Anatomic single- and double-bundle anterior cruciate ligament reconstruction, part 1: Basic science

Femoral Tunnel Position in Anatomical Double-bundle ACL Reconstruction is not Affected by Blumensaat's Line Morphology

The aim of this study was to reveal the influence of the morphological variations of the Blumensaat's line on anteromedial (AM) and posterolateral (PL) femoral tunnel position in anatomical double-bundle anterior cruciate ligament (ACL) reconstruction.Fifty-three subjects undergoing anatomical double-bundle ACL reconstruction were included (29 female, 24 male; median age 27.4 years; range: 14-50 years). Using an inside-out transportal technique, the PL tunnel position was made on a line drawn vertically from the bottommost point of the lateral condyle at 90 degrees of knee flexion, spanning a distance of 5 to 8 mm, to the edge of the joint cartilage. AM tunnel position was made 2 mm distal to the PL tunnel position. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill (large and small) types. Femoral tunnel position was determined using the quadrant method. A Mann-Whitney U test was performed to compare straight and hill type knees according to AM and PL femoral tunnel position.There were 18 straight and 35 hill type knees (13 small and 22 large hill). AM and PL femoral tunnel position in straight type knees were 21.7 ± 7.0 and 33.6 ± 10.5% in the shallow-deep direction, and 42.1 ± 11.1 and 72.1 ± 8.5% in the high-low direction, respectively. In hill type knees, AM and PL femoral tunnel position were 21.3 ± 5.8 and 36.9 ± 7.1% in the shallow-deep direction, and 44.6 ± 10.7 and 72.1 ± 9.7% in the high-low direction, respectively. No significant difference in AM or PL femoral tunnel position was detected between straight and hill type knees.AM and PL femoral tunnel position in anatomical double-bundle ACL reconstruction was not affected by the morphological variations of the Blumensaat's line. Surgeons do not need to consider Blumensaat's line morphology if AM and PL femoral tunnel position is targeted at the bottommost point of the lateral condyle. This was a level of evidence III study.

Femoral Tunnel Length in Anatomical Double-Bundle Anterior Cruciate Ligament Reconstruction Is Correlated with Body Size and Knee Morphology

The purpose of this study was to reveal the correlation between anteromedial (AM) and posterolateral (PL) femoral tunnel lengths in anatomical double-bundle anterior cruciate ligament (ACL) reconstruction and body size and knee morphology. Thirty-four subjects undergoing anatomical double-bundle ACL reconstruction were included in this study. Preoperative body size (height, body weight, and body mass index) was measured. Using preoperative magnetic resonance imaging (MRI), quadriceps tendon thickness and the whole anterior-posterior length of the knee were measured. Using postoperative computed tomography (CT), axial and sagittal views of the femoral condyle were evaluated. The correlation between measured intraoperative AM and PL femoral tunnel lengths, and body size and knee morphology using preoperative MRI and postoperative CT parameters was statistically analyzed. Both AM and PL femoral tunnel lengths were significantly correlated with height, body weight, posterior condylar length, and Blumensaat's line length. These results suggest that the femoral ACL tunnel length created using a transportal technique can be estimated preoperatively by measuring the subject's body size and/or the knee morphology using MRI or CT. For clinical relevance, surgeons should be careful to create femoral tunnel of sufficient length when using a transportal technique, especially in knees of subjects with smaller body size and knee morphology. Level of evidence is III.

Morphometric Analysis of the Tibial Attachment Shape of the Anterior Cruciate Ligament and Its Relationship With the Location of the Anterior Horn of the Lateral Meniscus

BACKGROUND

The success of anterior cruciate ligament (ACL) reconstruction relies on the accurate replication of the native ACL anatomy, including attachment shapes. The tibial attachment of the ACL exhibits significant shape variations with elliptical, C, and triangular shapes, highlighting the need for objective classification methods and additional information to identify individual anatomic variations.

HYPOTHESIS

The location of the attachment of the anterior horn of the lateral meniscus (AHLM) may determine the shape of the ACL attachment.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

The study used 25 knees from 17 Japanese cadavers for macroscopic anatomic examination and quantitative analysis. The shape of the ACL attachment was quantified using principal component analysis with elliptical Fourier descriptors, whereas the AHLM location was quantified by measuring its mediolateral and anteroposterior positions on the superior surface of the tibia. Reliability was assessed statistically.

RESULTS

The shape of the tibial attachment of the ACL varied among individuals and was classified as elliptical, C-shaped, or triangular. Scatterplots of the principal components of the ACL attachment shape showed overlapping regions of elliptical, C-shaped, and triangular ACL attachments, indicating that a C-shaped attachment is intermediate between elliptical and triangular attachments. The location of the AHLM attachment also varied, with areas in the anterolateral, anteromedial, or posteromedial region. The ACL shape and AHLM location were related, with elliptical, C-shaped, and triangular ACL attachments corresponding to anterolateral, anteromedial, and posteromedial AHLM attachments, respectively.

CONCLUSION

The AHLM attachment location influences the shape of the ACL attachment. Information on the location of the AHLM attachment can aid in predicting the shape of the ACL attachment during ACL reconstruction, potentially improving footprint coverage.

Three-Dimensional Orientation of the Native Anterior Cruciate Ligament in Magnetic Resonance Imaging

The aim of this study was to describe the three-dimensional orientation of the native anterior cruciate ligament (ACL) in magnetic resonance imaging (MRI) by calculating the angles of inclination in relation to the axial plane which is given for the knee joint line in a group of healthy individuals. These could help to establish guidelines that may be used for the surgical positioning of bone tunnels during ACL reconstruction. A total of 290 MRI scans of patients with integrity of the ACL were evaluated; three observers identified the coordinates of the femoral and tibial insertion sites, then it is defined the vector and evaluated its angles with respect to axial axis and calculated the angles with trigonometric equations. The data were analyzed according to the age, sex, side, BMI, and height of the patients, and the interobserver reliability was calculated. The patient demographics were as follows: age average: 45 years old, BMI average: 27.1, 54% right knees, and 60% female. The average angle for all the measurements was 76.95 degrees (SD ± 6.8 degrees) in the sagittal plane, 81.65 degrees (SD ± 7.79 degrees) in the coronal plane and 33.17 degrees (SD ± 4.98 degrees) in the axial plane. No statistically significant differences were found between the categorical variables mentioned; moderate to substantial interobserver reliability strength was found with an average kappa of 0.791 for all measurements. The three-dimensional orientation of the native ACL in a group of healthy individuals was established. The findings can be helpful for performing anatomical reconstructions of the ACL in injured patients using as reference the average calculated angles, or measure of the contralateral non-injured knee for surgical planning; these results serve as a basis for the design of a technique that optimizes the three-dimensional position of the ACL when it undergoes reconstruction in the trend toward greater precision for better functional results. Biomechanical and clinical-surgical studies are required to further evaluate our results.

Size Comparison of the Cadaveric Anterior Cruciate Ligament Midsubstance Cross-Sectional Area and the Cross-Sectional Area of Semitendinosus Double-Bundle Anterior Cruciate Ligament Reconstruction Autografts in Surgery

The purpose of this study was to compare the cadaveric midsubstance cross-sectional anterior cruciate ligament (ACL) area and the cross-sectional semitendinosus (ST) double-bundle ACL autograft area in surgery. Thirty-nine nonpaired formalin-fixed cadaveric knees and 39 subjects undergoing ST double-bundle ACL reconstruction were included in this study. After soft tissue resection, cadaveric knees were flexed at 90 degrees, and the tangential line of the femoral posterior condyles was marked and sliced on the ACL midsubstance. The cross-sectional ACL area was measured using Image J software. In the patients undergoing ACL surgery, the harvested ST was cut and divided into anteromedial (AM) bundle and posterolateral (PL) bundle. Each graft edge diameter was measured by a sizing tube, and the cross-sectional graft area was calculated: (AM diameter/2)2 × 3.14 + (PL diameter/2)2 × 3.14. Statistical analysis was performed for the comparison of the cross-sectional area between the cadaveric ACL midsubstance and the ST double-bundle ACL autografts. The cadaveric midsubstance cross-sectional ACL area was 49.0 ± 16.3 mm2. The cross-sectional ST double-bundle autografts area was 52.8 ± 7.6 mm2. The ST double-bundle autograft area showed no significant difference when compared with the midsubstance cross-sectional ACL area. ST double-bundle autografts were shown to be capable of reproducing the midsubstance cross-sectional ACL area.

The Anterior Cruciate Ligament: Principles of Treatment

The anterior cruciate ligament (ACL) is a crucial connective tissue in the knee joint (tibiofemoral joint). Although the surgical anatomy of this ligament has been studied and interpreted for decades, it remains a topic of discussion among surgeons. The ACL has two bundles, the anteromedial (AM) and the posterolateral (PL) bundle. ACL tears are among the most frequently sustained injuries to the tibiofemoral joint. The ACL is an important rotational stabilizer of the knee joint. The human knee joint can be classified as a complex structure, as it has many ligaments supporting its stability and ensuring required joint mobility. Previously, the outcomes of primary ACL surgery were poor; however, with time, the modalities have improved substantially. There are two methods of performing the reconstruction procedure, the single-bundle method, in which only the AM bundle is reconstructed, and the double-bundle method, in which both the AM and PL bundles of the ACL are reconstructed. Double bundle arthroscopic ACL reconstruction has been recognized as the gold standard procedure. The grafts used for the reconstruction procedure are the tendon of the patella graft and the grafts of the hamstrings. However, one of the drawbacks of performing this surgery is the development of complications, like osteoarthritis. This complication is observed majorly in sports professionals. This article aims to sum up the anatomy of the ACL, its regular tears, the various surgical aspects of managing it, and the advancement of treatment options in the past centuries. Although much has been achieved, detailed scientific studies should be carried out to improve the prognosis and decrease the risk of development of complications.

