Anterior Cruciate Ligament Footprint Research Articles

Variations in sagittal locations of anterior cruciate ligament tibial footprints and their association with radiographic landmarks: a human cadaveric study

BackgroundThis cadaveric study aimed to demonstrate variation of the anterior cruciate ligament (ACL) tibial attachment in the sagittal plane, and to analyze the radiographic landmarks which predict the sagittal location of the ACL tibial attachment.MethodsIn 20 cadaveric knees, native ACLs were removed and the centers of the ACL tibial and femoral attachments were marked with metal pins. Full extension lateral radiographs were then obtained in each cadaveric knee. Using the full extension lateral radiographs, the sagittal location of the ACL tibial footprint center was estimated as a percentage in the Amis and Jakob’s line. Several radiographic landmarks including the geometry of Blumensaat’s line and the apex of the tibial eminence were measured. Then, the relationship between the variation of the sagittal location of the ACL tibial footprint and several radiographic landmarks were analyzed using Pearson’s correlation analysis.ResultsThe average sagittal position of the native ACL tibial footprint was 40.9% (range: 38.0–45.0%). The line connecting the centers of the ACL footprint was nearly parallel to Blumensaat’s line, with an average angle of 1.7° (range: 0–4.1°). In addition, the distance from the point where Blumensaat’s line meets the tibial articular surface to the center of the ACL tibial footprint was almost consistent, at 7.6 mm on average (range: 6.4–8.7 mm). The correlation analysis revealed that the geometry of Blumensaat’s line was significantly correlated with the sagittal location of the ACL tibial footprint.ConclusionThe radiographic landmark that showed a significant correlation with the ACL tibial footprint in the full extension lateral radiographs was Blumensaat’s line.

Transportal Anterior Cruciate Ligament Reconstruction with Quadrupled Hamstring Tendon Graft: A Prospective Outcome Study.

Background:Anterior cruciate ligament (ACL) reconstruction has been one of the most commonly performed procedures throughout the world. Unsatisfactory outcome with conventional ACL reconstruction has been attributed to nonanatomic graft placement. Researchers have advised placing the graft in the native footprint of ACL to avoid nonanatomic graft placement. The goal of this study was to analyze the outcome of anatomic single bundle ACL reconstruction using transportal technique.Materials and Methods:This was a prospective outcome study conducted on 85 consecutive patients of ACL reconstruction of which 62 patients met inclusion and exclusion criteria and were analyzed for final results. All the patients underwent ACL reconstruction by quadrupled hamstring tendon graft using transportal technique and the accessory anteromedial (AAM) portal for femoral tunnel creation. The graft was fixed with endobutton on femoral side and bioabsorbable screw on the tibial side. Patients were evaluated for range of motion, International Knee Documentation Committee (IKDC) score, and Lysholm scores at a minimum followup period of 2 years. The mean pre- and postoperative scores were compared using Wilcoxon signed-rank test.Results:The mean Lysholm and IKDC scores improved significantly (P < 0.0001) from preoperative value. According to IKDC score, 90.3% (n = 56) were either normal or near normal at final followup. According to Lysholm score, 75.8% of patients had excellent and 13.3% had good results. Preoperatively, pivot shift was present in 85.5% (n = 53) of patients which reduced to 4.8% (n = 3) postoperatively. Infection and knee stiffness occurred in two patients, and femoral tunnel blowout and graft re-rupture occurred in one patient each.Conclusion:Anatomic ACL reconstruction by AAM portal is a reproducible technique which gives good clinical outcome at short-term followup.

Comparison of the Accuracy and Reproducibility of the Femoral Tunnel Location Between Anterior and Posterior Viewing During Outside-In Anterior Cruciate Ligament Reconstruction

