ACL Fibers Near the Lateral Intercondylar Ridge Are the Most Load Bearing During Stability Examinations and Isometric Through Passive Flexion

Bone Density Distribution Pattern in the Lateral Wall of the Femoral Intercondylar Notch: Implications for the Direct Insertion of the Femoral ACL Attachment

Background

The ideal position of the femoral bone tunnel in the anterior cruciate ligament (ACL) is controversial. The functional importance of the ACL fiber varies depending on where it is attached to the femur. Functionally important fibers can cause high mechanical stress on the bone, and the Wolff law predicts that bone mineral density will increase at high mechanical stress sites.

Purpose/Hypothesis

The purpose of this study was to use computed tomography imaging to determine the distribution pattern of bone density in the lateral intercondylar wall. It was hypothesized that the high-density area (HDA) of the lateral intercondylar wall would reflect the functional insertion of the ACL as reported in previous anatomic studies.

Study Design

Descriptive epidemiology study.

Methods

Data from 39 knees without ACL injuries were retrospectively collected. The HDA of the lateral intercondylar wall was defined as the region containing the top 10% of the radiodensity values. The shape of the HDA was approximated as an ellipse, and the quadrant method was used to determine the center of the ellipse. The association between the ratio of the minor axis to the major axis of the ellipse and background characteristics was investigated.

Results

According to the quadrant method, the center of the HDA ellipse was 33.6% in the deep-shallow direction and 23.4% in the high-low direction. The center of the ellipse was comparable to the anatomic center of the ACL footprint, as previously reported. The ratio of the minor axis to the major axis of the ellipse was 0.58 (95% CI, 0.54-0.62). There was a significant negative correlation between the ratio of the minor axis to the major axis of the HDA ellipse and the posterior tibial slope (r = -0.38, P = .02).

Conclusion

The center of the HDA ellipse was found to be similar to the anatomic center of the ACL footprint. Considering the mechanical stress responses in bone, the HDA of the lateral intercondylar wall has the potential to represent the ACL insertion, especially functional insertion.

Effects of higher femoral tunnels on clinical outcomes, MRI, and second-look findings in double-bundle anterior cruciate ligament reconstruction with a minimal 5-year follow-up

BACKGROUND

To perform anatomical anterior cruciate ligament reconstruction (ACLR), tunnels should be placed relatively higher in the femoral anterior cruciate ligament (ACL) footprint based on the findings of direct and indirect femoral insertion. But the clinical results of higher femoral tunnels (HFT) in double-bundle ACLR (DB-ACLR) remain unclear. The purpose was to investigate the clinical results of HFT and lower femoral tunnels (LFT) in DB-ACLR.

METHODS

From September 2014 to February 2016, 83 patients who underwent DB-ACLR and met the inclusion and exclusion criteria were divided into HFT-ACLR (group 1, n = 37) and LFT-ACLR (group 2, n = 46) according to the position of femoral tunnels. Preoperatively and at the final follow-up, clinical scores were evaluated with International Knee Documentation Committee (IKDC), Tegner activity, and Lysholm score. The stability of the knee was evaluated with KT-2000, Lachman test, and pivot-shift test. Cartilage degeneration grades of the International Cartilage Repair Society (ICRS) were evaluated on magnetic resonance imaging (MRI). Graft tension, continuity, and synovialization were evaluated by second-look arthroscopy. Return-to-sports was assessed at the final follow-up.

RESULTS

Significantly better improvement were found for KT-2000, Lachman test, and pivot-shift test postoperatively in group 1 ( P >0.05). Posterolateral bundles (PL) showed significantly better results in second-look arthroscopy regarding graft tension, continuity, and synovialization ( P <0.05), but not in anteromedial bundles in group 1. At the final follow-up, cartilage worsening was observed in groups 1 and 2, but it did not reach a stastistically significant difference ( P >0.05). No statistically significant differences were found in IKDC subjective score, Tegner activity, and Lysholm score between the two groups. Higher return-to-sports rate was found in group 1 with 86.8% (32/37) vs. 65.2% (30/46) in group 2 ( P = 0.027).

CONCLUSION

The HFT-ACLR group showed better stability results, better PL, and higher return-to-sports rate compared to the LFT-ACLR group.

Editorial Commentary: The Number One Cause of Anterior Cruciate Ligament Reconstruction Graft Failure Is a Misplaced Femoral Tunnel: Over-the-Top Technique Plus Lateral Extra-Articular Tenodesis Is Recommended

Patient factors (notably high tibial slope and narrow femoral intercondylar notch width) and surgical factors (including meniscus treatment and anterior cruciate ligament [ACL] tunnel position) contribute to ACL reconstruction failure. The number one cause of failure is a misplaced ACL femoral tunnel. Tunnel malposition leads to a higher incidence of postoperative meniscal lesions, inferior clinical outcomes, and higher revision rates.

A Cadaveric Study of the Optimal Isometric Region on the Anterolateral Surface of the Knee in Anterolateral Ligament Reconstruction

OBJECTIVE

Isolated intra-articular anterior cruciate ligament (ACL) reconstruction is not capable of restoring instability in many cases leading some to recommend concomitant anterolateral ligament (ALL) reconstruction. The satisfactory fixation site and graft length change are crucial in ligament reconstruction to restore the ALL function and avoid some unwanted graft behavior. The purpose of this investigation is to determine the optimal isometric region on the anterolateral aspect of the knee for ALL reconstruction using a three-dimensional optical instrument and a suture similar to an intraoperative isometric test.

METHODS

Six freshly frozen cadaveric human knees were used in this study. Data regarding the anterolateral surface were obtained using an optical measurement system to create a three-dimensional model. Nine points were selected on the femur (F1-F9) and tibia (Ta-Ti) respectively. The three-dimensional length change between each pair of tibial and femoral points was measured during passive knee flexion from 0° to 90° in 15° increments. Subsequently, five femoral points (A-E) were selected from the lateral femur, located in different areas relative to the lateral femoral epicondyle, and three tibial reference points (T1-T3) were selected in the isometric test. The changes in the length between each pair of reference points were measured using sutures. The 95% confidence interval for the rate of length change was estimated using the mean and standard deviation of the maximum rate of length change at different flexion angles, and the data were expressed as the mean (95% confidence interval) and compared with the maximum acceptable rate of change (10%).

RESULTS

The maximum acceptable change rate for ligament reconstruction is 10%, and the mean maximum rates and the 95% confidence interval (CI) of length change for the point combinations were calculated. Among all the combined points measured using the optical measurement system and the suture, the qualified point combination for reconstruction was F3 (8mm posterior and 8mm proximal to the lateral femoral epicondyle)-Tb (8mm proximal to the midpoint between the center of Gerdy's tubercle and the fibula head), A (posterior and proximal to the lateral femoral epicondyle)-T2 (10mm below the joint line)and A-T3 (15 mm below the joint line). The position of F3-Tb and A-T2 are close to each other.

CONCLUSION

The most isometric area of the femur for ALL reconstruction was posterior and proximal to the lateral femoral epicondyle. We recommend that the initial location of the femoral point be set at 8 mm posterior and 8 mm proximal to the lateral femoral epicondyle and the tibial point at approximately 10 mm below the joint line, midway between Gerdy's tubercle and fibular head, and subsequently adjusted to the most satisfactory position according to the isometric test.

Increased ACL direct insertion coverage provided more positive biomechanical effects on graft and bone tunnel during knee flexion: a simulation study

PURPOSE

Flattened femoral tunnels were recently applied in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction. Little is known about the biomechanical effect of such changes during knee flexion. The aim of the present simulation study was to assess the effect of altered ACL direct insertion coverage on the biomechanics of the graft and bone tunnel.

METHODS

Five finite element (FE) models, including a round femoral tunnel and four progressively flattened rounded rectangular femoral tunnels, were established to represent the ACL reconstructions. In vivo knee kinematics data obtained from the validated dual fluoroscopic imaging techniques controlled the FE models to simulate lunge motions. The maximal principal stress of the graft and the volume of equivalent strain within 1000-3000 microstrain (V1000-3000) of the cancellous bone were subsequently calculated at 0°, 30°, 60° and 90° of knee flexion.