Biomechanical Comparison of Anterior Cruciate Ligament Reconstruction Using a Single-Bundle Round or Ribbon-like Hamstring Tendon Graft

BACKGROUND

Persistent instability of the knee is reported in up to 30% of patients after anterior cruciate ligament (ACL) reconstruction. Based on anatomic findings showing that ACL is a flat ribbon-like structure that twists during knee flexion, a new surgical ACL reconstruction technique using a ribbon-like graft has been developed. However the effect of this surgical technique on knee kinematics has not yet been evaluated.

PURPOSE

To compare the anteroposterior and rotational stability of the knee after ACL reconstruction using single-bundle (SB) round and ribbon-like grafts in anterolateral-intact/deficient knees.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve human fresh-frozen cadaveric knees were tested with a 6 degrees of freedom robotic system. Internal rotation and anterior translation of the knee were recorded from 0° to 90° of flexion. A full kinematic assessment was performed in each of the following conditions: (1) intact knee, (2) after sectioning of the ACL, (3) after ACL reconstruction using a SB hamstring tendon graft in a round configuration and a ribbon-like configuration, and (4) after sectioning of the anterolateral structures. One-way analysis of variance and post hoc Tukey tests were used for statistical analyses.

RESULTS

When compared with the intact knee, the ACL-deficient knee demonstrated a mean ± SD increase in anterior translation and internal rotation of 6.3 ± 2.5 mm (P < .01) and 5.8°± 2.3° (P < .01), respectively. After ACL reconstruction using a SB ribbon-like graft, the mean difference in anterior translation and internal rotation as compared with the intact knee was -0.1 ± 1.5 mm (P = .842) and 0.0°± 1.1° (P = .999). These differences from the intact knee were also not significant after ACL reconstruction using a round graft (-0.1 ± 1.3 mm, P = .999; -0.5°± 1.5°, P = .401). In the ACL-reconstructed knee using either a ribbon-like or round graft, sectioning of the anterolateral structures did not induce a significant increase of anterior translation and internal rotation of the knee.

CONCLUSION

ACL reconstruction using a SB ribbon-like or round graft restored the kinematics of the intact knee at time zero. Secondary sectioning of the anterolateral structures in the ACL-reconstructed knee using both types of graft did not significantly affect the anterior translation and internal rotation of the knee.

CLINICAL RELEVANCE

This is the first biomechanical study on the new ACL reconstruction technique using a ribbon-like graft.

Transtibial Versus Anteromedial Portal Technique for Femoral Tunnel Drilling in Primary Single-Bundle Anterior Cruciate Ligament Reconstruction: A Meta-analysis of Level 1 and 2 Evidence of Clinical, Revision, and Radiological Outcomes

BACKGROUND

Although numerous clinical studies have compared transtibial (TT) and anteromedial portal (AMP) drilling of femoral tunnels during anterior cruciate ligament reconstruction (ACLR), there is no high-quality, evidence-based consensus regarding which technique affords the best outcome.

HYPOTHESIS

There would be no difference between the TT and AMP techniques in terms of knee stability, patient-reported outcomes, incidence of revision, and radiological results.

STUDY DESIGN

Meta-analysis; Level of evidence, 2.

METHODS

The PubMed and EMBASE databases were searched from inception to February 1, 2021. Level 1 and 2 clinical trials that compared TT and AM techniques were included. Data were meta-analyzed for the outcome measures of knee stability, patient-reported functional outcomes, incidence of revision, and radiological results. Dichotomous variables were presented as odds ratios (ORs), and continuous variables were presented as mean differences (MDs) and standard mean differences (SMDs).

RESULTS

The meta-analysis included 18 clinical studies, level of evidence 1 or 2, that involved 53,888 patients. Pooled data showed that the AMP group had a lower side-to-side difference (SMD, 0.22; 95% CI, 0.06 to 0.39; P = .009), a lower incidence of pivot-shift phenomenon (OR, 3.69; 95% CI, 1.26 to 10.79; P = .02), and a higher postoperative Lysholm score (SMD, -0.26; 95% CI, -0.44 to -0.08; P = .005) than the TT group. However, no statistically significant differences were seen in other outcomes, including subjective International Knee Documentation Committee scores (SMD, -0.11; 95% CI, -0.30 to 0.09; P = .30) or grades (OR, 0.93; 95% CI, 0.35 to 2.49; P = .89), postoperative activity level (MD, -0.14; 95% CI, -0.42 to 0.15; P = .35), and incidence of revision ACLR (OR, 1.04; 95% CI, 0.93 to 1.16; P = .45). The TT technique was more likely to create longer (SMD, 1.05; 95% CI, 0.05 to 2.06; P = .04) and more oblique (SMD, 0.81; 95% CI, 0.51 to 1.11; P < .001) femoral tunnels than the AMP technique, and a higher height ratio of the aperture position was detected with the TT technique (SMD, -3.51; 95% CI, -5.54 to -1.49; P < .001).

CONCLUSION

The AMP technique for ACLR may be more likely to produce better knee stability and improved clinical outcomes than the TT technique, but no difference was found in the incidence of revision between the 2 groups.

Prediction of individual graft for anterior cruciate ligament reconstruction using anthropometric data

INTRODUCTION

Multiple options for individual anterior cruciate ligament (ACL) reconstruction exist; still, there are no guidelines for the preoperative preparation. The aim of this study was to assess the correlation between patients' anthropometric data (height, weight, and age) and measurements of potential tendons (quadriceps-, patella, hamstrings tendon) for an anterior cruciate ligament reconstruction.

MATERIAL AND METHODS

MR images of 102 patients have been analyzed. Measurements of the ACL were performed with respect to its length and angle. The diameter and length as well as width of the quadriceps and patella tendon, the cross-sectional area (CSA) and diameter of the hamstring tendons have been assessed. Patients' height, weight, BMI, sex and age have been recorded. The correlations of these measurements with the patients' anthropometric data have been calculated. Inter-rater and intra-rater reliability based on intra-class correlation (ICC) was evaluated.

RESULTS

The mean lengths of the ACL were 29.8 ± 3.5 mm, tibial insertion sites 15.8 ± 2.5 mm and femoral insertion sites 15.2 ± 3.0 mm. Thickness of the quadriceps tendons was 4.7 ± 1.1 mm and patella tendon 3.2 ± 0.7 mm. The patients' height showed significant positive correlations with the CSA of the hamstring tendon measurements, the length of the ACL, and the insertion sites of the ACL. Patients' weight showed significant positive correlations with patella tendon thickness, the CSA of the hamstring tendons, the length of the ACL, and the tibial and femoral insertion sites. Patients' age showed a significant positive correlation with patella tendon thickness. The ICCs for intra- and inter-rater reliability were 0.98 (95% CI 0.95-0.99, p < 0.001) and 0.94 (95% CI 0.88-0.99, p < 0.001).

CONCLUSION

Anthropometric data with respect to height, weight, and sex can help to predict the dimension of tendons for ACL reconstruction and do correlate with ACL tendon. Patients at risk for small graft dimensions and failure are younger than 20 years and physically active. MRIs of patients at risk for small graft dimensions should be analyzed on tendon length and cross section areas preoperatively to determine the appropriate tendon harvest and fixation technique.

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Is Not Superior to Anatomic Single-Bundle Reconstruction at 10-Year Follow-up: A Randomized Clinical Trial

BACKGROUND

The anatomic double-bundle (DB) technique is purported to be a superior technique due to its mimicking of the double-stranded anatomic formation of the anterior cruciate ligament (ACL). Previous studies with 2-, 5- and 10-year follow-up are conflicted as to whether this technique is superior to the previous gold standard method of ACL reconstruction, the anatomic single-bundle (SB) reconstruction.

PURPOSE/HYPOTHESIS

The aim of this prospective randomized study was to compare the outcomes of the anatomic DB technique and anatomic SB technique with independent drilling at 10 years after anterior cruciate ligament (ACL) reconstruction. We hypothesized that DB ACL reconstruction would result in a better outcome in terms of the pivot-shift test.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 105 patients (33 women, 72 men; median age, 27 years [range, 18-52 years]) were randomized and underwent ACL reconstruction (DB group: n = 53; SB group: n = 52). All reconstruction procedures were performed anatomically by identifying the ACL footprint, using the anteromedial portal for femoral tunnel drilling, and utilizing interference screws for tibial and femoral fixation. One blinded observer examined the patients both preoperatively and at follow-up (median, 120 months [range, 112-134 months]). Multiple subjective and objective clinical evaluations were used to assess the outcomes. Radiographic assessments of osteoarthritis were performed using the Ahlbäck, Kellgren-Lawrence, and Fairbank classification systems early postoperatively and at the final follow-up.

RESULTS

Preoperatively, no differences were found between the study groups. Overall, 70 patients (67%; DB group: n = 39; SB group: n = 31) were available for analysis at 10-year follow-up. No significant difference could be shown between the groups in terms of the pivot-shift grade, knee laxity measurements using the KT-1000 arthrometer, manual Lachman grade, single-leg hop test result, range of motion measurements, Lysholm knee score, Tegner activity score, and Knee injury and Osteoarthritis Outcome Score (KOOS) score. Correspondingly, no differences were found between the groups regarding the presence of radiographic osteoarthritis at follow-up. Both groups improved at follow-up compared with preoperatively in terms of the pivot-shift grade, knee laxity measurements using the KT-1000 arthrometer, manual Lachman grade, Lysholm knee score, and KOOS score (P < .05 [highest P value for any comparison]).

CONCLUSION

The anatomic DB technique was not superior to the anatomic SB technique with independent drilling at 10-year follow-up in regard to objective and subjective measurements. As such, one could argue that there is no need for the continued use of the anatomic DB technique in an unselected population.

The efficacy and medium-term outcomes of ligament advanced reinforcement system compared with auto-grafts in anterior cruciate ligament reconstruction: At least 2 years follow-up

Background: Graft choice is an important step in the pre-operative plan of anterior cruciate ligament reconstruction (ACLR). The four-strand hamstring tendon (4SHT) is the most widely used auto-graft, while the Ligament Advanced Reinforcement System (LARS) is the newest typical biomaterial for ACLR. The physical activity level (PAL) before injury can affect the efficacy and outcomes of ACLR. This study aims to compare the efficacy and functional outcomes between ACLR using LARS and 4SHT in patients different PALs.

