Cadaveric knee observation study for describing anatomic femoral tunnel placement for two-bundle anterior cruciate ligament reconstruction

Optimal tibial tunnel angulation for anatomical anterior cruciate ligament reconstruction using transtibial technique

Numerous studies have suggested that the primary cause of failure in transtibial anterior cruciate ligament reconstruction (ACLR) is often attributed to non-anatomical placement of the bone tunnels, typically resulting from improper tibial guidance. We aimed to establish the optimal tibial tunnel angle for anatomical ACLR by adapting the transtibial (TT) technique. Additionally, we aimed to assess graft bending angle (GBA) and length changes during in vivo dynamic flexion of the knee. Twenty knee joints underwent a CT scan and dual fluoroscopic imaging system (DFIS) to reproduce relative knee position during dynamic flexion. For the single-legged lunge, subjects began in a natural standing position and flexed the right knee beyond 90° When performing the lunge task, the subject supported the body weight on the right leg, while the left leg was used to keep the balance. The tibial and femoral tunnels were established on each knee using a modified TT technique for single-bundle ACLR. The tibial tunnel angulation to the tibial axis and the sagittal plane were measured. Considering that ACL injuries tend to occur at low knee flexion angles, GBA and graft length were measured between 0° and 90° of flexion in this study. The tibial tunnel angulated the sagittal plane at 42.8° ± 3.4°, and angulated the tibial axis at 45.3° ± 5.1° The GBA was 0° at 90° flexion of the knee and increased substantially to 76.4 ± 5.5° at 0° flexion. The GBA significantly increased with the knee extending from 90° to 0° (p < 0.001). The ACL length was 30.2mm±3.0 mm at 0° flexion and decreased to 27.5mm ± 2.8 mm at 90° flexion (p = 0.072). To achieve anatomic single-bundle ACLR, the optimal tibial tunnel should be angulated at approximately 43° to the sagittal plane and approximately 45° to the tibial axis using the modified TT technique. What's more, anatomical TT ACLR resulted in comparable GBA and a relatively constant ACL length from 0° to 90° of flexion. These findings provide theoretical support for the clinical application and the promotion of the current modified TT technique with the assistance of a robot to achieve anatomical ACLR.

Evaluation of the Angle Between the Long Axis of the Femoral Anterior Cruciate Ligament Footprint and Bony Morphology of the Knee: A Cadaveric Descriptive Study

Purpose

There have been numerous studies of the anterior cruciate ligament (ACL) anatomy, but few have focused on the long axis angle of the femoral ACL footprint. This study investigated the angle between the long axis of the femoral ACL footprint and the bony morphology of the knee.

Methods

This study is a cadaveric descriptive study. Thirty non-paired formalin-fixed knees of Japanese cadavers were used. Anteromedial (AM) and posterolateral (PL) bundles were identified according to the tension pattern differences during the complete range of motion of the knee. In the ACL femoral footprint, there is a fold between the mid-substance insertion site and fan-like extension fibers. After identifying AM and PL bundles of mid-substance fibers, the mid-substance and fan-like extension fibers were divided into those bundles and stained. We defined the line passing through the center of the AM and PL bundles as the long axis of the ACL. The center points of each of the four areas and the angle between the long axis of the ACL and the bony morphology of the knee were calculated using Image J software.

Results

The mean angle between the axis of the femoral shaft and the long axis of the ACL mid-substance insertion was 28.8 ± 12.2 degrees. The mean angle between the Blumensaat line and the long axis of the mid-substance was 54.2 ± 13.5 degrees.

Conclusion

The mean angle between the axis of the femoral shaft and the long axis of the femoral ACL footprint was approximately 29 degrees. There is a wide variation in the long axis of the femoral ACL footprint. To achieve better clinical results through a more anatomically accurate reconstruction, it can be beneficial to replicate the ACL femoral footprint along its native long axis.

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

Background

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

Purpose/Hypothesis

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

Study Design

Descriptive epidemiology study.

Methods

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

Results

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

Conclusion

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

3D visualization of the human anterior cruciate ligament combining micro-CT and histological analysis

PURPOSE

The study aimed to obtain a comprehensive 3D visualization of knee specimens, including the cruciate ligaments and corresponding femoral and tibial bone insertions using a non-destructive micro-CT method.

METHODS

Knee specimens were fixed in anatomical positions and chemically dehydrated before being scanned using micro-CT with a voxel size of 17.5 μm. RGBA (red, green, blue, alpha) transfer functions were applied to virtually colorize each structure. Following micro-CT scanning, the samples were rehydrated, decalcified, and trimmed based on micro-CT 3D reconstructions as references. Histological evaluations were performed on the trimmed samples. Histological and micro-CT images were registered to morphologically and densitometrically assess the 4-layer insertion of the ACL into the bone.

RESULTS

The output of the micro-CT images of the knee in extension and flexion allowed a clear differentiation of the morphologies of both soft and hard tissues, such as the ACL, femoral and tibial bones, and cartilage, and the subsequent creation of 3D composite models useful for accurately tracing the entire morphology of the ligament, including its fiber and bundle components, the trajectory between the femur and tibia, and the size, extension, and morphology of its insertions into the bones.

CONCLUSION

The implementation of the non-destructive micro-CT method allowed complete visualization of all the different components of the knee specimens. This allowed correlative imaging by micro-CT and histology, accurate planning of histological sections, and virtual anatomical and microstructural analysis. The micro-CT approach provided an unprecedented 3D level of detail, offering a viable means to study ACL anatomy.

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.

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.

No Differences In Clinical Outcomes Between Rectangular and Round Tunnel Techniques For Anterior Crucial Ligament Reconstruction

PURPOSE

To compare the clinical outcomes between conventional round tunnel and rectangular tunnel in anatomic anterior cruciate ligament (ACL) reconstruction.

METHODS

This was a retrospective comparative cohort study between March 2015 and September 2018. The primary ACL reconstructions using anteromedial portal technique with minimum of 2 years follow-up were enrolled for this study. The exclusion criteria were patients with revision ACL reconstruction, high tibial osteotomy, multiligament injuries, and associated fractures around the knee. Outcome measures included the subjective International Knee Documentation Committee score, Tegner activity score, knee laxity testing, and measurement of the centers of the femoral and tibial tunnels on postoperative computed tomography (CT) images.

RESULTS

Forty-seven patients with ACL reconstruction with rectangular tunnel (group 1) and 108 patients with ACL reconstructions with conventional rounded tunnel (group 2) were included consecutively. There were no significant differences between groups in terms of clinical scores or knee laxity, as well as femoral and tibial tunnel positions on CT. One patient in group 2 had ACL failure because of trauma and was treated with revision surgery. Two patients had incomplete tibial fracture, but they healed spontaneously and showed no residual laxity at final follow-up. The intraobserver and interobserver reliability for the radiological measurements ranged from 0.78 to 0.86.