RESULTS

A lower stress state on the graft and a more beneficial strain state on the cancellous bone were observed when the femoral tunnel better covered the ACL direct insertion. The average maximal principal stress of each model were 3.93 ± 0.60 MPa, 3.82 ± 0.54 MPa, 3.43 ± 0.44 MPa, 3.45 ± 0.44 MPa and 3.05 ± 0.43 MPa, respectively. The average V1000-3000 of the cancellous bone of each model were 179.06 ± 89.62 mm3, 221.40 ± 129.83 mm3, 247.57 ± 157.78 mm3, 282.74 ± 178.51 mm3 and 295.71 ± 162.59 mm3, respectively. Both the stress and strain values exhibited two peaks during the flexion simulation. The highest value occurred at 30° of flexion, and the second highest value occurred at 90° of flexion.

CONCLUSIONS

Increased ACL direct insertion coverage provided more positive biomechanical effects after anatomical single-bundle ACL reconstruction during knee flexion.

The 25-year experience of over-the-top ACL reconstruction plus extra-articular lateral tenodesis with hamstring tendon grafts: the story so far

This article presents with an evidence based approach, the kinematical rationale, biological evidence and the long term results of the "Over-The-Top" anterior cruciate ligament reconstruction with lateral plasty technique. This surgery was developed more than 25 years ago at the Rizzoli Institute by professor Marcacci and Zaffagnini and it is still widely performed in many orthopedic center worldwide.

Rebranding the 'anatomic' ACL reconstruction: Current concepts

The anterior cruciate ligament (ACL) is a complex ribbon-like structure, which is approximately 3.5 times larger at the tibial and femoral insertions than at the midpoint. Accordingly, it is impossible to recreate with a single cylindrical graft. However, this has not stopped surgeons from using the term "anatomic" to describe multiple ACL reconstruction techniques inserting at a number of different locations within the original ACL footprint, causing confusion. The term "anatomic" should be discarded and replaced by an anatomic description of the tunnel placements on the tibia and femur. Current ACL reconstruction techniques cite anatomical studies that identified "direct and indirect fibres" of the ACL. The "direct fibres" bear 85-95% of the load and provide the main resistance to both anterior tibial translation and internal rotation/pivot shift. On the femur, these fibres insert in a line just posterior to the intercondylar ridge and comprise the portion of the ACL that surgeons should strive to restore. Placement of the graft just posterior to the intercondylar ridge creates a line of placement options from the anteromedial bundle to the "central" position and finally to the posterolateral bundle position. The authors prefer placing the femoral tunnel in the isometric anteromedial position and addressing a high-grade pivot shift at the IT-band with a lateral extra-articular tenodesis. As with the femoral tunnel, the native ACL footprint on the tibia is much larger than the ACL graft and thus can be placed in multiple "anatomic" locations. The authors prefer placement of the tibial tunnel in the anterior most position of the native footprint that does not cause impingement in the femoral notch. Additional research is needed to determine the ideal tunnel positions on the femur and tibia and validating the technique with patient outcomes. However, this cannot be accomplished without describing tunnel placement with specific anatomical locations so other surgeons can replicate the technique.

Reconstruction of the Anterior Cruciate Ligament Using Ruler-Assisted Positioning of the Femoral Tunnel Relative to the Posterior Apex of the Deep Cartilage: A Single-Center Case Series

The techniques available to locate the femoral tunnel during anterior cruciate ligament (ACL) reconstruction have notable limitations. To evaluate whether the femoral tunnel center could be located intraoperatively with a ruler, using the posterior apex of the deep cartilage (ADC) as a landmark. This retrospective case series included consecutive patients with ACL rupture who underwent arthroscopic single-bundle ACL reconstruction at the Department of Orthopedics, Beijing Tongren Hospital between January 2014 and May 2018. During surgery, the ADC of the femoral lateral condyle was used as a landmark to locate the femoral tunnel center with a ruler. Three-dimensional computed tomography (CT) was performed within 3 days after surgery to measure the femoral tunnel position by the quadrant method. Arthroscopy was performed 1 year after surgery to evaluate the intra-articular conditions. Lysholm and International Knee Documentation Committee (IKDC) scores were determined before and 1 year after surgery. The final analysis included 82 knees of 82 patients (age = 31.7 ± 6.1 years; 70 males). The femoral tunnel center was 26 ± 1.5% in the deep-shallow (x-axis) direction and 31 ± 3.1% in the high-low (y-axis) direction, close to the "ideal" values of 27 and 34%. Lysholm score increased significantly from 38.5 (33.5-47) before surgery to 89 (86-92) at 1 year after surgery (p < 0.001). IKDC score increased significantly from 42.5 (37-47) before surgery to 87 (83.75-90) after surgery (p < 0.001). Using the ADC as a landmark, the femoral tunnel position can be accurately selected using a ruler.

ACL Graft Matching: Cadaveric Comparison of Microscopic Anatomy of Quadriceps and Patellar Tendon Grafts and the Femoral ACL Insertion Site

BACKGROUND

The optimal graft choice between the bone-patellar tendon-bone (BPTB) and the quadriceps tendon remains controversial. Studies evaluating the microscopic anatomy of the quadriceps tendon-patellar bone (QTB) and BPTB grafts for anterior cruciate ligament (ACL) reconstruction are currently lacking.

HYPOTHESIS

The relationship between post-ACL reconstruction graft bending angle (GBA) and the angle corresponding to the GBA (cGBA) would indicate that the BPTB can bend more than the QTB at the femoral tunnel aperture.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty paired human cadaveric knees fixed at <10° of knee joint flexion (mean age, 82.5 years) underwent histological sectioning and staining with Masson trichrome and toluidine blue. The femoral ACL insertion, QTB graft, and BPTB graft were microscopically analyzed. The width of the direct insertion, thickness of the uncalcified fibrocartilage and calcified fibrocartilage, ligament attachment angle, and cGBA for each group were measured. Eighteen patients who underwent ACL reconstruction with QTB or BPTB autograft were included for the evaluation of GBA using computed tomography images at 1 week postoperatively.

RESULTS

The mean insertion widths of the femoral ACL, QTB, and BPTB were 7.81, 9.07, and 6.54 mm, respectively. The QTB was 16% wider than the ACL, while the BPTB was 16% narrower than the ACL. The mean insertion thicknesses of the femoral ACL, QTB, and BPTB were 0.53, 0.94, and 0.38 mm, respectively. The QTB was 77% thicker than the ACL (P < .001), while the BPTB was 28% thinner than the ACL (P = .017). The mean ligament attachment angles of the femoral ACL, QTB, and BPTB were 20.3°, 30.2°, and 33.3°, respectively, and the QTB and the BPTB were 49% and 64% larger, respectively, than the ACL. The mean cGBAs of the femoral ACL, QTB, and BPTB were 33.9°, 35.1°, and 12.3°, respectively. The BPTB was 64% smaller than the ACL, while there was no significant difference between the QTB and the ACL. The mean GBA was 57.7°.

CONCLUSION

The insertion width and thickness were significantly greater and smaller in the QTB and BPTB grafts, respectively, than in the ACL. The relationship between GBA after ACL reconstruction and cGBA in knee extension indicates that at the femoral tunnel aperture, the BPTB can bend more than the QTB.

CLINICAL RELEVANCE

QTB graft may allow more anatomic ACL reconstruction to be performed.

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

Background:

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

Purposes:

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

Study Design:

Descriptive laboratory study.

Methods:

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

Results:

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

Conclusion:

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

Clinical Relevance:

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

Does remnant tissue preservation in anterior cruciate ligament reconstruction influence the creation of the rectangular femoral tunnel?

PURPOSE

We have previously described anterior cruciate ligament reconstruction with a rounded rectangular femoral tunnel created using a rounded rectangular dilator designed to enable a more anatomical and wider tendon-bone junction. However, the influence of remnant tissue preservation on the creation of the rounded rectangular femoral tunnel is not clear. This study aimed to evaluate the influence of remnant tissue preservation on the creation of the rounded rectangular femoral tunnel.