Accuracy and reproducibility of the femoral tunnel location could be improved with a TS portal viewing using a 30° arthroscope. During outside-in anterior cruciate ligament (ACL) reconstruction, anteromedial (AM) or anterolateral (AL) portals are usually used for the viewing of the femoral foot print. However, observing the posterior portion of the ACL femoral foot print (AM bundle footprint) using an AM or AL portal could be difficult due to blocking by remnant ACL or ridge on the medial wall of the lateral femoral condyle. In this view point, using a 70° arthroscope through posterolateral (PL) portal, posterior part of the ACL footprint could be seen directly. However, this view could be a little distorted because the wall of the ACL insertion should be seen from posterior to anterior direction. The posterior trans-septal portal (TS) could allow direct visual access to the posterior part of the ACL femoral footprint through the posteromedial (PM) portal. The purpose of this study was to compare the accuracy and reproducibility of the femoral tunnel location between three different viewing techniques (observed through an AL or AM portal using a 30° arthroscope (A group) vs. PL portal using a 70° arthroscope (PL group) vs. TS portal using a 30° arthroscope (TS group) by 3D CT in outside-in ACL reconstruction. The hypothesis of this study was that femoral tunnel locations would be more accurate and reproducible in the posterior viewing group (PL and TS), and the TS viewing technique would be the best because it offers the most direct view of the medial wall of the lateral femoral condyle. One-hundred and six outside-in ACL constructions patients were recruited. Patients were divided into three groups according to the viewing techniques (36 A vs. 35 PL vs. 35 TS patients). Femoral tunnel locations were evaluated with a quadrant method and anatomic coordinate axes measurement (ACAM) method in the medial wall of the lateral femoral condyle using 3D reconstructed CT. The accuracy and reproducibility of the femoral tunnel locations were compared between three techniques. The accuracy of the tunnel location was higher in the TS group by the quadrant method (A group vs. TS group: p<0.001, PL group vs. TS group: p<0.001) as well as the ACAM (A group vs. TS group: p<0.001, PL group vs. TS group: p=0.02). The reproducibility of the femoral tunnel position in the TS group was the highest and femoral tunnel locations of the TS group were more compactly distributed compared with those of the A and PL group (standard deviation: A group [4.68%], PL group [3.75%], and TS group [1.34%] by the quadrant method; A group [5.18%], PL group [3.85%], and TS group [1.92%] by the ACAM method). Accuracy and reproducibility of the femoral tunnel location could be improved with a TS portal viewing using a 30° arthroscope and anterior and PL portal viewing using a 70° arthroscope showed no difference.

No clinical differences between anteromedial portal and transtibial technique for femoral tunnel positioning in anterior cruciate ligament reconstruction: a prospective randomized, controlled trial.

The anteromedial (AMP) portal technique was introduced to position the femoral tunnel in anterior cruciate ligament (ACL) reconstruction to more closely replicate the original ACL footprint compared to the transtibial (TT) approach. Few randomized trials have evaluated differences in these techniques with respect to clinical outcomes. The purpose of this study was to determine if there are any differences in clinical outcome between the AMP and TT approaches. This is a single-blinded, prospective, randomized controlled trial. Participants were randomized to undergo ACL reconstruction using the AMP or TT approach. The primary outcome measure was the ACL quality of life (ACL-QOL), and secondary outcomes were the IKDC knee assessment, side-to-side difference in anterior-posterior knee laxity (KT-1000) and tunnel orientation (X-ray findings) at preoperative, 3, 6, 12, and 24months postoperative. Statistical comparisons were performed using a series of t tests for independent groups with equal variance. Ninety-six participants were consented and randomized between 2007 and 2011 with eight excluded postrandomization. Mean (SD) preoperative ACL-QOL was 33 (13) for TT and 36 (17) for AMP and improved significantly (p<0.001) in both groups to 79 (18) and 78 (18) at 24months postoperative, respectively. The preoperative median IKDC grade for both groups was C and improved similarly in both groups at 24months (n.s.). There was no side-to-side difference in knee laxity based on KT-1000 measurements with a mean (SD) 1 (3) mm between affected and unaffected limbs in the TT group compared to 1 (3) mm for the AMP group. A significant difference was found in femoral tunnel orientation with the AMP group at 43° (7) and the TT group 58° (8) in the coronal plane (p<0.001). No differences in clinical outcome were found when comparing AMP to TT in primary ACL reconstruction using a STG graft. This prospective randomized controlled trial suggests surgeons can use either method without significantly compromising clinical outcome. I.