CONCLUSIONS

There were no differences in radiological and clinical results between rectangular tunnel group and conventional round tunnel group for arthroscopic ACL reconstruction. ACL reconstruction with a rectangular tunnel could be considered as a reliable technique, but care should be taken during tunnel establishment because of risk of fractures and malposition of rectangular tunnel.

Significance of the broad non-bony attachments of the anterior cruciate ligament on the tibial side

Knowledge of the anatomy of the anterior cruciate ligament (ACL) is important to understand the function and pathology of the knee joint. However, on the tibial side of ACL, its structural relationships with the articular cartilage and lateral meniscus remain unclear. Furthermore, conventional research methods are limited to analyzing the bone attachments. We provide a comprehensive, three-dimensional anatomical description of the tibial side of the ACL that questions the principle that “a ligament is necessarily a structure connecting a bone to another bone.” In our study, 11 knees from 6 cadavers were used for macroscopic anatomical examinations, serial-section histological analyses, and three-dimensional reconstructions. The attachments of the tibial side of ACL consisted of attachments to the bone (102.6 ± 27.5 mm²), articular cartilage (40.9 ± 13.6 mm²), and lateral meniscus (6.5 ± 4.6 mm²), suggesting that the ACL has close structural relationships with the articular cartilage and lateral meniscus. Our study demonstrates that the tibial side of the ACL is not attached to the bone surface only and provides new perspectives on ligamentous attachments. Considering its attachment to the articular cartilage would enable more accurate functional evaluations of the mechanical tensioning of the ACL.

Transtibial versus independent femoral tunnel drilling techniques for anterior cruciate ligament reconstruction: evaluation of femoral aperture positioning

Background

Femoral tunnel can be drilled through tibial tunnel (TT), or independent of it (TI) by out-in (OI) technique or by anteromedial (AM) technique. No consensus has been reached on which technique achieves more proper femoral aperture position because there have been evolving concepts in the ideal place for femoral aperture placement. This meta-analysis was performed to analyze the current literature comparing femoral aperture placement by TI versus TT techniques in ACL reconstruction.

Methods

We performed a comprehensive systematic review and meta-analysis of English-language literature in PubMed, Cochrane, and Web of Science databases for articles comparing femoral aperture placement by TI versus TT techniques with aperture position assessed by direct measurement or by postoperative imaging, PXR and/or CT and/or MRI.

Results

We included 55 articles with study population of 2401 knees of whom 1252 underwent TI and 1149 underwent TT techniques. The relevant baseline characteristics, whenever compared, were comparable between both groups. There was nonsignificant difference between TI and TT techniques in the distance from aperture center to footprint center and both techniques were unable to accurately recreate the anatomic footprint position. TI technique significantly placed aperture at more posterior position than TT technique. TI technique significantly lowered position of placed aperture perpendicular to Blumensaat’s line (BL) than TT technique, and modifications to TT technique had significant effect on this intervention effect. Regarding sagittal plane aperture placement along both AP anatomical axis and BL, there was nonsignificant difference between both techniques.

Conclusion

Modifications to TT technique could overcome limitations in aperture placement perpendicular to BL. The more anterior placement of femoral aperture by TT technique might be considered, to some extent, a proper position according to recent concept of functional anatomical ACL reconstruction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03040-5.

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.

The morphology of the femoral footprint of the anterior cruciate ligament changes with aging from a large semicircular shape to a small flat ribbon-like shape

PURPOSE

Compare the differences in the morphology of the ACL femoral footprint between the cadavers of the young and elderly in consideration of the degenerative physiological process that occurs with aging.

METHODS

The femoral footprint of the ACL was dissected in 81 knees of known gender and age (45 male/36 female). They were divided into four groups by age and gender, establishing 50 years as the cut-off point to divide patients by age. Three observers analyzed the femoral footprint dissections, and the shapes were described and classified. The area and morphometric characteristics of the femoral insertion of the ACL were determined and these were compared between genders and age groups.

RESULTS

The femoral footprint of the ACL from the cadavers of males younger than 50 years of age presented a semicircular morphology in 90% of the cases. In males aged more than 50 years, a ribbon-like morphology was found in 96% of the cases. In women less than 50 years old, the semicircular morphology was observed in 93.7% of the cases. In women aged over 50 years old, the ribbon-like morphology was found in 95% of the cases. A significant difference was observed between the prevalence rates of the morphologies, area size and measurements of the younger and older groups (p < 0.001 for both genders).

CONCLUSIONS

The femoral insertion of the ACL presents variations in its morphology, area and morphometric characteristics over time. It goes from a large semicircular shape that almost contacts the posterior articular cartilage to a smaller, flattened ribbon-like shape that moves away from the edge of the articular cartilage. It is bounded anteriorly by the lateral intercondylar ridge. These findings should be considered to avoid employing reconstruction techniques in which femoral tunnels with oval or rectangular shapes are used in patients under 50 years of age because they do not correspond to the morphology of the femoral insertion of the ACL in this age group.

No Difference in Ligamentous Strain or Knee Kinematics Between Rectangular or Cylindrical Femoral Tunnels During Anatomic ACL Reconstruction With a Bone-Patellar Tendon-Bone Graft

BACKGROUND

As our understanding of anterior cruciate ligament (ACL) anatomy has evolved, surgical techniques to better replicate the native anatomy have been developed. It has been proposed that the introduction of a rectangular socket ACL reconstruction to replace a ribbon-shaped ACL has the potential to improve knee kinematics after ACL reconstruction.

PURPOSE

To compare a rectangular femoral tunnel (RFT) with a cylindrical femoral tunnel (CFT) in terms of replicating native ACL strain and knee kinematics in a time-zero biomechanical anatomic ACL reconstruction model using a bone-patellar tendon-bone (BTB) graft.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 16 fresh-frozen, human cadaveric knees were tested in a 5 degrees of freedom, computed tomography-compatible joint motion simulator. Knees were tested with the ACL intact before randomization to RFT or CFT ACL reconstruction using a BTB graft. An anterior translation load and an internal rotation moment were each applied at 0°, 30°, 60°, and 90° of knee flexion. A simulated pivot shift was performed at 0° and 30° of knee flexion. Ligament strain and knee kinematics were assessed using computed tomography facilitated by insertion of zirconium dioxide beads placed within the substance of the native ACL and BTB grafts.

RESULTS

For the ACL-intact state, there were no differences between groups in terms of ACL strain or knee kinematics. After ACL reconstruction, there were no differences in ACL graft strain when comparing the RFT and CFT groups. At 60° of knee flexion with anterior translation load, there was significantly reduced strain in the reconstructed state ([mean ±standard deviation] CFT native, 2.82 ± 3.54 vs CFT reconstructed, 0.95 ± 2.69; RFT native, 2.77 ± 1.71 vs RFT reconstructed, 1.40 ± 1.76) independent of the femoral tunnel type. In terms of knee kinematics, there were no differences when comparing the RFT and CFT groups. Both reconstructive techniques were mostly effective in restoring native knee kinematics and ligament strain patterns as compared with the native ACL.