METHODS

A total of 198 patients who underwent primary anterior cruciate ligament reconstruction with a rounded rectangular femoral tunnel were evaluated retrospectively. Patients were categorized into a remnant preservation group (group P) and a non-preservation group (group N). Computed tomography images taken 1 week postoperatively were analyzed. The location of the rounded rectangular femoral tunnel evaluated using the quadrant method, its rotation angle, and the graft bending angle were compared between the two groups. The differences and the variance in femoral tunnel assessment were compared using the two-sample t-test and Levene's test.

RESULTS

Although there was no significant difference in the location of femoral tunnel for the deep/shallow direction along the Blumensaat's line (difference, p = .326; variances, p = .970), the tunnel was significantly lower in group P than in group N, with no variances (difference, p = .001; variances, p = .326). There were no significant differences and no variances in the tunnel rotation angle and the graft bending angle (difference, p = .727 and 0.514, respectively; variances, p = .827 and .445, respectively). Blow out of the posterior wall of the medial aspect of the femoral lateral condyle was an intraoperative complication that occurred in one case in group N.

CONCLUSION

The remnant preservation approach creates a lower femoral tunnel compared to the non-preservation technique. However, a rounded rectangular femoral tunnel can be created safely and is reproducible with remnant tissue preservation.

Anterior cruciate ligament graft forces are sensitive to fixation angle and tunnel position within the native femoral footprint during passive flexion

BACKGROUND

Anterior cruciate ligament (ACL) graft position within the anatomic femoral footprint of the native ACL and the flexion angle at which the graft is fixed (i.e., fixation angle) are important considerations in ACL reconstruction surgery. However, their combined effect on ACL graft force remains less well understood.

HYPOTHESIS

During passive flexion, grafts placed high within the femoral footprint carry lower forces than grafts placed low within the femoral footprint (i.e., high and low grafts, respectively). Forces carried by high grafts are independent of fixation angle. All reconstructions impart higher forces on the graft than those carried by the native ACL.

STUDY DESIGN

Controlled laboratory study.

METHODS

Five fresh-frozen cadaveric knees were mounted to a robotic manipulator and flexed from full extension to 90° of flexion. The ACL was sectioned and ACL force was calculated via superposition. ACL reconstructions were then performed using a patellar tendon autograft. For each knee, four different reconstruction permutations were tested: high and low femoral graft positions fixed at 15° and at 30° of flexion. Graft forces were calculated from full extension to 90° of flexion for each combination of femoral graft position and fixation angle again via superposition. Native ACL and ACL graft forces were compared through early flexion (by averaging tissue force from 0 to 30° of flexion) and in 5° increments from full extension to 90° of flexion.

RESULTS

When fixed at 30° of flexion, high grafts carried less force than low grafts through early flexion bearing a respective 64 ± 19 N and 88 ± 11 N (p = 0.02). Increasing fixation angle from 15° to 30° caused graft forces through early flexion to increase 40 ± 13 N in low grafts and 23 ± 6 N in high grafts (p < 0.001). Low grafts fixed at 30° of flexion differed most from the native ACL, carrying 67 ± 9 N more force through early flexion (p < 0.001).

CONCLUSION

ACL grafts placed high within the femoral footprint and fixed at a lower flexion angle carried less force through passive flexion compared to grafts placed lower within the femoral footprint and fixed at a higher flexion angle. At the prescribed pretensions, all grafts carried higher forces than the native ACL through passive flexion.

CLINICAL RELEVANCE

Both fixation angle and femoral graft location within the anatomic ACL footprint influence graft forces and, therefore, should be considered when performing ACL reconstruction.

Reliability of Anatomic Bony Landmark Localization of the ACL Femoral Footprint Using 3D MRI

Background:

Nonanatomic placement of anterior cruciate ligament (ACL) grafts is a leading cause of ACL graft failure. Three-dimensional (3D) magnetic resonance imaging (MRI) femoral footprint localization could enhance planning for an ACL graft's position.

Purpose:

To determine the intra- and interobserver reliability of measurements of the ACL femoral footprint position and size obtained from 3D MRI scans.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 41 patients with complete ACL tears were recruited between November 2014 and May 2016. Preoperatively, a coronal-oblique proton-density fast spin echo 3D acquisition of the contralateral uninjured knee was obtained along the plane of the ACL using a 1.5T MRI scanner. ACL footprint parameters were obtained independently by 2 musculoskeletal radiologists (observers A and B). The distal and anterior positions of the center of the footprint were measured relative to the apex of the deep cartilage at the posteromedial aspect of the lateral femoral condyle, and the surface area of the ACL femoral footprint was approximated from multiplanar reformatted images. After 1 month, the measurements were repeated. Intraclass correlation coefficients (ICCs) were calculated to assess for intra- and interobserver reliability. Bland-Altman plots were produced to screen for potential systematic bias in measurement and to calculate limits of agreement.

Results:

The ICCs for intraobserver reliability of the ACL femoral distal and anterior footprint coordinates were 0.75 and 0.78, respectively, for observer A. For observer B, they were 0.75 and 0.74, respectively. The ICCs for interobserver reliability were 0.75 and 0.85 for the distal and anterior coordinates, respectively. Bland-Altman plots demonstrated no significant systematic bias. For surface area measurements, the intraobserver ICCs were 0.37 and 0.62 for observers A and B, respectively. The interobserver reliability was 0.60. Observer B consistently measured the footprints as slightly larger versus observer A (1.19 ± 0.27 vs 1 ± 0.22 cm², respectively; P < .001).

Conclusion:

Locating the center of the anatomic footprint of the ACL with 3D MRI showed substantial intra- and interobserver agreement. Interobserver agreement for the femoral footprint surface area was fair to moderate.

Failure load of the femoral insertion site of the anterior cruciate ligament in a porcine model: comparison of different portions and knee flexion angles

BACKGROUND

This study compared the failure load of the femoral insertion site of the anterior cruciate ligament between different portions and knee flexion angles.

METHODS

In total, 87 fresh-frozen, porcine knees were used in this study. Three knees were used for histological evaluation; the remaining 84 knees were randomly divided into 4 groups: anterior anteromedial bundle, posterior anteromedial bundle, anterior posterolateral bundle, and posterior posterolateral bundle groups (n=21 per group). The anterior cruciate ligament femoral insertion site was divided into these four areas and excised, leaving a 3-mm square attachment in the center of each bundle. Tibia-anterior cruciate ligament-femur complexes were placed in a material testing machine at 30°, 120°, and 150° of knee flexion (n=7), and the failure load for each portion was measured under anterior tibial loading (0.33 mm/s).

RESULTS

Histological study showed that the anterior cruciate ligament femoral insertion site consisted of direct and indirect insertions. Comparison of the failure load between the knee flexion angles revealed that all the failure loads decreased with knee flexion; significant decreases were observed in the failure load between 30 and 150° knee flexion in the posterior anteromedial bundle and posterior posterolateral bundle groups. Comparison of the failure load according to different portions revealed a significant difference between the anteromedial and posterolateral bundle groups at 150° of knee flexion, but no significant difference among the groups at 30° of flexion.

CONCLUSIONS

Although the failure load of the posterior portion decreased significantly in the knee flexion position, it (mainly consisting of indirect insertion) plays a significant role against anterior tibial load in the knee extension position; this appears to be related to the characteristics of the insertion site. Reflecting the complex structure and function of the ACL, this study showed that the failure load of the femoral insertion site varies with differences in positions and knee flexion angles.

The intercondylar fossa-A narrative review

The intercondylar fossa (“intercondylar notch,” IN) is a groove at the distal end of the femur, housing important stabilizing structures: cruciate ligaments and meniscofemoral ligaments. As the risk for injury to these structures correlates with changes to the IN, exact knowledge of its morphology, possible physiological and pathological changes and different approaches for evaluating it are important. The divergent ways of assessing the IN and the corresponding measurement methods have led to various descriptions of its possible shapes. Ridges at the medial and lateral wall are considered clinically important because they can help with orientation during arthroscopy, whereas ridges at the osteochondral border could affect the risk of ligament injury. Changes related to aging and sex differences have been documented, further emphasizing the importance of individual assessment of the knee joint. Overall, it is of the utmost importance to remember the interactions between the osseous housing and the structures within.