Anatomic Anterior Cruciate Ligament Reconstruction - A Prospective Evaluation Using Three-Dimensional Magnetic Resonance Imaging

Objectives:The recent emphasis on anatomic reconstruction of the anterior cruciate ligament (ACL) is well supported by clinical and biomechanical research. Unfortunately, the location of the native femoral footprint can be difficult or even impossible to see at the time of surgery. Most surgeons therefore rely on anatomic landmarks, custom drill guides, or general rules-of-thumb to guide femoral tunnel placement; however, the accuracy of these techniques to reconstruct each patient’s native anatomy is poorly understood. The objective of this study was to use a previously described isotropic magnetic resonance sequence (3D MRI) to image patients with torn ACLs before and after reconstruction and thereby assess the accuracy of graft position on the femoral condyle in comparison to each patient’s native ACL footprint.Methods:Forty-one patients with unilateral ACL tears were prospectively recruited into our study. Each patient underwent a 3D MRI of both the injured and uninjured knees before surgery. The contralateral (uninjured) knee scan was used to define the patient’s native footprint. Patients then underwent ACL reconstruction with hamstring autograft by one of four experienced fellowship-trained sports orthopedic surgeons. The injured knee was reimaged after surgery. The location and percent overlap of the reconstructed femoral footprint was compared to the patient’s native footprint.Results:The center of the native ACL femoral footprint was a mean of 16.4 +/- 4.6 mm distal and 5.3 +/- 2.9 mm anterior to the apex of the deep cartilage. The position of the reconstructed graft was significantly different, with mean distance of 10.4 +/- 2.7 mm distal (P < 0.0001) and 7.7 +/- 3.1 mm anterior (P = 0.001). The mean distance between the center of the graft and the center of the native ACL femoral footprint (error distance) was 5.7 +/- 3.6 mm. Comparing error distances amongst the four surgeons demonstrated no significant difference using the Kruskal-Wallis one-way ANOVA (P = 0.78). On average, 21% of the graft was within the native ACL femoral footprint. Of the 41 patients, 16 (39%) had the graft placed entirely outside the native ACL footprint.Conclusion:Despite contemporary techniques and a concerted effort to perform anatomic ACL reconstructions by four experienced sports orthopedic surgeons, the position of the femoral footprint was significantly different between the native and reconstructed ligaments. Furthermore, each of the four surgeons uses a different technique but all had comparable errors in their tunnel placements. In order to achieve a truly anatomic reconstruction, surgeons may consider using a pre-operative 3D MRI, which enables excellent visualization of the ACL’s native anatomy and could potentially be used as a roadmap to guide anatomic tunnel placement.

Anterior cruciate ligament tibial insertion site is elliptical or triangular shaped in healthy young adults: high-resolution 3-T MRI analysis.

To clarify the morphology of anterior cruciate ligament (ACL) tibial insertion site in healthy young knees using high-resolution 3-T MRI. Subjects were 50 ACL-reconstructed patients with a mean age of 21.4±6.8years. The contralateral healthy knees were scanned using high-resolution 3-T MRI. The tibial insertion sites of the anteromedial (AM) and posterolateral (PL) bundle fibres, and the ACL attachment on the anterior horn of lateral meniscus (AHLM) were segmented from the MR images, and 3D models were reconstructed to evaluate the morphology. The shape of ACL footprint was qualitatively analysed, and the size of AM and PL attachments and AHLM overlapped area was measured digitally. Tibial AM and PL bundles were clearly identified in 42 of 50 knees (84.0%). Morphology of the whole ACL tibial insertion site was elliptical in 23 knees (54.8%) and triangular in 19 knees (45.2%), but not classified as C-shape in any knees. However, the AM bundle attachment was of C-shape in 29 knees (69.0%) and band-like in 13 knees (31.0%). Overlap of ACL on AHLM was found in 26 knees (61.9%), and the size of the overlapped area was 4.8±4.7% of the whole ACL insertion site. 3D morphology of the intact ACL tibial insertion site analysed by high-resolution 3-T MRI was elliptical or triangular in healthy young knees. However, the AM bundle insertion site was of C-shape or band-like. A small lateral portion of the ACL was overlapped with the AHLM. As for clinical relevance, these findings should be considered in order to reproduce the native ACL insertion site sufficiently. III.

Morphological size evaluation of the mid-substance insertion areas and the fan-like extension fibers in the femoral ACL footprint.

