Biomechanical comparison of three anatomic ACL reconstructions in a porcine model

Purpose  

Different tunnel configurations have been used for double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. However, controversy still exists as to whether three-tunnel DB with double-femoral tunnels and single-tibial tunnel (2F-1T) or with single-femoral tunnel and double-tibial tunnels (1F-2T) better restores intact knee biomechanics than single-bundle (SB) ACL reconstruction. The purpose was to compare the knee kinematics and in situ force in the grafts among SB and two types of three-tunnel DB ACL reconstructions performed in an anatomic fashion.     

ACL mismatch reconstructions: influence of different tunnel placement strategies in single-bundle ACL reconstructions on the knee kinematics

To evaluate the influence of tibial and femoral tunnel position in ACL reconstruction on knee kinematics, we compared ACL reconstruction with a tibial and femoral tunnel in anteromedial (AM-AM reconstruction) and in posterolateral footprint (PL-PL reconstruction) with a reconstruction technique with tibial posterolateral and femoral anteromedial tunnel placement (PL-AM reconstruction). In 9 fresh-frozen human cadaveric knees, the knee kinematics under simulated Lachman (134 N anterior tibial load) and a simulated pivot shift test (10 N/m valgus and 4 N/m internal tibial torque) were determined at 0°, 30°, 60°, and 90° of flexion. Kinematics were recorded for intact, ACL-deficient, and single-bundle ACL reconstructed knees using three different reconstruction strategies in randomized order: (1) PL-AM, (2) AM-AM and (3) PL-PL reconstructions. Under simulated Lachman test, single-bundle PL-AM reconstruction and PL-PL reconstructions both showed significantly increased anterior tibial translation (ATT) at 60° and 90° when compared to the intact knee. At all flexion angles, AM-AM reconstruction did not show any statistical significant differences in ATT compared to the intact knee. Under simulated pivot shift, PL-AM reconstruction resulted in significantly higher ATT at 0°, 30°, and 60° knee flexion and AM-AM reconstructions showed significantly higher ATT at 30° compared to the intact knee. PL-PL reconstructions did not show any significant differences to the intact knee. AM-AM reconstructions restore the intact knee kinematics more closely when compared to a PL-AM technique resembling a transtibial approach. PL-PL reconstructions showed increased ATT at higher flexion angles, however, secured the rotational stability at all flexion angles. Due to the independent tibial and femoral tunnel location, a medial portal technique may be superior to a transtibial approach.     

A comparative study of single-and double-bundle ACL reconstructions in sheep

Work in vitro has previously shown superior restoration of knee stability using a double-bundle anterior cruciate ligament (ACL) reconstruction compared with single bundles taken through the condyle or ‘over the top’. This paper describes an animal study designed to compare the three ACL reconstructions in vivo, in order to collect data that could support the clinical use of a double-bundle reconstruction. The three methods were compared in three groups of eight sheep, the ovine ACL having a distinct double-bundle structure. Biomechanically matched polyester fibre implants were used, with 6 months in vivo. The three methods led to similar intra-articular fibrous tissue integration of the implants and no evidence of implant damage, and biomechanical testing found greater laxity than normal for all three groups. The double-bundle group, however, had more joint surface degeneration than the other groups. It was concluded that clinical use of the double-bundle reconstruction was not indicated by the results of this experiment, in view of the more complex surgery and lack of superior performance.     

The concept of complete footprint restoration with guidelines for single- and double-bundle ACL reconstruction

Purpose  

This article introduces guidelines for single- (SB) and double-bundle (DB) ACL reconstruction based on the concept of complete footprint restoration. The goal is to reconstruct a maximum of anterior cruciate ligament (ACL) insertion site area to regain a maximum of ACL function. The concept is based on the hypothesis that the restored biomechanical envelope of the knee is a function of reconstructed ACL insertion site area.     

