Comparison of isometric and anatomical graft placement in synthetic ACL reconstructions: A pilot study

Evaluating femoral graft placement using three-dimensional magnetic resonance imaging in the reconstruction of the anterior cruciate ligament via independent or transtibial drilling techniques: a retrospective cohort study

PURPOSE

Anterior cruciate ligament (ACL) reconstruction is a common surgical procedure, yet failure still largely occurs due to nonanatomically positioned grafts. The purpose of this study was to retrospectively evaluate patients with torn ACLs before and after reconstruction via 3D MRI and thereby assess the accuracy of graft position on the femoral condyle.

METHODS

Forty-one patients with unilateral ACL tears were recruited. Each patient underwent 3D MRI of both knees before and after surgery. The location of the reconstructed femoral footprint relative to the patient's native footprint was compared.

RESULTS

Native ACL anatomical location of the native ACL had a significant impact on graft position. Native ACLs that were previously more anterior yielded grafts that were more posterior (3.70 ± 1.22 mm, P = 0.00018), and native ACL that were previously more proximal yielded grafts that were more distal (3.25 ± 1.09 mm, P = 0.0042). Surgeons using an independent drilling method positioned 76.2% posteriorly relative to the native location, with a mean 0.1 ± 2.8 mm proximal (P = 0.8362) and 1.8 ± 3.0 mm posterior (P = 0.0165). Surgeons using a transtibial method positioned 75% proximal relative to the native location, with a mean 2.2 ± 3.0 mm proximal (P = 0.0042) and 0.2 ± 2.6 mm posterior (P = 0.8007). These two techniques showed a significant difference in magnitude in the distal-proximal axis (P = 0.0332).

CONCLUSION

The femoral footprint position differed between the native and reconstructed ACLs, suggesting that ACL reconstructions are not accurate. Rather, they are converging to a normative reference point that is neither anatomical nor isometric.

A wear model to predict damage of reconstructed ACL

Impingement with surrounding tissues is a major cause of failure of anterior cruciate ligament reconstruction. However, the complexity of the knee kinematics and anatomical variations make it difficult to predict the occurrence of contact and the extent of the resulting damage. Here we hypothesise that a description of wear between the reconstructed ligament and adjacent structures captures the in vivo damage produced with physiological loadings. To test this, we performed an in vivo study on a sheep model and investigated the role of different sources of damage: overstretching, excessive twist, excessive compression, and wear. Seven sheep underwent cranial cruciate ligament reconstruction using a tendon autograft. Necropsy observations and pull-out force measurements performed postoperatively at three months showed high variability across specimens of the extent and location of graft damage. Using 3D digital models of each stifle based on X-ray imaging and kinematics measurements, we determined the relative displacements between the graft and the surrounding bones and computed a wear index describing the work of friction forces underwent by the graft during a full flexion-extension movement. While tensile strain, angle of twist and impingement volume showed no correlation with pull-out force (ρ = -0.321, p = 0.498), the wear index showed a strong negative correlation (r = -0.902, p = 0.006). Moreover, contour maps showing the distribution of wear on the graft were consistent with the observations of damage during the necropsy. These results demonstrate that wear is a good proxy of graft damage. The proposed wear index could be used in implant design and surgery planning to minimise the risk of implant failure. Its application to sheep can provide a way to increase preclinical testing efficiency.

Relationship Between Number of Lateral Intercondylar Ridges and Area of Denser Bone on the Lateral Intercondylar Wall

Background:

A deeper understanding of the anatomy of the intercondylar notch of the femur may help reduce technical errors during anatomic anterior cruciate ligament (ACL) reconstruction.

Purposes:

To classify the number of ridges on the lateral intercondylar wall, identify factors influencing the number of ridges, and define the relationship between the area of denser bone on the lateral intercondylar wall and the lateral intercondylar ridge.

Study Design:

Descriptive laboratory study.

Methods:

Included were 89 patients with computed tomography (CT) images of the knee joint. On full lateral view of the lateral femoral condyle, the authors evaluated for the presence of a lateral intercondylar ridge. The height and area of the lateral intercondylar wall (notch height and lateral notch area) and the length of Blumensaat line were calculated. Notch outlet length, axial notch area, notch width index, and transepicondylar length were also calculated using 3-dimensional CT. Maximum intensity projection was used to identify the area of denser bone on the femoral lateral intercondylar wall, and the relationship between this area and the lateral intercondylar ridge was investigated.