Methods: This was a prospective paired case-control study. ACL rupture patients included from 1 January 2017 to 31 December 2019 were subsequently divided into the high and plain PAL groups, according to their baseline PAL before injury. Clinical assessments included: Lachman test, pivot shift test, ligament laxity, Lysholm and International Knee Documentation Committee (IKDC) scores, and rate of returning to sports. The minimum follow-up was 2 years (y).

Results: A total of 58 patients had accomplished the 2 y follow-up (missing rate: 6.5%). In the high PAL group (n = 22), the positive rate of A–P laxity of the LARS subgroup was lower than the 4SHG subgroup (p = 0.138), while the Lysholm score (p = 0.002), IKDC score (p = 0.043), and rate of returning to sports (p = 0.010) of the LARS were higher than the 4SHG at 1 year follow-up; the positive rates of A–P laxity (p = 0.009) and pivot test (p = 0.027) were lower in the LARS than the 4SHG at 2 y follow-up. In the plain PAL group (n = 36), the positive rate of A–P laxity in the LARS subgroup was lower than the 4SHG at 1 year follow-up (p = 0.017); the positive rates of A–P laxity (p = 0.001), Lachman (p = 0.034), and pivot tests (p = 0.034) in the LARS were also lower than the 4SHG at 2 y follow-up, but the IKDC score (p = 0.038) and rate of returning to sports (p = 0.019) in the 4SHG were higher than the LARS.

Conclusion: In patients with high PAL, LARS can acquire better knee stability, sooner functional recovery, and returning to sports than 4SHG, while in patients without high PAL, 4SHG acquires better functional outcomes and a higher rate of returning to sports.

Influences of Partial Anterior Cruciate Ligament Injury On Anterior Cruciate Ligament Tensional Force and Kinematic Stability During Walking

Injuries in the anterior cruciate ligament (ACL), including partial tear and lengthening of the ACL, change the dynamic function of the knee. However, there is a lack of information on the effect of ACL partial tear on knee kinematics during walking. This study aimed to investigate the effects of different levels of ACL injuries on the knee stability and ACL tensional force to identify the critical injury level. Motion data of five normal subjects were acquired along with the ground reaction force. A knee model with 14 ligaments was developed using cadaveric specimen data. The initial length and stiffness of the ACL were changed to develop ACL-injured knee models. Musculoskeletal simulations of the knee models were performed using the measured gait data. The average tibial anterior translation increased significantly by 2.6 ± 0.7 mm when the ACL stiffness decreased to 25% of its original stiffness. The average tibial anterior translation increased significantly by 2.6 ± 0.3 mm at an increase in initial length of 10%. The knee with partial ACL tear had a non-linear decrease in ACL forces owing to the increase in the level of ACL injury, while the knee with ACL lengthening had linear decreased ACL forces. The partial tear of the ACL caused translational instability, while the complete tear caused both rotational and translational instabilities during the musculoskeletal walking simulation. This study presents the effects of partial ACL injuries on joint kinematics and ACL tensional force during the dynamic motion of walking.

Evaluation of anterior cruciate ligament surgical reconstruction through finite element analysis

Anterior cruciate ligament (ACL) tear is one of the most common knee injuries. The ACL reconstruction surgery aims to restore healthy knee function by replacing the injured ligament with a graft. Proper selection of the optimal surgery parameters is a complex task. To this end, we developed an automated modeling framework that accepts subject-specific geometries and produces finite element knee models incorporating different surgical techniques. Initially, we developed a reference model of the intact knee, validated with data provided by the Open Knee(s) project. This helped us evaluate the effectiveness of estimating ligament stiffness directly from MRI. Next, we performed a plethora of “what-if” simulations, comparing responses with the reference model. We found that (a) increasing graft pretension and radius reduces relative knee displacement, (b) the correlation of graft radius and tension should not be neglected, (c) graft fixation angle of 20\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document}∘ can reduce knee laxity, and (d) single-versus double-bundle techniques demonstrate comparable performance in restraining knee translation. In most cases, these findings confirm reported values from comparative clinical studies. The numerical models are made publicly available, allowing for experimental reuse and lowering the barriers for meta-studies. The modeling approach proposed here can complement orthopedic surgeons in their decision-making.

Flat-Tunnel Technique With Independently Tensioned Bundles Better Restores Rotational Stability Than Round-Tunnel Technique in Anatomic Anterior Cruciate Ligament Reconstruction Using Hamstring Graft: A Cadaveric Biomechanical Study

PURPOSE

To investigate the kinematics differences between round-tunnel (ROT) and flat-tunnel (FLT) techniques in anterior cruciate ligament (ACL) reconstruction when using hamstring graft.

METHODS

Nine matched pairs of fresh-frozen cadaveric knees were evaluated for the kinematics of intact, ACL-sectioned, and either ROT or FLT reconstructed knees. The graft bundles for FLT technique were separately tensioned. A 6 degrees of freedom robotic system was used to assess knee laxity: (1) 134-N anterior tibial load at 0°, 15°, 30°, 60°, and 90°of knee flexion; (2) 10 Nm of valgus torque followed by 5 Nm of internal rotation torque simulates a pivot-shift test at 15° and 30°; (3) 5-Nm internal and external rotation torques at 0°, 15°, 30°, 60°, and 90°; (4) 10-Nm varus and valgus torques at 15° and 30°.

RESULTS

Significant differences were found for ROT versus FLT techniques in terms of the simulated pivot-shift test at 15° (2.5 mm vs 1.4 mm, respectively, difference from intact; P =.039) and the internal rotation test at 15° (2.5° vs 0.5°, respectively, difference from intact; P =.034) and 30° (2.0° vs 0.4°, respectively, difference from intact; P =.014). No significant differences were found between groups during 134-N anterior tibial load, external rotation and valgus/varus rotation. Neither technique was able to reproduce the intact state during an anterior tibial load and simulated pivot-shift test.

CONCLUSIONS

The FLT technique with independently tensioned bundles shows the same anterior control as the ROT technique but better restores rotational stability in terms of the simulated pivot-shift test and the internal rotation test in anatomic ACL reconstruction at time zero.

CLINICAL RELEVANCE

The FLT technique with independently tensioned bundles of ACL reconstruction appears to be a viable, more anatomic technique than the ROT technique in mimicking flat anatomy and rotational stability of native ACL.

Tibial Spine Location Influences Tibial Tunnel Placement in Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction

The purpose of this study was to assess the influence of tibial spine location on tibial tunnel placement in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction using three-dimensional computed tomography (3D-CT). A total of 39 patients undergoing anatomical single-bundle ACL reconstruction were included in this study (30 females and 9 males; average age: 29 ± 15.2 years). In anatomical single-bundle ACL reconstruction, the tibial and femoral tunnels were created close to the anteromedial bundle insertion site using a transportal technique. Using postoperative 3D-CT, accurate axial views of the tibia plateau were evaluated. By assuming the medial and anterior borders of the tibia plateau as 0% and the lateral and posterior borders as 100%, the location of the medial and lateral tibial spine, and the center of the tibial tunnel were calculated. Statistical analysis was performed to assess the correlation between tibial spine location and tibial tunnel placement. The medial tibial spine was located at 54.7 ± 4.5% from the anterior border and 41.3 ± 3% from the medial border. The lateral tibial spine was located at 58.7 ± 5.1% from the anterior border and 55.3 ± 2.8% from the medial border. The ACL tibial tunnel was located at 34.8 ± 7.7% from the anterior border and 48.2 ± 3.4% from the medial border. Mediolateral tunnel placement was significantly correlated with medial and lateral tibial spine location. However, for anteroposterior tunnel placement, no significant correlation was found. A significant correlation was observed between mediolateral ACL tibial tunnel placement and medial and lateral tibial spine location. For clinical relevance, tibial ACL tunnel placement might be unintentionally influenced by tibial spine location. Confirmation of the ACL footprint is required to create accurate anatomical tunnels during surgery. This is a Level III; case-control study.

The radiographic tibial spine area is correlated with the occurrence of ACL injury

PURPOSE

The purpose of this study was to reveal the possible influence of the tibial spine area on the occurrence of ACL injury.

METHODS

Thirty-nine subjects undergoing anatomical ACL reconstruction (30 female, 9 male: average age 29 ± 15.2) and 37 subjects with intact ACL (21 female, 16 male: average age 29 ± 12.5) were included in this study. In the anterior-posterior (A-P) and lateral knee radiograph, the tibial spine area was measured using a PACS system. In axial knee MRI exhibiting the longest femoral epicondylar length, the intercondylar notch area was measured. Tibial spine area, tibial spine area/body height, and tibial spine area/notch area were compared between the ACL tear and intact groups.

RESULTS

The A-P tibial spine area of the ACL tear and intact groups was 178 ± 34 and 220.7 ± 58mm², respectively. The lateral tibial spine area of the ACL tear and intact groups was 145.7 ± 36.9 and 178.9 ± 41.7mm², respectively. The tibial spine area was significantly larger in the ACL intact group when compared with the ACL tear group (A-P: p = 0.02, lateral: p = 0.03). This trend was unchanged even when the tibial spine area was normalized by body height (A-P: p = 0.01, lateral: p = 0.02). The tibial spine area/notch area of the ACL tear and intact groups showed no significant difference.

CONCLUSION

The A-P and lateral tibial spine area was significantly smaller in the ACL tear group when compared with the ACL intact group. Although the sample size was limited, a small tibial spine might be a cause of knee instability, which may result in ACL injury.

LEVEL OF EVIDENCE

Level III.

