A Prospective Evaluation of Femoral Tunnel Placement for Anatomic Anterior Cruciate Ligament Reconstruction Using 3-Dimensional Magnetic Resonance Imaging

Evaluating femoral graft placement using three-dimensional magnetic resonance imaging in the reconstruction of the anterior cruciate ligament via independent or transtibial drilling techniques: a retrospective cohort study

PURPOSE

Anterior cruciate ligament (ACL) reconstruction is a common surgical procedure, yet failure still largely occurs due to nonanatomically positioned grafts. The purpose of this study was to retrospectively evaluate patients with torn ACLs before and after reconstruction via 3D MRI and thereby assess the accuracy of graft position on the femoral condyle.

METHODS

Forty-one patients with unilateral ACL tears were recruited. Each patient underwent 3D MRI of both knees before and after surgery. The location of the reconstructed femoral footprint relative to the patient's native footprint was compared.

RESULTS

Native ACL anatomical location of the native ACL had a significant impact on graft position. Native ACLs that were previously more anterior yielded grafts that were more posterior (3.70 ± 1.22 mm, P = 0.00018), and native ACL that were previously more proximal yielded grafts that were more distal (3.25 ± 1.09 mm, P = 0.0042). Surgeons using an independent drilling method positioned 76.2% posteriorly relative to the native location, with a mean 0.1 ± 2.8 mm proximal (P = 0.8362) and 1.8 ± 3.0 mm posterior (P = 0.0165). Surgeons using a transtibial method positioned 75% proximal relative to the native location, with a mean 2.2 ± 3.0 mm proximal (P = 0.0042) and 0.2 ± 2.6 mm posterior (P = 0.8007). These two techniques showed a significant difference in magnitude in the distal-proximal axis (P = 0.0332).

CONCLUSION

The femoral footprint position differed between the native and reconstructed ACLs, suggesting that ACL reconstructions are not accurate. Rather, they are converging to a normative reference point that is neither anatomical nor isometric.

Race and Gender Differences in Anterior Cruciate Ligament Femoral Footprint Location and Orientation: A 3D-MRI Study

OBJECTIVE

The femoral tunnel position is crucial to anatomic single-bundle anterior cruciate ligament (ACL) reconstruction, but the ideal femoral footprint position are mostly based on small-sized cadaveric studies and elderly patients with a single ethnic background. This study aimed to identify potential race- or gender-specific differences in the ACL femoral footprint location and ACL orientation, determine the correlation between the ACL orientation and the femoral footprint location.

METHODS

Magnetic resonance images (MRIs) of 90 Caucasian participants and 90 matched Chinese subjects were used for reconstruction of three-dimensional (3D) femur and tibial models. ACL footprints were sketched by several experienced orthopedic surgeons on the MRI photographs. The anatomical coordinate system was applied to reflect the ACL footprint location and orientation of scanned samples. The femoral ACL footprint locations were represented by their distance from the origin in the anteroposterior (A/P) and distal-proximal (D/P) directions. The orientation of the ACL was described with the sagittal, coronal and transverse deviation angles. The ACL orientation and femoral footprint position were compared by the two-sided t-test. Multiple regression analysis was used to study the correlation between the orientation and femoral footprint position.

RESULTS

The average femur footprint A/P position was -6.6 ± 1.6 mm in the Chinese group and -5.1 ± 2.3 mm in the Caucasian group, (p < 0.001). The average femur footprint D/P position was -2.8 ± 2.4 mm in Chinese and - 3.9 ± 2.0 mm in Caucasians, (p = 0.001). The Chinese group had a mean difference of a 1.5 mm (6.1%) more posterior and 1.1 mm (5.3%) more proximal in the position from the flexion-extension axis (FEA). And the males have a sagittal plane elevation about 4-5° higher than females in both racial groups. Furthermore, for every 1% (0.40 mm) increase in A/P and D/P values, the sagittal angle decreased by about 0.12° and 0.24°, respectively; the coronal angle decreased by about 0.10° and 0.30°, respectively. For every 1% (0.40 mm) increase in D/P value, the transverse angle increased by about 0.14°.

CONCLUSION

The significant race- and gender-specific differences in the femoral footprint and orientation of the ACL should be taken in consideration during anatomic single-bundle ACL reconstruction. Furthermore, the quantitative relationship between the ACL orientation and the footprint location might provide some reference for surgeons to develop a surgical strategy in ACL single-bundle reconstruction and revision.

Anterior cruciate ligament femoral footprint is oblong-ovate, triangular, or two-tears shaped in healthy young adults: three-dimensional MRI analysis

PURPOSE

This study aimed to evaluate the morphology of the anterior cruciate ligament (ACL) femoral footprint with three-dimensional magnetic resonance imaging (3D MRI) in healthy knees.

METHODS

Fifty subjects with healthy knees were recruited, utilising 3D-SPACE sequences for ACL evaluation. The ACL was manually segmented, and the shape, size and location of the ACL femoral footprint were evaluated on a reformatted oblique-sagittal plane, which aligned closely with the ACL attachment. Statistical analysis included one-way ANOVA for continuous variables and Fisher's exact test for categorical variables, with a P value < 0.05 considered significant.

RESULTS

Three types of ACL femoral footprint shape were identified, namely, oblong-ovate (OO) in 33 knees (66%), triangular (Tr) in 12 knees (24%) and two-tears (TT) in 5 knees (10%), with the mean areas being 58, 47 and 68 mm2, respectively. Within group TT, regions with similar sizes but different locations were identified: high tear (TT-H) and low tear (TT-L). Notably, group OO demonstrated a larger notch height index, whilst group TT was characterised by a larger α angle and lateral femoral condyle index. A noticeable variation was observed in the location of the femoral footprint centre across groups, with group TT-L and group Tr showing a more distal position relative to the apex of the deep cartilage. According to the Bernard and Hertel (BH) grid, the ACL femoral footprint centres in group TT-L exhibited a shallower and higher position than other groups. Furthermore, compared to group OO and TT-H, group Tr showed a significantly higher position according to the BH grid.

