel positioning during ACL reconstruction.

Application of a computerised navigation technique to assist arthroscopic anterior cruciate ligament reconstruction

PURPOSE

Based on biomechanical cadaver studies, anatomical double-bundle reconstruction of the anterior cruciate ligament (ACL) was introduced to achieve better stability in the knee, particularly in respect of rotatory loads. Previously, the success of ACL reconstruction was believed to be mainly dependent on correct positioning of the graft, irrespective of the number of bundles for which computer-assisted surgery was developed to avoid malpositioning of the tunnel. The aim of this study was to compare rotational and translational stability after computer-navigated standard single-bundle and anatomical double-bundle ACL reconstruction.

METHODS

The authors investigated 42 consecutive patients who had undergone the single-bundle or double-bundle ACL reconstruction procedure using autogenous hamstring tendon grafts and ENDOBUTTON fixation in patients who had been followed up for a minimum of 24 months. Post-operative anteroposterior and rotational laxity was measured with the KT3000 and compared between groups.

RESULTS

Both surgical procedures significantly improve rotational and translational stability compared to the preoperative ACL-deficient knee (P<0.05). No significant differences were registered between groups with regard to anteroposterior displacement of the tibia. The International Knee Documentation Committee (IKDC) and Lysholm scores were significantly higher in the double-bundle group. However, the results were excellent in both groups.

CONCLUSIONS

The use of computer-assisted ACL reconstruction, which is a highly accurate method of graft placement, could be useful for inexperienced surgeons to avoid malposition. Long-term results of at least five years are needed to determine whether double-bundle ACL reconstruction, which was associated with improved rotational laxity and significantly better IKDC and Lysholm scores compared to the standard single-bundle ACL reconstruction procedure, exerts an influence in terms of avoiding osteoarthritis or meniscus degeneration.

Reliability of early postoperative radiographic assessment of tunnel placement after anterior cruciate ligament reconstruction

PURPOSE

To evaluate the interobserver and intraobserver reliability of radiographic assessment of tunnel placement in anterior cruciate ligament reconstruction.

METHODS

Seven sports fellowship-trained orthopaedic surgeons in the Multicenter Orthopaedic Outcomes Network (MOON) group participated in the study. We prospectively enrolled 54 consecutive patients after primary anterior cruciate ligament reconstruction. Postoperative plain radiographs were obtained including a full-extension anteroposterior view of the knee, a lateral view of the knee in full extension, and a notch view at 45° of flexion (Rosenberg view). Three blinded reviewers performed 8 different radiographic measurements including those of Harner and Aglietti/Jonsson. Intraclass correlation coefficients were used to determine reliability of the measurements. Intrarater reliability was assessed by repeated measurements of a subset of 20 patient images from 1 institution, and inter-rater reliability was assessed by use of all 54 sets of films from a total of 4 institutions.

RESULTS

Intraobserver reliability for femoral measures ranged from none to substantial, with notch height having the worst results. Intraobserver reliability was moderate to almost perfect for tibial measures. Interobserver reliability ranged from slight to moderate for femoral measures. The Harner method for determining tunnel depth was more reliable than the Aglietti/Jonsson method. Interobserver reliability for tibial measures ranged from fair to substantial. The presence of metal interference screws did not improve reliability of measurements.

CONCLUSIONS

Postoperative radiographs are easily obtained, but our results show that radiographic measurements are of quite variable reliability, with most of the results falling into the fair to moderate categories.

Does computer navigation system really improve early clinical outcomes after anterior cruciate ligament reconstruction? A meta-analysis and systematic review of randomized controlled trials

Inaccurate tunnel placement is an important cause of failure in conventional anterior cruciate ligament (ACL) reconstruction. Controversy currently exists over the usefulness of computer-assisted navigation systems in addressing this problem. Five randomized or quasi-randomized, controlled trials comparing computer-navigated versus conventional technique in ACL reconstructions until December 1, 2009 were identified through a systematical database search. The clinical outcomes of the trials were analyzed by Lachman test, pivot-shift test, International Knee Documentation Committee knee score, Lysholm score, and Tegner score. Mean difference or risk ratio with 95% confidence interval was calculated using a fixed-effects or random-effects model. Heterogeneity across the studies was also assessed. We found that the use of computer-assisted navigation systems led to additional operative time (8-17min). No significant differences between computer-navigated and conventional groups were found in terms of knee stability and functional assessment during short-term follow-up. The role of computer-assisted navigation systems on clinical performance and longevity needs further investigation in large sample, long-term randomized trials.

Measurement of rotational laxity of the knee: in vitro comparison of accuracy between the tibia, overlying skin, and foot

BACKGROUND

Posterolateral corner (PLC) injuries are difficult to diagnose and cause significant morbidity. The ideal method for the dial test and its accuracy remain unclear.

