Anterior Cruciate Ligament Insertion Research Articles

Anatomical relationship between insertion sites, tunnel placement, and lateral meniscus anterior horn injury during single and double bundle anterior cruciate ligament reconstructions: A comparative macroscopic and histopathological evaluation in cadavers

PurposeThe influence of tunnel extension outside the anatomical anterior cruciate ligament (ACL) insertion in single-bundle (SB) or double-bundle (DB) ACL reconstruction is unclear. This study aimed to investigate the anatomical relationship between ACL insertion and tunnel extension in SB and DB ACL reconstruction, and the impact of tibial tunnel extension to the insertion of anterior horn of lateral meniscus in terms of injury. MethodsForty-six paired cadaver knees (mean age, 82.7 ± 10.7 years) were used. Right and left knees were used for SB (10 mm) and DB tunnel reaming (6 mm for the anteromedial and posterolateral bundles). Tibial and femoral tunnels were created to aim at the center of the ACL insertion by arthroscopic visualization. The relationship between tunnel extension and ACL insertion was evaluated macroscopically, and there ratio in two groups were compared by chi-square test. Further, the relative risk for meniscus injury based on tunnel placement was estimated. Coronal section of tibia and parallel section to Blumensaat line in femur were prepared to evaluate the relationship among tunnel position, ACL insertion, and anterior horn of the meniscus histologically. ResultsTibial tunnel extension out of the ACL insertion was observed macroscopically in 9 (39.1%) knees of the SB group, and 3 (13.0%) of the DB group (p = 0.045). In femoral tunnels, extension out of the ACL insertion was seen in 8 (34.8%) knees of the SB group and 1 (4.3%) of the DB group (p = 0.011). Partial injuries of the lateral meniscus anterior horn (LMAH) were observed in 5 (21.7%) knees of the SB group and 1 (4.3%) knee of the DB group (p = 0.091). The relative risk for LMAH injury was calculated as 5.0 (odds ratio, 6.1). Microscopically, SB tunnels appeared to expand out of ACL insertion, both in the femur and tibia. ConclusionsThe incidence of tunnel extension out of the ACL insertion in femur and tibia were higher with SB than with DB reconstruction. Furthermore, injury rate of the LMAH in the DB group was lower.

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

Background: Recent literature correlated anterior cruciate ligament (ACL) reconstruction failure to smaller diameter of the harvested hamstring (HS) autograft. However, this approach may be a simplification, as relation of graft size to native ACL size is not typically assessed and oversized grafts may impart their own complications. Purpose: To evaluate in vivo data to determine if the commonly used autografts reliably restore native ACL size. Study Design: Descriptive laboratory study. Methods: Intraoperative data of the tibial insertion area and HS graft diameter were collected and retrospectively evaluated for 46 patients who underwent ACL reconstruction with HS autografts. Magnetic resonance imaging measurements of the cross-sectional area (CSA) of the possible patellar tendon (PT) and quadriceps tendon (QT) autografts were also done for each patient. The percentages of tibial insertion site area restored by the 3 possible grafts were then calculated and compared for each individual. Results: The mean ACL tibial insertion area was 107.2 mm2 (60.5-155.5 mm2). The mean CSAs of PT, HS, and QT were 33.2, 55.3, and 71.4 mm2, respectively. When all grafts were evaluated, the percentage reconstruction of the insertion area varied from 16.2% to 123.1% on the tibial site and from 25.5% to 176.7% on the femoral site, differing significantly for each graft type (P < .05). On average, 32.8% of the tibial insertion area would have been filled with PT, 53.6% by HS, and 69.5% by QT. Based on previous cadaveric studies indicating that graft size goal should be 50.2% ± 15% of the tibial insertion area, 82.7% of patients in the HS group were within this range (36.9%, QT; 30.5%, PT), while 65.2% in the PT group were below it and 60.9% in the QT group were above it. Conclusion: ACL insertion size and the CSAs of 3 commonly used grafts vary greatly for each patient and are not correlated with one another. Thus, if the reconstructed ACL size is determined by the harvested autograft size alone, native ACL size may not be adequately restored. PT grafts tended to undersize the native ACL, while QT might oversize it. Clinical Relevance: These results may help surgeons in preoperative planning, as magnetic resonance imaging measurements can be helpful in determining individualized graft choice to adequately restore the native ACL.