The purpose of this study was to evaluate the detailed anatomy of the femoral anterior cruciate ligament (ACL) insertion site, with special attention given to the morphology of the mid-substance insertion areas and the fan-like extension fibers. Twenty-three non-paired human cadaver knees were used (7 Males, 16 Females, median age 83, range 69-96). All soft tissues around the knee were resected except the ligaments. The ACL was divided into antero-medial (AM) and postero-lateral (PL) bundles according to the difference in macroscopic tension patterns. The ACL was carefully dissected and two outlines were made of the periphery of each bundle insertion site: those which included and those which excluded the fan-like extension fibers. An accurate lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The area of each bundle, including and excluding the fan-like extension fibers, was measured with Image J software (National Institution of Health). The width and length of the mid-substance insertion sites were also evaluated using same image. The femoral ACL footprint was divided into four regions (mid-substance insertion sites of the AM and PL bundles, and fan-like extensions of the AM and PL bundles). The measured areas of the mid-substance insertion sites of the AM and PL bundles were 35.5±12.5, and 32.4±13.8mm2, respectively. Whole width and length of the mid-substance insertion sites were 5.3±1.4, and 15.5±2.9mm, respectively. The measured areas of the fan-like extensions of the AM and PL bundles were 27±11.5, and 29.5±12.4mm2, respectively. The femoral ACL footprint was divided into quarters of approximately equal size (mid-substance insertion sites of the AM and PL bundles, and fan-like extensions of the AM and PL bundles). For clinical relevance, to perform highly reproducible anatomical ACL reconstruction, the presence of the fan-like extension fibers should be taken into consideration.

Combined Anatomic Reconstruction of the Anterior Cruciate and Anterolateral Ligaments Using Hamstring Graft Through a Single Femoral Tunnel and With a Single Femoral Fixation

Patients with complete anterior cruciate ligament (ACL) injury have different degrees of rotational (internal rotation) laxity. A residual pivot shift has been found to be positive in more than 15% of cases after an accurate ACL reconstruction. Improved understanding of the existence, function, and biomechanical role of the anterolateral ligament (ALL) in controlling rotational instability of the knee has redirected and refocused attention on a supplemental extra-articular reconstruction of the ALL in conjunction with the intra-articular ACL reconstruction so as to restore normal kinematics of the knee. This Technical Note describes a technique that allows for a combined ACL and ALL reconstruction using autogenous hamstring graft (semitendinosus and gracilis tendons). One femoral tunnel is used connecting the anatomic femoral attachment of the ALL on the lateral wall of the lateral femoral condyle to the anatomic femoral ACL footprint on the medial wall of the lateral femoral condyle. The remaining part of the graft is fixed to the proximal tibia midway between Gordy's tubercle and the head of the fibula. This Technical Note describes a technique of both ACL and ALL reconstruction with a continuous hamstring graft.

Three-Dimensional CT Evaluation of Tunnel Positioning in ACL Reconstruction Using the Single Anteromedial Bundle Biological Augmentation (SAMBBA) Technique.

Background:Remnant preservation may confer important advantages in the anterior cruciate ligament (ACL)–reconstructed knee. However, the presence of a large remnant may obscure visualization and impair the ability to correctly place tunnels during surgery.Purpose:To determine whether tunnel placement during anatomic ACL reconstruction using the single anteromedial bundle biological augmentation (SAMBBA) technique is consistent and precise when a large native remnant is preserved.Study Design:Case series; Level of evidence, 4.Methods:Included in this study were 99 patients undergoing an ACL reconstruction during which at least 50% of the native ACL was preserved. The femoral tunnel was created using an outside-in specific guide. The tibial tunnel was positioned in the anteromedial region of the ACL footprint, and the remnant was carefully preserved while drilling and passing the semitendinosus graft through it. Postoperatively, 3-dimensional computed tomography (3D CT) was used to evaluate tunnel placement. The mean tunnel locations were calculated and the standard deviation was used to evaluate precision of positioning. Inter- and intrareader agreement were determined to assess reliability of evaluation of tunnel position.Results:The center of the femoral tunnel was positioned at a mean 19.4% (SD, 2%) of the depth of the notch and a mean 23.1% (SD, 3.5%) of the lateral wall height. The center of the tibial tunnel was positioned at a mean 36.3% (SD, 3.8%) of the anteroposterior length of the tibial plateau and at a mean 47.0% (SD, 2.7%) of the mediolateral width. The small standard deviations demonstrate that this technique allows precise tunnel placement. The tunnel positions achieved were consistent with previous anatomic studies of femoral and tibial anteromedial bundle insertion. Intra- and interobserver reliability were high.Conclusion:Three-dimensional CT evaluation demonstrated that despite the presence of a large remnant, placement of femoral and tibial tunnels for anatomic ACL reconstruction using the SAMBBA technique is consistent and precise.