Femoral Tunnel Widening After Double-Bundle Anterior Cruciate Ligament Reconstruction With Hamstring Autograft Produces a Small Shift of the Tunnel Position in the Anterior and Distal Direction: Computed Tomography-Based Retrospective Cohort Analysis

PURPOSE

To determine whether the femoral tunnel position remains in an anatomical footprint after tunnel widening and shifting.

METHODS

Patients who underwent unilateral double-bundle anterior cruciate ligament reconstruction with hamstring autograft and performed computed tomography scan evaluation at the time of 5 days and 1 year postoperatively were included in this retrospective cohort study. Three-dimensional models of the femur and femoral tunnels were reconstructed from computed tomography scan data. The location of the tunnel center and tunnel margins in the anatomical coordinate system, and the mean shifting distance of tunnel center and margin were measured with image analysis software during the period. The change of tunnel center location in Bernard quadrant was confirmed if the tunnel center remained within the boundaries of anatomical position after tunnel widening.

RESULTS

A total of 56 patients satisfied the inclusion criteria. The mean shifting distance of AM and PL tunnel centers were 1.7 ± 0.9 mm and 1.6 ± 0.6 mm. The Tunnel margin of the anteromedial (AM) and posteromedial (PL) tunnels were shifted to 2.5 ± 1.3 mm and 2.6 ± 1.4 mm in the anterior direction, and 1.4 ± 0.9 mm and 1.0 ± 0.7 mm in the distal direction, respectively. Among the anatomical located tunnel, 97% (32/33) and 87.1% (27/31) of AM and PL tunnel centers remained in a range of anatomical footprint. The tunnel center was shifted from the anatomical position into a nonanatomical position in 3% (1/33) of the AM tunnel and 12.9% (4/31) of PL tunnel after tunnel widening. The tunnel location which shifted nonanatomically were relatively anterior and distal position.

CONCLUSIONS

Tunnel widening shifts the tunnel position to the anterior and distal direction, which could change the initial tunnel position. Nevertheless, the majority of tunnel positions remained in the anatomical position after tunnel widening and shifting.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Independent Versus Transtibial Drilling in Anterior Cruciate Ligament Reconstruction: A Meta-analysis With Meta-regression

Background:

Anterior cruciate ligament (ACL) reconstruction can be performed with different techniques for independent and transtibial (TT) drilling of femoral tunnels, but there is still no consensus on which approach leads to the best outcome.

Purpose:

To assess whether the independent or TT drilling approach for ACL reconstruction leads to the best functional outcomes.

Study Design:

Systematic review; Level of evidence, 2.

Methods:

A systematic literature search was conducted on July 1, 2020, using the PubMed, Web of Science, Cochrane Library, and Scopus databases. The influence of different femoral drilling techniques was analyzed through a meta-analysis in terms of patient-reported outcome measure scores, risk of complications, range of motion limitations, graft failure, and differential laxity. Subanalyses were performed to compare the different independent drilling techniques considered. Linear metaregression was performed to evaluate if the year of study publication influenced the results. The risk of bias and quality of evidence were assessed following the Cochrane guidelines.

Results:

A total of 22 randomized controlled trials including 1658 patients were included in the meta-analysis. Both International Knee Documentation Committee (IKDC) subjective score and Lysholm score were higher with the independent drilling approach (mean difference [MD], 1.24 [P = .02] and 0.55 [P = .005], respectively). No difference was documented in terms of the risk of reinjury, but independent drilling led to reduced KT-1000 arthrometer–assessed anterior tibial translation (MD, 0.23; P = .01) and a higher probability of a negative postoperative pivot-shift test finding (risk ratio, 1.13; P = .04). There were no significant differences in IKDC objective or Tegner scores. A P value of .07 was found for the association between the year of the study and IKDC objective scores.

Conclusion:

Independent femoral tunnel drilling provided better results than the TT approach, although the difference was not clinically significant. No difference was observed in the risk of reinjury. Increasingly better results were seen among surgical procedures performed in more recent years. Among the independent drilling options, the anteromedial portal technique seemed to provide the most favorable outcomes. The lack of clinically significant differences and the promising outcomes reported with new modified TT techniques suggest the importance of correct placement, rather than the tunnel drilling approach, to optimize the results of ACL reconstruction.

No differences in clinical outcomes and graft healing between anteromedial and central femoral tunnel placement after single bundle ACL reconstruction

PURPOSE

The purpose of this study was to compare clinical outcomes and graft healing after anterior cruciate ligament (ACL) reconstruction with anteromedial and central femoral tunnel placement.

METHODS

During 2016 and 2018, 110 consecutive patients underwent single bundle ACL reconstruction; 85 patients met the inclusion criteria, and each patient underwent 3D-CT within 1 week and MRI 1.5 years after the operation. The central point of the femoral tunnel and signal/noise quotient (SNQ) of three regions of interest (ROI) in the intra-articular graft were measured to analyse the tunnel position and graft healing extent. Clinical assessments, including functional scores, KT-2000 arthrometer measurements and pivot-shift tests, were evaluated at the 2-year follow-up. Patients were divided into two groups depending on the femoral tunnel position: the anteromedial position group (Group A) and the centre position group (Group B).

RESULTS

Seventy-one patients were available for the 2-year follow-up and MRI examination: 34 patients in Group A and 35 patients in Group B, and 2 patients were excluded for an eccentric tunnel position. No graft failure occurred, and compared with the preoperative assessment outcomes, the outcomes of both groups improved at the final follow-up. Group A was significantly better than Group B regarding the KT-2000 arthrometer measurements (P = 0.031). No significant differences were observed in terms of functional scores, pivot-shift test results, or the SNQ between groups.

CONCLUSIONS

No differences in clinical outcomes or graft healing were found between AM and central femoral tunnel placements in single bundle ACL reconstruction. Therefore, satisfactory clinical outcomes, knee stability and graft healing can be obtained for both femoral tunnel placements.

LEVEL OF EVIDENCE

II.

Creating a Femoral Tunnel Aperture at the Anteromedial Footprint Versus the Central Footprint in ACL Reconstruction: Comparison of Contact Stress Patterns

Background:

It remains unclear whether an anteromedial (AM) footprint or a central footprint anterior cruciate ligament (ACL) graft exhibits less contact stress with the femoral tunnel aperture. This contact stress can generate graft attrition forces, which can lead to potential graft failure.

Purpose/Hypothesis:

The purpose of this study was to compare the difference in contact stress patterns of the graft around a femoral tunnel that is created at the anatomic AM footprint versus the central footprint. It was hypothesized that the difference in femoral tunnel positions would influence the contact stress at the interface between the reconstructed graft and the femoral tunnel orifice.

Study Design:

Controlled laboratory study.

Methods:

A total of 24 patients who underwent anatomic single-bundle ACL reconstruction were included in this study. In 12 patients, the femoral tunnels were created at the center of the native AM footprint (AM group), and in the remaining 12 patients the center of the femoral tunnel was placed in the anatomic central footprint (central group). Three-dimensional knee models were created and manipulated using several modeling programs, and the graft-tunnel angle (GTA) was determined using a special software program. The peak contact stresses generated on the virtual ACL graft around the femoral tunnel orifice were calculated using a finite element method.

Results:

The mean GTA was significantly more obtuse in the AM group than in the central group (124.2° ± 5.9° vs 112.6° ± 7.9°; P = .001). In general, both groups showed high stress distribution on the anterior surface of the graft, which came in contact with the anterior aspect of the femoral tunnel aperture. The degree of stress in the central group (5.3 ± 2.6 MPa) was significantly higher than that in the AM group (1.2 ± 1.1 MPa) (P < .001).

Conclusion:

Compared with the AM footprint ACL graft, the central footprint ACL graft developed significantly higher contact stress in the extended position, especially around the anterior aspect of the femoral tunnel orifice.

Clinical Relevance:

The contact stress of the ACL graft at the extended position of the knee may be minimized by creating the femoral tunnel at the AM-oriented footprint.

