Description of the attachment geometry of the anteromedial and posterolateral bundles of the ACL from arthroscopic perspective for anatomical tunnel placement

Evaluation of Failed ACL Reconstruction: An Updated Review

Failure rates among primary Anterior Cruciate Ligament Reconstruction (ACLR) range from 3.2% to 11.1%. Recently, there has been increased focus on surgical and anatomic considerations which predispose patients to failure, including excessive posterior tibial slope (PTS), unaddressed high-grade pivot shift, and improper tunnel placement. The purpose of this review was to provide a current summary and analysis of the literature regarding patient-related and technical factors surrounding revision ACLR, rehabilitation considerations, overall outcomes and return to sport (RTS) for patients who undergo revision ACLR. There is a convincingly higher re-tear and revision rate in patients who undergo ACLR with allograft than autograft, especially amongst the young, athletic population. Unrecognized Posterior Cruciate Ligament (PLC) injury is a common cause of ACLR failure and current literature suggests concurrent operative management of high-grade PLC injuries. Given the high rates of revision surgery in young active patients who return to pivoting sports, the authors recommend strong consideration of a combined ACLR + Anterolateral Ligament (ALL) or Lateral extra-articular tenodesis (LET) procedure in this population. Excessive PTS has been identified as an independent risk factor for ACL graft failure. Careful consideration of patient-specific factors such as age and activity level may influence the success of ACL reconstruction. Additional technical considerations including graft choice and fixation method, tunnel position, evaluation of concomitant posterolateral corner and high-grade pivot shift injuries, and the role of excessive posterior tibial slope may play a significant role in preventing failure.

Can patient anthropometry predict the anterior cruciate ligament footprint dimensions? - An MRI-based observational study on north Indian population

Background

Anterior Cruciate Ligament (ACL) reconstruction is one of the most common surgeries being currently done. As we usher into the era of Individualized Anatomic Reconstruction, it is very important to understand the native anatomy of ACL. We aimed to assess the ACL footprint dimensions in our patients and correlate it with anthropometric variables, which can help in preoperative decision making.

Method

A total of 143 eligible patients with suspected ACL injury presented during the study period. Out of which 92 were included in the study. Data on patient's age, sex, height, weight and body mass index (BMI) was recorded. The length and area of both the tibial and femoral footprints were measured on MRI. The footprint dimensions were correlated with the recorded anthropometric data.

Results

The ACL tibial footprint length and area, and femoral footprint length and area were found to be 13.3 ± 2.23 mm, 142.6 ± 26.16 mm2, 11.2 ± 1.97 mm, 125.8 ± 28.75 mm2 respectively. Footprint in males was significantly larger than females. A weak (ρ- 0.21 to 0.4) correlation with weight and moderate (ρ- 0.41 to 0.6) correlation with height was observed. Multivariate linear regression analysis yielded height to be the only significant predictor of footprint dimension from which predictive equations were drawn.

Conclusions

Height was found to be the most significant predictor of footprint dimensions in our patients. The predictive equations and graphs can aid in preoperative surgical decision making resulting in a more anatomical ACL reconstruction and improve the post-operative results.

Usefulness of 3-Dimensional Computed Tomography Assessment of Femoral Tunnel after Anterior Cruciate Ligament Reconstruction

Positioning of the femoral tunnel during anterior cruciate ligament (ACL) reconstruction is the most crucial factor for successful procedure. Owing to the inter-individual variability in the intra-articular anatomy, it can be challenging to obtain precise tunnel placement and ensure consistent results. Currently, the three-dimensional (3D) reconstruction of computed tomography (CT) scans is considered the best method for determining whether femoral tunnels are positioned correctly. Postoperative 3D-CT feedback can improve the accuracy of femoral tunnel placement. Precise tunnel formation obtained through feedback has a positive effect on graft maturation, graft failure, and clinical outcomes after surgery. However, even if femoral tunnel placement on 3D CT is appropriate, we should recognize that acute graft bending negatively affects surgical results. This review aimed to discuss the implementation of 3D-CT evaluation for predicting postoperative outcomes following ACL re-construction. Reviewing research that has performed 3D CT evaluations after ACL reconstruction can provide clinically significant evidence of the formation of ideal tunnels following anatomic ACL reconstruction.

Significant race and gender differences in anterior cruciate ligament tibial footprint location: a 3D-based analysis

BACKGROUND

The aim of the present study was to identify potential race- or gender-specific differences in anterior cruciate ligament (ACL) tibial footprint location from the tibia anatomical coordinate system (tACS) origin, investigate the distances from the tibial footprint to the anterior root of the lateral meniscus (ARLM) and the medial tibial spine (MTS), determine how reliable the ARLM and MTS can be in locating the ACL tibial footprint, and assess the risk of iatrogenic ARLM injuries caused by using reamers with various diameters (7-10 mm).

PATIENTS AND METHODS

Magnetic resonance images of 91 Chinese and 91 Caucasian subjects were used for the reconstruction of three-dimensional (3D) tibial and ACL tibial footprint models. The anatomical coordinate system was applied to reflect the anatomical locations of scanned samples.

RESULTS

The average anteroposterior (A/P) tibial footprint location was 17.1 ± 2.3 mm and 20.0 ± 3.4 mm in Chinese and Caucasians, respectively (P < .001). The average mediolateral (M/L) tibial footprint location was 34.2 ± 2.4 mm and 37.4 ± 3.6 mm in Chinese and Caucasians, respectively (P < .001). The average difference between men and women was 2 mm in Chinese and 3.1 mm in Caucasians. The safe zone for tibial tunnel reaming to avoid ARLM injury was 2.2 mm and 1.9 mm away from the central tibial footprint in the Chinese and Caucasians, respectively. The probability of damaging the ARLM by using reamers with various diameters ranged from 0% for Chinese males with a 7 mm reamer to 30% in Caucasian females with a 10 mm reamer.

CONCLUSIONS

The significant race- and gender-specific differences in the ACL tibial footprint should be taken in consideration during anatomic ACL reconstruction. The ARLM and MTS are reliable intraoperative landmarks for identifying the tibial ACL footprint. Caucasians and females might be more prone to iatrogenic ARLM injury.

LEVEL OF EVIDENCE

III, cohort study.

TRIAL REGISTRATION

This study has been approved by the ethical research committee of the General Hospital of Southern Theater Command of PLA under the code: [2019] No.10.

Loading mechanisms of the anterior cruciate ligament

This review identifies the three-dimensional knee loads that have the highest risk of injuring the anterior cruciate ligament (ACL) in the athlete. It is the combination of the muscular resistance to a large knee flexion moment, an external reaction force generating knee compression, an internal tibial torque, and a knee abduction moment during a single-leg athletic manoeuvre such as landing from a jump, abruptly changing direction, or rapidly decelerating that results in the greatest ACL loads. While there is consensus that an anterior tibial shear force is the primary ACL loading mechanism, controversy exists regarding the secondary order of importance of transverse-plane and frontal-plane loading in ACL injury scenarios. Large knee compression forces combined with a posteriorly and inferiorly sloped tibial plateau, especially the lateral plateau-an important ACL injury risk factor-causes anterior tibial translation and internal tibial rotation, which increases ACL loading. Furthermore, while the ACL can fail under a single supramaximal loading cycle, recent evidence shows that it can also fail following repeated submaximal loading cycles due to microdamage accumulating in the ligament with each cycle. This challenges the existing dogma that non-contact ACL injuries are predominantly due to a single manoeuvre that catastrophically overloads the ACL.

Systematic Review of Cadaveric Studies on Anterior Cruciate Ligament Anatomy Focusing on the Mid-substance Insertion and Fan-like Extension Fibers

PURPOSE

The purpose of this systematic review was to review the anatomical reports concerning the anterior cruciate ligament (ACL) focusing on the mid-substance insertion and fan-like extension fibers, or direct and indirect insertions.

METHODS

Following the PRISMA, data collection was performed. PubMed, Web of Science, and the Cochran library were searched with the terms "anterior cruciate ligament reconstruction", "anatomy", and "cadaver". Studies were included when anatomical dissection of the ACL with cadavers was performed. Biomechanical studies without a detailed description of the anatomical dissection, reviews, and studies not including pictures of the anatomical specimens were excluded from this study. In the full article review, documentation of the mid-substance insertion and fan-like extension fibers, or direct and indirect insertions in the ACL morphology was evaluated in detail.

RESULTS

Fifty-seven studies were included for detailed evaluation. In 2006, Mochizuki et al. reported a macroscopic differentiation between the mid-substance insertion and fan-like extension fibers in the ACL footprint. In 2010, Iwahashi et al. detected the existence of direct and indirect insertions within the femoral ACL footprint, microscopically. Following Mochizuki's report, anatomical evaluation of the mid-substance insertion and fan-like extension fibers, or direct and indirect insertions was reported in 16 of 51 ACL anatomical studies. In studies focusing on the morphology of the ACL, 16 of 28 studies addressed this subject. In these studies, the mid-substance insertion and fan-like extension fibers were differentiated macroscopically, and the direct and indirect insertions were differentiated microscopically within the ACL footprint. Fan-like extension fibers or indirect insertion was reported to surround the mid-substance insertion or direct insertion within the femoral ACL footprint.