CONCLUSION

In this study, the morphology of the ACL femoral footprint in healthy young adults was accurately evaluated using 3D MRI, revealing three distinct shapes: OO, Tr and TT. The different ACL femoral footprint types showed similar areas but markedly different locations. These findings emphasise the necessity of considering both the shape and precise location of the ACL femoral footprint during clinical assessments, which might help surgeons enhance patient-specific surgical plans before ACL reconstruction.

LEVEL OF EVIDENCE

IV.

Tunnel Management in Revision Anterior Cruciate Ligament Reconstruction: Current Concepts

Bone tunnel-related complications are frequently encountered during revision anterior cruciate ligament reconstruction (ACLR). Issues with tunnel positioning, enlargement, containment, and hardware interference may complicate surgery and compromise outcomes. As a result, several strategies have emerged to address these issues and optimize results. However, a systematic, unified approach to tunnel pathology in revision ACLR is lacking. The purpose of this review is to highlight the current state of the literature on bone tunnel complications and, although extensive literature on the subject is lacking, present an updated approach to the evaluation and management of tunnel-related issues in revision ACLR.

Rebranding the 'anatomic' ACL reconstruction: Current concepts

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

Biomechanical Analysis of Ideal Knee Flexion Angle for ACL Graft Tensioning Utilizing Multiple Femoral and Tibial Tunnel Locations

Anterior cruciate ligament (ACL) graft failure rate has been reported to be greater than 5% at 5 years. Our study evaluated ACL excursion with anatomic and nonanatomic femoral and tibial tunnels to determine optimal flexion angle to tension the ACL to minimize excursion. Ten cadaveric knee specimens were used. The ACL was sectioned and the femoral and tibial attachments were marked. A 1/16-inch drill created a tunnel in the center of the ACL footprint on the tibia and femur and additional tunnels were made 5 mm from this. A suture was passed through each tunnel combination and attached to a string potentiometer. The knee was ranged from full extension to 120 degrees of flexion for 10 cycles while mounted in a custom fixture. The change in length (excursion) of the suture during movement was recorded for each combination of femoral and tibial tunnels. Anatomic reconstruction of the ACL with tunnel placement in the center of the femoral and tibial footprint did not result in an isometric graft, with excursion of the ACL during knee motion of 7.46 mm (standard deviation [SD]: 2.7mm), greatest at 2.84 degrees of flexion (SD: 4.22). The tunnel combination that resulted in the least excursion was a femoral footprint 5 mm anterior to the femoral and 5 mm posterior to the tibial footprint (4. 2mm, SD: 1.37 mm). The tunnel combination that resulted in the most excursion utilized femoral footprint 5 mm proximal to the femoral and 5 mm posterior to the tibial footprint (9.81 mm, SD: 2.68 mm). Anatomic ACL reconstruction results in significant excursion of the ACL throughout motion. If not tensioned properly, the ACL can stretch during range of motion, potentially leading to rerupture. To prevent stretching of the graft, the current biomechanical study recommends tensioning an anatomic ACL reconstruction at its point of maximal excursion, or between 0 and 5 degrees of flexion. The level of evidence is IV.

The apex of the deep cartilage is a stable landmark to evaluate the femoral tunnel position in ACL reconstruction

PURPOSE

To develop a simple and effective method for evaluating the femoral tunnel position using the apex of the deep cartilage (ADC) as the landmark.

METHODS

A total of 52 patients who underwent arthroscopic ACL reconstruction were recruited between June and September 2021. The femoral tunnel was placed on the central point of the anteromedial footprint with an accessory anteromedial and a high anterolateral portal. Then, the length from the ADC to the shallow cartilage margin (L₁) and to the center of the femoral tunnel (l₁), as well as the center to the low cartilage margin (H₁, intraoperative height), was measured under arthroscopy and on postoperative CT scans (L₂, l₂ and H₂). Moreover, intraoperative and postoperative cartilage ratios were equivalent to l₁/L₁ and l₂/L₂, respectively. Linear regression, Pearson correlation and Bland-Altman analysis were performed to evaluate the consistency between these two measurements of cartilage ratio (l/L) and height (H).

RESULTS

The mean age at the time of surgery was 28.7 years; 42 patients were male, and 17 patients were hurt in the left knee among 52 patients. The intraoperative cartilage ratio was 0.37 ± 0.04, and the height was 8.1 ± 1.1 mm with almost perfect inter-observer reproducibility. After the surgery, the cartilage ratio and height were measured as 0.39 ± 0.04 and 8.2 ± 1.3 mm on 3D-CT, respectively, with almost perfect intra- and inter-observer reproducibility. Significant positive correlations and linear regression were detected in the cartilage ratio (r = 0.844, p < 0.001), and height (r = 0.926, p < 0.001) intraoperatively and postoperatively. The Bland-Altman plot also showed excellent consistency between arthroscopy and 3D-CT.

CONCLUSIONS

The ADC is a good landmark in the assessment of femoral tunnel position, with excellent consistency between intraoperative arthroscopic measurements and postoperative 3D-CT.

CLINICALTRIALS

gov Identifier: NCT04937517.

LEVEL OF EVIDENCE

Level III.