CONCLUSION

In the time-zero biomechanical environment, similar graft strains and knee kinematics were achieved using RFT and CFT BTB ACL reconstructions. Both techniques appeared to be equally effective in restoring kinematics associated with the native ACL state.

CLINICAL RELEVANCE

These data suggest that in terms of knee kinematics and graft strain, there is no benefit in performing the more technically challenging RFT as compared with a CFT BTB ACL reconstruction.

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

BACKGROUND

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

PURPOSE

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

STUDY DESIGN

Controlled laboratory study.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

A Systematic Review of Tissue Engineering Scaffold in Tendon Bone Healing in vivo

Background: Tendon-bone healing is an important factor in determining the success of ligament reconstruction. With the development of biomaterials science, the tissue engineering scaffold plays an extremely important role in tendon-bone healing and bone tissue engineering. Materials and Methods: Electronic databases (PubMed, Embase, and the Web of Science) were systematically searched for relevant and qualitative studies published from 1 January 1990 to 31 December 2019. Only original articles that met eligibility criteria and evaluated the use of issue engineering scaffold especially biomaterials in tendon bone healing in vivo were selected for analysis. Results: The search strategy identified 506 articles, and 27 studies were included for full review including two human trials and 25 animal studies. Fifteen studies only used biomaterials like PLGA, collage, PCL, PLA, and PET as scaffolds to repair the tendon-bone defect, on this basis, the rest of the 11 studies using biological interventions like cells or cell factors to enhance the healing. The adverse events hardly ever occurred, and the tendon bone healing with tissue engineering scaffold was effective and superior, which could be enhanced by biological interventions. Conclusion: Although a number of tissue engineering scaffolds have been developed and applied in tendon bone healing, the researches are mainly focused on animal models which are with limitations in clinical application. Since the efficacy and safety of tissue engineering scaffold has been proved, and can be enhanced by biological interventions, substantial clinical trials remain to be done, continued progress in overcoming current tissue engineering challenges should allow for successful clinical practice.

Clinical study of anatomical ACL reconstruction using a rounded rectangular dilator

Background

The aim of this study was that to compare clinical results between the rounded rectangular femoral tunnel ACL reconstruction (RFTR) and the conventional round femoral tunnel ACL reconstruction using a hamstring tendon. The hypothesis was that ACL reconstruction performed using the rounded rectangular dilator technique was better than that performed using the conventional round femoral tunnel technique in terms of clinical results and bone tunnel enlargement.

Methods

We conducted retrospective study. After exclusions, 40 patients were included in the conventional anatomical single-bundle ACL reconstruction (ASBR) group and 40 patients were included in the RFTR group. The evaluation items were knee stability, Lysholm knee score, IKDC subjective score at 2 years after surgery and bone tunnel enlargement.

Results

The RFTR group had a larger femoral tunnel area (average area, 53.1 ± 4.0 mm² vs. 46.1 ± 7.0 mm²; P < 0.01), better anteroposterior stability, and higher Lysholm scores than the ASBR group (average side-to-side difference for anterior tibial translation, 0.6 ± 0.8 mm vs. 1.6 ± 1.4 mm; P < 0.01; average Lysholm score, 98.5 ± 2.1 vs. 97.5 ± 3.5; P < 0.01). Further, bone tunnel enlargement ratio was significantly lower in the RFTR group (73 ± 38% vs. 107 ± 41%; P < 0.01).

Conclusions

We designed and developed an original rounded rectangular dilator to perform a novel ACL surgery. This technique can create a larger bone tunnel and improve clinical results than the conventional round anatomical single-bundle ACL reconstruction.

The Chinese ACL injury population has a higher proportion of small ACL tibial insertion sizes than Western patients

PURPOSE

The study purpose is to characterize the sizes of the anterior cruciate ligament (ACL) insertion site and intercondylar notch in Chinese patients undergoing ACL surgery. The findings will provide a reference for individualized clinical treatment of ACL rupture.

METHODS

For this study, 137 patients (102 males, 35 females) with an average age of 30.3 ± 9.5 years (range 14-52 years) undergoing ACL reconstruction were included. The tibial ACL insertion site length and width and the intercondylar notch width were measured on MRI and arthroscopically using a ruler. Descriptive statistics of the patients, the distribution of the measurements and the differences between males and females were calculated.

RESULTS

The ACL tibial insertion size and intercondylar notch width in Chinese patients with ACL injuries, as obtained by MRI and intra-operatively, exhibited significant individual variability. The tibial ACL insertion site had a mean length of 13.5 ± 2.1 mm and width of 10.9 ± 1.5 mm as measured on MRI and a mean length of 13.3 ± 2.1 mm and width of 11.0 ± 1.6 mm as measured intra-operatively. The mean intercondylar notch width was 15.2 ± 2.4 mm on MRI and the mean length was 15.0 ± 2.5 mm intra-operatively. The inter-rater reliability between MRI and intra-operative measurements confirmed that the two methods were consistent. In 65.7% of individuals, the ACL tibial insertion length was < 14 mm.

CONCLUSION

The distribution of tibial footprint size in Chinese patients is different from that in Western populations. There is a higher proportion of subjects with a tibial footprint size < 14 mm among Chinese patients with ACL injury. Therefore, great care should be taken when treating this population with the double-bundle technique or larger graft options. Level of evidence IV.

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

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

Biomechanical Effects of Additional Anterolateral Structure Reconstruction With Different Femoral Attachment Sites on Anterior Cruciate Ligament Reconstruction

BACKGROUND

Recently reported anterolateral structure reconstructions (ALSRs) to augment intra-articular anterior cruciate ligament reconstruction (ACLR) use various femoral attachment sites, and their biomechanical effects are still unknown.

HYPOTHESIS

ALSR concomitant with ACLR would control anterolateral rotational instability better than ACLR alone, and if ALSR had different femoral attachment sites, there would be different effects on its control of anterolateral rotational instability.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve fresh-frozen hemipelvis lower limbs were included. Anterior tibial translation during the Lachman test and tibial acceleration during the pivot-shift test were measured with a 3-dimensional electromagnetic measurement system in situations with the (1) ACL and ALS intact, (2) ACL and ALS cut, (3) ALSR without ACLR (ALSR alone), (4) ACLR without ALSR (ACLR alone), and (5) ALSR with ACLR. Three femoral attachment sites were used for ALSR: F1, 2 mm anterior and 2 mm distal to the lateral epicondyle; F2, 4 mm posterior and 8 mm proximal to the lateral epicondyle; and F3, over-the-top position for the lateral extra-articular tenodesis. The Steel test and Wilcoxon signed rank test were used for statistical analysis.

RESULTS

Anterior tibial translation during the Lachman test in the ACL and ALS-cut state was significantly larger than it was in the ACL and ALS-intact state, while its difference disappeared after ACLR. As for the pivot-shift test, additional ALSR with F2 to ACLR significantly decreased the acceleration (P = .046), although additional ALSR with F1 and F3 showed no significant effect.

CONCLUSION

ALSR with the femoral attachment site 4 mm posterior and 8 mm proximal to the lateral epicondyle in addition to ACLR played a role in reducing anterolateral rotational instability the most effectively among the measured attachment sites.