Descriptive anatomy of the anterior cruciate ligament femoral insertion

ObjectiveTo evaluate the morphology of the anterior cruciate ligament (ACL) femoral insertion in order to describe its anatomical features and insertion site location, with the aim of verifying if the ACL femoral insertion has individual characteristics and to provide information for appropriate femoral tunnel placement on anatomic ACL reconstruction. MethodsSixteen knees obtained from amputations were studied. The ACL femoral bundles and insertion shape were observed macroscopically, and the ligaments insertion length and thickness were measured with a digital caliper. The distances between the limits of the ligament to the articular cartilage, and the measurement of the area of insertion were checked using ImageJ software. ResultsThe ACL femoral insertion site was eccentric, closer to the deep condyle cartilage. In ten knees (62.5%), the ACL femoral insertion was oval; the mean length of the insertion was 16.4mm, varying from 11.3 to 19.3mm, the mean thickness varied from 7.85 to 11.23mm, and the mean area of the insertion was 99.7mm2, varying from 80.9 a 117.2mm2. The mean distances between the limits of the ligament to the superficial, deep, and inferior articular cartilage were 9.77±1.21, 2.60±1.20, and 1.86±1.15mm, respectively. ConclusionThere was a 30% to 40% difference between the minimum and maximum results of measurements of ACL femoral insertion length, thickness, and area demonstrating an important individual variation. The insertion site was eccentric, closer to the deep cartilage of the lateral femoral condyle.

Femoral Footprint for Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction: A Cadaveric Study.

PurposeTo identify the femoral footprint of the anterior cruciate ligament (ACL) in Koreans.Materials and MethodsEighteen embalmed cadaveric knees (mean age, 70 years) were examined. First, the shape of the ACL was determined macroscopically. After the ACL femoral footprint was defined, the ACL was cut from the femur and a Kirschner wire was inserted into the center of the ACL, and the position was verified with a C-arm. The position was quantified on the C-arm field using the quadrant method. The length and width of the ACL were measured.ResultsMacroscopically, the ACL is a flat single bundle with an average length of 34 mm and an average width of 9 mm. On average, the center of the ACL insertion site measured with the quadrant method was positioned at 29.5%±2.8% in an anterior direction (from posterior), and at 38.5%±3.2% in a distal direction (from Blumensaat’s line). The anterior and posterior margins of the ACL femoral footprint were the resident’s ridge and the cartilage margin of the lateral femoral condyle, respectively.ConclusionsThe center of the ACL femoral footprint is positioned more anteriorly and distally than the positions identified in previous studies.

Extension of knee immobilization delays recovery of histological damages in the anterior cruciate ligament insertion and articular cartilage in rabbits