CONCLUSIONS

The results of this systematic review showed that, the existence of the mid-substance insertion and fan-like extension fibers, or direct and indirect insertions in ACL morphology is being recognized more widely. These structures should be taken into consideration when surgeons perform ACL surgery.

LEVEL OF EVIDENCE

III. Systematic review of Level-III studies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43465-022-00695-4.

Anterior cruciate ligament foot plate anatomy: 3-dimensional and 2-dimensional MRI evaluation with arthroscopy assessment in a subset of patients

OBJECTIVES

ACL reconstruction tunnel location is an important predictor for outcomes after surgery. The aim was to establish 3D and 2D MRI radiological measurements for native ACL tibial footprint that can provide information to facilitate pre-operative planning for anatomical graft placement. The measurements were also correlated in a subset of patients on arthroscopy.

METHODS

Retrospective evaluation of a consecutive series of knee MRIs with both 2D and 3D MR imaging was performed in 101 patients with 43 men and 66 women and ages 39.5 ± 11.9 years. Two measurements were obtained, tibial to ACL and intermeniscal ligament to ACL (T-ACL) and (IM-ACL), respectively. In a cohort of 18 patients who underwent knee arthroscopy, the T-ACL and IML-ACL distances were also determined by an orthopedic surgeon using a standard scale. ICC, Pearson correlation, and Bland-Altman plot were generated.

RESULTS

For readers 1 and 2, the mean differences between 2D and 3D measurements of T-ACL and IM-ACL were 1.17 and 1.03 mm and 0.65 and 0.65 mm, respectively. The 2D measurements of T-ACL and IM-ACL were larger than the 3D measurements for both readers. The inter-reader reliability was excellent on 2D (0.81-0.96) and fair to excellent on 3D MRI (0.59-0.90). The mean arthroscopic IML-ACL was closer to that of 3D MRI compared to 2D MRI. The mean arthroscopic T-ACL was closer to 2D MRI than 3D MRI.

CONCLUSIONS

Both 2D and 3D MRI show inter-reader reliability with small inter-modality mean differences in the measurements from the tibial or inter-meniscal ligament margins.

KEY POINTS

• The mean differences between 2D and 3D measurements of tibia-ACL and intermeniscal ligament-ACL are small (< 1.2 mm). • As compared to arthroscopy, the mean T-ACL and IML-ACL were closer to measurements from 2D and 3D MRI, respectively. • Both 2D and 3D MRI can be reliably used to delineate ACL foot plate anatomy.

Single-Tunnel Double-Bundle-Like Effect With Footprint Enhancing Anterior Cruciate Ligament Reconstruction

The anterior cruciate ligament (ACL) consists of an anteromedial bundle and a posterolateral bundle giving anteroposterior and rotational stability. It's one of the most commonly injured ligaments and also one of the most commonly performed arthroscopic procedures. Management of ACL injuries is one of the most frequently studied subjects in the literature. Surgical management of ACL injuries varies from extraarticular tenodesis to arthroscopic transtibial reconstruction to double-bundle reconstruction to anatomic single-bundle reconstruction. Although double-bundle ACL reconstruction gives more rotational stability than anatomic single-bundle, functional outcome of both are the same, but the complication rates are much higher for double-bundle reconstruction. Hence, anatomic single-bundle ACL reconstruction has gained popularity. The femoral and tibial footprint of the ACL varies in shape and size; it can be oval, elliptical, rectangular, C-shape, and more. But all available ACL reconstruction techniques prepare a circular tunnel; hence, the footprint coverage of the native ACL is maximum after double-bundle reconstruction and less after anatomic single-bundle reconstruction. So, to have the benefit of double-bundle reconstruction with a single tunnel, we propose our technique of a single-tunnel double-bundle-like effect, with the footprint enhancing ACL reconstruction using our newly designed tunnel dilators.

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

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

Ideal Combination of Anatomic Tibial and Femoral Tunnel Positions for Single-Bundle ACL Reconstruction

Background:

Anatomic anterior cruciate ligament reconstruction (ACLR) is preferred over nonanatomic ACLR. However, there is no consensus on which point the tunnels should be positioned among the broad anatomic footprints.

Purpose/Hypothesis:

To identify the ideal combination of tibial and femoral tunnel positions according to the femoral and tibial footprints of the anteromedial (AM) and posterolateral (PL) anterior cruciate ligament bundles. It was hypothesized that patients with anteromedially positioned tunnels would have better clinical scores, knee joint stability, and graft signal intensity on follow-up magnetic resonance imaging (MRI) than those with posterolaterally positioned tunnels.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 119 patients who underwent isolated single-bundle ACLR with a hamstring autograft from July 2013 to September 2018 were retrospectively investigated. Included were patients with clinical scores and knee joint stability test results at 2-year follow-up and postoperative 3-dimensional computed tomography and 1-year postoperative MRI findings. The cohort was divided into 4 groups, named according to the bundle positions in the tibial and femoral tunnels: AM-AM (n = 33), AM-PL (n = 26), PL-AM (n = 29), and PL-PL (n = 31).

Results:

There were no statistically significant differences among the 4 groups in preoperative demographic data or postoperative clinical scores (Lysholm, Tegner, and International Knee Documentation Committee subjective scores); knee joint stability (anterior drawer, Lachman, and pivot-shift tests and Telos stress radiographic measurement of the side-to-side difference in anterior tibial translation); graft signal intensity on follow-up MRI; or graft failure.

Conclusion:

No significant differences in clinical scores, knee joint stability, or graft signal intensity on follow-up MRI were identified between the patients with anteromedially and posterolaterally positioned tunnels.

Anterior cruciate ligament bundle insertions vary between ACL-rupture and non-injured knees

PURPOSE

The present study aimed to investigate the three-dimensional topographic anatomy of the anterior cruciate ligament (ACL) bundle attachment in both ACL-rupture and ACL-intact patients who suffered a noncontact knee injury and identify potential differences.

METHODS

Magnetic resonance images of 90 ACL-rupture knees and 90 matched ACL-intact knees, who suffered a noncontact knee injury, were used to create 3D ACL insertion models.

RESULTS

In the ACL-rupture knees, the femoral origin of the anteromedial (AM) bundle was 24.5 ± 9.0% posterior and 45.5 ± 10.5% proximal to the flexion-extension axis (FEA), whereas the posterolateral (PL) bundle origin was 35.5 ± 12.5% posterior and 22.4 ± 10.3% distal to the FEA. In ACL-rupture knees, the tibial insertion of the AM-bundle was 34.3 ± 4.6% of the tibial plateau depth and 50.7 ± 3.5% of the tibial plateau width, whereas the PL-bundle insertion was 47.5 ± 4.1% of the tibial plateau depth and 56.9 ± 3.4% of the tibial plateau width. In ACL-intact knees, the origin of the AM-bundle was 17.5 ± 9.1% posterior (p < 0.01) and 42.3 ± 10.5% proximal (n.s.) to the FEA, whereas the PL-bundle origin was 32.1 ± 11.1% posterior (n.s.) and 16.3 ± 9.4% distal (p < 0.01) to the FEA. In ACL-intact knees, the insertion of the AM-bundle was 34.4 ± 6.6% of the tibial plateau depth (n.s.) and 48.1 ± 4.6% of the tibial plateau width (n.s.), whereas the PL-bundle insertion was 42.7 ± 5.4% of the tibial plateau depth (p < 0.01) and 57.1 ± 4.8% of the tibial plateau width (n.s.).

CONCLUSION

The current study revealed variations in the three-dimensional topographic anatomy of the native ACL between ACL-rupture and ACL-intact knees, which might help surgeons who perform anatomical double-bundle reconstruction surgery.

LEVEL OF EVIDENCE

III.

Anterior root of lateral meniscus and medial tibial spine are reliable intraoperative landmarks for the tibial footprint of anterior cruciate ligament

PURPOSE

The aims of the present study were (1) to investigate the tibial footprint location of the anterior cruciate ligament (ACL) in both ACL-ruptured and ACL-intact patients, (2) to identify the relationship of the tibial footprint to the anterior root of the lateral meniscus (ARLM) and medial tibial spine (MTS), and (3) to evaluate the reliability of the ARLM and MTS for identifying the center of the tibial ACL footprint.

METHODS

Magnetic resonance images of 90 knees with ACL rupture and 90 matched-controlled knees were used to create three-dimensional models of the tibia. The tibial ACL footprint was outlined on each model, and its location was measured using an anatomical coordinate system.