CLINICAL RELEVANCE

The present data will contribute to determine the appropriate femoral attachment site for ALSR to better control anterolateral rotational instability after ACL reconstruction.

New Calibrator with Points Distributed Conical Helically for Online Calibration of C-Arm

To improve the accuracy of calibration of C-arm, and overcome the space limitation in surgery, we proposed a new calibrator for online calibration of C-arm. After the image rectification by a polynomial fitting-based global correction method, the C-arm was assumed as an ideal pinhole model. The relationships between two kinds of spatial calibration errors and the distribution of fiducial points were studied: the performance of FRE (Fiducial Registration Error) and TRE (Target Registration Error) were not consistent, but both were best at the 12 marked points; the TRE decreased with the increase of the uniformity of calibration points distribution, and with the decrease of the distance between the target point and the center of calibration points. A calibrator with 12 fiducial points conical helically distributed, which could be placed on the knee, was an attractive option. A total of 10 experiments on C-arm calibration accuracy were conducted and the mean value of mapping error was 0.41 mm. We designed an ACL reconstruction navigation system and carried out specimen experiments on 4 pairs of dry femur and tibia. The mean accuracy of navigation system was 0.85 mm, which is important to the tunnel positioning for ACL reconstruction.

Comparison of Graft Length Changes During Knee Motion Among 5 Different Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction Approaches: A Biomechanical Study

Background:

In several anatomic single-bundle anterior cruciate ligament (ACL) reconstruction (ASB-ACLR) procedures, the femoral and tibial tunnel apertures are created at different locations within the native ACL attachment area.

Hypothesis:

Graft length changes during knee motion will be different among ASB-ACLR procedures with different femoral and tibial tunnel aperture locations.

Study Design:

Controlled laboratory study.

Methods:

A total of 12 cadaveric knees were used in this study. In each knee, 4 and 3 thin tunnels were created within the ACL attachment area on the femur and the tibia, respectively. Using 1 of 5 different combinations of femoral and tibial tunnel aperture location, 5 ASB-ACLRs were performed on each knee. In each reconstruction approach, a strong thread was used in place of the tendon graft, and the tibial graft end was tethered to a custom-made isometric positioner at 0° of knee flexion, with an approximately 12-N load applied to the thread. Then, each specimen underwent 5 cycles of knee flexion-extension motion in a range between 0° and 120°, and graft length changes were determined for each SB-ACLR approach.

Results:

The length changes of the graft were significantly different among the 5 ASB-ACLRs. The maximum length change values of the 3 grafts that were implanted between the femoral and tibial centers of the posterolateral bundle attachments or implanted into the femoral tunnel created at the center of the fanlike extension fiber attachment were significantly greater than those of the graft implanted between the centers of the anteromedial bundle attachments (P < .0001) and of the graft implanted between the centers of the whole ACL attachments (P < .0001).

Conclusion:

The length changes of the graft during knee motion were significantly different among the 5 ASB-ACLR approaches, even though all of the tunnel apertures were created within the femoral and tibial attachments of the native ACL.

Clinical Relevance:

The grafts in the first 3 graft locations may be so relaxed during knee flexion that they cannot resist anterior drawer loads exerted on the tibia.

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

BACKGROUNDS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comparison of three approaches for femoral tunnel during double-bundle anterior cruciate ligament reconstruction: A case controlled study

BACKGROUND

It is still controversial whether which femoral tunnel creation technique is best during anterior cruciate ligament reconstruction (ACLR). We aimed to clarify the features of three different techniques based on the femoral tunnel position created with the same tunnel-creating concept and the measurement data.

METHODS

The femoral tunnel of double-bundle (DB) ACLR was created using the behind-remnant approach in a remnant preserved manner following the policy of our institute. The trans-tibial approach (TT) was applied for all primary ACL injured cases until December 2012. The trans-portal approach (TP) was applied from January to September 2013, and the outside-in approach (OI) was indicated from October 2013 to March 2014. We compared the femoral tunnel aperture positions with the postoperative three-dimensional computed tomography (3D-CT). Additionally, the femoral tunnel length and the septum distance of each anteromedial (AM) and posterolateral (PL) tunnel were analyzed.

RESULTS

The AM tunnel aperture position of TT was significantly higher and shallower than that of TP in knee flexion position. The femoral tunnel length of TP was significantly shorter than that of TT and OI. The septum between each tunnel of OI trended wider than that of TT and TP.

CONCLUSIONS

The AM tunnel aperture position of TT runs the risk of a high and shallow position. TP runs the risk of insufficiently short tunnel length. It is important to apply each method flexibly to each case because no single best approach was found.

Tibiofemoral joint contact area and stress after single-bundle anterior cruciate ligament reconstruction with transtibial versus anteromedial portal drilling techniques

Background

During single-bundle ACLR, femoral tunnel location plays an important role in restoring the intact knee mechanisms, whereas malplacement of the tunnel was cited as the most common cause of knee instability. The objective of this study is to evaluate, objectively, the tibiofemoral contact area and stress after single-bundle (SB) anterior cruciate ligament reconstruction (ACLR) with femoral tunnel positions drilled by transtibial (TT) or anteromedial (AM) portal techniques.

Methods

Seven fresh human cadaveric knees underwent ACLR by the use of TT or AM portal techniques in a randomized order. These specimens were reused for ACL-R (TT and AM). The tibiofemoral contact area and stresses were gauged by an electronic stress-sensitive film inserted into the joint space. The knee was under the femoral axial compressive load of 1000 N using a biomechanics testing machine at 0°, 10°, 20°, and 30° of flexion. Three conditions were compared: (1) intact ACL, (2) ACLR by the use of the TT method, and (3) ACLR by the use of the AM portal method.

Results

Compared with AM portal ACL-reconstructed knees, a significantly decreased tibiofemoral contact area on the medial compartment was detected in the TT ACL-reconstructed knees at 20°of knee flexion (P = .047). Compared with the intact group, the TT ACLR group showed a higher mean stress at 20° and 30° of flexion on the medial compartments (P = .001, P = .003, respectively), while the AM portal ACLR group showed no significant differences at 30° of flexion (P = .073). The TT ACLR group also showed a higher mean maximum stress at 20° of flexion on the medial compartments (P = .047), while the AM portal ACLR group showed no significant differences at this angle(P = .319).

Discussion

The alternation of the tibiofemoral joint contact area and stress in reconstructed knees may be caused by the mismatch of the tibiofemoral joint during knee movement procedures compared with intact knees.

Conclusions

SB ACLR by the use of the AM portal method and TT method both alter the tibiofemoral contact area and stress when compared with the intact knee. When compared with the TT technique, ACLR by the AM portal technique more closely restores the intact tibiofemoral contact area and stress at low flexion angles.