PURPOSE

This study compares the accuracy of measuring tibial external rotation at the skeletal level to measuring the patella-tubercle angle (PTA) and the thigh-foot angle (TFA) in the supine position to assess the most accurate method to measure rotation during the dial test.

STUDY DESIGN

Controlled laboratory study.

METHODS

Measurements were compared simultaneously using rotational goniometers at a cutaneous splint over the tibia, at a foot splint, and directly from the tibial skeleton. Six lower limbs were used. The femur was held rigidly and the knee tested at 90° and 30° of flexion. External rotation torque up to 8 N·m was applied through the foot splint, and the rotations were measured by 2 testers.

RESULTS

Measurements at the tibial splint and directly on the tibia showed significant correlation at both knee flexion angles. The mean tibial external rotation was 24° at 90° of flexion and 26° at 30° of flexion (P < .05). The soft tissue effect caused the tibial splint to overestimate rotations by a mean of 6° and 9° at 90° and 30° of flexion, respectively. Foot splint measurements did not correlate significantly with tibial rotation, overestimating rotations by a mean of 103%. Intratester and intertester intraclass correlations were significant for the skin-mounted tibial splint measurements at both flexion angles but not for foot splint measurements at either flexion angles.

CONCLUSION

Rotation of the foot did not accurately represent the tibial external rotation at the knee, which could be measured more accurately by an instrument resting on the skin via a molded tibial splint. These results suggest that the PTA, and not the TFA, should be used in the dial test. This would support the use of the supine position during the dial test.

CLINICAL RELEVANCE

The dial test is a commonly used method for diagnosing PLC injuries. This study helps to identify the ideal position and measuring points to use for this test; measurements based on the tibia were more accurate than those that used rotation of the foot.

Three-dimensional anatomic evaluation of the anterior cruciate ligament for planning reconstruction

Anatomic study related to the anterior cruciate ligament (ACL) reconstruction surgery has been developed in accordance with the progress of imaging technology. Advances in imaging techniques, especially the move from two-dimensional (2D) to three-dimensional (3D) image analysis, substantially contribute to anatomic understanding and its application to advanced ACL reconstruction surgery. This paper introduces previous research about image analysis of the ACL anatomy and its application to ACL reconstruction surgery. Crucial bony landmarks for the accurate placement of the ACL graft can be identified by 3D imaging technique. Additionally, 3D-CT analysis of the ACL insertion site anatomy provides better and more consistent evaluation than conventional “clock-face” reference and roentgenologic quadrant method. Since the human anatomy has a complex three-dimensional structure, further anatomic research using three-dimensional imaging analysis and its clinical application by navigation system or other technologies is warranted for the improvement of the ACL reconstruction.

Computer-navigated surgery in anterior cruciate ligament reconstruction: are radiographic outcomes better than conventional surgery?

PURPOSE

The use of computer navigation systems in anterior cruciate ligament (ACL) has been the subject of debate. However, there is a lack of systematic review to analyze the radiographic outcomes after computer-navigated ACL reconstruction.

METHODS

We searched, in duplicate, Medline, Embase, and Web of Science databases for randomized controlled trials (RCTs)/quasi-RCTs comparing conventional versus computer-navigated ACL reconstruction. Two reviewers independently extracted the data. Radiographic outcomes reported in a majority of included trials were meta-analyzed using the Mantel-Haenszel test statistic.

RESULTS

After applying our eligibility criteria, we had 5 trials for systematic review and data synthesis. There was no evidence of statistical heterogeneity between all included studies. Both navigated and conventional ACL reconstructions placed the tibial tunnel in acceptable positions. The risk of notch impingement was reduced in the navigated group in comparison with the conventional group.

CONCLUSIONS

A computer navigation systems may reduce variation from optimal graft alignment and notch impingement. However, there is a need for further high-quality studies with long-term follow-up, so as to prove the clinical significance of these findings.

LEVEL OF EVIDENCE

Level II, systematic review of randomized controlled trials.

Rotational and translational laxity after computer-navigated single- and double-bundle anterior cruciate ligament reconstruction