Current concepts in anatomic single- and double-bundle anterior cruciate ligament reconstruction

An anterior cruciate ligament (ACL) tear is one of the most common orthopedic sport injuries. The ACL consists of 2 functional bundles-the anteromedial and posterolateral-which are named for the position of their insertion sites on the tibia. Anatomic ACL reconstruction can be defined as the restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. Some biomechanical studies have demonstrated that anatomic ACL reconstruction can restore knee motion significantly similar to that of the normal knee, as compared with traditional, nonanatomic single-bundle procedures. In vivo kinematic studies have also shown that nonanatomic single-bundle reconstruction fails to restore normal dynamic knee stability in all cases. Accurate restoration of knee kinematics with anatomic ACL reconstruction is critical to protect against the possibility that nonatomic sugical technique could result in early osteoarthritis, which is common in patients who sustain ACL tears. Surgical techniques for ACL reconstruction vary, and if different aspects of the surgery are compared for superiority (eg, single- vs double-bundle techniques), it is necessary that both procedures meet criteria to be designated as "anatomic." By emphasizing the importance of restoring the native anatomy of the knee, surgeons can give their patients the best chance at restoration of joint function and preservation of long-term knee health.     

Inferior results after revision ACL reconstructions: a comparison with primary ACL reconstructions

Purpose

Anterior cruciate ligament (ACL) ruptures are common, especially among young athletes, and such injuries may have considerable impact on both sport careers and everyday life. ACL reconstructions are successful for most patients, but some suffer from persistent giving-way symptoms and/or re-ruptures requiring revision surgery. The aim of this study was to evaluate the results after revision ACL reconstructions and compare them with the results in a control group consisting of primary ACL reconstructions.

Methods

This retrospective study included 56 patients undergoing revision ACL reconstruction and 52 patients receiving primary ACL reconstructions. The follow-up evaluation included clinical examination, instrumented laxity testing, testing of muscle strength, Tegner activity score, Lysholm score, Knee injury and osteoarthritis outcome score (KOOS) and radiological grading of osteoarthritis.

Results

The median time from the last ACL reconstruction to follow-up was 90 months in the revision ACL reconstruction group and 96 months in the primary ACL reconstruction group. The revision group had significantly inferior KOOS and Lysholm scores compared with the primary group. Patients in the revision group also showed greater laxity measured with the pivot shift test, a larger reduction in the Tegner activity score, reduced muscle strength in the injured knee, and more severe radiological osteoarthritis; however, no difference in anterior-posterior translation was found.

Conclusion

Inferior results were found on several of the testing parameters in the revision group compared with the primary group. Patients should receive this information prior to revision ACL reconstructions.

Level of evidence

III.     

Prospective randomized comparison of anatomic single- and double-bundle anterior cruciate ligament reconstruction

Purpose

To determine if anatomic double-bundle anterior cruciate ligament (ACL) reconstruction is superior to anatomic single-bundle reconstruction in restoring the stabilities and functions of the knee joint.

Methods

A prospective randomized clinical study was done to compare the results of 32 cases of anatomic single-bundle ACL reconstruction and 34 cases of anatomic double-bundle ACL reconstruction with average follow-up of 16.3 ± 3.1 months. Tunnel placements of all the cases were measured on 3D CT. Clinical results were collected after reconstruction; graft’s appearance, meniscus status and cartilage state under arthroscopy were compared and analysed too.

Results

Tunnel placements, confirmed with 3D CT, were in the anatomic positions as described in literature both in SB and DB group. No differences were found between SB and DB groups in clinical outcome scores, pivot shift test and KT 1000 measurements (average side-to-side difference for anterior tibial translation was 0.7 mm in SB group and 1.0 mm in DB group). More than 70 % of the single-bundle graft and AM bundle graft in DB group appeared excellent, but only 44.1 % of PL bundle grafts in DB group were excellent and 11.8 % were in poor state. No new menisci tear was found either in SB or DB group, however, in DB group cartilage damages in medial patella-femoral joint occurred in 38.2 % cases. This rate was significantly higher than in the SB group which is only 9.3 %.

Conclusion

Both single- and double-bundle anatomic ACL reconstruction can restore the knee’s stability and functions very well. However, more incidences of poor PL status and medial patellar-femoral cartilage damage may occur in double-bundle ACL reconstruction.