RESULTS

No significant difference in the location of the tibial footprint was found between ACL-ruptured and ACL-intact knees. The tibial ACL footprint was located in very close proximity to the ARLM, especially in the M/L direction. The safe zone of tibial tunnel reaming for avoiding damage to the ARLM was 2.6 mm lateral to the center of the native tibial footprint. Both the ARLM and MTS were reliable intraoperative landmarks for identifying the tibial footprint.

CONCLUSIONS

Orthopedic surgeons should be aware of the safe zone of tibial tunnel reaming for avoiding injury to the ARLM. Both the ARLM and MTS might be reliable landmarks for identifying the center of the tibial ACL footprint and may facilitate tibial tunnel placement during anatomical single-bundle ACL reconstruction, especially in cases of revision where the tibial ACL stump is not available.

LEVEL OF EVIDENCE

Level III.

Aperture elongation of the femoral tunnel on the lateral cortex in anatomical double-bundle anterior cruciate ligament reconstruction using the outside-in technique

In anatomical anterior cruciate ligament reconstruction surgery using the outside-in technique, the aperture of the femoral lateral cortex may become elliptical.Retrospective cross-sectional studyTo evaluate the extent of elliptical eccentricity in lateral apertures relative to aperture positioning and clinical failure rate in anatomical anterior cruciate ligament double-bundle reconstruction using outside-in technique.In 75 patients, the aperture elongation factor was defined as the ratio of the major axis of the elliptical aperture to the drill size. Using the lateral epicondyle as a reference point, the lateral femur was divided into sections by distance and angle, and the minimum area was evaluated to assess the relationship between the elongation factor and aperture position of the lateral cortex for each bundle. The incidence and associated clinical performance regarding cortical button migration were also investigated.Aperture elongation factors were 120.2 ± 13.3% and 120.0 ± 16.3% on the anteromedial (AM) and posterolateral (PL) sides, respectively. Femoral tunnel elongation was smallest when the entry point axis were both between 30 to 60° and distance was between 10 to 20 mm and 0 to 10 mm on the AM and PL sides, respectively. During the postoperative follow-up period, intra-tunnel migration was confirmed in 4 of 75 cases (5.3%). Fixation failure neither affected clinical scores nor knee laxity.Areas of minimum elongation for each bundle on both AM and PL sides were found anteroproximally to the lateral epicondyle and positioned near each other. Elongation did not directly affect the clinical outcome.Level of evidence grade: prognostic level III.

Morphology of the resident's ridge, and the cortical thickness in the lateral wall of the femoral intercondylar notch correlate with the morphological variations of the Blumensaat's line

PURPOSE

The purpose of this study was to reveal the morphological correlation between the lateral wall of femoral intercondylar notch and the Blumensaat's line.

METHODS

Forty-one non-paired human cadaveric knees were included in this study (23 female, 18 male: median age 83). Knees were resected, and 3 dimensional computed tomography (3D-CT) was performed. In the axial CT image, bony protrusion (resident's ridge) and cortical thickness in the lateral wall of the femoral intercondylar notch were detected. The length between the top of the ridge, or the most anterior, middle, and most posterior border of cortical thickness and posterior femoral condylar line was measured. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). In the hill types, the length between the hilltop and the posterior border of the Blumensaat's line or the posterior border of the femoral condyle was evaluated. Statistical correlation was calculated between the top of the ridge location, cortical thickness location in the notch, and hilltop location.

RESULTS

There were 7 straight type knees and 34 hill type knees (9 small hill type knees and 25 large hill type knees). Only the hill types of knees were evaluated. The top of the ridge, anterior margin, middle, and posterior border of cortical thickness in the lateral wall of the femoral intercondylar notch existed at 61.8 ± 4.6%, 58.3 ± 12.3%, 42.1 ± 7.9%, and 25.5 ± 5.4% from the posterior condylar line, respectively. The hilltop existed at 24.9 ± 5.9% and 30.7 ± 5.0%, from the posterior border of the Blumensaat's line and from the posterior border of the femoral condyle, respectively. Significant correlation was observed between resident's ridge top, cortical thickness location and hilltop location.

CONCLUSION

In all cadaveric knees, cortical thickness was detected in the lateral wall of the femoral intercondylar notch. The resident's ridge and cortical thickness location had significant correlation with the hill location in the Blumensaat's line, indicating a continuation of the cortical bone from the posterior cortex of the femoral shaft via the hilltop of the Blumensaat's line to the cortical thickness in the lateral wall of the femoral intercondylar notch. For clinical relevance, hilltop location in the Blumensaat's line is a new bony landmark in anterior cruciate ligament surgery.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Femoral Tunnel Placement Analysis in ACL Reconstruction Through Use of a Novel 3-Dimensional Reference With Biplanar Stereoradiographic Imaging

Background:

The femoral-sided anatomic footprint of the anterior cruciate ligament (ACL) has been widely studied during the past decades. Nonanatomic placement is an important cause of ACL reconstruction (ACLR) failure.

Purpose:

To describe femoral tunnel placement in ACLR through use of a comprehensive 3-dimensional (3D) cylindrical coordinate system combining both the traditional clockface technique and the quadrant method. Our objective was to validate this technique and evaluate its reproducibility.

Study Design:

Descriptive laboratory study.

Methods:

The EOS Imaging System was used to make 3D models of the knee for 37 patients who had undergone ACLR. We designed an automated cylindrical reference software program individualized to the distal femoral morphology of each patient. Cylinder parameters were collected from 2 observers’ series of 3D models. Each independent observer also manually measured the corresponding parameters using a lateral view of the 3D contours and a 2-dimensional stereoradiographic image for the corresponding patient.

Results:

The average cylinder produced from the first observer’s EOS 3D models had a 30.0° orientation (95% CI, 28.4°-31.5°), 40.4 mm length (95% CI, 39.3-41.4 mm), and 19.3 mm diameter (95% CI, 18.6-20.0 mm). For the second observer, these measurements were 29.7° (95% CI, 28.1°-31.3°), 40.7 mm (95% CI, 39.7-41.8 mm), and 19.7 mm (95% CI, 18.8-20.6 mm), respectively. Our method showed moderate intertest intraclass correlation among all 3 measuring techniques for both length (r = 0.68) and diameter (r = 0.63) but poor correlation for orientation (r = 0.44). In terms of interobserver reproducibility of the automated EOS 3D method, similar results were obtained: moderate to excellent correlations for length (r = 0.95; P < .001) and diameter (r = 0.66; P < .001) but poor correlation for orientation (r = 0.29; P < .08). With this reference system, we were able to describe the placement of each individual femoral tunnel aperture, averaging a difference of less than 10 mm from the historical anatomic description by Bernard et al.

Conclusion:

This novel 3D cylindrical coordinate system using biplanar, stereoradiographic, low-irradiation imaging showed a precision comparable with standard manual measurements for ACLR femoral tunnel placement. Our results also suggest that automated cylinders issued from EOS 3D models show adequate accuracy and reproducibility.

Clinical Relevance:

This technique will open multiple possibilities in ACLR femoral tunnel placement in terms of preoperative planning, postoperative feedback, and even intraoperative guidance with augmented reality.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Case-controlled study, III.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Case-controlled study, Level III.

Clinical study of anatomical ACL reconstruction with adjustable oval shaped bone tunnels: a CT evaluation

The purpose of this article was to demonstrate an adjustable oval bone tunnel ACLR technique. Aim of this technique was to fit the direction and shape of the footprint and tendon-bone healing passage (TBHP) which was defined as the passage of the normal ACL insertion embedded in the bone as closely as possible. 30 fresh-frozen human cadaveric knees were used to do the ACL anatomical insertions research. 20 patients underwent adjustable oval bone tunnel surgery and 20 patients were in round tunnel group. The tunnel of the presented technique was first drilled with a small diameter round drill bit. Then according to the direction and area of the remnant insersion fibers, the major axes of oval tunnels were expanded to theoretical value with a bone file. Major and minor axes, positions of bone apertures, and areas were evaluated on CT scans. These results were compared with cadaveric and theoretical values. The distance of major axis of oval femoral and tibial tunnel apertures were 10.42 ± 0.55 mm and 12.63 ± 0.5 mm respectively. There're no statistical significance compared with theoretical distance (femoral: P = 0.068, tibial: P = 0.058). The distance of minor axis of oval femoral and tibial tunnel apertures were 6.79 ± 0.28 mm and 6.02 ± 0.29 mm respectively. Both of them were longer than theoretical values (P < 0.001). Compared with the round femoral tunnel, the major/minor axis ratio of oval tunnel (1.53) was more close to the cadaveric results (1.83, P < 0.001). The areas of femoral and tibial apertures were 53.12 ± 1.87 mm² and 54.22 ± 3.21 mm² respectively. Both of them were smaller than the round tunnel area and lager than theoretical areas (P < 0.001). We successfully developed the adjustable single oval bone tunnel ACLR technique, which mimic the direction and shape of the tibial and femoral footprints together with the BTHP better than single round tunnel.