Results:

The lateral intercondylar ridge exhibited 3 types of morphological variations. The invisible type (no ridge) was observed in 20 knees (22.5%); the ridge type (1 ridge), in 23 knees (25.8%); and the plateau type (2 ridges), in 46 knees (51.7%). There were significant differences in notch height, lateral notch area, Blumensaat line length, and denser bone area among the ridge types (P ≤ .031 for all). The locations of the anterior ridge of the plateau type and of all 23 ridges of the ridge type corresponded to the anterior margin line of the area of denser bone.

Conclusion:

Significant differences were seen in the 3 types of lateral intercondylar ridges. The anterior margin line of the denser bone area on the lateral intercondylar wall was found to correspond to the anterior border of the plateau type and the ridge type.

Clinical Relevance:

The variations in the lateral intercondylar ridge may affect measurement accuracy during evaluation of ACL tunnel position while using the ridge as a landmark. The plateau-type ridge and the area of denser bone on the lateral intercondylar wall may provide a new way for surgeons to determine the femoral tunnel.

Establishment of near and non isometric anterior cruciate ligament reconstruction with artificial ligament in a rabbit model

Background

Tunnel position deicide the isometry of graft attachment in synthetic anterior cruciate ligament (ACL) reconstruction. Near-isometric tunnel position may have advantage in graft integration and knee function in ACL reconstruction (ACLR) with polyethylene terephthalate (PET) ligament. Few studies focused on tunnel position isometry when conduct ACLR with an animal model. This study aimed to establish a preclinical rabbit model of near and non isometric ACLR with PET ligament and investigate the advantage of near-isometric ACLR compared to non-isometric ACLR.

Methods

Nine hind limbs of rabbit were used in tunnel position study. Two femoral(anatomic, nonanatomic) tunnels and three tibial(anterior, middle, posterior) tunnels were used to measure tunnel position isometry during knee full range of motion. The tunnel position combination with minimal isometry was considered as near-isometric tunnel position. Then, 48 rabbits divided into two groups were conducted near or non isometric ACLR with PET ligament with graft fixation angle of 30° and constant tension of 5N. PET ligament isometry, range of motion(ROM) restriction, knee laxity were recorded after operation and followed up with macroscopic observation, microcomputed tomography (micro-CT) analysis, histology assessment and biomechanical test at 4 and 8 weeks postoperatively.

Results

The tunnel combination with minimal isometry was femoral anatomic position and tibial posterior position(5.19 ​± ​1.78%) and considered as near-isometric tunnel position. ROM restriction were observed in non-isometric group (22.50 ​± ​14.14°) while none in near-isometric group. However, no ROM restriction observed at 8 weeks in both group. Knee laxity compared to contralateral knee were better in near-isometric group than non-isometric group (stable/slack/total 10/2/12 VS 3/9/12, p ​= ​0.012) at 8 weeks postoperatively. Supeiror PET ligament integration were also observed in near-isometric group through macroscopic observation, micro-CT analysis, histology assessment at both 4 and 8 weeks. The failure load in the Near-Isometric group at 8 weeks were higher than timezero reconstruction with statistical difference (156.8N ​± ​25.98N vs.102.6 ​± ​22.96N, p ​= ​0.02).

Conclusion

A rabbit model of ACLR based on tunnel position isometry was successfully established in this study. The near-isometric tunnel position in rabbit model was femoral anatomic position and tibial posterior position. A near-isometric ACLR with PET ligament did not cause ROM restriction and had a better graft integration and follow-up stability than non-isometric ACLR with ROM restriction.

The Translational Potential of this Article

The study demonstrate the establishmentof near-isometric tunnel position and non-isometric tunnel position with significant difference of ROM restriction and graft-bone integration. The described tunnel positions with differential isometry in a rabbit ACLR provides a reproducible and translational small animal model and enables preclinical research between tunnel position isometry and its affection on variable grafts, graft integration and knee function.

Medium-Term (Least 5 Years) Comparative Outcomes in Anterior Cruciate Ligament Reconstruction Using 4SHG, Allograft, and LARS Ligament

OBJECTIVE

To compare the clinical efficacy of anterior cruciate ligament (ACL) reconstruction with 4-strand hamstring tendon autograft (4SHG), allograft and the Ligament Advanced Reinforcement System (LARS) ligament, and to find the causes of cumulative failure or nonreturn to sport.