Based on biomechanical cadaver studies, anatomic double-bundle reconstruction of the anterior cruciate ligament (ACL) was introduced to achieve better stability in the knee, particularly in respect of rotatory loads. Previously, the success of ACL reconstruction was believed to be mainly dependent on correct positioning of the graft, irrespective of the number of reconstructed bundles for which computer-assisted surgery was developed to avoid malpositioning of the tunnel. The aim of the present study is to compare rotational and translational stability after computer-navigated standard single-bundle, and anatomic double-bundle ACL reconstruction. The authors investigated 55 consecutive patients who had undergone the single-bundle or double-bundle ACL reconstruction procedure with the use of autogenous hamstring tendon grafts and EndoButton fixation, and the patients had been followed for a minimum period of 24 months. Intraoperative, anteroposterior and rotational laxity was measured with the computer navigation system, and compared between groups. Both surgical procedures significantly reduced anteroposterior displacement (AP) and internal rotation (IR) of the tibia compared to the pre-operative ACL-deficient knee (P < 0.05). No significant differences were registered between groups with regard to anteroposterior displacement of the tibia. A significantly greater reduction in internal rotation was noted in the double-bundle group (15.6 degrees) compared to the single-bundle group (7.1 degrees). The IKDC and Lysholm score were significantly higher in the double-bundle group. However, the results were excellent in both groups. The use of a computer-assisted ACL reconstruction, which is a highly accurate method of graft placement, could be useful for inexperienced surgeons to avoid malposition. Whether double-bundle ACL reconstruction, which was associated with improved rotational laxity and significantly better IKDC and Lysholm scores compared to the standard single-bundle ACL reconstruction procedure, provide an influence in terms of avoiding osteoarthritis or meniscus degeneration, long-term results of at least 5 years are needed.

Tension degradation of anterior cruciate ligament grafts with dynamic flexion-extension loading: a biomechanical model in porcine knees

PURPOSE

This study investigates the influence of various femoral anterior cruciate ligament graft fixation methods on the amount of tension degradation and the initial fixation strength after cyclic flexion-extension loading in a porcine knee model.

METHODS

One hundred twenty porcine digital extensor tendons, used as 4-stranded free tendon grafts, were fixated within porcine femoral bone tunnels by use of extracortical button, cross-pin, or interference screw fixation. One hundred twenty porcine patellar tendon-bone grafts were fixated by use of cross-pin, interference screw, or press-fit fixation. Each femur-graft complex was submitted to cyclic flexion-extension loading for 1,000 cycles throughout different loading ranges, and the total loss of tension was determined. After cyclic testing, the grafts were loaded to failure, and the data were compared with a pullout series without cyclic loading.

RESULTS

Tension degradation after 1,000 cycles of flexion-extension loading averaged 62.6% +/- 10.0% in free tendon grafts and 48.9% +/- 13.35% in patellar tendon-bone grafts. There was no influence of the loading range on the total amount of tension degradation. The total amount of tension degradation was the highest with interference screw fixation of free tendon and patellar tendon-bone grafts. Despite excessive loss of tension, the initial fixation strength of the femur-graft complex was not reduced.

CONCLUSIONS

The method of femoral graft fixation significantly influenced tension degradation during dynamic flexion-extension loading. Femoral graft fixation methods that secure the graft close to the tunnel entrance and that displace the graft substance from the center of the bone tunnel show the largest amount of tension degradation during cyclic flexion-extension loading. The graft substance, not the fixation site, was the weakest link of the graft complex within this investigation.

CLINICAL RELEVANCE

We believe that the graft fixation method should be considered when aiming to improve the precision of femoral graft placement in anterior cruciate ligament reconstruction.

Equal kinematics between central anatomic single-bundle and double-bundle anterior cruciate ligament reconstructions

PURPOSE

The purpose of this study was to compare the kinematics of a central anatomic single-bundle anterior cruciate ligament (ACL) reconstruction with a double-bundle ACL reconstruction by use of hamstring grafts and anatomic tunnel placement.

METHODS

Anterior tibial translation and rotation were measured with a computer navigation system in 8 pairs of fresh-frozen cadaveric knees by use of a 133-N anterior force, an internal and external torque of 10 Nm, and an anterior force (133 N) combined with an internal rotation torque (10 Nm). Tests were performed at 30 degrees and 60 degrees of flexion with the ACL intact, the ACL transected, and after reconstruction of one side of a pair with either a single or a double-bundle construct.

RESULTS

At 30 degrees of flexion, cutting the ACL increased anterior translation under an anterior force (P < .0001), an internal rotation torque (P = .02), and a combined anterior force plus internal rotation torque (P = .01). At 60 degrees of flexion, transecting the ACL led to increased anterior translation only when an anterior force was used (P < .0001). Both single- and double-bundle reconstructions restored normal kinematics at 30 degrees and 60 degrees of knee flexion.

CONCLUSIONS

Central anatomic single-bundle ACL reconstruction with tunnels centered within the tibial and femoral insertions and double-bundle ACL reconstruction can restore normal anterior translation to the knee under anterior and rotational loads applied at 30 degrees and 60 degrees of flexion.

CLINICAL RELEVANCE

The primary kinematic effect of an ACL injury is an increase in anterior tibial translation, but there is no significant change in maximum internal or external rotation. Single- and double-bundle ACL reconstructions are equally effective in restoring normal anterior translation to the knee under both anterior and rotational loads.