Stereophotogrammetric surface anatomy of the anterior cruciate ligament's tibial footprint: Precise osseous structure and distances to arthroscopically-relevant landmarks

BACKGROUND

While femoral tunnel malposition is widely recognized as the main technical error of failed anterior cruciate ligament (ACL) surgery, tibial tunnel malposition is likely underrecognized and underappreciated.

PURPOSE

To describe more precisely the qualitative and quantitative anatomy of the ACL's tibial attachment in vitro using widely available technology for stereophotogrammetric surface reconstruction, and to test its applicability in vivo.

METHODS

Stereophotogrammetric surface reconstruction was obtained from fourteen proximal tibias of cadaver donors. Measurements of areas and distances from the center of the ACL footprint and the footprint of the obtained bundles to selected arthroscopically-relevant anatomic landmarks were carried out using a three-dimensional design software program, and means and 95% confidence intervals were calculated for these measurements. Reference landmarks were tested in three-dimensional models obtained with arthroscopic videos.

MAIN FINDINGS

The osseous footprint of the ACL was described in detail, including its precise elevated limits, size, and shape, with its elevation pattern described as a quarter-turn-staircase-like ridge. Its internal indentations were related to inter-spaces identified as bundle divisions. Distances from the footprint center to arthroscopically relevant landmarks were obtained and compared to its internal structure, yielding a useful X-like landmark pointing to the most accurate placeholder for the ACL footprint's "anatomic" center. Certain structures and reference landmarks described were readily recognized in three-dimensional models from arthroscopic videos.

CONCLUSIONS

Stereophotogrammetric surface reconstruction is an accessible technique for the investigation of anatomic structures in vitro, offering a detailed three-dimensional depiction of the ACL's osseous footprint.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Case controlled study, Level III.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Torsional Appearance of the Anterior Cruciate Ligament Explaining "Ribbon" and Double-Bundle Concepts: A Cadaver-based Study

PURPOSE

To investigate the effect of the anterior cruciate ligament (ACL) torsion in 90° knee flexion on the morphological appearance of the ACL.

METHODS

Sixty knees from fresh frozen anatomical specimens were dissected. Eighteen knees were excluded according to selection criteria (torn ACL, mucoid degeneration of the ACL, arthritic lesions of the notch, or knees harboring synovial inflammatory pathologies). After the removal of the synovial membrane, the morphology of the ligamentous fibers of the ACL and the twist were analyzed. Twisting of the ACL was measured using a goniometer in 90° knee flexion and defined by the angle of external rotation of the femur on the axis of the tibia required to visualize a flat ACL. The orientation of tibial and femoral footprint was described in a coronal plane for the tibia and a sagittal plane for the femur.

RESULTS

In the 42 knees that were finally included, the ACL was always displayed as a single ribbon-like structure. The torsion of the fibers was on average 83.6° (± 9.4°) in 90° knee flexion. The twisting could be explained by the different orientations of the femoral (vertical in a sagittal plane) and tibial (horizontal in a coronal plane) footprints. An intraligamentous proximal cleavage area was encountered in 11 cases (i.e., 26%).

CONCLUSIONS

The ACL is a twisted structure with 83.6° of external torsion of fibers in 90° knee flexion. It is the torsion in the fibers, due to the relative position of bone insertions, which gives the ACL the appearance of being double bundle.

CLINICAL RELEVANCE

The concept of the torsional flat structure of the native ACL may be of importance during ACL reconstruction, both in terms of graft choice (flat rather than cylindrical) and of technical positioning (torsion).

Radiographic positions of femoral ACL, AM and PL centres: accuracy of guidelines based on the lateral quadrant method

PURPOSE

Femoral tunnel positioning is an important factor in anatomical ACL reconstructions. To improve accuracy, lateral radiographic support can be used to determine the correct tunnel location, applying the quadrant method. Piefer et al. (Arthroscopy 28:872-881, 2012) combined various outcomes of eight studies applying this method to one guideline. The studies included in that guideline used various insertion margins, imaging techniques and measurement methods to determine the position of the ACL centres. The question we addressed is whether condensing data from various methods into one guideline, results in a more accurate guideline than the results of one study.

METHODS

The accuracy of the Piefer's guideline was determined and compared to a guideline developed by Luites et al. (2000). For both guidelines, we quantified the mean absolute differences in positions of the actual anatomical centres of the ACL, AM and PL measured on the lateral radiographs of twelve femora with the quadrant method and the positions according to the guidelines.

RESULTS

The accuracy of Piefer's guidelines was 2.4 mm (ACL), 2.7 mm (AM) and 4.6 mm (PL), resulting in positions significantly different from the actual anatomical centres. Applying Luites' guidelines for ACL and PL resulted in positions not significantly different from the actual centres. The accuracies were 1.6 mm (ACL) and 2.2 mm (PL and AM), which were significantly different from Piefer for the PL centres, and therefore more accurate.

CONCLUSIONS

Condensing the outcomes of multiple studies using various insertion margins, imaging techniques and measurement methods, results in inaccurate guidelines for femoral ACL tunnel positioning at the lateral view.

CLINICAL RELEVANCE

An accurate femoral tunnel positioning for anatomical ACL reconstruction is a key issue. The results of this study demonstrate that averaging of various radiographic guidelines for anatomical femoral ACL tunnel placement in daily practice, can result in inaccurate tunnel positions.

LEVEL OF EVIDENCE

Diagnostic study, Level 1.

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

PURPOSE

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.

METHODS

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.

RESULTS

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 ± 13.8 mm², respectively. Whole width and length of the mid-substance insertion sites were 5.3 ± 1.4, and 15.5 ± 2.9 mm, respectively. The measured areas of the fan-like extensions of the AM and PL bundles were 27 ± 11.5, and 29.5 ± 12.4 mm², respectively.

CONCLUSION

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 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."

Does anatomic single-bundle ACL reconstruction using hamstring autograft produce anterolateral meniscal root tearing?

Background

To determine if tibial tunnel reaming during anatomic single-bundle anterior cruciate ligament (ACL) reconstruction using hamstring autograft can result in anterolateral meniscal root injury, as diagnosed by magnetic resonance imaging (MRI).

Methods

A case series of 104 primary anatomic single-bundle ACL reconstructions using hamstring autograft was retrospectively reviewed. Pre- and post-operative (>1 year) MRIs were radiologically evaluated for each patient, with a lateral meniscus extrusion > 3 mm at the level of the medial collateral ligament midportion on a coronal MRI, to establish anterolateral meniscal root injury.

Results

No patients presented radiological findings of anterolateral meniscal root injury in this case series.

Conclusions

Examining a single-bundle ACL reconstruction technique using hamstring autograft that considered tibial tunnel positioning in the center of the tibial footprint, this case series found no evidence of anterolateral meniscal root injury in patient MRIs, even more than 1-year post-operation.

The correlation of femoral tunnel length with the height and area of the lateral wall of the femoral intercondylar notch in anatomical single-bundle ACL reconstruction

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length and the height and area of the lateral wall of the femoral intercondylar notch in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction .

METHODS

Twenty-four subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (19 females and 5 males; average age 45.5 ± 16.7). In the anatomical single-bundle ACL reconstruction, the femoral and tibial tunnels were created close to the anteromedial bundle insertion site. Using post-operative three-dimensional computed tomography (3D-CT), an accurate lateral view of the femoral condyle was evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analysed. Tunnel placement was also evaluated using 3D-CT (Quadrant method).

RESULTS

The average femoral tunnel length was 35.3 ± 4.9 mm. The length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were 33.6 ± 3.4, 22.8 ± 2.4, and 734.6 ± 136 mm², respectively. Both the height and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 24.1 ± 3.9 % in a shallow-deep direction, and 33.5 ± 7.7 % in a high-low direction.

CONCLUSION

The height and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single-bundle ACL reconstruction. For clinical relevance, surgeons should be careful not to make the femoral tunnel too short in knees in which the femoral intercondylar notch is low in height or small in size.

LEVEL OF EVIDENCE

Case-controlled study, Level III.