[Purpose] To investigate the influence of knee immobilization period on recovery of histological damages in the anterior cruciate ligament (ACL) insertion and articular cartilage in rabbits. This knowledge is important for determining the appropriate rehabilitation approach for patients with ligament injuries, fracture, disuse atrophy, and degenerative joint disease. [Materials and Methods] Forty-eight male Japanese white rabbits were divided equally into the remobilization and control groups. The remobilization group had the right knee surgically immobilized, and was divided equally into four subgroups according to the duration of immobilization (1, 2, 4 and 8 weeks). After the immobilization was removed, the rabbits moved freely for 8 weeks. The control group underwent sham operation and followed the same time course as the remobilization group. The chondrocyte apoptosis rate and chondrocyte proliferation rate in the ACL insertion and articular cartilage were analyzed after remobilization. [Results] In the ACL insertion, the remobilization group had a higher chondrocyte apoptosis rate than the control group after 8 weeks of immobilization, and a lower chondrocyte proliferation rate than the control group after 4 and 8 weeks of immobilization. In the articular cartilage, the remobilization group had a lower chondrocyte proliferation rate than the control group after 8 weeks of immobilization. After 8 weeks of remobilization, the ACL insertion and articular cartilage are not completely recovered after 4 and 8 weeks of immobilization, respectively. [Conclusion] Our results suggest that 8 weeks of remobilization will result in recovery of the ACL insertion after 2 weeks of knee immobilization, and recovery of the articular cartilage after 4 weeks of knee immobilization. If 8 weeks of immobilization occurs, a remobilization duration of more than 8 weeks may be necessary.

Correlations between the anterior cruciate ligament insertion sites dimensions and patient's physical characteristics: an arthroscopic study

Correlations between the anterior cruciate ligament insertion sites dimensions and patient's physical characteristics: an arthroscopic study

Lateral Intercondylar Ridge: Is it a reliable landmark for femoral ACL insertion?: An anatomical study

BackgroundIncorrect femoral tunnel placement is the most common cause of graft failure during Anterior Cruciate Ligament (ACL) Reconstruction. A reliable landmark can minimize errors. AimTo identify whether the Lateral Intercondylar Ridge (LIR) is a consistent anatomical structure and define its relationship with the femoral ACL insertion. Materials and methodsPhase 1: we studied 23 femoral dry bone specimens macroscopically. Using a digital microscribe, the medial surface of the lateral femoral condyle was reconstructed (3D) to evaluate whether there was an identifiable bony ridge.Phase 2: 7 cadaveric specimens with intact soft tissues were dissected to identify the femoral ACL insertion. A 3D reconstruction of the femoral ACL insertion and the surface allowed us to define the relationship between the LIR and the ACL insertion. ResultsAll specimens had a defined LIR on the medial surface of the lateral femoral condyle. The ridge was consistently located just anterior to the femoral ACL insertion. The ACL footprint was present in the depression between the ridge and the Inferior Articular Cartilage Margin (IACM). The mean distance from the midpoint of the IACM to the LIR was 10.1 mm. ConclusionsThis is the first study to use the microscribe to digitally reconstruct the medial surface of the lateral femoral condyle. It shows that the LIR is a consistent anatomical structure that defines the anterior margin of the femoral ACL insertion, which guides femoral tunnel placement. Our findings support the ruler technique, which is a commonly used method for anatomic single bundle ACL reconstruction.

The posterior horn of the lateral meniscus is a reliable novel landmark for femoral tunnel placement in ACL reconstruction

Femoral tunnel placement is essential for good outcome in anterior cruciate ligament (ACL) reconstruction. In the past, several attempts have been made to optimize femoral tunnel placement. It was observed that the posterior horn of the lateral meniscus was always located directly below to the desired femoral ACL tunnel position, when the knee was brought to deep flexion (> 120°). The goal of the present study was to verify the hypothesis that the posterior horn of the lateral meniscus can be used as a landmark for femoral tunnel placement. Out of a consecutive series of ACL reconstructions done by a single surgeon, 55 lateral radiographs were evaluated according to the quadrant method by Bernard and Hertel. Additionally, on anterior-posterior radiographs the femoral tunnel angle was determined. In the present case series the posterior horn of the lateral meniscus could be identified and used as a landmark for femoral tunnel placement in all cases. The mean tunnel depth was 24 ± 5.1% and the mean tunnel height was 31.3 ± 5.7%. The mean femoral tunnel angle was 41 ± 4.9° using the anatomical axis as a reference. Compared to previous cadaver studies the data of the present study were within their anatomical range of the native ACL insertion site. The suggested technique using the posterior horn of the lateral meniscus as a landmark for femoral tunnel placement showed reproducible results and matches the native ACL insertion site compared to previous cadaveric studies. In particular, non-experienced ACL surgeons will benefit from this apparent landmark and the corresponding easy-to-use ACL reconstruction method. IV.