Systematic Review of Surgical Technique and Tunnel Target Points and Placement in Anatomical Single-Bundle ACL Reconstruction

The purpose of this systematic review was to reveal the trend in surgical technique and tunnel targets points and placement in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, data collection was performed. PubMed, EMBASE, and Cochran Review were searched using the terms "anterior cruciate ligament reconstruction," "anatomic or anatomical," and "single bundle." Studies were included when they reported clinical results, surgical technique, and/or tunnel placement evaluation. Laboratory studies, technical reports, case reports, and reviews were excluded from this study. From these full article reviews, graft selection, method of creating the femoral tunnel, and femoral and tibial tunnel target points and placement were evaluated. In the 79 studies included for data evaluation, the selected grafts were: bone patella tendon bone autograft (12%), and hamstring autograft (83%). The reported methods of creating the femoral tunnel were: transportal technique (54%), outside-in technique (15%), and transtibial technique (19%). In the 60 studies reporting tunnel target points, the target point was the center of the femoral footprint (60%), and the center of the anteromedial bundle footprint (22%). In the 23 studies evaluating tunnel placement, the femoral tunnel was placed in a shallow-deep direction (32.3%) and in a high-low direction (30.2%), and the tibial tunnel was placed from the anterior margin of the tibia (38.1%). The results of this systematic review revealed a trend in anatomical single-bundle ACL reconstruction favoring a hamstring tendon with a transportal technique, and a tunnel target point mainly at the center of the ACL footprint. The level of evidence stated is Systematic review of level-III studies.

The risk of graft impingement still exists in modern ACL surgery and correlates with degenerative MRI signal changes

PURPOSE

Anatomic tunnel placement in ACL reconstruction is crucial to restore knee function. The aims of this study were to (i) evaluate the accuracy of tunnel placement for primary state-of-the-art ACL reconstruction, and (ii) examine the correlation between incorrect tunnel placement, graft appearance, and notch impingement.

METHODS

In this retrospective study, all patients underwent primary single-bundle ACL reconstruction with independent drilling of the femoral and tibial tunnels according to anatomical landmarks. The accuracy of tunnel placement and the rate of notch impingement were analysed with MRI. The study cohort was subdivided according to the morphology of the graft: intact, degeneration, and re-rupture. The objective outcome was evaluated with the IKDC objective score, and the subjective outcomes were evaluated with the IKDC subjective score, the Lysholm knee score, the KOOS, and the Tegner activity scale score.

RESULTS

Eighty-seven consecutive patients with a mean follow-up of 3.8 ± 1.4 years were evaluated. There was no significant difference among the groups concerning the baseline characteristics. The re-rupture rate was 9.2%. The position of the femoral tunnel was correct in 92% of the patients, and the position of the tibial tunnel was correct in 93% of the patients. In the intact group, impingement was not found in any of the cases, whereas the rate of impingement in the degeneration (65%) and re-rupture (80%) groups was significantly higher than that in the intact group (p < 0.001). The risk of impingement was more likely with femoral (71% vs. 13%, p < 0.001) or tibial (100% vs. 11%, p < 0.001) malpositioning. The objective IKDC score was A in 52 patients (60%), B in 26 patients (30%), and C in 9 patients (10%). The average subjective IKDC score, Lysholm score, and KOOS were comparable in the intact and degeneration groups but significantly lower in the patient group with newly diagnosed re-ruptures (p = 0.05). The Tegner activity scale score was comparable in all three groups.

CONCLUSION

Even though the accuracy of femoral tunnel placement in modern single-bundle ACL reconstruction is greater, the risk of malpositioning and graft impingement remains. In our patient cohort, there was a clear correlation between ACL graft impingement, degenerative changes in MRI, and incorrect tunnel positioning. The surgeon must focus on accurate tunnel placement specific to individual patient anatomy.

LEVEL OF EVIDENCE

Level III.

All-Inside Anterior Cruciate Ligament Reconstruction Using an Anterior Half of the Peroneus Longus Tendon Autograft

Background:

The peroneus longus tendon (PLT) has been used as a graft in many orthopaedic surgical procedures because of its comparable biomechanical strength with the native anterior cruciate ligament (ACL). Despite its potential, few studies have been performed to investigate the clinical reliability of ACL reconstruction using a PLT autograft.

Purpose:

To assess the clinical outcomes and donor-site morbidity of ACL reconstruction using an anterior half of the PLT (AHPLT) autograft in patients with an isolated ACL injury.

Study Design:

Case series; Level of evidence, 4.

Methods:

Between January 2016 and January 2017, a total of 21 patients with an isolated ACL injury underwent all-inside single-bundle ACL reconstruction using an AHPLT autograft. Knee stability was assessed using the Lachman test, pivot-shift test, and KT-2000 arthrometer (side-to-side difference) with 134-N anterior force and at 30° of knee flexion. Knee function was evaluated using the International Knee Documentation Committee score, Lysholm score, and Tegner score. Donor-site morbidity was assessed using ankle eversion and plantarflexion strength as well as the American Orthopaedic Foot & Ankle Society scoring system and the Foot and Ankle Disability Index.

Results:

At a mean final follow-up of 40.1 months (range, 36-48 months), the KT-2000 arthrometer side-to-side difference was significantly lower compared with preoperatively (1.1 ± 0.62 vs 7.0 ± 2.18 mm, respectively; P < .001). The mean preoperative International Knee Documentation Committee, Lysholm, and Tegner scores were 52.0 ± 8.27, 50.9 ± 8.50, and 1.8 ± 0.87, respectively, increasing significantly to 94.2 ± 2.61, 95.2 ± 2.64, and 6.8 ± 1.50, respectively, at final follow-up (P < .001 for all). All patients had grade 5 muscle strength in ankle eversion and plantarflexion at the donor site, with mean American Orthopaedic Foot & Ankle Society and Foot and Ankle Disability Index scores of 96.8 and 97.6, respectively. No complications or reoperations occurred.

Conclusion:

All-inside ACL reconstruction using an AHPLT autograft produced good functional scores and stability without obvious ankle-site morbidity.

Pain Following Single-bundle versus Double-bundle Anterior Cruciate Ligament Reconstruction: A Systematic Review

BACKGROUND: Double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) has been known to result in better functional outcomes, joint stability, and lower revision rates compared to single-bundle (SB) ACLR. However, given the increased invasiveness and damage to the surrounding tissue area, it is proposed that it may be associated with increased pain. AIM: This review aims to gather all studies and literature that reported pain as an outcome when comparing SB versus DB ACLR. METHODS: Literature searching was conducted across seven search engines for studies reporting pain as an outcome and comparing SB versus DB ACLR. RESULTS: Eight studies met the eligibility criteria and were included in the study. Overall, the studies show variable findings regarding pain in DB compared to SB ACLR, with the only statistically significant results from two studies indicating that DB ACLR is associated with more pain than SB ACLR. CONCLUSION: Based on the limited evidence available, no conclusions can be made regarding the pain experienced between people receiving either procedure. This constitutes a need for additional studies with increased follow-up time periods, larger sample size, and better study design.

Biomechanical Difference between Conventional Transtibial Single-Bundle and Anatomical Transportal Double-Bundle Anterior Cruciate Ligament Reconstruction Using Three-Dimensional Finite Element Model Analysis

The purpose of our study was to analyze the graft contact stress at the tunnel after transtibial single-bundle (SB) and transportal double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. After transtibial SB (20 cases) and transportal DB (29 cases) ACL reconstruction, the three-dimensional image of each patient made by postoperative computed tomography was adjusted to the validation model of a normal knee and simulated SB and DB ACL reconstructions were created based on the average tunnel position and direction of each group. We also measured graft and contact stresses at the tunnel after a 134 N anterior load from 0° to 90° flexion. The graft and contact stresses became the greatest at 30° and 0° flexion, respectively. The total graft and contact stresses after DB ACL reconstruction were greater than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the graft and contact stresses of each graft after DB ACL reconstruction were less than those after SB ACL reconstruction. In conclusion, the total graft and total contact stresses after DB ACL reconstruction are higher than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the stresses of each graft after DB ACL reconstruction are about half of those after SB ACL reconstruction.

The long-term outcomes of different grafts in anterior cruciate ligament reconstruction: a network meta-analysis

OBJECTIVES

To compare the long-term prognosis of patients with different types of grafts used in anterior cruciate ligament reconstruction (ACLR).

METHODS

PubMed, Ovid (MEDLINE and Embase) and the Cochrane library were searched up to Feb 2020. Eligible studies about different grafts in ACLR were searched for identifying the evidence comparing the long-term (mean or median follow-up time or the general description of the follow-up time≥2 years) knee outcomes of different grafts for ACLR. The final included articles and evaluation criteria were confirmed by the authors and senior clinicians to ensure the validity of the included articles. Lysholm score, the results of pivot shift test, Lachman test and International Knee Documentation Committee (IKDC) evaluation were selected as prognostic indicators. A Bayesian network meta-analysis was conducted.

RESULTS

A total of 30 articles were included in our network meta-analysis. Finally, we found that artificial graft or augmentation can provide the not bad Lysholm score but the worse result of IKDC evaluation for patients with ACLR compared with other types of grafts. Double-bundle hamstring autograft can provide a good Lysholm score as well as lower positive rate of pivot shift test and Lachman test. Patellar tendon autograft can provide the better result of IKDC evaluation. The patients with allogeneic tendon graft may get the higher positive rate of pivot shift test and Lachman test. Patients with single-bundle hamstring autograft may get the ordinary result of IKDC evaluation and Lysholm score.

CONCLUSIONS

Double-bundle hamstring autograft may be a better choice because of more items of good prognosis for the patients with ACLR. Patellar tendon autograft is a right choice which only shows the disadvantage on the Lysholm score. The prognosis of patients with single-bundle hamstring autograft is ordinary. The effect of artificial graft or augmentation needs more evidence to prove. Allogeneic tendon graft is not a better choice when compared with other grafts referred in our network meta-analysis.

TRANSLATIONAL POTENTIAL STATEMENT

In this study, we made a comprehensive comparison of the grafts commonly used in anterior cruciate ligament reconstruction. The evidence presented in this study provides a reference for clinicians to select a suitable anterior cruciate ligament graft.