A comparative study of effect of autograft compared with allograft anterior cruciate ligament reconstruction on expressions of LOXs and MMPs

The present study aimed to compare the effect of autograft or allograft anterior cruciate ligament (ACL) reconstruction on the expressions of lipoxygenases (LOXs) and matrix metalloproteinases (MMPs) in a New Zealand white rabbit model. New Zealand white rabbits were divided randomly into control, sham, autograft and allograft groups. At the 4th and 8th week after operation, biomechanical testing was performed to measure the primary length, cross-sectional area, maximum tensile load and stiffness of ACL, and HE staining was used to observe cell morphology and fibre alignment of ACL. At the 2nd, 4th and 8th week after operation, quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemistry were applied to detect LOXs and MMPs expressions, and expressions of adenomatous polyposis coli (APC)/Wnt signalling pathway-related proteins. At the 4th and 8th week after operation, the maximum tensile load and stiffness were higher in the autograft group than in the allograft group, and the values at the 8th week were higher than those at the 4th week after operation. The fibroblast proliferation in the allograft group was more significant than that in the autograft group. Compared with the control group, LOXs and MMPs expressions and the positive expression rates of LOXs and MMPs proteins were elevated, and the values in the allograft group were higher than those in the autograft group at all time points. At 8th week after operation, compared with the autograft group, Wnt expression was higher and APC expression was lower in the allograft group. Autograft and allograft ACL reconstruction can promote LOXs and MMPs expressions by activating the APC/Wnt signalling pathway.

The anterior cruciate ligament: a study on its bony and soft tissue anatomy using novel 3D CT technology

PURPOSE

The purpose of this study is twofold: first, to visualize both the tibial and femoral bony insertion surfaces and second, to describe the anterior cruciate ligament (ACL) geometrically, using novel 3D CT imaging. In addition, new concepts of best-fit cylinder and central axis are introduced and evaluated.

METHODS

Eight unpaired knees of embalmed cadavers were used in this study. Following the dissection process, the ACL was injected with a contrast medium for CT imaging. The obtained CT images in extension, 45°, 90° and full flexion were segmented and rendered in 3D allowing morphological and morphometric analysis of the ACL. Anatomical footprint centres, femoral and tibial footprint surface area, best-fit ACL-cylinder intersection area, best-fit ACL-cylinder/footprint coverage ratio, best-fit ACL-cylinder central axis projections at the tibial and femoral footprint in the four positions were used to describe the anatomy of the ACL, based on the Bernard, Hertel and Amis grid.

RESULTS

Based on these parameters, with the best-fit cylinder representing the bulk of the ACL, a changing fibre-recruitment pattern was seen with a moving position of the central axis from posterior to anterior on the femoral and tibial footprint, going from extension to flexion. Furthermore, the numerical data show an increase in tibial footprint coverage by the best-fit cylinder through the ACL when the knee is progressively flexed, whereas an inverse relationship was seen on the femoral side.

CONCLUSION

This study is the first to describe the detailed anatomy of the human ACL with respect to its course and footprints using a 3D approach. It confirms the large difference and inter-patient variability between the tibial and femoral footprint area with the former being significantly smaller. The best-fit cylinder concept illustrates the recruitment pattern of the native ACL where in extension the postero-lateral fibres are recruited and in flexion rather the antero-medial bundle, which can be valuable information in reconstructive purposes. The best-fit cylinder and central axis concept offers additional insights into the optimal tunnel placement at the tibial and femoral footprint in order to cover the largest portion of the native ACL soft tissue, aiming for optimal ACL reconstruction.

Blumensaat's line is not always straight: morphological variations of the lateral wall of the femoral intercondylar notch

PURPOSE

The purpose of this study was to evaluate the morphological variations of the lateral wall of the femoral intercondylar notch.

METHODS

Fifty-two non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ACL. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch parallel to the plane of the femoral bone shaft. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on the femoral side. An accurate lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The morphological variations of Blumensaat's line, the height and area of the lateral wall of the femoral intercondylar notch and the size of the femoral ACL footprints were measured with Image J software.

RESULTS

Blumensaat's line exhibited three types of morphological variations. A straight line was observed in 19 knees (37 %) (straight type). A protrusion spanning less than half of the line was observed at the proximal part of Blumensaat's line in 10 knees (19 %) (small hill type). A protrusion spanning more than half of the line was observed at the proximal part of the line in 23 knees (44 %) (large hill type). In some knees with this large hill type variation, the appearance was similar to that of anterior spur. No significant differences between these three types were observed in either the height and area of the lateral wall of the femoral intercondylar notch or the area of the femoral ACL footprint.

CONCLUSION

In conclusion, Blumensaat's line has three types of morphological variations (straight, small hill and large hill types). For the clinical relevance, when ACL surgery is performed in knees with small or large hill type variations, surgeons should pay close attention to femoral tunnel evaluation and placement, especially for the use of Quadrant method. The grid placement of Quadrant method would be changed in the knees of these type variations.

A Systematic Review of Anterior Cruciate Ligament Femoral Footprint Location Evaluated by Quadrant Method for Single-Bundle and Double-Bundle Anatomic Reconstruction

PURPOSE

To unravel the standard position of anterior cruciate ligament (ACL) femoral origin and deduce practical arthroscopic localization and postsurgical evaluation method.

METHODS

Two independent reviewers searched PubMed using the terms ACL, footprint, femur, etc. We included studies published since January 1, 2000, in which the results were measured by Bernard's quadrant method. This method consists of 4 distances, including total diameter of lateral condyle along Blumensaat's line (distance t), maximum intercondylar notch height (distance h), distance from center of footprint to proximal border (distance x), and distance from center of footprint to Blumensaat's line (distance y). The data of included studies were combined to calculate theoretical centers and standard area for both ACL as a whole bundle and as anteromedial (AM) and posterolateral (PL) bundles individually. Finally, we translated the combined data to arthroscopic localization and postsurgical evaluation.

RESULTS

A total of 13 studies were included. The theoretical centers of ACL as a whole bundle is 28.4% ± 5.1% (x) of distance t and 35.7% ± 6.9% (y) of distance h, whereas AM bundle is 24.2% ± 4%, 21.6% ± 5.2% (x, y) and PL bundle is 32.8% ± 4.7%, 46.7% ± 4.9% (x, y), respectively. The standard area of ACL footprint is a circle with a center of 27.53%, 35.85% (x, y), and a radius of 4.58%, 9.2% (x, y), respectively. Translation of combined data shows that under arthroscopy, for single-bundle ACL reconstruction, the midpoint of distance from border of proximal to distal articular cartilage is the center of anatomic femoral socket.

CONCLUSIONS

Combined data unravel the standard position of ACL femoral origin. It can be used by clinicians to localize anatomic tunnel both in surgery and postsurgical evaluation. For single-bundle ACL reconstruction, the midpoint of lateral femoral condyle corresponds to anatomic socket.

LEVEL OF EVIDENCE

Level V, systematic review of anatomic studies.

Conventional over-the-top-aiming devices with short offset fail to hit the center of the human femoral ACL footprint in medial portal technique, whereas medial-portal-aiming devices with larger offset hit the center reliably

INTRODUCTION

Aim of this study was to investigate the accuracy of a conventional over-the-top-guide (OTG) with a typically short offset to hit the center of the native femoral ACL footprint through the anteromedial portal in comparison to a specific medial-portal-aimer (MPA) with larger offset.

MATERIALS AND METHODS

In 20 matched human cadaveric knees, insertion sites of the ACL were marked in medial arthrotomy. An OTG with an offset of 5.5 mm, respectively, the MPA with 9 mm offset was used in a medial portal approach to locate the center of a single bundle ACL reconstruction tunnel with k-wires. Distances from the footprint center, the OTG drilling and the MPA drilling to the roof of the intercondylar notch and to the deep cartilage margin were determined. After positioning of radiological markers, radiographic analysis was performed according to the quadrant technique as described by Bernard and Hertel.

RESULTS

The distance from ACL origin to the roof of the notch was 10.3 (±2.1) mm, in the OTG group 6.7 (±1.5) mm and in the MPA group 9.6 (±1.9) mm. The distance to the deep cartilage margin was 9.5 (±1.7) mm from ACL origin, 4.8 (±1.3) mm with OTG and 8.7 (±1.4) mm with MPA. There were statistically significant differences between the distances of the footprint center and the OTG group after measuring and also after radiographic analysis (p < 0.0001). Using the MPA, no significant different distances in comparison to the anatomical ACL center were found (p > 0.0001). There was an increased risk for femoral blow (9/10 vs. 0/10) in the OTG group after overdrilling with a 9 mm drill.

CONCLUSION

Short (5.5 mm) offset femoral aiming devices fail to locate the native ACL footprint center in medial portal approach with an increased risk for femoral blowout when overdrilling. The special medial-portal-aiming device with 9 mm offset hit the center reliably.

CT assessment of femoral tunnel placement after partial ACL reconstruction

INTRODUCTION

When one of the anterior cruciate ligament (ACL) bundles is torn, it seems appropriate to preserve the remaining bundle to improve the vascularization and proprioception of the graft, and to reproduce the attachment sites of the torn bundle. After ACL reconstruction, the functional result is worse when the tunnels are positioned further away from the native ACL's isometric attachment points. The goal of this study was to use CT 3D reconstructions to analyse the position of the femoral tunnel following partial ACL reconstruction and to compare it to complete ACL reconstruction cases. We hypothesized that the femoral tunnel positioning was optimal during partial ACL reconstruction.