Optimal Condition to Create Femoral Tunnel Considering Combined Influence of Knee Flexion and Transverse Drill Angle in Anatomical Single-Bundle ACL Reconstruction Using Medial Portal Technique: 3D Simulation Study

There has been no previous study using three-dimensional (3D) measurement on femoral tunnel characteristics according to the combined influence of various flexion angles of knee and transverse drill angles in single-bundle ACL reconstruction with transportal technique. The purpose of this study was to determine optimal condition of knee flexion angle and transverse drill angle to create secure femoral tunnel in single-bundle ACL reconstruction with transportal technique considering tunnel length, tunnel wall breakage, and graft bending angle. This study was conducted using simulation of 3D computed tomography of thirty subjects. Three variables of femoral tunnel changed according to combined influence of four flexion angles of knee and three transverse drill angles were measured: tunnel length, wall breakage, and graft bending angle. There was no case of short femoral tunnel less than 25 mm at 120° and 130° of flexion. There was no case of breakage of femoral tunnel at 120° of flexion with maximum transverse drill angle (MTA) and MTA-10° and at 130° of flexion. Considering effect on graft bending angle, decrease of flexion angle and transverse drill angle could be appropriate in creating femoral tunnel. Increased flexion angle and transverse drill angle secured femoral tunnel having sufficiently long length without wall breakage. However, avoiding excessive flexion angle and maximum transverse drill angle could be recommended because they tended to cause more acute graft bending angle.

Descriptive anatomy of the anterior cruciate ligament femoral insertion

Objective

To evaluate the morphology of the anterior cruciate ligament (ACL) femoral insertion in order to describe its anatomical features and insertion site location, with the aim of verifying if the ACL femoral insertion has individual characteristics and to provide information for appropriate femoral tunnel placement on anatomic ACL reconstruction.

Methods

Sixteen knees obtained from amputations were studied. The ACL femoral bundles and insertion shape were observed macroscopically, and the ligaments insertion length and thickness were measured with a digital caliper. The distances between the limits of the ligament to the articular cartilage, and the measurement of the area of insertion were checked using ImageJ software.

Results

The ACL femoral insertion site was eccentric, closer to the deep condyle cartilage. In ten knees (62.5%), the ACL femoral insertion was oval; the mean length of the insertion was 16.4 mm, varying from 11.3 to 19.3 mm, the mean thickness varied from 7.85 to 11.23 mm, and the mean area of the insertion was 99.7 mm², varying from 80.9 a 117.2 mm². The mean distances between the limits of the ligament to the superficial, deep, and inferior articular cartilage were 9.77 ± 1.21, 2.60 ± 1.20, and 1.86 ± 1.15 mm, respectively.

Conclusion

There was a 30% to 40% difference between the minimum and maximum results of measurements of ACL femoral insertion length, thickness, and area demonstrating an important individual variation. The insertion site was eccentric, closer to the deep cartilage of the lateral femoral condyle.

[Anatomical study of anterior cruciate ligament and its effect on reconstruction technique]

Objective

To summarize the current research progress of anterior cruciate ligament (ACL) anatomy, and discuss its effect on the reconstruction technique.

Methods

The literature concerning ACL anatomy and reconstruction at home and abroad was extensively reviewed and summarized.

Results

The anatomy and morphology of ACL has gained new recognition in recent years, and the "Ribbon-like" ACL has gradually been paid attention to by researchers. In present researches, it seems the "Ribbon-like" anatomy theory has advantages in theory when compared with the previous anatomy theory. It is more in line with the anatomy and isometric reconstruction.

Conclusion

The understanding of ACL anatomy guided the development of ACL reconstruction. The "Ribbon-like" ACL anatomy theory is the different understanding of the anatomy theory, which remains controversy. The "Ribbon-like" reconstruction maybe has more advantages in theory, but further study is needed.

Influence of knee flexion angle and transverse drill angle on creation of femoral tunnels in double-bundle anterior cruciate ligament reconstruction using the transportal technique: Three-dimensional computed tomography simulation analysis

BACKGROUND

The purpose of this study was to find appropriate flexion angle and transverse drill angle for optimal femoral tunnels of anteromedial (AM) bundle and posterolateral (PL) bundle in double-bundle ACL reconstruction using transportal technique.

METHODS

Thirty three-dimensional knee models were reconstructed. Knee flexion angles were altered from 100° to 130° at intervals of 10°. Maximum transverse drill angle (MTA), MTA minus 10° and 20° were set up. Twelve different tunnels were determined by four flexion angles and three transverse drill angles for each bundle. Tunnel length, wall breakage, inter-tunnel communication and graft-bending angle were assessed.

RESULTS

Mean tunnel length of AM bundle was >30mm at 120° and 130° of flexion in all transverse drill angles. Mean tunnel length of PL bundle was >30mm during every condition. There were ≥1 cases of wall breakage except at 120° and 130° of flexion with MTA for AM bundle. There was no case of wall breakage for PL bundle. Considering inter-tunnel gap of >2mm without communication and obtuse graft-bending angle, 120° of flexion and MTA could be recommended as optimal condition for femoral tunnels of AM and PL bundles.

CONCLUSION

Flexion angle and transverse drill angle had combined effect on femoral tunnel in double-bundle ACL reconstruction using transportal technique. Achieving flexion angle of 120° and transverse drill angle close to the medial femoral condyle could be recommended as optimal condition for femoral tunnels of AM and PL bundles to avoid insufficient tunnel length, wall breakage, inter-tunnel communication and acute graft-bending angle.

Editorial Commentary: The Ribbon Theory. Another Quantum Leap? The Anterior Cruciate Ligament Is Twisted and in Fact a Flat Structure. Or not?

Is the double bundle structure of the anterior cruciate ligament (ACL) a myth? Derotation untwists the ACL and results in a flat ribbon structure. However, other researchers dispute this theory and revealed 2 distinct bundles separated by a synovial septum. The answer is simple: we do not know and the evidence is conflicting.

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 Bow Tie Shape of the Anterior Cruciate Ligament as Visualized by High-Resolution Magnetic Resonance Imaging

BACKGROUND

Although numerous studies have examined the anatomic characteristics of the anterior cruciate ligament (ACL), its actual shape remains unclear.

PURPOSE

To determine the average shape of the ACL by analyzing its cross section through the use of high-resolution magnetic resonance imaging (MRI) data.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The study included 96 MRIs, conducted using a 3.0-T magnet, to analyze the shape of the ACL. Three-dimensional, curved multiplanar reconstruction was used to obtain cross sections at 7 points (femoral insertion; midsubstance 1, 2, 3, 4, and 5 from the femoral side to the tibial side; and tibial insertion). The width and thickness of cross sections were measured by 2 independent observers, and the ratio of width to thickness was calculated to determine the proportions of each cross section. The 7 cross sections were accumulated and standardized to generate an average model through the use of image analysis software developed by the authors.