Effect of Percentage of Femoral Anterior Cruciate Ligament Insertion Site Reconstructed With Hamstring Tendon on Knee Kinematics and Graft Force

BACKGROUND

Previous studies have stated that closely matching the size of the anterior cruciate ligament (ACL) insertion site footprint is important for biomechanical function and clinical stability after ACL reconstruction. However, the ACL varies widely regarding the area of femoral insertion, tibial insertion, and midsubstance of ACL, and reconstructing the insertion site area with a uniform diameter graft can result in a cross-sectional area that is greater than that of the midsubstance of the native ACL. Therefore, understanding the effect of relative graft size in ACL reconstruction on knee biomechanics is important for surgical planning.

PURPOSE

To assess how the percentage of femoral insertion site affects knee biomechanics in single- and double-bundle ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 14 human cadaveric knees were scanned with magnetic resonance imaging and tested using a robotic system under an anterior tibial load and a combined rotational load. In total, 7 knee states were evaluated: intact ACL; deficient ACL; single-bundle ACL reconstruction with approximate graft sizes 25% (small), 50% (medium), and 75% (large) of the femoral insertion site; and double-bundle reconstruction of approximately 50% (medium) and 75% (large) of the femoral insertion site, based on the ratio of the cross-sectional area of the graft to the area of the femoral ACL insertion site determined by magnetic resonance imaging.

RESULTS

Anterior tibial translation was not significantly larger than the intact state in single-bundle and double-bundle medium graft reconstructions (P > .05) and was significantly greater in the single-bundle small graft reconstruction (P < .05). Anterior knee translation in single-bundle medium graft and large graft reconstructions was not statistically different (P > .05). In contrast, the anterior tibial translation for double-bundle large graft reconstruction was significantly smaller than for double-bundle medium graft reconstruction at low flexion angles (P < .05). The single-bundle small graft force was significantly different from the intact ACL in situ force (P < .05). The graft force with double-bundle large reconstruction was significantly greater than that with the double-bundle medium reconstruction (P < .05) but was not significantly different from that of the intact ACL (P > .05).

CONCLUSION

Knee biomechanics with a single-bundle small graft tended to be significantly different from those of the intact knee. In the kinematic and kinetic data for the single- and double-bundle medium graft reconstruction, only the anterior translation at full extension for the single-bundle reconstruction was significantly different (lower) from that of intact knee. This was a time zero study.

CLINICAL RELEVANCE

This study can provide surgeons with guidance in selecting the graft size for ACL reconstruction.

Effectiveness of thicker hamstring or patella tendon grafts to reduce graft failure rate in anterior cruciate ligament reconstruction in young patients

PURPOSE

The purpose of this study was to determine the anterior cruciate ligament reconstruction (ACLR) failure rate in young patients utilizing the New Zealand (NZ) anterior cruciate ligament (ACL) Registry. The hypothesis was that the ACLR rupture rate would be lower for thicker hamstring graft and bone patellar tendon bone (BPB) grafts in comparison to the classic hamstring technique. The ACLR failure rate was assessed according to graft type and patients' sex.

METHODS

The NZ ACL registry was utilized to identify all patients aged 20 years or younger at the time of surgery who were skeletally mature and had a minimum 2-year follow-up. Graft ruptures, defined as an ACL revision, were identified according to graft type (traditional 4 strands hamstring semitendinosus and gracilis, 4 strands semitendinosus, 5-6 strands semitendinosus and gracilis, 7-8 strands semitendinosus and gracilis, bone-patella-bone graft).

RESULTS

Nine-hundred and ninety-two patients were included. At a mean follow-up of 38 months, 52 cases of graft rupture were recorded, (overall failure rate: 5.2%). The failure rate was not statistically influenced by the graft diameter. Patients with a thinner graft (< 8 mm-196 patients) had a similar failure rate (6%) to patients with a thicker graft (8 mm or more-485 patients) (6.2%). There was a lower failure rate in the BPB group (3.1%) versus all hamstrings group (6%) (ns). Finally, BPB in females had a lower failure rate than all hamstring constructs together (0% versus 5.1%; p = 0.023) CONCLUSION: In a young population traditional four-strand hamstring grafts, multiple strand configurations or BPB ACLR, whatever their size (> or < 8 mm), showed no significant difference in the failure rate in the NZ ACL registry. Female patients who had an ACL reconstruction with BPB graft had a significant lower failure rate than patients who had a hamstring graft.

LEVEL OF EVIDENCE

III.

Combination of anterior tibial and femoral tunnels makes the signal intensity of antero-medial graft higher in double-bundle anterior cruciate ligament reconstruction

PURPOSE

To elucidate whether sagittal graft tunnel affects the signal intensity in anatomical ACL reconstruction (ACLR) and to clarify the prevalence of intercondylar roof impingement. It was hypothesized that if the tunnel apertures are located within the anatomical footprint of ACL, tunnel position would not affect the signal intensity.

METHODS

A total of 132 patients who underwent anatomical double-bundle ACLR (DB-ACLR) using hamstring autograft were recruited. Tunnel position was determined by the quadrant method on three-dimensional computed tomography; the femoral tunnel position was defined as "high and low" or "deep and shallow", while that of the tibial side was defined as "anterior and posterior" or "medial and lateral". Subjects were divided into three groups according to the tertile of % deep-shallow. The signal intensity was evaluated by the region of interest value of the antero-medial bundle (AMB) and postero-lateral bundle on magnetic resonance imaging at 12 months after reconstruction. Linear regression analysis was conducted to elucidate the relationship between the percentage position of each tunnel and the graft signal intensity.

RESULTS

In the shallow tertile group, AMB signal intensity increased in the anterior position of the tibial tunnel (β = - 0.34; P = 0.025). In the intermediate and deep tertile groups, the tunnel position did not correlate with the signal intensity.

CONCLUSIONS

A more anterior tibial tunnel position increases AMB signal intensity in shallower femoral tunnel. Conversely, this correlation is attenuated for deeper femoral tunnels. Surgeons should pay attention to sagittal femoral tunnel position to create a more anterior tibial tunnel position.

LEVEL OF EVIDENCE

Level III.

How to Achieve an Accurate Anatomical Femoral Tunnel Technique in ACL Reconstruction in the Early Years of Your Consultancy? Femoral Offset Aimer Technique: Consistent and Reproducible Technique

Femoral tunnel malposition is the most common reason for failure of primary anterior cruciate ligament reconstruction. There are several methods to identify the anatomical location of femoral footprint. Femoral offset aimer technique is one such technique which is easy to use and reliable. It is an ideal technique for junior and inexperienced surgeons to recreate the femoral tunnel in its anatomical footprint. The senior author (P.E.) has been using this technique for 30 consecutive cases in his first year of independent practice during his consultancy without any major intraoperative complications. The author describes this technique in this article with tips and tricks which will especially guide the junior and inexperienced surgeons to avoid running into intraoperative problems while drilling the femoral tunnel.

Techniques for Femoral Socket Creation in ACL Reconstruction

Anterior cruciate ligament (ACL) injury is common and affects a wide variety of individuals. An ACL reconstruction is the treatment of choice for patients with subjective and objective symptoms of instability and is of particular importance to cutting or pivoting athletes. With many variables involved in ACL reconstruction, femoral tunnel placement has been found to affect clinical outcomes with nonanatomic placement being identified as the most common technical error. Traditionally the femoral tunnel was created through the tibial tunnel or transtibial with the use of a guide and a rigid reaming system. Because of proximal, nonanatomic tunnel placement using the transtibial technique, the use of the anteromedial portal and outside-in drilling techniques has allowed placement of the tunnel over the femoral footprint. In this paper, we discuss the difference between the 3 techniques and the advantages and disadvantages of each. The authors then explore the clinical differences and outcomes in techniques by reviewing the relevant literature.

The femoral posterior fan-like extension of the ACL insertion increases the failure load

PURPOSE

To examine the role of the posterior fan-like extension of the ACL's femoral footprint on the ACL failure load.

METHODS

Sixteen (n = 16) fresh frozen, mature porcine knees were used in this study and randomized into two groups (n = 8): intact femoral ACL insertion (ACL intact group) and cut posterior fan-like extension of the ACL (ACL cut group). In the ACL cut group, flexing the knees to 90°, created a folded border between the posterior fan-like extension and the midsubstance insertion of the femoral ACL footprint and the posterior fan-like extension was dissected and both areas were measured. Specimens were placed in a testing machine at 30° of flexion and subjected to anterior tibial loading (60 mm/min) until ACL failure.