METHODS

In this prospective single-centre study, 16 patients who underwent isolated anteromedial bundle reconstruction were evaluated during the immediate postoperative period using 3D reconstruction of CT images. During this same period, 180 patients who underwent complete ACL reconstruction in the same surgery unit served as a control group.

RESULTS

In the partial ACL reconstruction group, 6 tunnels (37.5%) were in the optimal position and 10 tunnels (62.5%) were not. In the complete ACL reconstruction group, 124 femoral (68.9%) were in the optimal position and 56 (31.1%) were not (P<0.05).

DISCUSSION

Femoral tunnel positioning is not always optimal in patients who undergo partial ACL reconstruction. Three-dimensional CT reconstruction is a good tool to help surgeons detect and learn from their errors.

LEVEL OF EVIDENCE

III (case-control study).

The difference in centre position in the ACL femoral footprint inclusive and exclusive of the fan-like extension fibres

PURPOSE

The purpose of this study was to compare the centre position of each anterior cruciate ligament bundle in its femoral footprint in measurements including and excluding the fan-like extension fibres.

METHODS

Fourteen non-paired human cadaver knees were used. 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 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 fibres. An accurate lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The centre position of each bundle, including and excluding the fan-like extension fibres, was measured with ImageJ software (National Institution of Health). Evaluation of the centre position was performed using the modified quadrant method.

RESULTS

The centre of the femoral AM bundle including the fan-like extension was located at 28.8% in a shallow-deep direction and 37.2% in a high-low direction. When the AM bundle was evaluated without the fan-like extension, the centre was significantly different at 34.6% in a shallow-deep direction (p = 0.000) and 36% in a high-low direction. The centre of the PL bundle including the fan-like extension was found at 37.1% in a shallow-deep direction and 73.4% in a high-low direction. When the PL bundle was evaluated without the fan-like extension, the centre was significantly different at 42.7% in a shallow-deep direction (p = 0.000) and 69.3% in a high-low direction (p = 0.000).

CONCLUSION

The centre position of the AM and PL bundles in the femoral ACL footprint was significantly different depending on the inclusion or exclusion of the fan-like extension fibres. For the clinical relevance, to reproduce the direct femoral insertion in the anatomical ACL reconstruction, tunnels should be placed relatively shallow and high in the femoral ACL footprint.

Proportional evaluation of anterior cruciate ligament footprint size and knee bony morphology

PURPOSE

The purpose of this study was to reveal the correlation in size between the native anterior cruciate ligament (ACL) footprint and the femoral intercondylar notch and the tibia plateau, and to calculate the proportion in size between the ACL footprint and knee bony morphology.

METHODS

Twenty-six non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ACL. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on both the femoral and tibial sides. An accurate lateral view of the femoral condyle and an axial view of the tibial plateau were photographed with a digital camera, and the images were downloaded to a personal computer. The size of the femoral and tibial ACL footprints and the area of the lateral wall of the intercondylar notch and the tibia plateau were measured with Image J software (National Institution of Health).

RESULTS

The sizes of the native femoral and tibial ACL footprints were 69.8 ± 25 and 133.8 ± 31.3 mm(2), respectively. The areas of the lateral wall of the intercondylar notch and the tibia plateau were 390.5 ± 70.5 and 2,281.7 ± 377.3 mm(2), respectively. The femoral ACL footprint area and the area of the lateral wall of the femoral intercondylar notch (Pearson's correlation coefficient = 0.603, p = 0.001), and the tibial ACL footprint area and the area of the tibia plateau (Pearson's correlation coefficient = 0.452, p = 0.02) both showed significant correlation. The femoral ACL footprint was 17.8 ± 4.9 %, the size of the lateral wall of the femoral intercondylar notch, and the tibial ACL footprint was 5.9 ± 1.3 %, the size of the tibia plateau.

CONCLUSION

For clinical relevance, the femoral ACL footprint is approximately 18 %, the size of the intercondylar notch, and the tibial ACL footprint is approximately 6 %, the size of the tibia plateau. It might be possible to predict the size of the ACL measuring these parameters preoperatively.

The Apex of the Deep Cartilage: A Landmark and New Technique to Help Identify Femoral Tunnel Placement in Anterior Cruciate Ligament Reconstruction

PURPOSE

The purpose of this study was to evaluate the apex of the deep cartilage (ADC) as a landmark to help guide femoral tunnel placement during anatomic single-bundle anterior cruciate ligament (ACL) reconstruction. Our secondary purpose was to assess whether or not the endoscopic transtibial femoral offset drill guide could reach the center of the ACL's femoral footprint.

METHODS

Eight formalin-injected cadaveric knees were dissected and the center of the ACL femoral footprints identified. The ADC was selected as an easily identifiable landmark during arthroscopy and was used to reference the position of the ACL femoral footprint with the knee flexed at 90°. Next, a 7-mm transtibial femoral ACL drill guide was used to engage the posterior aspect of the lateral condyle at the level of the femoral footprint. This position was marked, and the distance from the center of the femoral footprint was recorded for each specimen. Descriptive statistics were used to report our measurements.

RESULTS

The median high and shallow measurements were 3 mm (range, 1 to 4 mm) and 12 mm (range, 11 to 17 mm), respectively. The femoral offset guide never reached the center of the femoral footprint in all specimens; the median distance between the 2 measurements was 4.5 mm (range, 2 to 9 mm).

CONCLUSIONS

If the anatomy is difficult to delineate at the time of reconstruction, our study suggests using the ADC as a landmark to guide anatomic placement. The dissection of 8 cadavers showed that the center of the ACL femoral footprint had a median position of 3 mm high and 12 mm shallow to the ADC. We also showed that the transtibial femoral offset guide did not reach the center of the ACL footprint on all specimens and should therefore not be used for anatomic ACL reconstruction.

CLINICAL RELEVANCE

Current commercially available transtibial femoral offset guides cannot reach the center of the ACL's femoral footprint and therefore should not be used. Alternative techniques, such as referencing from the ADC through an anteromedial (AM) portal, are recommended.

Anatomy of the anterior cruciate ligament insertion sites: comparison of plain radiography and three-dimensional computed tomographic imaging to anatomic dissection

PURPOSE

The aim of this study was to provide quantitative data on insertion sites of anterior cruciate ligament (ACL) and to assess the correlation among measurements of anatomic dissection, plain radiographs, and 3D CT images to determine whether radiologic data can accurately reflect real anatomic measurements.

METHODS

Fifteen cadaveric knees were assessed using the three measurement modalities. Lengths of the long and short axis, area, and centre position of each bundle insertion sites by quadrant method were examined on both the femur and tibia. Distances from the insertion centre to distal cortical and posterior cortical margins of condyle on femur, and distance between insertion centres on tibia were also inspected.

RESULTS

The average ACL insertion position in the three measurement modalities was at 33.9 % in deep-shallow position and at 26.5 % in high-low position for anteromedial (AM) bundle and at 39.2 and 54.8 %, respectively, for posterolateral (PL) bundle in femur. For tibia, it was at 36.9 % in anterior-posterior position and 47.1 % in medial-lateral position for AM bundle and at 43.1 and 53.5 %, respectively, for PL bundle. The slight differences in various measurements among the three modalities were not statistically significant.

CONCLUSIONS

The femoral insertion positions were considerably shallow and low, whereas tibial insertion positions were near the average compared to those in previous studies. Plain radiographic and 3D CT measurements showed a reliable correlation with anatomic dissection measurements. The clinical relevance is that plain radiographs rather than 3D CT can be used as a post-operative evaluation tool after ACL reconstruction.

Size correlation between the tibial anterior cruciate ligament footprint and the tibia plateau

PURPOSE

The purpose of this study was to reveal the correlation between the size of the native anterior cruciate ligament (ACL) footprint and the size of the tibia plateau.

METHODS

Twenty-four non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ACL. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on both the femoral and tibial sides. An accurate lateral view of the femoral condyle and the tibial plateau was photographed with a digital camera, and the images were downloaded to a personal computer. The size of the femoral and tibial ACL footprints, and anterior-posterior (AP) and medial-lateral (ML), lengths of the tibia plateau and area of tibia plateau were measured with Image J software (National Institution of Health).

RESULTS

The sizes of the native femoral and tibial ACL footprints were 72.3 ± 24.4 and 134.1 ± 32.4 mm(2), respectively. The AP lengths of the whole, medial and lateral facet of the tibia plateau were as follows: 44.5 ± 4.1, 40.8 ± 4.1 and 36.8 ± 4 mm, respectively. The ML length of the tibia plateau was 68.3 ± 5.5 mm. Total area of tibia plateau was 2,282.9 ± 378.7 mm(2). The AP length of the lateral facet of the tibia plateau (Pearson's correlation coefficient = 0.508, p = 0.011) and the total area of tibia plateau (Pearson's correlation coefficient = 0.442, p = 0.031) were significantly correlated with the size of the tibial ACL footprint.