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.

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.

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

This study quantified the error in anterior cruciate ligament (ACL) insertion site location and area estimated from three-dimensional (3D) isotropic magnetic resonance imaging (MRI) by comparing to native insertion sites determined via 3D laser scanning. Isotropic 3D DESS MRI was acquired from twelve fresh-frozen, ACL-intact cadaver knees. ACL insertion sites were manually outlined in each MRI slice, and the resulting contours combined to determine the 3D insertion site shape. Specimens were then disarticulated, and the boundaries of the ACL insertion sites were digitized using a high-accuracy laser scanner. MRI and laser scan insertion sites were co-registered to determine the percent overlapping area and difference in insertion centroid location. Femoral ACL insertion site area averaged 112.7±17.9mm2 from MRI and 109.7±10.9mm2 from laser scan (p=0.345). Tibial insertion area was 134.7±22.9mm2 from MRI and 135.2±15.1mm2 from laser scan (p=0.881). Percentages of overlapping area between modalities were 82.2±10.2% for femurs and 81.0±9.0% for tibias. The root-mean-square differences for ACL insertion site centroids were 1.87mm for femurs and 2.49mm for tibias. The MRI-estimated ACL insertion site centroids were biased on average 0.6±1.6mm proximally and 0.3±1.9mm posteriorly for femurs, and 0.3±1.1mm laterally and 0.5±1.5mm anteriorly for tibias. Errors in ACL insertion site location and area estimated from 3D-MRI were determined via comparison with a high-accuracy 3D laser scanning. Results indicate that MRI can provide estimates of ACL insertion site area and centroid location with clinically applicable accuracy. MRI-based assessment can provide a reliable estimate of the native ACL anatomy, which can be helpful for surgical planning as well as assessment of graft tunnel placement.

Anatomia descritiva da inserção femoral do ligamento cruzado anterior

ObjectiveTo evaluate the morphology of the anterior cruciate ligament (ACL) femoral insertion in order to describe its anatomical features and insertion site location, with the aim of verifying if the ACL femoral insertion has individual characteristics and to provide information for appropriate femoral tunnel placement on anatomic ACL reconstruction. MethodsSixteen knees obtained from amputations were studied. The ACL femoral bundles and insertion shape were observed macroscopically, and the ligaments insertion length and thickness were measured with a digital caliper. The distances between the limits of the ligament to the articular cartilage, and the measurement of the area of insertion were checked using ImageJ software. ResultsThe ACL femoral insertion site was eccentric, closer to the deep condyle cartilage. In ten knees (62.5%), the ACL femoral insertion was oval; the mean length of the insertion was 16.4mm, varying from 11.3 to 19.3mm, the mean thickness varied from 7.85 to 11.23mm, and the mean area of the insertion was 99.7 mm2, varying from 80.9 a 117.2 mm2. The mean distances between the limits of the ligament to the superficial, deep, and inferior articular cartilage were 9.77±1.21, 2.60±1.20, and 1.86±1.15mm, respectively. ConclusionThere was a 30% to 40% difference between the minimum and maximum results of measurements of ACL femoral insertion length, thickness, and area demonstrating an important individual variation. The insertion site was eccentric, closer to the deep cartilage of the lateral femoral condyle.

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.

The Relationship of Anterior Cruciate Ligament Insertion Sites to the Distal Femoral Growth Centers: an MRI study

The Relationship of Anterior Cruciate Ligament Insertion Sites to the Distal Femoral Growth Centers: an MRI study

The prevalence and characteristics of a subcortical cystic lesion at the subspinous region of the knee.