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

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. 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. The ACL graft tension peaked (67±49N) 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±1.3MPa) than the other directions (p<0.01). Second largest pressure was carried in the anterior part (0.6±0.5MPa), followed by proximal and posterior parts (0.4±0.3, 0.2±0.2MPa respectively). 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.

Effects of ACL graft placement on in vivo knee function and cartilage thickness distributions.

Injuries to the anterior cruciate ligament (ACL) frequently lead to early-onset osteoarthritis. Despite advancement in surgical techniques, ACL reconstruction has a limited ability to prevent these degenerative changes. While previous studies have investigated knee function after ACL reconstruction, in vivo investigations of the effects of graft placement on in vivo joint function and cartilage health are limited. This review presents a series of studies that used novel imaging and 3D modeling techniques to determine the in vivo placement of the ACL graft on the femur using two different ACL reconstruction techniques. These techniques resulted in two distinct graft placement groups: one where the ACL was placed anatomically near the center of the native ACL footprint and another where the graft was placed anteroproximally on the femur, centered outside the ACL footprint. We quantified the effects of graft placement on graft deformation during in vivo loading and how these variables affected knee motion. Finally, we quantified whether femoral placement of the graft affected cartilage thickness. Our results demonstrate that achieving anatomic graft placement on the femur is critical to restoring native ACL function and normal knee kinematics. Knees with grafts that more closely restored normal ACL function, and thus knee motion, experienced less focal cartilage thinning than did those that experienced abnormal knee motion. These results suggest that achieving anatomic graft placement is a critical factor in restoring normal knee motion and potentially slowing the development of degenerative changes after ACL reconstruction. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1160-1170, 2017.

Lateral Radiographic Landmarks for ACL and LCL Footprint Origins During All-Epiphyseal Femoral Drilling in Skeletally Immature Knees.

This study was conducted to evaluate the spatial relationship of the anterior cruciate ligament (ACL) and lateral collateral ligament (LCL) femoral footprint origins in knee specimens from skeletally immature donors as viewed on lateral radiographs. Fourteen cadaver specimens of skeletally immature knees from children between 7 and 11 years old at the time of death were examined through gross dissection. Metallic pins were placed at the center of the ACL and LCL femoral footprints, and computed tomography (CT) scans were performed. Sagittal plane CT images were merged to create a view analogous to an intraoperative C-arm image with overlaid ACL and LCL ligament footprints. Ligament origins were then measured as a percent of the epiphyseal depth (% P-A [posterior-anterior]) and height (% P-D [proximal-distal]). The ACL origin was centered at a point located 14% (14% P-A) of the total lateral femoral condyle (LFC) depth from the most posterior aspect of the LFC and 38% (38% P-D) of the LFC height from the most proximal aspect of the posterior physis. The LCL origin was centered at a point 27% P-A and 37% P-D. When viewed on a sagittal CT reconstruction analogous to a perfect lateral intraoperative fluoroscopic view, the ACL footprint origin is posterior and slightly inferior to the LCL origin. Both origins are distal to the distal femoral physis and are posterior to the origin of the popliteus. This study demonstrates a consistent relationship between the origin of the ACL and LCL, which may be useful in guiding safe tunnel placement during all-epiphyseal ACL reconstruction in skeletally immature knees. This anatomic reference can be used intraoperatively to guide and radiographically evaluate ACL tunnel placement while avoiding the LCL origin in skeletally immature patients.

Comparison of Anterior Cruciate Ligament Graft Isometry between Paired Femoral and Tibial Tunnels.