Influence of the Anteromedial Portal and Transtibial Drilling Technique on Femoral Tunnel Lengths in ACL Reconstruction: Results Using an MRI-Based Model

Background:

In anatomic anterior cruciate ligament (ACL) reconstruction, graft placement through the anteromedial (AM) portal technique requires more horizontal drilling of the femoral tunnel as compared with the transtibial (TT) technique, which may lead to a shorter femoral tunnel and affect graft-to-bone healing. The effect of coronal and sagittal femoral tunnel obliquity angle on femoral tunnel length has not been investigated.

Purpose:

To compare the length of the femoral tunnels created with the TT technique versus the AM portal technique at different coronal and sagittal obliquity angles using the native femoral ACL center as the starting point of the femoral tunnel. The authors also assessed sex-based differences in tunnel lengths.

Study Design:

Descriptive laboratory study.

Methods:

Magnetic resonance imaging scans of 95 knees with an ACL rupture (55 men, 40 women; mean age, 26 years [range, 16-45 years]) were used to create 3-dimensional models of the femur. The femoral tunnel was simulated on each model using the TT and AM portal techniques; for the latter, several coronal and sagittal obliquity angles were simulated (coronal, 30°, 45°, and 60°; sagittal, 45° and 60°), representing the 10:00, 10:30, and 11:00 clockface positions for the right knee. The length of the femoral tunnel was compared between the techniques and between male and female patients.

Results:

The mean ± SD femoral tunnel length with the TT technique was 40.0 ± 6.8 mm. A significantly shorter tunnel was created with the AM portal technique at 30° coronal/45° sagittal (35.5 ± 3.8 mm), whereas a longer tunnel was created at 60° coronal/60° sagittal (53.3 ± 5.3 mm; P < .05 for both). The femoral tunnel created with the AM portal technique at 45° coronal/45° sagittal (40.7 ± 4.8 mm) created a similar tunnel length as the TT technique. For all techniques, the femoral tunnel was significantly shorter in female patients than male patients.

Conclusion:

The coronal and sagittal obliquity angles of the femoral tunnel in ACL reconstruction can significantly affect its length. The femoral tunnel created with the AM portal technique at 45° coronal/45° sagittal was similar to that created with the TT technique.

Clinical Relevance:

Surgeons should be aware of the femoral tunnel shortening with lower coronal obliquity angles, especially in female patients.

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.

Compressed Lateral and anteroposterior Anatomical Systematic Sequences «CLASS»: compressed MRI sequences with assessed anatomical femoral and tibial ACL's footprints, a feasibility study

Purpose

This study's main objective is to assess the feasibility of processing the MRI information with identified ACL-footprints into 2D-images similar to a conventional anteroposterior and lateral X-Ray image of the knee. The secondary aim is to conduct specific measurements to assess the reliability and reproducibility. This study is a proof of concept of this technique.

Methods

Five anonymised MRIs of a right knee were analysed. A orthopaedic knee surgeon performed the footprints identification. An ad-hoc software allowed a volumetric 3D image projection on a 2D anteroposterior and lateral view. The previously defined anatomical femoral and tibial footprints were precisely identified on these views. Several parameters were measured (e.g. coronal and sagittal ratio of tibial footprint, sagittal ratio of femoral footprint, femoral intercondylar notch roof angle, proximal tibial slope and others). The intraclass correlation coefficient (ICCs), including 95% confidence intervals (CIs), has been calculated to assess intraobserver reproducibility and interobserver reliability.

Results

Five MRI scans of a right knee have been assessed (three females, two males, mean age of 30.8 years old). Five 2D-"CLASS" have been created. The measured parameters showed a "substantial" to "almost perfect" reproducibility and an "almost perfect" reliability.

Conclusion

This study confirmed the possibility of generating "CLASS" with the localised centroid of the femoral and tibial ACL footprints from a 3D volumetric model. "CLASS" also showed that these footprints were easily identified on standard anteroposterior and lateral X-Ray views of the same patient, thus allowing an individual identification of the anatomical femoral and tibial ACL's footprints.

Level of evidence

Level IV diagnostic study

Feasibility and accuracy of orthopaedic surgical robot system for intraoperative navigation to locate bone tunnel in anterior cruciate ligament reconstruction

BACKGROUND

The combination of navigational system and robotics has the potential to accurately identify and drill bone tunnels in anterior cruciate ligament (ACL) reconstruction. This study explores the feasibility and accuracy of bone tunnel positioning using the TiRobot, an orthopaedic surgical robot.

METHODS

The experiment was divided into two groups. In group A, the bone tunnels were positioned using the TiRobot surgical robot (n = 8). In group B, handheld locators were used for positioning (n = 8).

RESULTS

TiRobot can be used for positioning the ACL bone tunnel. The accuracy of positioning the femoral tunnel in group A and B was 1.00 ± 0.20 and 3.10 ± 0.59 mm, respectively (t = -9.49, P < 0.001). As for tibial tunnel, the accuracy was 1.02 ± 0.20 and 2.64 ± 0.14 mm, respectively (t = -18.54, P < 0.001).

CONCLUSIONS

The bone tunnel drilling precision using TiRobot for ACL reconstruction surgery was more accurate than traditional surgical techniques.

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

Background:

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

Purpose:

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

Study Design:

Cohort study; Level of evidence, 3.

Methods:

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

Results:

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

Conclusion:

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

The risk of graft impingement still exists in modern ACL surgery and correlates with degenerative MRI signal changes

PURPOSE

Anatomic tunnel placement in ACL reconstruction is crucial to restore knee function. The aims of this study were to (i) evaluate the accuracy of tunnel placement for primary state-of-the-art ACL reconstruction, and (ii) examine the correlation between incorrect tunnel placement, graft appearance, and notch impingement.