Level of evidence

Randomized controlled trial, Level I.     

Restoration of sagittal and transverse plane proprioception following anatomic double-bundle ACL reconstruction

Purpose

To investigate the restoration of knee proprioception after anatomic double-bundle ACL reconstruction.

Methods

Eleven subjects who underwent anatomic double-bundle ACL reconstruction (12.5–15 months following surgery) and eleven healthy control subjects participated in the study. Sagittal and transverse plane threshold to detect passive motion (TTDPM) were assessed utilizing a customized isokinetic dynamometer by passively rotating the tibia about a fixed femur in both the sagittal plane and transverse plane at 0.25°/s until the subject signalled recognition of movement and movement direction. Based on the normality assumption, either dependent t test or Wilcoxon test was utilized to determine whether significant differences were present between the ACL-reconstructed and the uninjured contralateral limbs. Independent t test or Mann–Whitney test was utilized to compare between the ACL-reconstructed/uninjured contralateral and the external control limbs.

Results

There were no significant differences in TTDPM measurement in eleven out of twelve comparisons between the ACL-reconstructed and the uninjured contralateral/external control limbs. The only statistical significant difference was found on TTDPM towards internal rotation direction from the externally rotated-test position between the ACL-reconstructed and the uninjured contralateral limbs (p = 0.01).

Conclusions

Based on a small sample of eleven subjects, the current results indicate a restoration of both sagittal and transverse plane TTDPM following the anatomic double-bundle ACL reconstruction.

Level of evidence

III.     

The effect of graft tensioning in anatomic 2-bundle ACL reconstruction on knee joint kinematics

Recently, double bundle ACL reconstruction, in which the two bundles thought to have different effects on knee kinematics are reconstructed separately, is widely believed to more favorably restore normal knee kinematics than conventional single bundle ACL reconstruction. However, rotational kinematics during physiological movement after double bundle reconstruction has rarely been tested. The purpose of this study was to measure the kinematics of the ACL deficient and reconstructed knees using two different tensioning conditions in double bundle reconstruction, and to examine the effects of each graft on knee kinematics. Six cadaveric knees were used. Six degrees-of-freedom of knee kinematics and the tension of each graft were monitored during simulated knee extension with the ACL intact, resected, and reconstructed under two different tensioning conditions: 50 N on anteromedial bundle and 0 N on posterolateral bundle (AM-favored condition); 0 N on anteromedial bundle and 50 N on posterolateral bundle (PL-favored condition). Tibial translation: After ACL reconstruction, the tibia overcorrected posteriorly in both conditions. Such an overcorrection in the AM-favored condition was larger than in the PL-favored condition. Tibial rotation: The tibia was significantly externally rotated after ACL reconstruction at a low flexion angle in both conditions. However, at a high flexion angle, tibial external rotation was shown only in the AM-favored condition. Graft tension: While total tensions were similar between the two conditions, the AM bundle shared more tension in the AM-favored condition than in the PL-favored condition. A total of 50 N of tension force was assumed to be excessive for normalizing knee kinematics at a low flexion angle even if double bundle reconstruction was used. Additionally, the AM-favored tensioning reconstruction made the tibia rotate externally and translate posteriorly even at a high flexion angle. Further research is needed to normalize knee kinematics after ACL reconstruction, however it is recommended that a moderate tensioning force is applied to the PL bundle and a minimal tensioning force to the AM bundle in double bundle reconstruction to obtain better knee kinematics.     

Anatomic double-bundle ACL reconstruction restricts knee extension in knees with hyperextension

Purpose

Double-bundle ACL reconstruction has been demonstrated to be at least as effective as single-bundle reconstruction in terms of restoring knee rotational and translational stability. Until now, the influence on knees with hyperextension has not been evaluated. It was the purpose of this study to evaluate whether double-bundle ACL reconstruction restricts extension in hyperextendable knees.