Background Although we observed that subcortical cysts near the attachment of the meniscus or cruciate ligaments are frequently seen with a tear or degeneration of the adjacent meniscus and/or cruciate ligament, there is no large study describing the prevalence, distribution, and associated findings of these cysts. Purpose To evaluate the prevalence and distribution of subcortical cysts near the attachments of the meniscus or cruciate ligaments and evaluate pathologies of the meniscus or cruciate ligaments using magnetic resonance imaging (MRI). Material and Methods We reviewed 1009 knee MRIs for the presence of subcortical cysts near the meniscus or cruciate ligament attachments and evaluated their size, location, edema of the adjacent bone marrow, and integrities of the medial and lateral meniscus and anterior and posterior cruciate ligaments. Results The 110 cysts were found in either the middle (n = 56), posterior (n = 52), or anterior (n = 2) subspinous regions. Sixty-two were at meniscal root insertion, including seven at the lateral meniscus anterior horn, five at the lateral meniscus posterior horn, 48 at the medial meniscus posterior horn, and two at the medial meniscus anterior horn. All were associated with an adjacent meniscal pathology. Of the 34 cysts at the anterior cruciate ligament (ACL) insertion, 28 had ACL pathology. Nine cysts had surrounding edema in the adjacent bone marrow. Conclusion Subcortical cysts at the subspinous region of the knee were seen in 9.6% of knee MRI examinations. Most were in close proximity to the meniscal or cruciate ligaments with associated pathologies, suggesting that abnormal stress on the bone induces cyst formation.

Comparative Anatomy of the Anterior Cruciate Ligament Insertions in Primates

Despite a robust body of clinical literature on human entheses, relatively little is known about their anatomy in other species. We sought to document the microstructure of the femoral and tibial insertions of the anterior cruciate ligament (ACL) in a number of mammals, with a particular focus on Primates. Species investigated included those using unguligrade (deer, sheep), digitigrade (lion, tiger), and plantigrade (gorilla, Diana monkey, human) postures. We also explored the relationships between fibrocartilage thickness at ligament insertion sites and body mass.We found that most anatomical landmarks of the human ACL insertion have homologues in other mammals, including the Lateral Intercondylar Ridge (LIR), the Lateral Intercondylar Posterior Ridge (LIPR), and the Medial Intercondylar Ridge of the Tibia. However, we found that these ridges are not limited termini as is often assumed. Rather, their entheses are expansive and exhibit fibers that extend from both anterior and posterior aspects of these ridges. Considerable variation exists at the lateral border of the tibial ACL insertion, most likely related to spatial distinction of three subdivisions of the ACL (“bundles”) in deer and other ungulates. While primates still display up to three ACL bundles, they adhere more closely to one another and lack distinct septa. Humans share this primate‐typical anatomy.We measured fibrocartilage thickness of the ACL enthesis on histological thin sections using the method of orthogonal intercepts. Results of a standard linear regression of fibrocartilage thickness and body size indicate that there is no relationship between the natural log of body size as reported in the literature and the natural log of fibrocartilage thickness for either the femoral (F = 1.505, p= 0.1) or tibial (F = 2.57, p = 0.09) insertion sites of the ACL. These data suggest the possibility that, despite the potential biomechanical advantage of substantial fibrocartilage thickness, there may be an upper limit dictated by the (in)ability of nutrients and other cellular signals to diffuse within its extracellular matrix.

The effects of graft size and insertion site location during anterior cruciate ligament reconstruction on intercondylar notch impingement