METHODS

In this retrospective study, all patients underwent primary single-bundle ACL reconstruction with independent drilling of the femoral and tibial tunnels according to anatomical landmarks. The accuracy of tunnel placement and the rate of notch impingement were analysed with MRI. The study cohort was subdivided according to the morphology of the graft: intact, degeneration, and re-rupture. The objective outcome was evaluated with the IKDC objective score, and the subjective outcomes were evaluated with the IKDC subjective score, the Lysholm knee score, the KOOS, and the Tegner activity scale score.

RESULTS

Eighty-seven consecutive patients with a mean follow-up of 3.8 ± 1.4 years were evaluated. There was no significant difference among the groups concerning the baseline characteristics. The re-rupture rate was 9.2%. The position of the femoral tunnel was correct in 92% of the patients, and the position of the tibial tunnel was correct in 93% of the patients. In the intact group, impingement was not found in any of the cases, whereas the rate of impingement in the degeneration (65%) and re-rupture (80%) groups was significantly higher than that in the intact group (p < 0.001). The risk of impingement was more likely with femoral (71% vs. 13%, p < 0.001) or tibial (100% vs. 11%, p < 0.001) malpositioning. The objective IKDC score was A in 52 patients (60%), B in 26 patients (30%), and C in 9 patients (10%). The average subjective IKDC score, Lysholm score, and KOOS were comparable in the intact and degeneration groups but significantly lower in the patient group with newly diagnosed re-ruptures (p = 0.05). The Tegner activity scale score was comparable in all three groups.

CONCLUSION

Even though the accuracy of femoral tunnel placement in modern single-bundle ACL reconstruction is greater, the risk of malpositioning and graft impingement remains. In our patient cohort, there was a clear correlation between ACL graft impingement, degenerative changes in MRI, and incorrect tunnel positioning. The surgeon must focus on accurate tunnel placement specific to individual patient anatomy.

LEVEL OF EVIDENCE

Level III.

Artificial Intelligence in the Management of Anterior Cruciate Ligament Injuries

Background:

Technological innovation is a key component of orthopaedic surgery. With the integration of powerful technologies in surgery and clinical practice, artificial intelligence (AI) may become an important tool for orthopaedic surgeons in the future. Through adaptive learning and problem solving that serve to constantly increase accuracy, machine learning algorithms show great promise in orthopaedics.

Purpose:

To investigate the current and potential uses of AI in the management of anterior cruciate ligament (ACL) injury.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

A systematic review of the PubMed, MEDLINE, Embase, Web of Science, and SPORTDiscus databases between their start and August 12, 2020, was performed by 2 independent reviewers. Inclusion criteria included application of AI anywhere along the spectrum of predicting, diagnosing, and managing ACL injuries. Exclusion criteria included non-English publications, conference abstracts, review articles, and meta-analyses. Statistical analysis could not be performed because of data heterogeneity; therefore, a descriptive analysis was undertaken.

Results:

A total of 19 publications were included after screening. Applications were divided based on the different stages of the clinical course in ACL injury: prediction (n = 2), diagnosis (n = 12), intraoperative application (n = 1), and postoperative care and rehabilitation (n = 4). AI-based technologies were used in a wide variety of applications, including image interpretation, automated chart review, assistance in the physical examination via optical tracking using infrared cameras or electromagnetic sensors, generation of predictive models, and optimization of postoperative care and rehabilitation.

Conclusion:

There is an increasing interest in AI among orthopaedic surgeons, as reflected by the applications for ACL injury presented in this review. Although some studies showed similar or better outcomes using AI compared with traditional techniques, many challenges need to be addressed before this technology is ready for widespread use.

Clinical Outcome Evaluation of Anatomic Anterior Cruciate Ligament Reconstruction With Tunnel Positioning Using Gold Standard Techniques: A Systematic Review and Meta-analysis

Background:

There have been conflicting results about the theoretical advantages of anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

Purpose:

To evaluate the clinical and functional outcomes comparing anatomic single- versus double-bundle techniques, anatomic versus nonanatomic techniques, and transportal versus outside-in tunnel drilling for ACL reconstruction.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

A search was performed in the MEDLINE and EMBASE databases up to August 2018 for clinical trials comparing anatomic ACL reconstruction (with tunnel positioning demonstrated using gold standard radiologic techniques) with another technique, with a minimum functional and biomechanical follow-up of 6 months. A meta-analysis was performed to compare clinical and functional outcomes between anatomic single- versus double-bundle reconstruction and between anatomic versus nonanatomic techniques, using the risk difference or the mean difference. Risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale for cohort and case-control studies and the Cochrane Risk of Bias tool and Jadad Score for randomized controlled trials.

Results:

Included were 15 studies comprising 1290 patients (follow-up, 12-36 months). No significant differences favoring anatomic double-bundle over anatomic single-bundle reconstruction or outside-in over transportal techniques were found. The meta-analyses showed significant differences in the International Knee Documentation Committee (IKDC) objective score (risk difference, –0.14; 95% confidence interval, –0.27 to –0.01) favoring anatomic over nonanatomic reconstruction. No statistically significant differences were found between anatomic and nonanatomic surgical techniques on other functional scores or clinical examination outcomes, including the IKDC subjective score, Lysholm score, Tegner score, KT-1000 arthrometer test, or pivot-shift test.

Conclusion:

Double-bundle reconstruction was not superior to the single-bundle technique in clinical and functional outcomes. Anatomic ACL reconstruction shows significantly superior results over nonanatomic ACL reconstruction, reinforcing the anatomic technique as the gold standard choice for clinical practice.