RESULTS

The mean ± SD width (femoral insertion, 17.02 ± 2.17 mm; tibial insertion, 17.33 ± 2.03 mm) and thickness (femoral insertion, 11.03 ± 1.75 mm; tibial insertion, 10.09 ± 1.70 mm) of both insertions were significantly larger than those of midsubstance 4 (width, 9.99 ± 1.87 mm; thickness, 6.53 ± 1.25 mm) ( P < .001). The mean ratios of width to thickness of the 7 cross sections from femoral insertion to tibial insertion were 1.57 ± 0.23, 3.36 ± 0.57, 3.07 ± 0.81, 2.18 ± 0.54, 1.56 ± 0.32, 2.16 ± 0.48, and 1.75 ± 0.28, respectively. The shape of the cross section at midsubstance 4 was an oval isthmus, which was the most narrow and well-balanced shape. It was transformed into a wide band at midsubstance 1 and 5. The shape of the femoral insertion was semicircular, with its anterior side slightly straight and its posterior side convex. The tibial insertion was kidney bean-shaped.

CONCLUSION

On 3.0-T MRI, the ACL has a "bow tie" shape, including an oval isthmus, with a semicircular femoral insertion and kidney bean-shaped tibial insertion.

CLINICAL RELEVANCE

The measurement method will allow surgeons to quantitatively diagnose partial injuries of the ACL using a noninvasive system in actual patients.

Effects of different femoral tunnel positions on tension changes in anterolateral ligament reconstruction

PURPOSE

Several kinds of anterolateral ligament (ALL) reconstructions to augment intra-articular anterior cruciate ligament reconstruction to better control anterolateral rotational instability (ALRI) have been reported. However, the optimal femoral attachment site for ALL reconstruction is still unclear. The purpose of this study was to investigate the effects of different femoral attachment sites on the tension changes through knee motions in different situations in order to determine a recommended femoral attachment site for ALL reconstruction.

METHODS

Six fresh-frozen cadaveric knees were included. ALL reconstructions were performed with three different femoral attachment sites (F1: 2 mm anterior and 2 mm distal to the lateral epicondyle, F2: 4 mm posterior and 8 mm proximal to the lateral epicondyle and F3: position for the lateral extra-articular tenodesis). The graft tension changes were measured by a graft tensioning system during knee flexion-extension and manual maximum internal/external tibial rotation in the following situations: (1) intact, (2) ALL cut, (3) ALL and ACL cut and (4) ALL cut and ACL reconstructed. Effects of the different femoral attachment sites, the route superficial or deep to the LCL, and the situations of (1) to (4) were calculated via repeated-measures analysis of variance.

RESULTS

The tension of F1 was higher in flexion and lower in extension, whereas the tension of F2 and F3 was higher in extension and lower in flexion. F2 showed the smallest tension change. Situations of (1) to (4) did not affect tension changes. The graft tension became higher with internal rotation and lower with external rotation regardless of femoral attachment sites or situations.

CONCLUSION

With F2-4 mm posterior and 8 mm proximal to the lateral epicondyle-the reconstructed ALL had the least tension change with only a slight increase in tension as the knee extended. This result indicates that F2 is recommended for ALL reconstruction to better control ALRI, which will help determine the optimal femoral tunnel position for ALL reconstruction.

Inter- and Intrarater Reliability of the Femoral Tunnel Clock-Face Grading System During Anterior Cruciate Ligament Reconstruction

PURPOSE

To determine the inter- and intrarater reliability of the clock-face grading system as used by 3 fellowship-trained sports medicine surgeons.

METHODS

Arthroscopic video was taken of the femoral tunnel placement during 20 consecutive anterior cruciate ligament (ACL) reconstructions performed by 2 surgeons. All femoral tunnels were created using a medial portal technique. The video was taken using a 30° arthroscope placed in the lateral portal and showed the femoral tunnel as well as the remainder of the femoral notch, the posterior cruciate ligament, and the menisci for orientation. Three fellowship-trained sports medicine surgeons were asked to review the videos and assign an o'clock position to the femoral tunnel from the 9 to the 3 o'clock positions in "half-hour" increments. They were also asked to review the videos again 6 months later to determine intrarater reliability. Inter-rater reliability was evaluated using the intraclass correlation coefficient (ICC) 2-way mixed effect model with absolute agreement. The Spearman rank-order correlation coefficient (r) was applied to evaluate intrarater reliability.

RESULTS

The inter-rater reliability as measured by the ICC revealed poor agreement between the 3 surgeons (ICC = 0.204, 95% confidence interval = -0.015 to 0.491, F = 2.8, P = .004). The intrarater reliability at a 6-month interval was found to be moderate (r's = .43, P = .004).

CONCLUSIONS

The inter-rater reliability of the clock-face femoral tunnel grading system was found to be poor among fellowship-trained sports medicine surgeons whereas the intrarater reliability was found to be moderate. The utility of the femoral tunnel clock-face grading system may be compromised by suboptimal inter- and intrarater reliability, making it less useful as a tool of communication between surgeons.

LEVEL OF EVIDENCE

Level IV, case series with poor reference standard.

Comparing Dimensions of Four-Strand Hamstring Tendon Grafts with Native Anterior and Posterior Cruciate Ligaments

Background. The aim of the study was to evaluate whether or not there was any incompatibility between four-strand hamstring tendons taken from the same knee and the dimensions of the ACL and PCL. Methods. 15 fresh frozen cadaver hamstrings were prepared as four-strand grafts and measurements made of the ACL and PCL circumferences in the midsection were made in the narrowest part of the midsection. The cross-section areas and diameters were calculated with geometric calculations used to measure the cross-sectional area of cylinders. Accepting that the geometric insertions were elliptical, the length, width, and area were calculated for entry areas. Results. A significant relationship at 96.2% was determined between the ACL mid and the hamstring diameter. A significant relationship at 96.7% was determined between the ACL and the hamstring mid area. A significant relationship at 96.4% was determined between the PCL mid and the hamstring diameter. A significant relationship at 95.7% was determined between the PCL and the hamstring mid area. Conclusion. For the reconstruction of ACL and PCL, it was determined that there is less incompatibility between the four-strand hamstring tendons taken from the same knee and the dimensions of the midsection PCL compared to the ACL dimensions.

Synovial C-Shaped Tibial Footprint of the Anterior Cruciate Ligament

Background:

Although numerous anatomic studies about the anterior cruciate ligament (ACL) structure and attachments have been performed, these studies have not reached consensus on the ACL footprint.

Purpose:

To investigate the existing controversy regarding the morphology of the tibial ACL insertion (footprint) and confirm histologically that the tibial ACL footprint is not completely filled with ligament tissue.

Study Design:

Descriptive laboratory study.

Methods:

The tibial ACL footprint was dissected from 20 different fresh-frozen cadaveric knees (all males; mean age, 68.8 ± 5.4 years [range, 55-80 years]; mean weight, 78 ± 6.6 kg [range, 45-93 kg]). Two knees, 1 with severe osteoarthritis and 1 with previous knee surgery, were excluded. The tibial ACL insertion was observed, and this area was longitudinally divided into 4 parallel slices (0%-25%, 25-50%, 50%-75%, and 75%-100%), embedded in paraffin wax, and stained with hematoxylin-eosin, alcian blue, and picrosirius-polarization. The specimens were measured using a microscope to determine the distances from the anterior to the posterior border of the ACL ligament tibial insertion and the distance from the posterior border to the end of the ligament fibers of the ACL ligament tibial insertions.