BackgroundIntercondylar notch impingement is detrimental to the anterior cruciate ligament (ACL). Notchplasty is a preventative remodeling procedure performed on the intercondylar notch during ACL reconstruction (ACLR). This study investigates how ACL graft geometry and both tibial and femoral insertion site location may affect ACL-intercondylar notch interactions post ACLR. A range of ACL graft sizes are reported during ACLR, from six millimeters to 11mm in diameter. Variability of three millimeters in ACL insertion site location is reported during ACLR. This study aims to determine the post-operative effects of minor variations in graft size and insertion location on intercondylar notch impingement. MethodsSeveral 3D finite element knee joint models were constructed using three ACL graft sizes and polar arrays of tibial and femoral insertion locations. Each model was subjected to flexion, tibial external rotation, and valgus motion. Impingement force and contact area between the ACL and intercondylar notch compared well with experimental cadaver data from literature. ResultsA three millimeter anterior–lateral tibial insertion site shift of the maximum size ACL increased impingement force by 242.9%. A three millimeter anterior–proximal femoral insertion site shift of the maximum size ACL increased impingement by 346.2%. Simulated notchplasty of five millimeters eliminated all impingement for the simulation with the greatest impingement. For the kinematics applied, small differences in graft size and insertion site location led to large increases in impingement force and contact area. ConclusionsMinor surgical variations may increase ACL impingement. The results indicate that notchplasty reduces impingement during ACLR. Notchplasty may help to improve ACLR success rates.

Evaluation of the Bone-ligament and tendon insertions based on Raman spectrum and its PCA and CLS analysis

Injuries to the Anterior Cruciate Ligament (ACL) and Rotator Cuff Tendon (RCT) are common in physically active and elderly individuals. The development of an artificial prosthesis for reconstruction/repair of ACL and RCT injuries is of increasing interest due to the need for viable tissue and reduced surgically-related co-morbidity. An optimal prosthesis design is still elusive, therefore an improved understanding of the bone-soft tissue interface is extremely urgent. In this work, Raman spectral mapping was used to analyze, at the micron level, the chemical composition and corresponding structure of the bone-soft tissue interface. Raman spectroscopic mapping was performed using a Raman spectrometer with a 785 nm laser coupled to a microscope. Line-mapping procedure was performed on the ACL and RCT bone insertion sites. The classical least squares (CLS) fitting model was created from reference spectra derived from pure bone and soft-tissue components, and spectral maps collected at multiple sites from ACL and RCT specimens. The results suggest that different source of interface shows different boundary, even they seems have the same components. Compared to the common histology results, it provided intact molecular information that can easily distinguished some relative component change.

Influence of Knee Immobilization on Chondrocyte Apoptosis and Histological Features of the Anterior Cruciate Ligament Insertion and Articular Cartilage in Rabbits.

This study examined the influence of immobilization on chondrocyte apoptosis and histological features of the anterior cruciate ligament (ACL) insertion and knee articular cartilage in rabbits. Forty-eight male Japanese white rabbits were assigned to an immobilization (n = 24) or sham (n = 24) group. Rabbits in the immobilization group underwent complete unilateral surgical knee immobilization and rabbits in the sham group underwent a sham surgery. The average thickness of the glycosaminoglycan (GAG) stained red area by safranin O staining, the chondrocyte apoptosis rate and the chondrocyte proliferation rate in the cartilage layer in the ACL insertion and the articular cartilage of the medial tibial condyle were measured at one, two, four and eight weeks in six animals from each group. In the ACL insertion, the chondrocyte apoptosis rate was higher in the immobilization group than in the sham group at two and eight weeks after surgery (p < 0.05). The chondrocyte proliferation rate gradually decreased from two weeks to eight weeks in the immobilization group. The GAG layer was thinner in the immobilization group than in the sham group at two, four and eight weeks after surgery (p < 0.05). In the articular cartilage, the chondrocyte apoptosis rate in the immobilization group was higher than in the sham group at four and eight weeks after surgery (p < 0.05). The GAG layer was significantly thinner in the immobilization group than that in the sham group at four and eight weeks after surgery (p < 0.05). Knee immobilization significantly increased chondrocyte apoptosis at two and eight weeks after surgery in the ACL insertion and at four and eight weeks after surgery in the articular cartilage of the medial tibial condyle, and decreased GAG layer thickness from two to eight weeks after surgery in the ACL insertion and from four to eight weeks after surgery in the articular cartilage.

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.