Methods

Hamstring tendon reconstructions of 10 human cadaveric knees with the ability of hyperextension (age: 48 ± 14 years) were performed as single bundle (SB) on one side and double bundle (DB) on the other side. A surgical navigation system (BrainLab, Germany) was used to assess the kinematics of each knee at the intact and reconstructed state. A difference with regard to the anterior-to-posterior translation (AP) and rotational stability at 30° of knee flexion, 90° of flexion and the hyperextension capability of each specimen was analysed.

Results

The difference in AP translation before and after the reconstruction was not significantly different in 30° and 90° of flexion (n.s). Both single- and double-bundle reconstructions restored the preoperative kinematics at 30° and 90° of knee flexion (n.s). The knee extension was 4° ± 1.8° with the intact ACL and 4° ± 1.7° after reconstruction in the SB group (n.s). The knee extension was 5° of hyperextension ± 1.1° with the intact ACL and 0° ± 0.4° after reconstruction in the DB group; the limitation of the extension was significantly larger in this group (p = 0.013).

Conclusion

Both single- and double-bundle ACL reconstruction techniques are capable of restoring knee anteroposterior and rotational stability. Double-bundle reconstructions significantly reduce knee extension in knees with hyperextension capability. Care must be taken when using double-bundle techniques in patients with knee hyperextension as this procedure may limit the knee extension after double-bundle ACL reconstruction.     

Comparison of anatomic ACL reconstruction between selective bundle reconstruction and double-bundle reconstruction

Purpose

The objective of this study was to compare the clinical and radiologic results of preserved ligament remnants in the selective bundle anterior cruciate ligament (ACL) reconstruction and totally sacrificed ligament remnant in the double-bundle ACL reconstruction in order to confirm the evidence of selective bundle reconstruction.

Methods

This retrospective comparative study was conducted for comparison between preserved ligament remnants in the selective bundle ACL reconstruction and totally sacrificed ligament remnant in the double-bundle ACL reconstruction. From 2008 to 2010, 16 patients (group I) underwent selective bundle ACL reconstruction and 30 patients (group II) underwent double-bundle ACL reconstruction. Clinical, stability and radiologic results (tunnel locations of femoral tunnels using 3-D computed tomography and graft signal intensity using magnetic resonance imaging) were compared.

Results

In comparison with functional results, no statistical differences in the Lysholm, Tegner and International Knee Documentation Committee scores were observed between the two groups (n.s.). In comparison with stability results between the two groups, no statistical differences were observed in the Lachman, pivot shift and anterior drawer stress tests using a Telos^® device at 30° and 90° flexed positions (n.s.). In evaluation of the femoral tunnel location, no statistical significant differences in the tunnel position were observed between the groups (n.s.). No statistically significant differences in signal intensity were observed between the two groups (n.s.).

Conclusions

Compared to the double-bundle ACL reconstruction, selective bundle ACL reconstruction produced comparable clinical and radiologic results. Selective bundle ACL reconstruction could be performed instead of double-bundle ACL reconstruction if some intact bundle exists.

Level of evidence

Comparative study, Level III.     

Navigated knee kinematics after cutting of the ACL and its secondary restraint

Purpose  

The purpose of this study is to evaluate the kinematics changes of the knee after cutting of the ACL with or without injury of the anterolateral structures.     

Postoperative evaluation of tibial footprint and tunnels characteristics after anatomic double-bundle anterior cruciate ligament reconstruction with anatomic aimers