Results:

The 18 evaluated knee specimens confirmed the finding of a C-shaped tibial insertion of the ACL. The measurements showed that the ligament (vertical parallel collagen fibers) occupied only 30.8% of the complete insertion. The remaining area was filled with synovial tissue, demonstrating histologically the “C” shape.

Conclusion:

This study confirms macroscopically the C-shaped tibial insertion of the ACL and shows histologically that synovial tissue is an indirect insertion filling the major part of the footprint.

Clinical Relevance:

This anatomic study suggests a different shape of the ACL tibial footprint, which may be useful for new perspectives regarding ACL reconstruction surgery research.

An anatomical investigation of clock face landmarks around the glenoid for shoulder arthroscopy orientation

BACKGROUND

For shoulder arthroscopy, few anatomical landmarks are available and inexperienced surgeons tend to be adrift due to the limited visual field of the scope. The purpose of this study was to demonstrate the useful landmarks around the glenoid for accurate orientation, and also the safe distance to avoid suprascapular nerve injury during surgical procedures around the glenoid.

METHODS

In 15 human solution-fixed cadavers, a cross-section of the shoulder joint on the labrum surface was created. The positions of the principal anatomical structures surrounding the glenoid were marked on the labrum and measured using our clock face indication system. In 9 shoulders the distances from the labral surface to the spinoglenoid notch were recorded. As an indicator of the scapula size, the distances between the superior and inferior angles of the scapula were also measured.

RESULTS

The average landmark positions in the right shoulder were as follows: center of the attachment of the long tendon 11:59, anterior edge of the supraspinatus 11:59, posterior edge of the base of the coracoid process 12:13, superior edge of the subscapularis 1:03, anterior edge of the base of the coracoid process 1:25, inferior edge of the subscapularis 5:27, inferior edge of the teres minor 6:21, border of the infraspinatus and teres minor 7:43, center of the scapula spine 10:06, border of the supra and infraspinatus 10:27. The average distance from the labral surface to the spinoglenoid notch was 23.17 mm, and that from the superior to inferior angle was 144.93 mm. The Pearson correlation coefficient for these distances was 0.007.

CONCLUSIONS

The locations of anatomical landmarks surrounding the glenoid were reliably demonstrated using our clock face indication system. The expected distance from the labral surface to the suprascapular nerve was approximately 23 mm, irrespective of the size of the scapula.

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

BACKGROUND

The femoral insertion of the anterior cruciate ligament (ACL) has direct and indirect fiber types located within the respective high (anterior) and low (posterior) regions of the femoral footprint.

HYPOTHESIS

The fibers in the high region of the ACL footprint carry more force and are more isometric than the fibers in the low region of the ACL footprint.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen cadaveric knees were mounted to a robotic manipulator. A 134-N anterior force at 30° and 90° of flexion and combined valgus (8 N·m) and internal (4 N·m) rotation torques at 15° of flexion were applied simulating tests of anterior and rotatory stability. The ACL was sectioned at the femoral footprint by detaching either the higher band of fibers neighboring the lateral intercondylar ridge in the region of the direct insertion or the posterior, crescent-shaped fibers in the region of the indirect insertion, followed by the remainder of the ACL. The kinematics of the ACL-intact knee was replayed, and the reduction in force due to each sectioned portion of insertion fibers was measured. Isometry was assessed at anteromedial, center, and posterolateral locations within the high and low regions of the femoral footprint.

RESULTS

With an anterior tibial force at 30° of flexion, the high fibers carried 83.9% of the total anterior ACL load compared with 16.1% in the low fibers (P < .001). The high fibers also carried more anterior force than the low fibers at 90° of flexion (95.2% vs 4.8%; P < .001). Under combined torques at 15° of flexion, the high fibers carried 84.2% of the anterior ACL force compared with 15.8% in the low fibers (P < .001). Virtual ACL fibers placed at the anteromedial portion of the high region of the femoral footprint were the most isometric, with a maximum length change of 3.9 ± 1.5 mm.

CONCLUSION

ACL fibers located high within the femoral footprint bear more force during stability testing and are more isometric during flexion than low fibers.

CLINICAL RELEVANCE

It may be advantageous to create a "higher" femoral tunnel during ACL reconstruction at the lateral intercondylar ridge.

Femoral Aperture Fixation Improves Anterior Cruciate Ligament Graft Function When Added to Cortical Suspensory Fixation: An In Vivo Computer Navigation Study

Background:

Recommendations for bone tunnel placement during anterior cruciate ligament (ACL) reconstruction have become more precise. However, these recommendations differ neither with the choice of graft nor with the method of fixation used. The influence of the method of femoral fixation used on the biomechanical function of a soft tissue ACL graft remains unknown.

Hypothesis:

Our null hypothesis was that adding femoral aperture fixation to femoral cortical fixation, using the same bone tunnels, will not alter the control of anterior translation (AT) and internal rotation (IR) during ACL reconstruction using a hamstring graft.

Study Design:

Controlled laboratory study.

Methods:

A total of 22 patients with an acute isolated ACL rupture underwent reconstruction using a single-bundle autologous hamstring graft. Computer navigation was used intraoperatively to plot the AT and IR during the pivot-shift test before reconstruction, after ACL reconstruction using cortical suspensory fixation, and after the addition of femoral aperture fixation. Statistical analysis (analysis of variance) was used to compare the AT and IR during the pivot shift at each stage in the procedure.

Results:

Before ACL reconstruction, the mean (±SD) AT was 14.2 ± 7.3 mm and mean IR was 17.2° ± 5.5°. After reconstruction using femoral cortical suspension, these figures were significantly reduced to 6.2 ± 3.5 mm and 12.5° ± 3.20°, respectively (P < .001). The addition of the aperture fixation was associated with a further significant reduction to 4.6 ± 3.2 mm and 10.4° ± 2.7°, respectively (P < .001).

Conclusion:

The addition of femoral aperture fixation to suspensory fixation results in a significant reduction in both the AT and IR that occurs during the pivot-shift assessment immediately after ACL reconstruction using autologous hamstring graft.

Clinical Relevance:

The most precise positioning of bone tunnels during soft tissue ACL reconstruction needs to take into consideration the type of fixation being used.

Behind-remnant arthroscopic observation and scoring of femoral attachment of injured anterior cruciate ligament

PURPOSE

To describe the femoral anterior cruciate ligament (ACL) attachment based on the behind-remnant observation with a new scoring system and to investigate the characteristics of an ACL injured knee.

METHODS

One hundred and twenty-six ACL injured knees with four standardized arthroscopic photos and full evaluation under anaesthesia were included in the study. Sixty non-ACL injured knees were also evaluated as control. A scoring system for the femoral ACL attachment was set as follows based on behind-remnant findings; the direct insertion was divided into three portions as proximal, middle and distal. The fibrous extension from the articular surface (indirect insertion) and the severity of synovitis were also graded into 2, 1 and 0 points. The total score was 10 as full marks. The correlation between each score and total score, as well as age at surgery, gender, anterior laxity, pivot-shift test and meniscus injuries, was statistically evaluated with a significance of 0.05.