Enlarged tibial eminence may be a protective factor of anterior cruciate ligament

Anterior cruciate ligament (ACL) is a primary stabilizer of the knee and constrains joint motion, and its injury is very common in clinic. There are many studies on the risk factors of ACL injury such as the ACL diameter, intercondylar notch width index (NWI), sagittal condylar shape, tibial posterior slope, tibia eminence size and so on. Large amount of research data has confirmed that all above are closely related to ACL injury. Among them the morphological characteristics of femoral condyle and tibial plateau are closely related to ACL injury. For example the tibial eminence, which is the hot topic of recent research. Whether or how does it relate to ACL injury has draw much interest of researchers. Since the tibial eminence and the ACL are both located in the intercondylar notch and adjacent to each other, we hypothesize the size of the tibial eminence may relate to the rupture of ACL. For there is report have found that reduced medial tibial eminence was associated with ACL injury, we suggest a hypothesis that enlarged tibia eminence may be a protective factor of ACL.

The occurrence of ACL injury influenced by the variance in width between the tibial spine and the femoral intercondylar notch

PURPOSE

The purpose of this study was to reveal the influence of the variance in width between the tibial spine and the femoral intercondylar notch on the occurrence of ACL injury.

METHODS

Thirty-nine subjects undergoing anatomical ACL reconstruction (30 female, 9 male; average age 29 ± 15.2) and 37 subjects with intact ACL (21 female, 16 male; average age 29 ± 12.5) were included in this study. In the anterior-posterior knee radiograph, tibial spine height, and the length between the top of the medial and lateral tibial spine (tibial spine width) were measured. In axial knee MRI exhibiting the longest femoral epicondylar length, intercondylar notch outlet length was measured and notch width index was calculated. Tibial spine width/notch outlet length, and tibial spine width/notch width index were compared between the ACL tear and intact groups.

RESULTS

Tibial spine width/notch outlet length of the ACL tear and intact groups was 0.6 ± 0.1 and 0.7 ± 0.1, respectively. Tibial spine width/notch width index of the ACL tear and intact groups was 0.4 ± 0.1, and 0.6 ± 0.1, respectively. Both parameters were significantly larger in the ACL intact group.

CONCLUSION

Both tibial spine width/notch outlet length and tibial spine width/notch width index were significantly smaller in the ACL tear group when compared with the ACL intact group. The occurrence of ACL injury influenced by the variance in width between the tibial spine and the femoral intercondylar notch.

LEVEL OF EVIDENCE

III.

Techniques for In Vivo Measurement of Ligament and Tendon Strain: A Review

The critical clinical and scientific insights achieved through knowledge of in vivo musculoskeletal soft tissue strains has motivated the development of relevant measurement techniques. This review provides a comprehensive summary of the key findings, limitations, and clinical impacts of these techniques to quantify musculoskeletal soft tissue strains during dynamic movements. Current technologies generally leverage three techniques to quantify in vivo strain patterns, including implantable strain sensors, virtual fibre elongation, and ultrasound. (1) Implantable strain sensors enable direct measurements of tissue strains with high accuracy and minimal artefact, but are highly invasive and current designs are not clinically viable. (2) The virtual fibre elongation method tracks the relative displacement of tissue attachments to measure strains in both deep and superficial tissues. However, the associated imaging techniques often require exposure to radiation, limit the activities that can be performed, and only quantify bone-to-bone tissue strains. (3) Ultrasound methods enable safe and non-invasive imaging of soft tissue deformation. However, ultrasound can only image superficial tissues, and measurements are confounded by out-of-plane tissue motion. Finally, all in vivo strain measurement methods are limited in their ability to establish the slack length of musculoskeletal soft tissue structures. Despite the many challenges and limitations of these measurement techniques, knowledge of in vivo soft tissue strain has led to improved clinical treatments for many musculoskeletal pathologies including anterior cruciate ligament reconstruction, Achilles tendon repair, and total knee replacement. This review provides a comprehensive understanding of these measurement techniques and identifies the key features of in vivo strain measurement that can facilitate innovative personalized sports medicine treatment.

A Review on Finite Element Modeling and Simulation of the Anterior Cruciate Ligament Reconstruction

The anterior cruciate ligament (ACL) constitutes one of the most important stabilizing tissues of the knee joint whose rapture is very prevalent. ACL reconstruction (ACLR) from a graft is a surgery which yields the best outcome. Taking into account the complicated nature of this operation and the high cost of experiments, finite element (FE) simulations can become a valuable tool for evaluating the surgery in a pre-clinical setting. The present study summarizes, for the first time, the current advancement in ACLR in both clinical and computational level. It also emphasizes on the material modeling and properties of the most popular grafts as well as modeling of different surgery techniques. It can be concluded that more effort is needed to be put toward more realistic simulation of the surgery, including also the use of two bundles for graft representation, graft pretension and artificial grafts. Furthermore, muscles and synovial fluid need to be included, while patellofemoral joint is an important bone that is rarely used. More realistic models are also required for soft tissues, as most articles used isotropic linear elastic models and springs. In summary, accurate and realistic FE analysis in conjunction with multidisciplinary collaboration could contribute to ACLR improvement provided that several important aspects are carefully considered.

The location of the femoral ACL footprint center is different depending on the Blumensaat's line morphology

PURPOSE

The purpose of this study was to evaluate the difference in the center point of the femoral ACL footprint according to the morphological variations of the Blumensaat's line.

METHODS

Fifty-nine non-paired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. Digital images were evaluated using the Image J software. The periphery of the femoral ACL footprint was outlined and the center point was measured automatically. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). The center of the femoral ACL footprint and hilltop placement were evaluated using the quadrant method. A quadrant grid was placed uniformly, irregardless of hill existence, and not including the articular cartilage. A correlation analysis was performed between the center point of the femoral ACL footprint and hilltop placement.

RESULTS

The straight type consisted of 19 knees, and the hill type 40 knees (small hill type 13 knees and large hill type 27 knees). The center of the femoral ACL footprint (shallow-deep/high-low) in the straight and hill type knees was 33.7/47.6%, and 37.2/50.3%, respectively. In the hill type, the ACL footprint center was significantly more shallow when compared to the straight type. Significant correlation was observed between the center point of the femoral ACL footprint and hilltop placement of the Blumensaat's line.

CONCLUSION

The center point of the femoral ACL footprint was significantly more shallow in the hill type knees when compared to the straight type. For clinical relevance, considering that the location of the femoral ACL footprint center is different depending on the Blumensaat's line morphology, to perform accurate ACL reconstruction, femoral ACL tunnel placement should be made based on Blumensaat's line morphological variations.

Functional double-bundle anterior cruciate ligament reconstruction using hamstring tendon autografts with preserved insertions is an effective treatment for tibiofemoral instability

PURPOSE

The aim of this study was to introduce a modified anatomical anterior cruciate ligament reconstruction using functional double bundles (F-DBACLR), which achieved sequential tensioning at all flexion angles postoperatively, and compare its clinical outcomes with the anatomical single-bundle technique (A-SBACLR).

METHODS

A total of 156 patients with an ACL injury underwent ACLR (A-SB group, n = 78; F-DB group, n = 78). All operations were performed by anatomically identifying the ACL footprints and fixing the graft at a pre-determined degree of knee flexion. Two observers blinded to the patient identities examined the patients preoperatively and during follow-up (median 28.2 months; range 26-31 months). Multiple subjective and objective clinical evaluation tests and assessment of clinical outcomes concerning the translational and rotational stability of the knee including the International Knee Documentation Committee (IKDC) questionnaire, Lysholm Knee Scoring Scale, Knee Injury and Osteoarthritis Outcome Score (KOOS), Tegner Activity Scale, KT-1000 laxity measurements, Lachman test and pivot-shift test were performed preoperatively and postoperatively.

RESULTS

Preoperatively, no differences were found between the two groups. During the 2-year observation period, patients in the F-DB group revealed better clinical outcomes in terms of the Tegner Activity Scale Score, IKDC, KOOS and Lysholm Knee Scoring Scale. Similar results were shown in regard to the translational stability in both groups, while the F-DB group had more rotational stability at 2 years of follow-up.

CONCLUSIONS

The clinical outcomes indicated that F-DBACLR is clinically practicable and advantageous in the treatment of the ACL-deficient knee.

LEVEL OF EVIDENCE

II.

The Blumensaat's line morphology influences to the femoral tunnel position in anatomical ACL reconstruction

PURPOSE

The purpose of this study was to reveal the influence of the morphological variations of the Blumensaat's line on femoral tunnel position in anatomical anterior cruciate ligament (ACL) reconstruction.

METHODS

Thirty-eight subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (22 female, 16 male: median age 45: 15-63). Using a trans-portal technique, the femoral tunnel was targeted to reproduce the center of antero-medial bundle. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). Femoral ACL tunnel position was evaluated using the quadrant method. When the quadrant method grid was applied, the baseline of the grid was matched to the anterior part of the Blumensaat's line, without considering the existence of a hill. Using pre-operative 3D-CT data, the axial and sagittal morphology of the knee was also compared, establlishing straight and hill types.

RESULTS

There were 12 straight type knees and 26 hill type knees (7 small hill type knees and 19 large hill type knees). The femoral tunnel position in straight type knees was 23.6 ± 3.7% in the shallow-deep direction, and 41.3 ± 8.2% in the high-low direction. In hill type knees, the tunnel position was 27 ± 4.7% in the shallow-deep direction, and 51 ± 10.1% in the high-low direction. The femoral tunnel was placed significantly more shallow and lower in hill type knees when compared with straight type knees.

CONCLUSION

Femoral ACL tunnel placement was significantly influenced by the morphological variations of the Blumensaat's line. As detecting morphological variation in arthroscopic surgery is difficult, surgeons should confirm such variations pre-operatively using radiograph or CT so as to avoid making extremely shallow and low tunnels in hill type knees.

LEVEL OF EVIDENCE

Case-controlled study, III.

Correlation between the mid-substance cross-sectional anterior cruciate ligament size and the knee osseous morphology

INTRODUCTION

One of the final goals of anatomical anterior cruciate ligament (ACL) reconstruction is the restoration of native anatomy. It is essential to obtain more accurate predictors of mid-substance ACL size before surgery. However, to the best of our knowledge, no study has reported correlation between the mid-substance cross-sectional ACL size and the knee osseous morphology. The purpose of this study was to reveal correlation between the mid-substance cross-sectional ACL size and the knee osseous morphology.