RESULTS

The intact ACL group had a femoral insertion area of 182.1 ± 17.1 mm². In the ACL cut group, the midsubstance insertion area was 113.3 ± 16.6 mm², and the cut posterior fan-like extension portion area was 67.1 ± 8.3 mm². The failure load of the ACL intact group was 3599 ± 457 N and was significantly higher (p < 0.001) than the failure load of the ACL cut group 392 ± 83 N.

CONCLUSION

Transection of the posterior fan-like extension of the ACL femoral footprint has a significant effect on the failure load of the ligament during anterior loading at full extension. Regarding clinical relevance, this study suggests the importance of the posterior fan-like extension of the ACL footprint which potentially may be retained with remnant preservation during ACL reconstruction. Femoral insertion remnant preservation may allow incorporation of the fan-like structure into the graft increasing graft strength.

Anterior Cruciate Ligament Reconstruction Using a Ribbon-Like Graft With a C-Shaped Tibial Bone Tunnel

According to recent anatomic studies, the anterior cruciate ligament (ACL) appears to be a flat, "ribbon-like" structure, with a thin, oval-shaped insertion on the femur and a C-shaped tibial insertion. According to this anatomy, we describe an ACL-reconstruction technique that aims to approximate this natural anatomy. The basic principle of this technique is not to use conventional round tunnels but create tunnel shapes that resemble more closely the original ACL insertion sites. Using either a rectangular quadriceps tendon graft or a "flat" hamstring graft may not only provide a biomechanical advantage with increased rotational stability but also improve bone-tendon healing due to increased bone-tendon contact and decreased diffusion length. Creating a C-shaped tibial tunnel also avoids laceration of the anterior horn of the lateral meniscus, which is frequently harmed during conventional tibial tunnel drilling.

Functional Adaptation of the Fibrocartilage and Bony Trabeculae at the Attachment Sites of the Anterior Cruciate Ligament

The direct insertion of an enthesis is composed of uncalcified fibrocartilage (FC) and calcified FC, believed to function as buffers for multidirectional forces applied to the ligament. This study was performed to investigate the relationship between the FC thickness and bony trabecular orientation of the anterior cruciate ligament (ACL) on both the femoral and tibial sides. Six cadavers were examined (age at death: 73-92 years). Both femoral and tibial insertions of the ACL were harvested and used to make 0.5 mm interval semi-serial sections. Microdigital images were taken and used to measure the maximum thickness of both the uncalcified FC and Calcified FC. Two-dimensional discrete Fourier analysis was also performed to determine the orientation angle and orientation intensity of bony trabeculae directly under the FC. The mean thicknesses of the uncalcified FC at the femoral and tibial insertions were 0.98 mm and 0.49 mm, respectively. The mean thicknesses of the calcified FC were 0.47 mm and 0.38 mm, respectively. There was a significant difference in the uncalcified FC thickness, but not in the calcified FC thickness. The bony trabeculae showed a prominent orientation parallel to the ACL fiber on both sides, but it was more intense on the tibial side than on the femoral side. The trabecular orientation was prominent in the proximal-posterior part of the femoral side and in the anteromedial part of the tibial side, suggesting that mechanical stress is greater in these parts. The dominant bony trabecular angle was 69.0° on the femoral side and 59.8° on the tibial side when the tidemark was set at 0°. These findings suggest that the femoral side receives multidirectional stresses, while relatively unidirectional stress is loaded on the tibial side. Furthermore, stress is considered to be greater in the proximal-posterior part of the femoral insertion and in the anteromedial part of the tibial insertion. At the time of ACL reconstruction, attention should be paid to assign a robust portion of the graft to the posterior part of the femoral insertion and anteromedial part of the tibial insertion. Clin. Anat., 33:988-996, 2020. © 2019 Wiley Periodicals, Inc.

In vivo attachment site to attachment site length and strain of the ACL and its bundles during the full gait cycle measured by MRI and high-speed biplanar radiography

The purpose of this study was to measure in vivo attachment site to attachment site lengths and strains of the anterior cruciate ligament (ACL) and its bundles throughout a full cycle of treadmill gait. To obtain these measurements, models of the femur, tibia, and associated ACL attachment sites were created from magnetic resonance (MR) images in 10 healthy subjects. ACL attachment sites were subdivided into anteromedial (AM) and posterolateral (PL) bundles. High-speed biplanar radiographs were obtained as subjects ambulated at 1 m/s. The bone models were registered to the radiographs, thereby reproducing the in vivo positions of the bones and ACL attachment sites throughout gait. The lengths of the ACL and both bundles were estimated as straight line distances between attachment sites for each knee position. Increased attachment to attachment ACL length and strain were observed during midstance (length = 28.5 ± 2.6 mm, strain = 5 ± 4%, mean ± standard deviation), and heel strike (length = 30.5 ± 3.0 mm, strain = 12 ± 5%) when the knee was positioned at low flexion angles. Significant inverse correlations were observed between mean attachment to attachment ACL lengths and flexion (rho = -0.87, p < 0.001), as well as both bundle lengths and flexion (rho = -0.86, p < 0.001 and rho = -0.82, p < 0.001, respectively). AM and PL bundle attachment to attachment lengths were highly correlated throughout treadmill gait (rho = 0.90, p < 0.001). These data can provide valuable information to inform design criteria for ACL grafts used in reconstructive surgery, and may be useful in the design of rehabilitation and injury prevention protocols.

Tunnel placement in ACL reconstruction surgery: smaller inter-tunnel angles and higher peak forces at the femoral tunnel using anteromedial portal femoral drilling-a 3D and finite element analysis

PURPOSE

Recent studies have emphasized the importance of anatomical ACL reconstruction to restore normal knee kinematics and stability. Aim of this study is to evaluate and compare the ability of the anteromedial (AM) and transtibial (TT) techniques for ACL reconstruction to achieve anatomical placement of the femoral and tibial tunnel within the native ACL footprint and to determine forces within the graft during functional motion. As the AM technique is nowadays the technique of choice, the hypothesis is that there are significant differences in tunnel features, reaction forces and/or moments within the graft when compared to the TT technique.

METHODS

Twenty ACL-deficient patients were allocated to reconstruction surgery with one of both techniques. Postoperatively, all patients underwent a computed tomography scan (CT) allowing 3D reconstruction to analyze tunnel geometry and tunnel placement within the native ACL footprint. A patient-specific finite element analysis (FEA) was conducted to determine reaction forces and moments within the graft during antero-posterior translation and pivot-shift motion.

RESULTS

With significantly shorter femoral tunnels (p < 0.001) and a smaller inter-tunnel angle (p < 0.001), the AM technique places tunnels with less variance, close to the anatomical centre of the ACL footprints when compared to the TT technique. Using the latter, tibial tunnels were more medialised (p = 0.007) with a higher position of the femoral tunnels (p = 0.02). FEA showed the occurrence of higher, but non-significant, reaction forces in the graft, especially on the femoral side and lower, however, statistically not significant, reaction moments using the AM technique.

CONCLUSION

This study indicates important, technique-dependent differences in tunnel features with changes in reaction forces and moments within the graft.

LEVEL OF EVIDENCE

II.

Femoral tunnel placement in single-bundle, remnant-preserving anterior cruciate ligament reconstruction using a posterior trans-septal portal

BACKGROUND

Anatomic tunnel formation and remnant preservation are valuable aspects of anterior cruciate ligament (ACL) reconstruction. However, anatomic landmarks are difficult to observe during remnant-preserving ACL reconstruction (ACLR). The aims of this study were to evaluate the: 1) femoral tunnel location created with guidance from the apex of the deep cartilage margin (ADC) and footprint compared to anatomical reference; and 2) relationship between femoral tunnel location and outcomes of ACLR.

METHODS

A total of 109 ACLR patients without revision ACLR, multi-ligament reconstruction, peri-knee fracture, and osteotomy were included. The femoral tunnel was formed at the most proximal corner of the femoral footprint using a posterior trans-septal portal as the viewing portal. The distance from the tunnel center to ADC was measured by computed tomography and arthroscopy. The two measurements were then compared. Finally, femoral tunnel location was compared to the anatomic reference and correlated with the outcomes.