Accurate tunnel placement is important for a successful anterior cruciate ligament (ACL) reconstruction. Controversy exists concerning the preferred method of femoral tunnel preparation, with proponents of both medial portal and transtibial drilling techniques. Current ACL literature suggests that placement of the femoral ACL attachment site posterior or "low" in the ACL footprint leads to more anatomically correct ACL mechanics and better rotational control. There is limited literature focusing on ACL graft displacement through knee range of motion based on specific paired placement of femoral and tibial tunnels. Our purpose was to assess ACL isometry between multiple combinations of femoral and tibial tunnels. We hypothesized that placement of the graft at the posterior aspect of the ACL footprint on the femur would be significantly less isometric and lead to more graft displacement as compared with central or anterior placement. The ACL of matched pairs of cadaveric knees was arthroscopically debrided while leaving the soft tissue footprint on the femur and tibia intact. One knee from each pair underwent notchplasty. In all knees, three femoral and three tibial tunnels were created at the anterior, central, and posterior aspects of the ACL footprint. A suture was passed through each tunnel combination (nine potential pairs), and the change in isometry was measured throughout full knee range of motion. Placement of the femoral tunnel along the posterior aspect of the ACL footprint was less isometric compared with a central or anterior position in the femoral footprint. Placement of a posterior tibial tunnel also led to decreased isometry, but tibial tunnel placement affected isometry to a lesser extent than femoral tunnel placement. The combination of a posterior femoral and posterior tibial tunnel resulted in greater than 1 cm of graft excursion from full flexion to extension. Placement of ACL tunnels at anisometric sites may adversely affect the mechanical properties and behavior of the ACL graft, resulting in either graft laxity in flexion or overconstraint and loss of extension.

Matching the Anterior Cruciate Ligament Graft to the Patient

The aim of anterior cruciate ligament (ACL) reconstruction is to restore normal knee functioning. Key to successful ACL reconstruction understands how to match the ACL graft to the bone tunnel while taking into account interpatient variances. Bone tunnel location and size should be determined according to the original ACL footprint anatomy of each patient. Therefore, appropriate assessments of individual anatomy should be obtained before surgery using imaging techniques. Additionally, graft type should be carefully selected after fully considering biomechanical properties, donor site morbidities, patient activities and lifestyle, and patient preference. This report describes technical issues associated with imaging assessments of ACL anatomy and summarizes the features of currently available graft materials. Despite advancements in ACL reconstruction, certain points remain unclear, such as how much of the native ACL footprint should be covered by the reconstruction graft during surgery. Therefore, further studies are needed to improve the optimum matching of grafts to the requirements of each individual patient.

Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction Using the Modified Transtibial Technique

We present a technique for anterior cruciate ligament (ACL) reconstruction using hamstring tendon autograft with a modified transtibial technique. Our modified transtibial technique has the advantages of the conventional transtibial technique that is familiar to surgeons and that allows the press-fit fixing and enables us to make a relatively long femoral tunnel. To make the femoral tunnel at the anatomic position, the triangular, funnel-shaped bony trough was made to slip the eccentrically positioned guide pin into the anticipated anatomic center with a free-hand technique after marking the anatomic ACL footprint using a microfracture awl through the anteromedial portal. Gradual femoral reaming was performed with knee angle changes, which reduces the chances of posterior wall blowout, increases the femoral tunnel length, and avoids breakage of guide pin at the bending point. Our modified transtibial technique is anticipated to provide a more anatomic placement of the femoral tunnel during ACL reconstruction than the previous traditional transtibial techniques.

Anteromedial Portal Anterior Cruciate Ligament Reconstruction With Tibialis Anterior Allograft

In an effort to better restore normal joint function and kinematics, recent emphasis has been placed on surgical techniques that provide a more anatomic reconstruction of the anterior cruciate ligament (ACL). With femoral tunnel placement shown to play a vital role in the biomechanics, stability, and clinical outcomes after ACL reconstruction, approaches that better approximate the ACL's native femoral origin have been adopted. The independent anteromedial portal technique is thought to better position the femoral tunnel within the native ACL footprint and leave the graft more posteroinferior on the wall of the lateral femoral condyle than the more traditional transtibial approach. This article outlines the surgical technique for an anteromedial portal ACL reconstruction with a tibialis anterior allograft fixed with the Mitek Femoral and Tibial Intrafix sheath and screw system (DePuy Synthes, Raynham, MA).

Technical note: Anterior cruciate ligament reconstruction in the presence of an intramedullary femoral nail using anteromedial drilling.