CONCLUSION

For clinical relevance, the AP length of lateral facet of the tibia plateau and total area of tibia plateau are significantly correlated with the size of the tibial ACL footprint. It might be possible to predict the size of the ACL measuring these parameters.

Flat midsubstance of the anterior cruciate ligament with tibial "C"-shaped insertion site

PURPOSE

This anatomical cadaver study was performed to investigate the flat appearance of the midsubstance shape of the anterior cruciate ligament (ACL) and its tibial "C"-shaped insertion site.

METHODS

The ACL midsubstance and the tibial ACL insertion were dissected in 20 cadaveric knees (n = 6 fresh frozen and n = 14 paraffined). Magnifying spectacles were used for all dissections. Morphometric measurements were performed using callipers and on digital photographs.

RESULTS

In all specimens, the midsubstance of the ACL was flat with a mean width of 9.9 mm, thickness of 3.9 mm and cross-sectional area of 38.7 mm(2). The "direct" "C"-shaped tibial insertion runs from along the medial tibial spine to the anterior aspect of the lateral meniscus. The mean width (length) of the "C" was 12.6 mm, its thickness 3.3 mm and area 31.4 mm(2). The centre of the "C" was the bony insertion of the anterior root of the lateral meniscus overlayed by fat and crossed by the ACL. No posterolateral (PL) inserting ACL fibres were found. Together with the larger "indirect" part (area 79.6 mm(2)), the "direct" one formed a "duck-foot"-shaped footprint.

CONCLUSION

The tibial ACL midsubstance and tibial "C"-shaped insertion are flat and are resembling a "ribbon". The centre of the "C" is the bony insertion of the anterior root of the lateral meniscus. There are no central or PL inserting ACL fibres. Anatomical ACL reconstruction may therefore require a flat graft and a "C"-shaped tibial footprint reconstruction with an anteromedial bone tunnel for single bundle and an additional posteromedial bone tunnel for double bundle.

The Lateral Meniscus as a Guide to Anatomical Tibial Tunnel Placement During Anterior Cruciate Ligament Reconstruction

Purpose:

The aim of the study is to show, on an MRI scan, that the posterior border of the anterior horn of the lateral meniscus (AHLM) could guide tibial tunnel position in the sagittal plane and provide anatomical graft position.

Method:

One hundred MRI scans were analysed with normal cruciate ligaments and no evidence of meniscal injury. We measured the distance between the posterior border of the AHLM and the midpoint of the ACL by superimposing sagittal images.

Results:

The mean distance between the posterior border of the AHLM and the ACL midpoint was -0.1mm (i.e. 0.1mm posterior to the ACL midpoint). The range was 5mm to -4.6mm. The median value was 0.0mm. 95% confidence interval was from -0.5 to 0.3mm.

A normal, parametric distribution was observed and Intra- and inter-observer variability showed significant correlation (p<0.05) using Pearsons Correlation test (intra-observer) and Interclass correlation (inter-observer).

Conclusion:

Using the posterior border of the AHLM is a reproducible and anatomical marker for the midpoint of the ACL footprint in the majority of cases. It can be used intra-operatively as a guide for tibial tunnel insertion and graft placement allowing anatomical reconstruction. There will inevitably be some anatomical variation. Pre-operative MRI assessment of the relationship between AHLM and ACL footprint is advised to improve surgical planning.

Level of Evidence:

Level 4.

Ribbon like appearance of the midsubstance fibres of the anterior cruciate ligament close to its femoral insertion site: a cadaveric study including 111 knees

PURPOSE

Recently, the configuration of the anterior cruciate ligament (ACL) from its direct femoral insertion to midsubstance was found to be flat. This might have an important impact for anatomical ACL reconstruction. The purpose of this anatomical study was to evaluate the macroscopic appearance of the ACL from femoral to midsubstance.

METHODS

The ACL was dissected in 111 human fresh frozen cadaver knees from its femoral insertion to midsubstance, and the shape was described. The anatomical findings were documented on digital photographs and on video. Thirty knees were sent for computed tomography (CT), magnetic resonance imaging (MRI) and histology of the femoral ACL insertion.

RESULTS

Two millimetres from its direct femoral insertion, the ACL fibres formed a flat ribbon in all dissected knees without a clear separation between AM and PL bundles. The ribbon was in exact continuity of the posterior femoral cortex. The width of the ribbon was between 11.43 and 16.18 mm and the thickness of the ACL was only 2.54-3.38 mm. 3D CT, MRI and the histological examination confirmed above findings.

CONCLUSION

This is a detailed anatomical study describing the ribbon-like structure of the ACL from its femoral insertion to midsubstance. A key point was to carefully remove the surface fibrous membrane of the ACL. A total of 2-3 mm from its bony femoral insertion, the ACL formed a flat ribbon without a clear separation between AM and PL bundles. The ribbon was in exact continuity of the posterior femoral cortex. The findings of a flat ligament may change the future approach to femoral ACL footprint and midsubstance ACL reconstruction and to graft selection.

Effect of anteromedial portal entrance drilling angle during anterior cruciate ligament reconstruction: a three-dimensional computer simulation

PURPOSE

The object of this study was to evaluate entrance angle effects on femoral tunnel length and cartilage damage during anteromedial portal drilling using three-dimensional computer simulation.

MATERIALS AND METHODS

Data was obtained from an anatomic study performed using 16 cadaveric knees. The anterior cruciate ligament femoral insertion was dissected and the knees were scanned by computer tomography. Tunnels with different of three-dimensional entrance angles were identified using a computer simulation. The effects of different entrance angles on the femoral tunnel length and medial femoral cartilage damage were evaluated. Specifically, tunnel length and distance from the medial femoral condyle to a virtual cylinder of the femoral tunnel were measured.

RESULTS

In tunnels drilled at a coronal angle of 45°, an axial angle of 45°, and a sagittal angle of 45°, the mean femoral tunnel length was 39.5±3.7 mm and the distance between the virtual cylinder of the femoral tunnel and the medial femoral condyle was 9.4±2.6 mm. The tunnel length at a coronal angle of 30°, an axial angle of 60°, and a sagittal angle of 45°, was 34.0±2.9 mm and the distance between the virtual cylinder of the tunnel and the medial femoral condyle was 0.7±1.3 mm, which was significantly shorter than the standard angle (p<0.001).

CONCLUSION

Extremely low and high entrance angles in both of axial plane and coronal plane produced inappropriate tunnel angles, lengths and higher incidence of cartilage damage. We recommend that angles in proximity to standard angles be chosen during femoral tunnel drilling through the anteromedial portal.

Commonly used ACL autograft areas do not correlate with the size of the ACL footprint or the femoral condyle

PURPOSE

The purpose of this study was to reveal the correlation between the size of the native anterior cruciate ligament (ACL) footprint and the area of commonly used autografts using cadaveric knees.

METHODS

Twenty-Four non-paired human cadaver knees were used. The size of the femoral and tibial ACL footprints, length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were photographed and measured with Image J software (National Institution of Health). Simulating an semitendinosus tendon (ST) graft, the ST was cut in half. The bigger half was regarded as the antero-medial (AM) bundle, and the remaining half was regarded as the postero-lateral (PL) bundle. Simulating an semitendinosus and gracilis (ST-G) graft, the bigger half of the ST and G was regarded as the AM bundle, and the smaller half of the ST was regarded as the PL bundle. Each graft diameter was measured, and the graft area was calculated. Simulating a bone-patella tendon-bone (BPTB) graft, a 10-mm wide BPTB graft was harvested and the area calculated.

RESULTS

The sizes of the native femoral and tibial ACL footprints were 72.3 ± 24.4 and 134.1 ± 32.4 mm(2), respectively. The length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were 29.5 ± 2.5 mm, 17.7 ± 2.3 mm, and 400.9 ± 62.6 mm(2), respectively. The average areas of the ST, ST-G, and BPTB graft were 52.7 ± 6.3, 64.7 ± 7.6, and 37.1 ± 7.5 mm(2). Both the height and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with the femoral size of the ACL footprint (p = 0.007 and 0.008, respectively). However, no significant correlation was observed between ACL footprint size and autograft size. No significant correlation was observed between autograft size and the size of the lateral wall of the femoral intercondylar notch.

CONCLUSION

In ACL reconstruction, if the reconstructed ACL size is determined by the harvested autograft size alone, native ACL size and anatomy are unlikely to be reproduced.

Anatomic single-bundle ACL surgery: consequences of tibial tunnel diameter and drill-guide angle on tibial footprint coverage

PURPOSE

To investigate the consequences of differences in drill-guide angle and tibial tunnel diameter on the amount of tibial anatomical anterior cruciate ligament (ACL) footprint coverage and the risk of overhang of the tibial tunnel aperture over the edges of the native tibial ACL footprint.