RESULTS

The average distance from ADC to the femoral tunnel center was 7.0 ± 1.4 mm as measured by arthroscopy, and 7.2 ± 2.0 mm using three-dimensional computed tomography. There was no statistically significant difference between the two methods (P = 0.420). Clinical and stability outcomes were significantly improved postoperatively. Clinical outcome was not related to femoral tunnel location; however, stability outcome was related to femoral tunnel location: the more proximally located femoral tunnels showed better stability.

CONCLUSION

The ADC can be a possible landmark in remnant-preserving ACLR using a trans-septal portal. A more proximal femoral tunnel, which is located at the proximal corner of the ACL remnant, can provide stability advantage during remnant-preserving ACLR.

Proximal fixation anterior to the lateral femoral epicondyle optimizes isometry in anterolateral ligament reconstruction

PURPOSE

Concomitant anterolateral ligament (ALL) injury is often observed in patients with an anterior cruciate ligament injury leading some to recommend concurrent ALL reconstruction. In ligament reconstruction, it is imperative to restore desirable ligament length changes to prevent stress on the graft. The purpose of this investigation is to identify the optimal femoral and tibial locations for fixation in ALL reconstruction.

METHODS

3D computerized tomography (CT) knee models were obtained from six fresh-frozen, unpaired, cadaveric human knees at 0°, 10°, 20°, 30°, 40°, 90°, 110°, and 125°of knee flexion. Planar grids were projected onto the lateral knee. Isometry between each tibial and femoral grid point was calculated at each angle of flexion by the length change in reference to the length at 0° of knee flexion. The mean normalized length change over the range of motion was calculated for each combination of points at all angles of flexion were calculated.

RESULTS

Fixation of the ALL to the lateral femoral epicondyle or 5 mm anterior to the epicondyle with tibial fixation on the posteroinferior aspect of the tibial condyle (14-21 mm posterior to Gerdy's tubercle and 13-20 mm below the joint line) provided the lowest average length change for all possible ALL tibial insertion points. Minimal length change for all femoral fixation locations occurred from 20° to 40° of flexion, which identifies the angle of flexion where graft tensioning should occur intraoperatively.

CONCLUSION

With the use of 3D reconstructed models of knee-CT scans, we observed that there was no ALL fixation point that was truly isometric throughout range of motion. Fixation of the anterolateral ligament on the lateral femoral epicondyle or anterior to the lateral femoral epicondyle and on the inferoposterior aspect of the tibial condyle restores isometry. Additionally, minimal length change was observed between 20° and 40° of flexion, which is the most appropriate range of knee flexion to tension the graft. Reproducing isometry reduces stress on the graft, which minimizes the risk of graft failure.

Transportal central femoral tunnel placement has a significantly higher revision rate than transtibial AM femoral tunnel placement in hamstring ACL reconstruction

PURPOSE

It is proposed that central femoral ACL graft placement better controls rotational stability. This study evaluates the consequence of changing the femoral tunnel position from the AM position drilled transtibially to the central position drilled transportally. The difference in ACL graft failure is reported.

METHODS

This prospective consecutive patient single surgeon study compares the revision rates of 1016 transtibial hamstring ACL reconstructions followed for 6-15 years with 464 transportal hamstring ACL reconstructions followed for 2-6 years. Sex, age, graft size, time to surgery, meniscal repair and meniscectomy data were evaluated as contributing factors for ACL graft failure to enable a multivariate analysis. To adjust for the variable follow-up a multivariate hazard ratio, failure per 100 graft years and Kaplan-Meier survivorship was determined.

RESULTS

With transtibial ACLR 52/1016 failed (5.1%). With transportal ACLR 32/464 failed (6.9%). Significant differences between transportal and transtibial ACLR were seen for graft diameter, time to surgery, medial meniscal repair rates and meniscal tissue remaining after meniscectomy. Adjusting for these the multivariate hazard ratio was 2.3 times higher in the transportal group (p = 0.001). Central tunnel placement resulted in a significantly 3.5 times higher revision rate compared to an anteromedial tunnel placement per 100 graft years (p = 0.001). Five year survival was 980/1016 (96.5%) for transtibial versus 119/131 (90.5%) for transportal. Transportal ACLR also showed a significantly higher earlier failure rate with 20/32 (61%) of the transportal failing in the first year compared with 14/52 (27%) for transtibial. (p = 0.001.) CONCLUSION: Transportal central femoral tunnel ACLR has a higher failure rate and earlier failure than transtibial AM femoral tunnel ACLR.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

Positioning of the femoral tunnel in anterior cruciate ligament reconstruction: functional anatomical reconstruction

The aim of this study was to review and update the literature in regard to the anatomy of the femoral origin of the ACL, the concept of the double band and its respective mechanical functions, and the concept of direct and indirect fibres in the ACL insertion. These topics will be used to help determine which might be the best place to position the femoral tunnel and how this should be achieved, based on the idea of functional positioning, that is, where the most important ACL fibres in terms of knee stability are positioned. Low positioning of the femoral tunnel, reproducing more of the posterolateral band, and positioning the tunnel away from the lateral intercondylar ridge, that is, in the indirect fibres, would theoretically rebuild a ligament that is less effective in relation to knee stability. The techniques described to determine the femoral tunnel's centre point all involve some degree of subjectivity; the point is defined manually and depends on the surgeon's expertise. The centre of the ACL insertion in the femur should be used as a parameter. Once the centre of the ligament in its footprint is marked, the centre of the tunnel must be defined, drawing the marking toward the intercondylar ridge and anteromedial band. This will allow the femoral tunnel to occupy the region containing the most important original ACL fibres in terms of this ligament's function.

No difference in the graft shift between a round and a rounded rectangular femoral tunnel for anterior cruciate ligament reconstruction: an experimental study

INTRODUCTION

We developed a novel technique of creating a rounded rectangular femoral bone tunnel for anatomical, single-bundle, autologous hamstring tendon anterior cruciate ligament (ACL) reconstruction. Although this tunnel has many advantages, its non-circular shape has raised concerns regarding excessive graft shift within the bone tunnel. This study aimed to compare the graft shift between round and rounded rectangular tunnels using a graft diameter tester for simulating the femoral bone tunnel.

MATERIALS AND METHODS

Seven semitendinosus tendon grafts harvested from fresh-frozen cadavers were prepared by removing all excess soft tissue. The two ends of a double-fold hamstring tendon were sutured using a baseball stitch and then looped over a TightRope (Arthrex Co., Ltd., Naples, Florida, USA) to make a fourfold graft. The diameter of the graft was standardized to 8 mm using a round graft diameter tester. A round and an original rounded rectangular graft diameter tester were used for simulating the respective femoral bone tunnels. The graft was inserted into the tunnel, with the TightRope positioned on the outside of the tunnel. The distal end of the graft was tensioned to 40 N at an angle of 75° to reproduce the most severe graft bending angle. Digital photographs of the tunnel aperture taken at each simulated tunnel and the range of graft shift in the simulated tunnel were analyzed by ImageJ software. Statistical analyses were performed using the Tukey test. P < 0.05 was considered to be significant.

RESULTS

There were no significant differences between the round and the rounded rectangular tunnel groups (P > 0.05) in terms of graft shift, gap area, and graft shift ratio.

CONCLUSION

In a simulated ACL reconstruction, there is no difference in the graft shift between a round and a rounded rectangular bone tunnel.

Dynamic 3-Dimensional Mapping of Isometric Anterior Cruciate Ligament Attachment Sites on the Tibia and Femur: Is Anatomic Also Isometric?

PURPOSE

The purpose of this study was to (1) map the length changes of the medial wall of the lateral femoral condyle (MWLFC) with respect to various points about the tibial anterior cruciate ligament (ACL) footprint to determine the area that demonstrates the least amount of length change through full range of motion and (2) to identify a range of flexion that would be favorable for graft tensioning.

METHODS

Six fresh-frozen cadaveric knees were obtained from screened individuals with no prior history of arthritis, cancer, surgery, or any ligamentous knee injury. For each knee, 3-dimensional computed tomography point-cloud models were obtained in succession from 0° to 135°. A point grid was placed on the MWLFC and the tibia. Intra-articular length was calculated for each point on the femur to the tibia at all flexion angles and grouped to represent areas for bone tunnels. Normalized length changes were compared.