High variability in anterior cruciate ligament femoral footprint: Implications for anatomical anterior cruciate ligament reconstruction

BACKGROUND

The study aimed to (1) investigate the variability of the femoral ACL center in ACL-ruptured patients, (2) identify whether the currently available over-the-top femoral ACL guides could allow for anatomical reconstruction of the native ACL footprint.

MATERIAL AND METHODS

Magnetic resonance images of 95 knees with an ACL rupture were used to create three-dimensional models of the femur. The femoral ACL footprint area was outlined on each model, and the location of the femoral ACL center was reported using an anatomical coordinate system. The distance of the femoral ACL center from the over-the-top position was measured.

RESULTS

The femoral ACL center demonstrated a high intersubject variability ranging from 1.8 mm (9%) to 12.3 mm (60%) posterior and from 7.7 mm (37%) distal to 4.8 mm (23%) proximal using the posterior condyle circle reference. The average distance of the femoral ACL center from the over-the-top position was 1.9 ± 1.5 mm posterior and 13.8 ± 2.7 mm distal, respectively. The contemporary over-the-top femoral ACL aimers could restore the femoral ACL center in only 6.5% of the patients.

CONCLUSIONS

The femoral ACL center demonstrated a high variation on its location, which resulted in a high intersubject variability from the over-the-top position. The contemporary over-the-top femoral tunnel guides do not provide sufficient offset to allow for an anatomical ACL reconstruction. Anteromedial-portal specific femoral ACL guides with a femoral offset ranging from 10 to 18 mm in the proximal/distal direction are required to restore the native ACL footprint.

Femoral Intercondylar Notch: Gross Anatomy and Histology of the Connective Tissue Lining of its Roof: A Pilot Study

PURPOSE

We have consistently observed a connective tissue lining over the intercondylar notch's roof (CTLINR) during arthroscopic surgeries of the knee joint. As there is a strong association of the intercondylar fossa with the anterior cruciate ligament (ACL), we believe that this tissue must be having some role in the functioning of the ACL. The purpose of this pilot study was to investigate the anatomic characteristics of the CTLINR.

METHODS

In this observational anatomical study, we have investigated the gross anatomical and histological features of the CTLINR in four knees of two fresh frozen non-embalmed cadavers. We have also studied its ultrastructural characteristics by obtaining an arthroscopic biopsy of the tissue from a patient undergoing ACL reconstruction.

RESULTS

At gross examination, the CTLINR had a typical glistening white surface with transversely oriented fibres. It entirely covered the roof of the intercondylar notch and was soft to touch. Histological examination with haematoxylin-eosin stain revealed fibro-collagenous tissue with intervening blood vessels. Transmission electron microscopy manifested loosely arranged collagen fibres of variable diameter.

CONCLUSION

The histological and electron microscopic characteristics of the tissue differentiate it from the ACL and its femoral enthesis, suggesting that it was a distinct anatomical structure. As it entirely covered the roof of the intercondylar fossa and had a smooth surface and soft consistency, it may protect the reconstructed ACL from graft abrasion. Furthermore, as it had a characteristic arthroscopic appearance, future research can investigate its role in femoral tunnel positioning.

The REVision Using Imaging to Guide Staging and Evaluation (REVISE) in ACL Reconstruction Classification

Revision anterior cruciate ligament (ACL) procedures are increasing in incidence and possess markedly inferior clinical outcomes (76% satisfaction) and return-to-sports (57%) rates than their primary counterparts. Given their complexity, a universal language is required to identify and communicate the technical challenges faced with revision procedures and guide treatment strategies. The proposed REV: ision using I: maging to guide S: taging and E: valuation (REVISE) ACL (anterior cruciate ligament) Classification can serve as a foundation for this universal language that is feasible and practical with acceptable inter-rater agreement. A focus group of sports medicine fellowship-trained orthopaedic surgeons was assembled to develop a classification to assess femoral/tibial tunnel "usability" (placement, widening, overlap) and guide the revision reconstruction strategy (one-stage vs. two-stage) post-failed ACL reconstruction. Twelve board-certified sports medicine orthopaedic surgeons independently applied the classification to the de-identified computed tomographic (CT) scan data of 10 patients, randomly selected, who failed ACL reconstruction. An interclass correlation coefficient (ICC) was calculated (with 95% confidence intervals) to assess agreement among reviewers concerning the three major classifications of the proposed system. Across surgeons, and on an individual patient basis, there was high internal validity and observed agreement on treatment strategy (one-stage vs. two-stage revision). Reliability testing of the classification using CT scan data demonstrated an ICC (95% confidence interval) of 0.92 (0.80-0.98) suggesting "substantial" agreement between the surgeons across all patients for all elements of the classification. The proposed REVISE ACL Classification, which employs CT scan analysis to both identify technical issues and guide revision ACL treatment strategy (one- or two-stage), constitutes a feasible and practical system with high internal validity, high observed agreement, and substantial inter-rater agreement. Adoption of this classification, both clinically and in research, will help provide a universal language for orthopaedic surgeons to discuss these complex clinical presentations and help standardize an approach to diagnosis and treatment to improve patient outcomes. The Level of Evidence for this study is 3.

A Hybrid Transtibial Technique Combines the Advantages of Anteromedial Portal and Transtibial Approaches: A Prospective Randomized Controlled Trial

BACKGROUND

The anteromedial (AM) portal and transtibial (TT) approaches are 2 common anterior cruciate ligament (ACL) femoral tunnel drilling techniques, each with unique benefits and disadvantages. A hybrid TT (HTT) technique using medial portal guidance of a flexible TT guide wire has recently been described that may combine the strengths of both the AM portal and the TT approaches.