MATERIALS AND METHODS

We used 39 non-paired formalin fixed Japanese cadaveric knees. All surrounding muscles, ligaments and soft tissues in the knee were resected. After soft tissue resection, the knee was flexed at 90°, and a tangential plane of the femoral posterior condyles was marked and cut the ACL. Femoral ACL footprint size, Blumensaat's line length, lateral wall of the femoral intercondylar notch size, lateral wall of the femoral intercondylar notch height, tibial ACL footprint size, tibia plateau size, the whole anterior-posterior (AP) length, the medial and the lateral AP length of the tibia plateau, and the medial-lateral (ML) length of the tibia plateau were measured. The Pearson's product movement correlation was calculated to reveal correlation between the mid-substance cross-sectional ACL size and the measured parameters of the knee osseous morphology.

RESULTS

The measured mid-substance cross-sectional ACL size was 49.9 ± 16.3 mm². The tibial ACL footprint size, the tibia plateau size, the whole AP length of the tibia plateau, the lateral AP length of the tibia plateau and the ML length of the tibia plateau were significantly correlated with the mid-substance cross-sectional ACL size.

CONCLUSIONS

For clinical relevance, some tibial sides of the knee osseous morphology were significantly correlated with the mid-substance cross-sectional ACL size. It might be possible to predict the mid-substance ACL size measuring these parameters.

Side Variations of Anterior Cruciate Ligament Coronal Angles: Implications for ACL Reconstruction

Current literature has shown a biomechanical advantage of recreating the native coronal obliquity of the anterior cruciate ligament (ACL) during grating procedures; however, the majority of studies on ACL morphological variation have been performed unilaterally. This cadaveric study aimed to evaluate sided ACL coronal angle of inclination variation including trend analysis with sex, age, height, and femoral condyle width. The ACLs of 57 embalmed cadaveric specimens were evaluated bilaterally for a total of 114 ACLs. The knees were flexed to 110°. A 0.70-mm wire measured coronal angulation through the lateral tibial plateau and the medial ACL border. An image taken of the wire allowed digital measurement with the ImageJ software. IBM SPSS was utilized for statistical analysis. Bilateral measurements demonstrated a difference in an individual's sided ACL angulation (P < 0.001). Right-sided angulation was greater in 61.4% (35/57). In cadavers with greater right-side angulation, right ACLs averaged 66.2° versus left ACLs averaged 60.9° (P < 0.001). Cadavers with greater left-sided ACL angles demonstrated average left ACLs measuring 65.5° versus right ACLs measuring 60.6° (P < 0.001). Right-sided angles were greater in 69.7% of females. Understanding the anatomy of the ACL's native coronal angle and variations between a patient's knees is imperative during reconstruction surgery to aid in anatomic tunnel placement for improved knee motion and rotational knee kinematics following surgery. A statistically significant difference exists between an individual's right and left ACL coronal angles of inclination. Clin. Anat. 32:1102-1106, 2019. © 2019 Wiley Periodicals, Inc.

Comparison of Modified Transtibial and Anteromedial Portal Techniques in Anatomic Single-Bundle ACL Reconstruction

The purpose of this study was to compare the clinical, 3-dimensional computed tomography, magnetic resonance imaging, and second-look arthroscopic findings of the modified transtibial technique with those of the anteromedial portal technique in single-bundle anterior cruciate ligament reconstruction (SB-ACLR). Among patients who underwent SB-ACLR from February 2012 to May 2014, 95 patients with a minimum of 36 months of follow-up were included in this retrospective study. Forty-five patients underwent a reconstruction using the modified transtibial technique. Fifty patients underwent a reconstruction using the anteromedial portal technique. Clinical scores and stabilities were recorded preoperatively and at final follow-up. All patients had postoperative computed tomography and the computed tomography parameters, including tunnel position and graft obliquity, evaluated. Additionally, postoperative magnetic resonance imaging and second-look arthroscopy were performed. On the basis of the functional and stability outcomes, all of the patients showed significant improvement after SB-ACLR, with no significant differences existing between the 2 groups (P>.05). Tunnel position and obliquity were not significantly different between the 2 groups (P>.05). There were no statistically significant differences between the 2 groups regarding the magnetic resonance imaging and second-look arthroscopy findings (P>.05). The tunnel characteristics and clinical results of the 2 techniques were comparable. Given the several advantages of the modified transtibial technique, including its simplicity and patients' greater activity level, it is suitable for anatomic SB-ACLR. [Orthopedics. 2019; 42(2):83-89.].

The correlation between the femoral anterior cruciate ligament footprint area and the morphology of the distal femur: three-dimensional CT evaluation in cadaveric knees

BACKGROUNDS

"Anatomical" anterior cruciate ligament (ACL) reconstruction is defined as the functional restoration of the ACL to its native dimensions. It is essential to obtain more accurate predictors of ACL size before surgery. The purpose of this study was to investigate the correlation between the native femoral ACL footprint size and the morphology of the distal femur using three-dimensional CT (3D-CT).

METHODS

Thirty non-paired Japanese human cadaver knees were used. All soft tissues around the knee were resected except the ACL. For the evaluation of femoral condyle morphology, trans-epicondylar length (TEL), notch outlet length, axial notch area, and notch width index were measured using 3D-CT. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. The ACL was carefully dissected, and the boundaries of the ACL insertion site were outlined on the femoral side. An accurate lateral view of the femoral condyle was photographed with a digital camera. The size of the femoral ACL footprint, length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were measured with ImageJ software.

RESULTS

Notch height, lateral notch area, and TEL were significantly correlated with the femoral ACL footprint area. Both axial notch area and notch outlet length were significantly correlated with the femoral mid-substance insertion area.

CONCLUSION

Morphological evaluation using 3D-CT preoperatively may be useful in predicting the femoral ACL footprint size.

Measurement of the Whole and Midsubstance Femoral Insertion of the Anterior Cruciate Ligament: The Comparison with the Elliptically Calculated Femoral Anterior Cruciate Ligament Footprint Area

PURPOSE

The purpose of this study was to measure the detailed morphology of the femoral anterior cruciate ligament (ACL) footprint. The correlation and the comparison between the measured area and the area which mathematically calculated as elliptical were also evaluated.

MATERIALS AND METHODS

Thirty nine nonpaired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on both the whole footprint and the midsubstance insertion. Lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The area, length, and width of the femoral ACL footprint were measured with Image J software (National Institution of Health). Using the length and width of the femoral ACL footprint, the elliptical area was calculated as 0.25 π (length × width). Statistical analysis was performed to reveal the correlation and the comparison of the measured and elliptically calculated area.

RESULTS

The sizes of the whole and midsubstance femoral ACL footprints were 127.6 ± 41.7 mm² and 61 ± 20.2 mm², respectively. The sizes of the elliptically calculated whole and midsubstance femoral ACL footprints were 113.9 ± 4.5 mm² and 58.4 ± 3 mm², respectively. Significant difference was observed between the measured and the elliptically calculated area. In the midsubstance insertion, significant correlation was observed between the measured and the elliptically calculated area (Pearson's correlation coefficient = 0.603, P = 0.001). However, no correlation was observed in the whole ACL insertion area.

CONCLUSION

The morphology of the femoral ACL insertion resembles an elliptical shape. However, due to the wide variation in morphology, the femoral ACL insertion cannot be considered mathematically elliptical.

Femoral tunnel length in anatomical single-bundle ACL reconstruction is correlated with height, weight, and knee bony morphology

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction and body size and/or knee morphology.

METHODS

Thirty-one subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (20 female, 11 male; median age 46, 15-63). Pre-operative height, body weight, and body mass index (BMI) were measured. In pre-operative magnetic resonance imaging, the thickness of the quadriceps tendon and the whole anterior-posterior (AP) length of the knee were measured using the sagittal slice. Using post-operative three-dimensional computed tomography, accurate axial and lateral views of the femoral condyle were evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the height, weight, BMI, quadriceps tendon thickness, AP length of the knee, trans-epicondylar length, the notch area (axial), length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were statistically analyzed. Tunnel placement was also evaluated using a Quadrant method.

RESULTS

The average femoral tunnel length was 35.6 ± 4.4 mm. The average height, body weight, and BMI were 162.7 ± 7.2 cm, 61.9 ± 10 kg, and 23.4 ± 3.5, respectively. Femoral tunnel length was significantly correlated with height, body weight and the height and area of lateral wall of the femoral intercondylar notch, and the length of the Blumensaat's line.

CONCLUSION

For clinical relevance, the risk of creating a femoral tunnel of insufficient length in anatomical single-bundle ACL reconstruction exists in subjects with small body size. Surgeons should pay careful attention to prevent this from occurring.

LEVEL OF EVIDENCE

Case-controlled study, Level III.

Evaluation of age-related differences in anterior cruciate ligament size

PURPOSE

The purpose of this study was to reveal the relation between age and the morphological characteristics of the anterior cruciate ligament (ACL) using magnetic resonance imaging (MRI).

METHODS

Thirty-seven young subjects who were diagnosed with a meniscus injury without ACL tear using MRI (15 male and 22 female, median age 26, range 15-49), and 33 elderly subjects for whom knee MRI was performed before uni-compartmental knee arthroplasty (11 male and 22 female, median age 77, range 60-83), were included in this study. In the elderly group, healthy ACL gross morphology was confirmed macroscopically during surgery. In all knees, ACL was detected without any intensity alteration. In the MRI evaluation, using the axial slice revealing the greatest length between the medial and lateral epicondyle of the femur, axial ACL size was evaluated. Using the coronal plane image, the sagittal image was sliced parallel with the native ACL. In the sagittal image of the MRI, the largest area of the ACL was measured. Statistical analysis was performed to reveal the correlation between age and ACL size. Both axial and sagittal ACL areas were compared between the young and elderly groups.

RESULTS

Age and sagittal ACL area were significantly correlated (Pearson's coefficient correlation: - 0.353, P = 0.003). The sagittal ACL area was significantly larger in the young group when compared with the elderly group (P = 0.001). However, when the sagittal ACL area was normalized by the length of Blumensaat's line, no significant difference was observed.