DESIGN

Retrospective case series.

SETTING

Department of Orthopedic Surgery, the second affiliated hospital of Soochow University, Suzhou, Jiangsu, China.

PATIENTS

Three hundred six patients with isolated ACL deficiency were included. Two hundred twenty-nine patients met the inclusion/exclusion criteria, and finally, 185 of these patients participated in this study.

INTERVENTIONS

Anterior cruciate ligament reconstruction using 4SHG, allograft, and LARS.

MAIN OUTCOME MEASURES

Objective knee function, subjective knee function, and information regarding return to sport, cumulative failure, and complications. Secondary: distribution of tunnel position and tunnel enlargement.

RESULTS

There were no statistically significant differences between the 3 groups regarding all the clinical objective and subjective results, return to sport, complications, or cumulative failures (P > 0.05). One hundred twenty-eight patients (69.2%, 128/185) returned to sport. Preoperative (after injury) Tegner scores were inferior to postoperative Tegner scores, and postoperative Tegner scores were inferior to preinjury Tegner scores (P < 0.01). The femoral tunnel malposition was significantly associated with cumulative failure (P < 0.05).

CONCLUSIONS

There were no statistically significant differences among the 4SHG, allograft, and LARS ligament in terms of the clinical outcomes after ACL reconstruction (ACLR) at 5-years follow-up. Interestingly, ACLR could improve the functional and motorial level of the knee, but patients had great difficulty in regaining the level of preinjury movement. In addition, the malposition of the femoral tunnel was an important cause of cumulative failure.

Effect of Nearly Isometric ACL Reconstruction on Graft-Tunnel Motion: A Quantitative Clinical Study

Background:

In anterior cruciate ligament (ACL) reconstruction, minimizing the graft-tunnel motion (GTM) will promote graft-to-bone healing and avoid graft loosening or tearing as well as potential bone tunnel enlargement. A nearly isometric state of the graft can be achieved by placing the tunnel properly to theoretically gain better graft-to-bone healing. However, little clinical evidence is available to quantify the relation between GTM and tunnel position.

Purpose:

To find the proper zones for the femoral and tibial tunnel apertures that minimize the GTM, referred to as the “nearly isometric zone,” through use of intraoperative GTM measurement and 3-dimensional computed tomography (3D-CT).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 100 patients were enrolled in this study. Nearly isometric ACL reconstruction was performed, and an intra-articular GTM measuring device was designed to measure and record the amplitude of GTM while the knee was flexed from 0° to 120°. Postoperatively, the patients underwent multislice CT, and the images were used to create 3D-CT models. After tibial aperture examination, 5 patients were excluded due to the divergence of tibial aperture, and therefore 95 patients remained in the study. Patients were divided into 2 groups according to whether the lateral intercondylar ridge was absent or present. The Bernard-Hertel grid coordinates (h, t) of the femoral tunnel were then quantified.

Results:

The maximal GTM (mGTM) was a mean ± SD of 1.06 ± 0.66 mm (range, 0.0-3.0 mm). The mGTM in patients with a lateral intercondylar ridge was significantly lower than that in patients without a lateral intercondylar ridge (0.81 ± 0.39 vs 1.59 ± 0.73 mm, respectively; P < .0001). The average h and t were 0.227 ± 0.079 and 0.429 ± 0.770, respectively. Notably, in 1 patient, the mGTM was 0 mm whereas the coordinates (h, t) of the femoral tunnel were 0.250 and 0.255. The overall GTM slowly increased before 90° but increased significantly after the knee was bent 105° (P = .010). Correlation analysis showed that the t coordiinate had significant correlation with mGTM (R = 0.581; P < .001). A gradient pattern was created to show the nearly isometric blue zone (mGTM <0.5 mm), which was found to overlap with the IDEAL (isometric, direct insertion, eccentric, anatomic, low tension-flexion pattern) position.

Conclusion:

A method of measuring intraoperative GTM and quantifying femoral tunnel position on postoperative 3D-CT was successfully developed. The presence of a lateral condylar ridge can significantly reduce mGTM. A nearly isometric zone was described that was consistent with the IDEAL concept.