HYPOTHESIS

The HTT technique will achieve anatomic femoral tunnel apertures similar to the AM portal technique, with improved femoral tunnel length and orientation.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 30 consecutive patients with primary ACL tears were randomized to undergo the TT, AM portal, or HTT technique for femoral tunnel positioning at the time of reconstruction. All patients underwent 3-dimensional computed tomography of the operative knee at 6 weeks postoperatively. Femoral and tibial tunnel aperture positions and tunnel lengths, as well as graft bending angles in the sagittal and coronal planes, were measured.

RESULTS

Tibial tunnel lengths and aperture positions were identical between the 3 groups. The AM portal and HTT techniques achieved identical femoral aperture positions in regard to both height (P = .629) and depth (P = .582). By contrast, compared with the AM portal and HTT techniques, femoral apertures created with the TT technique were significantly higher (P < .001 and P < .001, respectively) and shallower (P = .014 and P = .022, respectively) in the notch. The mean femoral tunnel length varied significantly between the groups, measuring 35.2, 41.6, and 54.1 mm for the AM portal, HTT, and TT groups, respectively (P < .001). Last, there was no difference between the mean coronal (P = .190) and sagittal (P = .358) graft bending angles between the TT and HTT groups. By contrast, compared with the TT and HTT techniques, femoral tunnels created with the AM portal technique were significantly more angulated in the coronal plane (17.7° [P < .001] and 12.5° [P = .006], respectively) and sagittal plane (13.5° [P < .001] and 10.5° [P = .013], respectively).

CONCLUSION

This prospective randomized controlled trial found that the HTT technique achieved femoral aperture positions equally as anatomic as the AM portal technique but produced longer, less angulated femoral tunnels, which may help reduce graft strain and mismatch. As such, this hybrid approach may represent a beneficial combination of both the TT and the AM portal techniques.

REGISTRATION

NCT02795247 (ClinicalTrials.gov identifier).

Can Surgeons Identify ACL Femoral Ridges Landmark and Optimal Tunnel Position? A 3D Model Study

Purpose

To examine the ability of surgeons to identify the osseous landmarks associated with the femoral anterior cruciate ligament (ACL) footprint and locate optimal tunnel placement on 3-dimensional (3D) printed models compared with intraoperative placement.

Methods

Twelve sports fellowship-trained orthopaedic surgeons were asked to identify a femoral landmark and an ACL footprint on 10 different 3D printed knees. The 3D models were made based on 20 real patients with different anatomical morphology who later received ACL reconstructive surgery using independent drilling. ImageJ software was used to quantify the measurements, which were then analyzed using descriptive statistics.

Results

Overall, none of the surgeons were able to consistently identify the junction of the bony ridges. The mean error per participant ranged from 2.81 to 7.34 mm in the proximal direction (P = 3.30e-05) and from 2.42 to 8.05 mm in the posterior direction (P =4.88e-12). None of the surgeons were able to appropriately identify the center of the femoral footprint on the anatomic 3D models. The difference between the center of the footprint surgeons identified on the 3D model and the tunnel graft location in surgery was significantly different (P = .0046). On average, the magnitude of the error when the surgeons performed the actual surgery was 3.72 ± 2.43 mm, whereas on the 3D models it was 5.82 ± 1.97 mm.

Conclusions

Experienced sports fellowship-trained orthopaedic surgeons were unable to correctly identify the junction of the intercondylar and bifurcate ridges and the native ACL footprint on 3D models. Operatively placed tunnels were more accurate implying that looking either through a scope or soft-tissue landmarks play a significant role in surgeons ACL footprint localization.

Clinical Relevance

The graft position for ACL reconstruction plays an important role on the kinematics of the knee. This paper shows that soft tissue landmarks are needed to provide reliable reference points for reconstruction.

Effect of Nearly Isometric ACL Reconstruction on Graft-Tunnel Motion: A Quantitative Clinical Study

Background:

In anterior cruciate ligament (ACL) reconstruction, minimizing the graft-tunnel motion (GTM) will promote graft-to-bone healing and avoid graft loosening or tearing as well as potential bone tunnel enlargement. A nearly isometric state of the graft can be achieved by placing the tunnel properly to theoretically gain better graft-to-bone healing. However, little clinical evidence is available to quantify the relation between GTM and tunnel position.

Purpose:

To find the proper zones for the femoral and tibial tunnel apertures that minimize the GTM, referred to as the “nearly isometric zone,” through use of intraoperative GTM measurement and 3-dimensional computed tomography (3D-CT).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 100 patients were enrolled in this study. Nearly isometric ACL reconstruction was performed, and an intra-articular GTM measuring device was designed to measure and record the amplitude of GTM while the knee was flexed from 0° to 120°. Postoperatively, the patients underwent multislice CT, and the images were used to create 3D-CT models. After tibial aperture examination, 5 patients were excluded due to the divergence of tibial aperture, and therefore 95 patients remained in the study. Patients were divided into 2 groups according to whether the lateral intercondylar ridge was absent or present. The Bernard-Hertel grid coordinates (h, t) of the femoral tunnel were then quantified.

Results:

The maximal GTM (mGTM) was a mean ± SD of 1.06 ± 0.66 mm (range, 0.0-3.0 mm). The mGTM in patients with a lateral intercondylar ridge was significantly lower than that in patients without a lateral intercondylar ridge (0.81 ± 0.39 vs 1.59 ± 0.73 mm, respectively; P < .0001). The average h and t were 0.227 ± 0.079 and 0.429 ± 0.770, respectively. Notably, in 1 patient, the mGTM was 0 mm whereas the coordinates (h, t) of the femoral tunnel were 0.250 and 0.255. The overall GTM slowly increased before 90° but increased significantly after the knee was bent 105° (P = .010). Correlation analysis showed that the t coordiinate had significant correlation with mGTM (R = 0.581; P < .001). A gradient pattern was created to show the nearly isometric blue zone (mGTM <0.5 mm), which was found to overlap with the IDEAL (isometric, direct insertion, eccentric, anatomic, low tension-flexion pattern) position.