CONCLUSION

For clinical relevance, sagittal ACL size was significantly larger in young subjects. The reason for this difference is likely the difference in knee size. When performing anatomical studies of the ACL using cadaveric knees of elderly specimens, there is the possibility that the ACL size will be underestimated. Considering that the ACL surgery is mainly performed for young subjects, cadavers of younger age should be used in such studies.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

High complication rate following dynamic intraligamentary stabilization for primary repair of the anterior cruciate ligament

PURPOSE

New strategies for dynamic intraligamentary stabilization (DIS) in the primary repair of anterior cruciate ligament (ACL) ruptures are currently under debate. It has been proposed that these might serve as alternative techniques to conventional ACL reconstruction procedures using tendon autografts. The aims of the present investigation were to evaluate the functional results and critically assess the complication rate following primary ACL repair with DIS and to review existing reports of favourable clinical results with the method in relation to knee joint stability and patient satisfaction.

METHODS

Fifty-nine patients received dynamic intraligamentary stabilization a mean of 14 days after ACL rupture. Fifty-seven patients (96.6%, male:female = 37:20; mean age 27.6 years) were available for follow-up examinations including the Tegner activity level, anteroposterior stability in comparison with the uninjured knee, subjective satisfaction, and range of knee motion. Complications after 3 and 12 months were also analyzed. Associated lesions requiring surgical measures were found in 30 patients.

RESULTS

A statistically significant decrease in Tegner activity levels was detected between the preoperative status (median 7) and the 12-month follow-up (median 5). The overall complication rate was 57.9%, including rerupture or non-healing (n = 10, 17.5%), repeat arthroscopy (n = 13, 22.8%) as a result of meniscus tears (n = 2, 15.4%), cyclops syndrome (n = 4, 30.8%) or restricted range of motion (n = 7, 53.8%), arthrofibrosis (n = 3, 5.3%), and implant interference (n = 7, 12.3%). Anteroposterior KT-1000 stability of 3 mm or below was achieved in 29 (50.9%) patients.

CONCLUSIONS

The DIS procedure does not appear to be appropriate for providing predictable results in a young and active cohort of patients following ACL rupture, as it has an unacceptably high complication rate and leads to residual anteroposterior knee joint laxity of 3 mm or more in 28 (49.1%) of cases.

LEVEL OF EVIDENCE

IV (prospective case series).

Femoral Tunnel Drilling Method: Risk of Reoperation and Revision After Anterior Cruciate Ligament Reconstruction

BACKGROUND

The femoral tunnel in anterior cruciate ligament reconstruction (ACLR) can be created by the transtibial (TT) or tibial-independent (TI) methods. An anatomically located femoral tunnel can be more consistently achieved by TI methods, which include the anteromedial portal and lateral (outside-in, retrodrill) techniques. Nonanatomic graft placement in ACLR can result in postoperative instability and meniscal or chondral injury. An anatomically located graft is subjected to higher postoperative physiologic forces than one placed nonanatomically.

PURPOSE

To examine isolated primary ACLR and determine the risk of aseptic revision and reoperation based on femoral tunnel drilling method.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

The ACLR registry of an integrated US health care system was used to identify primary isolated unilateral ACLRs from 2009 to 2014. Multivariable Cox proportional hazard regression models were used to evaluate risk for aseptic revision for graft failure and aseptic reoperation for meniscal or chondral injury according to femoral tunnel drilling method: TI versus TT. Models included age, sex, body mass index (BMI), race, graft type, and femoral fixation type as covariates.

RESULTS

The cohort included 19,059 patients with primary ACLR. The mean age was 28.9 years (SD, 11.5), 6991 patients (36.8%) were younger than 22 years, 11,795 patients (61.9%) were male, 7648 patients (40.1%) had a BMI less than 25 kg/m², 8913 patients (46.8%) were white, and 7357 patients (38.6%) received an allograft. Median follow-up was 2.30 years (interquartile range, 1.08-3.77). TI techniques were used for 12,342 (64.8%) of the ACLRs, and the TT method was used for 6717 (35.2%). Use of TI techniques increased from 33.6% of all ACLRs in 2009 to 83.4% in 2014. After adjustment for covariates, the TI group had a higher risk for aseptic revision than the TT group (hazard ratio [HR], 1.28; 95% CI, 1.04-1.56), and this risk was 1.41 times higher in patients younger than 22 years specifically. The 5-year cumulative reoperation probability was lower in the TI group (4.50%; 95% CI, 3.78%-5.36%) compared with the TT group (5.06%; 95% CI, 4.31-5.94%). After adjustment for the covariates, no difference in risk for aseptic reoperation was observed (HR, 1.08; 95% CI, 0.85-1.39).

CONCLUSION

In the largest known study of its type examining femoral tunnel drilling method for primary ACLR, after adjustment for age, sex, BMI, race, graft type, and femoral fixation, TI techniques were found to carry higher risk of aseptic revision compared with the TT method, while no difference was observed in risk for aseptic reoperation.

Individualized Anterior Cruciate Ligament Graft Matching: In Vivo Comparison of Cross-sectional Areas of Hamstring, Patellar, and Quadriceps Tendon Grafts and ACL Insertion Area

BACKGROUND

Recent literature correlated anterior cruciate ligament (ACL) reconstruction failure to smaller diameter of the harvested hamstring (HS) autograft. However, this approach may be a simplification, as relation of graft size to native ACL size is not typically assessed and oversized grafts may impart their own complications.

PURPOSE

To evaluate in vivo data to determine if the commonly used autografts reliably restore native ACL size.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Intraoperative data of the tibial insertion area and HS graft diameter were collected and retrospectively evaluated for 46 patients who underwent ACL reconstruction with HS autografts. Magnetic resonance imaging measurements of the cross-sectional area (CSA) of the possible patellar tendon (PT) and quadriceps tendon (QT) autografts were also done for each patient. The percentages of tibial insertion site area restored by the 3 possible grafts were then calculated and compared for each individual.

RESULTS

The mean ACL tibial insertion area was 107.2 mm² (60.5-155.5 mm²). The mean CSAs of PT, HS, and QT were 33.2, 55.3, and 71.4 mm², respectively. When all grafts were evaluated, the percentage reconstruction of the insertion area varied from 16.2% to 123.1% on the tibial site and from 25.5% to 176.7% on the femoral site, differing significantly for each graft type ( P < .05). On average, 32.8% of the tibial insertion area would have been filled with PT, 53.6% by HS, and 69.5% by QT. Based on previous cadaveric studies indicating that graft size goal should be 50.2% ± 15% of the tibial insertion area, 82.7% of patients in the HS group were within this range (36.9%, QT; 30.5%, PT), while 65.2% in the PT group were below it and 60.9% in the QT group were above it.

CONCLUSION

ACL insertion size and the CSAs of 3 commonly used grafts vary greatly for each patient and are not correlated with one another. Thus, if the reconstructed ACL size is determined by the harvested autograft size alone, native ACL size may not be adequately restored. PT grafts tended to undersize the native ACL, while QT might oversize it.

CLINICAL RELEVANCE

These results may help surgeons in preoperative planning, as magnetic resonance imaging measurements can be helpful in determining individualized graft choice to adequately restore the native ACL.

Intraoperative Graft Isometry in Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction

Purpose

Little is known about the isometry of anatomic single-bundle anterior cruciate ligament (ACL) tunnel positions in vivo although it is closely related to graft tension throughout the range of motion. The purpose of this study was to evaluate intraoperative graft isometry in anatomic single-bundle ACL reconstruction in vivo.

Materials and Methods

Graft length changes were assessed before bio-screw fixation in the tibial tunnel by pulling the graft with tensions of 20 lbs and 30 lbs in full extension at flexion angles of 30°, 60°, 90°, and 120°.

Results

At the flexion angle of 30°, 20 lbs and 30 lbs of tension showed −0.4 mm and −0.6 mm length changes, respectively. The greater the flexion angle of the knee, the shorter the graft length in the joint. At the flexion angles of 90° and 120°, there was significant difference in the graft length change between 20 lbs and 30 lbs of tension.

Conclusions

Anatomic single-bundle ACL reconstruction was non-isometric. The graft length was the longest in full extension. The tension of graft became loose in flexion. At the flexion angles of 90° and 120°, there was significant difference in the graft length change between 20 lbs and 30 lbs of tension.

Three-dimensional isotropic magnetic resonance imaging can provide a reliable estimate of the native anterior cruciate ligament insertion site anatomy

PURPOSE

This study quantified the error in anterior cruciate ligament (ACL) insertion site location and area estimated from three-dimensional (3D) isotropic magnetic resonance imaging (MRI) by comparing to native insertion sites determined via 3D laser scanning.

METHODS

Isotropic 3D DESS MRI was acquired from twelve fresh-frozen, ACL-intact cadaver knees. ACL insertion sites were manually outlined in each MRI slice, and the resulting contours combined to determine the 3D insertion site shape. Specimens were then disarticulated, and the boundaries of the ACL insertion sites were digitized using a high-accuracy laser scanner. MRI and laser scan insertion sites were co-registered to determine the percent overlapping area and difference in insertion centroid location.

RESULTS

Femoral ACL insertion site area averaged 112.7 ± 17.9 mm² from MRI and 109.7 ± 10.9 mm² from laser scan (p = 0.345). Tibial insertion area was 134.7 ± 22.9 mm² from MRI and 135.2 ± 15.1 mm² from laser scan (p = 0.881). Percentages of overlapping area between modalities were 82.2 ± 10.2% for femurs and 81.0 ± 9.0% for tibias. The root-mean-square differences for ACL insertion site centroids were 1.87 mm for femurs and 2.49 mm for tibias. The MRI-estimated ACL insertion site centroids were biased on average 0.6 ± 1.6 mm proximally and 0.3 ± 1.9 mm posteriorly for femurs, and 0.3 ± 1.1 mm laterally and 0.5 ± 1.5 mm anteriorly for tibias.

CONCLUSION

Errors in ACL insertion site location and area estimated from 3D-MRI were determined via comparison with a high-accuracy 3D laser scanning. Results indicate that MRI can provide estimates of ACL insertion site area and centroid location with clinically applicable accuracy. MRI-based assessment can provide a reliable estimate of the native ACL anatomy, which can be helpful for surgical planning as well as assessment of graft tunnel placement.