RESULTS

The femoral attachment score of the ACL injured knees was statistically different from that of the non-ACL injured knees. Anterior laxity was dependent only on the integrity of the proximal portion. Knee instability was significantly correlated with the status of the direct insertion. Medial and lateral meniscus injuries were correlated with the middle part and the distal part of the direct insertion, respectively. The direct insertion was less preserved in distal and articular sides.

CONCLUSION

Arthroscopic observation behind the remnant of the injured ACL showed clearer findings of the femoral attachment than that from the front. Behind-remnant observation greatly assists in the creation of a correct anatomical tunnel with the preserving remnant. The scoring system indicated several significant correlations between the score and preoperative patient status.

The anatomy of the anterior cruciate ligament and its relevance to the technique of reconstruction

Anterior cruciate ligament (ACL) reconstruction is commonly performed and has been for many years. Despite this, the technical details related to ACL anatomy, such as tunnel placement, are still a topic for debate. In this paper, we introduce the flat ribbon concept of the anatomy of the ACL, and its relevance to clinical practice.

Cite this article: Bone Joint J 2016;98-B:1020–6.

The ACL Graft Has Different Cross-sectional Dimensions Compared With the Native ACL: Implications for Graft Impingement

BACKGROUND

Impingement of anterior cruciate ligament (ACL) grafts against the femoral notch and the posterior cruciate ligament (PCL) is thought to be influenced primarily by tunnel position and graft orientation. Recent data have implied that the native ACL is ribbon-shaped.

PURPOSE

To evaluate the 3-dimensional shape and cross-sectional area of the native ACL versus the ACL graft and to compare the degree of impingement against the femoral notch and PCL.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Bilateral knee magnetic resonance images were analyzed for 27 patients with unilateral bone-patellar tendon-bone (BPTB) ACL reconstruction performed via transtibial or anteromedial portal femoral tunneling techniques. Three-dimensional models of the ACL, PCL, femur, and tibia were digitally rendered. The cross-sectional area and dimensions of the native ACL and the reconstructed graft were determined at 3 equally spaced locations and compared via Wilcoxon-Mann-Whitney and Kruskal-Wallis tests. In addition, impingement of the ACL on the PCL and femoral notch was graded in 3 groups. Chi-square or Fisher exact tests were used to compare the proportional differences of impingement of the native and reconstructed ACL on the PCL and femoral notch, respectively. All analyses were performed using 2-sided hypothesis testing, with statistical significance at P < .05.

RESULTS

Cross-sectional areas at all 3 points on the ACL graft were significantly greater than those of the native ACL (P < .001). The long- to short-axis ratio for the native ACL was significantly greater at each location compared with the corresponding locations along the ACL graft (P < .001), implying that the native ACL is "flatter" than is an ACL graft. There were 19 operated knees (70%) with contact or impingement between the ACL graft and the femoral notch compared with zero knees with a native ACL (P < .001). In addition, 22 operated knees (81%) showed contact or impingement between the ACL graft and the PCL, compared with 7 knees (26%) with a native ACL (P < .001). No significant differences in impingement frequency were noted between the transtibial and anteromedial tunneling techniques for ACL graft specimens (P > .05).

CONCLUSION

Native ACLs have a smaller cross-sectional area, are "flatter," and experience less incidence of impingement compared with anatomically placed BPTB ACL grafts.

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.

Posterior Wall Blowout in Anterior Cruciate Ligament Reconstruction: A Review of Anatomic and Surgical Considerations

Violation of the posterior femoral cortex, commonly referred to as posterior wall blowout, can be a devastating intraoperative complication in anterior cruciate ligament (ACL) reconstruction and lead to loss of graft fixation or early graft failure. If cortical blowout occurs despite careful planning and adherence to proper surgical technique, a thorough knowledge of the anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes. This article highlights anatomic considerations for femoral tunnel placement in ACL reconstruction and techniques for avoidance and salvage of a posterior wall blowout.

Anatomic Oblong Double Bundle Anterior Cruciate Ligament Reconstruction

Double-bundle anterior cruciate ligament (ACL) reconstruction using hamstring tendon grafts is a standard procedure for ACL injury. However, its clinical effectiveness is not always satisfactory. One cause of this was problems with the graft-tunnel healing of the posterolateral bundle (PLB) on the femur. To solve this problem, we devised a new anatomic ACL reconstruction technique to improve the graft-tunnel healing of the femoral PLB by using a single-bundle with one bone tunnel on the femoral side and a double-bundle on the tibial side. We have performed 40 procedures with excellent results and no cases of intra- or postoperative complication. This procedure can help improve the graft-tunnel healing around the femoral bone tunnel aperture for the PLB.

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.

A new behind-remnant approach for remnant-preserving double-bundle anterior cruciate ligament reconstruction compared with a standard approach

PURPOSE

To introduce a new behind-remnant approach for double-bundle (DB) anterior cruciate ligament (ACL) reconstruction and to compare the femoral tunnel positions of anteromedial (AM) and posterolateral (PL) bundles between the new and standard procedures by a three-dimensional computed tomography (3D-CT).

METHODS

During DB ACL reconstruction, two approaches for femoral tunnel creation were consecutively practiced from 2010 to 2012. The patients were evaluated retrospectively as a cohort study. A total of 200 primary ACL reconstructions have been performed using a transtibial approach. One approach was a standard approach from the front in which the ACL remnant was peeled off from the attachment, and two guide wires were inserted based on anatomic bony landmarks (standard group). The other approach was a new behind-remnant approach in which the ACL remnant was kept untouched and two guide wires were inserted at the posterior margin of the direct ACL insertion (behind-remnant group). The position of the AM and PL femoral tunnels was expressed on a 3D-CT reconstructive image using the quadrant method with a statistical analysis.

RESULTS

The depth of the AM center was 24 ± 6 % (mean and standard deviation) in the standard group and 22 ± 5 % in the behind-remnant group. The height of the AM tunnel center was 22 ± 8 % in the standard group and 31 ± 8 % in the behind-remnant group. The depth of the PL tunnel center was 32 ± 6 % in the standard group and 35 ± 5 % in the behind-remnant group. The height of the PL tunnel center was 47 ± 9 % in the standard group and 55 ± 7 % in the behind-remnant group. The AM and PL femoral tunnels in both groups were created within the normal anatomic footprint of the previous studies. The behind-remnant approach created a significantly lower femoral tunnel for both AM (p = 0.000) and PL tunnels (p = 0.000). The depth of both AM and PL tunnels was not significantly different between the two groups (n.s.).

CONCLUSION

The new behind-remnant procedure is technically simple and reproducible as a remnant-preserving ACL reconstruction.

LEVEL OF EVIDENCE

Cohort study, Level III.