METHODS

Twenty fresh-frozen adult human knee specimens with a median age of 46 years were used for this study. Digital templates mimicking the ellipsoid aperture of tibial tunnels with a different drill-guide angle and a different diameter were designed. The centres of these templates were positioned over the geometric centre of the tibial ACL footprint. The amount of tibial ACL footprint coverage and overhang was calculated. Risk factors for overhang were determined. Footprint coverage and the risk of overhang were also compared between a lateral tibial tunnel and a classic antero-medial tibial tunnel.

RESULTS

A larger tibial tunnel diameter and a smaller drill-guide angle both will create significant more footprint coverage and overhang. In 45% of the knees, an overhang was created with a 10-mm diameter tibial tunnel with drill-guide angle 45°. Furthermore, a lateral tibial tunnel was found not to be at increased risk of overhang.

CONCLUSION

A larger tibial tunnel diameter and a smaller drill-guide angle both will increase the amount of footprint coverage. Inversely, larger tibial tunnel diameters and smaller drill-guide angles will increase the risk of overhang of the tibial tunnel aperture over the edges of the native tibial ACL footprint. A lateral tibial tunnel does not increase the risk of overhang.

Evaluation of ACL mid-substance cross-sectional area for reconstructed autograft selection

PURPOSE

The purpose of this study was to compare the size of the native ACL mid-substance cross-sectional area and the size of commonly used autografts. Hypothesis of this study was that the reconstructed graft size with autografts would be smaller than the native ACL size.

METHODS

Twelve non-paired human cadaver knees were used. The ACL was carefully dissected, and the mid-substance of the ACL was cross-sectioned parallel to the articular surface of the femoral posterior condyles at 90 degrees of knee flexion. The size of the cross-sectional area of the ACL, and the femoral and tibial footprints were measured using Image J software (National Institute of Health). The semitendinosus tendon (ST) and the gracilis (G) tendon were harvested and prepared for ACL grafts. Simulating an ST graft, the ST was cut in half. The bigger half was regarded as the antero-medial (AM) bundle, and the remaining half was regarded as the postero-lateral (PL) bundle. Simulating an ST-G graft, the bigger half of the ST and G were regarded as the AM bundle, and the smaller half of the ST was regarded as the PL bundle. Each graft diameter was measured, and the graft area was calculated. Simulating a rectangular bone-patella tendon-bone (BPTB) graft, a 10-mm-wide BPTB graft was harvested and the area calculated.

RESULTS

The sizes of the ACL mid-substance cross-sectional area, femoral and tibial ACL footprint were 46.9 ± 18.3, 60.1 ± 16.9 and 123.5 ± 12.5 mm(2), respectively. The average areas of the ST, ST-G, and BPTB grafts were 52.0 ± 3.8, 64.4 ± 6.2, and 40.8 ± 6.7 mm(2), respectively. The ST and BPTB grafts showed no significant difference in graft size when compared with the ACL cross-sectional area.

CONCLUSION

ST and BPTB autografts were able to reproduce the native size of the ACL mid-substance cross-sectional area. The ST-G graft was significantly larger than the ACL cross-sectional area. For clinical relevance, ST and BPTB grafts are recommended in order to reproduce the native size of the ACL in anatomical ACL reconstruction with autograft.

Single-bundle anterior cruciate ligament reconstruction: a biomechanical cadaveric study of a rectangular quadriceps and bone--patellar tendon--bone graft configuration versus a round hamstring graft

PURPOSE

The purposes of this study were to investigate anterior tibial translation under loading conditions after single-bundle (SB) anterior cruciate ligament (ACL) reconstruction using a rectangular tunnel placement strategy with quadriceps and bone--patellar tendon--bone (BPTB) graft and to compare these data with a SB hamstring reconstruction with a round tunnel design.

METHODS

In 9 human cadaveric knees, the knee kinematics were examined with robotic/universal force-moment sensor testing. Within the same specimen, the knee kinematics under simulated pivot-shift and KT-1000 arthrometer (MEDmetric, San Diego, CA) testing were determined at 0°, 15°, 30°, 60°, and 90° of flexion under different conditions: intact knee, ACL-deficient knee, and SB ACL-reconstructed knee. For the SB ACL-reconstructed knee, 3 different SB reconstruction techniques were used: a rectangular tunnel strategy (9 × 5 mm) with quadriceps graft, a rectangular tunnel strategy with BPTB graft, and a round tunnel strategy (7 mm) with hamstring graft.

RESULTS

In a simulated Lachman test, a statistically significant difference was found at 0° and 15° of knee flexion between the rectangular reconstruction with quadriceps graft (5.1 ± 1.2 mm and 8.3 ± 2 mm, respectively) or BPTB graft (5.3 ± 1.5 mm and 8 ± 1.9 mm, respectively) and the reconstruction using hamstring graft (7.2 ± 1.4 mm and 12 ± 1.8 mm, respectively) (P = .032 and P = .033, respectively, at 0°; P = .023 and P = .02, respectively, at 15°). On the simulated pivot-shift test at 0° and 15°, rectangular ACL reconstruction with quadriceps graft (3.9 ± 2.1 mm and 6.5 ± 1.7 mm, respectively) or BPTB graft (4.2 ± 1.8 mm and 6.7 ± 1.7 mm, respectively) showed a significantly lower anterior tibial translation when compared with round tunnel reconstruction (5.5 ± 2.1 mm and 7.9 ± 1.9 mm, respectively) (P = .03 and P = .041, respectively, at 0°; P = .042 and P = .046, respectively, at 15°).

CONCLUSIONS

Under simulated Lachman testing and pivot-shift testing, a reconstruction technique using a rectangular tunnel results in significantly lower anterior tibial translation at 0° and 15° of flexion in comparison to knees reconstructed with a hamstring SB graft using a round tunnel strategy.

CLINICAL RELEVANCE

ACL reconstruction with a rectangular tunnel and BPTB and quadriceps tendon might result in better anterior knee stability at low flexion angles than ACL reconstruction with hamstring SB graft and a round tunnel in the clinical setting.

Accuracy of a computer-assisted planning and placement system for anatomical femoral tunnel positioning in anterior cruciate ligament reconstruction

BACKGROUND

Femoral tunnel positioning is a difficult, but important factor in successful anterior cruciate ligament (ACL) reconstruction. Computer navigation can improve the anatomical planning procedure besides the tunnel placement procedure.

METHODS

The accuracy of the computer-assisted femoral tunnel positioning method for anatomical double bundle ACL-reconstruction with a three-dimensional template was determined with respect to both aspects for AM and PL bundles in 12 cadaveric knees.

RESULTS

The accuracy of the total tunnel positioning procedure was 2.7 mm (AM) and 3.2 mm (PL). These values consisted of the accuracies for planning (AM:2.9 mm; PL:3.2 mm) and for placement (about 0.4 mm). The template showed a systematic bias for the PL-position.

CONCLUSIONS

The computer-assisted templating method showed high accuracy for tunnel placement and has promising capacity for application in anatomical tunnel planning. Improvement of the template will result in an accurate and robust navigation system for femoral tunnel positioning in ACL-reconstruction.

Size comparison of ACL footprint and reconstructed auto graft

PURPOSE

The purpose of this study was to compare the size of native anterior cruciate ligament (ACL) footprints and the size of commonly used auto grafts. The hypothesis was that the reconstructed graft size with auto grafts might be smaller than the native ACL footprint.

METHODS

Fourteen non-paired human cadaver knees were used. The semitendinosus tendon (ST) and the gracilis (G) tendon were harvested and prepared for ACL grafts. Simulating an ST graft, the ST was cut in half. The bigger half was regarded as the antero-medial (AM) bundle, and the remaining half was regarded as the postero-lateral (PL) bundle. Simulating an ST-G graft, the bigger half of the ST and G were regarded as the AM bundle, and the smaller half of the ST was regarded as the PL bundle. Each graft diameter was measured, and the graft area was calculated. Simulating a rectangular bone-patella tendon-bone (BPTB) graft, a 10-mm wide BPTB graft was harvested and the area calculated. The ACL was carefully dissected, and the size of the femoral and tibial footprints was measured using Image J software (National Institution of Health).

RESULTS

The average areas of the ST, ST-G, and BPTB graft were 52.3 ± 7.3, 64.4 ± 9.2, and 32.7 ± 6.5 mm(2), respectively. The sizes of the native femoral and tibial ACL footprints were 85.4 ± 26.3 and 145.4 ± 39.8 mm(2), respectively. Only the ST-G graft showed no significant difference in graft size when compared with the femoral ACL footprint.

CONCLUSION

Only the ST-G auto graft was able to reproduce the native size of the ACL footprint on the femoral side. None of the auto grafts could reproduce the size of the tibial ACL footprint. For clinical relevance, ST-G graft is recommended in order to reproduce the native size of the ACL in anatomical ACL reconstruction with auto graft.