Conclusion:

A method of measuring intraoperative GTM and quantifying femoral tunnel position on postoperative 3D-CT was successfully developed. The presence of a lateral condylar ridge can significantly reduce mGTM. A nearly isometric zone was described that was consistent with the IDEAL concept.

Three-Dimensional Magnetic Resonance Imaging for Guiding Tibial and Femoral Tunnel Position in Anterior Cruciate Ligament Reconstruction: A Cadaveric Study

Background:

Femoral and tibial tunnel malposition for anterior cruciate ligament (ACL) reconstruction (ACLR) is correlated with higher failure rate. Regardless of the surgical technique used to create ACL tunnels, significant mismatches between the native and reconstructed footprints exist.

Purpose:

To compare the position of tunnels created by a standard technique with the ones created based on preoperative 3-dimensional magnetic resonance imaging (3D MRI) measurements of the ACL anatomic footprint.

Study Design:

Controlled laboratory study.

Methods:

Using 3D MRI, the native ACL footprints were identified. Tunnels were created on 16 knees (8 cadavers) arthroscopically. On one knee of a matched pair, the tunnels were created based on 3D MRI measurements that were provided to the surgeon (roadmapped technique), while on the contralateral knee, the tunnels were created based on a standard anatomic ACLR technique. The technique was randomly assigned per set of knees. Postoperatively, the positions of the tunnels were measured using 3D MRI.

Results:

On the tibial side, the median distance between the center of the native and reconstructed ACL footprints in relation to the root of the anterior horn of the lateral meniscus medially was 1.7 ± 2.2 mm and 1.9 ± 2.8 mm for the standard and roadmapped techniques, respectively (P = .442), while the median anteroposterior distance was 3.4 ± 2.4 mm and 2.5 ± 2.5 mm for the standard and roadmapped techniques, respectively (P = .161). On the femoral side, the median distance in relation to the apex of the deep cartilage (ADC) distally was 0.9 ± 2.8 mm and 1.3 ± 2.1 mm for the standard and roadmapped techniques, respectively (P = .195), while the median distance anteriorly from the ADC was 1.2 ± 1.3 mm and 4.6 ± 4.5 mm for the standard and roadmapped techniques, respectively (P = .007).

Conclusion:

Providing precise radiological measurements of the ACL footprints does not improve the surgeon’s ability to position the tunnels. Future studies should continue to attempt to provide tools to improve the tunnel position in ACLR.

Clinical Relevance:

This cadaveric study indicates that despite the use of 3D MRI in understanding the ACL anatomy, re-creating the native ACL footprints remains a challenge.

A comparison of femoral tunnel placement in ACL reconstruction using a 70° arthroscope through the anterolateral portal versus a 30° arthroscope through the anteromedial portal: a pilot 3D-CT study

Background

Graft malposition is a risk factor for failure of anterior cruciate ligament reconstruction. A 70° arthroscope improves visualisation of the medial wall of the lateral femoral condyle without switching portals. We investigated whether the use of this arthroscope affected the accuracy and precision of femoral tunnel placement.

Methods

Fifty consecutive adult patients were recruited. Following one withdrawal and two exclusions, 47 patients (30 in group 1 (70° arthroscope), 17 in group 2 (30° arthroscope)) underwent three-dimensional computed tomography imaging using a grid-based system to measure tunnel position.

Results

No difference was found in the accuracy or precision of tunnels (mean position: group 1 = 33.3 ± 6.0% deep–shallow, 27.2 ± 5.2% high–low; group 2 = 31.7 ± 6.9% deep–shallow, 29.0 ± 6.2% high–low; not significant). A post-hoc power analysis suggests a study of 106 patients would be required.

Conclusions

This pilot study suggests that tunnel position is not affected by the arthroscope used. An appropriately powered study could investigate this finding alongside other potential benefits of using a 70° arthroscope for this procedure.

Trial registration

ClinicalTrials.gov, NCT02816606. Registered on 28 June 2016.

Effect of Teaching Session on Resident Ability to Identify Anatomic Landmarks and Anterior Cruciate Ligament Footprint: A Study Using 3-Dimensional Modeling

Background:

Femoral tunnel positioning in anterior cruciate ligament reconstruction (ACLR) is an intricate procedure that requires highly specific surgical skills.

Purpose:

To report the ability of residents to identify femoral landmarks and the native ACL footprint before and after a structured formal teaching session as a reflection of overall surgical skill training for orthopaedic surgery residents in Canada.

Study Design:

Controlled laboratory study.

Methods:

A total of 13 senior orthopaedic residents were asked to identify a femoral landmark and an ACL footprint on ten 3-dimensional (3D)–printed knee models before and after a teaching session during the fall of 2018. The 3D models were made based on actual patients with different anatomic morphologic features. ImageJ software was used to quantify the measurements, which were then analyzed through use of descriptive statistics.