AIMTo describe an approach to anterior cruciate ligament (ACL) reconstruction using autologous hamstring by drilling via the anteromedial portal in the presence of an intramedullary (IM) femoral nail.METHODSOnce preoperative imagining has characterized the proposed location of the femoral tunnel preparations are made to remove all of the hardware (locking bolts and IM nail). A diagnostic arthroscopy is performed in the usual fashion addressing all intra-articular pathology. The ACL remnant and lateral wall soft tissues are removed from the intercondylar, to provide adequate visualization of the ACL footprint. Femoral tunnel placement is performed using a transportal ACL guide with desired offset and the knee flexed to 2.09 rad. The Beath pin is placed through the guide starting at the ACL’s anatomic footprint using arthroscopic visualization and/or fluoroscopic guidance. If resistance is met while placing the Beath pin, the arthroscopy should be discontinued and the obstructing hardware should be removed under fluoroscopic guidance. When the Beath pin is successfully placed through the lateral femur, it is overdrilled with a 4.5 mm Endobutton drill. If the Endobutton drill is obstructed, the obstructing hardware should be removed under fluoroscopic guidance. In this case, the obstruction is more likely during Endobutton drilling due to its larger diameter and increased rigidity compared to the Beath pin. The femoral tunnel is then drilled using a best approximation of the graft’s outer diameter. We recommend at least 7 mm diameter to minimize the risk of graft failure. Autologous hamstring grafts are generally between 6.8 and 8.6 mm in diameter. After reaming, the knee is flexed to 1.57 rad, the arthroscope placed through the anteromedial portal to confirm the femoral tunnel position, referencing the posterior wall and lateral cortex. For a quadrupled hamstring graft, the gracilis and semitendinosus tendons are then harvested in the standard fashion. The tendons are whip stitched, quadrupled and shaped to match the diameter of the prepared femoral tunnel. If the diameter of the patient’s autologous hamstring graft is insufficient to fill the prepared femoral tunnel, the autograft may be supplemented with an allograft. The remainder of the reconstruction is performed according to surgeon preference.RESULTSThe presence of retained hardware presents a challenge for surgeons treating patients with knee instability. In cruciate ligament reconstruction, distal femoral and proximal tibial implants hardware may confound tunnel placement, making removal of hardware necessary, unless techniques are adopted to allow for anatomic placement of the graft.CONCLUSIONThis report demonstrates how the femoral tunnel can be created using the anteromedial portal instead of a transtibial approach for reconstruction of the ACL.

A Validation Study of a Novel 3-Dimensional MRI Modeling Technique to Identify the Anatomic Insertions of the Anterior Cruciate Ligament.

Background:Anatomic single bundle anterior cruciate ligament (ACL) reconstruction is the current gold standard in ACL reconstructive surgery. However, placement of femoral and tibial tunnels at the anatomic center of the ACL insertion sites can be difficult intraoperatively. We developed a “virtual arthroscopy” program that allows users to identify ACL insertions on preoperative knee magnetic resonance images (MRIs) and generates a 3-dimensional (3D) bone model that matches the arthroscopic view to help guide intraoperative tunnel placement.Purpose:To test the validity of the ACL insertion sites identified using our 3D modeling program and to determine the accuracy of arthroscopic ACL reconstruction guided by our “virtual arthroscopic” model.Study Design:Descriptive laboratory study.Methods:Sixteen cadaveric knees were prescanned using routine MRI sequences. A trained, blinded observer then identified the center of the ACL insertions using our program. Eight knees were dissected, and the centers of the ACL footprints were marked with a screw. In the remaining 8 knees, arthroscopic ACL tunnels were drilled into the center of the ACL footprints based on landmarks identified using our virtual arthroscopic model. Postprocedural MRI was performed on all 16 knees. The 3D distance between pre- and postoperative 3D centers of the ACL were calculated by 2 trained, blinded observers and a musculoskeletal radiologist.Results:With 2 outliers removed, the postoperative femoral and tibial tunnel placements in the open specimens differed by 2.5 ± 0.9 mm and 2.9 ± 0.7 mm from preoperative centers identified on MRI. Postoperative femoral and tibial tunnel centers in the arthroscopic specimens differed by 3.2 ± 0.9 mm and 2.9 ± 0.7 mm, respectively.Conclusion:Our results show that MRI-based 3D localization of the ACL and our virtual arthroscopic modeling program is feasible and does not show a statistically significant difference to an open arthrotomy approach. However, additional refinements will be required to improve the accuracy and consistency of our model to make this an effective tool for surgeons performing anatomic single-bundle ACL reconstructions.Clinical Relevance:Arthroscopic anatomic single-bundle ACL reconstruction is the current gold standard for ACL reconstruction; however, the center of the ACL footprint can be difficult to identify arthroscopically. Our novel modeling can improve the identification of this important landmark intraoperatively and decrease the risk of graft malposition and subsequent graft failure.