Following anatomic double-bundle anterior cruciate ligament (ACL) reconstruction with hamstring tendon autografts, 38 consecutive patients were evaluated with high-speed three-dimensional computed tomography. Scans were performed within 3 days following surgery. The length and width of the reconstructed ACL footprint were measured on axial images. Then, 3D images were converted into 2D with radiologic density for measurement purposes. Tunnel orientation was measured on AP and lateral views. In the sagittal plane, the center of the anteromedial (AMB) and posterolateral bundle (PLB) tibial attachment positions was calculated as the ratio between the geometric insertion sites with respect to the sagittal diameter of the tibia. In addition, the length from the anterior tibial plateau to the retro-eminence ridge was measured; the relationship of this line with the centers of the AM and PL tunnels was then measured. The AP length of the reconstructed footprint was 17.1 mm ± 1.9 mm and the width 7.3 mm ± 1.2 m. The distance from retro-eminence ridge to center of AM tunnel was 18.8 mm ± 2.8 mm, and the distance from RER to center of PL tunnel was 8.7 mm ± 2.6 mm. The distance between tunnels center was 10.1 mm ± 1.7 mm. There were no significant differences between the intra- and inter-observer measurements. The bone bridge thickness was 2.1 mm ± 0.8 mm. In the sagittal plane, the centers of the tunnel apertures were located at 35.7% ± 6.7% and 53.7% ± 6.8% of the tibia diameter for the AMB and PLB, respectively. The surface areas of the tunnel apertures were 46.3 mm² ± 4.4 mm² and 36.3 mm² ± 4.0 mm² for the AM and PL tunnels, respectively. The total surface area occupied by both tunnels was 82.6 mm² ± 7.0 mm². In the coronal plane, tunnel orientation showed the AM tunnel was more vertical than the PL tunnel with a 10° divergence (14.8° vs. 24.1°). In the sagittal plane, both tunnels were almost parallel (29.9° and 25.4° for the AM and PL tunnels, respectively). When using anatomic aimers, the morphometric parameters of the reconstructed tibial footprint in terms of length and distances to the surrounding bony landmarks were similar to the native ACL tibial footprint. However, the native footprint width was not restored, and the surface area of the two tunnel apertures was in the lower range of the published values for the native footprint area.     

Anatomic double-bundle and over-the-top single-bundle with additional extra-articular tenodesis: an in vivo quantitative assessment of knee laxity in two different ACL reconstructions

Purpose  

Combinations of intra- and extra-articular procedures have been proposed for anterior cruciate ligament reconstruction with the aim of achieving an optimal control of translational and rotational knee laxities. Recently, the need for better reproducing the structural and functional behavior of the native anterior cruciate ligament led to the definition of anatomic double-bundle surgical approach. This study aimed to quantitatively verify whether the in vivo static and dynamic behavior obtained using over-the-top single-bundle with extra-articular tenodesis reconstruction was comparable to the results achieved by anatomic double-bundle approach.     

Analysis of tunnel widening after double-bundle ACL reconstruction

Purpose

The purpose of this study was to evaluate the tunnel widening using a multi-planar reformation of MRI (Magnetic Resonance Imaging) in the orientation of the tunnel. The hypotheses of this study were as follows: (1) tunnel widening would be reduced with the above-mentioned technique, (2) the degree of tunnel widening would be different at the site of the tunnels, and (3) the time interval from surgery to MRI acquisition would affect the magnitude of tunnel widening.

Methods

Forty double-bundle ACL reconstructed patients who underwent postoperative MRI were enrolled in this study. The postoperative MRI was performed at 26.7?±?7.4?months in terms of time. The tunnel widening was examined using a multi-planar reformation of MRI in the orientation of the tunnel. Site-specific analysis was performed according to the depth (the entrance, mid, and exit portion) and wall (anterior, posterior, medial, and lateral walls). The correlation between MRI and widening was also evaluated.

Results

The mean tunnel widening of the femoral AM (Anteromedial), femoral PL (Posterolateral), tibial AM, and tibial PL in terms of the most widened diameter was 1.9 (25.4), 2.1 (30.8), 2.5 (32.8), and 3.2?mm (44.5%), respectively. The tibial PL tunnel showed significant widening than the other tunnels. At the entrance, tunnel widening occurred mostly, followed by the order of the mid and exit portion. Correlation analysis of the time interval of MRI acquisition and tunnel widening showed little association.

Conclusions

Tunnel widening after a double-bundle ACL reconstruction using an outside-in technique with press-fitting of the graft was acceptable compared to previously published studies. The tibial PL tunnel showed the most widening among the 4 tunnels examined with the tunnel entrance being most widened area.

Level of evidence

Therapeutic case series, Level IV.