Results:

Before and after the teaching session, residents attempted to identify a specific anatomic location (bifurcate and intercondylar ridge intersection) with a mean error per participant ranging from 5.00 to 10.95 mm and 4.79 to 12.13 mm in magnitude, respectively. Furthermore, before and after the teaching session, residents identified the specific position to perform the surgical procedure (ACL femoral footprint), with a mean error per participant ranging from 4.58 to 8.80 mm and 3.87 to 11.07 mm in magnitude, respectively. The teaching session resulted in no significant improvement in identification of either the intersection of the bifurcate and intercondylar ridges (P = .9343 in the proximal-distal axis and P = .8133 in the anteroposterior axis) or the center of the femoral footprint (P = .7761 in the proximal-distal axis and P = .9742 in the anteroposterior axis).

Conclusion:

Although a formal teaching session was combined with a hands-on session that entailed real surgical instrumentation and fresh cadaveric specimens, the intervention seemed to have no direct impact on senior residents’ performance or their ability to demonstrate the material taught. This puts into question the format and efficacy of present teaching methods. Also, it is possible that the 3D spatial perception required to perform these skills is not something that can be taught effectively through a teaching session or at all. Further investigation is required regarding the effectiveness and application of surgical skill laboratories and simulations on the competencies of orthopaedic residents.

Evaluating the Accuracy of Tibial Tunnel Placement After Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction

BACKGROUND

Anatomic anterior cruciate ligament (ACL) reconstruction improves knee kinematics and joint stability in symptomatic patients who have ACL deficiency. Despite a concerted effort to place the graft within the ACL's native attachment sites, the accuracy of tunnel placement using contemporary techniques is not well established.

PURPOSE

To use 3-dimensional magnetic resonance imaging (3D MRI) to prospectively evaluate the accuracy of tibial tunnel placement after anatomic ACL reconstruction.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Forty patients with symptomatic, ACL-deficient knees were prospectively enrolled in the study and underwent 3D MRI of both their injured and uninjured knees before and after surgery through use of a validated imaging protocol. The root ligament of the anterior horn of the lateral meniscus was used as a radiographic reference, and the center of the reconstructed graft was compared with that of the contralateral normal knee. The tunnel angles and intra-articular graft angles were also measured, as was the percentage overlap between the native tibial footprint and tibial tunnel.

RESULTS

The reconstructed tibial footprint was placed at a mean ± SD of 2.14 ± 2.45 mm (P < .001) medial and 5.11 ± 3.57 mm (P < .001) posterior to the native ACL footprint. The mean distance between the center of the native and reconstructed ACL at the tibial attachment site was 6.24 mm. Of the 40 patients, 18 patients had a tibial tunnel that overlapped more than 50% of the native footprint, and 10 patients had maximal (100%) overlap. Further, 22 of the 40 patients had less than 50% overlap with the native footprint, and in 12 patients the footprint was missing completely.

CONCLUSION

Despite the use of contemporary surgical techniques to perform anatomic ACL reconstruction, a significant positioning error in tibial tunnel placement remains.

Video-based computer navigation in knee arthroscopy for patient-specific ACL reconstruction

PURPOSE

The anterior cruciate ligament tear is a common medical condition that is treated using arthroscopy by pulling a tissue graft through a tunnel opened with a drill. The correct anatomical position and orientation of this tunnel are crucial for knee stability, and drilling an adequate bone tunnel is the most technically challenging part of the procedure. This paper presents the first guidance system based solely on intra-operative video for guiding the drilling of the tunnel.

METHODS

Our solution uses small, easily recognizable visual markers that are attached to the bone and tools for estimating their relative pose. A recent registration algorithm is employed for aligning a pre-operative image of the patient's anatomy with a set of contours reconstructed by touching the bone surface with an instrumented tool.

RESULTS

Experimental validation using ex-vivo data shows that the method enables the accurate registration of the pre-operative model with the bone, providing useful information for guiding the surgeon during the medical procedure. Experiments also demonstrate that the guided drilling of the tunnel leads to errors as low as 2.5 mm in the footprint and [Formula: see text] in orientation, which compares favourably to other works in the field.

CONCLUSION

The high accuracy and short time overhead evinced by the experimental validation combined with no additional incisions or capital equipment make this video-based computer-aided arthroscopy solution an appealing alternative to the existing approaches.

Anteversion and length of the femoral tunnel in ACL reconstruction: in-vivo comparison between rigid and flexible instrumentation

Background

Due to it being tangential to the distal femoral axis, the anteromedial portal presents significant risk of causing iatrogenic damage, and of producing tunnels that are too short for optimal osseointegration. Flexible reamers were developed to eliminate the need for knee hyperflexion and offer better-controlled orientation of the femoral tunnel. We aimed to compare the anteversion and length of femoral tunnels drilled using flexible reamers to those drilled using rigid reamers.

Methods

Between May 2012 and December 2013, all patients receiving ACL reconstruction performed by one surgeon were operated on using either a rigid or a flexible reamer from the same supplier (Versi-Tomic® system, Stryker, Kalamazoo, Michigan). The height of each patient was recorded, and the length and anteversion of the femoral tunnels were measured intra-operatively and on true lateral radiographs, respectively.

Results

Thirty-seven patients underwent operations using the rigid instrumentation, and 43 using the flexible instrumentation. There was no statistically significant difference between the two groups in either sex or height (p = n.s.). The patients operated on using the rigid instrumentation had tunnels anteverted by 18.6° ± 6° and 33.6 ± 2.9 mm long. Those operated on using the flexible instrumentation had tunnels anteverted by 40° ± 2° and 41.1 ± 3.57 mm long. Both anteversion and tunnel length were significantly greater for tunnels drilled using the flexible instrumentation (p < 0.001).

Conclusions

This study demonstrated that flexible reamers produce significantly more anteverted and longer femoral tunnels during ACL reconstruction than rigid reamers. Clinical studies remain necessary to assess the outcomes of ACL reconstruction using flexible reamers.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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