The Anatomic Centers of the Femoral and Tibial Insertions of the Anterior Cruciate Ligament: A Systematic Review of Imaging and Cadaveric Studies Reporting Normal Center Locations

Background: The anterior cruciate ligament (ACL) is regularly reconstructed if knee joint function is impaired. Anatomic graft tunnel placement, often assessed with varying measurement methods, in the femur and tibia is considered important for an optimal clinical outcome. A consensus on the exact location of the femoral and tibial footprint centers is lacking. Purpose: To systematically review the literature regarding anatomic centers of the femoral and tibial ACL footprints and assess the mean, median, and percentiles of normal centers. Study Design: Systematic review. Methods: A systematic literature search was performed in the PubMed/Medline database in November 2015. Search terms were the following: “ACL” and “insertion anatomy” or “anatomic footprint” or “radiographic landmarks” or “quadrant methods” or “tunnel placement” or “cadaveric femoral” or “cadaveric tibial.” English-language articles that reported the location of the ACL footprint according to the Bernard and Hertel grid in the femur and the Stäubli and Rauschning method in the tibia were included. Weighted means, weighted medians, and weighted 5th and 95th percentiles were calculated. Results: The initial search yielded 1393 articles. After applying the inclusion and exclusion criteria, 16 studies with measurements on cadaveric specimens or a healthy population were reviewed. The weighted mean of the femoral insertion center based on measurements in 218 knees was 29% in the deep-shallow (DS) direction and 35% in the high-low (HL) direction. The weighted median was 26% for DS and 34% for HL. The weighted 5th and 95th percentiles for DS were 24% and 37%, respectively, and for HL were 28% and 43%, respectively. The weighted mean of the tibial insertion center in the anterior-posterior direction based on measurements in 300 knees was 42%, and the weighted median was 44%; the 5th and 95th percentiles were 39% and 46%, respectively. Conclusion: Our results show slight differences between the weighted means and medians in the femoral and tibial insertion centers. We recommend the use of the 5th and 95th percentiles when considering postoperative placement to be “in or out of the anatomic range.”

Synovial C-Shaped Tibial Footprint of the Anterior Cruciate Ligament.

Background:Although numerous anatomic studies about the anterior cruciate ligament (ACL) structure and attachments have been performed, these studies have not reached consensus on the ACL footprint.Purpose:To investigate the existing controversy regarding the morphology of the tibial ACL insertion (footprint) and confirm histologically that the tibial ACL footprint is not completely filled with ligament tissue.Study Design:Descriptive laboratory study.Methods:The tibial ACL footprint was dissected from 20 different fresh-frozen cadaveric knees (all males; mean age, 68.8 ± 5.4 years [range, 55-80 years]; mean weight, 78 ± 6.6 kg [range, 45-93 kg]). Two knees, 1 with severe osteoarthritis and 1 with previous knee surgery, were excluded. The tibial ACL insertion was observed, and this area was longitudinally divided into 4 parallel slices (0%-25%, 25-50%, 50%-75%, and 75%-100%), embedded in paraffin wax, and stained with hematoxylin-eosin, alcian blue, and picrosirius-polarization. The specimens were measured using a microscope to determine the distances from the anterior to the posterior border of the ACL ligament tibial insertion and the distance from the posterior border to the end of the ligament fibers of the ACL ligament tibial insertions.Results:The 18 evaluated knee specimens confirmed the finding of a C-shaped tibial insertion of the ACL. The measurements showed that the ligament (vertical parallel collagen fibers) occupied only 30.8% of the complete insertion. The remaining area was filled with synovial tissue, demonstrating histologically the “C” shape.Conclusion:This study confirms macroscopically the C-shaped tibial insertion of the ACL and shows histologically that synovial tissue is an indirect insertion filling the major part of the footprint.Clinical Relevance:This anatomic study suggests a different shape of the ACL tibial footprint, which may be useful for new perspectives regarding ACL reconstruction surgery research.