Current Strategies and Future Directions to Optimize ACL Reconstruction in Adolescent Patients

The incidence of anterior cruciate ligament (ACL) injuries in the pediatric population has risen in recent years. These injuries have historically presented a management dilemma in skeletally immature patients with open physes and significant growth remaining at time of injury. While those nearing skeletal maturity may be treated with traditional, transphyseal adult techniques, these same procedures risk iatrogenic damage to the growth plates and resultant growth disturbances in younger patients with open physes. Moreover, conservative management is non-optimal as significant instabilities of the knee remain. Despite the development of physeal-sparing reconstructive techniques for younger patients, there remains debate over which procedure may be most suitable on a patient to patient basis. Meanwhile, the drivers behind clinical and functional outcomes following ACL reconstruction remain poorly understood. Therefore, current strategies are not yet capable of optimizing surgical ACL reconstruction on an individualized basis with absolute confidence. Instead, aims to improve surgical treatment of ACL tears in skeletally immature patients will rely on additional approaches in the near future. Namely, finite element models have emerged as a tool to model complex knee joint biomechanics. The inclusion of several individualized variables such as bone age, three dimensional geometries around the knee joint, tunnel positioning, and graft tension collectively present a possible means of better understanding and even predicting how to enhance surgical decision-making. Such a tool would serve surgeons in optimizing ACL reconstruction in the skeletally immature individuals, in order to improve clinical outcomes as well as reduce the rate of post-operative complications.

Stress distribution is deviated around the aperture of the femoral tunnel in the anatomic anterior cruciate ligament reconstruction

PURPOSE

Final tunnel location in the anterior cruciate ligament (ACL) reconstruction is unpredictable due to tunnel widening and/or transposition. The mechanical stress around the tunnel aperture seems to be a major factor but is not fully investigated. The purpose of this study was to measure the stress from the ACL graft around the tunnel aperture when the ACL graft tension reaches its peak.

METHODS

Six cadaveric knees were used. Single-bundle ACL reconstruction was performed using a hamstrings graft. Both femoral and tibial tunnels were created at the centre of the original ACL footprint. A 7-mm-internal-diameter aluminium cylinder with pressure sensors was placed in the femoral tunnel. Hamstrings graft with a microtension sensor was inserted. After fixation, passive extension-flexion was performed while monitoring the tunnel aperture pressure and the graft tension simultaneously. The pressure on the femoral tunnel aperture when the ACL graft tension reach its peak was compared between four directions.

RESULTS

The ACL graft tension peaked (67 ± 49 N) at full extension (-5.8 ± 4.1°). Pressure at the femoral tunnel aperture was different between different directions (p < 0.01). Distal part had significantly larger pressure (1.7 ± 1.3 MPa) than the other directions (p < 0.01). Second largest pressure was carried in the anterior part (0.6 ± 0.5 MPa), followed by proximal and posterior parts (0.4 ± 0.3, 0.2 ± 0.2 MPa respectively).

CONCLUSION

The stress distribution at the femoral tunnel aperture is not equal in different directions, while the distal part dominantly bears the stress from the ACL graft. Surgeons should pay close attention to the distal edge of the femoral tunnel which should be inside the anatomic ACL footprint eventually.

Sagittal femoral condyle morphology correlates with femoral tunnel length in anatomical single bundle ACL reconstruction

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length and the morphology of the femoral intercondylar notch in anatomical single bundle anterior cruciate ligament (ACL) reconstruction using three-dimensional computed tomography (3D-CT).

METHODS

Thirty subjects undergoing anatomical single bundle ACL reconstruction were included in this study (23 female, 7 male: average age 45.5 ± 16.7). In the anatomical single bundle ACL reconstruction, the femoral and tibial tunnels were created close to the antero-medial bundle insertion site with trans-portal technique. Using post-operative three-dimensional computed tomography (3D-CT), accurate axial and lateral views of the femoral condyle were evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the transepicondylar length (TEL), notch width index, notch outlet length, the notch area (axial), length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analyzed. Tunnel placement was also evaluated using a Quadrant method.

RESULTS

The average femoral tunnel length was 35.4 ± 4.4 mm. The average TEL, NWI, notch outlet length, and the axial notch area, were 76.9 ± 5.1 mm, 29.1 ± 3.8%, 19.5 ± 3.9 mm, and 257.4 ± 77.4 mm², respectively. The length of Blumensaat's line and the height and area of the lateral wall of the femoral intercondylar notch were 33.8 ± 3.2 mm, 22.8 ± 2.3 mm, and 738.7 ± 129 mm², respectively. The length of Blumensaat's line, the height, and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 23.4 ± 4.5% in a shallow-deep direction and 35.4 ± 8.8% in a high-low direction.

CONCLUSION

The length of Blumensaat's line, height, and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single bundle ACL reconstruction. For clinical relevance, these parameters are useful in predicting the length of the femoral tunnel in anatomical single bundle ACL reconstruction for the prevention of extremely short femoral tunnel creation.

LEVEL OF EVIDENCE

Case controlled study, Level III.

Comparison of Clinical Results, Second-Look Arthroscopic Findings, and MRI Findings Between the Transportal and Outside-In Techniques for Double-Bundle Anatomic Anterior Cruciate Ligament Reconstruction: A Prospective, Randomized Controlled Trial With a Minimum 2-Year Follow-up

BACKGROUND

Although image analysis has shown that the outside-in (OI) technique is associated with different femoral tunnel geometry than the transportal (TP) technique in anatomic anterior cruciate ligament (ACL) reconstruction, it is not known whether clinical results differ between the 2 techniques.

PURPOSE

To compare clinical results, second-look arthroscopic findings, and magnetic resonance imaging (MRI) findings between the TP and OI techniques in anatomic double-bundle (DB) ACL reconstruction.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

From November 2010 to March 2013, 128 patients were enrolled in this study and were randomly assigned to either the TP group (64 patients) or the OI group (64 patients), and DB ACL reconstructions were performed. At the minimum 2-year follow-up (34.9 ± 10.9 months), 111 patients (86.7%) were evaluated with multiple clinical scores and stability tests (KT-2000 arthrometer, Lachman test, and pivot-shift test). Ninety-three knees were evaluated for graft continuity, graft tension, and synovialization by use of second-look arthroscopy. Seventy-eight knees were evaluated on MRI for graft continuity, femoral graft tunnel healing, and graft signal/noise quotient (SNQ). The primary outcome was KT-2000 arthrometer results. Results were compared between the TP and OI groups.

RESULTS

No significant differences were found between the 2 groups in terms of KT-2000 arthrometer results, which was the primary outcome, and other clinical results, with the exception of the postoperative functional test of International Knee Documentation Committee (IKDC) objective score. The ratio of grade A and B on the postoperative functional test of IKDC objective score was significantly larger for the OI group (51/58) than the TP group (36/53) ( P = .005). The second-look arthroscopic findings were not significantly different between the 2 groups in either bundle ( P > .05). In addition, MRI findings did not differ significantly between the 2 groups ( P > .05).

CONCLUSION

With the exception of the functional test of IKDC objective score, we found that clinical results, second-look arthroscopic findings, and MRI findings did not differ significantly between the OI and TP techniques for anatomic ACL reconstruction, although femoral tunnel geometries differed significantly between the 2 techniques.

The importance of Blumensaat's line morphology for accurate femoral ACL footprint evaluation using the quadrant method

PURPOSE

The purpose of this study was to evaluate the difference in the center position of the ACL footprint based on grid placement using the quadrant method according to the morphological variations of the Blumensaat's line.

METHODS

Fifty-nine non-paired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch, and the digital images were evaluated using Image J software. The femoral ACL footprint was periphery outlined and the center position was automatically measured. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight, small hill, and large hill types. From the images, grid quadrants were placed as: Grid (1) without consideration of hill existence and not including the chondral lesion. Grid (2) without consideration of hill existence and including the chondral lesion. Grid (3) with consideration of hill existence and not including the chondral lesion. Grid (4) with consideration of hill existence and including the chondral lesion.

RESULTS

The straight type consisted of 19 knees, the small hill type 13 knees, and the large hill type 27 knees. Depending on the quadrant grid placement, significant center position difference was observed both in the shallow-deep, and high-low direction. When hill existence was considered, the center position of the ACL was significantly changed to a high position.

CONCLUSION

The center position of the ACL footprint exhibited significant differences according to Blumensaat's line morphology. For clinical relevance, when ACL surgery is performed in knees with small or large hill type variations, surgeons should pay close attention to femoral tunnel evaluation and placement, especially when using the quadrant method.

Contact area between femoral tunnel and interference screw in anatomic rectangular tunnel ACL reconstruction: a comparison of outside-in and trans-portal inside-out techniques

PURPOSE

The purpose of this study was to compare the femoral tunnel length, the femoral graft bending angle at the femoral tunnel aperture, and the contact area between the femoral tunnel wall and an interference screw used for fixation in anatomic rectangular tunnel anterior cruciate ligament (ACL) reconstruction (ART ACLR).

METHODS

The study included 149 patients with primary ACL injury who underwent ART ACLR. Preoperatively, flexion angle of the index knee was checked under general anaesthesia. Those of less than 130° of passive flexion were assigned to the outside-in (OI) technique (78 patients), while the others to the trans-portal inside-out (TP) technique (71 patients). The patients underwent computed tomography with multiplanar reconstruction at 3-5 weeks post-operatively. Femoral tunnel length, graft bending angle, and contact ratio between the IFS and femoral tunnel were assessed. P < 0.05 was considered statistically significant.

RESULTS

The femoral tunnel length in the OI technique was significantly longer than that in the TP technique (P < 0.001). The femoral graft bending angle in the OI technique was significantly more acute than that in the TP technique (P < 0.001). The contact ratio in the OI technique was significantly larger than that in the TP technique at every point in the femoral tunnel (P < 0.001).

CONCLUSIONS

The OI technique resulted in a more acute femoral graft bending angle, longer mean femoral tunnel length, and larger contact ratio than the TP technique after ART ACLR.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.