RESULTS

Areas anterior/distal on the MWLFC increased with increasing flexion, and areas proximal/posterior decreased with increasing flexion. The area about the intersection of the lateral intercondylar ridge and the bifurcate ridge was most isometric throughout flexion as no significant change in ligament length was found throughout flexion. The normalized length changes from the central position of the tibia showed no significant difference compared with the anterior or posterior tibial position.

CONCLUSIONS

No area of the MWLFC is truly isometric through flexion. Femoral tunnel placement slightly anterior to the center of the anteromedial and posterolateral bundles was most isometric. Minimal length change occurs between 10° and 40°, which reflects the range where graft tensioning was most often performed. The results of this study provide further support for an anatomic ACL reconstruction. CLINICAL RELEVANCE: The femoral tunnel location for ACL reconstruction with the least amount of length change through range of motion should encompass the direct fibers of the ACL.

Arthroscopic primary repair of the anterior cruciate ligament: what the radiologist needs to know

Recently, there has been a renewed interest in primary repair of proximal anterior cruciate ligament (ACL) tears. Magnetic resonance imaging (MRI) plays an important role in preoperative patient selection and in postoperative ligament assessment. Knowledge of the imaging factors that make patients candidates for primary ACL repair, namely proximal tear location and good tissue quality, can help radiologists provide information that is meaningful for surgical decision making. Furthermore, an understanding of the surgical techniques can prevent misinterpretation of the postoperative MRI. This article reviews preoperative MRI characterization of ACL injuries, techniques of arthroscopic primary ACL repair surgery and examples of postoperative MRI findings.

An In Vivo Prediction of Anisometry and Strain in Anterior Cruciate Ligament Reconstruction - A Combined Magnetic Resonance and Dual Fluoroscopic Imaging Analysis

PURPOSE

To evaluate the in vivo anisometry and strain of theoretical anterior cruciate ligament (ACL) grafts in the healthy knee using various socket locations on both the femur and tibia.

METHODS

Eighteen healthy knees were imaged using magnetic resonance imaging and dual fluoroscopic imaging techniques during a step-up and sit-to-stand motion. The anisometry of the medial aspect of the lateral femoral condyle was mapped using 144 theoretical socket positions connected to an anteromedial, central, and posterolateral attachment site on the tibia. The 3-dimensional wrapping paths of each theoretical graft were measured. Comparisons were made between the anatomic, over the top (OTT), and most-isometric (isometric) femoral socket locations, as well as between tibial insertions.

RESULTS

The area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. The most isometric attachment site was found midway on the Blumensaat line with approximately 2% and 6% strain during the step-up and sit-to-stand motion, respectively. Posterior femoral attachments resulted in decreased graft lengths with increasing flexion angles, whereas anterodistal attachments yielded increased lengths with increasing flexion angles. The anisometry of the anatomic, OTT and isometric grafts varied between tibial insertions (P < .001). The anatomic graft was significantly more anisometric than the OTT and isometric graft at deeper flexion angles (P < .001).

CONCLUSIONS

An area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. ACL reconstruction at the isometric and OTT location resulted in nonanatomic graft behavior, which could overconstrain the knee at deeper flexion angles. Tibial location significantly affected graft strains for the anatomic, OTT, and isometric socket location. CLINICAL RELEVANCE: This study improves the knowledge on ACL anisometry and strain and helps surgeons to better understand the consequences of socket positioning during intra-articular ACL reconstruction.

Loss of Internal Tibial Rotation After Anterior Cruciate Ligament Reconstruction

The flexion angle of the knee and the position of the tibia need to be considered during tensioning of the anterior cruciate ligament (ACL) graft to avoid overconstraining the knee. The purpose of this report was to describe 2 cases of loss of tibial internal rotation after single-bundle anatomic ACL reconstruction with graft tensioning in flexion. Retrospective review of each patient's operative chart revealed that the graft was tensioned in flexion and placed in an anatomic position in the femoral tunnel at the time of the index operation. Primary outcome was ACL revision surgery. Secondary outcome data included Lysholm scores and Lachman and pivot shift tests. Two patients underwent revision ACL reconstruction with a more vertical tunnel placed through a transtibial technique. The graft was tensioned in full knee extension and neutral rotation of the tibia. This resulted in restoration of normal tibial internal rotation to 10°. Lysholm scores improved from 35 to 90 in patient 1 and from 12 to 61 in patient 2. Patient 1 returned to college soccer at 6 months postoperatively. Her knee was stable to Lachman and pivot shift tests. Patient 2 has been followed for 12 months and has returned to all normal activities without pain or dysfunction. Anatomic femoral placement of the ACL with improper positioning of the knee during tensioning of the graft may capture the knee and lead to loss of the normal internal rotation. The surgeon should be aware of this complication during primary ACL reconstruction. [Orthopedics. 2018; 41(1):e22-e26.].

Transtibial Versus Anteromedial Portal ACL Reconstruction: Is a Hybrid Approach the Best?

BACKGROUND

Improved biomechanical and clinical outcomes are seen when the femoral tunnels of the anterior cruciate ligament (ACL) are placed in the center of the femoral insertion. The transtibial (TT) technique has been shown to be less capable of this than an anteromedial (AM) portal approach but is more familiar to surgeons and less technically challenging. A hybrid transtibial (HTT) technique using medial portal guidance of a transtibial guide wire without knee hyperflexion may offer anatomic tunnel placement while maintaining the relative ease of a TT technique.

PURPOSE

To evaluate the anatomic and biomechanical performance of the HTT technique compared with TT and AM approaches.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-six paired, fresh-frozen human knees were used. Twenty-four knees (12 pairs) underwent all 3 techniques (TT, AM, HTT) for femoral tunnel placement, with direct measurement of femoral insertional overlap and femoral tunnel length. The remaining 12 knees (6 pairs) underwent completed reconstructions to evaluate graft anisometry and tunnel orientation, with each technique performed in 4 specimens and tested using motion sensors with a quad-load induced model. Graft length changes and graft/femoral tunnel angle were measured at varying degrees of flexion.

RESULTS

Percentage overlap of the femoral insertion averaged 37.0% ± 28.6% for TT, 93.9% ± 5.6% for HTT, and 79.7% ± 7.7% for AM, with HTT significantly greater than both TT (P = .007) and AM (P = .001) approaches. Graft length change during knee flexion (anisometry) was 30.1% for HTT, 12.8% for AM, and 8.5% for TT. When compared with the TT approach, HTT constructs exhibited comparable graft-femoral tunnel angulation (TT, 150° ± 3° vs HTT, 142° ± 2.3°; P < .001) and length (TT, 42.6 ± 2.8 mm vs HTT, 38.5 ± 2.0 mm; P = .12), while AM portal tunnels were significantly shorter (31.6 ± 1.6 mm; P = .001) and more angulated (121° ± 6.5°; P < .001).

CONCLUSION

The HTT technique avoids hyperflexion and maintains femoral tunnel orientation and length, similar to the TT technique, but simultaneously achieves anatomic graft positioning.

CLINICAL RELEVANCE

The HTT technique offers an anatomic alternative to an AM portal approach while maintaining the technical advantages of a traditional TT reconstruction.

Anterior Cruciate Ligament Injury, Reconstruction, and the Optimization of Outcome

Anterior cruciate ligament reconstruction (ACLR) provides an established surgical intervention to control pathological tibiofemoral translational and rotational movement. ACLR is a safe and reproducible intervention, but there remains an underlying rate of failure to return to preinjury sporting activity levels. Postoperative pathological laxity and graft reinjury remain concerns. Previously, unrecognized meniscal lesions, disruption of the lateral capsule, and extracapsular structures offer potential avenues to treat and to therefore improve kinematic outcome and functional results, following reconstruction. Addressing laterally based injuries may also improve the durability of intraarticular ACLR. Improving the anterior cruciate ligament (ACL) graft replication of the normal ACL attachment points on the femur and the tibia, using either double bundle or anatomical single bundle techniques, improves kinematics, which may benefit outcome and functionality, following reconstruction.